Adaptation to Forced Exercise in the Rat

¹ From the Department of Physiology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina

The influence of forced exercise (treadmill running) on food intake, body weight and spontaneous activity was studied in male albino rats. The initial response to gradually increasing exercise load was a decrease in food intake and body weight on exercise days, with compensatory increase in both factors on rest days (week-ends). By the time exercise had been increased to 1 mile/day, food intake on exercise days had returned to normal or slightly above, and food intake on rest days was significantly elevated. During the recovery period following the exercise experiment, food intake remained elevated despite the absence of a significant weight deficit. Overnight spontaneous activity was strikingly reduced in exercised rats, with only partial restoration on rest days, and with gradual return to normal during the postexercise recovery period.