Motor Hyperactivity Resulting in Diameter Decrease of Peripheral Nerves1

Summary. Two groups of guinea‐pigs were subjected to intense motor training. Fibre spectra of one unimodal and one bimodal nerve were recorded after training periods of 11 and 29 days, respectively. The data recorded show that a significant decrease in fibre diameter can be produced by hyperactivity. The mechanisms underlying the present findings are discussed. It is suggested that the consumption of substances in the processes may be so great on intense activity that it cannot be completely compensated by synthesis, thus resulting in a decrease in fibre diameter.