Effect of Training on Plasma Anabolic and Catabolic Steroid Hormones and Their Response During Physical Exercise

Abstract

27Moderate physical exercise does not cause any changes in the plasma levels of the catabolic hormone cortisol and the anabolic hormone testosterone compared with the concentrations during a control day. In studies on army recruits, however, fit compared to unfit men tended to have smaller mean decreases in plasma testosterone and free testosterone index during the day both during a control day and during a day with submaximal marching exercise. After 4 months training, the mean plasma testosterone and free testosterone index tended to decrease less during both control and marching exercise days, and this was more evident in the well-conditioned subjects. However, very fit male athletes, who have been training for many years, and sedentary men have identical plasma testosterone levels and serum sex hormone binding globulin binding capacities (SHBG). Intense physical exercise invariably leads to an increase in plasma cortisol and a decrease in plasma testosterone compared with the concentrations during a control day. However, the percentage of free testosterone seems to increase cornpensatorily, which in many individuals keeps the absolute free testosterone level constant or even higher despite no change or slight increase in SHBG. Prolonged exhaustive physical exercise in men results in a decrease in plasma testosterone even down to normal female levels, and there is a constant increase in SHBG resulting in very low free testosterone concentrations. It is known from studies in rats that a low level of androgens results in an increase in the binding of cortisol in muscle tissue probably due to an increase in the number of cortisol receptors. This in combination with the high level of cortisol during prolonged exhaustive physical exercise may lead to a situation in which the protein catabolic events in the muscle cells supersedes the anabolic ones. Rats trained on a treadmill and sedentary rats have identical plasma and testicular testosterone concentrations, identical plasma LH levels, and training has no effect on Leydig cell LH and prolactin receptors. When these rats ran until exhaustion, the trained rats were able to run much longer (up to 3 h) than the untrained rats. In this experiment, the decrease in plasma testosterone was greater in the trained rats compared with the untrained ones, and also the testicular concentration of testosterone, androstenedione, and progesterone fell to lower levels in the trained rats after the exhaustive exercise. The plasma LH levels remained unchanged. This suggests that the decrease in plasma testosterone is due to a reduction in testicular testosterone production and a depletion of the testosterone stores and that the testosterone-LH feedback mechanism is no longer functioning in these exhausted animals. However, when the Leydig cells were incubated in vitro with HCG at different concentrations, it could be shown that in trained rats Leydig cell testosterone and cyclic AMP production was significantly greater than in sedentary rats. All these results are in good agreement w...

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