Characteristics of growth-inducing exercise

Abstract

Characteristics of growth-inducing exercise in hamsters were studied by examining (a) dependence of this phenomenon on a specific activity device, (b) its species-specificity, and (c) features of the running pattern which produce optimal growth acceleration. Acceleration of growth by exercise occurs in hamsters running on either horizontal discs or in vertical wheels, and in gerbils running in rotating wheels, and is therefore neither device- or species-specific phenomenon. In contrast to the two rodent species demonstrating increases in the rate of weight gain at levels of voluntary activity between 10,000 and 30,000 RPD, rats running on either activity device, and gerbils and ground squirrels running on horizontal discs, generated low levels of activity and no evidence of increased somatic growth. At weight ranges associated with maximal acceleration of growth by disc exercise, hamsters ran at moderately high speeds of between 35 and 51 cm/sec for up to one hour without a pause. Their total daily activity exceeded 15,000 RPDs (5.9-8.5 km) and lasted between 5 and 10 hours. Prolonged voluntary activity at relatively low speed constitutes a sufficient condition for acceleration of somatic growth in two rodent species.