Effects of musculoskeletal work load and muscle strength on strain at work in women and men aged 44 to 58 years.

The effects of musculoskeletal work load and muscle strength on strain at work were analysed among 60 women and 69 men (mean age 52 +/- 3.4) in municipal jobs in Finland. The musculoskeletal work load was determined by analysing the jobs by a job description method. The maximal isometric hand grip strength was assessed with a manometer, trunk flexion and trunk extension strength with a dynamometer, and dynamic trunk flexion endurance strength with a sit-up test. Heart rate was registered continuously and ratings of perceived exertion were determined 4 times during the work shift. The results revealed that high musculoskeletal work load was systematically and significantly related to high strain at work in both sexes. A high mean heart rate related to an individual's range in women was an interaction effect of high work load and low hand grip strength or low trunk flexion strength. Among men, both high mean and maximal heart rates in relation to the heart rate range was due to the interaction effects of high work load and low trunk extension strength. The interaction of work load and strength was not systematically related to the ratings of perceived exertion during work. It was concluded that the musculoskeletal work load exerted the main effects on the cardiorespiratory and perceived strains at work. The interaction effects of work load and strength on strain depended on the sex and the muscle group in the studied work load level of elderly municipal employees.