THE EFFECTS OF CHRONIC EXERCISE ON METABOLIC AND REPRODUCTIVE FUNCTIONS IN MALE RATS

Previous studies concerning the effects of swimming on various endocri ne gland functions have been performed (4,6). Our study was thus desig ned to analyze the effects of chronic exercise (swimming) on the resti ng metabolic rates (RMR) of adult rats. Most of the protocols used a w ater temperature of 33 C. It is our contention that such a protocol is not exclusively an exercise stress, but also a hypothermic stress (10 ) The protocol of our study was designed in a way that hypothermic str ess was not part of the exercise stress. Male rats were swam in 36 C w ater for 3 hours a day, 5 days a week for 4 months. RMR of the animals were determined 24 h after the next to last swim session. Plasma horm one levels and epididymal sperm concentrations were determined in anim als sacrificed 24 h after the last swim period. Exercising animals had a RMR 16% greater than that of control animals (p < 0.02), yet total and free thyroxine and total and free triiodothyronine were not signif icantly elevated. Neither plasma testosterone nor epididymal sperm cou nts were significantly reduced in the exercising animals. It appears t hat chronic exercise produces an elevation in RMR which is unrelated t o thyroid gland activity and does not suppress the hypothalamic-pituit ary-gonadal axis.