Physical activities at work and risk of musculoskeletal pain and its consequences: protocol for a study with objective field measures among blue-collar workers

Defining a systems framework for characterizing physical work demands with wearable sensors

Measuring the physical demands of work is important in understanding the relationship between exposure to these job demands and their impact on the safety, health, and well-being of working people. However, work is changing and our knowledge of job demands should also evolve in anticipation of these changes. New opportunities exist for noninvasive long-term measures of physical demands through wearable motion sensors, including inertial measurement units, heart rate monitors, and muscle activity monitors. Inertial measurement units combine accelerometers, gyroscopes, and magnetometers to provide continuous measurement of a segment's motion and the ability to estimate orientation in 3-dimensional space. There is a need for a system-thinking perspective on how and when to apply these wearable sensors within the context of research and practice surrounding the measurement of physical job demands. In this paper, a framework is presented for measuring the physical work demands that can guide designers, researchers, and users to integrate and implement these advanced sensor technologies in a way that is relevant to the decision-making needs for physical demand assessment. We (i) present a literature review of the way physical demands are currently being measured, (ii) present a framework that extends the International Classification of Functioning to guide how technology can measure the facets of work, (iii) provide a background on wearable motion sensing, and (iv) define 3 categories of decision-making that influence the questions that we can ask and measures that are needed. By forming questions within these categories at each level of the framework, this approach encourages thinking about the systems-level problems inherent in the workplace and how they manifest at different scales. Applying this framework provides a systems approach to guide study designs and methodological approaches to study how work is changing and how it impacts worker safety, health, and well-being.

Mapping the conceptual structure of ergonomics, musculoskeletal disorders, treatment and return to work in manual jobs: A systematic review

BACKGROUND

Musculoskeletal disorders constitute one of the major health problems of workers exposed to manual work throughout the world. Nevertheless, there is no study that maps its conceptual structure based on a systematic methodology.

OBJECTIVE

To identify the conceptual structure of ergonomics, MSDs, treatment and return to work in manual jobs in the last 12 years by applying a systematic co-word network analysis methodology which describes the replicability of the search filters and emphasizes the rigor that has to be followed in the creation of the network.

METHODS

The search filter was customized for each bibliographic database, and followed the PRISMA 2020 flowchart for the screening process. For the creation of the network, the titles, abstracts, and keywords were used as the unit of analysis extracting the noun phrases of the first two units. In the normalization process, the terms of the search filter were deleted and their associated terms, and standardized the similar terms. Regarding the plotting of the network, Vosviewer was used applying the network settings based on content analysis.

RESULTS

The co-word network shows three communities: Ergonomic assessment and workplace intervention tools, factors related to rehabilitation and return to work, and physical and mental overload management. For each community, there is a framework that explains the relationship within terms.

CONCLUSION

This study is aligned with the replicability, robustness, and relevance recommendations in the implementation of rigorous scientometric studies. The occupational health community is encouraged to implement scientometric studies following a rigorous methodology and working in interdisciplinary team.

Does it matter for health if steps are taken during work or leisure? A prospective accelerometer study using register-based long-term sickness absence

BACKGROUND

Walking is known to be good for health. However, it is unknown whether it matters if steps are taken during work or leisure. Therefore, we aimed to examine the prospective association between accelerometer-measured steps taken during work or leisure and register-based long-term sickness absence (LTSA).

METHODS

We included 937 blue- and white-collar workers from the PODESA cohort who wore a thigh-based accelerometer over four days to measure number of steps during work and leisure. Steps were divided into domain based on diary data. First event of LTSA was retrieved from a national register with four years' follow-up. We used Cox proportional hazard models to analyze the association between domain-specific and total daily steps and LTSA, adjusted for age, sex, job type, smoking, and steps in the other domain (e.g., work/leisure).

RESULTS

We found more steps at work to be associated with a higher LTSA risk [Hazard Ratio (HR):1.04; 95% CI: 1.00-1.08 per 1000 steps]. No significant association was found between steps during leisure and LTSA (HR: 0.97; 95% CI: 0.91-1.02), nor between total daily steps and LTSA (HR: 1.01; CI 95% 0.99-1.04).

CONCLUSIONS

More steps at work were associated with higher risk of LTSA, while steps during leisure was not clearly associated with LTSA risk. These findings partly support 'the physical activity paradox' stating that the association between physical activity and health depends on the domain.

The Use of Wearable Inertial Sensors and Workplace-Based Exercises to Reduce Lateral Epicondylitis in the Workstation of a Textile Logistics Center

People whose jobs involve repetitive motions of the wrist and forearm can suffer from lateral epicondylitis, which is a significant burden on both the individual and the employer due to treatment costs, reduced productivity, and work absenteeism. This paper describes an ergonomic intervention to reduce lateral epicondylitis in the workstation of a textile logistics center. The intervention includes workplace-based exercise programs, evaluation of risk factors, and movement correction. An injury- and subject-specific score was calculated from the motion captured with wearable inertial sensors at the workplace to evaluate the risk factors of 93 workers. Then, a new working movement was adapted to the workplace, which limited the observed risk factors and took into account the subject-specific physical abilities. The movement was taught to the workers during personalized sessions. The risk factors of 27 workers were evaluated again after the intervention to validate the effectiveness of the movement correction. In addition, active warm-up and stretching programs were introduced as part of the workday to promote muscle endurance and improve resistance to repetitive stress. The present strategy offered good results at low cost, without any physical modification of the workplace and without any detriment to productivity.

Agreement between an expert-rated mini job exposure matrix of occupational biomechanical exposures to the lower body and technical measurements or observation: a method comparison study

OBJECTIVES

Investigating the agreement between an expert-rated mini job exposure matrix (JEM) of lower body exposures and technical measurements of worktime spent standing/walking and observation-based estimates of time spent kneeling/squatting and total load lifted per workday.

METHODS

We chose 16 job titles from the 121 job groups in the lower body JEM and included them in the mini JEM. New expert ratings for the mini JEM were performed by the same five occupational physicians who performed the ratings for the lower body JEM. For each job title and type of exposure, the exposure estimates were a mean of the five independent ratings. Technical measurements of standing/walking for all 16 job titles, and for 8 job titles workplace observations were performed of kneeling/squatting and total load lifted per workday. Data were collected from September to December 2015 and supplemented by data from the NOMAD and DPhacto studies collected between 2011 and 2013. All data were collected in Denmark. Agreement between expert-based and measured/observed lower body exposures by job titles was evaluated using Spearman's rank correlation, Bland-Altman plots evaluated systematic deviations and limits of agreement (LoA).

RESULTS

Standing/walking showed a rank correlation of 0.55, kneeling/squatting 0.83 and total load lifted per workday 0.71. The mini JEM estimates did not systematically deviate from the technical measurements/observations for time spent standing/walking (mean difference 0.20 hours/workday, LoA -1.63, 2.03 hours/workday) and kneeling/squatting (mean difference -0.35 hours/workday, LoA -1.21, 0.51 hours/workday). For total load lifted per workday, the mini JEM systematically overestimated the exposures compared with the observations (mean difference -909 kg/workday, LoA -3000, 1147 kg/workday).

CONCLUSIONS

There was moderate to very high agreement between an expert-rated mini JEM of standing/walking, kneeling/squatting, and lifting exposures and corresponding technical measurements/observations. This method comparison study supports the use of the expert-based lower body JEM in large-scale occupational epidemiological studies.

Physical Activity Advice for Prevention and Rehabilitation of Low Back Pain- Same or Different? A Study on Device-Measured Physical Activity and Register-Based Sickness Absence

Purpose We lack knowledge on whether the advice of "being physically active" should be the same for prevention and rehabilitation of low back pain (LBP). Sickness absence is a key outcome for LBP prevention and rehabilitation. We investigated the associations between physical activity and long-term sickness absence (LTSA) among employees with and without LBP. Methods Between 2011 and 2013, 925 Danish employees wore a Actigraph GTX3 accelerometer for 1-5 workdays to measure physical activity and reported LBP in past 7 days. Employees were followed for 4 years to determine their first register-based LTSA event (≥ 6 consecutive weeks). Results Among employees with LBP, increasing moderate-to-vigorous-intensity physical activity at work by 20 min and decreasing the remaining behaviors at work (ie., sitting, standing and light-intensity activity) by 20 min was associated with 38% (95% CI 17%; 63%) higher LTSA risk. Increasing light-intensity activity at work by 20 min and decreasing 20 min from the remaining behaviors was associated with 18% (95% CI 4%; 30%) lower risk. During leisure, increasing moderate-to-vigorous-intensity activity by 20 min or standing by 40 min was associated with 26% (95% CI 3%; 43%) lower and 37% (95% CI 0%; 87%) higher risk, respectively. Among employees without LBP, we found no such associations. Conclusions The physical activity advice ought to be different for LBP prevention and rehabilitation to reduce LTSA risk, and specified by domain and activity intensity. At work, employees with LBP should be advised to spend time on light-intensity physical activity and limit their time on moderate-to-vigorous-intensity physical activity. During leisure, employees should spend time on moderate-to-vigorous-intensity physical activity.

Intensity of occupational physical activity in blue-collar workers: do self-reported rating and device-worn measurements agree?

PURPOSE

High intensity occupational physical activity (OPA) seem to aggravate health and increase risk of sick leave and early retirement. Most intensity of OPA monitoring has been self-reported, e.g. by rating of perceived exertion (RPE). However, no studies have investigated the precision and risk of bias in RPE reporting during free-living OPA. This study investigated the agreement between OPA intensity in percentage of the heart rate reserve (%HRR) estimated from RPE and device-measured heart rate (HR), and potential bias factors on this agreement.

METHODS

The CR10 scale measured RPE at work. The Actiheart monitor measured HR during 24-h a day for 2-4 days. Both RPE and device-worn HR were converted to %HRR. The difference between both %HRR and their limits of agreement was determined in a Bland Altman plot. To detect bias factors, the difference between both %HRR was regressed on age, sex, cardiorespiratory fitness, occupational lifting, medication, consequences of musculoskeletal disorders and the interactions between these factors with device-work %HRR.

RESULTS

Six hundred and twenty-three participants were included in the analysis. Mean difference between RPE-based and device-worn %HRR was 54.6% (SD 19.5). The limits of agreement were wide (11.6-90.1%HRR). Age (0.48%HRR, 95% CI 0.18-0.79) occupational lifting (9.84%HRR, 95% CI 3.85-15.83) and cardiorespiratory fitness (0.41%HRR, 95% CI 0.03-0.79) significantly biased the agreement between the estimations of OPA intensity.

CONCLUSION

RPE overestimated OPA intensity, and was biased by several factors. Device-worn %HRR should be preferred when evaluating OPA intensity among workers with physically demanding jobs.

Physical work conditions and perceived health problems among informal automobile artisans

BACKGROUND:

Automobile car repair requires intensive activities. Several studies have described different work characteristics of automobile artisans’ work. However, the effects of physical work conditions (PWC) on worker health outcomes are largely unknown.

OBJECTIVE:

This study aimed to explore which of the PWC have high negative impact on worker’s health outcomes, and whether the same conditions affected both illnesses and injuries.

METHODS:

A cross-sectional design and a multistage method were used to randomly select 632 workers. A structured self-reported questionnaire was used to obtain information on dependent variables (illness/injuries) and independent variables (PWC). The results were analysed using the chi-square test and logistic regression analysis, while controlling for occupation.

RESULTS:

Workers who manually lifted heavy items or orally sucked petrol regularly reported illnesses and injuries. Long work experience and long working hours were significantly associated with illness, whereas prolonged standing was significantly related to injuries. Contrary to our initial expectation, workers who regularly worked at 2 m or higher above the ground level tended to report less illness and injury.

CONCLUSIONS:

PWCs were more significantly related to work-related illnesses than injuries. Therefore, interventional programs for automobile artisans should focus on the PWC that increase worker vulnerability to work-related illnesses.

The elixir of muscle activity and kinesiology in a health perspective: Evidence of worksite tailored exercise training alleviating muscle disorders

Physical activity is known to benefit health while muscle activation and movements performed during occupational work in contrast may result in work-related musculoskeletal disorders. Therefore, we posed the research question: which mode of muscle activation may result in a reversal of work-related disorders? To address this, we performed electromyographic (EMG) and kinematic assessments of workers with diverse exposure categories: sedentary monotonous work, prolonged walking/standing, and physically heavy work. The various job-specific exposure variables could be categorized in terms of duration, intensity, repetition, static component, peak force etc. that were subsequently identified as risk factors. Based on sports science principles we developed tailored exercise programs to counteract job exposure. EMG activity during exercise training was monitored to identify principal differences between exercise training and job patterns. Evidence from more than 20 RCT studies including >4000 workers showed positive effects such as decreased muscle pain and increased workability. Finally, we identified plausible underlying mechanisms in muscle tissue - human and animal - that confirmed metabolic, morphological, and hormonal changes with e.g. repetitive work that were reversal to adaptations reported with exercise training. Progress has been made in developing intelligent physical exercise training, IPET, as the best complementary activity to job exposure and includes muscle activations and movements that limit work-related inactivity atrophy as well as overload injury.

Cardiorespiratory Fitness in Occupational Groups-Trends over 20 Years and Future Forecasts

BACKGROUND

Reports have indicated a negative trend in cardiorespiratory fitness (CRF) in the general population. However, trends in relation to different occupational groups are missing. Therefore, the aim of our study was to examine the trends in CRF during the last 20 years, and to provide a prognosis of future trends in CRF, in different occupational groups of Swedish workers.

METHODS

Data from 516,122 health profile assessments performed between 2001 to 2020 were included. CRF was assessed as maximal oxygen consumption and was estimated from a submaximal cycling test. Analyses include CRF as a weighted average, standardized proportions with low CRF (<32 mL/min/kg), adjusted annual change in CRF, and forecasting of future trends in CRF.

RESULTS

There was a decrease in CRF over the study period, with the largest decrease in both absolute and relative CRF seen for individuals working in administrative and customer service (-10.1% and -9.4%) and mechanical manufacturing (-6.5% and -7.8%) occupations. The greatest annual decrease was seen in transport occupations (-1.62 mL/min/kg, 95% CI -0.190 to -0.134). Men and younger individuals had in generally a more pronounced decrease in CRF. The proportion with a low CRF increased, with the greatest increase noted for blue-collar and low-skilled occupations (range: +19% to +27% relative change). The forecast analyses predicted a continuing downward trend of CRF.

CONCLUSION

CRF has declined in most occupational groups in Sweden over the last two decades, with a more pronounced decline in blue-collar and low-skilled occupational groups.

Day-to-day pattern of work and leisure time physical behaviours: are low socioeconomic status adults couch potatoes or work warriors?

Background

Most studies on day-to-day patterns of physical behaviours (i.e. physical activities and sedentary behaviour) are based on adults with high socioeconomic status (SES) and without differentiating between work and leisure time. Thus, we aimed to characterise the day-to-day leisure time physical behaviours patterns among low SES adults and investigate the influence of work physical behaviours.

Methods

This cross-sectional study included 963 adults from low SES occupations (e.g. manufacturing, cleaning and transportation). The participants wore accelerometers for 1–7 days to measure physical behaviours during work and leisure time, expressed as time-use compositions consisting of time spent sedentary, standing or being active (walking, running, stair climbing, or cycling). Compositional multivariate multilevel models were used to regress daily leisure time-use composition against work time-use compositions. Interaction between weekday and (1) type of day, (i.e., work/non-work) and (2) the work time-use composition were tested. Compositional isotemporal substitution was used to interpret the estimates from the models.

Results

Each weekday, workers consistently spent most leisure time being sedentary and most work time standing. Leisure time physical behaviours were associated with type of day (p < 0.005, more sedentary on workdays vs. non-workdays), weekday (p < 0.005, more sedentary on Friday, Saturday and Sunday), standing work (p < 0.005, more sedentary and less standing and active leisure time on Sunday), and active work (p < 0.005, less sedentary and more standing and active leisure time on Sunday). Sedentary leisure time increased by 18 min, while standing and active leisure time decreased by 11 and 7 min, respectively, when 30 min were reallocated to standing at work on Sunday. Conversely, sedentary leisure time decreased by 25 min, and standing and active leisure time increased by 15 and 10 min, respectively, when 30 min were reallocated to active time at work on Sunday.

Conclusions

While low SES adults’ leisure time was mostly sedentary, their work time was predominantly standing. Work physical behaviours differently influenced day-to-day leisure time behaviours. Thus, public health initiatives aiming to change leisure time behaviours among low SES adults should consider the influence of work physical behaviours.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-11409-0.

Number of steps and systolic blood pressure: Do work and leisure matter?

The number of steps per day influences blood pressure and health. However, the association between steps at work and leisure and blood pressure is unknown. Thus, we aimed to investigate the association between the domain‐specific number of steps and systolic blood pressure. A thigh‐worn accelerometer was used to measure the steps of 694 workers over 1–5 consecutive days, separated into work and leisure domains using a self‐reported diary. We linearly regressed steps at work, leisure and total day against systolic blood pressure, adjusting for age, sex, body mass index, smoking, and antihypertensive medication. Additionally, we stratified the analyses on job type (blue‐collar or white‐collar). The results of this cross‐sectional analysis indicated a beneficial association between the number of steps (per 2000‐step interval) and systolic blood pressure for the total day (−0.5 mmHg; −1.0 to −0.8, 95% CI, p < 0.05) and work (−0.9 mmHg; −1.5 to −0.4, 95% CI, p < 0.05), but not for leisure (+0.1 mmHg; −0.7 to 0.9, 95% CI, p = 0.75). Blue‐collar workers took almost twice as many steps at work (9143 ± SD3837) as white‐collar workers (5863 ± SD3565) and, after stratification on job type, we observed a beneficial association between the number of steps at work and systolic blood pressure among blue‐collar workers (−1.1 mmHg; −1.7 to −0.4, 95% CI, p < 0.05), but not for white‐collar workers (−0.3 mmHg; −1.7 to 1.1, 95% CI, p = 0.7). These findings indicate that the number of steps at work, particularly among blue‐collar workers, is beneficially associated with systolic blood pressure. Such findings support the potential of work (re)design to promote walking to improve blood pressure.

Heart rate during work and heart rate variability during the following night: a day-by-day investigation on the physical activity paradox among blue-collar workers

Objectives:

Contrary to leisure-time physical activity, occupational physical activity (OPA) may have harmful health effects, called the physical activity paradox. A proposed mechanism is that OPA can elevate the heart rate (HR) for several hours per day. We aimed to investigate the association between the mean intensity of OPA and HR variability (HRV) indices the following night.

Methods:

Three cohorts (NOMAD, DPhacto, and Physical Workload and Fitness) involving blue-collar workers from different sectors were merged in this study. HR monitors (Actiheart) recorded 24-hour inter-beat intervals (IBI) for up to four consecutive days. The relative intensity of the mean HR during work was estimated by HR reserve (%HRR), and time-domain indices of HRV were analyzed during the following night. Data were analyzed using a multilevel growth model to test the association between mean %HRR during work and HRV indices at night in a day-by-day analysis adjusted for age, BMI, alcohol consumption, smoking, and occupation.

Results:

The dataset included a sample of 878 Danish blue-collar workers, with a mean %HRR during work of 31%, and 42% worked at an intensity ≥30%HRR. The multilevel model showed negative within- and between-subject associations between %HRR during work and HRV indices at night.

Conclusions:

Our results indicate a higher %HRR during work to associate with lower HRV indices the following night and a higher HR, reflecting an imbalanced autonomic cardiac modulation. This finding supports a high mean HR during work to be a potential underlying mechanism for the harmful health effect of OPA.

Automatically Determining Lumbar Load during Physically Demanding Work: A Validation Study

A sensor-based system using inertial magnetic measurement units and surface electromyography is suitable for objectively and automatically monitoring the lumbar load during physically demanding work. The validity and usability of this system in the uncontrolled real-life working environment of physically active workers are still unknown. The objective of this study was to test the discriminant validity of an artificial neural network-based method for load assessment during actual work. Nine physically active workers performed work-related tasks while wearing the sensor system. The main measure representing lumbar load was the net moment around the L5/S1 intervertebral body, estimated using a method that was based on artificial neural network and perceived workload. The mean differences (MDs) were tested using a paired t-test. During heavy tasks, the net moment (MD = 64.3 ± 13.5%, p = 0.028) and the perceived workload (MD = 5.1 ± 2.1, p < 0.001) observed were significantly higher than during the light tasks. The lumbar load had significantly higher variances during the dynamic tasks (MD = 33.5 ± 36.8%, p = 0.026) and the perceived workload was significantly higher (MD = 2.2 ± 1.5, p = 0.002) than during static tasks. It was concluded that the validity of this sensor-based system was supported because the differences in the lumbar load were consistent with the perceived intensity levels and character of the work tasks.

Work-Time Compositions of Physical Behaviors and Trajectories of Sick Leave Due to Musculoskeletal Pain

We aimed to investigate the association between work-time compositions of physical behavior and sick leave trajectories due to musculoskeletal pain over one year. We conducted a secondary analysis using the data of 981 workers in a Danish prospective cohort (DPHACTO 2012–2014). At baseline, we assessed physical behaviors (sitting, standing, light physical activity (LIPA), and moderate-to-vigorous physical activity (MVPA)) at work and during leisure, using accelerometers. Over 1 year follow-up, workers reported sick-leave days due to musculoskeletal pain at 4-week intervals. Four distinct trajectories of sick leave were previously identified in this cohort (“no sick leave”, “few days—increasing trajectory”, “some days—decreasing trajectory”, “some days—increasing trajectory”), and used as an outcome in multinomial regression models with work-time compositions as predictors, adjusted for compositions of behavior during leisure, age, sex, body mass index, and smoking habits. More time spent sitting relative to the other behaviors was negatively associated with the trajectory of few days—increasing sick leave (p = 0.004), while time in LIPA was positively associated with the trajectory of some days—increasing sick leave (p = 0.009). Standing and MVPA were not significantly associated with sick leave trajectories. In conclusion, work-time compositions with more sitting relative to the other behaviors had lower risk for an increasing trajectory of sick leave due to pain, while compositions with more LIPA had higher risk. This may have implications for prevention of pain-related sick leave in blue-collar workers.

Accelerometer-Measured Physical Activity at Work and Need for Recovery: A Compositional Analysis of Cross-sectional Data

Objectives

Previous research has shown strong associations between occupational physical activity (OPA) and need for recovery (NFR). However this research has only utilized self-reported measures of OPA which may be biased. Thus, there is a need for investigating if the previously documented association between self-reported OPA and NFR can be found when using technical measures of OPA. There is also the need to investigate whether older workers are particularly susceptible to increased NFR, since age-related declines in physical capacity mean that it is likely these workers will have a higher NFR for a given physical activity. The aim of this study was to investigate the association between technically measured OPA and NFR, and whether this relationship is modified by age.

Methods

This study utilized data from the Danish Physical Activity Cohort with Objective Measurements cohort—comprising Danish workers (n = 840) from the cleaning, manufacturing, and transportation sectors. OPA was measured by accelerometers attached to the thigh and upper back for at least one work day and classified into four physical behaviour categories (sedentary, standing, light, or moderate/vigorous). NFR was measured using a shortened version of the Danish NFR scale. Analysis was conducted using linear regression and isotemporal substitution analyses for compositional data.

Results

The overall association between OPA and NFR was statistically significant in the unadjusted model (P < 0.001), but not when adjusted for age, sex, occupation, and shift work (P = 0.166). Isotemporal substitution showed small but significant reductions in NFR when increasing sedentary time relative to other behaviours (adjusted: ΔNFR = −0.010 [−0.019; −0.001]). There were no significant interactions between age and OPA (P = 0.409).

Conclusions

This study found significant associations between OPA and NFR, but the effect sizes were small. Reallocating 30 min to sedentary behaviours from other behaviours was associated with a reduced NFR, but the effect size may not be practically relevant. Moreover, no clear modifying effects of age were identified.

Zero problems with compositional data of physical behaviors: a comparison of three zero replacement methods

BACKGROUND

Researchers applying compositional data analysis to time-use data (e.g., time spent in physical behaviors) often face the problem of zeros, that is, recordings of zero time spent in any of the studied behaviors. Zeros hinder the application of compositional data analysis because the analysis is based on log-ratios. One way to overcome this challenge is to replace the zeros with sensible small values. The aim of this study was to compare the performance of three existing replacement methods used within physical behavior time-use epidemiology: simple replacement, multiplicative replacement, and log-ratio expectation-maximization (lrEM) algorithm. Moreover, we assessed the consequence of choosing replacement values higher than the lowest observed value for a given behavior.

METHOD

Using a complete dataset based on accelerometer data from 1310 Danish adults as reference, multiple datasets were simulated across six scenarios of zeros (5-30% zeros in 5% increments). Moreover, four examples were produced based on real data, in which, 10 and 20% zeros were imposed and replaced using a replacement value of 0.5 min, 65% of the observation threshold, or an estimated value below the observation threshold. For the simulation study and the examples, the zeros were replaced using the three replacement methods and the degree of distortion introduced was assessed by comparison with the complete dataset.

RESULTS

The lrEM method outperformed the other replacement methods as it had the smallest influence on the structure of relative variation of the datasets. Both the simple and multiplicative replacements introduced higher distortion, particularly in scenarios with more than 10% zeros; although the latter, like the lrEM, does preserve the ratios between behaviors with no zeros. The examples revealed that replacing zeros with a value higher than the observation threshold severely affected the structure of relative variation.

CONCLUSIONS

Given our findings, we encourage the use of replacement methods that preserve the relative structure of physical behavior data, as achieved by the multiplicative and lrEM replacements, and to avoid simple replacement. Moreover, we do not recommend replacing zeros with values higher than the lowest observed value for a behavior.

The physical activity paradox revisited: a prospective study on compositional accelerometer data and long-term sickness absence

Background

The ‘physical activity paradox’ advocates that leisure physical activity (PA) promotes health while high occupational PA impairs health. However, this paradox can be explained by methodological limitations of the previous studies—self-reported PA measures, insufficient adjustment for socioeconomic confounding or not addressing the compositional nature of PA. Therefore, this study investigated if we still observe the PA paradox in relation to long-term sick absence (LTSA) after adjusting for the abovementioned limitations.

Methods

Time spent on moderate-to-vigorous physical activity (MVPA) and remaining physical behaviors (sedentary behavior, standing, light PA and time in bed) at work and in leisure was measured for 929 workers using thigh accelerometry and expressed as isometric log-ratios (ilrs). LTSA was register-based first event of ≥6 consecutive weeks of sickness absence during 4-year follow-up. The association between ilrs and LTSA was analyzed using a Cox proportional hazards model adjusted for remaining physical behaviors and potential confounders, then separately adjusting for and stratifying by education and type of work.

Results

During the follow-up, 21% of the workers experienced LTSA. In leisure, more relative MVPA time was negatively associated with LTSA (20% lower risk with 20 min more MVPA, p = 0.02). At work, more relative MVPA time was positively associated with LTSA (15% higher risk with 20 min more MVPA, p = 0.02). Results remained unchanged when further adjusted for or stratified by education and type of work.

Conclusion

These findings provide further support to the ‘PA paradox’.

Light-intensity physical activity derived from count or activity types is differently associated with adiposity markers

Aim

The aim of this study was to compare the association between count‐ and activity type–based definitions of light‐intensity physical activity (LIPA) and adiposity markers.

Methods

A total of 516 Danish workers participated in 1‐4 days of hip‐ and thigh‐based accelerometer measurements. Three definitions of average daily time spent in LIPA were derived: LIPA (1) time spent between 100 and 2029 CPM, LIPA (2) time spent moving and slow walking, and LIPA (3) time spent moving, walking slow, and standing. Adiposity markers were body mass index (BMI), body fat percentage, and waist circumference. The cross‐sectional association between the three LIPA definitions and adiposity markers was analyzed and interpreted using compositional regression models followed by reallocation of time between LIPA, moderate‐to‐vigorous physical activity (MVPA), and sedentary behavior (SB), respectively.

Results

The geometric means of daily time (min/day) spent in LIPA 1, LIPA 2, and LIPA 3 were 326, 102, and 274, respectively. We found the direction and strength of the association between the relative importance of daily time spent in LIPA and the adiposity markers to depend on the LIPA definition. For example, reallocating 30 minutes from MVPA to LIPA 1, LIPA 2 and LIPA 3 were associated with a 2.97 (95% CI: 0.68; 5.27), −0.71 (95% CI: −1.43; 0.02), and −0.45 (95% CI: −1.01; 0.11) difference in BMI, respectively.

Conclusion

Our findings highlight the need for caution when comparing results from studies using different definitions of LIPA.

"Study protocol for the ≥65 years NOrthern jutland Cohort of Fall risk Assessment with Objective measurements (the NOCfao study)"

Background

Accidental falls are common among community-dwellers, probably due to the level of physical activity and impaired postural stability. Today, fall risk prediction tools’ discriminative validity are only moderate. In order to increase the accuracy, multiple variables such as highly validated objective field measurements of physical activity and impaired postural stability should be adressed in order to predict falls. The main aim of this paper is to describe the ≥65 years NOrthern jutland Cohort of Fall risk Assessment with Objective measurements (NOCfao) investigating the association between physical activity and impaired postural stability and the risk of fall episodes among community-dwelling older adults.

Methods

The study consists of a baseline session where the participants are asked to respond to three questionnaires, perform physical tests (i.e., measuring strength in the upper and lower extremities, balance, and walking speed), participate in an assessment of pain sensitivity, and to wear an ankle mounted pedometer for measuring physical activity for 5 days. Subsequently, the fall incidences and the circumstances surrounding the falls during the previous 1 to 2 months will be recorded throughout a one-year follow-up period.

Discussion

This study will add to the present-day understanding of the association between physical activity and impaired postural stability and the risk of fall episodes among community-dwelling older adults. These data will provide valid and reliable information on the relationship between these variables and their significance for community-dwelling older adults.

Trial registration

ClinicalTrials.gov identifier: NCT2995317. Registered December 13th, 2016.

Sensor Technologies to Manage the Physiological Traits of Chronic Pain: A Review

Non-oncologic chronic pain is a common high-morbidity impairment worldwide and acknowledged as a condition with significant incidence on quality of life. Pain intensity is largely perceived as a subjective experience, what makes challenging its objective measurement. However, the physiological traces of pain make possible its correlation with vital signs, such as heart rate variability, skin conductance, electromyogram, etc., or health performance metrics derived from daily activity monitoring or facial expressions, which can be acquired with diverse sensor technologies and multisensory approaches. As the assessment and management of pain are essential issues for a wide range of clinical disorders and treatments, this paper reviews different sensor-based approaches applied to the objective evaluation of non-oncological chronic pain. The space of available technologies and resources aimed at pain assessment represent a diversified set of alternatives that can be exploited to address the multidimensional nature of pain.

Cervical musculoskeletal disorders and their relationships with personal and work-related factors among electronic assembly workers

INTRODUCTION

Electronics assembly workers are reported to have a high prevalence of musculoskeletal disorders (MSDs). This study investigated the prevalence of cervical MSDs and the complex relationships between cervical MSDs and individual, physical, psychosocial factors among electronics assembly workers.

METHODS

In this cross-sectional survey, self-administered questionnaires from 700 workers in electronics manufacturing workshops were analysed. Information concerning musculoskeletal symptoms, personal and work-related factors was collected. Finally, the prevalence of cervical MSDs was computed for different subgroups, and the relationships with different factors were analyzed using logistic regression and structural equation modeling (SEM).

RESULTS

The total 12 month prevalence of cervical MSDs among the survey population was 29.4%. Variables of gender, job tenure, twisting head frequently, neck flexion/extension for long time and work required to be done quickly showed significant associations with MSDs in a multivariate logistic regression (P < 0.05). The SEM analysis showed moderate and significant correlations between postural load (γ = 0.279), gender (γ = 0.233) and cervical MSDs, while there were weak but significant correlations between vibration (γ = 0.024), work stress (γ = 0.126), job tenure (γ = 0.024) and cervical MSDs. Both work stress and vibration affected the MSDs indirectly through postural load.

CONCLUSIONS

The logistic regression results support previous general epidemiological MSD studies, and indicates that individual, physical, and psychosocial factors are related to cervical MSDs. The SEM provides a better approximation of the complexity of the relationship between risk factors and cervical MSDs. Improving awkward postures may be effective ways to control the influence of occupational stressors or vibration on MSDs. Practical Applications: The study is to improve prevention of MSDs among electronics assembly workers and promote their occupational health.

Associations between occupational relative aerobic workload and resting blood pressure among different age groups: a cross-sectional analysis in the DPhacto study

OBJECTIVE

High levels of occupational physical activity (OPA) increase heart rate, blood pressure (BP) and the risk of hypertension. Older workers may be more vulnerable to high levels of OPA due to age-related degeneration of the cardiovascular system and cardiorespiratory fitness. This study investigates the association of relative aerobic workload (RAW) with resting BP and examines if this relation is moderated by age.

DESIGN

Cross-sectional epidemiological study.

SETTING

Data were collected among employees of 15 Danish companies in the cleaning, manufacturing and transport sectors.

PARTICIPANTS

2107 employees were invited for participation, of these 1087 accepted and 562 (42% female and 4% non-Westerns) were included in the analysis based on the criteria of being non-pregnant, no allergy to bandages, sufficient amount of heart rate data corresponding to ≥4 work hours per workday or 75% of average work hours, and no missing outcome and confounder values.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measure was BP.

RESULTS

Heart rate reserve was estimated from ambulatory 24-hour heart rate measures covering 2.5 workdays per participant (SD 1.0 day). Age significantly moderated the association between RAW and BP. Mean intensity and duration of high RAW (≥30% heart rate reserve) showed positive associations with diastolic BP and negative associations with pulse pressure (PP) among participants ≥47 years old. Tendencies towards negative associations between RAW and BP were seen among participants <47 years old.

CONCLUSIONS

Mean intensity and duration of RAW increased diastolic BP among participants ≥47 years old. Negative associations with PP may be due to healthy worker selection bias. Prevention of hypertension should consider reductions in RAW for ageing workers.

Movement behavior profiles and obesity: a latent profile analysis of 24-h time-use composition among Danish workers

BACKGROUND/OBJECTIVES

An element of obesity prevention is increasing total physical activity energy expenditure. However, this approach does not incorporate the balance of various movement behaviors-physical activity, sedentary behaviors and sleep-across domains of the day. We aimed to identify time-use profiles over work and leisure, termed 'movement behavior profiles' and to investigate their association with obesity.

SUBJECTS/METHODS

Eight-hundred-and-seven workers completed (a) thigh accelerometry and diaries to determine their 24-h composition of behaviors (sedentary and standing, light physical activity and moderate-to-vigorous physical activity at work and leisure, and time in bed) and (b) obesity measurements. Movement behavior profiles were determined using latent profile analyses of isometric log-ratios of the 24-h composition, and labeled according to animal movement behavior traits. Linear models were applied to determine the association between profiles and obesity.

RESULTS

Four profiles were identified, labeled as "Chimpanzees" (n = 226), "Lions" (n = 179), "Ants" (n = 244), and "Koalas" (n = 158). "Chimpanzees" work time was evenly distributed between behaviors while their leisure time was predominantly active. Compared to Chimpanzees, "Lions" were more active at work and sedentary during leisure and spent more time in bed; "Ants" were more active at work and during leisure; "Koalas" were more sedentary at work and leisure and spent similar time in bed. With "Chimpanzees" as reference, "Lions" had least favorable obesity indicators: +2.0 (95% confidence interval [CI] 0.6, 3.4) %body fat, +4.3 cm (1.4, 7.3) waist circumference and +1.0 (2.0, 0.0) Body Mass Index (BMI), followed by "Koalas" +2.0 (0.4, 3.7) %body fat, +3.1 cm (0.1, 6.0) waist circumference, and +0.8 (-0.30, 1.94) BMI. No significant differences were found between "Chimpanzees" and "Ants".

CONCLUSIONS

Movement behavior profiles across work and leisure time-use compositions are associated with obesity. Achieving adequate balance between work and leisure movement behaviors should be further investigated as a potential obesity prevention strategy.

Validation of a Short-Form Version of the Danish Need for Recovery Scale against the Full Scale

Introduction: The Need for Recovery (NFR) Scale facilitates the understanding of the factors that can lead to sustainable working and employability. Short-form scales can reduce the burden on researchers and respondents. Our aim was to create and validate a short-form Danish version of the NFR Scale. Methods: Two datasets were used to conduct the exploratory and confirmatory analyses. This was done using qualitative and quantitative methods. The exploratory phase identified several short-form versions of the Danish NFR Scale and evaluated the quality of each through the assessment of content, construct and criterion validity, and responsiveness. These evaluations were then verified through the confirmatory analysis, using the second dataset. Results: A short-form NFR scale consisting of three items (exhausted at the end of a work day, hard to find interest in other people after a work day, it takes over an hour to fully recover from a work day) showed excellent validity and responsiveness compared to the nine-item scale. Furthermore, a short-form consisting of just two items also showed excellent validity and good responsiveness. Conclusion: A short-form NFR scale, consisting of three items from the Danish NFR Scale, seems to be an appropriate substitute for the full nine-item scale.

Assessing physiological response mechanisms and the role of psychosocial job resources in the physical activity health paradox: study protocol for the Flemish Employees' Physical Activity (FEPA) study

Background

In the current labour system many workers are still exposed to heavy physical demands during their job. In contrast to leisure time physical activity (LTPA), occupational physical activity (OPA) is associated with an increased risk of cardiovascular diseases and all-cause mortality, termed “the physical activity (PA) health paradox”. In order to gain more insight into the PA health paradox, an exploration of structural preventive measures at the workplace is needed and therefore objective field measurements are highly recommended. The objective of this paper is to provide an overview of the protocol of the Flemish Employees’ Physical Activity (FEPA) study, including objective measurements of PA, heart rate (HR) and cardiorespiratory fitness (CRF) to gain more insight into the PA health paradox.

Methods

A total of 401 workers participated in the FEPA study across seven companies in the service and production sector in Belgium. The participants comprised 167 men and 234 women, aged 20 to 65 years. OPA and LTPA were assessed by two Axivity AX3 accelerometers on the thigh and upper back. Ambulatory HR was measured by the Faros eMotion 90° monitor. Both devices were worn during two to four consecutive working days. In addition, CRF was estimated by using the Harvard Step Test. Statistical analyses will be performed using Pearson correlation, and multiple regression adjusted for possible confounders.

Discussion

This study aims to provide a better insight in the PA health paradox and the possible buffering factors by using valid and objective measurements of PA and HR (both during LTPA and OPA) over multiple working days. The results of the study can contribute to the prevention of cardiovascular disease by providing tailored recommendations for participants with high levels of OPA and by disseminating the results and recommendations to workplaces, policy makers and occupational health practitioners.

Is high aerobic workload at work associated with leisure time physical activity and sedentary behaviour among blue-collar workers? A compositional data analysis based on accelerometer data

Objective

This study aimed to investigate the hypothesized negative association between duration of work time spent at a high relative aerobic workload and leisure time movement behaviours among blue-collar workers.

Methods

This was a cross-sectional study based on heart rate and accelerometer data from 803 blue-collar workers (447 men and 356 women). Relative aerobic workload was measured as percentage of heart rate reserve during work (%HRR). Leisure time movement behaviours were expressed in terms of leisure time spent in sedentary and active behaviours in uninterrupted bouts (i.e. <10 min, ≥10–30 min and >30 min). Compositional regression and isotemporal substitution models were used to assess the association between the predominance of work time spent at ≥40%HRR and leisure time spent in sedentary and active bouts. All analyses were stratified by sex.

Results

For men, there was no statistically significant association between the predominance of work time spent at ≥40%HRR and leisure time movement behaviours. Among women, the predominance of ≥40%HRR at work was negatively associated with relative leisure time spent in ≥10 min bouts of active behaviour (β^ = -0.21, p = 0.02) and a theoretical 15 min reallocation of work time from <40%HRR to ≥40%HRR was estimated to decrease active behaviour by 6 min during leisure time.

Conclusion

Our result highlights the need for considering work-related barriers for an active leisure time in high-risk populations. Longitudinal studies are warranted to disentangle the relationship between physically demanding work characteristics and leisure time movement behaviours in such populations.

Sick leave due to musculoskeletal pain: determinants of distinct trajectories over 1 year

Purpose

This study aimed to identify sub-groups of workers with different trajectories of sick leave due to musculoskeletal pain over 1 year, and to investigate the extent to which the identified trajectories are associated with personal, occupational, lifestyle, and pain-related factors at baseline.

Methods

Data on 981 blue- and white-collar workers were analyzed in the DPHACTO cohort (2012–2014). The number of days on sick leave due to pain was reported using text messages at 4-week intervals across 1 year. Latent class growth analysis was used to distinguish sub-groups with different trajectories of sick leave. A web-based questionnaire at baseline was used to assess personal, occupational (physical and psychosocial), lifestyle, and pain-related factors. Multinomial regression models were constructed to determine associations between baseline factors and trajectories of sick leave (referencing no sick leave), with adjustment for potential confounders.

Results

Four distinct sub-groups were identified, with trajectories of sick leave due to pain ranging from no sick leave (prevalence 76%; average 0.5 days/year) to some days and increasing sick leave due to pain over 1 year (2%; 89 days/year). The increasing trajectory of sick leave was associated with higher perceived physical exertion, more time in manual work, less social community and influence at work, less leisure-time physical activity, smoking, and more severe symptoms (e.g., multisite pain, low back pain intensity, and pain interference).

Conclusions

We identified four distinct trajectories of sick leave due to musculoskeletal pain. The sub-group with increasing sick leave due to pain was associated with several modifiable physical and psychosocial factors at work and outside work, which may have implications for prevention.

Electronic supplementary material

The online version of this article (10.1007/s00420-019-01447-y) contains supplementary material, which is available to authorized users.

Is Daily Composition of Movement Behaviors Related to Blood Pressure in Working Adults?

INTRODUCTION

To investigate the association of the daily composition of time spent sedentary, in light physical activity and moderate-to-vigorous physical activity and time in bed (movement behaviors) with blood pressure (BP) among white- and blue-collar workers.

METHODS

Systolic BP (SBP), diastolic BP (DBP) and body mass index of 827 workers were objectively measured. Daily composition of movement behaviors was derived from an Actigraph placed on the thigh for 1 to 5 d using the Acti4 software (2012-2013). The composition was expressed as isometric log-ratios. The cross-sectional associations between daily movement behavior composition and BP were investigated using the Compositional Data Analysis approach. The associations were adjusted for age, sex, body mass index, lift/carry duration, medication intake, and job sector.

RESULTS

Daily composition of time spent in movement behaviors was significantly associated with SBP (F = 2.84, P = 0.04), but not DBP (F = 0.48, P = 0.69). Specifically, time reallocation to sedentary time and light physical activity from the remaining behaviors was deleteriously associated with SBP, whereas time reallocation to time in bed and moderate-to-vigorous physical activity from the remaining behaviors was beneficially associated with SBP. However, the results were only significant for time spent sedentary (P = 0.01) and in bed (P = 0.047).

CONCLUSIONS

Daily composition of movement behaviors is associated with SBP among workers. Spending more time sedentary compared with other behaviors was deleteriously associated with SBP, whereas spending more time in bed was beneficially associated with SBP. How time is spent in different movement behaviors throughout the day is important for BP and needs to be further investigated to be included in future clinical practice guidelines.

Are trajectories of neck-shoulder pain associated with sick leave and work ability in workers? A 1-year prospective study

OBJECTIVES

The study aimed to determine the extent to which latent trajectories of neck-shoulder pain (NSP) are associated with self-reported sick leave and work ability based on frequent repeated measures over 1 year in an occupational population.

METHODS

This longitudinal study included 748 Danish workers (blue-collar, n=620; white collar, n=128). A questionnaire was administered to collect data on personal and occupational factors at baseline. Text messages were used for repeated measurements of NSP intensity (scale 0-10) over 1 year (14 waves in total). Simultaneously, self-reported sick leave (days/month) due to pain was assessed at 4-week intervals, while work ability (scale 0-10) was assessed using a single item (work ability index) at 12-week intervals over the year. Trajectories of NSP, distinguished by latent class growth analysis, were used as predictors of sick leave and work ability in generalised estimation equations with multiple adjustments.

RESULTS

Sick leave increased and work ability decreased across all NSP trajectory classes (low, moderate, strong fluctuating and severe persistent pain intensity). In the adjusted model, the estimated number of days on sick leave was 1.5 days/month for severe persistent NSP compared with 0.1 days/month for low NSP (relative risk=13.8, 95% CI 6.7 to 28.5). Similarly, work ability decreased markedly for severe persistent NSP (OR=12.9, 95% CI 8.5 to 19.7; median 7.1) compared with low NSP (median 9.5).

CONCLUSION

Severe persistent NSP was associated with sick leave and poor work ability over 1 year among workers. Preventive strategies aiming at reducing severe persistent NSP among working populations are needed.

Technically measured compositional physical work demands and prospective register-based sickness absence (PODESA): a study protocol

BACKGROUND

Various physical work demands are shown to be associated with sickness absence. However, these studies have: (a) predominantly used self-reported data on physical work demands that have been shown to be inaccurate compared with technical measurements, (b) principally focused on various physical work demands in 'isolation', i.e. ignoring their co-dependency - compositional nature -, and (c) mainly used register data on long-term sickness absence. The present article describes the protocol of a study with the objective of investigating the association between technically measured compositional data on physical work demands and prospective long- and short-term register-based data on sickness absence.

METHODS

'The technically measured compositional Physical wOrk DEmands and prospective association with register-based Sickness Absence study (PODESA)' comprises data from two Danish cohorts (NOMAD and DPhacto) primarily on blue-collar workers. In the PODESA cohort, data on 1108 workers were collected at baseline (between 2011 and 2014). The cohort data comprise, e.g., self-reported information on descriptives, lifestyle, workday, and health, as well as accelerometer-based measurements of physical work demands (physical activity, movements, and postures). These baseline measurements are linked with prospective register-based data on sickness absence for up to four years after baseline. The prospective association between physical work demands and sickness absence will be analysed using a Compositional Data Analysis approach.

DISCUSSION

PODESA provides a unique possibility of unravelling which combinations of physical work demands are associated with prospective sickness absence. PODESA employs technically measured information on physical work demands (taking into account the compositionality of physical work demand data) and prospective sickness absence data. The findings from PODESA can be used to develop strengthened preventive interventions for sickness absence. Results are expected in 2019-2021.

Objectively Measured Sitting and Standing in Workers: Cross-Sectional Relationship with Autonomic Cardiac Modulation

Excessive sitting and standing are proposed risk factors for cardiovascular diseases (CVDs), possibly due to autonomic imbalance. This study examines the association of objectively measured sitting and standing with nocturnal autonomic cardiac modulation. The cross-sectional study examined 490 blue-collar workers in three Danish occupational sectors. Sitting and standing during work and leisure were assessed during 1⁻5 days using accelerometers. Heart rate (HR) and heart rate variability (HRV) were obtained during nocturnal sleep as markers of resting autonomic modulation. The associations of sitting and standing still (h/day) with HR and HRV were assessed with linear regression models, adjusted for age, gender, body mass index, smoking, and physical activity. More sitting time during leisure was associated with elevated HR (p = 0.02), and showed a trend towards reduced HRV. More standing time at work was associated with lower HR (p = 0.02), and with increased parasympathetic indices of HRV (root mean squared successive differences of R-R intervals p = 0.05; high-frequency power p = 0.07). These findings, while cross-sectional and restricted to blue-collar workers, suggest that sitting at leisure is detrimental to autonomic cardiac modulation, but standing at work is beneficial. However, the small effect size is likely insufficient to mitigate the previously shown detrimental effects of prolonged standing on CVD.

Daily domain-specific time-use composition of physical behaviors and blood pressure

Background

Previous research has shown contrasting effects on hypertension for occupational and leisure-time physical behaviors—physical activity and sedentary behavior and time in bed. However, (a) none of these studies have addressed the compositional property of the physical behaviors and (b) most knowledge on the association between domain-specific physical behaviors and hypertension relies upon self-reported physical behaviors information primarily on white-collar worker study samples. We aimed to be the first to disentangle the relationship between technically measured 24-h time-use behaviors in work and leisure domains and blood pressure among blue-collar workers using a compositional data analysis approach.

Methods

Workers (n = 669) wore accelerometers to measure daily minutes of work and leisure sedentary time, light physical activity (LPA) and moderate-to-vigorous physical activity (MVPA), and time in bed which were isometrically log-transformed. Cross-sectional linear association between time-use composition and systolic (SBP) and diastolic (DBP) blood pressure were determined using compositional isotemporal substitutions models.

Results

The time-use composition at the work and leisure domains was significantly associated with SBP (F = 4.98, p < 0.001) and DBP (F = 2.91, p = 0.008). Reallocating sedentary time to remaining behaviors within each domain—work and leisure—was favorably associated with SBP. Similar results were observed when reallocating time in bed from the remaining leisure behaviors. Results for reallocating time to/from MVPA and LPA at both domains were non-significant. Results regarding all physical behaviors for DBP were generally non-significant.

Conclusions

Time-use composition of physical behaviors at work and leisure is associated with blood pressure among blue-collar workers. At both domains, reallocating sedentary time to remaining behaviors, especially to time in bed at leisure may reduce blood pressure. Our results, based on a compositional data approach, can be used to better design accurate and comprehensive time-use recommendations both at work and leisure for high-risk groups like blue-collar workers.

Electronic supplementary material

The online version of this article (10.1186/s12966-018-0766-1) contains supplementary material, which is available to authorized users.

Are accelerometer measures of temporal patterns of static standing associated with lower extremity pain among blue-collar workers?

BACKGROUND

Pain in the lower extremities is common among blue-collar workers, with prolonged static standing as a potential risk factor. However, little is known about the association between diurnal accelerometer measures of static standing and pain in the lower extremities, and the potential importance of temporal patterns of static standing for this association.

RESEARCH QUESTION

We aimed to investigate the cross-sectional association between accelerometer measures of total static standing time and temporal patterns (bout duration) of static standing (short: 0-5 min; moderate: >5-10 min; and long bouts: >10 min) during total day, work and leisure and pain intensity (on a 0-10 scale) in hips, knees and feet/ankles.

METHODS

Accelerometers were used to measure static standing during four consecutive days among 677 blue-collar workers. Linear regression analyses were used to investigate the association between static standing time and pain intensity in the lower extremities.

RESULTS

Total static standing time comprised, on average, 3.9 h per day. 72.6% of the workers were exposed to long bouts of static standing, averaging 0.1 h per day. Short bouts of static standing were positively associated with hip and knee pain during total day, and positively associated with knee pain during work. Also, total static standing time during leisure was positively associated with knee and hip pain. A negative, but not significant, association was found for static standing in moderate bouts at work and hip pain.

SIGNIFICANCE

Even though the associations found were weak, these findings suggest that the temporal pattern of static standing is of importance for pain in the lower extremities. Future research should examine the possibility that moderate bouts of standing could play a role in preventing lower extremity pain.

The association between multisite musculoskeletal pain and cardiac autonomic modulation during work, leisure and sleep - a cross-sectional study

Background

The prevention and rehabilitation of multisite musculoskeletal pain would benefit from studies aiming to understand its underlying mechanism. Autonomic imbalance is a suggested mechanism for multisite pain, but hardly been studied during normal daily living. Therefore, the aim of the study is to investigate the association between multisite musculoskeletal pain and cardiac autonomic modulation during work, leisure and sleep.

Methods

This study is based on data from the “Danish Physical activity cohort with objective measurements” among 568 blue-collar workers. Pain intensity scales were dichotomized according to the median of each scale, and the number of pain sites was calculated. No site was regarded as the pain-free, one site was considered as single-site musculoskeletal pain and pain in two or more sites was regarded as multisite musculoskeletal pain. Heart rate variability (HRV) was measured by an electrocardiogram system (ActiHeart) and physical activity using accelerometers (Actigraph). Crude and adjusted linear mixed models were applied to investigate the association between groups and cardiac autonomic regulation during work, leisure and sleep.

Results

There was no significant difference between groups and no significant interaction between groups and domains in the crude or adjusted models for any HRV index. Significant differences between domains were found in the crude and adjusted model for all indices, except SDNN; sleep time showed higher values than leisure and work time, except for LF and LF/HF, which were higher during work.

Conclusion

This cross-sectional study showed that multisite musculoskeletal pain is not associated with imbalanced cardiac autonomic regulation during work, leisure and sleep time.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2312-3) contains supplementary material, which is available to authorized users.

Self-recordings of upper arm elevation during cleaning - comparison between analyses using a simplified reference posture and a standard reference posture

BACKGROUND

To reduce ergonomic risk factors in terms of awkward and constrained postures and high velocities, it is important to perform adequate risk assessments. Technical methods provide objective measures of physical workload. These methods have so far mainly been used by researchers. However, if written instructions how to apply the sensors and how to adopt the reference posture are provided, together with triaxial accelerometers, it may be possible for employees to record their own physical workload. The exposure in terms of e.g. upper arm elevations could then easily be assessed for all workers in a workplace. The main aims of this study were: 1) to compare analyses for self-recording of upper arm elevation during work using a simplified reference posture versus using a standard reference posture, and 2) to compare the two reference postures.

METHODS

Twenty-eight cleaners attached an accelerometer to their dominant upper arm and adopted a simplified reference according to a written instruction. They were thereafter instructed by a researcher to adopt a standard reference. Upper arm elevations were recorded for 2 or 3 days. Each recording was analysed twice; relative to the simplified reference posture and relative to the standard reference posture. The group means of the differences in recorded upper arm elevations between simplified and standard reference analyses were assessed using Wilcoxon signed ranks test. Furthermore, we calculated the group mean of the differences between the simplified reference posture and the standard reference posture.

RESULTS

For arm elevation during work (50th percentile), the group mean of the differences between the two analyses was 0.2° (range -7 - 10°). The group mean of the differences between the two references was 9° (range 1 - 21°). The subjects were able to follow the instructions in the protocol and performed self-recording of upper arm elevation and velocity.

CONCLUSIONS

The small difference between the two analyses indicates that recordings performed by employees themselves are comparable, on a group level, with those performed by researchers. Self-recordings in combination with action levels would provide employers with a method for risk assessment as a solid basis for prevention of work-related musculoskeletal disorders.

The association between occupational standing and sedentary leisure time over consecutive workdays among blue-collar workers in manual jobs

PURPOSE

Blue-collar workers spend much leisure time sedentary, which is associated with numerous health impairments. The extensive sedentary leisure time among blue-collar workers could be caused by fatigue from physically demanding work, like stationary standing. Occupational stationary standing is prevalent in many blue-collar jobs and has been shown to induce fatigue. The objective of this study was to investigate the association between occupational standing and sedentary leisure time over several workdays among blue-collar workers.

METHODS

This study used data from 925 workers from Danish workplaces within cleaning, transportation, manufacturing, construction, road maintenance, garbage disposal, and health service. Eligible workers wore accelerometers for 2-5 consecutive workdays. A linear regression was used to investigate the association between percent of work time spent standing and leisure time spent sedentary. A multilevel growth model was used to assess the association between standing during work and sedentary leisure time over consecutive workdays.

RESULTS

We found no association between percent of work hours spent standing and percent of leisure time spent sedentary (coef. = 0.01, p = 0.84). The results showed an increase in the workers' sedentary leisure time over a week (coef. = 0.70, p < 0.01). However, this increase was not associated with consecutive workdays exposed to occupational standing (coef. = 0.02, p = 0.42).

CONCLUSION

In this study, we found no support of a positive association between occupational standing and sedentary leisure time. This lack of association could be attributable to a low variation in sedentary leisure time or the chosen definition and measurement of occupational standing.

Association between objectively measured static standing and low back pain - a cross-sectional study among blue-collar workers

This study aims to investigate the cross-sectional association between objectively measured total time and temporal patterns of static standing (short bouts: 0-5 min; moderate bouts: >5-10 min; and long bouts: >10 min) during work and leisure and low back pain (LBP) among 698 blue-collar workers. Workers reported LBP on a 0-10 scale. The association between time spent on static standing and LBP was tested with linear regression. A positive association with LBP intensity was found for long bouts of static standing (β = 0.27) during total day (work + leisure), and total static standing time at leisure (β = 0.12). No significant associations were found for static standing during work and LBP intensity. These findings indicate that particularly long bouts of static standing over the entire day contribute to LBP in blue-collar workers. Practitioner Summary: The association between LBP and static standing time was investigated. This study indicates that prolonged time standing during total day and standing during leisure are positively associated with LBP among blue-collar workers. Therefore, practitioners should consider long periods of standing as a potential risk factor for LBP.

Does Physically Demanding Work Hinder a Physically Active Lifestyle in Low Socioeconomic Workers? A Compositional Data Analysis Based on Accelerometer Data

Leisure time physical activity (LTPA) is strongly associated with socioeconomic position (SEP). Few studies have investigated if demanding occupational physical activity (OPA) could impede a physically active lifestyle in low SEP groups. The aim of this study was to investigate the association between OPA and LTPA among low SEP men and women. We used cross-sectional data from 895 low SEP workers who wore accelerometers for 1–5 consecutive workdays. The associations between the relative importance of activities performed during work and leisure time were assessed using compositional regression models stratified on sex. Compositional isotemporal substitution models were used to assess the implication of increasing occupational walking, standing, or sitting on LTPA. We found dissimilarity in LTPA between the sexes, with men spending more waking leisure time sedentary than women (men ~67%, women ~61%), suggesting women performed more household tasks. In men, the associations between OPA and LTPA were weak. In women, the strongest association was observed between the relative importance of occupational walking and leisure time standing (β^ = −0.16; p = 0.01), where reallocating 15 min work time to occupational walking showed an expected decrease in leisure time standing of 7 min. If this time was spent on additional sedentary leisure time, it could have adverse health consequences.

A comparison of standard and compositional data analysis in studies addressing group differences in sedentary behavior and physical activity

BACKGROUND

Data on time spent in physical activity, sedentary behavior and sleep during a day is compositional in nature, i.e. they add up to a constant value. Compositional data have fundamentally different properties from unconstrained data in real space, and require other analytical procedures, referred to as compositional data analysis (CoDA). Most physical activity and sedentary behavior studies, however, still apply analytical procedures adapted to data in real space, which can lead to misleading results. The present study describes a comparison of time spent sedentary and in physical activity between age groups and sexes, and investigates the extent to which results obtained by CoDA differ from those obtained using standard analytical procedures.

METHODS

Time spent sedentary, standing, and in physical activity (walking/running/stair climbing/cycling) during work and leisure was determined for 1-4 days among 677 blue-collar workers using accelerometry. Differences between sexes and age groups were tested using MANOVA, using both a standard and a CoDA approach based on isometric log-ratio transformed data.

RESULTS

When determining differences between sexes for different activities time at work, the effect size using standard analysis (η² = 0.045, p < 0.001) was 15% smaller than that obtained with CoDA (η² = 0.052, p < 0.001), although both approaches suggested a statistically significant difference. When determining corresponding differences between age groups, CoDA resulted in a 60% larger, and significant, effect size (η² = 0.012, p = 0.02) than that obtained with the standard approach (η² = 0.008, p = 0.07). During leisure, results based on standard (age; η² = 0.007, p = 0.09; sex; η² = 0.052, p < 0.001) and CoDA (age; η² = 0.007, p = 0.09; sex; η² = 0.051, p < 0.001) analyses were similar.

CONCLUSION

Results and, hence, inferences concerning age and sex-based differences in time spent sedentary and in physical activity at work differed between CoDA and standard analysis. We encourage researchers to use CoDA in similar studies, to adequately account for the compositional nature of data on physical activity and sedentary behavior.

Shift work is associated with reduced heart rate variability among men but not women

BACKGROUND

Imbalance in the autonomic nervous system due to a disrupted circadian rhythm may be a cause of shift work-related cardiovascular diseases.

OBJECTIVE

We aimed to determine the association between shift work and cardiac autonomic activity in blue-collar workers.

METHODS

The study included 665 blue-collar workers aged 18-68 years in different occupations from two Danish cohort studies. Time and frequency domain parameters of heart rate variability (HRV) were measured during sleep using the Actiheart monitor, and used as markers of cardiac autonomic function. Multiple linear regression analyses were used to investigate differences in HRV between day and shift workers.

RESULTS

Shift workers had no significantly different HRV parameters than day workers, except for a lower VLF (B: 0.21; 95% CI: -0.36-0.05). The lower VLF was only present among non-night shift workers (p < 0.05) and not among night shift workers (p > 0.05). Results differed significantly by gender (p for interaction < 0.10): among men, shift work was negatively associated with RMSSD (B: -7.83; 95% CI: -14.28-1.38), SDNN (B: -7.0; 95% CI: -12.27-1.78), VLF (B: -0.27; 95% CI: -0.46-0.09) and Total Power (B: -0.61; 95% CI: -1.20-0.03), while among women, shift work was only associated with the LF/HF ratio (B: -0.29; 95% CI: -0.54-0.03).

CONCLUSION

Shift work was particularly associated with lower HRV during sleep among men. This indicates that shift work causes imbalance in the autonomic nervous system among men, which might increase their risk of cardiovascular diseases.

Sleep positions and nocturnal body movements based on free-living accelerometer recordings: association with demographics, lifestyle, and insomnia symptoms

BACKGROUND

In order to establish normative values for body positions and movements during sleep, the objective of this study was to explore the distribution of sleep positions and extent of nocturnal body moments and the association with sex, age, body-mass index (BMI), smoking, alcohol consumption, and insomnia symptoms.

MATERIALS AND METHODS

This cross-sectional study comprised data on a working population (363 men and 301 women) who participated in the Danish Physical Activity Cohort with Objective Measurements (DPHACTO). Measures of body position and movements were obtained from actigraph accelerometers on the thigh, upper back, and upper arm. Linear regression was used to estimate adjusted mean differences in movements among categories of demographic and lifestyle characteristics.

RESULTS

During their time in bed, participants spent 54.1% (SD 18.1%) in the side position, 37.5% (SD 18.2%) in the back position, and 7.3% (SD 12.3%) in the front position. Increasing age and BMI were associated with increased time in the side position and a proportional reduction in time in the back position. There were on average 1.6 (SD 0.7) position shifts per hour. Compared to males, females had fewer position shifts (-0.37, 95% CI -0.48 to -0.24) and fewer arm, thigh, and upper-back movements. Participants aged 20-34 years had more arm, thigh, and upper-back movements compared to participants ≥35 years. Obese participants had fewer shifts in body position (-0.15, 95% CI -0.27 to 0), but more arm, thigh, and upper-back movements compared to normal-weight participants. Smokers had fewer shifts in body position than nonsmokers (-0.27, 95% CI -0.4 to -0.13).

CONCLUSION

The predominant sleep position in adults is on the side. This preference increases with age and BMI. The extent of nocturnal body movements is associated with sex, age, BMI, and smoking.

On the health paradox of occupational and leisure-time physical activity using objective measurements: Effects on autonomic imbalance

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.

Trunk kinematics and low back pain during pruning among vineyard workers-A field study at the Chateau Larose-Trintaudon

The prevalence of low back disorders is dramatically high in viticulture. Field measurements that objectively quantify work exposure can provide information on the relationship between the adopted trunk postures and low back pain. The purposes of the present study were three-fold (1) to carry out a kinematics analysis of vineyard-workers’ pruning activity by extracting the duration of bending and rotation of the trunk, (2) to question separately the relationship between the duration of forward bending or trunk rotation with low back pain intensity and pressure pain sensitivity and (3) to question the relationship between the combined duration of forward bending and trunk rotation on low back pain intensity and pressure pain sensitivity. Fifteen vineyard-workers were asked to perform pruning activity for 12 minutes with a wireless triaxial accelerometer placed on their trunk. Kinematic analysis of the trunk showed that vineyard-workers spent more than 50% of the time with the trunk flexed greater than 30° and more than 20% with the trunk rotated greater than 10°. These results show that pruning activity lead to the adoption of forward bended and rotated trunk postures that could significantly increase the risk of work related musculoskeletal disorders in the low back. However, this result was mitigated by the observation of an absence of significant association between the duration of forward bending and trunk rotation with low back pain intensity or pressure pain sensitivity. Even if prospective field measurements and studies assessing the effects of low back pain confounders are needed, this field study provides new genuine information on trunk kinematics during pruning activity.

Objectively measured physical activity and 12-month trajectories of neck–shoulder pain in workers: A prospective study in DPHACTO

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.

The variability of the trunk forward bending in standing activities during work vs. leisure time

High level of occupational physical activity (PA), contrary to leisure time activities, is generally associated with detrimental health outcomes. We hypothesized that this contrast may be associated with a different pattern of exposure variability in PA, e.g., forward bending of the trunk. The study was conducted on 657 blue-collar workers. Two accelerometers were used to identify the body posture and forward bending of the trunk during work and leisure time. The pattern of forward bending was analyzed using exposure variation analysis (EVA). The recordings comprised of 2.6 ± 0.97 working days in average, with 19.9 ± 8.1 h work and 22.9 ± 8.9 h leisure. The standard deviation and entropy of the EVA profile indicated 11% and 6% (for about 80% of subjects) less variable pattern during work compared with the leisure time, respectively. These new findings contribute to the understanding the paradoxical outcomes of PA during work and leisure.

Is prolonged sitting at work associated with the time course of neck-shoulder pain? A prospective study in Danish blue-collar workers

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 1 year in blue-collar workers.

METHODS

Data were analysed from 625 blue-collar workers in the Danish PHysical ACTivity cohort with Objective measurements (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 1 year using repeated text messages (14 in total). Linear mixed models were used to determine the relationship between per cent 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).

CONCLUSIONS

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

Low back pain patterns over one year among 842 workers in the DPhacto study and predictors for chronicity based on repetitive measurements

Background

Low back pain (LBP) occurrence and intensity are considered to fluctuate over time, requiring frequent repetitive assessments to capture its true time pattern. Text messages makes frequent reporting of LBP feasible, which enables investigation of 1) the time pattern of LBP, and 2) predictors for having a continued high (chronic) level of LBP over longer periods of time. However, this has not previously been investigated in a larger working population.

The aim of this study was to examine these two aspects in a working population of 842 workers with repetitive measurements of LBP over one year.

Methods

There were 842 workers from 15 companies in the DPhacto study participating in this study. Demographic, work- and health-related factors, and back endurance were measured at baseline, while 14 monthly repeated text message assessments of LBP intensity were prospectively collected. A factor analysis was used to cluster different time-patterns of LBP, and defining the group of participants with chronic LBP. A multi-adjusted logistic regression analysis was performed to investigate baseline predictors for chronic LBP.

Results

The factor analysis revealed two dimensions of the time pattern of LBP, defined as the LBP intensity and LBP variation, respectively. A Visual Pain Mapping was formed based on the combination of the two pain dimensions, classifying the time-patterns of LBP into four categories: (1) low intensity and low variation, (2) low intensity and high variation, (3) high intensity and high variation, (4) high intensity and low variation (defined as chronic LBP). Significant baseline predictors for chronic LBP in the fully adjusted model were high baseline LBP (p < 0.01), low workability (p < 0.01), low BMI (p < 0.05), and being a blue-collar worker (vs. white-collar worker) (p < 0.05).

Conclusion

This study presents a novel classification of the course of LBP based on repetitive measurements over a year, and revealed the predicting factors for chronic LBP based on repetitive measurements in a working population.

Temporal patterns of sitting at work are associated with neck-shoulder pain in blue-collar workers: a cross-sectional analysis of accelerometer data in the DPHACTO study

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.