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Introduction: Work-related musculoskeletal disorders in the neck shoulder are known to be especially prevalent in women of higher age. But experimental studies examining the activity of the neck muscles and associations or interactions between age, gender, and work load are sparse. This study examined differences of upper trapezius muscle (UT) activity during a dual task in four groups of older and younger women and men.

Methods: Forty-eight volunteers attended an experimental study and were equally divided into four experimental groups (male and female and age range between 18–27 or 50–67 years). All 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.

Results: Despite high inter-individual variability in muscle activity, age and gender 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. Additionally, the UT was nearly constantly active in the older women group.

Discussion: It is striking that under these experimental conditions older women constantly activated parts of the UT while the younger subjects mostly kept the UT relaxed. This may be due to several reasons, e.g. altered physical capacity, cognitive processing ability or adaptation to the test situation.

Conclusion: Such exposures may be important in an aging workforce, and adapted work environments can help to prevent work-related musculoskeletal complaints.