Effect of chronic exercise on adrenocortical function and structure in the rat

exercise on adrenocortical function and structure in the rat. J. Appl. Physiol. 3 l(6) : 880-883. 197 1.-The effect of chronic exercise on plasma corticosterone and on the adrenal cortex was studied in the rat. Groups of male rats were exercised on a treadmill for 2, 4, 6, and 8 weeks. Chronic exercise was found to increase the resting levels of plasma corticosterone after 2 and 4 weeks. After 6 weeks these levels returned to near normal and were normal after 8 weeks. Both the trained and control rats after 8 weeks had similar high levels of corticosterone after an exhaustive exercise bout. The response of the adrenal cortex to exercise was similar to that of other stressors. The adrenal cortex was still responsive after long-term chronic exercise even though the plasma corti-costerone levels were low at rest. The width of the zona fasciculata of the adrenal cortex increased significantly in trained rats and was responsible for the adrenal hypertrophy and the increase