Melatonin and gonadotropin secretion after acute exercise in physically active males

Summary Serum concentrations of luteinizing hormone (LH), follicle stimulating hormone, testosterone (T) and melatonin were measured in seven physically active male volunteers after exercise on a treadmill using the Bruce protocol. Measurements were made on blood samples obtained before exercise, within 30 s after exercise, at 15 min after exercise, and subsequently at 30-min intervals after exercise for a total duration of 180 min. Serum LH concentration fell from a peak post-exercise level of 15.7 (4.7) IU·l^–1 [mean (SD)] to a nadir of 10.3 (2.4) IU·l^–1 (P<0.004). Nadir values in individual volunteers were seen between 60 and 150 min after exercise. This fall in serum LH was paralleled by a similar fall in the concentration of serum T. Serum melaonin concentrations did not change significantly after exercise. It is concluded that melatonin, despite is reported anti-gonadotropic properties, does not play a role in the depression of serum LH after acute strenuous exercise in physically active males     

Inhibin and gonadotrophin secretion in physically active males after acute exercise.

Serum concentrations of luteinizing hormone (LH) follicle stimulating hormone (FSH), testosterone and inhibin were measured in six physically active male volunteers after heavy exercise on a treadmill. Hormone measurements were made before exercise, immediately after exercise and at 30-min intervals for 3 h after exercise. Serum concentrations of LH fell after exercise reaching nadir values between 60 and 180 min post-exercise. The nadir value of LH for the group as a whole occurred 90 min after exercise. Serum testosterone concentrations paralleled the changes in LH concentrations. Serum FSH and inhibin concentrations did not show any appreciable change from baseline values. The data suggest that acute exercise does not significantly lower serum concentrations of FSH or inhibin. Whether repetitive and prolonged heavy exercise, as in competitive runners, produces alterations in serum inhibin concentrations remains to be determined.     

Plasma adrenocorticotrophin and cortisol responses to acute hypoxia at rest and during exercise

Summary Plasma adrenocorticotrophin (ACTH) and cortisol (F) concentrations were studied in six male subjects under normoxic (N) and acute hypoxic (H) conditions (altitude 3000 m) in a hypobaric chamber. Comparisons were made at rest, at 15, 30, and 60 min of exercise (65% ), and after a 10 min recovery period. Mean (±SE) resting plasma ACTH levels were significantly higher in H (18.6±5.7 pmol · l^–1) than in N (9.6±1.6 pmol · l^–1) but no difference in resting plasma cortisol was observed between the two conditions. Both plasma ACTH and F concentrations were significantly increased at 60 min of exercise and during the recovery period under normoxic conditions. Hypoxia did not affect the ACTH response to exercise but reduced cortisol elevation. The changes in plasma cortisol concentration from rest to exercise were significantly correlated to ACTH under normoxic (r=0.89,p<0.001) but not under hypoxic (r=0.43, NS) conditions. Plasma lactate concentration was higher at the end of exercise in hypoxia (p<0.01), and no correlation existed between plasma lactate and ACTH levels. These observations provide further evidence that at sea level the increase in plasma cortisol levels during exercise is the result of ACTH-induced steroidogenesis. The responses observed at rest and during exercise in hypoxia suggest that adrenal sensitivity for ACTH may be altered.     

β-Endorphin/β-lipotropin release and gonadotropin secretion after acute exercise in physically conditioned males

Summary β-endorphin (β-EP) andβ-lipotropin (β-LPH) concentrations were measured in the basal state and after acute exercise for 15 min or until exhaustion in 6 physically conditioned male volunteers. Serum concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone and prolactin were also measured in the basal state. In addition, the concentrations of the gonadotropins (LH and FSH) were determined after exercise and the gonadotropin response to gonadotropin releasing hormone was assessed before and after exercise. The data show that acute exercise stimulates the release of bothβ-EP andβ-LPH which return to base-line levels within 60 min after exercise. This is in contrast to our previously described results in physically unconditioned male volunteers in whom onlyβ-LPH release was noted after exercise. Serum LH concentrations declined after exercise reaching nadir values between 60 to 150 min after exercise. As we previously reported in physically unconditioned male volunteers, serum FSH concentrations did not change with exercise and the gonadotropin response to LRH stimulation was uninfluenced by exercise. Serum testosterone and prolactin concentration were within the normal range for healthy adult males. We speculate that the difference inβ-EP release with exercise in physically conditioned and unconditioned males represents a difference in processing of the opioid precursor molecule (pro-opiomelanocortin, POMC) in the two groups.     

Hormonal responses to high- and moderate-intensity strength exercise

The hormonal responses of nine male, strength athletes to strength exercise were examined. The athletes performed one moderate- and one high-intensity strength exercise workout. In the high-intensity workout, the load was 100% of each subject's three-repetition maximum (3-RM) for squats and front squats, and 100% of each subject's six-repetition maximum (6-RM) for leg extensions. In the moderate-intensity workout, the load was 70% of the high-intensity protocol. Rest periods between sets were 4–6 min for both workouts. Blood samples were taken before, 30 min into, and every 15 min for the 1st h after exercise, and then 3, 7, 11, 22 and 33 h after exercise, thus allowing examination of both the acute and prolonged hormonal responses. Blood samples were analyzed for testosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH), cortisol, adrenocorticotrophic hormone (ACTH), growth hormone (GH), insulin-like growth factor (IGF-1), insulin, sex hormone binding globulin, creatine kinase, total protein, glucose and lactate. The acute responses of testosterone and cortisol were greater during the high-intensity protocol as compared to the moderate-intensity protocol. The cortisol response was associated with an increase in ACTH concentration. LH and FSH showed no response to either protocol. Acute GH responses were not different between protocols. There were great inter-individual differences in acute GH responses to both protocols. There were no significant differences between protocols with regard to prolonged responses for any hormone. In both trials, IGF-1 concentrations were significantly lower at 0800 hours the morning after exercise as compared to concentrations found at 0800 hours the morning before exercise. The mechanisms responsible for reducing IGF-1 concentration in these trials are unclear, and it is not known if this reduction observed 22 hours after exercise is of physiological significance. Accepted: 13 December 1999     

Effect of physical training on the responses of serum adrenocorticotropic hormone during prolonged exhausting exercise

Summary The purpose of this study was to investigate the effects of physical training on the responses of serum adrenocorticotropic hormone (ACTH) and cortisol concentration during low-intensity prolonged exercise. Five subjects who had fasted for 12 h cycled at the same absolute intensity that elicited 50% of pre-training maximal oxygen uptake ( O_2max), either until exhaustion or for up to 3 h, before and after 7 weeks of vigorous physical training [mean daily energy consumption during training exercise, 531 kcal (2230 kJ)]. In the pre-training test, serum ACTH and cortisol concentrations did not increase during the early part of the exercise. Increases in concentrations of both hormones occurred in all subjects when blood glucose concentration decreased during the later phase of the exercise. The mean values and SEM of serum ACTH and cortisol concentrations at the end of the exercise were 356 ng · l^–1, SEM 79 and 438 g · l^–1, SEM 36, respectively. After the physical training, O_2max of the subjects improved significantly from the mean value of 50.2 ml · kg^–1 · min^–1, SEM 2.5 to 57.3 ml · kg^–1 · min^–1, SEM 2.0 (P < 0.05). In the post-training test, exercise time to exhaustion was prolonged in three subjects. Comparing the pre- and post training values observed after the same length of time that the subjects had exercised in the pre-training test, the post-training values of serum ACTH (44 ng · l^–1, SEM 3) and cortisol (167 g · l^–1, SEM 30) concentration were less than the pre-training value (P < 0.05). However, after the subjects stopped exercising in the post-training test, the serum ACTH (214 ng · l^–1, SEM 49) and cortisol (275 g · l^–1, SEM 50) concentrations were not significantly different from those measured after the subjects stopped exercising in the pre-training test (P > 0.10). In conclusion, high-intensity physical training reduced the responses of both hormones during prolonged exercise, propbably because of a delayed decrease of blood glucose concentration after physical training, while the level of the blood glucose concentration which induces ACTH and cortisol secretion did not change.     

Does functional alteration of the gonadotropic axis occur in endurance trained athletes during and after exercise?

In men, the hypothalamic-pituitary-testicular axis controls the secretion of testosterone which, in this sex, is a major anabolic hormone. Physical exercise modulates testosterone concentration, affecting the whole axis by poorly understood mechanisms. We have reported in this preliminary study the short and longterm effects of exercise on the function of the gonadotropic axis in trained compared to untrained subjects. Environmental factors known to interfere with pituitary function were minimized. Four marathon and four sedentary men, were studied during 5 days successively using different combinations of two factors: duration and intensity of running tests. Day 0 (DO) was a rest day, and the exercises were: D1 and D2 brief (20 min), light (50% maximal heart rate, HR_max, D1) or intense (80% HR_max, D2), D3 and D4 prolonged (120 min) and light (50% HR_max, D3) or intense (80% HR_max, D4). Testosterone (free and total) and luteinizing hormone (LH) concentrations were measured before, during and after exercise. The baseline concentrations of plasma testosterone were lower in the long distance runners than in the sedentary group [41.8 (SEM 5.5) vs 64.5 (SEM 7.9) pmol · 1^–1, respectively;P < 0.05]. This phenomenon was centrally mediated as LH concentration was apparentlyinappropriately low [3.4 (SEM 0.4) vs 4.3 (SEM 1.0) UI · 1^–1;P > 0.05]. Light to moderate exercise did not modify testosterone and LH concentrations. Conversely, intense and prolonged exercise increased testosterone concentration [73.2 (SEM 9.0) vs 92 (SEM 11.0) pmol · 1^–1 in the long distance runners and sedentary group, respectively;P < 0.05] and lowered LH concentrations [2.1 (SEM 0.3) vs 3.4 (SEM 0.3) UI · 1^–1 in the long distance runners and sedentary group, respectively;P <0.05 compared to DO, at the same time]. In our conditions of exercise, negative feedback of testosterone upon LH persisted, as positive feedback of low testosterone concentrations was apparently lacking (inappropriately low LH concentration with regard to low basal testosterone concentration).     

β-Endorphin and adrenocorticotrophin after incremental exercise and marathon running-female responses

Investigations of exercise-induced increases in -endorphin, adrenocorticotropic hormone (ACTH) and cortisol concentration have been carried out mainly in men. Data concerning the female reaction are sparse and less clear. In a comparison between incremental exercise and marathon running 14 experienced female marathon runners volunteered to run to exhaustion according to an incremental treadmill protocol. They ran a marathon 4 weeks later. Blood was analysed for -endorphin, ACTH and cortisol concentration immediately prior to the laboratory treadmill test, 3, 30 and 60 min later, as well as prior to the marathon, after 60 min and 120 min of running and 3, 30 min, and 24 h after completion of the run. At each blood collection, lactate concentration, heart frequency and perceived exertion were determined. The mean marathon running time was 3.22 h. Baseline concentrations for -endorphin of 22 pmol · l^–1 before the marathon and 19 pmol · l^–1 before the treadmill exercise increased 1.4-fold 30 min after the marathon and 1.9-fold after the treadmill exercise; for ACTH the baseline of 4.7 and 4.0 pmol · l^–1 t was increased by 8.3- and 10.3-fold, respectively. Cortisol concentration rose exponentially from a baseline 17 g · dl^–1 and peaked at 2.2-fold 30 min after the run, when the maximal concentration also had been reached after the treadmill test, increasing 1.3-fold from a baseline of 21 g · dl^–1. The maximal values for cortisol concentration after both exercises differed from each other, while the maxima of ACTH and -endorphin concentrations were similar. The ACTH and -endorphin concentration declined more slowly during the recovery after the marathon than after the treadmill. Cortisol concentration was below baseline 24 h later. In comparison with men studied earlier, female marathon runners showed higher baseline concentrations and lesser increases in -endorphin and lower baseline concentrations and larger increases in ACTH concentration after both types of exercise. The delayed decrease in concentration of the hormones after the marathon was similar in male and female runners.     

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·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·l^–1], while in the other 6 subjects (group B) a decrease or no change was seen [+3.1 (5.3) nmol·l^–1 ,between groups, P<0.05]. Growth hormone concentration was substantially higher in group A [+14.7 (4.8) ng·ml^–1] than group B [+6.0 (2.9) ng·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. Electronic Publication     

Thyroid and testicular hormone responses to graded and prolonged exercise in man

Eight men were studied during graded (47, 77 and 100% of maximal oxygen uptake) and prolonged (76%) exhaustive treadmill running. Plasma catecholamine levels increased progressively with intensity and duration of exercise. Serum concentrations of thyroid-stimulating hormone (TSH) increased with increasing work loads and were 107 (58–243)% (P<0.001) above resting values after maximal work. Thyroxine, triiodothyronine and luteinizing hormone in serum never changed significantly. While a small increase in testosterone concentrations (13 [1–24]%) after maximal exercise probably could be explained by changes in plasma volume, a definite increase (31 [14–56]%) occurred after 40 min of prolonged exercise. During continued exercise testosterone concentrations then gradually declined. Testicular stimulation by the increased catecholamine concentrations possibly contributed to the rise in testosterone concentrations, but no evidence was found for a direct catecholamine induced increase in the activity of the thyroid gland. The exercise induced increase in TSH levels possibly explains the increased thyroid hormone secretion rate, which previously has been found in individuals participating in physical training programs.     

Influence of exercise duration on post-exercise steroid hormone responses in trained males

The purpose of this study was to systematically evaluate the effect of endurance exercise duration on hormone concentrations in male subjects while controlling for exercise intensity and training status. Eight endurance-trained males (19–49 years) completed a resting control session and three treadmill runs of 40, 80, and 120 min at 55% of VO₂max . Blood samples were drawn before the session and then 1, 2, 3 and 4 h after the start of the run. Plasma was analyzed for luteinizing hormone (LH), dehydroepiandrosterone sulfate (DHEAS), cortisol, and free and total testosterone. LH was significantly greater at rest compared to the running sessions. Both free and total testosterone generally increased in the first hour of the 80 and 120 min runs and then showed a trend for a steady decline for the next 3 h of recovery. Dehydroepiandrosterone sulfate increased in a dose-response manner with the greatest increases observed during the 120-min run, followed by the 80-min run. Cortisol only increased in response to the 120-min run and showed a decline across time in all other sessions. The ratios of anabolic hormones (testosterone and DHEAS) to cortisol were greater during the resting session and the 40-min run compared to the longer runs. The results indicate that exercise duration has independent effects on the hormonal response to endurance exercise. At a low intensity, longer duration runs are necessary to stimulate increased levels of testosterone, DHEAS and cortisol and beyond 80 min of running there is a shift to a more catabolic hormonal environment.     

Effect of acute ether or restraint stress on plasma corticotropin-releasing hormone, vasopressin and oxytocin levels in the rat

Ether and restraint stress-induced peripheral plasma corticotropin releasing hormone (CRH), arginine vasopressin (AVP), oxytocin (OXY) and adrenocorticotropin (ACTH) levels were measured by radioimmunoassays. Plasma CRH, AVP, OXY and ACTH rose to approximately twice the level of control rats 2 min after the onset of a 1-min exposure to ether. Plasma CRH rose further 5 min after the onset of ether stress, while plasma AVP and OXY returned to the baseline levels at 5 min. Plasma CRH, OXY and ACTH showed significant elevation 2 min after the onset of restraint stress, while plasma AVP did not show a significant change. Plasma OXY and ACTH rose further 5 min after the onset of restraint stress, whereas plasma CRH returned to baseline levels. CRH and OXY concentrations in the hypothalamic median eminence decreased 5 min after the onset of ether exposure and restraint, while the AVP concentration did not differ from control levels. The results, including the discrepancy between plasma CRH and ACTH 5 min after stress, suggest that CRH in the peripheral plasma is derived from both hypothalamic and extrahypothalamic tissues. The levels of stress-induced CRH in the peripheral plasma were sufficient to stimulate ACTH release. These results suggest that ether and restraint stress elevate plasma CRH shortly after the onset of the stress, and that this elevation in the plasma CRH level is at least partly responsible for stress-induced ACTH secretion.     

Effect of anaerobic and aerobic exercise of equal duration and work expenditure on plasma growth hormone levels

Summary Growth hormone (GH) and lactic acid levels were measured in five normal males before, during and after two different types of exercise of nearly equal total duration and work expenditure. Exercise I (aerobic) consisted of continuous cycling at 100 W for 20 min. Exercise II (anaerobic) was intermittent cycling for one minute at 285 W followed by two minutes of rest, this cycle being repeated seven times. Significant differences (P<0.01) were observed in lactic acid levels at the end of exercise protocols (20 min) between the aerobic (I) and anaerobic (II) exercises (1.96±0.33 mM·l^–1 vs 9.22±0.41 mM·l^–1, respectively). GH levels were higher in anaerobic exercise (II) than in aerobic (I) at the end of the exercise (20 min) (2.65±0.95 g·l^–1 vs 0.8±0.4 g·l^–1;P<0.10) and into the recovery period (30 min) (7.25±6.20 g·l^–1 vs 2.5±2.9 g·l^–1;P<0.05, respectively).     

Plasma vasopressin,growth hormone and ACTH responses to static handgrip in healthy subjects

Summary Ten healthy male subjects took part in the study. They performed three consecutive bouts of static handgrip at 30% of maximal voluntary contraction (MVC), using two hands alternately and without rest intervals. Blood pressure was measured every 30 s and ECG was recorded continuously. Blood samples for arginine vasopressin (AVP), growth hormone (GH), adrenocorticotrophic hormone (ACTH) and cortisol determinations were taken at rest, after each exercise bout, as well as at 10 and 30 min after the last one. During the whole period of exercise (9 min) blood pressure and heart rate were elevated. The effort caused a significant increase in the plasma AVP concentration. In the majority of subjects the peak values occurred after the first or second exercise bout and were followed by a rapid decline of the hormone concentration. Changes in GH, ACTH and cortisol concentrations were insignificant; however, in seven of the ten subjects, considerably elevated plasma GH levels were found at the end of the third exercise bout and/or 10 min after its cessation.     

Effects of a rapid change in muscle glycogen availability on metabolic and hormonal responses during exercise

Summary To evaluate the metabolic and hormonal adaptations following a rapid change in muscle glycogen availability, 14 subjects had their muscle glycogen content increased in one leg (IG) and decreased in the other (DG). In group A (n=7), subjects exercised on a bicycle ergometer at 70% maximal oxygen uptake for 20 min using the DG leg. Without resting these same subjects exercised another 20 min using the IG leg. Subjects in group B (n=7) followed the same single-leg exercise protocol but in the reverse order. In order to get some information on the time sequence of these possible adaptations, blood samples were collected at rest and at the beginning and the end of each exercise period (min 5, 20, 25, and 40). Results indicated that 5 min after the switch from the DG leg to the IG leg. transient increases in plasma free fatty acids (1.20 to 1.39 meq·l^–1) and serum insulin (10.1 to 12 mU·l^–1) concentrations occured. Between minute 25 and 40 of exercise, the DG to IG switch was accompanied by a decrease in free fatty acids and glycerol concentrations as well as an increase in lactate levels. An opposite response was observed in the IG to DG condition during the same time span. Plasma norepinephrine, epinephrine, glucagon, and serum cortisol concentrations were not significantly affected by the leg change. These results suggest a rapid preferential use of muscle glycogen when available and a time lag in the response of the extramuscular substrate mobilization factors.     

Cortisol,testosterone, and insulin action during intense swimming training in humans

An increase in the amounts of circulating plasma cortisol or a decrease in testosterone can result in whole-body insulin resistance. The purpose of this study was to determine if the increase in cortisol and/or decrease in testosterone concentrations commonly evident with intense endurance training is associated with insulin resistance. Male (n = 9) and female (n = 10) swimmers were examined during the off-season, after 9 weeks (9 WKS) of training averaging 5,500 m·day^–1 and after an additional 9 weeks (18 WKS) of training averaging 8,300 m·day^–1. Resting plasma cortisol concentration was (P <– 0.05) higher in the women compared to the men at 9 WKS; values were not significantly different between genders at 18 WKS. Plasma testosterone concentration decreased significantly (P <– 0.05) in the men at 9 and 18 WKS, but did not change in the women. Whole-body insulin action, as determined by insulin and glucose responses during a 120 min, 75-g oral glucose tolerance test, did not change with training in either the men or women. These data indicated that plasma testosterone concentration can decrease in male swimmers during intense endurance training; this alteration does not affect whole-body insulin action. There would also appear to be a gender-specific response of plasma cortisol to endurance training, which does not influence insulin action.     

Effects of atrial natriuretic factor on anterior pituitary hormone secretion in normal man

Summary The effects of intravenous human atrial natriuretic factor ANF(99-126) administration on anterior pituitary hormone secretion have not been extensively investigated in humans. We repeatedly studied 10 healthy volunteers (5 female, 5 male, aged 28±2 years) on 2 occasions, 3 days apart. In randomized, single blind order, subjects received pretreatment with either placebo or intravenous ANF(99–126) (bolus 100 g/kg, 30-min infusion of 0.1 g/kg-min). Subsequently, on both occasions subjects received a combined intravenous bolus injection of pituitary releasing hormones (200 pg thyrotropin releasing hormone, 100 g gonadotropin releasing hormone, 50 g growth hormone releasing hormone and 100 g human adrenocorticotropin releasing hormone; Bissendorf, Hannover, FRG). Plasma concentrations of adrenocorticotropic hormone (ACTH), cortisol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), growth hormone (GH), thyrotropin (TSH), prolactin, ANF and cyclic guanosine monophosphate (GMP) were determined by radioimmunoassay. ANF(99–126) treatment induced a significant reduction in basal ACTH plasma concentrations and tended to decrease basal plasma cortisol. The TSH response to combined releasing hormone administration was significantly diminished after ANF(99-126) pretreatment. In women, the releasing hormone induced prolactin increase was reduced after ANF(99–126) pretreatment. With the present study design, ANF(99–126) did not alter the basal or releasing hormone stimulated plasma concentrations of cortisol, LH, FSH and GH. Releasing hormone administration did not affect ANF and cyclic GMP plasma levels. In humans, effects of natriuretic peptides on anterior pituitary hormone secretion may have to be considered with investigational or therapeutic administration of ANF analogues or agents interfering with the ANF metabolism.Abbreviations ANF(99–126) human atrial natriuretic factor - ACTH adrenocorticotropic hormone - LH luteinizing hormone - FSH follicle-stimulating hormone - GH growth hormone - TSH thyrotropin - PRL prolactin - cyclic GMP cyclic guanosine monophosphate - TRH thyrotropin releasing hormone - GnRH gonadotropin releasing hormone - GHRH growth hormone releasing hormone - CRH adrenocorticotropin releasing hormone     

Pituitary–adrenal responses to arm versus leg exercise in untrained man

The purpose of this study was to examine pituitary–adrenal (PA) hormone responses [beta-endorphin (β-END), adrenocorticotropic hormone (ACTH) and cortisol] to arm exercise (AE) and leg exercise (LE) at 60 and 80% of the muscle-group specific VO₂ peak. Eight healthy untrained men (AE VO₂ peak=32.4±3.0 ml kg⁻¹ min⁻¹, LE VO₂ peak=46.9±5.3 ml kg⁻¹ min⁻¹) performed two sub-maximal AE and LE tests in random order. Plasma β-END, ACTH and cortisol were not different (P>0.05) between AE and LE at either exercise intensity; the 60% testing elicited no changes from pre-exercise (PRE) values. For 80% testing, plasma β-END, ACTH and cortisol were consistently, but not significantly, greater during LE than AE. In general, plasma β-END and ACTH were higher (P<0.05) during 80% exercise, than PRE, for both AE and LE. Plasma cortisol was elevated (P<0.05) above PRE during 80% LE, and following 80% for both AE and LE. Plasma ACTH was higher (P<0.05) during 80% LE and AE versus 60% LE and AE, respectively. Plasma β-END and cortisol were significantly higher during and immediately after 80% LE than 60% LE. Thus, plasma β-END, ACTH and cortisol responses were similar for AE and LE at the two relative exercise intensities, with the intensity threshold occurring somewhere between 60 and 80% of VO₂ peak. It appears that the smaller muscle mass associated with AE was sufficient to stimulate these PA axis hormones in a manner similar to LE, despite the higher metabolic stress (i.e., plasma La^-) associated with LE.     

Serum hormones and physical performance capacity in young boy athletes during a 1-year training period

Summary Serum hormones and physical performance capacity in boy athletes (AG;n = 19) were investigated during a 1-year training period (between the ages of 11.6 and 12.6 years). Six young untrained boys served as the control group (CG). The mean serum testosterone concentration increased significantly in AG (P<0.05) following the training period from 2.92 nmol·l^–1, SD 1.04 to 5.81 nmol·l^–1, SD 1.33. Significant differences were not observed in the cortisol, sex hormone binding globulin and growth hormone levels during the follow-up period. The AG clearly increased speed (P<0.001), speed-strength (P<0.01-P<0.001) and anaerobic capacity (P<0.001) whereas CG had only slight increases (NS) in physical performance capacity during a 1-year period. During the last 6-month training period significant positive correlations (r=0.490–0.58;P<0.05 -P<0.01) were observed in AG between the relative changes in testosterone, testosterone: cortisol ratio and growth hormone and the relative performance change in speed, maximal isometric force and endurance, respectively. At the end of the period significant positive correlations were observed in all subjects between the level of testosterone and speed-strength (r=0.52–0.64;P<0.01 -P<0.001) and anaerobic capacity (r=0.49;P<0.05). It was concluded that an increase in anabolic activity with the synchronous training already has positive effects on trainability and physical performance capacity at an early stage in puberty.     

Glucocorticoid response to exercise as measured by serum and salivary cortisol

Summary Serum and salivary cortisol concentrations were studied in 78 elite athletes engaged in different sports, by subjecting them to high-intensity laboratory exercise. The mean difference in the pre-exercise cortisol concentrations in the seven groups studied were more marked in serum (from 311 to 768 nmol · l^–1) than in saliva (from 17.9 to 22.7 nmol · 1^–1, only one group reaching 40 nmol ·^–1). Judging from the correlation coefficients based on total variances, the post-/pre-exercise differences in cortisol concentrations in serum depended chiefly on pre-exercise values, while those in saliva tended to depend more on the postexercise concentrations. The coefficients of correlation between that difference and either the pre- or postexercise values were –0.71 and 0.47, respectively, for serum, and –0.51 and 0.58, respectively, for saliva. This would suggest that salivary cortisol concentration might be a more suitable variable for assessing glucocorticoid activity in exercise than serum cortisol concentration, probably being less sensitive to pre-exercise emotional state.