Physical demands in working life and individual physical capacity

The impact of cardiorespiratory fitness and physical workload on disability pension-a cohort study of Swedish men

OBJECTIVE

Understanding the impact of physical capacity in combination with high physical workload could be beneficial for the prevention of health-related exits from work. Therefore, the aim of this study was to investigate the separate and combined effects of low cardiorespiratory fitness and high physical workload on disability pension (DP) due to any cause, musculoskeletal disorders (MSD), and cardiovascular diseases (CVD).

METHODS

A total of 279 353 men born between 1951 and 1961 were followed regarding DP between 2006 and 2020, ages 45-64. Cardiorespiratory fitness was assessed during military conscription, using an ergometer bicycle test. Physical workload was based on a job-exposure matrix (JEM) linked to occupational title in 2005. Cox regression models estimated separate and combined associations with DP.

RESULTS

Low cardiorespiratory fitness and high physical workload were associated with increased risk of DP. For all cause DP, the fully adjusted hazard ratio and 95% confidence interval for those with low cardiorespiratory fitness was 1.38 (1.32-1.46) and for those with high physical workload 1.48 (1.39-1.57). For all cause and MSD DP, but not for CVD DP, the combination of low cardiorespiratory fitness and high physical workload resulted in higher risks than when adding the effect of the single exposures.

CONCLUSION

Both low cardiorespiratory fitness in youth and later exposure to high physical workload were associated with an increased risk of DP, where workers with the combination of both low cardiorespiratory fitness and a high physical workload had the highest risks (all-cause and MSD DP).

Effects of Prevalent and Newly Diagnosed Arthritis on Changes in Perceived Physical Demands and Work Stress Among Older Workers: Results of a 3 Year Panel Study

OBJECTIVES

Examine the effects of prevalent and newly diagnosed arthritis on changes in perceived physical demands and general work stress.

METHODS

Conditional change logistic regression models examined the strength of association between arthritis and perceived (1) work stress and (2) physical demands, using data from the NIDI Pension Panel Study (n = 2099).

RESULTS

Prevalent and newly diagnosed arthritis were associated with increased odds of perceived work stress and high physical demands. Manual workers with newly diagnosed arthritis exhibited a 6.73-fold (95% CI = 2.87-15.77) increased odds of physical demands. Arthritis in three body extremities was differentially associated with increased odds of work stress and physical demands in manual and non-manual workers.

DISCUSSION

Prevalent and incident arthritis were associated with changes in work stress and physical demands in older workers. Policies and workplace interventions to reduce stress and physical demands and improve workability in older workers with arthritis are needed.

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.

Physical workload and obesity have a synergistic effect on work ability among construction workers

PURPOSE

Obesity and high physical workload are both associated with poor work ability, but the interaction between obesity and high physical workload on work ability is not yet fully understood. Obesity and high physical workload may share a common mechanical pathway, possibly leading to a synergistic negative effect on work ability. The purpose of this study was to investigate the effect of obesity on work ability in workers with high versus low physical work load.

METHODS

A longitudinal study was conducted among 36,435 Dutch construction workers who participated in at least two periodic medical examinations during the years 2008-2015. Logistic regression analyses were used to investigate the effect of manual material handling and strenuous work postures in sports on the association between obesity and work ability. Work ability was measured using the self-reported Work Ability Index consisting of seven dimensions. Confounding effects were tested for age, educational level, smoking, vigorous physical activity, psychosocial work demands, and working hours. Additive interaction between obesity and physical workload on work ability was tested using the relative excess risk due to interaction (RERI).

RESULTS

Construction workers with overweight (OR = 1.09; 95% CI 1.02-1.16) or obesity (OR = 1.27; 95% CI 1.17-1.38) had an increased risk of poor/moderate work ability. Exposure to manual material handling (OR = 1.58; 95% CI 1.49-1.68) or strenuous work postures (OR = 1.80; 95% CI 1.70-1.90) also increased the risk of poor/moderate work ability. The effect of the combination of obesity with high physical workload was greater than the sum of the individual effects (strenuous work postures: RERI = 0.39; 95% CI 0.10-0.67; manual material handling: RERI = 0.26; 95% CI 0.02-0.51).

CONCLUSIONS

Obesity and high physical workload were associated with poor work ability and had a synergistic, negative effect on work ability. Interventions that prevent obesity and high physical workload might have a beneficial effect on work ability.

A Feminist Intervention That Hurt Women: Biological Differences, Ergonomics, and Occupational Health: Une intervention féministe qui a nui aux femmes: différences biologiques, égalité, ergonomie et santé au travail

The University of Québec in Montréal has agreements with trade unions providing access to university resources. Researchers involved in this program worked in partnership with union women's and health and safety committees for more than twenty years. Not all studies succeeded in improving women's working conditions. One joint project involved observational studies of tasks done by health-care workers, complemented by interviews and questionnaires. We found that task assignments, movements, postures, and work-related musculoskeletal disorders varied by gender/sex and made recommendations for change. However, issues of pay equity, spending on health care, and contracting-out of "ancillary work" were salient. Researchers learned that in the absence of changes in power relationships in the workplace, women may be disadvantaged by denial as well as by exaggeration of female-male differences. Men may also be at risk when their gender is invisible. We suggest some feminist approaches to workplace solutions and some pathways for research. Résumé L'Université du Québec à Montréal a signé avec des centrales syndicales des ententes leur donnant un accès à des ressources universitaires. Des chercheures ont travaillé en partenariat avec des comités syndicaux de condition des femmes et de santé-sécurité au travail pendant plus de 25 ans, mais ce ne sont pas toutes les études qui ont abouti à des améliorations. Un projet concernait des observations du travail d'employé.e.s du secteur de la santé, dont les tâches, mouvements, et postures variaient selon le genre/sexe. Nous avons recommandé des transformations, mais des enjeux d'équité salariale, de coûts et de sous-traitance y ont fait obstacle. Les chercheures ont appris qu'en l'absence de transformation des rapports de pouvoir au travail, le déni des différences hommes-femmes, autant que leur exagération, peut désavantager les travailleuses (et les travailleurs). Nous suggérons des approches féministes aux solutions pour le milieu de travail, ainsi que des pistes de recherche.

Does Aerobic Exercise Increase 24-Hour Ambulatory Blood Pressure Among Workers With High Occupational Physical Activity?-A RCT

OBJECTIVE

High occupational physical activity (OPA) increases cardiovascular risk and aerobic exercise has been recommended for reducing this risk. This paper investigates the effects of an aerobic exercise intervention on 24-hour ambulatory blood pressure (ABP) among cleaners with high OPA.

METHODS

Hundred and sixteen cleaners between 18 and 65 years were randomized. During the 4-month intervention period, the aerobic exercise group (AE) (n = 57) performed worksite aerobic exercise (2 × 30 minutes/week), while the reference group (REF) (n = 59) attended lectures. Between-group differences in 4-month ABP changes were evaluated by intention-to-treat analysis using a repeated-measure 2 × 2 multiadjusted mixed-models design.

RESULTS

Relative to REF, 24-hour ABP significantly increased in AE: systolic 3.6 mm Hg (95% confidence interval (CI) 1.6–5.7) and diastolic 2.3 mm Hg (95% CI 0.9–3.8). Cleaners with high aerobic workload exhibited particularly high 24-hour ABP increases: systolic 6.0 mm Hg (95% CI 2.4–9.6), and diastolic 3.8 mm Hg (95% CI 1.3–6.4).

CONCLUSION

Aerobic exercise increased 24-hour ABP among cleaners. This adverse effect raises questions about the safety and intended benefits of aerobic exercise, especially among workers with high OPA and a demanding aerobic workload.

http://www.controlled-trials.com/ISRCTN86682076. Unique identifier ISRCTN86682076.

CLINICAL TRIAL REGISTRATION

Trial Number ISRCTN86682076.

Physical activity and lung cancer risk in men and women

PURPOSE

Although evidence has accumulated that recreational physical activities (PA) may reduce lung cancer risk, there is little evidence concerning the possible role of a potentially more important source of PA, namely occupational PA. We investigated both recreational and lifetime occupational PA in relation to lung cancer risk in a population-based case-control study in Montreal, Canada (N_CASES = 727; N_CONTROLS = 1,351).

METHODS

Unconditional logistic regression was used to estimate odds ratios (OR), separately for men and women, adjusting for smoking, exposure to occupational carcinogens, and sociodemographic and lifestyle factors.

RESULTS

In both sexes, increasing recreational PA was associated with a lower lung cancer risk (OR_MEN = 0.66, 95% confidence interval (CI) 0.47-0.92; OR_WOMEN = 0.55, 95% CI 0.34-0.88, comparing the highest versus lowest tertiles). For occupational PA, no association was observed among women, while increasing occupational PA was associated with increased risk among men (OR_MEN = 1.96, 95% CI 1.27-3.01). ORs were not modified by occupational lung carcinogen exposure, body mass index, and smoking level; results were similar across lung cancer histological types.

CONCLUSIONS

Our results support the previous findings for recreational PA and lung cancer risk. Unexpectedly, our findings suggest a positive association for occupational PA; this requires replication and more detailed investigation.

Long Term Effects on Risk Factors for Cardiovascular Disease after 12-Months of Aerobic Exercise Intervention - A Worksite RCT among Cleaners

Objectives

Occupational groups exposed to high occupational physical activity have an increased risk for cardiovascular disease (CVD). This may be explained by the high relative aerobic workload. Enhanced cardiorespiratory fitness reduces the relative aerobic workload. Thus, the aim was to evaluate the 12-months effects of worksite aerobic exercise on risk factors for CVD among cleaners.

Methods

One hundred and sixteen cleaners aged 18–65 years were randomized to a group performing aerobic exercise and a reference group receiving lectures. Outcomes were collected at baseline and after 12-months. A repeated measures 2×2 multi-adjusted mixed-model design was applied to compare the between-group differences using intention-to-treat analysis.

Results

Between-group differences (p<0.05) were found favouring the aerobic exercise group: cardiorespiratory fitness 2.15 (SE 1.03) mlO₂/min/kg, aerobic workload -2.15 (SE 1.06) %HRR, resting HR -5.31 (SE 1.61) beats/min, high sensitive C-reactive protein -0.65 (SE 0.24) μg/ml. The blood pressure was unaltered. Stratified analyses on relative aerobic workload at baseline revealed that those with relative aerobic workloads ≥30% of HRR seems to impose a notable adverse effect on resting and ambulatory blood pressure.

Conclusion

This long-term worksite aerobic exercise intervention among cleaners led to several beneficial effects, but also potential adverse effects among those with high relative aerobic workloads.

Trial Registration

Controlled-Trials.com ISRCTN86682076

Heavy Physical Work: Cardiovascular Load in Male Construction Workers

This study aimed to elucidate cardiovascular loads (CVL) in construction workers during work and leisure by relative heart rate (RHR) over several days. Furthermore, we sought to evaluate the level of CVL in relation to individual factors, work ability, musculoskeletal pain and subjective general health. From a group of 255 construction workers responding to the baseline questionnaire, the CVL during work and leisure time was determined by recording RHR in 42 workers over 3–4 days. Almost 60% of the workday was spent below 20% RHR. The mean RHR during work for all participants was 16% RHR, with large differences between professions. On average, the 42 workers spent 14% of the workday at a RHR above 33%, and four subjects (10%) had a mean RHR above 33% during work. Eight (19%) of the participants had a mean length of their workday exceeding calculated maximal acceptable work time. Seven persons (17%) experienced on average one or more episode(s) of 5 min or more continuously above 33% RHR. The cardiovascular load at work was significantly associated with age and V˙O_2max, but not with work ability, musculoskeletal pain or subjective general health.

Dietary protein intake is associated with maximal and explosive strength of the leg flexors in young and older blue collar workers

The aim of this study was to investigate the association between dietary protein (PRO) intake and maximal and rapid strength of the leg flexors in blue collar (BC) working men. Twenty-four young (age, 23.2 ± 2.1 years) and 19 older (age, 52.8 ± 5.2 years) men employed in BC occupations completed a 3-day dietary record and isometric strength testing of the leg flexors. Food logs were analyzed for total PRO (TPRO) and essential amino acid (EAA) intake. Rapid and maximal strength capacities were examined from the rate of torque development at 50 milliseconds and peak torque of the torque-time curves, respectively. Pearson correlations and partial correlations were used to examine the relationships between TPRO and EAA intake on strength variables. Peak torque was positively correlated to TPRO and EAA intake in the young (r = 0.439 and r = 0.431; P < .05) and older (r = 0.636 and r = 0.605; P < .01) men, and rate of torque development at 50 milliseconds was correlated to TPRO and EAA intake in the young (r = 0.512 and r = 0.310; P = .01) and older (r = 0.662 and r = 0.665; P < .01) men, respectively. There were no relationships (P > .05) between TPRO and strength variables when controlling for EAA intake. Total PRO intake explained 20 to 44% of the variance in rapid and maximal strength for both age groups. Essential amino acid intake was largely responsible for the positive relationship between PRO intake and strength. Across young and older BC working male populations, PRO consumption was associated with both maximal and explosive strength capacities of the leg flexors muscle group.

Improved fitness after a workbased physical exercise program

Purpose

– The purpose of this paper is to investigate the effects on fitness outcomes of a work-based physical exercise (PE) intervention among women working in older people’s care. In addition, effects on productivity-related outcomes including work ability and sickness absence were studied.

Design/methodology/approach

– Employees participated in a one-year intervention involving two one-hour weekly mandatory PE sessions. The intervention (n=13) was compared to referents (n=12). Fitness tests and self-reports on work ability and sickness absence were obtained before the intervention (T1), six months into the intervention and after 12 months.

Findings

– Fitness test scores (corrected for age and weight) increased significantly over time in the intervention group but not among referents. Perceived exertion decreased significantly in the intervention group and increased significantly among referents. For self-rated work ability and sickness absence, no significant time or group differences emerged.

Research limitations/implications

– Further research on larger groups of women is needed to delineate the effects of PE on self-rated productivity and performance.

Practical implications

– Work-based PE programs can improve fitness among women in older people’s care.

Social implications

– With previous research having primarily focussed on men, this study shows that women in blue-collar jobs also may benefit from taking part in work-based PE programs.

Originality/value

– This paper makes an important contribution through its focus on the effects of a work-based PE program on fitness and possible relations to productivity, among employed women.

Are elderly construction workers sufficiently fit for heavy manual labour?

This study analysed the work ability of elderly construction workers. Forty male construction workers, 20 young (age < 33 yrs) and 20 senior (age>44 yrs) workers, were tested regarding aerobic power (VO2max) and muscle strength. The aerobic demand of a number of tasks in construction work was measured and compared with the workers' aerobic power. VO2max was higher for the young, and they performed better on most muscle strength tests. The measurements showed that about half of the senior workers had to use more than 30% of their maximum oxygen uptake on some tasks. In conclusion, because elderly construction workers decline in physical fitness, they are more exposed to overload when performing heavy manual work than are their younger peers. Increasing their individual fitness or adjusting their workload may be important for staying in the workforce for such workers.

PRACTITIONER SUMMARY

Construction workers must occasionally perform strenuous work tasks that may endanger their safety. This was more often the case for elderly workers investigated here. Elderly workers should therefore be particularly observant of their physical fitness, and should possibly train during leisure time to improve their fitness.

A 24-h assessment of physical activity and cardio-respiratory fitness among female hospital cleaners: a pilot study

The aim of this study was to evaluate the feasibility of methods for objective 24-h sampling of physical activity among cleaners. Twenty cleaners participated in three 24-h measurements. Amount of steps, heart rate (HR), cardio-respiratory fitness, body mass index (BMI) and blood pressure were measured. The methods were feasible for the objective 24-h sampling of physical activity and cardio-respiratory fitness among cleaners. Measurements showed that the cleaners walked 20,198 ± 4,627 steps per day. During working hours, the average cardio-respiratory load was 25 ± 6% of heart rate reserve (HRR). The cleaners had a low estimated cardio-respiratory fitness (34 mlO2/kg/min), a high BMI (50%, >25 kg/m(2)) and blood pressure (50%, >120/>80 mmHg). The high amount of steps, the relatively high cardiovascular load at work and low cardio-respiratory fitness illustrate the need for further investigation of the relationship between physical activity at work and in leisure, and cardiovascular health in this population.

PRACTITIONER SUMMARY

This study evaluated the feasibility of methods for objective 24-h sampling of physical activity among cleaners; the methods used were found to be feasible. The cleaners had a high cardiovascular load at work and low cardio-respiratory fitness, suggesting that there is a need for further investigations.

Health-promoting educational interventions: A one-year follow-up study

Aims: The purpose of this study was to describe and analyse the effects of health-promoting educational interventions among employees in a municipality in Sweden. Methods: A randomized controlled educational intervention study was performed with 340 employees. Supervisors and workplace champions took part in two separate educational programmes with focus on health promotion. Intervention groups were teams of supervisors, teams of workplace champions and a mixed group (supervisors and workplace champions). The control group did not take part in any of the activities. Evaluations with physical fitness tests and a self-administrated questionnaire were performed twice. Focus group discussions were held. Results: All groups raised their physical fitness level from baseline to follow-up. Females in the supervisor group had increased their mean maximal oxygen uptake from 32.0 mlO2/kg*min to 34.9 mlO2/kg*min which was more than the others. Supervisors had reached increased knowledge within the area ‘organizational factors’ and behavioural changes had been obtained within the area ‘life-style’. Workplace champions working together with their supervisors had an easier and more motivated situation than workplace champions working by themselves. Conclusions: Coaching supervisors as well as the mixed group seemed to improve the intervention of health promotion most and should be continued.

Identifying work ability promoting factors for home care aides and assistant nurses

BACKGROUND

In workplace health promotion, all potential resources needs to be taken into consideration, not only factors relating to the absence of injury and the physical health of the workers, but also psychological aspects. A dynamic balance between the resources of the individual employees and the demands of work is an important prerequisite. In the home care services, there is a noticeable trend towards increased psychosocial strain on employees at work. There are a high frequency of work-related musculoskeletal disorders and injuries, and a low prevalence of sustainable work ability. The aim of this research was to identify factors promoting work ability and self-efficacy in care aides and assistant nurses within home care services.

METHODS

This study is based on cross-sectional data collected in a municipality in northern Sweden. Care aides (n = 58) and assistant nurses (n = 79) replied to a self-administered questionnaire (response rate 46%). Hierarchical multiple regression analyses were performed to assess the influence of several independent variables on self-efficacy (model 1) and work ability (model 2) for care aides and assistant nurses separately.

RESULTS

Perceptions of personal safety, self-efficacy and musculoskeletal wellbeing contributed to work ability for assistant nurses (R2adj of 0.36, p < 0.001), while for care aides, the safety climate, seniority and age contributed to work ability (R2adj of 0.29, p = 0.001). Self-efficacy was associated with the safety climate and the physical demands of the job in both professions (R2adj of 0.24, p = 0.003 for care aides), and also by sex and age for the assistant nurses (R2adj of 0.31, p < 0.001).

CONCLUSIONS

The intermediate factors contributed differently to work ability in the two professions. Self-efficacy, personal safety and musculoskeletal wellbeing were important for the assistant nurses, while the work ability of the care aides was associated with the safety climate, but also with the non-changeable factors age and seniority. All these factors are important to acknowledge in practice and in further research. Proactive workplace interventions need to focus on potentially modifiable factors such as self-efficacy, safety climate, physical job demands and musculoskeletal wellbeing.

Si le bruit rend sourd, rend-il nécessairement sourde ?

Au Québec, des données spécifiques concernant les conditions d’emploi, de travail et de rémunération des hommes et des femmes sont publiées régulièrement. Depuis peu, des données ventilées selon le sexe commencent à alimenter les efforts de prévention en santé au travail. Malgré ces progrès, certains défis techniques, idéologiques et politiques demeurent: allant des difficultés dans les calculs des populations à risque, à la réticence à adapter les postes de travail ou à adapter la formation à la spécificité biologique des femmes. La recherche sur la santé des femmes au travail a beaucoup progressé, mais il reste plusieurs étapes à franchir. Notons également que les spécificités associées au genre des hommes sont presqu'entièrement oubliées dans les études. Il est difficile de conserver un équilibre entre la protection de la santé et l’égalité des sexes dans la recherche et l’intervention en santé au travail. Pour assurer cet équilibre, la recherche doit se faire en collaboration avec les travailleuses et travailleurs. Ils peuvent ainsi contribuer à construire une base solide d’informations qui permettront aux gouvernements, aux organismes responsables de la prévention en santé au travail, aux employeurs et aux syndicats de tenir compte, dans leurs politiques, des besoins des deux sexes en santé au travail.

Oxygen consumption prediction models for individual and combination materials handling tasks

An experiment was conducted to develop models to predict oxygen consumption of males and females engaged in common materials handling tasks including lifting, lowering, pushing, pulling, (de)palletising and combination tasks involving lifting or lowering a box and carrying it a set distance and lifting or lowering it to the destination. Nineteen male and 19 female subjects participated in the study. A psychophysical approach was used to set load limits for individual subjects for the oxygen consumption protocol. The 8398 oxygen consumption values collected were entered into the initial regression analyses and 168 potential outliers were removed before the final models were run. In addition to relevant task variables, body weight was a significant predictor variable in all models. The r(2) values for the final models ranged from 0.54 to 0.82 and the root mean square errors ranged from 90.2 ml to 294.8 ml.

Distribution and determinants of maximal physical work capacity of Korean male metal workers

The distribution of maximal physical work capacity (MPWC) can be used to establish an upper limit for energy expenditure during work (EEwork). If physically demanding work has wearing effects, there will be a negative relationship between MPWC and workload. This study was conducted to investigate the distribution of MPWC among Korean metal workers and to examine the relationship between workload and MPWC. MPWC was estimated with a bicycle ergometer using a submaximal test. Energy expenditure was estimated by measuring heart rates during work. The study subjects were 507 male employees from several metal industries in Korea. They had a lower absolute VO2max than the Caucasian populations described in previous studies. The older workers had a lower physical capacity and a greater overload at work. A negative relationship was found between MPWC and workload across all age groups. Upper limits for EEwork for all age groups and for older age groups are recommended based on the 5th percentile value of MPWC.

In vivolumbar erector spinae oxygenation and blood volume measurements in healthy men during seated whole-body vibration

Exposure to whole-body vibration is implicated as one of the occupational risk factors for lower back disorders; however, its influence on the lumbar muscle physiology is still poorly understood. The objective of this study was to investigate the effects of backrest support and hand grip contractions on lumbar muscle oxygenation and blood volume responses during seated whole-body vibration using continuous dual-wave near-infrared spectroscopy. Thirteen healthy men were exposed to frequencies of 3, 4.5 and 6 Hz on a vibration simulator, in randomized order on separate days. Each day the duration of the protocol was 30 min. During the fifth minute of vibration 'with' and 'without' backrest support, participants performed maximal rhythmic hand grip contractions for 1 min. In general, erector spinae oxygenation and blood volume showed a trend to decrease with vibration exposure compared to the control condition. However, these responses were not influenced by the change in vibration frequency (P > 0.05). Sitting without backrest resulted in a greater decrease in oxygenation (by 27%, P = 0.02) and blood volume (by 11%, P = 0.05) than with backrest, implying a deficiency in oxygen supply owing to the sitting posture. Compared to the vibration-only condition, hand grip work decreased both oxygenation (by 22%, P = 0.003) and blood volume responses (by 13%, P = 0.04), suggesting that postural load due to prolonged sitting combined with physical activity during vibration might further burden paraspinal muscles. The influence of adipose tissue thickness of the lumbar muscle on optically derived oxygenation and blood volume changes was inconclusive.

Long-term repeatability of force, endurance time and muscle activity during isometric contractions

We determined the repeatability and correlations between force, endurance and muscle activity during isometric contractions over three years. Twenty-six subjects, with and without complaints of the shoulder and neck, performed standardized maximal and submaximal shoulder-abduction contractions and wrist extension-contractions at yearly intervals from 1997 to 1999. Peak forces developed during maximal contraction and the endurance times of submaximal contractions during shoulder abduction and wrist extension were measured. Electromyography (EMG) of muscle activity was recorded bilaterally from the upper trapezius, middle deltoid, and forearm extensor muscles. Root mean square EMG amplitudes were calculated. We found statistically significant associations between peak forces developed during wrist extension and shoulder abduction, and between endurance times of submaximal wrist extension and shoulder abduction. No statistically significant changes in peak force and EMG(peak) were found over the measurement years. The responses were not statistically significantly influenced by gender, or neck and shoulder pain. However, we observed considerable intra-individual variation in the inter-year measurements particularly for the responses to submaximal contraction. Such large variations represent a challenge when attempting to use the responses to interpret the effects of therapies.

Comparisons of physiological and perceptual responses in healthy men and women during standardized arm cranking and task-specific pushing–pulling

OBJECTIVE

Peak cardiorespiratory, metabolic, and perceptual responses in healthy men (n=11) and women (n=11) were compared during two different upper body exercise modes: standardized arm cranking and task-specific pushing-pulling.

METHODS

Each subject completed to volitional exhaustion both an incremental arm cranking and a pushing-pulling exercise continuously, in a random order, on two separate days. Physiological responses were monitored using an automated metabolic cart and a heart rate monitor, and the rating of perceived exertion was obtained using a 15-point Borg Scale.

RESULTS

Peak oxygen uptake, oxygen pulse, respiratory exchange ratio, and ventilation rate were higher and total exercise time to exhaustion was lower during arm cranking compared to pushing-pulling (P<0.05). However, heart rate was similar between exercise modes (P>0.05). Men showed greater physiological responses (absolute oxygen uptake, oxygen pulse, and ventilation rate) and longer exercise time to exhaustion than women (P<0.05). Power output during arm cranking was higher (by 79%) than pushing-pulling (P<0.01), with men demonstrating 30% greater values during both exercise modes (P<0.01). The lower power output generated during pushing-pulling resulted in a greater ratio of peak oxygen uptake to power output (by 72%; P<0.05). Interestingly, although power output and oxygen uptake were lower at the maximal workload, perceived exertion was higher (by 5%) during pushing-pulling (P<0.05).

CONCLUSIONS

Based on the physiological differences, pushing-pulling is found to be metabolically less efficient than arm cranking. However, greater ratings of perceived exertion during pushing-pulling implies that the perception of effort can also be influenced by a low intensity task, such as pushing-pulling, if performed for a prolonged period. Occupational health professionals should be aware of the limitations of utilizing physiological and perceptual responses obtained only from standardized ergometric protocols in predicting the workers' performance effectiveness.

Muscle strength and aerobic capacity in a representative sample of employees with and without repetitive monotonous work

OBJECTIVES

The purpose of the study was to determine a possible association between the type of work individuals perform and his or her physical capacity. There was focus on whether workers performing repetitive monotonous work differ from workers with varied work tasks with respect to the physical capacity.

METHODS

Maximal backward extension and forward flexion torques of the trunk, maximal shoulder elevation and abduction torques, handgrip strength and aerobic capacity were measured on 423 (213 male and 210 female) Danish employees with a mean age of 40 years. Half of the group had varied work and the other half had repetitive monotonous work.

RESULTS

The main finding was that there is no difference in the measured physical capacities between employees with repetitive monotonous work and those compared with workers with varied work tasks.

CONCLUSIONS

No difference in the physical capacities measured in the two groups of employees was found. Reasons for this are discussed.

Leisure time physical activity and strenuousness of work as predictors of physical functioning: a 28 year follow up of a cohort of industrial employees

AIMS

To examine associations of leisure time physical activity and physical strenuousness of work with physical functioning 28 years later.

METHODS

A cohort (n = 902) of metal industry employees was studied for exercise and housework activity in 1973 and 1978, and for BMI, current smoking, strenuousness of work, grip strength, and chronic diseases in 1973. Of the 670 survivors in 2000, 529 (79%) responded to all studied items in a follow up questionnaire including the SF-36 Physical Functioning (PF) scale. Belonging to the lower quartile of the PF scale denoted poor functioning.

RESULTS

Vigorous exercise and housework activity were inversely associated with poor PF 28 years later in both white-collar and blue-collar workers. Engaging in activities of any intensity was similarly associated among the blue-collar workers. In a multiple logistic regression model including as independent variables age, sex, occupational class, the number of chronic diseases, vigorous leisure time physical activity, BMI, physical work strenuousness, and smoking (all measured at baseline), the risk of poor PF at follow up was decreased by vigorous leisure time physical activity and increased by high physical strenuousness of work, high BMI, and smoking. The effect of work strenuousness was mainly due to that among the blue-collar group. Allowing for baseline grip strength did not materially alter the results.

CONCLUSION

Vigorous leisure time physical activity decreased the risk of poor physical functioning as perceived considerably later in life, while high work strenuousness, smoking, and overweight increased it. Among blue-collar workers a beneficial association was observed with all leisure time activity, including that of lower intensity.