Cortisol--essential adaptation hormone in exercise.
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Adaptation, Physiological↗
Biomedical subjects
M Viru
Publications and source records attributed to M Viru.
Influence of prolonged continuous exercise on hormone responses to subsequent exercise in humans.
This study examined the possibility that fatigue may modify the hormone responses to exercise. A group of 12 endurance trained athletes ran for 2 h (blood lactate concentrations of approximately 2 mmol x l(-1)) in order to induce fatigue. The subjects exercised for 10 min at 70% maximal oxygen uptake before (1st test) and after (2nd test) the 2 h run to assess hormone responsiveness. A 1 min anaerobic power test was performed to assess muscle power. Cortisol, growth hormone, testosterone and insulin concentrations were determined before and after the 1st and 2nd tests. The 1st test resulted in increases in concentrations (P < 0.05) of cortisol and growth hormone, a decrease in insulin concentration (P<0.01) and no change in testosterone concentration. The 2 h run caused decreases of insulin, increases of growth hormone concentration and variable responses in the concentrations of cortisol and testosterone. The 2nd test decreased insulin concentration further (P < 0.05), but responses of the concentrations of testosterone, growth hormone and cortisol were variable. In 6 subjects (group A) cortisol displayed an increase [mean (SD)] from baseline concentrations [+ 304.0 (60.0) nmol x l(-1)], while in the other 6 subjects (group B) a decrease or no change was seen [+ 3.1 (5.3) nmol x l(-1), between groups, P<0.05]. Growth hormone concentration was substantially higher in group A [+ 14.7 (4.8) ng x ml(-1)] than group B [+ 6.0 (2.9) ng x ml(-1)] following the 2nd test. In group A anaerobic muscle power was higher, while in group B it was lower, after the 2 h run than before the 2 h run (P < 0.05). The findings suggest that fatigue from prolonged endurance activity may introduce a resetting in the pituitary-adrenocortical component of the endocrine system, expressed either by intensified or by suppressed endocrine functions.
Adult↗
Hormonal responses to whole-body vibration in men.
The aim of this study was to evaluate the acute responses of blood hormone concentrations and neuromuscular performance following whole-body vibration (WBV) treatment. Fourteen male subjects [mean (SD) age 25 (4.6) years] were exposed to vertical sinusoidal WBV, 10 times for 60 s, with 60 s rest between the vibration sets (a rest period lasting 6 min was allowed after 5 vibration sets). Neuromuscular performance tests consisting of counter-movement jumps and maximal dynamic leg presses on a slide machine, performed with an extra load of 160% of the subjects body mass, and with both legs were administered before and immediately after the WBV treatment. The average velocity, acceleration, average force, and power were calculated and the root mean square electromyogram (EMGrms) were recorded from the vastus lateralis and rectus femoris muscles simultaneously during the leg-press measurement. Blood samples were also collected, and plasma concentrations of testosterone (T), growth hormone (GH) and cortisol (C) were measured. The results showed a significant increase in the plasma concentration of T and GH, whereas C levels decreased. An increase in the mechanical power output of the leg extensor muscles was observed together with a reduction in EMGrms activity. Neuromuscular efficiency improved, as indicated by the decrease in the ratio between EMGrms and power. Jumping performance, which was measured using the counter-movement jump test, was also enhanced. Thus, it can be argued that the biological mechanism produced by vibration is similar to the effect produced by explosive power training (jumping and bouncing). The enhancement of explosive power could have been induced by an increase in the synchronisation activity of the motor units, and/or improved co-ordination of the synergistic muscles and increased inhibition of the antagonists. These results suggest that WBV treatment leads to acute responses of hormonal profile and neuromuscular performance. It is therefore likely that the effect of WBV treatment elicited a biological adaptation that is connected to a neural potentiation effect, similar to those reported to occur following resistance and explosive power training. In conclusion, it is suggested that WBV influences proprioceptive feedback mechanisms and specific neural components, leading to an improvement of neuromuscular performance. Moreover, since the hormonal responses, characterised by an increase in T and GH concentration and a decrease in C concentration, and the increase in neuromuscular effectiveness were simultaneous but independent, it is speculated that the two phenomena might have common underlying mechanisms.
Adult↗
Improvement of motor abilities in pubertal girls.
BACKGROUND: Purpose of the study was to test the hypothesis that in the course of sexual maturation possibilities for accelerated development of motor abilities are triggered in girls. METHODS: A cross-sectional study was conducted on 77 healthy 11- to 14-year-old girls, grouped according to Tanner's 5-stage scale of sexual maturation. Motor abilities were assessed with the aid of 20 m dash, 4 x 9 m shuttle run, standing long jump, squats in 30 sec, sit ups in 30 sec, trunk forward flexion, Cooper 12-min running test, and Harvard step-test. RESULTS: Performance in the shuttle run, standing long jump and trunk forward flexion improved in correlation with sexual maturation stage. When consecutive maturation groups were compared, in standing long jump and trunk forward flexion significant differences were found between sexual maturation stages II and III, in shuttle run between stages I and II. The significant main effect of sexual maturation was confirmed with the aid of MANOVA. 23% of variance in the results of trunk forward flexion, 17% in standing long jump, and 10% in shuttle run were attributable to maturation differences. For the same three motor tasks 4%, 8%, and 15%, were respectively attributed to age differences. Differences between maturation groups disappeared when the results of shuttle run and standing long jump were adjusted with the aid of ANCOVA for age or height as the covariate, but persisted after results were controlled for body mass. CONCLUSIONS: The results support the tested hypothesis. Critical for improvement of agility is reaching maturation stage II, and for increase of leg muscle explosive strength and trunk flexibility, reaching stage III.
Adolescent↗
Exercise-induced hormone responses in girls at different stages of sexual maturation.
The dependence of exercise-induced hormone responses on sexual maturation was tested in a 3-year longitudinal experiment on 34 girls (aged 11-12 years at the beginning). Sexual maturation was evaluated by Tanners five-stage scale. Children cycled for 20-min at 60% maximal oxygen uptake once a year. Cortisol, insulin, growth hormone, beta-oestradiol, progesterone and testosterone concentrations in venous blood were determined by radioimmunoassay procedures. Basal concentrations of growth hormone increased and of cortisol decreased when breast stage III was reached. Reaching breast stage IV was associated with an increase in basal concentrations of beta-oestradiol, progesterone and testosterone. The exercise induced significant increases in concentrations of cortisol, growth hormone and beta-oestradiol and a decrease in insulin concentration. At breast stage III the increase in cortisol concentration was to a lower level [467 (SEM 42) vs 567 (SEM 46)nmol x l(-1)] and growth hormone concentration to a higher level [29.4 (SEM 0.5) vs 12.8 (SEM 0.4)ng x ml(-1)], while the fall in insulin concentration was less pronounced [postexercise level 10.6 (SEM 0.9) vs 7.8 (SEM 0.8)mU x l(-1)] than in stage II. The magnitude of the cortisol response was reduced in the last stage of breast development (+42.1% vs +55.5% at stage II, +66.2% at stage III, and +50.0% at stage IV). The magnitude of beta-oestradiol response was the lowest in breast stage IV (+15.8%) and the highest at stage V (+41.1%). The progesterone response became significant at stage IV and testosterone response at stage V. In conclusion, we found that reaching breast stage III was associated with altered responses of cortisol, insulin and growth hormone concentrations while the responses of the sex hormone concentrations became pronounced in the last stages of sexual maturation.
Adolescent↗
Effect of restricted blood flow on exercise-induced hormone changes in healthy men.
To test the influence of the accumulation of metabolites on exercise-induced hormone responses, plasma concentrations of cortisol, growth hormone (GH), insulin, testosterone, thyrotropin (TSH), free thyroxine (fT4) and triiodothyronine (T3) were compared during exercise performed under normal conditions (control) and under conditions of restricted blood flow of exercising leg muscles (ischaemia) in nine healthy young men. Blood supply was reduced by 15%-20% by the application of 50 mmHg external pressure over the exercising leg. During 45-min cycling exercise during ischaemia the increase in GH concentration was twice as large as under normal conditions. Despite the below-threshold exercise intensity for activation of the pituitary-adrenocortical system under normal exercise conditions ischaemic exercise elicited cortisol and T3 responses (concentration increases of 83% and 9.5%, respectively). Ischaemic exercise attenuated the decrease of plasma insulin concentration found under normal conditions. The concentrations of testosterone, TSH and fT4 were not changed significantly during exercise performed in either condition. The results support the suggested essential role of muscle metaboreceptors in the control of hormone responses during muscle activity.
Adolescent↗
Effect of oral creatine supplementation on jumping and running performance.
The study was designed to investigate the effect of creatine monohydrate ingestion (20 g daily for 5 days) on performance in 45 s maximal continuous jumping and in all-out treadmill running at 20 km x h(-1), (inclination 5 degrees, duration approximately 60s). The participants were qualified sprinters and jumpers. The effect of creatine was compared with placebo in a double-blind design. Creatine (Cr) supplementation led to a significant enhancement of performance capacity in the jumping test by 7% during the first 15 s and by 12% during the second 15 s of the exercise. The positive effect of Cr supplementation was not observed in the last third of the continuous jumping exercise, when the contribution of anaerobic metabolism was decreasing. The time of intensive running up to exhaustion improved by 13%. The results show that Cr supplementation helps to prolong the time during which the maximal rate of power output could be maintained.
Adult↗
Hormonal responses in strenuous jumping effort.
In order to test the possibility for rapid responses of blood hormone levels in short-term supramaximal exercises, serum concentrations of corticotropin (ACTH), cortisol (C), total testosterone (tT), free testosterone (fT), growth hormone (GH), thyrotropin (TSH), free thyroxine (fT4), free triiodothyronine (fT3), prolactin (PRL), insulin-like growth factor (IGF-I), and sex hormone-binding globulin (SHBG) were determined by RIA procedures in blood samples obtained before and immediately after a 60-s period of consecutive vertical jumps (Bosco test). The study subjects were 16 Italian professional soccer players. Immediately after exercise, significant increases (p < 0.05) were found in the concentrations of ACTH (by 39%), C (by 14%), TSH (by 20%), fT3 (by 28%), fT4 (by 30%), tT (by 12%), fT (by 13%), and SHBG (by 21%). Significant changes were not detected in the blood levels of GH, IGF-I and PRL. Most pronounced testosterone responses were typical for persons of high jumping performance (the increase of serum tT correlated with average power output, r = 0.61 and jumping height, r = 0.66). The larger the drop in power output during 60-s jumping, the higher was the thyroid response: the difference in jumping height between the first and last 15-s period correlated with increases in TSH (r = 0.52) and in fT4, (r = 0.55). In conclusion, the obtained results indicate that in intense exercise, causing the rapid development of fatigue, rapid increases in serum levels of hormones of the pituitary-adrenocortical, pituitary-gonadal and pituitary-thyroid systems occur.
Adrenocorticotropic Hormone↗
Glucocorticoids in metabolic control during exercise: alanine metabolism.
To evaluate glucocorticoid participation in the control of alanine metabolism during exercise, experiments were performed on adrenalectomized and normal male rats. The adrenal insufficiency prevented the rises induced by 3 h of swimming in alanine levels of blood plasma, red portion of quadriceps, and liver. In normal rats, the rise in alanine content by 65% in blood, 50% in fast-twitch oxidative fibers, and 93% in liver was associated with increased activity of alanine aminotransferase in fast-twitch oxidative-glycolytic fibers (by 23%). In adrenalectomized rats, enzyme activity during exercise did not change in muscles and decreased in hepatic tissue (by 25%). The dependence of exercise-induced changes in alanine aminotransferase activity on glucocorticoids was confirmed by an increased enzyme activity (by 53%) in exercised adrenalectomized rats treated with 125 micrograms corticosterone. In normal rats, training prevented both the rise of blood corticosterone and the activation of hepatic alanine aminotransferase during exercise. The results support the view that the stimulation of the glucose-alanine cycle by glucocorticoids promotes alanine supply and utilization in liver during exercise. In adrenalectomized rats, hepatic arginase activity was decreased during exercise and no elevation of urea levels was found in blood, liver, or skeletal muscles. Consequently, the use of products of the deamination of alanine (and other amino acids) for urea formation also depends on glucocorticoids.
Adrenalectomy↗
Development of ischemic contracture in isolated skeletal muscles: relation to the capacity for anaerobic glycolysis.
In order to evaluate the dependence of the rate of ischemic contracture development in isolated skeletal muscles on the capacity for anaerobic glycolysis, factors affecting ischemic contracture development were examined using rat soleus and quadriceps muscles. The contracture developed faster in slow-twitch oxidative (SO) fibers than in fast-twitch glycolytic (FG) fibers. In both types of fibers, the rate of contracture development was inversely related to the medium pH. Addition of lactate increased the rate of contracture development. In FG fibers, the lactate level during contracture was directly, and the glycogen level inversely, proportional to the medium pH. An increase in muscle lactate level by 4-h swimming accelerated the contracture development, and reduced further lactate accumulation during contracture. Types of exercise training known to influence the capacity for anaerobic glycolysis (interval training and repeated fast climbing and swimming) decreased the velocity of contracture development. Isoprenaline administration in vivo accelerated contracture development in association with reduced lactate level during contracture. Swimming training counterbalanced the action of isoprenaline. Adrenalectomy accelerated contracture development in SO fibers, and decreased lactate accumulation during contracture in FG fibers. In adrenalectomized rats, the effects of exercise were more pronounced in SO fibers than in FG fibers. These results indicate that the rate of contracture development in isolated skeletal muscle is inversely related to the capacity for anaerobic glycolysis.
Adrenalectomy↗
Glucocorticoids in metabolic control during exercise: glycogen metabolism.
In order to evaluate the participation of glucocorticoids in the control of glycogen metabolism during exercise, experiments were performed on male adrenalectomized and normal rats. In adrenalectomized rats swimming for 4 hours induced less pronounced increases in lactate concentrations in skeletal muscles than in normal rats (in FG fibers up to 10.7 +/- 1.0 vs 14.8 +/- 1.2 and in SO fibers up to 9.1 +/- 0.7 vs 12.5 +/- 0.7 mg x g-1 wet tissue). The glycogen drop in liver and oxidative muscles was also less pronounced (in liver by 14% vs 52%, in SO fibers by 33% vs 54% in normal rats). Swimming until exhaustion led to an extremely low glucose level in blood (1.89 +/- 0.12 mMol x L-1) in adrenalectomized rats. When they were treated with dexamethasone, the swimming duration was longer (12 +/- 1 hours vs 9 +/- 0.8 hours in saline treated), blood glucose level at exhaustion was higher (3.07 +/- 0.23 mMol x L-1) and the drop of hepatic and muscle glycogen was more pronounced. In normal rats hepatic glycogen content dropped by 68% after swimming for 4 hours. After swimming for 8 or 12 hours further decreases in hepatic glycogen content were insignificant. High levels of corticosterone in blood was found after swimming for 4 and 8 hours. After swimming for 16 hours corticosterone concentration was below normal and a new drop in liver glycogen (until a level constituting only 11% initial) was recorded. The results support the suggestion that glucocorticoids, regulate hepatic glycogen and peripheral glucose utilization during exercise, and also participate in the control of glycogenolysis in muscles.
Adrenal Glands↗
Differences in effects of various training regimens on metabolism of skeletal muscles.
The purpose of the study was to detect the specific nature of the action of various training regimens on glycogen, activities of phosphofructokinase (PFK) and myofibrillar Ca(2+)-ATPase, and Ca2+ accumulation by the sarcoplasmic reticulum in muscle fibers of various types. Models of sprint, interval or aerobic continuous running training for 10 weeks, as well as a model of fast strength training (repeated fast clambering up a slope of 80 degrees) and swimming training for 6 weeks were applied in Wistar rats. Most of the training regimes used caused increases in glycogen content both in the soleus muscle (SO) by 29 ... 199% and in the white part of the quadriceps muscle (FG) by 37 ... 65%. Only sprint training was ineffective in both muscles and aerobic running in FG fibers. All training regimes, including sprint training, increased the glycogen content of the sarcoplasmic reticulum (SPR). A significant suppression of PFK activity was found 48 hours after interval or aerobic running in both muscles and after sprint running in the soleus (by 26 ... 62%). However, 4-min highly intensive test running (60 m.s-1) resulted in 2-3 fold increases in PFK activity of both muscles in rats trained by interval or continuous running but not in sprint trained and sedentary animals. It was suggested that training in intensive interval running or aerobic running enhances the sensitivity of PFK both to inhibitory and activating influences. The activity of Ca(2+)-ATPase increased as a result of sprint, interval, continuous running and strength training and decreased in result of continuous swimming. The rate of Ca2+ accumulation by SPR increased with sprint, interval, aerobic running and fast strength training in SO and with fast strength training in FG fibers.
Aerobiosis↗
Exercise-induced catabolic responses in various muscle fibres.
In Wistar rats a 10-hr swim caused an immediate increase of 3-methylhistidine and free tyrosine content in the white portion of quadriceps muscle. In the red portion the elevated levels of these amino acids were observed within 6 to 48 hrs of postexercise recovery. The glycogen depletion was substantially higher in the red portion of the muscle, indicating that the most active were oxidative-glycolytic fibres during the exercise. In conclusion, during exercise the most active muscle fibres do not contribute to the mobilization of protein resources. In a later part of postexercise recovery, catabolic changes occur in most active fibres, constituting, reasonably, a part of enhanced protein turnover.
Animals↗