Leisure and muscular performance in health and disease : a study of 40-64-year-old northern Swedes

Sammanfattning: Categories and frequencies of leisureactivities employed by 156 randomly selected males and females aged 40-44, 50-54, 60-64 were investigated by structured interviews and were related to leisuresatisfaction, to experienced health and socio-economic status. In equal numbers (15) of males and females from each group and in 24 males (60 +_6 years) with intermittent claudication (Cl) isokinetic plantar flexion performance was investigated with registrations of peak torque (PT), contractional work (CW), active range-of-motion (RoM) and integrated electromyograms from all threee triceps surae heads. Subjects performed a few maximum plantarflexions at different velocities of angular motion and also up to 200 consecutive plantar flexions at 60 °/s. The males aged 40-44 were re -investigated after two years additionally using electromyographic power frequency analyses.Leisure choice was mainly age and sex independent and extensively included outdoor activities. Leisure satisfaction was positively associated with relative frequency of activities. Symptoms of bodily discomfort, in particular backpain, were quite common and apparently caused relatively low level of mutual leisure activities. Thus, with in this age span, leisure activities appear rather rigid but often successfully, adhered to . Common ailments influence partnership mutuality negatively.Plantar flexion PT and CW are adequately p re dicta ble by sex, age and crural circumference. Uniformly a 3:2 male/female ratio characterizes mechanical output and iEMG. The latter is velocity independent. Output decreases with increasing age. Hence the output/excitation balance (CW/iEMG) is age, but not sex, dependent. CI-patients produce less PT and CW than do controls. Independently of this disease, of age and sex, PT and CW describe parallel negative exponential functions of velocity.During repeated manoeuvres plantar flexion output and iEMG initially drop, there after to maintain nearly steady-state levels. Throughout up to 200 contractions CW/iEMG was unaltered in the clinically healthy. Test/re-test with two years interval yielded nearly identical results. Leftshifts in mean power frequency in parallel with output-drop imply that the latter probably is due to FT-motor unit fatigue. For CW, but not for PT, the drop became slower and the (relative) steady-state level higher with increasing age, indicating significant increase in endurance with age. In the Cl-patients, output, but not excitation, decreased after a few repititions. Therefore, CW/iEMG fell dramatically, implying intramuscular fatigue. Taken together with findings of close associations between total cumulated work and measured/expected maximum walking tole rance it is suggested that measurements of CW and calculations of CW/iEMG are of clinical value.