Neuromuscular function in weight-trainers.

Electrophysiologic measurements were made on the median-innervated thenar muscles and triceps surae in 17 weight-trainers (bodybuilders and weight-lifters) and in control subjects. In the median-innervated thenar muscles, the weight-trainers presented normal values for motor unit counts, reflex potentiation, and twitch contractile properties; however, the weight-trainers possessed a significantly greater (8%) median motor nerve conduction velocity. In the triceps surae, the weight-trainers exhibited significantly greater reflex potentiation (70%), which was interpreted as an increased ability to activate motor units during maximal voluntary contractions. Peak twitch tension (16%) and twitch contraction time (20%) of the triceps surae were significantly greater in the weight-trainers, whereas their twitch half-relaxation time and soleus motor unit counts were not significantly different from control values. The observed difference may reflect a combination of genetic endowment and the effects of training.