Exercise-induced growth in golden hamsters: Effects of age, weight, and activity level

Abstract

The relationship between the exercise-induced growth and the endogenous controls of growth was examined in 356 golden hamsters of which equal numbers were given access to horizontal disc exercisers and maintained sedentary at different ages (17 and 42 days) and body weights (25-180 g). Hamsters started exercising around Day 35, increased their activity levels to 30,000 revolutions per day (RPD) by Day 35, and ran progressively less as their weight increased above 65 g. Exercise accelerated growth only in hamsters which have entered the slow asymptotic phase of growth, which weighed between 60-180 g and generated over 15,000 RPD. Disc exercise appears to reinstate higher rates of ponderal and linear growth after hamsters have entered the slow asymptotic phase of growth. Sustained inhibition of exponential growth may participate in the long-term regulation of body size in adult rodents.