The Importance of the Training-Induced Decrease in Basal Cortisol Concentration in the Improvement in Muscular Performance in Humans

Abstract

Acute exercise-induced changes in cortisol concentration (C) and training related adaptation within hypothalamic-pituitary-adrenal (HPA) axis has been widely examined, but their influence on muscle strength performance is at best uncertain. Twenty four young healthy men were randomly assigned to an endurance training group (ET, n=12) or to a non-exercising controls (CON, n=12). ET performed supervised endurance training on cycle ergometer for 20 weeks. Endurance training program improved exercise capacity (14 % increase in power output generated at peak oxygen uptake – VO2peak), muscle strength performance (increase in MVC – maximal voluntary contraction – by 9 % and in TTF 50 % MVC – time to fatigue at 50 % MVC – by 21 %) and led to a decrease in basal serum C concentration (P=0.006) and an increase in basal testosterone to cortisol (T/C) and free testosterone to cortisol (fT/C) ratios (P=0.01 and P=0.02, respectively). It was found that the decrease in C concentration (ΔC) was positively correlated to the increase in local muscular endurance (ΔTTF 50 % MVC). No significant hormonal changes were seen in CON group. It is concluded that greater decrease in cortisol concentration after the endurance training is accompanied by poorer improvement in skeletal muscle performance in previously untrained subjects.

Lowered Serum Testosterone Concentration Is Associated With Enhanced Inflammation and Worsened Lipid Profile in Men

“…The data regarding the effect of exercise training on gonadal androgens in aging males are, however, inconsistent ( 52 , 53 ). Nevertheless, based on our earlier studies ( 20 , 26 , 54 , 55 ), we can suggest that the basal T and fT concentrations change in response to exercise training accordingly to the applied training load. Therefore, it can be postulated that a low-to-moderate training load leads to an increase in the T concentration ( 20 , 54 ), a moderate-to-heavy training load does not change it ( 26 ), and a heavy-to-maximal training load leads to a decrease in its concentration ( 55 ).…”

“…The data regarding the effect of exercise training on gonadal androgens in aging males are, however, inconsistent (52,53). Nevertheless, based on our earlier studies (20,26,54,55), we can suggest that the basal T and fT concentrations change in response to exercise training accordingly to the applied training load. Therefore, it can be postulated that a low-to-moderate training load leads to an increase in the T concentration (20,54) The training-induced changes in the androgen concentrations, regardless of whether they are related to the direct stimulation of the HPG axis or to the effects of body fat-androgens interactions, may be of great importance because we have demonstrated that they are inversely correlated with markers of inflammation and blood lipids (Figures 1 and 2).…”

“…SHBG measurement was standardized against the 1st International Standard for SHBG from the National Institute for Biological Standards and Control (NIBSC, code 95/560). Moreover, fT was calculated using the assumption-free empirical equations ( 25 ), as it was shown that this method is very useful in providing more detailed information about the androgen and anabolic/catabolic status of the body ( 26 ).…”

“…, a moderate-to-heavy training load does not change it(26), and a heavy-to-maximal training load leads to a decrease in its concentration(55). This concept was recently supported in the review by Matos et al(56), and it can also explain why Lovell et al(52) did not observe any changes in the resting T and fT concentrations during training of progressively increasing loads in older men, whereas Hayes et al(53) found enhanced basal T and fT concentrations after training of shorter durations and lower total loads (although partly of higher intensities).…”

A quantitative method for estimating the adaptedness in a physiological study

“…The latter premise has been suggested as a result of an analysis of experiments performed in different studies. Thus, for instance, it is known that trained athletes in response to intensive physical loads ( F ″) show higher cortisol secretion [22] mainly due to the decrease in post-training value ( F′ ) of basal secretion [23, 24]. Untrained people, however, did not display such increased secretion, or even showed a decline thereof.…”