Effect of treadmill speeds and slopes on voluntary exercise in rats

Male rats 87 days of age were given daily 90-minute sesions of voluntary exercise on self-operated treadmills pre-set to deliver speeds ranging from 6.1 to 73.2 m/minute and slopes of 0 to 27 degrees. Voluntary motivation to operate the treadmills was induced by maintaining the rats at constant body weights of 203 +/- 2 g. Under the conditions of the experiment, the rats selected 24.4 m/minute and 0 degree slope with running bursts averaging 21 to 24 seconds in duration as a preferred condition for greatest running. Since all activity was voluntary, the consistent patterns of running bursts at 24.4 m/minute are believed to be potentially capable of serving as reference baselines for detection of food contaminants, toxicants and other insults to normal metabolic processes.