Endurance training in females: changes in beta-endorphin and ACTH

Previous results from endurance training in women have been discrepant in regard to influences on basal and maximum adrenocorticotropin (ACTH) and beta-endorphin (beta-EP) concentrations before and after exhaustive exercise. A group of 23 untrained young women ran 3 times a week for 30 min at an individual specific intensity corresponding to their respective anaerobic threshold, derived from the lactate performance curve obtained from prior treadmill testing. ACTH and beta-EP were measured at rest, as well as 5 and 30 min after exhaustive progressive spiroergometric treadmill running, both before and after the 8 week endurance training program. Basal beta-EP did not change after training, but less elevated concentrations were measured both 5 (p < 0.05) and 30 min (p < 0.05) after exercise, after the training program. In contrast, the resting concentration of ACTH increased significantly; the respective maximum concentration was less elevated after 5 min and much less elevated 30 min after the exercise (p < 0.05). Positive correlations were found after the exhaustive exercise between beta-EP and ACTH, as well as between maximum lactate and ACTH. Training was associated with significant changes in maximum running speed (p < 0.01), maximum oxygen uptake (p < 0.01) and the running speed at the anaerobic threshold (p < 0.05). Maximum lactate and the level of perceived exertion remained unchanged, showing a similar level of exhaustion. Our results indicate that endurance training modulates the hormonal responses of beta-EP and ACTH to comparable workloads of high intensity. After the training program the maximum concentrations are significantly lower during the recovery period. The tendency to elevated basal ACTH, and thus elevated cortisol, might be a new factor to consider in evaluation of endurance training induced hormonal disturbances in women.