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...
Nineteen untrained preadolescent males (11-13 years old) were randomly placed into an experimental trained group (STG, n = 9) and a control group (n = 10). Informed consent was obtained from the children and their parents. The STG was submitted to a 2-month resistance-training program (6 exercises, 3 x 10 repetitions maximum [RM], 3 times per week), followed by a 2-month detraining program. The effectiveness of the resistance program was determined by measuring pre- and posttraining and detraining differences in isometric and isotonic (10RM) strength and hormonal responses in testosterone (T), sex hormone binding globulin, and free androgen index (FAI). Their maturation stage was evaluated according to Tanner. Significant posttraining isometric strength gains (17.5%) and mean T and FAI value increases (p < 0.05-0.001) were observed in STG. Detraining resulted in a significant loss (9.5%, p < 0.001) of isometric strength whereas the hormonal parameters of STG remained practically unaltered. The relative (delta%) postdetraining hormonal responses correlated significantly with the respective isometric strength changes. In conclusion, the resistance training induced strength changes independent of the changes in the anabolic and androgenic activity in preadolescent males. Further research is needed to fully clarify the physiological mechanisms underlying the strength training and detraining process.
SummaryBlood coagulation and fibrinolysis were assessed in 13 Finnish amateur runners aged 31 to 48, and one 65-year old taking part in a non-competitive marathon (42.2 km). After the run the mean values of partial thromboplastin time showed a very significant shortening, whereas the mean values of the prothrombin time and of plasma fibrinogen were not significantly altered. The mean values of euglobulin lysis time were significantly shorter and the mean values of fibrin degradation products increased highly significantly. After the run, protamine sulphate was positive or strongly positive in all subjects, whereas the ethanol gelation test was negative in all runners; no cryofibrinogen was detected in any participant. Thus, running a marathon race affects the haemostatic balance and activates the fibrinolytic mechanism. The effects of training and physical fitness on the above parameters are discussed.
Blood cortisol, ACTH, thyroxine, triiodothyronine, reverse triiodothyronine, thyroid stimulating hormone (TSH) and vasopressin concentrations were determined in 9 runners (29\p=n-\56 years old) and one 80year old man taking part in a non-competitive Marathon in Athens, Greece on October 1976. After the run the mean concentrations of cortisol, ACTH and vasopressin showed a significant rise. The thyroid function variables and TSH did not differ from the control values. There was a significant correlation between the cortisol and ACTH levels after the race and also between their increments from the corresponding base values. A significant correlation was found between the physical fitness (as measured by indirect determination of Vo2max) and the post-race cortisol levels. One of the well trained runners with a fairly good running time had the highest post-race values for 6 of 7 hormones studied.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.