This study investigated temporal changes in movement strategy and performance during fatiguing short-cycle work. Eighteen participants performed six 7-minutes work blocks with repetitive reaching movements at 0.5 Hz, each followed by a 5.5-minute rest break for a total duration of one hour. Electromyography (EMG) was collected continuously from the upper trapezius muscle, the temporal movement strategy and timing errors were obtained on a cycle-to-cycle basis, and perceived fatigue was rated before and after each work block. Clear signs of fatigue according to subjective ratings and EMG manifestations developed within each work block, as well as during the entire hour. For most participants, timing errors gradually increased, as did the waiting time at the near target. Changes in temporal movement strategy were negatively correlated with changes in the level and variability of EMG, suggesting that an adaptive temporal strategy offset the development of unstable motor solutions in this fatiguing, short-cycle work

Patients suffering from work-related muscle pain (WRMP) fatigue earlier during exercise than healthy controls. Inadequate oxygen consumption and/or inadequate blood supply can influence the ability of the muscles to withstand fatigue. However, it remains unknown if oxygenation and hemodynamics are associated with early fatigue in muscles of WRMP patients. In the present study we applied near-infrared spectroscopy (NIRS) on the extensor carpi radialis (ECR) and trapezius (TD) muscles of patients with WRMP (n = 18) and healthy controls (n = 17). Our objective was to determine if there were group differences in endurance times for a low-level contraction of 15% maximal voluntary contraction (MVC) – sustained for 12-13 min, and to see if these differences were associated with differences in muscle oxygenation and hemodynamics. At baseline, oxygen saturation (StO₂%) was similar between groups for the ECR, but StO₂% was significantly lower for TD for the WRMP patients (76%) compared to controls (85%) (P < 0.01). Also, baseline ECR blood flow was similar in the two groups. For both muscles there were a larger number of patients, compared to controls, that did not maintain the 15% MVC for the allotted time. Consequently, the endurance times were significantly shorter for the WRMP patients than controls (medians, ECR: 347 s vs. 582 s; TD: 430 s vs. 723 s respectively). Responses in StO₂% during the contractions were not significantly different between groups for either muscle, i.e. no apparent difference in oxygen consumption. Overall, we interpret our findings to indicate that the early fatigue for our WRMP patients was not associated with muscle oxygenation and hemodynamics.

Objective:  This study systematically summarizes biochemical biomarker research in non-traumatic musculoskeletal disorders (MSDs).  Two research questions guided the review:  1) Are there biochemical markers associated with neck and upper extremity MSDs? and, 2) Are there biochemical markers associated with the severity of neck and upper extremity MSDs? 

Methods:  A literature search was conducted in PubMed and SCOPUS.  Eighty-seven studies met primary inclusion criteria.  Following a quality screen, data were extracted from 44 sufficient quality articles.

Results:  Most of the 87 studies were cross-sectional and utilized convenience samples of patients as both cases and controls.  A response rate was explicitly stated in only 11 (13%) studies.  Less than half of the studies controlled for potential confounding through restriction or in the analysis.  Most sufficient quality studies were conducted in older populations (mean age in one or more analysis group > 50 yrs).

In sufficient quality articles, 82% demonstrated at least one statistically significant association between the MSD(s) and biomarker(s) studied.  Evidence suggested that: a) the collagen repair marker TIMP-1 is decreased in fibroproliferative disorders, b) 5-HT (serotonin) is increased in trapezius myalgia, and c) triglycerides are increased in a variety of MSDs.  Only five studies showed an association between a biochemical marker and MSD severity.

Conclusion: While some MSD biomarkers were identified, limitations in the articles examined included possible selection bias, confounding, spectrum effect (potentially heterogeneous biomarker associations in populations according to symptom severity or duration) and insufficient attention to co-morbid conditions. A list of recommendations for future studies is provided.

Background

This study systematically summarizes quantitative imaging biomarker research in non-traumatic neck and shoulder musculoskeletal disorders (MSDs). There were two research questions: 1) Are there quantitative imaging biomarkers associated with the presence of neck and shoulder MSDs?, 2) Are there quantitative imaging biomarkers associated with the severity of neck and shoulder MSDs?

Methods

PubMed and SCOPUS were used for the literature search. One hundred and twenty-five studies met primary inclusion criteria. Data were extracted from 49 sufficient quality studies.

Results

Most of the 125 studies were cross-sectional and utilized convenience samples of patients as both cases and controls. Only half controlled for potential confounders via exclusion or in the analysis. Approximately one-third reported response rates. In sufficient quality articles, 82% demonstrated at least one statistically significant association between the MSD(s) and biomarker(s) studied. The literature synthesis suggested that neck muscle size may be decreased in neck pain, and trapezius myalgia and neck/shoulder pain may be associated with reduced vascularity in the trapezius and reduced trapezius oxygen saturation at rest and in response to upper extremity tasks. Reduced vascularity in the supraspinatus tendon may also be a feature in rotator cuff tears. Five of eight studies showed an association between a quantitative imaging marker and MSD severity.

Conclusions

Although research on quantitative imaging biomarkers is still in a nascent stage, some MSD biomarkers were identified. There are limitations in the articles examined, including possible selection bias and inattention to potentially confounding factors. Recommendations for future studies are provided.

Background. Although the potential for musculoskeletal disorder (MSD) biomarkers to detect subclinical disease and monitor MSD severity was discussed more than 20 years ago, only one review on biochemical biomarkers exclusive to humans has been published (Saxton 2000). The aim of this study was to systematically summarize biochemical biomarker research in neck and upper extremity MSDs that could appear in a work-related context. Two research questions guided the review: (1) Are there biochemical markers associated with neck and upper extremity MSDs? (2) Are there biochemical markers associated with the severity of neck and upper extremity MSDs?

Methods: A literature search was conducted in PubMed and SCOPUS. 87 studies met primary inclusion criteria. Following a quality screen, data were extracted from 44 sufficient-quality articles.

Results. Most of the 87 studies were cross-sectional and utilized convenience samples of patients as both cases and controls. A response rate was explicitly stated in only 11 (13%) studies. Less than half of the studies controlled for potential confounding through restriction or in the analysis. Most sufficient-quality studies were conducted in older populations (mean age in one or more analysis group > 50 yrs). In sufficient-quality articles, 82% demonstrated at least one statistically significant association between the MSD(s) and biomarker(s) studied. Evidence suggested that: (a) the collagen repair marker TIMP-1 is decreased in fibroproliferative disorders, (b) 5-HT (serotonin) is increased in trapezius myalgia, and (c) triglycerides are increased in a variety of MSDs. Only five studies showed an association between a biochemical marker and MSD severity.

Discussion. While some MSD biomarkers were identified, limitations in the articles examined included possible selection bias, confounding, spectrum effect (potentially heterogeneous biomarker associations in populations according to symptom severity or duration) and insufficient attention to co-morbid conditions. A list of recommendations for future studies is provided.

Background

Little is known about the association of objectively measured temporal patterns of sitting (i.e., how sitting is distributed across time) with obesity indicators. We aimed to investigate the extent to which temporal patterns of sitting (time spent in long, moderate and brief uninterrupted sitting periods) are associated with obesity indicators (body mass index (BMI), waist circumference and fat percentage), independently from moderate-vigorous physical activity (MVPA) and total sitting time among blue-collar workers.

Methods

Workers (n=205) wore Actigraph GT3X+ accelerometers on the thigh and trunk for 1-4 working days. The time-line of sitting on working days was computed using the validated Acti4 software. Total sitting time and time spent sitting in brief (≤5 mins), moderate (>5 and ≤30 mins), and long (>30mins) periods were determined for the whole day, and for leisure and work separately. Obesity indicators, i.e. BMI (kg/m2), waist circumference (cm) and fat percentage were objectively measured. Associations between duration of sitting periods and each obesity indicator were determined using linear regression analysis adjusted for several potential confounders including objectively measured MVPA and total sitting time.

Results

Sitting time in brief periods was negatively associated with obesity indicators for the whole day (BMI, P<0.01; fat percentage, P<0.01; waist circumference, P<0.01) and work (BMI, P<0.01; fat percentage, P<0.01; waist circumference, P<0.01), but not for leisure time. Sitting time in long periods was positively associated with obesity indicators for the whole day (waist circumference, P=0.05) and work (waist circumference, P=0.01; BMI, P=0.04), but not for leisure time. Sitting in moderate periods was not associated with obesity indicators for any domain.

Conclusion

Time spent in brief and long periods of sitting during the whole day and at work were inversely associated with obesity indicators when adjusting for MVPA and total sitting time, while sitting during leisure time did not show these associations. Thus, the temporal distribution of sitting seems to influence the relationship between sitting and obesity.

Background: Studies on the association between sitting time and low back pain (LBP) have found contrasting results. This may be due to the lack of objectively measured sitting time or because socioeconomic confounders were not considered in the analysis.

Objectives: To investigate the association between objectively measured sitting time (daily total, and occupational and leisure-time periods) and LBP among blue-collar workers.

Methods: Two-hundred-and-one blue-collar workers wore two accelerometers (GT3X+ Actigraph) for up to four consecutive working days to obtain objective measures of sitting time, estimated via Acti4 software. Workers reported their LBP intensity the past month on a scale from 0 (no pain) to 9 (worst imaginable pain) and were categorized into either low (≤5) or high (>5) LBP intensity groups. In the multivariate-adjusted binary logistic regression analysis, total sitting time, occupational and leisure-time sitting were both modeled as continuous (hours/day) and categorical variables (i.e. low, moderate and high sitting time).

Results: The multivariate logistic regression analysis showed a significant positive association between total sitting time (hours) and high LBP intensity (odds ratio; OR=1.43, 95%CI=1.15-1.77, P=0.01). Similar results were obtained for leisure-time sitting (OR=1.45, 95%CI= 1.10-1.91, P=0.01), and a similar but non-significant trend was obtained for occupational sitting time (OR=1.34, 95%CI 0.99-1.82, P=0.06). In the analysis on categorized sitting time, high sitting time was positively associated with high LBP for total (OR=3.31, 95%CI= 1.18-9.28, P=0.03), leisure (OR=5.31, 95%CI= 1.57-17.90, P=0.01), and occupational (OR=3.26, 95%CI= 0.89-11.98, P=0.08) sitting time, referencing those with low sitting time.

Conclusion: Sitting time is positively associated with LBP intensity among blue-collar workers. Future studies using a prospective design with objective measures of occupational sitting time are recommended.

Considering that adults spend a considerable proportion of their day at work, employment is a key determinant for daily PA. However, specifics of how and under what circumstances occupational PA (OPA) influences total PA, including other PA domains (e.g. leisure time PA, transport), are unclear. Little is also known about OPA patterns in different occupational groups and how OPA patterns can be changed, among for example those who have mostly sedentary occupations. One important issue concerns if working in a standing position and the use of dynamic chairs has any effect on OPA levels, for instance among office workers. This despite the fact that ergonomists advocate sedentary workers to work in a standing position or use an “active sitting” approach using “dynamic” chairs. To be able to give recommendations regarding PA to employees with different OPA, more insight is needed on how to optimally measure OPA. To move the field forward, knowledge should be combined from different disciplines involved in measuring OPA. Therefore, we want to initiate an interdisciplinary discussion on appropriate measurements of OPA. The aim of the symposium is to present a holistic approach to measuring OPA by combining our expertise in the field of PA and health, measurement of PA using objective measures and self-reported measures, ergonomics, occupational health and public health science.

Neck-shoulder pain (NSP) is a highly prevalent musculoskeletal disorder with unclear causes, and effective prevention and treatment require a further understanding of the underlying mechanisms. Aberrant autonomic nervous system (ANS) regulation is a hypothesized causal element in the development and maintenance of chronic muscle pain.

The overall aim of this thesis was to investigate possible differences in ANS regulation between chronic NSP and healthy control (CON) groups using both laboratory assessment and ambulatory monitoring in daily life.

Four papers are included in this thesis, based on data from three groups with chronic NSP. Autonomic responses to laboratory stressors were assessed using heart rate variability (HRV), blood pressure, trapezius muscle activity and blood flow measurements (Study І) in NSP and CON. Long-term ambulatory monitoring of HRV, physical activity and perceived symptoms were assessed in Studies ІІ and IV to investigate group differences in real-life conditions. Finally, the effects of a ten-week intervention (using individually adjusted HRV biofeedback) to reinstating ANS balance in subjects with chronic NSP were evaluated using self-reported symptoms and health ratings, as well as autonomic regulation testing (i.e., evaluating HRV at rest and in response to stress) (Study ІІІ).

The main findings from the four studies demonstrated aberrant ANS regulation in the NSP group compared to CON, which was predominantly characterized by diminished parasympathetic cardiac activity during rest and sleep, and altered sympathetic reactivity to laboratory stressors (Studies І, ІІ and IV). Different patterns in physical activity were observed between the NSP and CON groups, with reduced physical activity during leisure time in the NSP group (Studies ІІ and IV). Physical activity was found to be positively associated with HRV. Positive effects of HRV-biofeedback were found on perceived health, including social function, vitality and bodily pain, and improved HRV (Study ІІІ).

In conclusion, imbalanced ANS regulation was demonstrated among persons with chronic NSP at both the systemic and local levels. Diminished parasympathetic activity in NSP was modulated by lower levels of physical activity in leisure time. Interventions targeting ANS functions might benefit persons with chronic NSP.

Objective

Leisure-time physical activity (LTPA) has considerable benefits for cardiovascular health and longevity, while occupational physical activity (OPA) is associated with an elevated cardiovascular risk. This “health paradox” may be explained by different effects on the autonomic nervous system from OPA and LTPA. Thus, we aimed to investigate whether objectively measured OPA and LTPA are differentially associated with autonomic regulation among workers.

Methods

The study comprised 514 blue-collar workers from the Danish cohort DPHACTO. Physical activity (i.e. walking, climbing stairs, running and cycling) was assessed objectively using accelerometers worn on the thigh, hip and trunk over multiple working days. During this period, a heart rate monitor was used to sample heart period intervals from the ECG signal. Heart rate and heart rate variability (HRV) indices were analyzed during nocturnal sleep as markers of autonomic regulation. Multiple regression analysis was used to determine the main effects of OPA and LTPA and their interaction on heart rate and HRV, adjusting for multiple confounders.

Results

Statistically significant interaction was found between OPA and LTPA on heart rate (adjusted p<0.0001) and HRV indices in time (rMSSD, adjusted p = 0.004) and frequency-domains (HF, adjusted p = 0.022; LF, adjusted p = 0.033). The beneficial effect of LTPA on nocturnal heart rate and HRV clearly diminished with higher levels of OPA, and high levels of both OPA and LTPA had a detrimental effect.

Conclusion

We found contrasting associations for objectively measured OPA and LTPA with heart rate and HRV during sleep. Differential effects of OPA and LTPA on autonomic regulation may contribute to the physical activity health paradox.

Objectives

This study aimed to determine the extent to which objectively measured sitting time at work is associated with the course of neck-shoulder pain across one year in blue-collar workers.

Methods

Data was analyzed from 625 blue-collar workers in the Danish DPHACTO cohort study (2012-2013). Objective data on sitting time were collected at baseline using accelerometry. Self-reported pain intensity (numeric rating scale 0-10) in the neck-shoulder region was registered for one year using repeated text messages (14 in total). Linear Mixed Models were used to determine the relationship between percent time in sitting at work and trajectories of neck-shoulder pain, with and without adjustment for demographic, occupational and lifestyle factors, and baseline pain intensity.

Results

More sitting time at work was associated with a faster decline in pain intensity over 12-months, as indicated by a statistically significant effect of sitting on pain trajectories in the crude (p=0.020) and fully adjusted models (p=0.027).

Conclusion                             

In blue-collar workers, more sitting time at work was associated with a favorable development of pain intensity over time. The relationship between sitting at work and pain needs further investigation before explicit recommendations and guidelines on sedentary behavior among blue-collar workers can be developed.

Objectives Prolonged sitting has been suggested as a risk factor for neck-shoulder pain (NSP). Using a cross-sectional design, we investigated the extent to which objectively measured time sitting is associated with NSP among blue-collar workers.

Methods Sitting time was measured during multiple working days on male (n=118) and female (n=84) blue-collar workers (n=202) using tri-axial accelerometers (Actigraph) placed on the thigh and trunk. Workers were categorized into having, on average, a low, moderate, or high sitting time, with mean values (SD between subjects) of 4.9 (1.0), 7.3 (0.5), and 9.6 (1.1) hours in total per day. Workers rated their largest NSP intensity during the previous month on a numerical scale (0-9), and were subsequently dichotomized into a low and high NSP intensity group (ratings 0-4 and >4, respectively). Logistic regression analyses adjusted for several individual and work-related factors were used to investigate the association between average sitting time per day (work, leisure and total) and NSP intensity.   

Results For total sitting time, workers in the high sitting category were more likely (adjusted OR 2.97, CI 1.25-7.03) to report high NSP intensity than those who sat moderately (reference category). Low sitting during work was associated with a reduced NSP intensity, but only for males (adjusted OR 0.26 CI 0.07-0.96). No significant association was found between sitting during leisure and NSP intensity.

Conclusion These findings suggest an association between sitting time, in total per day and specifically during work, and NSP intensity among blue-collar workers. We encourage studying the structure and explanation of this association further in prospective studies on larger populations.

Introduction

Prolonged occupational sitting has been suggested to be a risk factor for neck-shoulder pain (NSP). However, studies using valid and precise methods for assessing sitting are lacking. We investigated the extent to which objectively measured sitting time is associated with intense NSP among blue-collar workers.

Methods

In a cross-sectional study, sitting time was measured for two working days on male (n=118) and female (n=84) blue-collar workers using tri-axial accelerometers (Actigraph) placed on the thigh and trunk. Workers were categorized in tertiles having low, moderate, or high sitting time at work. Workers rated their NSP intensity during the previous month on a numerical scale (0-9), and were then dichotomized into a low (0-4) and high (>4) NSP intensity group. Binary logistic regression analyses, with multiple adjustments for individual and occupational risk factors besides sitting, were performed to investigate the association between occupational sitting time and intense NSP, separately for males and females.  

Results

We found that low occupational sitting was associated with a reduced NSP intensity compared to moderate sitting among males (OR 0.28, 95%CI 0.08-0.98). This association remained significant after adjustment for individual and occupational covariates (adjusted OR 0.26, 95%CI 0.07-0.96). We found no such relationship among females (OR 1.01, 95%CI 0.28-3.59), and high sitting was not associated with pain.

Conclusion

Our findings suggest a gender-specific association between occupational sitting time and intense NSP among blue-collar workers. We encourage further studies to investigate the nature of this association, using prospective designs in larger, gender-stratified populations.

Introduction

Previous studies have found substantial differences in the health effects of occupational (OPA) and leisure time physical activity (LTPA): LTPA is generally beneficial to health, while OPA may be detrimental. Why these differences occur is, however, so far not clear. Different time patterns of OPA and LTPA may be an explanation. Thus, we aimed to investigate the extent to which time patterns of OPA and LTPA differ in a population of blue-collar workers.

Methods

This study was conducted on a cross-sectional sample of 191 blue-collar workers from seven workplaces in Denmark. Physical activity and sedentary behavior were estimated using the Acti4 method on recordings from accelerometers (Actigraph GT3X+) worn on the thigh and trunk for four consecutive days. Time patterns of OPA and LTPA were retrieved separately for work and leisure using Exposure Variation Analysis (EVA), and expressed in terms of percentage time spent in uninterrupted periods of different durations (<1min, 1-5 min, 5-10 min, 10-30 min, 30-60 min and > 60 min) of sitting, standing, and walking. Differences between OPA and LTPA in selected EVA derivatives were tested using repeated measures ANOVA with adjustments for differences between work and leisure in total time for each activity.

Results

We found significant differences between work and leisure time for several EVA derivatives, with OPA showing a larger percentage time walking and standing in short periods (<5 min), and less percent time in prolonged sitting (>30 min) than LTPA. Apart from standing (p=.10), these differences remained significant even after adjusting for the difference between work and leisure in total time spent in each activity.

Conclusion

We found, among blue-collar workers, that the time patterns of OPA and LTPA were markedly different even after adjustment for total PA time. We suggest using EVA derivatives in future studies investigating potential associations of OPA and LTPA with health outcomes.

OBJECTIVES: Neck-shoulder pain (NSP) is a common work-related musculoskeletal disorder with unclear mechanisms. Changes in physical activity and autonomic nervous system regulation may be involved in the pathogenesis of chronic NSP. The aim of the current study was to investigate autonomic regulation in relation to physical activity and perceived symptoms during work and leisure time among workers with chronic NSP (n = 29) as compared to a healthy control group (CON, n = 27).

METHODS: Physical activity was objectively monitored for 7 days using accelerometry. Beat-to-beat heart rate was collected continuously for 72 h, with simultaneous momentary ratings of pain, stress, and fatigue. Duration of sitting/lying, standing and walking, number of steps, and energy expenditure were used as measures of physical activity. Heart rate variability (HRV) indices were extracted in time and frequency domains as reflecting autonomic regulation. Data were divided into work hours, leisure time, and sleep.

RESULTS: The NSP group rated higher levels of stress and fatigue at work and leisure, and reduced sleep quality as compared to CON. Elevated heart rate and reduced HRV were found in NSP compared with CON, especially during sleep. The NSP group demonstrated a different pattern of physical activity than CON, with a lower activity level in leisure time. Higher physical activity was associated with increased HRV in both groups.

CONCLUSION: Changes in HRV reflected an autonomic imbalance in workers with chronic musculoskeletal pain. This can be explained by reduced physical activity in leisure time. Intervention studies aimed at increasing physical activity may shed further light on the association between autonomic regulation and physical activity in work-related NSP.

Background. Previous studies suggest that prolonged sitting at work is a risk-factor for neck-shoulder pain (NSP). However, a majority of studies on the association between occupational sitting and NSP have relied on cross-sectional designs and self-reported measurements of sitting time. Our aim was to determine the extent to which occupational sitting time, assessed using accelerometry, is associated with the 1-year time course of NSP intensity among blue-collar workers.

Methods. Our study included 494 Danish workers (female n=220) from three occupational sectors: cleaning (n=96), manufacturing (n=356) and transportation (n=42). At baseline, sitting was monitored continuously for several working days (mean (SD) wear time: 2.6 (0.9) days) using accelerometers attached to the thigh and trunk. During the following 12 months, data on self-reported NSP intensity (NRS scale, range 0-10) were collected on a monthly basis using SMS tracking. Repeated measures ANOVA adjusted for gender, occupational sector, seniority, and pain at baseline was used to examine the association between per cent time spent sitting (at work and leisure) and changes in NSP across time.

Results. We found a significant interaction between occupational sitting at baseline and the time course of NSP (F(11,491)=6.37, p=0.01), which remained significant with adjustment for covariates (F(11,464)=6.64, p=0.01). We found no main effect of occupational sitting on NSP (p>0.05). Categorizing sitting time revealed that more sitting at work was accompanied by larger reductions in NSP over time. The effect of time on NSP was stronger in the high sitting group (F(11,162)=30.4, p<0.0001) than in the low (F(11,162)=4.9, p=0.05) and moderate (F(11,167)=5.10, p=0.02) sitting groups. We found no association between leisure-time sitting and NSP (p>0.05).

Discussion. In contrast to previous studies, our results indicate that prolonged sitting is associated with a favourable prognosis of NSP across one year in workers. The clinical significance of this result needs to be examined further

Objective

The aim of this randomized controlled trial (RCT) was to determine whether aerobic exercise during work hours affects cardiac autonomic regulation in cleaners characterized by high levels of occupational physical activity and poor cardiorespiratory fitness.

Method

Eligible cleaners (n=116) were randomized to an aerobic exercise group (n=59) or a reference group (n=57) with lectures. The intervention group received two 30-min sessions per week of supervised aerobic exercise over 4 months. Diurnal measurements of heart rate variability (HRV) and physical activity (accelerometry) were obtained at baseline and at 4-month follow-up. Time and frequency domain indices of HRV were derived during work, leisure time and sleep to evaluate cardiac autonomic regulation. Linear mixed models were used to determine the effect of the intervention on HRV indices, with adjustment for age, gender and daily use of antihypertensive and/or heart medication.

Results

Compared with the reference group, the exercise group increased all HRV indices apart from a reduction in LF/HF ratio from baseline to follow-up both during work (p<0.05) and leisure (p<0.05). In contrast, during sleep, the HRV indices tended to decrease in the exercise group compared with the reference group from baseline to follow-up, being significant for the HF spectral component (p=0.03).

Conclusion

Among cleaners, a worksite aerobic exercise intervention improved cardiac autonomic regulation during work and leisure, but not during sleep. The health effect of this contrasting change in autonomic regulation needs further investigation.

Syfte

Kunskapen om vilka faktorer som påverkar förloppet av smärta i nacke/skuldra hos personer med manuella arbeten är mycket begränsad. Syftet med föreliggande prospektiva studie var att undersöka sambandet mellan objektivt registrerad fysisk aktivitet på arbetet och fritiden med förloppet av smärta över ett år hos kvinnor och män med manuellt arbete.

Metod

Data samlades in från 625 arbetare inom industri, städning och transport sektorerna från den Danska kohorten DPHACTO. Fysisk aktivitet mättes objektivt vid baslinje med 4 accelerometrar (Actigraph GT3X+) under 1-5 arbetsdagar. Mjukvaran Acti4 användes för att klassificera olika typer av fysisk aktivitet (gå, gå i trapport, cykla, springa). Andel tid i fysisk aktivitet beräknades separat för arbete och fritid. Textmeddelanden (SMS) med frågor om smärtintensitet i nacke/skuldra (skala 0-10) sändes ut till deltagarna med fyra veckors intervall under 12 månader. Linear mixed models användes för att fastställa samband mellan fysisk aktivitet på arbete och fritid med nivå och förändring av smärta över tid, med justering för potentiella konfounders.

Resultat

Fysisk aktivitet på arbetet var inte associerat med genomsnittlig smärtnivå, men fysisk aktivitet på fritiden var associerat med lägre smärta både hos kvinnor (B=-0.71, 95 % CI -1.31‒-0.11) och män (B=-0.85, 95 % CI -1.57‒-0.13). Vi fann en signifikant interaktion mellan fysisk aktivitet och kön på förändring av smärta. Fysisk aktivitet på arbetet var relaterat till långsammare återhämtning av smärta hos män (B=0.03, 95 % CI 0.01‒0.05), medan fysisk aktivitet på fritiden var associerat med långsammare återhämtning hos kvinnor.

Slutsatser

Resultaten indikerar att fysisk aktivitet på fritiden har en skyddande effekt på smärta i nacke/skuldra hos personer med manuellt arbete. Betydelsen av fysisk aktivitet på arbetet och fritiden för återhämtning av smärta tycks skilja sig mellan kvinnor och män, vilket kan bero på skillnader i exponering, vila och återhämtning. 

The aim of the present study was to investigate reactions in trapezius muscle blood flow (MBF), muscle activity, heart rate variability (HRV) and systemic blood pressure (BP) to autonomic tests in subjects with chronic neck-shoulder pain and healthy controls. Changes in muscle activity and blood flow due to stress and unfavourable muscle loads are known underlying factors of work-related muscle pain. Aberration of the autonomic nervous system (ANS) is considered a possible mechanism. In the present study, participants (n = 23 Pain, n = 22 Control) performed autonomic tests which included a resting condition, static hand grip test (HGT) at 30% of maximal voluntary contraction, a cold pressor test (CPT) and a deep breathing test (DBT). HRV was analysed in time and frequency domains. MBF and muscle activity were recorded from the upper trapezius muscles using photoplethysmography and electromyography (EMG). The pain group showed reduced low frequency-HRV (LF) and SDNN during rest, as well as a blunted BP response and increased LF-HRV during HGT (∆systolic 22 mm Hg; ∆LF(nu) 27%) compared with controls (∆systolic 27; ∆LF(nu) 6%). Locally, the pain group had attenuated trapezius MBF in response to HGT (Pain 122% Control 140%) with elevated trapezius EMG following HGT and during CPT. In conclusion, only HGT showed differences between groups in systemic BP and HRV and alterations in local trapezius MBF and EMG in the pain group. Findings support the hypothesis of ANS involvement at systemic and local levels in chronic neck-shoulder pain.

The aim of the study was to investigate autonomic nervous system regulation, physical activity (PA) and perceived stress and energy during daily activities in subjects with chronic muscle pain in the neck-shoulders (trapezius myalgia) (n = 23) and symptom-free controls (n = 22). Subjects underwent 24-h objective ambulatory monitoring of heart rate variability (HRV) and PA, and reported their perceived stress and energy in a diary. Standard HRV measures were extracted in time and frequency domains. The volume and pattern of different types of activities were quantified in terms of intensity and duration of walking, and time spent sitting, standing and lying during the 24-h measurement. Results showed shortened inter beat-intervals (higher heart rate) and reduced HRV in the pain group, most pronounced during sleep (p < 0.05). For overall PA, the pain group showed increased lying time, compared to controls (p < 0.05). A different activity pattern was found in the pain group, with reduced leisure time PA and increased PA during morning hours, in comparison with controls (p < 0.05). Both groups demonstrated low levels of perceived stress, whereas reduced energy was observed in the pain group (p < 0.05). In conclusion, monitoring of 24-h HRV demonstrated diminished HRV among persons with chronic neck-shoulder pain. This reflected aberration in autonomic regulation, suggesting reduced parasympathetic activation and increased sympathetic tone as an element in maintenance of chronic muscle pain.

Purposes

Neck-shoulder pain (NSP) is a common work-related musculoskeletal disorder (1). The autonomic nervous system (ANS) is a potential element in the pathogenesis of regional muscle pain (2). Altered cardiovascular regulation has been observed in chronic NSP at rest and in response to stressors (3, 4). Importantly, the ANS control of the cardiovascular system is strongly influenced by daily physical activity. Thus, the observed aberrations in ANS regulation in chronic NSP may be due to pain-related changes in daily physical activity. The present study aimed at investigating ANS regulation and physical activity in workers with chronic NSP (N = 29) and symptom-free controls (N = 27) during work and leisure time.

Methods

Ambulatory monitoring of physical activity (seven days) and ANS cardiac activity (72-hours) were performed using accelerometry and electrocardiography, respectively. Time walking, sitting/lying and standing, as well as number of steps were calculated for each hour and averaged for work and leisure time. Heart rate variability indices were calculated in both time and frequency domains, and averaged over work, leisure time and sleep.

Results

The results indicated a reduced level of leisure time physical activity in NSP compared to controls (p<0.05), while no differences were observed for sedentary time. NSP demonstrated diminished HRV during sleep (p<0.05). Positive correlations were found between leisure time physical activity and HRV during sleep (p<0.05).

Conclusions

Reduced leisure time physical activity and diminished nocturnal HRV were seen in persons with chronic muscle pain. Correlations between leisure time physical activity and HRV may indicate that ANS regulation was partly modulated by physical activity in leisure time

INTRODUCTION:

Musculoskeletal pain is highly common among the working population. It has been assumed that chronic pain may reduce the activity level in daily life, which in turn may aggravate pain and associated symptoms. However, it is not known whether pain impacts on daily activities among workers. Commonly accepted and validated protocols are needed to gain objective information about possible deviations in physical activity patterns in subjects with chronic musculoskeletal pain.

PURPOSE:

The aim of this cross-sectional study was to investigate the volume and time-pattern of daily physical activity in workers with chronic musculoskeletal pain compared with healthy controls.

METHODS:

Twenty-seven workers with chronic muscle pain primarily in the neck-shoulder region, and 27 age- and gender- matched controls participated in the study. Both groups were recruited from the same global manufacturing company within the industrial sector at a site in Sweden. Physical activity and sedentary behaviour were monitored for seven days, both during work and leisure time, using a single tri-axial accelerometer (PAL Technologies Ltd, Glasgow). Time spent walking, standing and sitting/lying and steps were calculated for each hour. The mean metabolic equivalent (MET) was estimated and used as a measure of energy expenditure. The coefficient of variation (CV) between daytime hours was calculated as a measure of variation.

RESULTS:

For overall daily activity, the mean standing time was significantly higher in the pain group (263 min/day) compared with controls (209 min/day) (p=0.04), whereas no difference was found in energy expenditure or sedentary time. The analyses of time patterns revealed lower energy expenditure in the evening and morning hours among those with pain (mean 1.6 MET/h) compared with the control group (mean 1.8 MET/h) (p<0.05). The pain group showed on average a smaller CV in MET (9%) than the control group (11%) (p=0.02), which indicated a reduced variation in physical activity. There were no significant associations between pain intensity and physical activity.

CONCLUSION:

Despite a normal level of total physical activity, workers with chronic musculoskeletal pain had an altered activity pattern in terms of reduced variation and a lower activity level in leisure time.

Aims: This study aimed to investigate the association between objectively measured physical activity at work and leisure and the intensity (mean level and time course) of neck–shoulder pain (NSP) over 12 months among male and female blue collar workers. Methods: Data were obtained from 625 blue collar workers from the Danish cohort DPHACTO. Physical activity was measured objectively at baseline using accelerometers. The percentage of time spent in physical activity (walking, climbing stairs, running and cycling) was calculated for both work and leisure time. Longitudinal data on the intensity of NSP (numerical rating scale 0–10) were collected using text messages every fourth week over 12 months. Linear mixed models were used to investigate the associations between occupational physical activity (OPA) and leisure time physical activity (LTPA) and the trajectories of the intensity of NSP, adjusted for individual, biomechanical and psychosocial factors, and baseline pain. Results: OPA was not associated with the mean intensity of NSP over 12 months. LTPA was negatively associated with the mean intensity of NSP both among men (B=−0.71, 95% CI −1.31 to −0.11) and women (B=−0.85, 95% CI −1.57 to −0.13). Sex interactions on the 12-month trajectories of NSP showed that higher physical activity was associated with a slower reduction in NSP among men for OPA only (B=0.03, 95% CI 0.01-0.05) and women for LTPA only (B=0.05, 95% CI 0.00-0.09). Conclusions: We found that more time in LTPA was associated with a lower overall intensity of NSP over 12 months among blue collar workers. However, depending on sex and domain, high physical activity had an unfavourable effect on the course of NSP over 12 months.

Background

Our aim was to examine the extent to which temporal patterns of sitting during occupational work and during leisure-time, assessed using accelerometry, are associated with intense neck–shoulder pain (NSP) in blue-collar workers.

Methods

The population consisted of 659 Danish blue-collar workers. Accelerometers were attached to the thigh, hip, trunk and upper dominant arm to measure sitting time and physical activity across four consecutive days. Temporal sitting patterns were expressed separately for work and leisure by the proportion of total time spent sitting in brief bursts (0–5 min), moderate (>5–20 min) and prolonged (>20 min) periods. The peak NSP intensity during the previous 3 months was assessed using a numerical rating scale (range 0–10) and dichotomized into a lower (≤4) and higher (>4) NSP score. Logistic regression analyses with multiple adjustments for individual and occupational factors were performed to determine the association between brief, moderate and prolonged sitting periods, and NSP intensity.

Results

Time in brief bursts of occupational sitting was negatively associated with NSP intensity (adjusted OR 0.68, 95 % CI 0.48–0.98), while time in moderate periods of occupational sitting showed a positive association with NSP (adjusted OR 1.32, 95 % CI 1.04–1.69). Time in prolonged periods of occupational sitting was not associated with NSP (adjusted OR 0.78, 95 % CI 0.78–1.09). We found no significant association between brief, moderate or prolonged sitting periods during leisure, and NSP.

Conclusion

Our findings indicate that the association between occupational sitting time and intense NSP among blue-collar workers is sensitive to the temporal pattern of sitting.

Background We determined the extent to which heart rate variability (HRV) responses to daily physical activity differ between subjects with and without chronic neck pain.

Method Twenty-nine subjects (13 women) with chronic neck pain and 27 age- and gender-matched healthy controls participated. Physical activity (accelerometry), HRV (heart rate monitor) and spatial location (Global Positioning System (GPS)) were recorded for 74 hours. GPS data were combined with a diary to identify periods of work, and of leisure at home and elsewhere. Time- and frequency-domain HRV indices were calculated, and stratified by period and activity type (lying/sitting, standing, or walking). ANCOVAs with multiple adjustments were used to disclose possible group differences in HRV.

Results The pain group showed a reduced HRV response to physical activity compared with controls (p=.001), according to the sympathetic-baroreceptor HRV index (LF/HF, ratio between low and high frequency power), even after adjustment for leisure time physical activity, work stress, sleep quality, mental health, and aerobic capacity (p=.02). The parasympathetic response to physical activity did not differ between groups.

Conclusions Relying on long-term monitoring of physical behavior and heart rate variability, we found an aberrant sympathetic-baroreceptor response to daily physical activity among subjects with chronic neck pain.

Background

Leisure time physical activity (LTPA) is generally associated with favorable cardiovascular health outcomes, while occupational physical activity (OPA) shows less clear, or even opposite, cardiovascular effects. This apparent paradox is not sufficiently understood, but differences in temporal patterns of OPA and LTPA have been suggested as one explanation. Our aim was to investigate the extent to which work and leisure (non-occupational time) differ in temporal activity patterns among blue-collar workers, and to assess the modification of these patterns by age and gender.

Methods

This study was conducted on a cross-sectional sample of male (n = 108) and female (n = 83) blue-collar workers, aged between 21 and 65 years. Physical activity and sedentary behavior were assessed using accelerometers (Actigraph GT3X+) worn on the thigh and trunk for four consecutive days. Temporal patterns of OPA and LTPA were retrieved using Exposure Variation Analysis (EVA), and expressed in terms of percentage of work and leisure time spent in uninterrupted periods of different durations (<1 min, 1–5 min, 5–10 min, 10–30 min, 30–60 min and > 60 min) of sitting, standing, and walking. Repeated measures ANOVA and linear regression analyses were used to test a) possible differences between OPA and LTPA in selected EVA derivatives, and b) the modification of these differences by age and gender.

Results

OPA showed a larger percentage time walking in brief (<5 min) periods [mean (SD): 33.4 % (12.2)], and less time in prolonged (>30 min) sitting [7.0 % (9.3)] than LTPA [walking 15.4 % (5.0); sitting 31.9 % (15.3)], even after adjustment for the difference between work and leisure in total time spent in each activity type. These marked differences in the temporal pattern of OPA and LTPA were modified by gender, but not age.

Conclusion

We found that the temporal patterns of OPA and LTPA among blue-collar workers were markedly different even after adjustment for total physical activity time, and that this difference was modified by gender. We recommend using EVA derivatives in future studies striving to disentangle the apparent paradoxical cardiovascular effect of physical activity at work and during leisure.

Background:

Decreased physical activity levels have been found among subjects with work-related musculoskeletal disorders (MSD). Still, little is known about the distribution of physical activity and sedentary behavior over a work day, and whether these patterns differ between work and leisure time. Our aim was to characterize and compare physical activity patterns at work and leisure time (spent at home or elsewhere) among office workers with MSD and asymptomatic controls.

Methods:

Seventeen office workers (11f, 6m; mean age 41(SD=11) years) with neck-shoulder pain, and 17 age- and gender-matched asymptomatic office workers participated. Physical activity and sedentary behavior were monitored continuously for seven days using a single tri-axial accelerometer (ActivPAL). During four consecutive work-days within this period, data from a geographical positioning system (GPS) detector installed on a smartphone was combined with a written diary to identify the location (work place, leisure "at home" and "elsewhere") of the participants. Differences between groups in mean physical activity levels (excluding sleep) stratified by location were analysed with ANOVA. Physical activity patterns were expressed using Exposure Variation Analysis (EVA), showing the percentage of time spent in periods of different durations (<1min, 1-5min, 5-10min, 10-30min, 30-60min, >60min) of sitting/lying, standing, and walking.

Results:

In both groups, the lowest activity levels were found at work. Leisure "elsewhere" showed less %time in long bouts (>30min) of sitting/lying and more %time in walking (5-10 and 10-30 min bouts) compared with "home". Workers with pain did not increase their leisure activity level "elsewhere" compared with "home" to the same extent as controls, which was mainly reflected in a larger %time in prolonged periods (>30 min) of sitting/lying among those with pain.

Conclusion:

The combination of accelerometry and GPS allowed a detailed characterization of physical activity patterns stratified by location among office workers. Some differences were found between workers with and without MSD, which need further investigation as to their effects on health and well-being.

Recent studies focusing on autonomic nervous system (ANS) dysfunctions, together with theoretical pathophysiological models of musculoskeletal disorders, indicate the involvement of ANS regulation in development and maintenance of chronic muscle pain. Research has demonstrated the effectiveness of heart rate variability (HRV) biofeedback (BF) in increasing HRV and reducing the symptoms of different disorders characterized by ANS aberration. The study investigated the effects of resonance frequency HRV BF on autonomic regulation and perceived health, pain, stress and disability in 24 subjects with stress-related chronic neck-shoulder pain. Twelve subjects participated in 10 weekly sessions of resonant HRV BF and were compared to a control group. Subjective reports and HRV measures during relaxation and in response to a standardized stress protocol were assessed for both groups pre- and post-intervention. Group X time interactions revealed a significantly stronger increase over time in perceived health (SF-36) for the treatment group, including vitality, bodily pain and social functioning. Interactions were also seen for HRV during relaxation and reactivity to stress. The present pilot study indicates improvement in perceived health over a 10 week intervention with HRV-biofeedback in subjects with chronic neck-pain. Increased resting HRV as well as enhanced reactivity to hand grip and cold pressor tests might reflect beneficial effects on ANS regulation, and suggest that this intervention protocol is suitable for a larger controlled trial.

Prolonged sitting is associated with increased risk for cardiovascular diseases and mortality. However, research into the physiological determinants underlying this relationship is still in its infancy. The aim of the study was to determine the extent to which occupational and leisure-time sitting are associated with nocturnal heart rate variability (HRV) in blue-collar workers. The study included 138 blue-collar workers (mean age 45.5 (SD 9.4) years). Sitting-time was measured objectively for four days using tri-axial accelerometers (Actigraph GT3X+) worn on the thigh and trunk. During the same period, a heart rate monitor (Actiheart) was used to sample R-R intervals from the electrocardiogram. Time and frequency domain indices of HRV were only derived during nighttime sleep, and used as markers of cardiac autonomic modulation. Regression analyses with multiple adjustments (age, gender, body mass index, smoking, job-seniority, physical work-load, influence at work, and moderate-to-vigorous physical activity) were used to investigate the association between sitting time and nocturnal HRV. We found that occupational sitting-time was negatively associated (p < 0.05) with time and frequency domain HRV indices. Sitting-time explained up to 6% of the variance in HRV, independent of the covariates. Leisure-time sitting was not significantly associated with any HRV indices (p > 0.05). In conclusion, objectively measured occupational sitting-time was associated with reduced nocturnal HRV in blue-collar workers. This indicates an attenuated cardiac autonomic regulation with increasing sitting-time at work regardless of moderate-to-vigorous physical activity. The implications of this association for cardiovascular disease risk warrant further investigation via long-term prospective studies and intervention studies.

Purpose Heart rate variability (HRV) is often monitored in occupational studies as a measure of cardiac autonomic activation, but the reliability of commonly used HRV indices is poorly understood. In the present study, we determined the variability between and within subjects of common HRV indices during a repetitive low-force occupational task, i.e. pipetting, and interpreted the results in terms of necessary sample sizes in studies comparing HRV between conditions or groups.

Methods Fourteen healthy female subjects performed a standardized pipetting task in the laboratory on three separate days within a short time-span (<2 weeks), and on one additional occasion six months later. A number of standard HRV indices were calculated in both time and frequency domains. For each HRV index, variance components were estimated between subjects, within subjects between occasions far apart in time, and within subjects between days within a two-week period.

Results We found that the time interval between repeated measurements did not influence the extent of HRV variability, and that the reliability of most HRV indices was sufficient for even small study samples (30 subjects or less) to be able to detect, with satisfying power (>0.80), a significant 10% to 20% difference in HRV between groups, and between conditions within individuals.

Conclusions We conclude that HRV can be used as a reliable and feasible marker of autonomic activity in occupational studies of repetitive low-force work.