Bilateral trapezius activity during a dual task depends on age and sex - Results of an experimental laboratory study

Despite strong associations between prevalence rates of musculoskeletal complaints in the neck-shoulder area and age and sex, studies examining the dependence on muscular strain on these factors are sparse. During a dual task, simulating repetitive moderate- and low-force work under cognitive demands, the study examined upper trapezius muscle (UT) activity in four equal-sized groups representing older and younger women and men. All 48 participants completed four 30-minute dual-task conditions of two levels of muscular load (mean 5%/10% maximum force) combined with an easy or difficult cognitive load. The dual tasks combined force tracking requiring intermittent isometric contractions of wrist muscles with a concurrent memory task. Surface electromyography was bilaterally applied to the UT to derive activity levels and the relative rest time during the conditions. Despite high interindividual variability in muscle activity, age and sex had statistically significant effects on activity levels of both sides. Older women had higher levels compared to younger men, independent of conditions (p < 0.01), which was supported by descriptive trends of less relative rest time, particularly on the inactive non-dominant side. Nearly constant and elevated UT activity was seen notably in older women. In an aging workforce, this may be relevant to prevent work-related musculoskeletal complaints.