Abstract
BackgroundInjury prevalence data commonly indicate trends of higher rates of work-related musculoskeletal disorders in older workers over their younger counterparts, and for females more than males. The purpose of this study was to investigate age and sex-related differences in manifestations of shoulder muscle fatigue in a cohort of young and older working age males and females, in a single experiment design allowing for direct comparison of the fatigue effects between the target groups.MethodsWe report upper trapezius muscle fibre Conduction Velocity (CV) as an indicative measure of muscle fatigability, and isometric endurance time, at three levels of shoulder abduction lifting force set relative to participants’ maximal strength.ResultsUpper trapezius conduction velocity was significantly different between the young and old groups (p = 0.002) as well as between males and females (p = 0.016). Shoulder abduction endurance time was affected by age (P = 0.024) but not sex (p = 0.170).ConclusionsThe study identified age-related improvement in muscle fatigue resistance and increased resistance for females over males, contrary to injury prevalence trends. The muscle fatigue effects are most likely explained by muscle fibre type composition. Experimental fatigue treatments of the upper trapezius were tested at exposures relative to the participants’ strength. Absolute strength is higher when young and is generally higher for males. The findings of this study point towards age and sex-related differences in strength rather than in muscle fatigue resistance as a primary cause for the differences in the injury trends.
Highlights
Injury prevalence data commonly indicate trends of higher rates of work-related musculoskeletal disorders in older workers over their younger counterparts, and for females more than males
The current study focuses on evaluating the latter explanation by measuring muscle fibre conduction velocity in a group of old and young participants
The second key strength of this study is the measurement of muscle fatigue via muscle fibre conduction velocity for the experimental fatigue conditions tested, and for a shoulder muscle commonly associated with Musculo-Skeletal Disorders (MSDs)
Summary
Injury prevalence data commonly indicate trends of higher rates of work-related musculoskeletal disorders in older workers over their younger counterparts, and for females more than males. The purpose of this study was to investigate age and sex-related differences in manifestations of shoulder muscle fatigue in a cohort of young and older working age males and females, in a single experiment design allowing for direct comparison of the fatigue effects between the target groups. Occupational injury and symptom prevalence data often indicate higher rates for older workers and for females [1, 2]. Collins and O’Sullivan [3] previously reported prevalence of neck/shoulder symptoms of Musculo-Skeletal Disorders (MSDs) for young and old age groups in a sedentary occupation, a trend described by others [4].
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