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).     

Effect of high intensity interval training on 2,3-diphosphoglycerate at rest and after maximal exercise

Summary The purpose of this study was to examine the effect of intense interval training on erythrocyte 2,3-diphosphoglycerate (2,3-DPG) levels at rest and after maximal exercise. Eight normal men, mean ± SE=24.2±4.3 years, trained 4 days·week^–1 for a period of 8 weeks. Each training session consisted of eight maximal 30-s rides on a cycle ergometer, with 4 min active rest between rides. Prior to and after training the subjects performed a maximal 45-s ride on an isokinetic cycle ergometer at 90 rev·min^–1 and a graded leg exercise test (GLET) to exhaustion on a cycle ergometer. Blood samples were obtained from an antecubital vein before, during and after the GLET only. Training elicited significant increases in the amount of work done during the 45-s ride (P<0.05), and also in maximal oxygen uptake ( max: Pre=4.01±0.13; Post=4.29±0.07 l·min^–1;P<0.05) during exercise and total recovery (Pre=19.14±0.09; Post=21.45±0.10 l·30 min^–1;P<0.05) after the GLET. After training blood lactate was higher, base excess lower and pH lower during and following the GLET (P<0.05 for all variables). Training caused no significant differences in erythrocyte 2,3-DPG levels at rest (Pre=11.8±0.7; Post=12.1±0.7 mol·g^–1 hemoglobin (Hb);P>0.05), at exhaustion (Pre=12.0±0.8; Post=11.2±0.8 mol·g^–1 Hb;P>0.05) or during 30 min of recovery from the GLET. Additionally, acute exercise (pre-training GLET) did not effect any change in 2,3-DPG at exhaustion or during recovery from exercise compared to resting values. The higher max and total recovery values observed after training appear to be unrelated to 2,3-DPG levels. Under the present conditions, the role, if any, of 2,3-DPG in enhancing tissue oxygenation during increased metabolic demand remains obscure.Supported by grants from Miles Laboratories, Elkhart, Indiana, and the Ball State Graduate Student Research Fund     

Chemiluminescence response of granulocytes from elite athletes during recovery from one or two intense bouts of exercise

In this study nine elite athletes each participated in three different 24- h trials, as follows: (1) complete bed rest (REST), (2) one bout of exercise at 1515 hours (ONE-EX), (3) two exercise bouts, one at 1100 hours and one at 1515 hours (TWO-EX-3 h), and (4) two exercise bouts, one at 0800 hours and one at 1515 hours (TWO-EX-6 h). Exercise was performed on a cycle ergometer with 10 min of warm-up and then 65 min at an exercise intensity of 75% of maximum oxygen uptake (V˙O_2max). The polymorphonuclear neutrophil (PMN) counts increased consistently in response to exercise, and more in trial TWO-EX-3 h than in the two other exercise trials (P<0.01). The respiratory burst of PMN was measured as chemiluminescence (CL), obtained with phorbol myristate (PMA) and serum-opsonised zymosan (SOZ) as stimulators. Exercise triggered the CL response for a defined number of PMN, significantly above baseline (REST) values (P<0.05) for ONE-EX and TWO-EX-3 h, but not for TWO-EX-6 h. The strongest response was observed for TWO-EX-3 h, but the difference between exercise procedures was not significant. However, as a novel approach, a comparison was made using total oxidative potentials per litre of blood, as obtained by combining CL values and PMN numbers. TWO-EX-3 h yielded significantly higher values than the other experimental treatments. Thus, by this measure the total oxidative potential of PMN·l^–1 blood remains at a higher level with short intervals between exercise bouts (i.e. 3 h instead of 6 h), possibly due to a combined effect of cell number increase and the priming state of PMN. This may suggest that for intensive training twice a day, a recovery phase of 5–6 h is preferable. The elevation in cell number is best explained by a combined effect of catecholamines and cortisol. Growth hormone is one probable candidate as a stimulator of CL, but other molecular participants that respond to exercise may exert roles as either stimulators or inhibitors of CL. Electronic Publication     

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).     

Kinetics of plasma potassium concentrations during exhausting exercise in trained and untrained men

The purpose of this study was to examine the time course of changes in plasma potassium concentration during high intensity exercise and recovery in trained and untrained men. The subjects performed two exercise protocols, an incremental test and a sprint, on a cycle ergometer. A polyethylene catheter was inserted into the antecubital vein to obtain blood samples for the analysis of plasma electrolyte concentrations and acid-base parameters, during and after exercise. During both tests, venous plasma sodium, potassium and chloride concentrations increased in all the subjects, although the largest relative increase was detected in potassium concentration - 35% and 31% over rest in the progressive test and 61% and 37.7% in the sprint test, for cyclists and controls, respectively. After exercise plasma potassium concentration decreased exponentially to below resting values. There was a linear correlation between the amount of potassium accumulated in plasma during exercise and the amount eliminated from plasma when the exercise ceased. We found that, although plasma potassium accumulation occurred in both forms of exercise in the trained and nontrained subjects, the time constant of potassium decrease following exercise was shorter in the trained subjects. Thus, the trained subjects exhibited a better capacity to recover to resting concentrations of plasma potassium. We propose that the extracellular potassium accumulation acts as a negative feedback signal for sarcolemma excitability depending on the muscle metabolic rate.     

Regulation of growth hormone during exercise by oxygen demand and availability

Summary Five normal men performed seven sets of seven squats at a load equal to 80% of their seven repetition maximum. Plasma growth hormone (GH) and lactate levels increased during and after the completion of the exercise. A significant (r=0.93, P<0.001) linear correlation was found between GH changes and the corresponding oxygen Demand/Availability (D/A) ratio expressed by (where f=[lactate at time x]/[lactate at time 0]). A retrospective examination of previously published data from our laboratory and others also demonstrated the existence of a significant correlation between changes in plasma GH levels and the D/A ratios over a wide variety of exercise; aerobic and anaerobic, continuous and intermittent, weight lifting and cycling, in both fit and unfit subjects under normoxic and hypoxic conditions. It is suggested that the balance between oxygen demand and availability may be an important regulator of GH secretion during exercise. DCIEM No. 87-P-27     

Growth hormone and prolactin response to rehydration during exercise: effect of water and carbohydrate solutions

Summary The effect of progressive rehydration with either water or a carbohydrate solution on the plasma growth hormone (GH) and prolactin (PRL) response to exercise was examined together with plasma somatostatin. Five subjects underwent four 3-h experimental sessions at 36°C in which 25-min exercise periods alternated with 5-min rest periods. The sessions were conducted without fluid replacement (DH) or under rehydration with either water or isosmotic carbohydrate solutions AISO (acid) or NISO (neutral). The fluid was given every 10 min after the 1st h of exercise. Plasma GH increased significantly (p < 0.01) under DH after 2 and 3 h of exercise; this increase was prevented by rehydration with water, AISO and NISO. Plasma glucose was significantly higher following AISO and NISO rehydration compared with DH. This possibly influenced the GH response, but there was no difference between plasma glucose levels under DH and water rehydration at any time. The solutions tended to attenuate the increase in heart rate, rectal temperature and plasma cortisol, suggesting that the lack of GH response under rehydration conditions is a result of decreasing physiological stress levels. The GH response could not be explained by plasma somatostatin, which tended to decline in all sessions. Plasma PRL did not increase in any of the sessions, confirming that exercise without rehydration is a more potent stimulator of GH than of PRL. It is concluded that progressive rehydration with water is sufficient to prevent the exercise-induced increase in plasma GH.     

Variation of soluble transferrin receptor and ferritin concentrations in human serum during recovery from exercise

Serum soluble transferrin receptor (sTfR) has been proposed as a more stable index of iron status than serum ferritin in athletes. However, the variation in sTfR concentration during recovery from acute exercise is unknown. The aim of the present study was to examine the effect of prolonged moderate exercise on ferritin and sTfR concentrations, as well as on several hematologic variables up to 24 h post-exercise. Fifteen young, untrained men exercised on a cycle ergometer for 45 min at a heart rate of 150–155 beats min⁻¹ and provided blood samples before as well as immediately, 6 h, and 24 h after exercise. Ferritin and sTfR values did not change significantly with time. sTfR levels exhibited lower variation during the observation period, the median intra-individual coefficient of variation being 5.2%, as opposed to 10.9% for ferritin. In conclusion, serum ferritin concentration is not affected by prolonged moderate exercise and can be used as a reliable index of iron status, at least for athletes not involved in extreme physical activities. Serum sTfR concentration seems to be more stable and could replace ferritin as the preferred index of iron stores if problems associated with the novelty of the assay were overcome. Electronic Publication     

Steroid and pituitary hormone responses to rowing: relative significance of exercise intensity and duration and performance level

Summary To analyse the relative significance of exercise intensity and duration as well as of performance capacity, hormone changes were recorded in 16 male rowers in two experiments separated by a year. The test exercises consisted of 7-min (at the supramaximal intensity) and 40-min rowing (at the level of the anaerobic threshold) on a rowing apparatus. In addition, somatotropin and cortisol responses were estimated in rowing for 8 × 2000 m in 14 rowers of national class. All three tests caused significant increases in somatotropin and cortisol concentrations in the blood. Follitropin concentrations were elevated in the 7-min exercise test in the second experiment and in the 40-min exercise test in both experiments. Lutropin and progesterone concentrations increased during the more prolonged exercise in the first experiment. No common change was found in testosterone concentrations. Cortisol and somatotropin responses to the 40-min rowing test at anaerobic threshold were more pronounced than to the 7-min exercise test at supramaximal intensity. When the rowers achieved a national class level of performance (the second experiment) the hormone responses to 7-min supramaximal exercise were increased. During the 8 × 2000-m rowing test cortisol but not somatotropin concentration increased to an extremely high level in the rowers of national class. It is concluded that in strenuous exercise cortisol and somatotropin responses were triggered by the exercise intensity threshold. The exact magnitude of the response would seem to have depended on additional stimuli caused by exercise duration and on possibility of mobilizing hormone reserves.     

Renal handling of salt and water in humans during exercise with or without hydration

Plasma sodium (Na⁺) concentration, i.e. natraemia, results from body tonicity equilibrium. During exercise, a change in body tonicity can result from an imbalance between intake and loss of Na⁺, potassium (K⁺) and water (H₂O) due to renal and/or extra-renal mechanisms. Whether exercise-induced changes in kidney function could be responsible for such an imbalance was studied by measuring glomerular filtration rate (creatinine clearance), proximal tubule activity (lithium clearance) and renal handling of Na⁺ and K⁺ at rest and during exercise. Since hyponatraemia during or after exercise has been reported, we also investigated whether a water load could be appropriately excreted during exercise. Ten young men pedalled on a cycle ergometer at 60% of maximal oxygen uptake for 45 min with (HE, hydrated exercise) or without (DHE, dehydrated exercise) a supply of water. In both conditions, creatinine, lithium, and electrolyte (Na⁺+K⁺) clearances decreased and natraemia did not change. The DHE induced a loss of body mass (–1.29%), decreased diuresis and large extra-renal water loss [mean (SEM)] [880 (73) ml]. The HE led to no loss in body mass, increased diuresis and lower extrarenal water loss [680 (48) ml]. Electrolyte-free water excretion, negative for DHE, represented 60% of diuresis during HE. Thus the kidney, by increasing electrolyte reabsorption mainly in the proximal tubule, and appropriately excreting a water load, seems efficacious in regulating extracellular fluid volume and body tonicity and so not responsible for the imbalance between (Na⁺+K⁺)/H₂O intake and loss. Therefore, extra-renal changes could be the main causes of exercise-induced tonicity imbalances which could ultimately lead to dysnatraemia. Electronic Publication     

Self-assessment of somatic and psychic symptoms during a two months period of hormone replacement therapy in perimenopausal women

Summary The drastic decrease in sex steroids production at menopause is often related to the development of somatic and psychic symptoms in women. We examined the effects of a two months hormone replacement therapy (HRT) on weekly self-assessments of menopausal symptoms, mood and sleep disturbances. In addition, spatial perception and motor performances abilities were measured before and after 8 weeks of HRT. Twentythree healthy perimenopausal women (mean 50 ± 4.8 years of age) with no previous hormone therapy and a Kuppermann-Index ≥15 were included. Before therapy and in weekly intervals during two months of treatment women reported upon their menopausal symptoms (MENOI), their mood state (POMS) and sleep disturbances (VISM). Psychological examinations were done before HRT and two months later under hormone replacement therapy. All 23 patients showed a significant improvement of the self report of climacteric, affective symptoms and of sleep disturbances, and a tendency to improvement in cognitive performance with respect to pretreatment measures. This indicates that hormone replacement therapy in perimenopausal women is associated with clinical improvement in somatic and psychic symptoms and a cognitive enhancement in some aspects. These benefits of the HRT must play a role in cost-effectiveness analyses of HRT.     

Influence of exercise intensity on time spent at high percentage of maximal oxygen uptake during an intermittent session in young endurance-trained athletes

The purpose of this study was to compare, during a 30s intermittent exercise (IE), the effects of exercise intensity on time spent above 90% and time spent above 95% in young endurance trained athletes. We hypothesized that during a 30sIE, an increase in exercise intensity would allow an increase in due to a decrease in time to achieve 90% or 95% of Nine endurance-trained male adolescents took part in three field tests. After determination of their and maximal aerobic velocity (MAV), they performed, until exhaustion, two intermittent exercise sessions alternating 30s at 100% of MAV (IE₁₀₀) or 110% of MAV (IE₁₁₀) and 30s at 50% of MAV. Mean time to exhaustion (t _lim) values obtained during IE₁₀₀ were significantly longer than during IE₁₁₀ (p < 0.01). Moreover, no significant difference was found in expressed in absolute or relative (%t _lim) values between IE₁₀₀ and IE₁₁₀. In conclusion, an increased of 10% of exercise intensity during a 30s intermittent exercise model (with active recovery), does not seem to be the most efficient exercise to solicit oxygen uptake to its highest level in young endurance-trained athletes.     

Endocrine and follicle characteristics of cycles with and without endogenous luteinizing hormone surges during superovulation induction with pulsatile follicle-stimulating hormone

The induction of superovulation in women with human gonadotrophinsmay result in blockage of the endogenous luteinizing hormone(LH) surge, but the reasons for this are not known. Ten normallyovulating women with longstanding infertility volunteered forthis study. They were treated with 225 IU follicle-stimulatinghormone (FSH) daily s.c. in a pulsatile manner (28 IU every3 h) starting on cycle day 2. Serum FSH and oestradiol levelsincreased and serum LH levels decreased significantly duringthe FSH treatment, as compared to their spontaneous cycles.Only five women displayed an LH surge during the FSH treatment.Serum FSH and LH levels during treatment were significantlylower and the number of follicles 12–15 mm in diameterand their total fluid volume was significantly greater in thecycles without an endogenous LH surge. Basal LH levels in thecycles without an LH surge increased soon after the end of theFSH treatment (cycle day 18), while FSH levels were still verylow without any incremental tendency. These results suggestthat a high number of small follicles may have a suppressiveeffect on both tonic and mid-cycle gonadotrophin secretion.Furthermore, the LH suppressive mechanism seems to be differentfrom that of the FSH.     

Pregnancy and birth after high serum progesterone concentrations during the follicular phase in an in-vitro fertilization cycle with gonadotrophin-releasing hormone agonist suppression

This case illustrates the possibility of achieving a pregnancyand birth when elevated progesterone concentrations (>4 ng/ml)are present during the follicular phase (from 6 days beforehuman chorionic gonadotrophin injection) of a gonadotrophin-releasinghormone agonist/menotrophin cycle for in-vitro fertilization(IVF). The present patient underwent three IVF/embryo transfercycles in which progesterone concentrations were repeatedlyincreased from the mid-follicular phase onwards. A pregnancywas achieved after the first IVF attempt but ended in a miscarriagein the 19th week of gestation. During the second IVF attemptan endometrial biopsy taken on the day of oocyte retrieval revealedan endometrial advancement of 2 days. A successful pregnancyand birth was again achieved after the third IVF attempt althoughprogesterone concentrations were considerably increased from6 days before the ovulatory stimulus.     

Phosphocreatine recovery overshoot after high intensity exercise in human skeletal muscle is associated with extensive muscle acidification and a significant decrease in phosphorylation potential

The phosphocreatine (PCr) recovery overshoot in skeletal muscle is a transient increase of PCr concentration above the resting level after termination of exercise. In the present study [PCr], [ATP], [P_i] and pH were measured in calf muscle during rest, during plantar flexion exercise until exhaustion and recovery, using the ³¹P NMR spectroscopy. A significantly greater acidification of muscle cells and significantly lower phosphorylation potential (ΔG _ATP) at the end of exercise was encountered in the group of subjects that evidenced the [PCr] overshoot as well as [ADP] and [P_i] undershoots than in the group that did not. We postulate that the role of the PCr overshoot-related transiently elevated [ATP]/[ADP_free] ratio is to activate different processes (including protein synthesis) that participate in repairing numerous damages of the muscle cells caused by intensive exercise-induced stressing factors, such as extensive muscle acidification, a significant decrease in ΔG _ATP, an elevated level of reactive oxygen species or mechanical disturbances.     

The effects of a glycogen loading regimen on acid-base status and blood lactate concentration before and after a fixed period of high intensity exercise in man

Summary Six healthy male subjects exercised after an overnight fast for a fixed 3 min period at a workload equivalent to 100% of their maximal oxygen uptake ( ) on 3 separate occasions. The first test took place after subjects had consumed a mixed diet (43±3% carbohydrate (CHO), 41±5% fat and 16±3% protein) for 3 days, and was followed 2 h later by prolonged cycling to exhaustion at 77±3% to deplete muscle glycogen stores. Following this, subjects consumed a low CHO diet (4±1% CHO, 63±5% fat and 33±6% protein) for the remainder of the day and for the subsequent 2 days; on the morning of the next day a second high intensity test took place. Finally subjects followed a 3 day high CHO diet (73±7% CHO, 17±6% fat and 10±1% protein) before their last test. Acid-base status and selected metabolites were measured on arterialised-venous blood at rest prior to exercise and at intervals for 15 min following exercise. Prior to exercise, plasma pH and blood lactate concentration were higher (p<0.05) after the high CHO diet when compared with the low CHO diet. Pre-exercise plasma bicarbonate, blood PCO₂ and blood base excess were all higher after the high (p<0.001,p<0.01,p<0.01 respectively) and normal (p<0.05,p<0.05,p<0.05 respectively) CHO diets when compared with the low CHO diet. During the post-exercise period there were no differences in plasma pH or blood base excess between the three experimental situations; plasma bicarbonate was higher (p<0.05) at 2 min post-exercise after the high CHO diet when compared with the low CHO diet; blood PCO₂ was higher throughout the post-exercise period after the high CHO diet when compared with the low CHO diet and at 2 min post-exercise was higher after the normal CHO diet than after the low CHO diet (p<0.5). The post-exercise blood lactate concentration after the high CHO diet was at all times higher than the corresponding values recorded after the normal CHO diet and until 15 min post-exercise was significantly higher than the values recorded after the low CHO diet. The present experiment further substantiates the view that a pattern of dietary and exercise manipulation can significantly influence the acid-base status of the blood and by doing so may influence high intensity exercise performance.     

Changes in serum concentrations and pituitary content of the two prolactins and growth hormone during the reproductive cycle in female tilapia, Oreochromis mossambicus, compared with changes during fasting

Patterns of change in serum concentrations and pituitary content of GH and two tilapia prolactins (PRL177 and PRL188) were examined during the reproductive cycle of female tilapia, Oreochromis mossambicus, adapted to fresh water and to seawater. Changes in these hormones during fasting were examined to elucidate whether changes observed during brooding could be attributed to a reduction in feeding during brooding. Serum concentrations of GH increased prior to pituitary content during the brooding phase of the reproductive cycle. In contrast, pituitary content of GH increased prior to serum concentrations during fasting. There was no consistent pattern of change in serum or pituitary PRL levels during the reproductive cycle, among experiments. Serum concentrations of PRL177 were elevated in all fasted fish, whereas PRL188 was elevated during fasting in males but not females. The increases in the serum concentration of PRLs and GH, and in the pituitary content of GH in response to fasting support the notion that these hormones are involved in the regulation of the use of metabolic substrates in tilapia. We conclude that reduced food intake during brooding may contribute to changes in serum and pituitary levels of the PRLs and GH observed during the reproductive cycle. Nevertheless, differences between changes in serum and pituitary GH during brooding and fasting suggest GH has actions in reproduction, and changes in GH during brooding are not only in response to fasting.     

Thyroid-stimulating hormone (TSH) receptor antibodies and antibodies stimulating adenyl cyclase in relatives from two families with a high prevalence of Graves' hyperthyroidism: A ten-year follow-up study

Thyroid-stimulating hormone (TSH) receptor antibodies and antibodies stimulating adenyl cyclase were measured in 47 relatives of patients with Graves' hyperthyroidism from two families with a high prevalence of the disease, in whom bioassays for the long-acting thyroid stimulator (LATS) had been performed 10 years earlier. Tests were also carried out in six propositi from the two families and age- and sex-matched normal subjects from six families. There had been no new cases of hyperthyroidism since the first study, although one subject was clinically and biochemically hyperthyroid at the time of study and two more were biochemically borderline hyperthyroid but clinically euthyroid. Levels of serum T₄, thyrotropin, and percentage T₃ resin uptake and free thyroxine indices were similar for relatives and normal subjects, although the mean serum T₃ level for relatives was significantly greater than that for the normal subjects. Antibodies were not detected by either assay in any relative. Significant titers of antithyroglobulin antibodies were demonstrated in 4 of 44 relatives but in none of 46 normals tested, while thyroid cytoplasmic antibodies were detected in 8 of 44 relatives and 3 of 45 normals. The mean serum IgG for Graves' relatives was significantly greater than that for the normals, although the mean IgM and IgA levels for the two groups were not significantly different.