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  • 301.
    Pulido, Jean Alexander
    et al.
    Department of Industrial Engineering, Pontificia Universidad Javeriana, Bogotá.
    Barrero, Lope
    Department of Industrial Engineering, Pontificia Universidad Javeriana, Bogotá.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Dennerlein, Jack
    Bouvé College of Health Science, Northeastern University, Boston.
    Torres, Paola
    Javesalud, Health service provider, Bogota.
    Berna, Luis Gabriel
    Javesalud, Health service provider, Bogota.
    Low back pain affects self-reported task durations: results of an experimental study2016Conference paper (Refereed)
    Abstract [en]

    Background. Self-reported task durations are frequently used as input when assessing exposures related to musculoskeletal disorders (MSDs), in spite of being associated with errors. This work aimed to estimate the extent to which low-back pain status, true task duration, biomechanical load and pace influence errors in self-reported task durations.

    Methods. 48 workers with—and 48 workers without— low-back pain, matched by gender, age group and job type, were recruited through a health service provider. T-tests con-firmed that matching was successful. Each worker performed three standardized tasks—i.e. shelving boxes, filing journals and typing texts—in a combination of the following conditions: one of three durations (60, 80 or 100 minutes); two paces in shelving (walking at 3 km/hr vs. 6 km/hr); and two loads in shelving (box weight 1.25 vs. 2.5 kg). Partici-pants were asked about the perceived duration of each task immediately after the work session while being aware of the total duration of the session. Posture and kinematics of the back (iLMM™) and heart rate (portable Polar®) were monitored throughout sessions.

    Results. Regression analyses indicated that task type, true task duration and low-back pain status affect errors in self-reported task durations. Workers with low-back pain overestimated the shelving task more than workers without pain, by 15 to 36 minutes, depending on the true duration of the task. This occurred at the expense of a larger underestimation of the other two tasks, and mainly the typing task.

    Discussion. Since errors in self-reported task duration appear to be significantly de-pendent on the worker’s musculoskeletal pain status, as well as factors in the job, we recommend that efforts be made to correct such errors by calibration modeling, or, at a minimum, that researchers be aware of this potential effect on exposure assessments and on epidemiological research that deals with work-related MSDs.

  • 302.
    Rashid, Mamunur
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Kristofferzon, Marja-Leena
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Caring science.
    Heiden, Marina
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Nilsson, Annika
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Caring science. Department of Public Health and Caring Sciences, Faculty of Medicine, Uppsala University, Uppsala, Sweden.
    Factors related to work ability and well-being among women on sick leave due to long-term pain in the neck/shoulders and/or back: a cross-sectional study2018In: BMC Public Health, ISSN 1471-2458, E-ISSN 1471-2458, Vol. 18, no 1, article id 672Article in journal (Refereed)
    Abstract [en]

    BACKGROUND:

    Musculoskeletal pain is one of the leading causes of sick leave, especially among women, in Western countries. The aim of the present study was to identify factors associated with work ability and well-being, respectively, among women on sick leave due to long-term pain in the neck/shoulders and/or back.

    METHODS:

    A cross-sectional study with a correlational design was conducted on women who were sick-listed due to long-term pain in the neck/shoulders and/or back. A total of 208 participants responded to a survey comprising eight instruments: Multidimensional Pain Inventory scale, General Self-Efficacy scale, Sense of Coherence scale, Coping Strategies Questionnaire, Demand-Control-Support Questionnaire, Hospital Anxiety and Depression Scale, Work Ability Index and Life Satisfaction questionnaire. Multiple linear regression analyses were performed to identify factors associated with work ability and well-being, respectively.

    RESULTS:

    Women who more strongly believed they would return to the same work had greater work ability (β = 0.39, p < 0.001), whereas women with higher pain intensity (β = - 0.30, p < 0.001) and higher job strain (β = - 0.12, p < 0.05) had lower work ability. Women with higher self-efficacy rated greater well-being (β = 0.14, p < 0.05). As the women's scores for depression increased, their well-being decreased by 48%, which was statistically significant (p < 0.001). The regression models for work ability and well-being were significant (p < 0.001), and their adjusted R- square values were 48% and 59%, respectively.

    CONCLUSIONS:

    The study suggests that the factors beliefs to be back at the same work, pain intensity and job strain are predictive of work ability. Moreover, the factors self-efficacy and depression seem to be predictive of well-being. The findings highlight factors that should be considered by health care professionals and policy-makers to guide attempts to reduce sick leave.

  • 303.
    Rashid, Mamunur
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Kristofferzon, Marja-Leena
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Caring science.
    Heiden, Marina
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Nilsson, Annika
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Caring science.
    Predictors of work ability among women on long-term sick leave due to musculoskeletal pain2017In: NES2017 conference proceedings / [ed] Anna-Lisa Osvalder, Mikael Blomé and Hajnalka Bodnar, 2017, p. 140-Conference paper (Refereed)
    Abstract [en]

    Background: Musculoskeletal pain is one of the leading causes of sick leave (SL), especially among women in Sweden and in other western countries. It is, therefore, important to know which health- and work-related factors are associated with work ability (WA) among women with long-term musculoskeletal pain.

         Purpose: The aim of this study was to determine whether there is any association between self-efficacy, anxiety, depression, sense of coherence, job strain, support at work, pain intensity, physical activity, beliefs to be back at the same work, coping strategies, and WA.

         Methods: A cross-sectional study was conducted on women with long-term pain who were on SL. Inclusion criteria: (i) age 18-65 years, (ii) SL: ≥ 1 months, (iii) SL: ≥ 50%, (iv) pain in neck, shoulder or back (≥ 3 months), and (v) understanding Swedish. Exclusion criteria: (i) rheumatoid arthritis, (ii) multiple sclerosis, (iii) stroke, (iv) cancer, (v) Parkinson, (vi) bipolar disease, (vii) schizophrenia, (viii) pregnancy. In spring 2016, self-administered questionnaires were sent out to 600 women who were receiving time-loss benefits according to the Swedish Social Insurance registers. Out of these, a total of 208 participants responded and were included in the analysis. For assessing the predictors and the outcome, seven instruments were used: General Self-Efficacy, Hospital Anxiety and Depression Scale, Demand-Control-Support Questionnaire, Sense of Coherence, Multidimensional Pain Inventory, Coping Strategy Questionnaire and Work Ability Index. Two of the predictors, physical activity and beliefs to be back at the same work, were measured by single questions. Multiple linear regression analyses were performed to detect which of the factors were associated with WA.

         Results: Women who more strongly believed that they would return to the same work within 6 months had higher WA (β= 0.39, p < .001), whereas women with higher pain intensity (β= -0.28, p < .001) and higher job strain (β= -0.12, p < .05) had lower WA. The results did not change when age, cohabitant, economic situation and social support were controlled for in the analysis. The regression model was significant (p < .0001), and its adjusted R- square was 48%.

         Discussion and practical implications: Women’s positive beliefs are associated with higher WA in accordance with previous studies. Our study also found that pain intensity and high job strain are associated with reduced WA. The results suggest that health care providers and employers should take women’s beliefs to be back at the same work into account for supporting them to return to work. Furthermore, the focus of rehabilitation program should be on women suffering from high pain intensity to increase WA.

         Conclusion: This study showed that beliefs to be back at the same work, pain intensity and job strain might be predictors of WA. Further studies are needed to identify if these predictors are also important for WA among women with long-term pain who are at work.

     

    Key words: Factors, ability to work, sickness absence, women and pain

  • 304.
    Rashid, Mamunur
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Kristofferzon, Marja-Leena
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Caring science. Department of Public Health and Caring Sciences, Faculty of Medicine, Uppsala University, Sweden .
    Heiden, Marina
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Nilsson, Annika
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Caring science. Department of Public Health and Caring Sciences, Faculty of Medicine, Uppsala University, Sweden .
    Work ability, well-being and return-to-work among women in Gävleborg on sick leave due to long-term pain in the neck/shoulders and/or back2018In: FALF KONFERENS 2018 Arbetet – problem eller potential för en hållbar livsmiljö?   10-12 juni 2018 Gävle: Program och abstracts / [ed] Per Lindberg, Gävle: Gävle University Press , 2018, p. 68-Conference paper (Refereed)
    Abstract [en]

    Background

    Sickness absence due to long-term musculoskeletal pain (MSP) is a common phenom-enon in Sweden as well as in other European countries. Sick leave due to MSP (i.e. pain in the neck/shoulders and/or back) is higher among women than among men; therefore, women can be considered as a vulnerable group.

    Aim

    The overall aim is to identify factors of importance for work ability, well-being and return to work among women of working age who are on sick leave due to long-term pain in the neck/shoulders and/or back. The project includes three empirical studies.

    Methods

    The project was a result of a joint collaboration between the University of Gävle and the Swedish Social Insurance Agency in Gävleborg. Initially, a postal survey was sent to 600 women in Gävleborg who were receiving time-loss benefits during spring 2016. The inclusion criteria were: women aged 18-65 years, ≥ 50% sick leave from service, sick leave ≥ 1 month due to pain in the neck/shoulders and/or back (≥ 3 months) and understanding the Swedish language. The exclusion criteria were: rheumatoid arthritis, multiple sclerosis, stroke, cancer, Parkinson, bipolar disease, schizophrenia and preg-nancy. After 12 months, a follow-up survey was sent to the 208 women who answered the survey at baseline, and 141 responded.

    Results

    Study-I aimed to identify factors associated with work ability and well-being among women on sick leave. The results showed that beliefs to be back at the same work, pain intensity and job strain correlated with work ability. Self-efficacy and depression correlated with well-being. Study-II aimed to compare work ability and well-being over time, among women who returned to work (RTW) versus women who remained on sick leave in one year. The findings indicated that out of 141 women, 94 did RTW and 47 remained on sick leave. The group that RTW improved in work ability as well as well-being over time, whereas the group that remained on sick leave tended to decline over time in well-being. Study-III aims to identify predictors of RTW among women on sick leave. The analysis is under way. This project highlights factors that should be considered by health care professionals and policy-makers to guide attempts to reduce sick leave in this vulnerable group.

  • 305.
    Rashid, Mamunur
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Kristofferzon, Marja-Leena
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Caring science. Uppsala University, Uppsala, Sweden.
    Nilsson, Annika
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Caring science. Uppsala University, Uppsala, Sweden.
    Heiden, Marina
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Factors associated with return-to-work among people on work absence due to long-term neck or back pain: a narrative systematic review2017In: BMJ Open, ISSN 2044-6055, E-ISSN 2044-6055, Vol. 7, no 6, article id e014939Article, review/survey (Refereed)
    Abstract [en]

    OBJECTIVE:

    The purpose of this narrative systematic review was to summarise prognostic factors for return to work (RTW) among people with long-term neck/shoulder or back pain.

    METHODS:

    A systematic literature search was performed through three databases (Medline, CINAHL and PsycINFO) for studies published until February 2016. Only observational studies of people on work absence (≥2 weeks) due to neck/shoulder or back pain were included. The methodological quality of the included studies was assessed using guidelines for assessing quality in prognostic studies on the basis of Framework of Potential Biases. Factors found in the included studies were grouped into categories based on similarities and then labelled according to the aspects covered by the factors in the category.

    RESULTS:

    Nine longitudinal prospective cohort studies and one retrospective study fulfilled the inclusion criteria. From these, five categories of factors were extracted. Our findings indicate that recovery beliefs, health-related factors and work capacity are important for RTW among people with long-term neck or back pain. We did not find support for workplace factors and behaviour being predictive of RTW.

    CONCLUSIONS:

    Our findings suggest that recovery beliefs, perceived health and work capacity may be important targets of intervention for people with long-term neck or back pain. However, more high-quality prospective studies are needed to confirm the results and improve our understanding of what is needed to facilitate RTW in this population.

  • 306.
    Rasmussen, Charlotte
    et al.
    National research centre for the working Environment, Copenhagen, Denmark.
    Hallman, David
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Hellström, Fredrik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Symposia: Musculoskeletal pain as an outcome - how can we get better insight into the time course of musculoskeletal pain?2018Conference paper (Refereed)
  • 307.
    Rezagholi, Mahmoud
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Differential Socio-Economic Effects of Work Environmental Risk Faktors2016In: Journal of Health & Medical Economics, Vol. 2, no 2, article id 9Article in journal (Refereed)
    Abstract [en]

    Efficient resource allocation in the management of occupational health and safety (OHS) in the workplace requires access to information about the effects of different psychosocial and physical risk factors in the workplace on lost working hours and reduced productivity. The present article aims to help the OHS policy-makers in their decisions on allocating economic and human resources to deal with different environmental risk factors and their socio-economic consequences in the workplace. The socio-economic consequences refer substantially to missed and unproductive working hours due to sickness absences and sickness presenteeism respectively. The methodologies employed to fulfil the purpose of this study included methods to estimate marginal effects of different risk factors on lost working hours and labour productivity. The empirical results of the study showed that the psychosocial and physical dimensions of the work environment of the Swedish company Sandvik Materials Technology had different socio-economic impacts in terms of lost working hours and labour productivity. The psychosocial work environment had the greatest impacts, particularly on reducing work ability and work interest among workers and on work-related disorders among female workers. 

  • 308.
    Rezagholi, Mahmoud
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Economic Decisions on Proposed Work Environmental Studies: a Theory for Cost and Value of Information2016In: Science Journal of Public Health, ISSN 2328-7950, Vol. 4, no 1, p. 11-19Article in journal (Refereed)
    Abstract [en]

    Assessment studies of occupational exposures are retrospectively evaluated based on their achieved statistical efficiency and/or their imposed costs. However, any decision on the performance of such studies strongly requires an economic evaluation in advance. The economic evaluation of proposed work environmental studies needs, in turn, access to information on the socio-economic impacts of occupational exposures. The present article aims to help policy makers in their decisions on proposed work environmental studies by introducing a cost-value approach to the information to be produced during the studies. The cost-value approach is not exposed to subjective judgements, as in the approach of “willingness to pay”, nor to consideration of invaluable statistical efficiency as “output”, as in exposure assessment studies. The work environmental study investigated in this article contained three different groups of occupational exposures that caused sickness absences and impairments at work in a Swedish company, Sandvik Materials Technology. The results show that the suggested study would be acceptable to the policy makers in the company, as its estimated value was strictly greater than its estimated costs.

  • 309.
    Rezagholi, Mahmoud
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Bantekas, Apostolos
    University of Gävle, Faculty of Education and Business Studies, Department of Business and Economic Studies, Economics.
    Making Economic Social Decisions for Improving Occupational Health: A Predictive Cost-Benefit Analysis2015In: Occupational Medicine & Health Affairs, ISSN 1463-502X, E-ISSN 2329-6879, Vol. 3, no 6, article id 225Article in journal (Refereed)
    Abstract [en]

    The few studies attempting to estimate costs of work-related disorders suffer from poor applied methodologies. Further, as the costs are often limited to the company, decisions about investment in improving the work environment are made at the company level. However, economic decisions on changing work environments and improving occupational health need to be made at the societal level. In an economic social decision, all direct and indirect costs imposed on society by work-related disorders are considered, regardless of who pays which cost. This study introduces and demonstrates a methodology appropriate for economic decisions at the societal level for preventing work-related disorders and promoting occupational health in the workplace. The methodology uses the concept of human capital in assessing productivity loss associated with the disorders. The empirical results show that Swedish society could have gained up to 442 855 537 SEK by preventing work-related disorders at the Swedish company Sandvik Materials Technology during 2014, 87% of which would have been captured by the company.

  • 310.
    Richter, Hans
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Neck pain brought into focus2014In: Work: A journal of Prevention, Assesment and rehabilitation, ISSN 1051-9815, E-ISSN 1875-9270, Vol. 47, no 3, p. 413-418Article in journal (Refereed)
    Abstract [en]

    A time honored dictum states that the eyes "lead the body", i.e. that the body typically adjust its position to compensate for an impoverished retinal image (e. g., as due to optical blur, and/or inappropriately sized visual target). But only moderate or low level of evidence exists in support of this view. Inconclusive evidence does not, however, equal negative evidence. The accommodation/vergence system does exhibit signs of overload in contemporary working life, including eye discomfort, transient myopia, altered pattern of eye-lens oscillations, and associated phoria. Accommodation/vergence overload, caused by non-ergonomic near work, may also emerge as quickly as within one regular workday. Long-term musculoskeletal consequences of high accommodation/vergence demands have nevertheless not yet been studied in any detail. A research agenda which aims to provide multi-scientific evidence for eye-neck/shoulder interactions with public health implications and which also, in addition, study the eye-neck/shoulder mechanisms and elucidates the operating characteristics, should consequently be highly warranted. This new knowledge would be useful for physiotherapists, ergonomists and opticians, who in their profession treat patients experiencing vision-and musculoskeletal disorders. If both visual and the musculoskeletal aspects are given full and equal weight in the design and evaluation of work places, it is predicted to lead to an improved quality of life for the individual worker, and an enhanced productivity for the employer.

  • 311.
    Richter, Hans
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Crenshaw, Albert G.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Domkin, Dmitry
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Elcadi, Guilherme H.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Near infrared spectroscopy as a useful research tool to measure prefrontal cortex activity during visually demanding near work2016In: IIE Transactions on Occupational Ergonomics and Human Factors, ISSN 2157-7323, Vol. 4, no 2-3, p. 164-174Article in journal (Refereed)
    Abstract [en]

    Background: Unlike the usual skeletal muscles, ciliary muscles responsible for focusing the crystalline eye lens and extraocular muscles responsible for convergence eye movements appear resistant to fatigue. Purpose: The dual goals of this article are to briefly outline the current evidence that suggests that probing into blood flow and hemodynamic prefrontal brain activity with Near-Infrared Spectroscopy (fNIRS) could advance progress in visual ergonomic research, and to provide pilot data exemplifying the proposed approach. Methods: The vision task consisted of sustained focusing on a contrast-varying black and white Gabor grating. Four participants with a median age of 46 (IQR 44 – 50) fixated the grating from a distance of 65 cm. Three counterbalanced 10-min tasks required central fixation and accommodation/convergence on the grating target through: (i) 0.0 diopter (D) lenses, (ii) −1.5 D lenses, and (iii) −3.5yD lenses while maintaining maximal focus. Non-invasive measurements of local oxyhemoglobin (HbO2) were quantified with a one-channel Near Infrared Spectrometer, NIRS. The NIRS probe was placed on the prefrontal cortex in the vicinity of the right dorsolateral prefrontal cortex or Brodmann area 46 (DLPFC, BA 46). Accommodation response and contrast threshold was measured in parallel. Results: General estimating equation analyses showed that baseline subtracted DLPFC blood flow (ΔHbO2) increased significantly over time in all three lens conditions. The effect of time may be caused by a continuous increase in mental effort to compensate for progressively more mental fatigue induced by increased visual attention. The increase of DLPFC ΔHbO2 was also larger in magnitude in participants with larger amplitudes accommodation response (i.e., in participants who minimized deterioration in visual performance). Conclusion: The results from this study indicate that oxyhemoglobin changes recorded over DLPFC with NIRS can be used to assay the degree to which the visual system is strained during demanding near work.

  • 312.
    Richter, Hans
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Domkin, Dmitry
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Elcadi, Guilherme H.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Sports science.
    Anderson, H. W.
    Skogforsk, the forestry research institute of Sweden, Uppsala, Sweden.
    Högberg, Hans
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Caring science.
    Englund, Martin
    Skogforsk, the forestry research institute of Sweden, Uppsala, Sweden.
    A comparison of mental and visual loads resulting from semi-automated and conventional forest harvesting: An experimental machine simulation study2018Conference paper (Other academic)
    Abstract [en]

    This study is concerned with a new method for partly automating forestry harvesting work. Work-related injuries and constant demands for a higher productivity are two of the many arguments for why forestry work must be improved. Forestry work places great mental demands on the driver because they must continuously evaluate and act on relevant parts in a heavy visual information flow. Against this background the purpose of the present study was to extend the knowledge of functional linkages between visual and mental fatigue, performance, and prefrontal cortex activity, during semi-automated and conventional forestry harvesting work. Eleven healthy participants, range 21–51 years old, with a minimum of 1-year work experience, carried out the task of loading logs along a standardized path in a machine simulator during two counterbalanced 45-min periods: (i) conventional forest harvesting, and; (ii) semi-automated forest harvesting. Equal emphasizes was put on accuracy and speed. During manual forest harvesting the driver controlled the crane arm, used to load logs into the load space of the forest vehicle (“forwarder”), by manually operating the joysticks and so guide the crane to the location of the log and then back to the load space. During semi-automatic forest harvesting the driver moved the crane with the press of a button to a pre-programmed location near the log and then, after another button press, to a pre-programmed location within the load space. The following joystick usage parameters were considered for the statistical analysis: Sequential work cycle number, work phase (1-loading in basket, 2-movement to log, 3-picking up log, 4-movement to load space), number of simultaneously used controls across samples of one phase, number of direction changes of joystick movements per phase. Mental load was assessed by quantification of oxygenated hemoglobin (HbO2) concentration changes over the right dorsolateral prefrontal cortex (dlPFC) via non-invasive functional near infrared spectrometry (fFNIRS: PortaLite mini, Artinis Medical Systems, Zetten, the Netherlands). The frequency and duration of horizontal amplitudes of eye/head/neck angles was assessed continuously with 8 SmartEye cameras and used as a measure of visual load. NASA-TLX and Borg CRS was used to assess perceived mental and physical fatigue. Linear Mixed Model will be used to test and to analyze the effect of the duration of work, joystick usage, work type (manual or semi-automated) and perceived mental and physical effort on the outcome of oxygenated hemoglobin concentration. This study contributes with new knowledge of the consequences of the current increase in automation. The 4th industrial revolution can have tremendous implications on how we perceive and organize work in the future, but little is still known about the impact on human body and brain.

  • 313.
    Richter, Hans
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Domkin, Dmitry
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Elcadi, Guilherme H.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Andersson, Helena
    Skogforsk, the forestry research institute of Sweden, Uppsala, Sweden.
    Högberg, Hans
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Caring science.
    Forsman, Mikael
    Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
    Englund, Martin
    Skogforsk, the forestry research institute of Sweden, Uppsala, Sweden.
    A comparsion of mental and visual loads resulting from semi-automated and conventional forest harvesting: An experimental machine simulation study2018In: FALF Konferens 2018: Arbetet - problem eller potential för en hållbar livsmiljö?: Program och Abstracts / [ed] Per Lindberg, Gävle: Gävle Universtiy Press , 2018, p. 96-Conference paper (Other academic)
    Abstract [en]

    This study is concerned with a new method for partly automating forestry harvesting work. Work-related injuries and constant demands for a higher productivity are two of the many arguments for why forestry work must be improved. Forestry work places great mental demands on the driver because they must continuously evaluate and act on relevant parts in a heavy visual information flow. Against this background the purpose of the present study was to extend the knowledge of functional linkages between visual and mental fatigue, performance, and prefrontal cortex activity, during semi-automated and conventional forestry harvesting work. Eleven healthy participants, range 21–51 years old, with a minimum of 1-year work experience, carried out the task of loading logs along a standardized path in a machine simulator during two counterbalanced 45-min periods: (i) conventional forest harvesting, and; (ii) semi-automated forest harvesting. Equal emphasizes was put on accuracy and speed. During manual forest harvesting the driver controlled the crane arm, used to load logs into the load space of the forest vehicle (“forwarder”), by manually operating the joysticks and so guide the crane to the location of the log and then back to the load space. During semi-automatic forest harvesting the driver moved the crane with the press of a button to a pre-programmed location near the log and then, after another button press, to a pre-programmed location within the load space. The following joystick usage parameters were considered for the statistical analysis: Sequential work cycle number, work phase (1-loading in basket, 2-movement to log, 3-picking up log, 4-movement to load space), number of simultaneously used controls across samples of one phase, number of direction changes of joystick movements per phase. Mental load was assessed by quantification of oxygenated hemoglobin (HbO2) concentration changes over the right dorsolateral prefrontal cortex (dlPFC) via non-invasive functional near infrared spectrometry (fFNIRS: PortaLite mini, Artinis Medical Systems, Zetten, the Netherlands). The frequency and duration of horizontal amplitudes of eye/head/neck angles was assessed continuously with 8 SmartEye cameras and used as a measure of visual load. NASA-TLX and Borg CRS was used to assess perceived mental and physical fatigue. Linear Mixed Model will be used to test and to analyze the effect of the duration of work, joystick usage, work type (manual or semi-automated) and perceived mental and physical effort on the outcome of oxygenated hemoglobin concentration. This study contributes with new knowledge of the consequences of the current increase in automation. The 4th industrial revolution can have tremendous implications on how we perceive and organize work in the future, but little is still known about the impact on human body and brain.

  • 314.
    Richter, Hans
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Domkin, Dmitry
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Forsman, Mikael
    Division of Occupational and Environmental Medicine, Department of Public Health Sciences, Karolinska Institute.
    Ciliary muscle contraction force and trapezius muscle activity during manual tracking of visual targets2014In: The Association for Research in Vision and Ophthalmology Annual Meeting: ARVO 2014, 2014, p. 263-Conference paper (Refereed)
  • 315.
    Richter, Hans
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Forsman, Mikael
    Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
    Elcadi, Guilherme H.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences, Sports science.
    Brautaset, R.
    School of Optometry, Karolinska Institutet, Stockholm, Sweden.
    Marsh, John E.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology. School of Psychology, University of Central Lancashire, Preston, United Kingdom.
    Zetterberg, Camilla
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Section of Occupational and Environmental Medicine, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
    Prefrontal cortex activity evoked by convergence load under conflicting stimulus-to-accommodation and stimulus-to-vergence eye-movements measured by NIRS: Prefrontal cortex oxygenation and visual fatigue2018In: Frontiers in Human Neuroscience, ISSN 1662-5161, E-ISSN 1662-5161, Vol. 12, article id 298Article in journal (Refereed)
    Abstract [en]

    Purpose: To extend our knowledge of the functional linkages between visual fatigueand regional cerebral prefrontal cortex (PFC) oxygenation, we measured time related hemodynamic changes over the right dorsolateral prefrontal cortex (dlPFC) duringconvergence load under conflicting stimulus-to-accommodation and stimulus-tovergence eye movements with and without concurrent mental load.

    Methods: Twenty healthy participants with a median age of 28 years (range:18–44 years) fixated upon a vertical bar presented separately to the left andright eyes, using polarized filters, during four counterbalanced 10-min periods:(i) no accommodation/vergence conflict (Control, Ctrl); (ii) added convergenceload and accommodation/vergence conflict (Conv); (iii) added cognitive load only(Cog) and; (iv) a combination of added cognitive and convergence load andaccommodation/vergence conflict (Cc). Viewing distance was 65 cm. Non-invasivemeasurements of hemodynamic activity over the dlPFC were quantified by functionalnear-infrared spectroscopy (fNIRS). During the two-convergence load conditions, thehorizontal disparity of the two bars varied dynamically from no disparity to a disparityset 20% below the individual threshold for diplopia. Cognitive load was induced by then-back-2 test which required the subject to memorize and recall the changing colorsof the horizontal bars and decide when a given color was the same as that occurring two colors previously. fNIRS data were averaged over 10-s windows centered at 0, 2,4, 6, 8, and 10 min of each task, subtracted from a 20-s baseline window immediatelypreceding the visual task, and then represented as changes in oxygenated hemoglobin(ΔHbO2); deoxygenated hemoglobin (ΔHHb) and total hemoglobin (ΔtHb).

    Results: Linear mixed model analyses showed that hemodynamic activity wassystematically influenced by time (p < 0.001). The group-averaged time-related levelof change across the viewing conditions did not differ when compared with one another(p > 0.05). Larger convergence eye-movement responses under conflicting stimulus-to accommodation,and stimulus-to-vergence over time, increased ΔHbO2 and ΔtHb onlyin condition Cc and after 8 min of task time (p < 0.10 for min-6 and min-8: p < 0.05 for min-10).

    Discussion: Collectively, our data suggest that HbO2, HHb, and tHb, recorded over the dlPFC with fNIRS, can be used to assay the degree to which supervisory oculomotorcontrol processes are activated during visually deficient near work.

  • 316.
    Richter, Hans
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Zetterberg, Camilla
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Forsman, Mikael
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Karolinska Institut, Stockholm, Sweden .
    Temporal Dependence of Trapezius Muscle Activation during Sustained Eye-Lens Accommodation at Near2013In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 8026, no 2, p. 269-275Article in journal (Refereed)
    Abstract [en]

    In this experimental study different levels of oculomotor load were induced via optical trial lenses. The aim was to investigate the temporal dependence of a moderate visual load on trapezius muscle activity. Trapezius muscle activity was measured with bipolar surface electromyography (EMG). Sixty-six subjects with a median age of 36 (range 19–47, std 8) viewed a black and white Gabor grating (5 c/deg) through 0 D, and -3.5 D lenses, in periods of 7-min. An auto refractor was used to continuously sample data on eye-lens accommodation during the vision tasks. Response-diopters were used as a dichotomous high/low accommodation grouping variable. For these groups EMG amplitudes during minutes 1-7 per each lens trial were studied separately with Generalized Estimating Equations (GEE). The analysis results showed significant increases in trapezius muscle activity over time for both viewing conditions. For the binocular -3.5 D condition response-diopters gave a significant positive contribution to the EMG amplitude. The results indicate that sustained eye-lens accommodation at near, during ergonomically unfavorable viewing conditions, may increase the risk for trapezius muscle myalgia.

  • 317.
    Richter, Hans
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Zetterberg, Camilla
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Section of Occupational and Environmental Medicine, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
    Forsman, Mikael
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Division of Occupational and Environmental Medicine, Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden.
    Trapezius muscle activity increases during near work activity regardless of accommodation/vergence demand level2015In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 115, no 7, p. 1501-1512Article in journal (Refereed)
    Abstract [en]

    Aim

    To investigate if trapezius muscle activity increases over time during visually demanding near work.

    Methods

    The vision task consisted of sustained focusing on a contrast-varying black and white Gabor grating. Sixty-six participants with a median age of 38 (range 19–47) fixated the grating from a distance of 65 cm (1.5 D) during four counterbalanced 7-min periods: binocularly through −3.5 D lenses, and monocularly through −3.5 D, 0 D and +3.5 D. Accommodation, heart rate variability and trapezius muscle activity were recorded in parallel.

    Results

    General estimating equation analyses showed that trapezius muscle activity increased significantly over time in all four lens conditions. A concurrent effect of accommodation response on trapezius muscle activity was observed with the minus lenses irrespective of whether incongruence between accommodation and convergence was present or not.

    Conclusions

    Trapezius muscle activity increased significantly over time during the near work task. The increase in muscle activity over time may be caused by an increased need of mental effort and visual attention to maintain performance during the visual tasks to counteract mental fatigue.

  • 318. Order onlineBuy this publication >>
    Rissén, Dag
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Centrum för forskning och utveckling, Uppsala universitet/Landstinget Gävleborg.
    Psykosocial arbetsmiljö och (o)hälsa: ett biopsykosocialt stressperspektiv2014In: Hälsa, livsmiljö och arbetsliv: ur ett socialt arbete-perspektiv / [ed] Fereshteh Ahmadi & Sam Larsson, Gävle: Gävle University Press , 2014, p. 17-42Chapter in book (Other academic)
  • 319.
    Rissén, Dag
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Centre for Research & Development, Uppsala University/Region of Gävleborg, Gävle, Sweden.
    Fjellman-Wiklund, Annchristine
    Department of Community Medicine and Rehabilitation, Physiotherapy, Umeå University.
    Röijezon, Ulrik
    Department of Health Science, Luleå University of Technology.
    Prevalence, intensity, and playing related consequences of musculoskeletal pain, and associations with mood among professional orchestra musicians: a pilot study2015Conference paper (Refereed)
    Abstract [en]

    Title: Prevalence, intensity, and playing related consequences of musculoskeletal pain, and associations with mood among professional orchestra musicians – a pilot study

    Aim: The aim of this cross-sectional study was to examine the 7-day prevalence, intensity, and consequences of musculoskeletal pain in the upper part of the body among professional musicians. Additional aims were to examine subjective mood and associations between mood and pain.

    Methods: This study is part of an ongoing national survey on musculoskeletal health conditions among professional musicians in Swedish symphony and opera orchestras. The data of this report is collected from two orchestras. Seventy-eight musicians (80%) participated, aged 45 ±9.6 years and 41% women. Results: Eighty percent of the musicians reported pain during the last 7 days. Pain was most frequent in the neck (59%) and the right shoulder (36%). The intensity of pain (11-point scale) was highest in the neck (mean 2.7, SD 1.8) and in the right hand (mean 2.7, SD 1.9). Playing related consequences were particularly related to pain in the left (71%) and right (54%) hands, and pain located to the left upper extremity did relatively more often affect playing performance compared to right side pain. Mood ratings showed that the musicians to a higher degree experienced “positive mood” (stimulated, concentrated, happy) compared to “negative mood” (stressed, exhausted, tense, nervous/anxious). Significant positive correlations were found between neck pain and stressed (rho=0.501, p=.000); neck pain and exhausted (rho=0.318, p=0.033); neck pain and tense (rho=0.314, p=0.034); and neck pain and nervous/anxious (rho=0.346, p=0.019). Significant correlations were not found between mood and pain in any other body region, except for a positive correlation between right shoulder and exhausted (rho=0.384, p=0.048).

    Conclusion: These preliminary results show a high 7-day prevalence of pain among professional musicians, especially in the neck. Left upper extremity and left and right hand pain needs special clinical attention due to high impact on playing performance. The results concerning associations between perceived “negative mood” and neck pain are supported by earlier findings (1,2) but need further exploration.

  • 320.
    Ristiniemi, Heli
    et al.
    Stress Clinic, Stockholm, Sweden.
    Perski, Aleksander
    Stress Research Institute Stockholm University, Stockholm, Sweden.
    Lyskov, Eugene
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Emtner, Margareta
    Department of Medical Sciences and Neuroscience Uppsala University, Uppsala, Sweden.
    Hyperventilation and exhaustion syndrome2014In: Scandinavian Journal of Caring Sciences, ISSN 0283-9318, E-ISSN 1471-6712, Vol. 28, no 4, p. 657-664Article in journal (Refereed)
    Abstract [en]

    Chronic stress is among the most common diagnoses in Sweden, most commonly in the form of exhaustion syndrome (ICD-10 classification – F43.8). The majority of patients with this syndrome also have disturbed breathing (hyperventilation). The aim of this study was to investigate the association between hyperventilation and exhaustion syndrome. Thirty patients with exhaustion syndrome and 14 healthy subjects were evaluated with the Nijmegen Symptom Questionnaire (NQ). The participants completed questionnaires about exhaustion, mental state, sleep disturbance, pain and quality of life. The evaluation was repeated 4 weeks later, after half of the patients and healthy subjects had engaged in a therapy method called ‘Grounding’, a physical exercise inspired by African dance. The patients reported significantly higher levels of hyperventilation as compared to the healthy subjects. All patients’ average score on NQ was 26.57 ± 10.98, while that of the healthy subjects was 15.14 ± 7.89 (t = −3.48, df = 42, p < 0.001). The NQ scores correlated strongly with two measures of exhaustion (Karolinska Exhaustion Scale KES r = 0.772, p < 0.01; Shirom Melamed Burnout Measure SMBM r = 0.565, p < 0.01), mental status [Hospital Anxiety and Depression Score (HADS) depression r = 0.414, p < 0.01; HADS anxiety r = 0.627, p < 0.01], sleep disturbances (r = −0.514, p < 0.01), pain (r = −.370, p < 0.05) and poor well-being (Medical Outcomes Survey Short Form 36 questionnaire- SR Health r = −0.529, p < 0.05). In the logistic regression analysis, the variance in the scores from NQ were explained to a high degree (R2 = 0.752) by scores in KES and HADS. The brief Grounding training contributed to a near significant reduction in hyperventilation (F = 2.521, p < 0.124) and to significant reductions in exhaustion scores and scores of depression and anxiety. The conclusion is that hyperventilation is common in exhaustion syndrome patients and that it can be reduced by systematic physical therapy such as Grounding.

  • 321.
    Rolfö, L.
    et al.
    Department of Ergonomics, KTH Royal Institute of Technology, Huddinge, Sweden.
    Jahncke, Helena
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Järvholm, L. S.
    Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden.
    Öhrn, M.
    Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden.
    Babapour, M.
    Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg, Sweden.
    Predictors of Preference for the Activity-based Flexible Office2019In: Human Systems Engineering and Design: Proceedings of the 1st International Conference on Human Systems Engineering and Design (IHSED2018) / [ed] Tareq Ahram, Waldemar Karwowski, and Redha Taiar, Cham: Springer, 2019, p. 547-553Conference paper (Refereed)
    Abstract [en]

    Activity-based Flexible Offices (A-FOs) are implemented with varying degree of success. Employees relocate from cell or open-plan offices, from different organizational backgrounds, varying design and implementation processes, and have different types of work tasks. This study aims at investigating whether preference for the A-FO correlate with these preconditions. The results from Chi-square tests and Spearman’s non-parametric correlation of post-relocation questionnaires distributed to 11 A-FO sites, showed that a high preference for the A-FO correlated strongest with an A-FO preference prior to relocation, being a former open-plan office occupier and with frequent performance of innovation. Low preference for the A-FO correlated with frequent performance of concentration demanding tasks. Working with tasks with high confidentiality did not predict the preference ratings.

  • 322.
    Rolfö, Linda
    et al.
    Unit of Ergonomics, School of Technology and Health, KTH, Stockholm, Sweden.
    Eklund, Jörgen
    Unit of Ergonomics, School of Technology and Health, KTH, Stockholm, Sweden.
    Jahncke, Helena
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Perceptions of performance and satisfaction after relocation to an activity-based office2018In: Ergonomics, ISSN 0014-0139, E-ISSN 1366-5847, Vol. 61, no 5, p. 644-657Article in journal (Refereed)
    Abstract [en]

    Many companies move from open-plan offices (OPO) to activity-based workplaces (ABWs). However, few studies examine the benefits and drawbacks following such a change. The aim of this study was to explore how physical conditions, office use, communication, privacy, territoriality, satisfaction and perceived performance change following a company's relocation from an OPO to an ABW. A mixed methods approach included pre- and post-relocation questionnaires and post-relocation focus groups, individual interviews and observations. The questionnaires enabled comparisons over time (n = 34) and broader analyses based on retrospective ratings of perceived change (n = 66). Results showed that satisfaction with auditory privacy, background noise, air quality, outdoor view and aesthetics increased significantly after relocation. Negative outcomes, such as lack of communication within teams, were perceived as being due to the high people-to-workstation ratio and lack of rules. Overall satisfaction with the physical work environment increased in the ABW compared to the OPO. Perceived performance did not change significantly. Practitioner Summary: Activity-based workplaces (ABWs) are commonly implemented although their effects on performance and well-being are unclear. This case study gives advice to stakeholders involved in office planning. Despite shortcomings with the people-to-workstation ratio and rules, employees showed improved satisfaction with auditory privacy and aesthetics in the ABW compared with the previous open-plan office.

  • 323.
    Rudolfsson, Thomas
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Umeå universitet, Sjukgymnastik.
    Sensorimotor control and cervical range of motion in women with chronic neck pain: Kinematic assessments and effects of neck coordination exercise2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Introduction: Neck pain is a common problem in society and is more prevalent among women. The consequences of neck pain for the individual often include activity and participation limitations, thus affecting many dimensions of life. There is still a lack of understanding of the underlying mechanisms of the disorder and likewise of efficient rehabilitation for people with neck pain. However, coordination exercises have shown promising short-term effects. To carry this line of research forward, there is a need to improve methods for objective characterization of impairments and to investigate novel methods of rehabilitation.

    Aims: To characterize impairments of active cervical range of motion of the upper and lower cervical levels in women with chronic neck pain with a novel method (Study I and II) and identify the influence of head posture and movement strategies (Study II). Further, to investigate the effects of a novel method for neck coordination exercise on sensorimotor function and neck pain (study III) and the consistencies of motor variability metrics in a goal directed arm movement task to aid the design of future clinical research (Study IV).

    Methods: All studies were laboratory based with kinematic assessments of neck movements (Study I-III), balance (Study III) and goal directed arm movements (Study III, IV). The studies had designs that were: cross-sectional (I and II), randomized controlled trial (III) or test-retest reliability study (IV). Participants in Study I (n=135) and II (n=160) were women with chronic non-specific neck pain and healthy controls. In Study III, women with chronic non-specific neck pain (n=108) were randomized into three different individually supervised 11 week interventions. Study IV included healthy women (n=14).

    Results: It was found that cervical range of motion impairments in women with non-specific neck pain were direction- and level-specific; impairments were greater in extension in the upper and flexion in the lower levels of the cervical spine. The magnitude of impairments in range of motion was associated to self-ratings of functioning and health. Possible group differences in natural head posture were rejected as a cause for the direction specific effects. Neither could the effects be explained by a strategy to minimize torque in the cervical spine during movement execution. The neck coordination training was not superior to strength training (best-available) and massage treatment (sham) in improving sensorimotor functions or pain according to short-term and 6 months follow ups. The results from the study of the goal directed movement task showed that between and within-subject sizes of most motor variability metrics were too large to make the test suitable for application in clinical research.

    Conclusions: Women with chronic non-specific neck pain have direction- and level-specific impairments in cervical sagittal range of motion. The underlying causes of these specific impairments remains unresolved, but the direction specific impairments are not related to natural head posture. The clinical validity of the method of characterization of cervical range of motion was supported and it can be useful in future clinical research. The novel method of neck coordination exercise showed no advantages on sensorimotor functions or pain compared with best-available treatment in women with chronic non-specific neck pain.

  • 324.
    Rudolfsson, Thomas
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Department of Community Medicine and Rehabilitation, Physiotherapy, Umeå University, Umeå, Sweden.
    Björklund, Martin
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Department of Community Medicine and Rehabilitation, Physiotherapy, Umeå University, Umeå, Sweden.
    Svedmark, Åsa
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Department of Community Medicine and Rehabilitation, Physiotherapy, Umeå University, Umeå, Sweden.
    Srinivasan, Divya
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Djupsjöbacka, Mats
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Direction-specific impairments in cervical range of motion in women with chronic neck pain: influence of head posture and gravitationally induced torque2017In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 1, article id e0170274Article in journal (Refereed)
    Abstract [en]

    Background: Cervical range of motion (ROM) is commonly assessed in clinical practice and research. In a previous study we decomposed active cervical sagittal ROM into contributions from lower and upper levels of the cervical spine and found level- and direction-specific impairments in women with chronic non-specific neck pain. The present study aimed to validate these results and investigate if the specific impairments can be explained by the neutral posture (defining zero flexion/extension) or a movement strategy to avoid large gravitationally induced torques on the cervical spine.

    Methods: Kinematics of the head and thorax was assessed in sitting during maximal sagittal cervical flexion/extension (high torque condition) and maximal protraction (low torque condition) in 120 women with chronic non-specific neck pain and 40 controls. We derived the lower and upper cervical angles, and the head centre of mass (HCM), from a 3-segment kinematic model. Neutral head posture was assessed using a standardized procedure.

    Findings: Previous findings of level- and direction-specific impairments in neck pain were confirmed. Neutral head posture was equal between groups and did not explain the direction-specific impairments. The relative magnitude of group difference in HCM migration did not differ between high and low torques conditions, lending no support for our hypothesis that impairments in sagittal ROM are due to torque avoidance behaviour.

    Interpretation: The direction- and level-specific impairments in cervical sagittal ROM can be generalised to the population of women with non-specific neck pain. Further research is necessary to clarify if torque avoidance behaviour can explain the impairments.

  • 325.
    Rudolfsson, Thomas
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Umeå universitet.
    Djupsjöbacka, Mats
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Häger, Charlotte
    Umeå universitet.
    Björklund, Martin
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Umeå universitet, Alfta Research Foundation.
    Effects of neck coordination exercise on sensorimotor function in chronic neck pain: a randomized controlled trial2014In: Journal of Rehabilitation Medicine, ISSN 1650-1977, E-ISSN 1651-2081, Vol. 46, no 9, p. 908-914Article in journal (Refereed)
    Abstract [en]

    Objective: To evaluate the effect of neck coordination exercise on sensorimotor function in women with neck pain compared with best-available treatment and sham treatment. Design: Observer-blinded randomized controlled trial with short-term and 6-month follow-ups. Subjects: Women with chronic non-specific neck pain were randomized to 3 groups: neck coordinationexercise with a novel training device; strength training for the neck and shoulders; or massage. Each group had 36 participants. Methods: The intervention period was 11 weeks with 22 individually supervised sessions. Primary outcomes were postural sway measures and precision of goal-directed arm movements. Secondary outcomes were range of motion for the neck, peak speed of axial rotation, and neck pain. A repeated measures multivariate analysis of variance (MANOVA) was conducted separately on the primary outcomes for the short-term and 6-month evaluations and on the sensorimotor secondary outcomes for the 6-month effect. The 6-month effect on pain was analysed with a repeated measures analysis ofvariance (ANOVA). Results: No significant treatment effects in favour of neck coordination exercise were found for short-term or 6-month evaluations. Conclusion: Neck coordination exercise is no better than strength training and massage in improvingsensorimotor function. Further research should investigate the use of cutoffs for sensorimotordysfunctions prior to proprioceptive or coordinative training.

  • 326.
    Röijezon, Ulrik
    et al.
    Department of Health Science, Luleå University of Technology.
    Ardel, Dag
    Department of Community Medicine & Rehabilitation, Physiotherapy, Umeå University.
    Rissén, Dag
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Centre for Research & Development, Uppsala University/Region of Gävleborg, Gävle, Sweden.
    Juul-Kristensen, Birgit
    Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark.
    Generalised Joint Hypermobility and musculoskeletal pain among professional classical orchestra musicians in Sweden: a pilot study2015Conference paper (Refereed)
    Abstract [en]

    Aims: The aims were to 1) investigate the presence of Generalised Joint Hypermobility (GJH) and musculoskeletal pain among musicians in professional Swedish symphony and opera orchestras, and 2) investigate associations between GJH and musculoskeletal pain.

    Methods: A Swedish version of the 5-part questionnaire [1] and the standardised Nordic questionnaire for musculoskeletal pain disorders [2] were included in an ongoing national survey on musculoskeletal health conditions among professional orchestra musicians in Sweden. The data of this report is collected from two orchestras. Seventy-eight musicians (80%) participated, aged 45 ±9.6 years with 41% women.

    Results: At present, 77 participants completed the 5-part questionnaire, of which 19.5% (28% of the women and 13% of the men) scored two or more on the 5-part questionnaire, which is the criteria for GJH. Pain prevalence during the last 12 months was highest for the neck (73.7%) and lowest for the left and right elbows (15.6% and 16.9%, respectively) (Table 1). Binary logistic regressions revealed that hypermobility was associated with increased risk for pain conditions at the neck (Odds Ratio 5.64, p=0.005) and the left and the right hand (Odds Ratio 1.80, p=0.019 and Odds Ratio 1.68, p=0.032, respectively) (Table 1).

    Discussion/Conclusion: Previous studies have reported various results regarding hypermobility and association with musculoskeletal pain conditions, including both increased and reduced risk [3- 5]. Our study shows increased risk of pain located to the neck and both hands among musicians with GJH, while no significant increased or decreased risks were seen for the other body parts. However, larger groups of musicians should confirm the influence of GJH on musculoskeletal pain, and whether it differs between men and women and between groups of instruments. The current preliminary results may indicate that GHJ among musicians should be identified and preventive strategies be recommended, e.g., regarding pauses, posture and physical exercises.

  • 327.
    Samani, Afshin
    et al.
    Center for Sensory-Motor Interaction (SMI), Dept. of Health Science and Technology, Aalborg University.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Madeleine, Pascal
    Center for Sensory-Motor Interaction (SMI), Dept. of Health Science and Technology, Aalborg University.
    Cluster-based EVA: an alternative approach for quantification of exposure variation2013In: Eighth International Conference on Prevention of Work-related Musculoskeletal Disorders; Abstracts, 2013, p. 219-Conference paper (Refereed)
  • 328.
    Samani, Afshin
    et al.
    Center for Sensory Motor Interaction, Department of Health Science and Technology, Aalborg University.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Madeleine, Pascal
    Center for Sensory Motor Interaction, Department of Health Science and Technology, Aalborg University.
    Cluster-based exposure variation analysis2013In: BMC Medical Research Methodology, ISSN 1471-2288, E-ISSN 1471-2288, Vol. 13, p. 54-54Article in journal (Refereed)
    Abstract [en]

    Background: Static posture, repetitive movements and lack of physical variation are known risk factors for work-related musculoskeletal disorders, and thus needs to be properly assessed in occupational studies. The aims of this study were (i) to investigate the effectiveness of a conventional exposure variation analysis (EVA) in discriminating exposure time lines and (ii) to compare it with a new cluster-based method for analysis of exposure variation.

    Methods: For this purpose, we simulated a repeated cyclic exposure varying within each cycle between “low” and “high” exposure levels in a “near” or “far” range, and with  “low” or “high” velocities (exposure change rates). The duration of each cycle was also manipulated by selecting a “small” or “large” standard deviation of the cycle time. Theses parameters reflected three dimensions of exposure variation, i.e. range, frequency and temporal similarity. Each simulation trace included two realizations of 100 concatenated cycles with either low (r=0.1), medium (r=0.5) or high (r=0.9) correlation between the realizations. These traces were analyzed by conventional EVA, and a novel cluster-based EVA (C-EVA). Principal component analysis (PCA) was applied on the marginal distributions of 1) the EVA of each of the realizations (univariate approach), 2) a combination of the EVA of both realizations (multivariate approach) and 3) C-EVA. The least number of principal components describing more than 90% of variability in each case was selected and the projection of marginal distributions along the selected principal component was calculated. A linear classifier was then applied to these projections to discriminate between the simulated exposure patterns, and the accuracy of classified realizations was determined.

    Results: C-EVA classified exposures more correctly than uni 1 variate and multivariate EVA approaches; classification accuracy was 49%, 47% and 52% for EVA (univariate and multivariate), and C-EVA, respectively (p<0.001). All three methods performed poorly in discriminating exposure patterns differing with respect to the variability in cycle time duration.

    Conclusion: While C-EVA had a higher accuracy than conventional EVA, both failed to detect differences in temporal similarity. The data-driven optimality of data reduction and the capability of handling multiple exposure time lines in a single analysis are the advantages of the C-EVA.

  • 329.
    Samani, Afshin
    et al.
    Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Denmark.
    Srinivasan, Divya
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Madeleine, Pascal
    Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Denmark.
    Nonlinear metrics assessing motor variability in a standardized pipetting task: Between- and within-subject variance components2015In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 25, no 3, p. 557-564Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to estimate the between days test-retest reliability of nonlinear metrics used to quantify motor variability in a repetitive precision task. On three separate days, 14 healthy subjects performed pipetting as a general model of repetitive precision tasks. The task consisted of transferring liquid 20 times with a cycle time of 2.8 s from a pickup tube to eight target tubes placed on a table in front of the subjects. The motion of hand, arm and the pipet tip was tracked in 3D and the shoulder elevation and elbow flexion angle were obtained. Motor variability was assessed using nonlinear metrics based on information theory and recurrence quantification analysis. Between- and within- (between-days) subject variance components were computed using a one-way random effect model, and intra-class correlation coefficients (ICC) were calculated from the variance components as standardized measures of reliability. Most of the metrics displayed a considerable between-days variance component and therefore the ICC showed a slight to moderate reliability. The reported data on between- and within-subject variability can be used to design future studies using non-linear motor variability metrics on kinematics data.

  • 330.
    Samani, Afshin
    et al.
    Department of Health Science and Technology, Aalborg University.
    Srinivasan, Divya
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Madeleine, Pascal
    Department of Health Science and Technology, Aalborg University.
    Variability in patterns of muscular activity during a fatiguing repetitive task2016Conference paper (Refereed)
    Abstract [en]

    Background. Muscle fatigue develops at markedly different rates among individuals. The pattern of variation in muscle activity has been suggested as a determinant of the rate of fatigue development. This variation can occur between muscles or between compart-ments of a muscle. Thus, we investigated the pattern of muscular activity in shoulder and arm regions during a fatiguing repetitive work task.

    Methods. 21 healthy young women performed a repetitive pipetting task at 2.8 seconds/cycle. The session continued until the subject rate of perceived exertion reached 8 on Borg CR-10 scale. High density (HD) surface electromyogram (EMG) over upper trapezius, and bipolar EMG from extensor carpi radialis, flexor carpi radialis, biceps, triceps, deltoi-deus anterior, serratus anterior, upper and lower trapezius were collected to investigate intra- and inter-muscle variation patterns. EMG amplitude and mean power frequency (MPF) were obtained for all the recorded EMG signals. The barycenter of activity over the HD-EMG grid was also determined. Normalized mutual information (NMI) was determined for each pair of muscles. The extent of variability of the outcomes was also assessed.

    Results. As fatigue developed, EMG amplitude increased and the MPF decreased for all muscles except the MPF for upper trapezius and deltoideus. The activity of trapezius was higher on the lateral side of HD-EMG grid than on the medial side and the barycenter showed a lateral shift across time. NMI between the muscle pairs also increased with fatigue. The variability of the investigated outcomes was not associated with the time to the task ending.

    Discussion. Myo-electrical manifestations of muscle fatigue were observed but none of the outcomes had an association with the rate of fatigue development. Using multivariate approaches, synergistic pattern of muscular activity is yet to be investigated.

  • 331.
    Samani, Afshin
    et al.
    Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
    Srinivasan, Divya
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Madeleine, Pascal
    Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
    Variability in spatio-temporal pattern of trapezius activity and coordination of hand-arm muscles during a sustained repetitive dynamic task2017In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 235, no 2, p. 389-400Article in journal (Refereed)
    Abstract [en]

    The spatio-temporal distribution of muscle activity has been suggested to be a determinant of fatigue development. Pursuing this hypothesis, we investigated the pattern of muscular activity in the shoulder and arm during a repetitive dynamic task performed until participants' rating of perceived exertion reached 8 on Borg's CR-10 scale. We collected high density surface electromyogram (HD-EMG) over the upper trapezius, as well as bipolar EMG from biceps brachii, triceps brachii, deltoideus anterior, serratus anterior, upper and lower trapezius from 21 healthy women. Root mean square (RMS) and mean power frequency (MNF) were calculated for all EMG signals. The barycenter of RMS values over the HD-EMG grid was also determined, as well as normalized mutual information (NMI) for each pair of muscles. Cycle-to-cycle variability of these metrics was also assessed. With time, EMG RMS increased for most of the muscles, and MNF decreased. Trapezius activity became higher on the lateral side than on the medial side of the HD-EMG grid and the barycenter moved in a lateral direction. NMI between muscle pairs increased with time while its variability decreased. The variability of the metrics during the initial 10% of task performance was not associated with the time to task termination. Our results suggest that the considerable variability in force and posture contained in the dynamic task per se masks any possible effects of differences between subjects in initial motor variability on the rate of fatigue development.

  • 332.
    Sandfeld, Jesper
    et al.
    Institute of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen.
    Larsen, Lisbeth Højkjær
    Institute of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen.
    Crenshaw, Albert
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Jensen, Bente Rona
    Institute of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen.
    Muscle oxygenation, EMG, and cardiovascular responses for cabin attendants vs. controls2013In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 84, no 5, p. 478-485Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION: The goal was to investigate the effect of acute moderate hypobaric exposure on the physiological responses to sustained contractions (local) and light to moderate dynamic exercise (systemic) for cabin attendants (CAB) and a matched control group (CON).

    METHOD: There were 14 CAB and 13 CON who participated. The experimental protocol was designed as a 2 x 2 randomized crossover study for which subjects performed a forearm isometric test and a cycling test in normobaric (NORM) and hypobaric [HYPO; 574 mmHg approximately 8000 ft (2440 m) above sea level (ASL)] conditions. Oxygen saturation (StO2%) was measured in the extensor carpi radialis muscle at rest and during an isometric wrist extension (20% MVC). Heart rate (HR), ventilation (V(E)), and oxygen uptake (VO2) were measured at rest, during cycling exercise at intensities of 50 W and 100 W, and during recovery. Blood samples were collected and analyzed for hemoglobin concentrations.

    RESULTS: Local response: There was a significant effect of HYPO for both CAB and CON with a decrease in StO2% of 6.5% both at rest and during contraction. Systemic response: there was no general effect of HYPO on HR, VE, or VO2. No differences were found between groups in either the local or systemic response or in the blood parameters.

    CONCLUSION: This study shows an effect of moderate hypobaric exposure on local muscle oxygenation during rest and sustained contraction. Whether this has an impact on fatigue development during work among cabin attendants is discussed.

  • 333.
    Sandlund, Jonas
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Department of Community Medicine and Rehabilitation, Physiotherapy, Umeå University, Umeå, Sweden.
    Srinivasan, Divya
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Heiden, Marina
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Differences in motor variability among individuals performing a standardized short-cycle manual task2017In: Human Movement Science, ISSN 0167-9457, E-ISSN 1872-7646, Vol. 51, p. 17-26Article in journal (Refereed)
    Abstract [en]

    Motor variability (MV) has been suggested to be a determinant of the risk for developing musculoskeletal disorders in repetitive work. In this study we examined whether individuals consistently differed in the extent of motor variability when performing a standardized short-cycle manual task. On three separate days, arm kinematics was recorded in 14 healthy subjects performing a pipetting task, transferring liquid from a pick-up tube to eight target tubes with a cycle time of 2.8 s. Cycle-to-cycle standard deviations (SD) of a large selection of shoulder and elbow kinematic variables, were processed using principal component analysis (PCA). Thereafter, between-subjects and between-days (within-subject) variance components were calculated using a random effects model for each of four extracted principal components. The results showed that MV differed consistently between subjects (95% confidence intervals of the between-subjects variances did not include zero) and that subjects differed consistently in MV between days. Thus, our results support the notion that MV may be a consistent personal trait, even though further research is needed to verify whether individuals rank consistently in MV even across tasks. If so, MV may be a candidate determinant of the risk of developing fatigue and musculoskeletal disorders in repetitive occupational work.

  • 334.
    Sandlund, Jonas
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Department for Community Medicine and Rehabilitation, Umeå University.
    Srinivasan, Divya
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Consistency of individual motor variability patterns in repetitive precision work2015In: Physiotherapy, ISSN 0031-9406, E-ISSN 1873-1465, Vol. 101, no Suppl. 1, p. e1334-e1335Article in journal (Other academic)
    Abstract [en]

    Background:

    A longstanding hypothesis in physical therapy and occupational research is that workers repeating a task very stereotypically will be more prone to develop musculoskeletal disorders than workers that manage to vary postures and loads. Increased movement variability (MV), presumably, modify tissue loads, distribute stresses more equally, and thus reduce the cumulative load on any particular tissue. A handful of studies of MV have indicated less overuse injuries and faster recovery from musculoskeletal pain disorders. Even when repeating strictly controlled tasks individuals may differ in motor consistency, some showing higher levels of MV than others. However, whether the extent of MV is indeed a consistent individual trait across different tasks and different days is not known.

    Purpose:

    To investigate whether individual profiles of MV is stabile between days, the consistency of MV patterns from kinematic recordings, repeated across three days, was studied when performing repetitive upper-extremity precision work.

    Methods:

    A laboratory-based simulation of precision work; a 'pipetting' task paradigm, was developed in which liquid was repeatedly transferred from one tube to another, with a cycle time of 2.8s. Fourteen healthy female subjects, aged 20-45 years, right-handed and with experience in pipetting participated on 3 different days under identical conditions. Kinematic data were obtained using an electromagnetic motion capture system (FASTRAK). MV in shoulder elevation, elbow flexion and shoulder-elbow coordination were operationalized using cycle-to-cycle standard deviations across 20 pipetting cycles of kinematics parameters including joint range of motion, average and peak velocities, time to peak velocities, average angle and phase. Multivariate analysis was conducted using principal component analysis (PCA) (SIMCA+P, 12.0) to analyze relationships among variables and individual patterns in the data matrix of the recordings from day1. Thereafter, in order to confirm the observed structure of inter-individual MV patterns, classification of the data from day2 and day3 was performed using the parameters of the model from day1.

    Results:

    Four PCA components (Eigenvalues>1) accounted for 80 percent of the total variance in the model for day1. In the subsequent prediction model where data from day2 and 3 were projected into the model of day1, all subject observations except one could be predicted with 95% confidence (Hotelling T2). And individual data scores from all three days were clustered in relative proximity to each other, indicating consistency in MV between days.

    Conclusion(s):

    The findings indicate, even in this small and homogenous sample of young healthy females, that there may indeed be consistent individual traits in motor variability. A next step would be to answer whether these traits remain consistent if work factors such as work pace or precision are altered, and whether individual profiles of MV are associated with physiological responses related to risk for developing musculoskeletal disorders.

    Implications:

    Consistency of individual MV patterns substantiate previous notions that some people appear prone to repeat themselves while others tend to vary their motor behavior when performing the same task. Assessment of MV by physical therapists in research and practice could be valuable to further explore and address the relation of MV and musculoskeletal health.

  • 335.
    Sato, Tatiana
    et al.
    Physical Therapy Department, Federal University of São Carlos (UFSCar), Brazil.
    Hallman, David
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Kristiansen, Jesper
    National Research Centre for the Working Environment, Copenhagen, Denmark.
    Skotte, Jørgen
    National Research Centre for the Working Environment, Copenhagen, Denmark.
    Holtermann, Andreas
    National Research Centre for the Working Environment, Copenhagen, Denmark.
    Different autonomic responses to occupational and leisure time physical activities among blue-collar workers2018In: International Archives of Occupational and Environmental Health, ISSN 0340-0131, E-ISSN 1432-1246, Vol. 91, no 3, p. 293-304Article in journal (Refereed)
    Abstract [en]

    PURPOSE:

    The differential effect of occupational and leisure time physical activity on cardiovascular health is termed the physical activity health paradox. Cardiac autonomic modulation could bring insights about the underlying mechanism behind this differential effect. The aim was to compare heart rate variability (HRV) during different activities (sitting, standing and moving) at work and leisure among blue-collar workers.

    METHODS:

    One hundred thirty-eight workers from the NOMAD cohort were included. Data from physical activity and HRV were obtained for 3-4 days using tri-axial accelerometers (Actigraph GT3X+) and a heart rate monitor (Actiheart). HRV indices were determined during sitting, standing and moving both at work and leisure. Linear mixed-models with two fixed factors (activities and domains) were applied to investigate differences in HRV indices adjusting for individual and occupational factors.

    RESULTS:

    The results showed significant effects of domain (p < 0.01), physical activity type (p < 0.01) and interaction between domain and activity type (p < 0.01) on HRV indices. Mean heart rate (IBI) and parasympathetic measures of HRV (RMSSD and HF) were lower for sitting (p < 0.01) and higher for moving (p < 0.01) during work compared with leisure, while no difference between domains was found for standing (p > 0.05). Sympathovagal balance (LF/HF) was higher during work for sitting and moving (p < 0.01), but showed no difference for standing (p = 0.62).

    CONCLUSIONS:

    Differences in cardiac autonomic modulation between work and leisure were found, indicating sympathetic predominance during work and parasympathetic predominance during leisure for sitting. Autonomic responses can be part of the mechanism that explains the differential effect of occupational and leisure time physical activity on health.

  • 336.
    Sato, Tatiana
    et al.
    Physical Therapy Department, Federal University of São Carlos, São Paulo, Brazil.
    Hallman, David
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Kristiansen, Jesper
    National Research Centre for the Working Environment, Copenhagen, Denmark.
    Skotte, Jørgen
    National Research Centre for the Working Environment, Copenhagen, Denmark.
    Holtermann, Andreas
    National Research Centre for the Working Environment, Copenhagen, Denmark.
    Different autonomic responses to occupational and leisure time physical activity among blue-collar workers2016Conference paper (Refereed)
    Abstract [en]

    Introduction: There is a well-established relationship between high physical activity at leisure time and decreased mortality risk. On the other hand, high physical demands at work seem to increase this risk. However, the underlying mechanism behind this effect remains unknown. Heart rate variability (HRV) measurements may bring some insight into the mechanism. Thus, the aim of this study was to determine whether HRV differs between work and leisure time among blue-collar workers.

    Methods: This study was based on data from the cross-sectional NOMAD study among blue-collar workers from seven workplaces in Denmark. One hundred thirty-eight blue-collar workers, which had at least 7 recording hours during work and leisure time were included in the analysis. Data from physical activity and HRV were obtained for four days using tri-axial accelerometers (Actigraph GT3X+) and heart rate monitor (Actiheart), respectively. Parametric (paired t test) and nonparametric (Wilcoxon signed-ranks test) tests for pairwise comparisons were applied to compare mean HRV indices in time and frequency domains between work and leisure time.

    Results: The mean age of the workers was 45.2 years, 51% were females, 42% were smokers, 18% reported lifetime occurrence of hypertension and 45% reported to perform lifting and carrying for more than half of the work time. A significant higher overall HRV was found during leisure time compared to work. Leisure time showed higher parasympathetic nervous system (PNS) measures of HRV (p<.05), while sympathetic nervous system (SNS) related indices (p<.05) were reduced in comparison to work.

    Conclusions: Leisure time showed high HRV and PNS indices and work time showed high SNS-related indices. The higher SNS modulation during work can be related to a greater risk of developing heart diseases among blue-collar workers.

  • 337.
    Slijper, Harm
    et al.
    Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Over, E.
    Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands.
    Richter, Janneke
    Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands.
    Frens, Maarten
    Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands.
    Measuring computer use behavior: patterns of variability, within and across days and between different users2008In: Proceedings of Measuring Behavior 2008; 6th International Conference on Methods and Techniques in Behavioral Research / [ed] A.J. Spink, M.R. Ballintijn, N.D. Bogers, F. Grieco, L.W.S. Loijens, L.P.J.J. Noldus, G. Smit, and P.H. Zimmerman, Wageningen: Noldus , 2008, p. 111-112Conference paper (Refereed)
  • 338.
    Srinivasan, Divya
    et al.
    Department of Industrial and Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, USA.
    Barbieri, Dechristian
    Department of Physical Therapy, Federal University of São Carlos, São Paulo, Brazil.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Oliveira, Ana Beatriz
    Department of Physical Therapy, Federal University of São Carlos, São Paulo, Brazil.
    Sit-stand desks with reminder prompts and semi-automated position changes2017Conference paper (Refereed)
  • 339.
    Srinivasan, Divya
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Cantu, Hiram
    Department of Kinesiology and Physical Education, McGill University.
    Cote, Julie
    Department of Kinesiology and Physical Education, McGill University.
    Fatigue-induced increase in movement variability does not come at a cost of worse performance in a repetitive pointing task2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203Article in journal (Refereed)
    Abstract [en]

    Neuromuscular strategies employed in multijoint movements during repetitive motion-induced fatigue are still unclear, and movement variability may present a novel way to understand the compensatory control mechanisms that occur during fatigue. The aim of this study was to assess changes in shoulder and elbow joint kinematic variabilities and shoulder-elbow coordination variability associated with neck-shoulder fatigue, and whether these changes affected the spatio-temporal aspects of task performance. Nineteen healthy young adults continuously performed a repetitive pointing task between two targets placed in front of them at shoulder height at 1 Hz until fatigue (Borg CR10 rating of 8). Shoulder and elbow kinematics were recorded and used to compute shoulder abduction-adduction and elbow flexion-extension joint angles, and fingertip trajectories were used to compute the movement time and 3D spatial coordinates of the endpoint in each repetitive pointing movement cycle. Cycle-to-cycle movement variability of the shoulder and elbow joint angles from 15 consecutive forward pointing movements and cycle-to-cycle variability of continuous relative phase between the shoulder and elbow joint angles were compared between the first (baseline) and last (fatigue-terminal) minutes of performance. Shoulder kinematic variability and shoulder-elbow coordination variability were found to significantly increase with fatigue (by 60% and 30% of their respective baseline values). However, movement timing errors and spatial variability of the endpoint were found to be unchanged with fatigue. Results suggest that fatigue-related increase in shoulder variability may have been compensated by changes in shoulder-elbow coordination with an overall task performance objective and associated hierarchical control mechanisms.

  • 340.
    Srinivasan, Divya
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Martin, Bernard
    University of Michigan, Ann Arbor, USA.
    Reed, Matthew
    University of Michigan, Ann Arbor, USA.
    Effects of task characteristics on unimanual and bimanual movement times2013In: Ergonomics, ISSN 0014-0139, E-ISSN 1366-5847, Vol. 56, no 4, p. 612-622Article in journal (Refereed)
    Abstract [en]

    Fitts’ law cannot be used to predict movement times (MTs) of bimanual tasks since no empirical relationships associating task difficulty and bimanual MT have been demonstrated yet. Development of a ‘bimanual task difficulty index’ has been challenged by the complex patterns of coordination involved in simultaneously performing two tasks, one with each hand, under a control system with limited visual and attentional resources. To address this fundamental issue in human motor performance, bimanual object transfers with the left and right hands to targets of various precision requirements and separated by different distances were studied in six healthy subjects. Visual resource allocation during task performance was used to identify ‘primary’ and ‘secondary’ hand movements in bimanual tasks. While the primary movement was similar to a unimanual movement, the secondary MT varied with its own, as well as the contralateral hand’s task constraints. These results, which were stable and consistent across six subjects, provide preliminary evidence that visual behaviour, indicating closed-loop control, can be used to systematically derive bimanual MTs.

  • 341.
    Srinivasan, Divya
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    The consistency across days of motor variability in repetitive pipetting2013In: Eighth International Conference on Prevention of Work-related Musculoskeletal Disorders; Abstracts, 2013, p. 56-57Conference paper (Refereed)
  • 342.
    Srinivasan, Divya
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    The effect of combining physical and cognitive loads on motor variability in a standardised repetitive precision task2015In: Proceedings of the 19th Triennial Congress of the International Ergonomics Association, Melbourne 9-14 August, 2015 / [ed] Gitte Lindgaard & Dave Moore, 2015Conference paper (Refereed)
  • 343.
    Srinivasan, Divya
    et al.
    Grado Department of Industrial and Systems Engineering, Virginia Polytechnic Institute and State University.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Barbieri, Dechristian
    Department of Physical Therapy, Federal University of São Carlos.
    Oliveira, Ana Beatriz
    Department of Physical Therapy, Federal University of São Carlos.
    Do sit-stand workstations increase variation in upper arm postures while performing computer-intensive office work?2017Conference paper (Refereed)
  • 344.
    Srinivasan, Divya
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Hallman, David M.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Samani, Afshin
    SMI, Department of Health Science and Technology, Aalborg University, Denmark.
    Madeleine, Pascal
    SMI, Department of Health Science and Technology, Aalborg University, Denmark.
    Lyskov, Eugene
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Effects of concurrent physical and cognitive demands on muscle activity and heart rate variability in a repetitive upper-extremity precision task2016In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 116, no 1, p. 227-239Article in journal (Refereed)
    Abstract [en]

    Purpose Most previous studies of concurrent physical and cognitive demands have addressed tasks of limited relevance to occupational work, and with dissociated physical and cognitive task components. This study investigated effects on muscle activity and heart rate variability of executing a repetitive occupational task with an added cognitive demand integral to correct task performance.

    Methods Thirty-five healthy females performed 7.5 min of standardized repetitive pipetting work in a baseline condition and a concurrent cognitive condition involving a complex instruction for correct performance. Average levels and variabilities of electromyographic activities in the upper trapezius and extensor carpi radialis (ECR) muscles were compared between these two conditions. Heart rate and heart rate variability were also assessed to measure autonomic nervous system activation. Subjects also rated perceived fatigue in the neck–shoulder region, as well as exertion.

    Results Concurrent cognitive demands increased trapezius muscle activity from 8.2 % of maximum voluntary exertion (MVE) in baseline to 9.0 % MVE (p = 0.0005), but did not significantly affect ECR muscle activity, heart rate, heart rate variability, perceived fatigue or exertion.

    Conclusion Trapezius muscle activity increased by about 10 %, without any accompanying cardiovascular response to indicate increased sympathetic activation. We suggest this slight increase in trapezius muscle activity to be due to changed muscle activation patterns within or among shoulder muscles. The results suggest that it may be possible to introduce modest cognitive demands necessary for correct performance in repetitive precision work without any major physiological effects, at least in the short term.

  • 345.
    Srinivasan, Divya
    et al.
    Grado Department of Industrial and Systems Engineering, Virginia Polytechnic Institute and State University.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Huysmans, Maaike
    Department of Public & Occupational Health; EMGO Institute for Health & Care Research, VU University Medical Center, Amsterdam.
    Between-subjects and between-days variance in occupational sitting time among seasoned users of sit-stand workstations2017Conference paper (Refereed)
  • 346.
    Srinivasan, Divya
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Samani, Afshin
    Department of Health Science and Technology, Aalborg University.
    Madeleine, Pascal
    Department of Health Science and Technology, Aalborg University.
    Effects of concurrent physical and cognitive demands on arm movement kinematics in a repetitive upper-extremity precision task2015In: Human Movement Science, ISSN 0167-9457, E-ISSN 1872-7646, Vol. 42, p. 89-99Article in journal (Refereed)
    Abstract [en]

    The effect of concurrent physical and cognitive demands on arm motor control is poorly understood. This exploratory study compared movement kinematics in a repetitive high-precision pipetting task with and without additional concurrent cognitive demands in the form of instructions necessary to locate the correct target tube. Thirty-five healthy female subjects performed a standardized pipetting task, transferring liquid repeatedly from one pick-up tube to different target tubes. In the reference condition, lights indicated the target tube in each movement cycle, while the target tube had to be deciphered from a row and column number on a computer screen in the condition with additional cognitive demands. Kinematics of the dominant arm was assessed using the central tendency and variability of the pipette-tip end-point trajectory and joint kinematics properties of the shoulder and elbow. Movements slowed down (lower velocities and higher area under the movement curves) and end point trajectory variability increased in the condition with additional cognitive demands, but there were no changes in the kinematics properties such as joint range of motion, times of acceleration and deceleration (as indicated by the time to peak velocity), average angles, or phase relationships between angle and angular velocity of shoulder or elbow movements between the two conditions. Further, there were also no differences in the size or structure of variability of the shoulder and elbow joint angles, suggesting that subjects could maintain the motor repertoire unaltered in the presence of these specific additional cognitive demands. Further studies should address motor control at other levels of concurrent cognitive demands, and with motor tasks that are less automated than the pipetting task used in the present study, so as to gain an increased understanding of the effect of concurrent cognitive demands for other activities of relevance to daily life.

  • 347.
    Srinivasan, Divya
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Samani, Afshin
    Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Denmark.
    Madeleine, Pascal
    Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Denmark.
    The combined influence of task accuracy and pace on motor variability in a standardised repetitive precision task2015In: Ergonomics, ISSN 0014-0139, E-ISSN 1366-5847, Vol. 58, no 8, p. 1388-1397Article in journal (Refereed)
    Abstract [en]

    Thirty-five healthy women, experienced in pipetting, each performed four pipetting sessions at different pace and accuracy levels relevant to occupational tasks. The size and structure of motor variability of shoulder and elbow joint angles were quantified using cycle-to-cycle standard deviations of several kinematics properties, and indices based on sample entropy and recurrence quantification analysis. Decreasing accuracy demands increased both the size and structure of motor variability. However, when simultaneously lowering the accuracy demand and increasing pace, motor variability decreased to values comparable to those found when pace alone was increased without changing accuracy. Thus, motor variability showed some speed-accuracy trade-off, but the pace effect dominated the accuracy effect. Hence, this trade-off was different from that described for end-point performance by Fitts’ law. The combined effect of accuracy and pace and the resultant decrease in motor variability are important to consider when designing sustainable work systems comprising repetitive precision tasks.

  • 348.
    Srinivasan, Divya
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Rudolfsson, Thomas
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Department of Community Medicine and Rehabilitation, Umeå University, Umeå, Sweden.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Between- and within-subject variance of motor variability metrics in females performing repetitive upper-extremity precision work2015In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 25, no 1, p. 121-129Article in journal (Refereed)
    Abstract [en]

    Kinematic motor variability is extensively studied in occupational, clinical and sports biomechanics, but the consistency of most motor variability metrics have never been reported. In this study, fourteen subjects performed a repetitive pipetting task on three separate days. Movements of hand, arm and pipette tip were recorded in 3D and used to compute shoulder elevation, elbow flexion and shoulder-arm coordination angles, as well as pipette-tip endpoint precision. Cycle-to-cycle motor variability was quantified using linear dispersion measures of standard kinematics properties such as peak velocity, range of motion, and inter-segmental relative phase. Between- and within-subject consistencies of these variability metrics were quantified by variance components estimated using a nested random effects model. For most metrics, the variance between subjects was larger than that between days and cycles. Entering the variance components in statistical power equations showed that for most metrics, a total of 80-100 subjects will be required to detect a 20% difference between two groups with sufficient power, while this difference can typically be detected  in repeated-measures (paired) designs using 25 subjects. The reported between- and within-subject variance components can be used as a data base to facilitate efficient designs of future studies of kinematic motor variability.

  • 349.
    Srinivasan, Divya
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Samani, Afshin
    Center for Sensorimotor Interaction, Department of Health Science and Technology, Aalborg University.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Madeleine, Pascal
    Center for Sensorimotor Interaction, Department of Health Science and Technology, Aalborg University.
    The size and structure of arm movement variability decreased with work pace in a standardised repetitive precision task2015In: Ergonomics, ISSN 0014-0139, E-ISSN 1366-5847, Vol. 58, no 1, p. 128-139Article in journal (Refereed)
    Abstract [en]

    Increased movement variability has been suggested to reduce the risk of developing musculoskeletal disorders caused by repetitive work. This study investigated the effects of work pace on arm movement variability in a standardized repetitive pipetting task performed by 35 healthy women. During pipetting at slow and fast paces differing by 15%, movements of arm, hand and pipette were tracked in 3D, and used to derive shoulder and elbow joint angles. The size of cycle-to-cycle motor variability was quantified using standard deviations of several kinematics properties, while the structure of variability was quantified using indices of sample entropy and recurrence quantification analysis. When pace increased, both the size and structure of motor variability in the shoulder and elbow decreased. These results suggest that motor variability drops when repetitive movements are performed at increased paces, which may in the long run lead to undesirable outcomes such as muscle fatigue or over-use.

  • 350.
    Srinivasan, Divya
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Sandlund, Jonas
    Umeå University, Department of Community Medicine and Rehabilitation, Physiotherapy.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Motor variability traits among individuals performing repetitive precision work2014In: Proceedings of the 11th International Symposium on Human Factors in Organizational Design and Management (ODAM), and 46th Annual Nordic Ergonomics Society Conference (NES): Selected and peer reviewed papers / [ed] Ole Broberg et al., Santa Monica, CA: The IEA Press , 2014, p. 987-989Conference paper (Refereed)
    Abstract [en]

    Motor variability (MV) refers to the intrinsic variability naturally present in the motor control system. Occurring even in the simplest movements, it is usually manifested as a difference in joint movements, joint coordination and/or muscle activities between successive repeats of a task which are identical in performance. Contrary to the traditional view that MV is detrimental to performance, it is now widely accepted that MV may actually have an important functional role in skill acquisition, and that skilled performance may, actually, be associated with increased MV. Further, MV is related to pain and fatigue, and may play a decisive role in rehabilitation (reviewed in Srinivasan & Mathiassen 2012). Hypothetically, individuals with a larger MV would be better protected against overuse injuries, and recover faster after disorders affecting motor performance. However, whether the extent of MV is, indeed, a consistent individual trait across different tasks is not known.    

    The purpose of this study was to let individuals perform a laboratory-based simulation of repetitive upper-extremity precision work and determine:

    (i)             Whether it is possible to systematically classify individuals according to the size of their MV in repetitive work;

    (ii)            Whether classification of individuals in one working condition on one day persists even when some work-factors are slightly changed, and between different days when they perform the same work.

    Repetitive pipetting with a cycle time of 2.8s was performed in the laboratory by a group of 14 healthy female subjects, aged 20-45 years, right-handed and experienced in pipetting, on 3 different days under identical protocol and experimental conditions. Work factors such as work-pace, precision and cognitive load (on top of the pipetting work) were manipulated within each day. Kinematic data were obtained using electromagnetic motion capture systems (FASTRAK).

    MV in shoulder elevation, elbow flexion and shoulder-elbow coordination were operationalized using cycle-to-cycle standard deviations of motor parameters such as peak velocities, time lag of peak velocities, phase angle and inter-segmental phase angle. The resulting traits in individuals and the consistency of those traits across tasks and days will be presented.

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