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  • 551.
    Persson, Lina
    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.
    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.
    Variation i arbetet: växlingar mellan fysiska och mentala arbetsuppgifter: Företag D2017Report (Other academic)
  • 552.
    Picchiottino, Mathieu
    et al.
    CIAMS, Université Paris-Sud, Université Paris-Saclay, Orsay Cedex, France.
    Leboeuf-Yde, Charlotte
    Institute for Regional Health Research, University of Southern Denmark, Odense, Denmark.
    Gagey, Olivier
    CIAMS, Université Paris-Sud, Université Paris-Saclay, Orsay Cedex, France..
    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.
    The acute effects of joint manipulativetechniques on markers of autonomic nervous system activity: a systematic review and meta-analysis of randomized sham-controlled trials2019In: Chiropractic and Manual Therapies, ISSN 2045-709X, E-ISSN 2045-709X, Vol. 27, article id 17Article in journal (Refereed)
    Abstract [en]

    BackgroundThe autonomic nervous system (ANS) interests many chiropractors and manual therapists, because joint manipulative techniques (JMT), e.g. high velocity low amplitude (HVLA) manipulations and mobilizations, appear to produce acute changes in ANS mediated physiology. The complexity of this issue justifies a systematic critical literature review.

    ObjectiveTo review the literature comparing the acute changes in markers of ANS activity between JMT applied on spinal or peripheral joints and a sham procedure in healthy or symptomatic subjects.

    MethodWe searched PsycINFO, PEDro, PubMed, Cochrane library, EMBASE, and Medline up to December 2017. We updated the search with PubMed, Cochrane library, EMBASE, and Medline including July 2018. Inclusion criteria were: randomized sham-controlled trials assessing the effect of JMT on markers of ANS activity; manually applied JMT, regardless of technique, applied on either healthy or symptomatic humans; outcome measurements recorded at baseline and repeated during and/or after interventions. Selection of articles and data extraction were performed independently by two reviewers. The quality of studies was assessed using the Cochrane ‘risk of bias’ tool and a technical check-list. Results were reported narratively with some meta-analyses. The Cochrane GRADE approach was used to assess the certainty of evidence.

    ResultsTwenty-nine of 2267 studies were included in the synthesis. Mobilizations (oscillatory technique) probably produce an immediate and short-term, bilateral increase in skin sympathetic nerve activity (reflected by an increase in skin conductance) regardless of the area treated (moderate-certainty evidence). It is uncertain whether the sympathetic arousal also explains an increase in respiratory rate (very low-certainty evidence). Our evaluation of the literature suggests that spinal sustained apophyseal glides (SNAGs) mobilization and HVLA manipulation of the spine may have no acute effect on the studied markers of ANS activity (very low- to low-certainty evidence).

    ConclusionSome types of mobilizations probably produce an immediate and short-term, statistically significant increase in skin sympathetic nerve activity when compared to a sham procedure, whereas spinal SNAGs and spinal HVLA techniques may have no acute effect on the studied markers of ANS activity. No region-specific results were noted. The literature suffers from several shortcomings, for which reason we strongly suggest further research.

  • 553.
    Pulido, Jean Alexander
    et al.
    Centro de Estudios de Ergonomía, Department of Industrial Engineering, School of Engineering, Pontificia Universidad Javeriana, Bogotá.
    Barrero, Lope Hugo
    Centro de Estudios de Ergonomía, Department of Industrial Engineering, School of 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
    Department of Physical Therapy, Movement, and Rehabilitation Sciences, Bouvé College of Health Sciences, Northeastern University, Boston.
    Correctness of self-reported task durations: a systematic review: a systematic review2018In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 62, no 1, p. 1-16Article in journal (Refereed)
    Abstract [en]

    Background: Durations of tasks in a job is an essential interest in occupational epidemiology. Such durations are frequently measured using self-reports, which may, however, be associated with both bias and random errors. The present systematic literature review examines the correctness of self-reported durations of tasks, i.e. the extent to which they differ from more valid reference data due to either systematic or random error, and factors influencing this correctness, with particular emphasis on assessment of exposures of relevance to musculoskeletal disorders.

    Method: The search for relevant studies included the databases ISI web of Science, Medline, EBSCO HOST, Proquest and Psycnet.

    Results: Thirty-two articles were identified, 23 of which examined occupational tasks and nine non-occupational tasks. Agreement between self-reports and a more correct reference was reported for, in total, 182 tasks. Average proportional errors were, for most tasks, between -50% (i.e. underestimations) and +100%, with a dominance of overestimations; 22% of all results considered overestimations of 100% or more. For 15% of the 182 reported tasks, the mean difference between the self-reported and the reference duration value was less than 5%, and 20% of the 182 mean differences were between 5% and 20%. In general, respondents were able to correctly distinguish tasks of a longer duration from shorter tasks, even though the actual durations were not correct. A number of factors associated with the task per se appeared to influence agreement between self-reports and reference data, including:  type of task, true task duration, task pattern across time (continuous vs. discontinuous), and whether the addressed task is composed of subtasks. The musculoskeletal health status of the respondent did not have a clear effect on the ability to correctly report task durations. Studies differed in key design characteristics and detail of information reported, which hampers a formal aggregation of results.

    Discussion: The correctness of self-reported task durations is, at the best, moderate at the individual level, and this may present a significant problem when using self-reports in task-based assessment of individual job exposures. However, average self-reports at the group level appear reasonably correct, and may thus be a viable method in studies addressing, for instance, the relative occurrence of tasks in a production system. Due to the disparity of studies, definite conclusions on the quantitative effect on agreement of different modifiers are not justified, and we encourage future studies specifically devoted to understanding and controlling sources of bias in self-reported task durations. We also encourage studies developing decision support for when to apply or avoid self-reports to measure task durations, depending on study purpose and occupational setting.

  • 554.
    Pulido, Jean Alexander
    et al.
    Centro de Estudios de Ergonomía, Department of Industrial Engineering, School of Engineering, Pontificia Universidad Javeriana, Bogotá, Colombia.
    Barrero, Lope Hugo
    Centro de Estudios de Ergonomía, Department of Industrial Engineering, School of Engineering, Pontificia Universidad Javeriana, Bogotá, Colombia.
    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
    Department of Physical Therapy, Movement, and Rehabilitation Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA, USA.
    Torres, Paola
    Academic Research, Sede Santa Bárbara, Javesalud-IPS, Bogotá, Colombia.
    Bernal, Luis Gabriel
    Academic Research, Sede Santa Bárbara, Javesalud-IPS, Bogotá, Colombia.
    Differences in the accuracy of self-reported task durations between workers with and without acute non-specific low-back pain2015In: Proceedings of the 19th Triennial Congress of the International Ergonomics Association, Melbourne 9-14 August 2015, 2015Conference paper (Refereed)
  • 555.
    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.

  • 556.
    Radovanovic, Sasa
    et al.
    University of Gävle, Centre for Musculoskeletal Research.
    Day, Scott Jason
    Johansson, Håkan
    University of Gävle, Centre for Musculoskeletal Research.
    The impact of whole-hand vibration exposure on the sense of angular position about the wrist joint2006In: International Archives of Occupational and Environmental Health, ISSN 0340-0131, E-ISSN 1432-1246, Vol. 79, no 2, p. 153-160Article in journal (Refereed)
    Abstract [en]

    OBJECTIVES: The purpose of this research is to determine the impact of whole-hand vibration on the capacity of subjects to identify previously presented positions of the hand in both wrist flexion and extension. METHODS: In each movement direction, targets of 15 or 30 degrees were presented with an imposed passive movement from the start position. During the second imposed movement, subjects were required to identify when the target position had been reached. For the vibration condition, 15 s of whole-hand vibration exposure was repeated immediately prior to each target position trial. Proprioceptive capacity was assessed by comparing the identified angular position with the reference position-angular distance expressed in terms of absolute error (AE), constant error (CE), and variable error (VE). RESULTS: For three of the four target positions (15 and 30 degrees flexion and 15 degrees extension), the absolute, constant, and VEs of target identification were insensitive to vibration, whereas for the 30 degrees extension target, both the absolute and CE were significantly different before and after the vibration application, showing the subjects overshooting previously presented target position. All three error measures were larger for the long targets than the short targets. CONCLUSIONS: Short-duration exposure to whole-hand vibration is insufficient to compromise post-vibration position sense in the wrist joint, except near the end range of joint movement in wrist extension. Complement contribution of different proprioceptive receptors (muscle, joint, and skin receptors) seems to be crucial for accuracy to reproduce passive movements, since the capacity of any individual class of receptor to deliver information about movement and position of the limbs is limited.

  • 557.
    Radovanovic, Sasa
    et al.
    University of Gävle, Centre for Musculoskeletal Research.
    Dragasevic, N T
    Maric, J
    Milanovic, S
    Ljubisavljevic, Milos
    University of Gävle, Centre for Musculoskeletal Research.
    Kostic, V S
    Effects of transcranial magnetic stimulation of the cerebellum on performance of consecutive rapid movements in patients with idiopathic sporadic cerebellar ataxia and healthy subjects2006In: The Movement Disorder Society’s 10th International Congress of Parkinson’s Disease and Movement: October 28 - November 2, Kyoto, Japan, 2006Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    It is known that cerebellum influences the action of the motor system. The cerebellum may exert a facilitatory influence in the motor cortex, and should be involved in temporal computations in movement performance. The inability to compute time differences would affect time-related tasks. However, the cerebellar role to control precise movement performance is contradictory. Furthermore, facilitatory effect of cerebellum might be decreased in cerebellar degeneration. The aim of the study was to investigate the performance of the rapid movements in patients with “pure” cerebellar ataxia.

    Movement performance was compared in 13 patients and 8 healthy subjects. Movements were performed from the initial to the target position, with the movement length of 40 deg in the elbow flexion. Motor threshold (MT) of the motor cortex was determined and TMS was then applied right of the inion, in two conditions: With the strength of 5% below the MT, at the moment of command to start the flexion movement, and with the same strength 20 ms before the movement start. Two additional conditions were also tested: TM stimulus was applied with the strength of 30% above the MT at the moment of movement start, and at 20 ms before movement start.

    Patients perform significantly longer movements then healthy subjects, and accuracy of the movements deteriorates. Length of the movements was also prolonged in the conditions where stronger stimulus was applied. Accuracy of the movements in patients was not different when the stimulus was applied in the phase of the movement preparation, compared in moment 0 and -20 ms. Same was true for healthy subjects in both conditions - stimulus below and above MT.

    Results that differences in disturbance timing and strength have no clear effects might speak for preprogrammed characteristics of rapid movements in both healthy subjects and ataxia patients, where sensory input is not of primary importance. Deficits in cerebellar ataxia for the movement length may be attributable to improper processing of motor command and/or sensory information.

  • 558.
    Rashid, Mamunur
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology. University of Gävle, Centre for Musculoskeletal Research.
    Heiden, Marina
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, Occupational Health Science. University of Gävle, Centre for Musculoskeletal Research.
    Nilsson, Annika
    University of Gävle, Faculty of Health and Occupational Studies, Department of Caring Science, Caring Science.
    Kristofferzon, Marja-Leena
    University of Gävle, Faculty of Health and Occupational Studies, Department of Caring Science, Caring Science.
    Do work ability and well-being matter for return to work?: Cut-off points for Work Ability Index and Life Satisfaction questionnaire among women with long-term musculoskeletal painManuscript (preprint) (Other academic)
    Abstract [en]

    Objectives: To determine whether work ability and well-being predict return to work (RTW) among women with long-term neck/shoulder and/or back pain at a 1-year follow-up, and to assess the ability of the Work Ability Index (WAI) and Life Satisfaction questionnaire (LiSat-11) to discriminate between those who did RTW and those who did not RTW. 

    Methods: A survey was sent to 600 women receiving time-loss benefits from the Swedish Social Insurance Agency. In total, 208 women responded at baseline, and 141 at a 1-year follow-up. To identify whether work ability and well-being predicted RTW, multiple logistic regression analyses were performed with and without adjustment for type of work and pain intensity. To assess the discriminative ability of the WAI and LiSat-11 for women who did RTW and those who did not RTW, Receiver Operating Characteristic curves were fitted.  

    Results: Work ability predicted RTW, and the results remained significant after adjusting for type of work and pain intensity (OR 1.12, 95% CI: 1.04-1.22). Well-being was not significant. The WAI at baseline adequately discriminated between RTW and no RTW after one year (AUC 0.78, 95% CI 0.70-0.86), but the LiSat-11 did not.

    Conclusions: Our results indicate that work ability is an important factor for RTW among women on SL for long-term neck/shoulder and/or back pain. The WAI has adequate discriminatory ability in this population, but the LiSat-11 has not.  

     

    Keywords: Life satisfaction, Musculoskeletal pain, Sickness absence, Work status

  • 559.
    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.

  • 560.
    Rashid, Mamunur
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology. University of Gävle, Centre for Musculoskeletal Research.
    Kristofferzon, Marja-Leena
    University of Gävle, Faculty of Health and Occupational Studies, Department of Caring Science, Caring Science.
    Heiden, Marina
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, Occupational Health Science. University of Gävle, Centre for Musculoskeletal Research.
    Nilsson, Annika
    University of Gävle, Faculty of Health and Occupational Studies, Department of Caring Science, Caring Science.
    Predictors of return to work among women with long-term neck/shoulder and/or back pain: a 1-year prospective studyManuscript (preprint) (Other academic)
    Abstract [en]

    Objective: The aim of this study was to identify predictors of return to work (RTW) among women on sick leave due to long-term neck/shoulder and/or back pain.

    Methods: The study was a prospective survey with a 1-year follow-up. Data on predictors and outcome were collected using a self-administrated questionnaire containing eight instruments – Coping Strategies Questionnaire, General Self-Efficacy scale, Sense of Coherence, Multidimensional Pain Inventory, Hospital Anxiety and Depression Scale, Demand-Control-Support Questionnaire, Work Ability Index, and Life Satisfaction questionnaire, as well as a set of background questions. A total of 208 women, aged 23-63 years, were included at baseline, and 141 responded at the 1-year follow-up. Multiple logistic regression analyses were performed to identify predictors of RTW.

    Results: Of the 141 women, 94 had RTW and 47 had not at the 1-year follow-up. Women who engaged in more coping by increasing behavioral activities, such as leisure activities, reading and socialization, (OR 1.12, 95% CI 1.02-1.22) and those who more strongly believed they would return to the same work within 6 months (OR 1.24, 95% CI 1.12-1.38) had an increased probability of RTW. Getting more social support outside work (OR 0.49, 95% CI 0.26-0.90) decreased the odds of RTW at the 1-year follow-up.

    Conclusions: The findings suggested that behavioral activities, belief in returning to the same work and social support were predictors of RTW at the 1-year follow-up. Healthcare professionals should consider these predictors in efforts to prevent prolonged sick leave and to promote RTW among women with long-term neck/shoulder and/or back pain.

     

     

    Key terms: Follow-up study, musculoskeletal pain, prognostic factors, sickness absence, return to work.

     

  • 561.
    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

  • 562.
    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.

  • 563.
    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.

  • 564.
    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)
  • 565.
    Rezagholi, Mahmoud
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research. Uppsala universitet, Institutionen för medicinska vetenskaper.
    Cost-Efficient Designs for Assessing Work-Related Biomechanical Exposures2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Work-related disorders due to biomechanical exposures have been subject to extensive research. Studies addressing these exposures have, however, paid limited attention to an efficient use of resources in exposure assessment. The present thesis investigates cost-efficient procedures for assessment of work-related biomechanical exposures, i.e. procedures aiming at a proper balance between statistical and economic performance.

    Paper I is a systematic review of tools used in literature providing cost-efficient data collection designs. Two main approaches were identified in nine publications, i.e. comparing cost efficiency among alternative data collection designs, and optimizing resource allocation between different stages of data collection, e.g. subjects and samples within subjects. The studies presented, in general, simplified analyses, in particular with respect to economics.

    Paper II compared the cost-efficiency of four video-based techniques for assessing upper arm postures. The comparison was based both on a comprehensive model of cost and error and additionally on two simplified models. Labour costs were a dominant factor in the cost efficiency comparison. Measurement bias and costs other than labour cost influenced the rank and economic evaluation of the assessment techniques.

    Paper III compared the cost efficiency of different combinations of direct and indirect methods for exposure assessments. Although a combination of methods could significantly reduce the total cost of obtaining a desired level of precision, the total cost was, in the investigated scenario, lowest when only direct measurements were performed. However, when the total number of measurements was fixed, a combination was the most cost efficient choice.

    In Paper IV, demand functions were derived for a four-stage measurement strategy with the focus of either minimizing the cost for a required precision, or maximizing the precision for a predetermined budget. The paper presents algorithms for identifying optimal values of measurement inputs at all four stages, adjusted to integers, as necessary for practical application.

    In summary, the thesis shows that it is important to address all sources of costs and errors associated with alternative measurement designs in any particular study, and that an optimal determination of samples at different stages can be identified in several cases not previously addressed in the literature.         

  • 566.
    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. 

  • 567.
    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.

  • 568.
    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.

  • 569.
    Rezagholi, Mahmoud
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. 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, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Cost-Efficient Design of Occupational Exposure Assessment Strategies: A Review2010In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 54, no 8, p. 858-868Article in journal (Refereed)
    Abstract [en]

    When designing a strategy for collecting occupational exposure data, both economic and statistical performance criteria should be considered. However, very few studies have addressed the trade-off between the cost of obtaining data and the precision/accuracy of the exposure estimate as a research issue. To highlight the need of providing cost-efficient designs for assessing exposure variables in occupational research, the present review explains and critically evaluates the concepts and analytical tools used in available cost efficiency studies. Nine studies were identified through a systematic search using two algorithms in the databases PubMed and ScienceDirect. Two main approaches could be identified in these studies: comparisons of the cost efficiency associated with different measurement designs, and optimizations of resource allocation on the basis of functions describing cost and statistical efficiency. In either case, the reviewed studies use simplified analytical tools and insufficient economic analyses. More research is needed to understand whether these drawbacks jeopardize the guidance on cost-efficient exposure assessment provided by the studies, as well as to support theoretical results by empirical data from occupational life.

  • 570.
    Rezagholi, Mahmoud
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. 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, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Liv, Per
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Cost efficiency comparison of four video-based techniques for assessing upper arm postures2012In: Ergonomics, ISSN 0014-0139, E-ISSN 1366-5847, Vol. 55, no 3, p. 350-360Article in journal (Refereed)
    Abstract [en]

    Many video-based techniques for assessing postures at work have been developed. Choosing the most appropriate technique should be based on an evaluation of different alternatives in terms of their ability to produce posture information at low input costs, i.e. their cost efficiency. This study compared four video-based techniques for assessing upper arm postures, using cost and error data from an investigation on hairdressers. Labour costs associated with the posture assessments from the video recordings were the dominant factor in the cost efficiency comparison. Thus, a work sampling technique associated with relatively large errors appeared, in general, to be the most cost-efficient because it was labour-saving. Measurement bias and other costs than labour cost for posture assessment influenced the ranking and economic evaluation of techniques, as did the applied measurement strategy, i.e. the number of video recordings and the number of repeated assessments of them.

  • 571.
    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.

  • 572.
    Richter, Hans
    et al.
    University of Gävle, Centre for Musculoskeletal Research.
    Bänziger, Tanja
    University of Gävle, Centre for Musculoskeletal Research.
    Saber, A
    Forsman, Mikael
    Low-level experimental accommodative/vergence load and trapezius muscle activity2009In: Proceedings of 17th World Congress of Ergonomics, 2009Conference paper (Refereed)
  • 573.
    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.

  • 574.
    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.

  • 575.
    Richter, Hans
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, Occupational Health Science. University of Gävle, Centre for Musculoskeletal Research. Högskolan i Gävle.
    Domkin, Dmitry
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, 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 Health Science and Psychology, Occupational Health Science. University of Gävle, Centre for Musculoskeletal Research.
    Andersson, H. W.
    Skogforsk, the forestry research institute of Sweden, Uppsala, Sweden.
    Högberg, Hans
    University of Gävle, Faculty of Health and Occupational Studies, Department of Caring Science, Caring Science.
    Englund, Martin
    Skogforsk, the forestry research institute of Sweden, Uppsala, Sweden.
    A Comparison of Mental and Visual Load Resulting from Semi-automated and Conventional Forest Forwarding: An Experimental Machine Simulation Study2019In: Proceedings of the 20th Congress of the International Ergonomics Association (IEA 2018): Volume X: Auditory and Vocal Ergonomics, Visual Ergonomics, Psychophysiology in Ergonomics, Ergonomics in Advanced Imaging / [ed] Bagnara S., Tartaglia R., Albolino S., Alexander T., Fujita Y., Cham, 2019, 827, Vol. X, p. 199-208Conference paper (Refereed)
    Abstract [en]

    The purpose of the present study was to extend the knowledge offunctional linkages between visual and mental load, performance, and prefrontalcortex (PFC) activity, during forestry forwarding 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 machinesimulator during two counterbalanced test conditions: (i) conventional cranecontrol, and; (ii) semi-automated crane control. Mental load was assessed byquantification of oxygenated hemoglobin (HbO2) concentration changes overthe right dorsolateral prefrontal cortex (dlPFC) via non-invasive functional nearinfrared spectrometry (fNIRS). Visual, autonomic, and motoric control variableswere measured and analyzed in parallel along with the individual level of performance.Linear Mixed Models (LMM) analysis indicated more mental loadduring conventional crane work. Collectively, our data suggest that fNIRS is aviable tool which can be used in neuroergonomic research to evaluate physiologicalactivity levels in PFC.

  • 576.
    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.

  • 577.
    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)
  • 578.
    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.

  • 579.
    Richter, Hans
    et al.
    University of Gävle, Centre for Musculoskeletal Research.
    Lodin, Camilla
    University of Gävle, Centre for Musculoskeletal Research.
    Why eye strain can be pain in the neck2008Conference paper (Refereed)
  • 580.
    Richter, Hans
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Lodin, Camilla
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Forsman, Mikael
    Karolinska institutet.
    Temporal aspects of increases in eye-neck activation levels during visually deficient near work2012In: Work: A journal of Prevention, Assesment and rehabilitation, ISSN 1051-9815, E-ISSN 1875-9270, Vol. 41, no Suppl. 1, p. 3379-3384Article in journal (Refereed)
    Abstract [en]

    In an experimental study two levels of oculomotor load were induced via optical trial lenses. Trapezius muscle activity was measured with bipolar surface electromyography and normalized to a submaximal contraction. Sixty-six subjects with a median age of 36 (range 19–47, std 8) viewed a black and white Gabor grating (5 c/deg) for two 7-min periods monocularly through a 0 D lens or binocularly through -3.5 D lenses. The effect of time was separately regressed to EMG in two different subgroups of responders: a High-Oculomotor-Load (HOL) and a Low-Oculomotor-Load (LOL) group. A linear regression model was fitted on group level with exposure time on the x-axis and normalized trapezius muscle EMG (%RVE) on the y-axis. The slope coefficient was significantly positive in the -D blur condition for only the HOL subgroup of responders: 0.926 + Time min 1-7x 0.088 (p = 0.002, r2 =0.865). There was no obvious sign of this activity to level off or to stabilize. These results suggest that professional information technology users that are exposed to a high level of oculomotor load, during extended times, are at an increased risk of exhibiting an increased trap.m. activity.

  • 581.
    Richter, Hans
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, Occupational Health Science. University of Gävle, Centre for Musculoskeletal Research.
    Long, Jennifer
    School of Optometry and Vision Science, UNSW Sydney, Sydney, AUSTRALIA.
    The pitfalls of the traditional office ergonomics model in the current mobile work environment:  Is visual ergonomic health literacy the remedy?2019In: Work: A journal of Prevention, Assessment and rehabilitation, ISSN 1051-9815, E-ISSN 1875-9270, Vol. 63, no 3, p. 447-456Article in journal (Refereed)
    Abstract [en]

    Mobile technology has revolutionised how we work. It is now relatively easy to work anywhere and anytime, but this has placed the onus on mobile (or flexible) workers to set up their own work environment for comfort and ease of use. Vision is an important driver of posture, and hence visual ergonomics principles are integral for setting up digital devices. If mobile workers do not have visual ergonomics knowledge, or are unable to apply visual ergonomics knowledge to appropriately set up their work environment, then they are at risk of developing visual-related occupational health issues due to exposure to adverse physical work environments.

    To address this potential health care issue, we propose the introduction of Visual Ergonomics Health Literacy. This would provide mobile workers (including school children) with the knowledge and skills to set up their work environment for comfort and ease of use, wherever they work. It is important to address this issue now before we have a widespread epidemic of discomfort and injury from not applying sound visual ergonomics principles to work environments.

  • 582.
    Richter, Hans O
    University of Gävle, Centre for Musculoskeletal Research.
    Accommodative/vergence performance following low-levels sustained oculomotor load2007In: 30th European Conference on Visual Perception: Perception 36 Suppl., 2007, p. 30-Conference paper (Other academic)
  • 583.
    Richter, Hans O
    University of Gävle, Centre for Musculoskeletal Research.
    Eye-neck/scapular area interactions during strenuous near work: biologically plausible pathways with relevance for work related musculoskeletal disorders of the neck and upper extremity2008In: Zeitschrift für Arbeitswissenschaft, ISSN 0340-2444, Vol. 3, no 62, p. 190-199Article in journal (Refereed)
    Abstract [en]

    The time honoured dictum “the eyes steer the body” has gained additional legitimacy in recent years with the advent of new mechanisms which link the visual and musculoskeletal system with one another. A systematic review of the circumstances, under which a change in accommodation/vergence loads actually lead to alterations in physiological levels of musculoskeletal tonus, or vice versa, therefore, appears timely.

  • 584.
    Richter, Hans O
    University of Gävle, Centre for Musculoskeletal Research.
    Neck shoulder activation induced by deficient visual quality2007In: 39th Annual Congress of the Nordic Ergonomics Society, 2007Conference paper (Other academic)
  • 585.
    Richter, Hans O.
    et al.
    University of Gävle, Centre for Musculoskeletal Research.
    Bänziger, Tanja
    Abdi, S.
    Forsman, Mikael
    Low-level sustained accommodative/vergence loads, eyestrain and trapezius muscle activity2008In: Perception, ISSN 0301-0066, E-ISSN 1468-4233, Vol. 37, no Suppl., p. 24-24Article in journal (Refereed)
  • 586.
    Richter, Hans O.
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Bänziger, Tanja
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Abdi, S.
    The Bernadotte Laboratories, St. Erik’s Eye Hospital, Department of Clinical Neuroscience, Karolinska Institutet, Sweden.
    Forsman, Mikael
    Division of Occupational and Environmental Medicine, Department of Public Health Sciences, Karolinska Institutet, Sweden.
    Stabilization of gaze: A relationship between ciliary muscle contraction and trapezius muscle activity2010In: Vision Research, ISSN 0042-6989, E-ISSN 1878-5646, Vol. 50, no 23, p. 2559-2569Article in journal (Refereed)
    Abstract [en]

    In an experimental study four levels of oculomotor load were induced binocularly. Trapezius muscle activity was measured with bipolar surface electromyography and normalized to a submaximal contraction. Twenty-eight subjects with a mean age of 29 (range 19–42, std 8) viewed a high-contrast fixationt arget for four 5-min periods through: (i) 3.5 dioptre (D) lenses; (ii) 0 D lenses; (iii) individuallya djusted prism D lenses (1–2 D base out); and (iv) +3.5 D lenses. The target was placed close to thei ndividual’s age-appropriate near point of accommodation in conditions (i–iii) and at 3 m in condition( iv). Each subject’s ability to compensate for the added blur was extracted via infrared photorefraction measurements. A bitwise linear regression model was fitted on group level with eye-lens refraction on the x-axis and normalized trapezius muscle EMG (%RVE) on the y -axis. The model had a constant level of trapezius muscle activity – where subjects had not compensated for the incurred defocus by a change in eye-lens accommodation – and a slope, where the subjects had compensated. The slope coefficient was significantly positive in the D (i) and the +D blur conditions (iv). During no blur (ii) and prism blur (iii) there were no signs of relationships. Nor was there any sign of relationship between the convergence response and trapezius muscle EMG in any of the experimental conditions. The results appear directly attributable to an engagement of the eye-lens accommodative system and most likely reflect sensorimotor processing along its reflex arc for the purpose of achieving stabilization of gaze

  • 587.
    Richter, Hans O.
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Bänziger, Tanja
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Forsman, Mikael
    Division of Occupational and Environmental Medicine, Department of Public Health Sciences, Karolinska Institutet, Sweden.
    Eye-lens accommodation load and static trapezius muscle activity2011In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 111, no 1, p. 29-36Article in journal (Refereed)
    Abstract [en]

    The purpose of this experimental study was to investigate if sustained periods of oculomotor load impacts on neck/scapular area muscle activity. The static trapezius muscle activity was assessed from bipolar surface electromyography, normalized to a submaximal contraction. Twenty-eight subjects with a mean age of 29 (range 19–42, SD 8) viewed a high-contrast fixation target for two 5-min periods through: (1) -3.5 dioptre (D) lenses; and (2) 0 D lenses. The target was placed 5 D away from the individual’s near point of accommodation. Each subject’s ability to compensate for the added blur was extracted via infrared photorefraction measurements. Subjects whose accommodative response was higher in the -D blur condition (1) showed relatively more static bilateral trapezius muscle activity level. During no blur (2) there were no signs of relationships. The results indicate that sustained eye-lens accommodation at near, during ergonomically unfavourable viewing conditions, could possibly represent a risk factor for trapezius muscle myalgia.

  • 588.
    Richter, Hans O
    et al.
    University of Gävle, Centre for Musculoskeletal Research.
    Crenshaw, Albert
    University of Gävle, Centre for Musculoskeletal Research.
    Djupsjöbacka, Mats
    University of Gävle, Centre for Musculoskeletal Research.
    Kjellberg, Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Lyskov, Eugene
    University of Gävle, Centre for Musculoskeletal Research.
    Accommodative/vergence eye-movements in response to optical blur and musculoskeletal discomfort2007In: Work with computing systems - WWCS 2007, Stockholm: Computing systems for human benefits from the 8th International Conference on Work With Computing Systems : May 21st-24th 2007, Stockholm Sweden, Stockholm: Royal institute of technology , 2007, p. 125-125Conference paper (Refereed)
  • 589.
    Richter, Hans O
    et al.
    University of Gävle, Centre for Musculoskeletal Research.
    Crenshaw, Albert
    University of Gävle, Centre for Musculoskeletal Research.
    Lyskov, Eugene
    University of Gävle, Centre for Musculoskeletal Research.
    Accommodation – vergence performance after low levels of oculomotor load2007In: Scandinavian Journal of Work, Environment and Health, ISSN 0355-3140, E-ISSN 1795-990X, no 3, p. 60-67Article in journal (Refereed)
    Abstract [en]

    Objectives This experimental pilot study assessed the effects of sustained low-level accommodative vergence loads on oculomotor performance, eyestrain, and musculoskeletal functioning.

    Methods A high-contrast fixation-point stimulus [light-emitting diode (LED)] was introduced into the optical axis of the viewing eye or into the midline in case of binocular viewing. The participants (N=6) were asked to compensate for the blur incurred by adjusting the strength of their eye lens. The participants performed in the following three standardized sequential viewing tasks: (i) resting with eyes open in darkness, (ii) accommodating alternately on a near versus a far LED illuminated sequentially (near–far response), and (iii) sustained fixation upon a LED at near. After the third task, the first and second tasks were repeated once.

    Results The main effects of the third task were to decrease the overall rate of binocular accommodative relaxation time (diopters/s) in the repetition of the second task trial. The baseline shifts in individual response times also correlated with changes in the response amplitudes under the binocular stimulus conditions, which required contraction of the ciliary muscle.

    Conclusions The results taken as a whole validate a technique of essential interest to applied vision research.

  • 590.
    Richter, Hans O
    et al.
    University of Gävle, Centre for Musculoskeletal Research.
    Crenshaw, Albert
    University of Gävle, Centre for Musculoskeletal Research.
    Lyskov, Eugene
    University of Gävle, Centre for Musculoskeletal Research.
    Low-levels sustained accommodative/vergence loads, eyestrain and neck-shoulder discomfort2007In: Work With Display Unit, 2007Conference paper (Other academic)
  • 591.
    Richter, Hans O
    et al.
    University of Gävle, Centre for Musculoskeletal Research.
    Elfström, A
    Kjellberg, Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Zetterström,
    Wiholm, Clairy
    Visual stress a risk factor for musculo-skeletal complaints in visual display unit workers2007In: Work With Display Unit, 2007Conference paper (Other (popular science, discussion, etc.))
  • 592.
    Richter, Hans O
    et al.
    University of Gävle, Centre for Musculoskeletal Research.
    Knez, Igor
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Superior low-wavelength contrast sensitivity in asthenopics during voluntary efforts to accommodation2006In: 29th European Conference on Visual Perception: Perception 35. Suppl, 2006, p. 131-131Conference paper (Other academic)
    Abstract [en]

    The purpose of this work was to characterise short-(S)-wavelength-sensitive-cone mediated contrast sensitivity (CS) across twenty symptom-free subjects and eight asthenopics, all with normal-unaided-or-corrected visual acuity with no sign of oculomotor dysfunction. Threshold contrast sensitivity was assessed by the von Békésy tracking method from a viewing distance of 2.4 m (0.40 D). Three counterbalanced tasks required central fixation of black-and-white square-wave gratings (1, 5, 10, 14, and 17 cycles deg-1) presented through a low-pass (400 - 450 nm) tinted blue lens: through (i) a 0.0 D lens, (ii) a -1.50 D lens, (iii) a +1.50 D lens while attempting volitional accommodation to minimise blur. Baseline increases in eye-strain, which approached high levels at the end of the experiment, did not differentiate between the two groups of volunteers. Compared with symptom-free subjects, asthenopics exhibited larger magnitudes CS performance in the intermediate spatial frequencies during experimental conditions requiring voluntary increases in accommodation. The residual filtered light may encompass reference wavelengths habitually used by the asthenopics in retinal alignment as an adaptive strategy to spare accommodation from eye-strain. Alternatively, asthenopics, owing to inherent retinal factors, may 'drive' their accommodative system harder than symptom-free subjects.[Supported by the Swedish Council for Working Life and Social Research Grant 2005-0488 to HR.]

  • 593.
    Richter, Hans O.
    et al.
    University of Gävle, Centre for Musculoskeletal Research. University of Gävle, Department of Education and Psychology, Ämnesavdelningen för psykologi.
    Knez, Igor
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Superior short-wavelength contrast sensitivity in asthenopics during reflexive readjustments of ocular accommodation2007In: Ophthalmic & physiological optics, ISSN 0275-5408, E-ISSN 1475-1313, Vol. 27, no 4, p. 361-372Article in journal (Refereed)
    Abstract [en]

    The purpose of this work was to characterize contrast sensitivity (CS) under short-wavelength illumination in 20 symptom-free subjects and eight asthenopics: all had normal unaided or corrected visual acuity and no sign of oculomotor disease. Threshold CS was assessed using the von Bekesy tracking method from a viewing distance of 2.4 m (0.40 D). Three counterbalanced tasks required central fixation of black-and-white square-wave gratings (1, 5, 10, 14 and 17 c/deg) presented through a low-pass filter blue lens and (1) a +1.50 D lens; (2) a -1.50 D lens and (3) a 0 D lens, while attempting accommodation to minimize blur. Baseline increases in eye strain, which approached high levels at the end of the experiment, did not differentiate between the two groups of volunteers. All the subjects made evident appropriate accommodation during the low blur condition (0 D); the CS curve exhibited the expected characteristics. When the minus lens was placed before the eyes of the observers the distant square-wave gratings were still seen clearly, the eyes presumably had accommodated by an amount equal to the power of the negative lens. Compared with symptom-free subjects, asthenopics exhibited greater CS at the intermediate spatial frequencies both during the low blur and the minus blur conditions. Asthenopics may exhibit an individualized sensory tendency to react more strongly to shorter wavelengths of light and may therefore reflexively 'drive' their accommodative system harder than symptom-free subjects. This would explain the presence of their asthenopia in the first place. Blue light may, in addition, induce more arousal and higher alertness in this category of participants. This would boost the oculomotor aspects of their performance. These findings add to the current understanding of individual variability in the level of oculomotor loads following strenuous near work.

  • 594.
    Richter, Hans O.
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Röijezon, Ulrik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Björklund, Martin
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. 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, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Long-term adaptation to neck/shoulder pain and perceptual performance in a hand laterality motor imagery test2010In: Perception, ISSN 0301-0066, E-ISSN 1468-4233, Vol. 39, no 1, p. 119-130Article in journal (Refereed)
    Abstract [en]

    The effect of neck/shoulder pain on the performance in a hand laterality motor imagery test was studied. Responses to the Cooper and Shepard (1975, Journal of Experimental Psychology: Human Perception and Performance 104 48 ^ 56) hand laterality test were explored in twenty-four individuals with chronic non-specific neck pain and twenty-one subjects with chronic neck pain of traumatic origin (whiplash-associated disorder). Twenty-two controls were also included in the study. Digitalised right- or left-hand stimuli were presented at five different stimulus angles (08, 458 laterally, 908 laterally, 1358 laterally, and 1808). The experimental task was to decide the laterality as fast and accurately as possible. The performance, both reaction time (RT) and accuracy, of the two experimental groups was contrasted with that of the control group. The main results revealed that the subjects afflicted with whiplash injury on the average exhibited a faster response pattern than symptom-free healthy controls. Despite their  usculoskeletal deficits and experience of pain these volunteers also exhibited a preserved speed ^ accuracy tradeoff. Longer duration of time with symptoms of neck pain was, moreover, associated with progressively faster RTs. These results point to perceptual learning and may reflect different stages of adaptation to neck pain.

  • 595.
    Richter, Hans O.
    et al.
    University of Gävle, Centre for Musculoskeletal Research. University of Gävle, Department of Education and Psychology, Ämnesavdelningen för folkhälsovetenskap. Department of Optometry and Optical Science, Faculty of Physics and Mathematics, University of Latvia, Riga, Latvia.
    Wennberg, Patrik
    Department of Optometry and Optical Science, Faculty of Physics and Mathematics, University of Latvia, Riga, Latvia.
    Raudsepp, Jaanus
    University of Gävle, Centre for Musculoskeletal Research.
    The effects of inverting prisms on the horizontal-vertical illusion: a systematic effect of downward gaze2007In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 183, no 1, p. 9-15Article in journal (Refereed)
    Abstract [en]

    The purpose of this work is to compare the relative contributions from the extraocular and sensory systems on the magnitude of the horizontal-vertical illusion (HVI). The visual HVI refers to the general tendency to overestimate vertical extensions of small-scale lines on a picture plane relative to the horizontal by 4-16% depending on the method of measurement. The HVI line stimuli consisted of luminous vertical and horizontal lines forming "L-profiles" located in the frontoparallel plane at a 45 cm viewing distance, collinearly with a binocular gaze. The home position of gaze was aligned to the center of the screen with the ear-eye angle concordant with the environmental horizontal. Illusion strength was quantified when subjects fixated the HVI line stimuli in four quadrants of the visual field. The HVI was also viewed through prism lenses that inverted the retinal images by 180 degrees , thereby dissociating the sensory "up-down" direction from the oculomotor up-down frame of reference. The results revealed a systematically lower magnitude of the HVI in the bottom visual field regardless of whether subjects fixated the HVI with the distorting prisms or without. Taken together, these results suggest that the HVI is sensitive to small-angle gaze shifts. In agreement with several recent findings, these results are interpreted as implying that the brain imposes an enhanced analytic structure on the ascending sensory information during downward gaze.

  • 596.
    Richter, Hans O.
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Zetterlund, Christina
    The Low Vision Centre, Örebro County Council, Örebro, Sweden. Centre for Rehabilitation Research, Örebro University Hospital, Örebro, Sweden.
    Lundqvist, Lars-Olov
    Centre for Rehabilitation Research, Örebro University Hospital, Örebro, Sweden.
    Eye-neck interactions triggered by gaze control during visually deficient it-work probed by path analysis2010In: NES2010, 2010Conference paper (Refereed)
  • 597.
    Richter, Hans O.
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, CBF. University of Gävle, Centre for Musculoskeletal Research.
    Zetterlund, Christina
    The Low Vision Centre, Örebro County Council, Örebro, Sweden, and Centre for Rehabilitation Research, Örebro University Hospital, Örebro, Sweden.
    Lundqvist, Lars-Olov
    Centre for Rehabilitation Research, Örebro University Hospital, Örebro, Sweden.
    Eye-neck interactions triggered by visually deficient computer work2011In: Work: A journal of Prevention, Assesment and rehabilitation, ISSN 1051-9815, E-ISSN 1875-9270, Vol. 39, no 1, p. 67-78Article in journal (Refereed)
    Abstract [en]

    Objectives: To study the joint occurrence of eye-and-neck/scapular area symptoms and their association with occupational risk factors in a cross-sectional sample of professional information technology users. Study population: The participants consisted of 3,971 employees who worked with computers for a minimum of one hour a day. 2,551 (73%) were men and 945 (27%) women, with an age range of 18 up to 64 years. The mean age was 38.1 (SD = 10.7) for men and 37.6 (SD = 12.0) for the women. The measures were obtained via a self-administered survey in combination with a visual examination conducted by an optometrist. Methods: Two complementary logistic regression analyses with forced entry was conducted on n = 3,496 (88% adjusted response rate) cases. The effect of ocular symptoms on the risk of reporting musculoskeletal symptoms, or vice versa, was examined first in two separate binominal logistic regression analyses. Age, Gender, Near work variable and Visual functioning variables were included in these analyzes. Variables associated with the risk of developing an increase in either symptom category were also examined in two additional binomial logistic regression analyses. Results: Exposure to spectacles (single vision, multifocal, or progressive correction) in combination with a visual acuity < 1 surfaced as a key mediator of symptoms from the neck/scapular area (p < 0.01). A vergence disparity (uncompensated vergence error) similarly was associated with an augmented risk of developing an increase in neck/scapular area symptoms (p < 0.05). The most influential risk factor for neck/scapular area symptoms were ocular symptoms and vice versa (p < 0.0001). Conclusions: The results support the hypothesis which postulates that eye-neck/scapular area symptoms interaction may be due to a functional coupling from and between the eye-neck/scapular area muscles [28].

  • 598.
    Richter, Hans
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, Occupational Health Science. University of Gävle, Centre for Musculoskeletal Research.
    Sundin, Sofia
    Long, Jennifer
    School of Optometry and Vision Science, UNSW Sydney, Australia; Jennifer Long Visual Ergonomics, Katoomba, NSW, Australia.
    Visually deficient working conditions and reduced work performance in office workers: Is it mediated by visual well-being and health?2019In: International Journal of Industrial Ergonomics, ISSN 0169-8141, E-ISSN 1872-8219, Vol. 72, p. 128-136Article in journal (Refereed)
    Abstract [en]

    Introduction: The main purpose of this cross-sectional study was to investigate whether visual well-being and health act as a mediating factor between perceived visual ergonomic working conditions and self-rated visual performance among office workers who perform administrative tasks and computer-based work at the Swedish Tax Agency.

    Methods: A questionnaire was sent to 94 office workers addressing: 1) perceived visual quality of the visual display units; 2) prevalence of eye symptoms; and 3) self-rated visual performance. Eighty-six persons (54 women (63 %), 31 men (36 %), and 1 of unspecified sex) answered the questionnaire. Multiple regression analysis investigated the association between visual ergonomic working conditions and visual performance, with and without visual well-being and health as a mediator.

    Results: The group mean of the Indexed survey questions indicated reasonably good quality visual ergonomic working conditions, a relative absence of eye symptoms, and acceptable self-rated visual performance. Results from multiple regression analysis showed a significant association between perceived visual ergonomic working conditions and self-rated visual performance (r2 = 0.30, β = 0.327, p < 0.01). When visual well-being and health was used as a mediator, the association between perceived visual ergonomic working conditions and self-rated visual performance remained the same (r2 = 0.32, β = 0.315, p < 0.01).

    Discussion: It was surprising to discover that self-rated visual performance  was independent of visual health and well-being. Possible explanations include exposure factors not included in the current study, such as dry air and sensory irritation in eyes, psychosocial stress, time spent performing near work activities or time exposed to visually deficient working conditions. The strong connection between satisfaction with visual ergonomics work conditions and productivity found in this study has implications for workplace profitability and staff satisfaction. If productivity of office workers is improved by better visual ergonomics work conditions, then managers within workplaces may be able to improve work outcomes by optimizing the physical work environment.

  • 599.
    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.

  • 600.
    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.

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