Effects of aerobic training on reactive capacity: an animal model.

Young (120 day) and Old (500 day) Sprague-Dawley rats were divided into four groups: Young exercisers, young control, old exercisers, and old controls. All animals were shaped, over a 7-day period, on an escape and avoidance task that produced very rapid responses ranging from 100 to 200 msec in the shortest CS-UCS intervals. Both the young and old exercise groups aerobically trained for 6 months by running daily on a rodent treadmill up to 1 hour. Aerobic training effects, measured by oxygen consumption per gram of gastrocnemius-plantaris muscle tissue revealed that the exercise groups were well trained, expressed by a 71% and 97% increase in oxygen utilization by the young and old groups respectively. Reactive capacity results revealed that on some variables the old trained animals were faster in both escape and avoidance responses than the old control animals. The shorter the CS-UCS interval, the greater the differences were between the age groups and the trained and control animals. The aerobic training main effect was significant after 3 months of training as well as after 6 months. Viable mechanisms to explain the results are discussed.