Isokinetic pull-up strength profiles of men and women in different working posture

Dynamic and static shoulder strength relationship and predictive model

Static strength is typically used to standardize occupational tasks in an effort to limit over-exertion injuries; however, workplace tasks are commonly dynamic in nature. The purpose of this investigation was to assess factors influencing isokinetic shoulder strength and to develop predictive equations for isokinetic shoulder flexion and extension strength using isometric strength. Fifteen women performed a set of concentric isokinetic and isometric shoulder flexion and extension maximal exertions across a series of movement planes, angular velocities, and grip types. Data were used to generate two stepwise multiple regression models for predicting isokinetic shoulder flexion and exertion strength across the various exertion parameters. The final regression models explained a high degree of variance in predicting isokinetic shoulder flexion (R² = 0.59) and extension (R² = 0.67) with a subset of four and five inputs, respectively. The predictive equations can help establish acceptable force limits for workplace tasks requiring dynamic actions using more easily attainable static forces.

Is sitting worse than static standing? How a gender analysis can move us toward understanding determinants and effects of occupational standing and walking

The Yant Award was established in 1964 to honor the contributions of William P. Yant, the first president of the American Industrial Hygiene Association. It is presented annually for outstanding contributions in industrial hygiene or allied fields to an individual residing outside the United States. The 2014 award recipient is Dr. Karen Messing, Professor emeritus, Department of Biological Sciences, Université du Québec à Montréal and Researcher, CINBIOSE Research Centre. Gender (socially determined) differences in occupations, employment, and working conditions, task assignments, and work methods that affect exposure to health risks are increasingly documented. Interactions of (biologically influenced) sex differences with workplace parameters may also influence exposure levels. During field studies, ergonomists learn a lot about gender and sex that can be important when generating and testing hypotheses about the mechanisms that link workplace exposures to health outcomes. Prolonged standing is common in North America; almost half (45%) of Québec workers spend more than three-quarters of their working time on their feet and 40% of these cannot sit at will. This posture has been linked to chronic back pain and musculoskeletal disorders (MSDs) in the lower limbs, but many health professionals suggest workers should stand rather than sit at work. We ask: (1) Given the fact that roughly the same proportion of men and women stand at work, what does a gender-sensitive analysis add to our ability to detect and thus prevent work-related MSDs?; (2) How does ergonomics research inform gender-sensitive analysis of occupational health data?; and (3) What do researchers need to know to orient interventions to improve general working postures? We have sought answers to these questions through collaborative research with specialists in epidemiology, occupational medicine, biomechanics, and physiology, carried out in partnership with public health organisations, community groups, and unions. We conclude that failure to characterize prolonged static standing and to apply gender-sensitive analysis can confuse assessment of musculoskeletal and circulatory effects of working postures. We suggest that prolonged static sitting and standing postures can and should be avoided by changes to workplace organization and environments. Research is needed to define optimal walking speeds and arrive at optimal ratios of sitting, standing, and walking in the workplace.

Isokinetic pull strengths in the vertical plane: effects of speed and arm angle

The significance of knowing dynamic (isokinetic) strengths of individuals and the impact of selected individual and work-related factors on these strengths have been addressed in previous works. This follow-up study investigated the effects of pulling speed and angle of the preferred arm on isokinetic strengths of males and females in a vertical plane. The results indicated that speed of pulling has a major influence on strength exertion capabilities of people. Isokinetic strength exertions are maximum in the vertical plane but are smaller than isometric strength exertions in the vertical plane. As expected, men exerted greater force than females. Force exertions in the sitting and standing postures were not appreciably different from each other. RELEVANCE: Knowledge of strength exertion capabilities of individuals is necessary for designing work controls, and in assessing rehabilitative effects of physical therapy programmes. How the speed of motions and orientations of the arm influence strength can assist in designing work which is within the capability of the working population.