Title: Effect of Acute Exercise on Glycogen Levels in Adrenalectomized Rats1
Abstract: In animal and human populations the resting level of muscle glycogen is an important determinant of an exercise response. Since the hormonal mechanisms are obscure, the effectof a single bout of exercise on muscle and liver glycogen levels was studied in adrenalectomized, adrenaldemedullated, and sham-operated Sprague-Dawley rats. Plasma FFA levels, 11-OHCS levels and blood glucose values were also measured in rats who were approximately 50 days old at the time of surgery. One week after surgery, the animals were “exhausted” by running on a treadmill for 60-70 min at grades between 0-15% and speeds ranging from 8.8 to 22.8 m⁄min. The plasma 11-OHCS and FFA levels indicated that the surgical and exercise procedures were effective and strenuous. Resting muscle glycogen results from nonexercised animals showed that the adrenal-demedullated group had the highest concentration of all groups.Immediately after exercise,liver and muscle glycogen stores were significantly reduced in every group whilethe plasma FFA levels were increased in the shamoperated and adrenal-demedullatedanimals, Blood glucose was elevated in only the sham-operated animals. Forty-eight hr following exercise, tissue glycogen levels had returned to control levels, as had plasma FFA and bloodglucose values. Food consumption on the day following the exercise bout was markedly reduced in the threegroups thatdid not receive injections of steroids. However, by the second postexercise day, food consumption had returned to their pre-exercise levels in all groups. There was no statistical evidencefrom the postexercise animals to indicate that a single exhaustive bout of exercise had produced elevated levels of muscle glycogen (supercompensation). The results emphasize the physiological importance of the adrenal hormones in the response to exercise and in the recovery fromexercise. (Endocrinology95: 1385 1974)