ELECTRICALLY-EVOKED TORQUE-VELOCITY CHARACTERISTICS AND ISOMYOSIN COMPOSITION OF THE TRICEPS SURAE IN YOUNG AND ELDERLY MEN

The electrically evoked isokinetic torque-velocity relationship of the triceps surae of eight elderly and four non-trained young men was exa mined in relation to the isomyosin composition of the soleus and the g astrocnemius muscles, determined under non-denaturing conditions using pyrophosphate gel electrophoresis. The angle specific torque-velocity properties of the triceps surae were measured using maximal percutane ous electrical stimulation at 50 Hz and a release technique. The elder ly subjects generated significantly (P < 0.05) less absolute torque at all angular velocities when compared with the young subjects. When th e isokinetic data were normalized to the isometric torque, the lower n ormalized torques generated by the elderly subjects were not statistic ally different from the young. The total fast isomyosin (FM) content o f the soleus and gastrocnemius in the elderly subjects was 22 +/- 13 a nd 35 +/- 18%, respectively. This compared with 29 +/- 8 (n.s.) and 44 +/- 8% (n.s.) in the young subjects. When the gastrocnemius and soleu s muscles were given an equal weighting and considered together to rep resent the whole triceps surae, the normalized torque at the fixed ang ular velocity of 5 rad s(-1) was significantly associated with %FM (I = 0.90, P < 0.01), and the isomyosin bands %FM1 (r = 0.90, P < 0.01) a nd %FM2 (r = 0.93, P < 0.001) when only the elderly subjects were cons idered. No relationships were observed between contractile characteris tics and contractile protein profile when only the young subjects were considered. This was despite the inclusion of a further two sprint an d three endurance trained athletes to increase the range of contractil e characteristics and differences in muscle composition.