Cardiovascular,hormonal and body fluid changes during prolonged exercise

Summary During prolonged heavy exercise a gradual upward drift in heart rate (HR) is seen after the first 10 min of exercise. This secondary rise might be caused by a reduction in stroke volume due to reduced filling of the heart, which is dependent upon both hemodynamic pressure and blood volume. Swimming and bicycling differ with respect to hydrostatic pressure and to water loss, due to sweating. Five subjects were studied during 90 min of bicycle exercise, and swimming the leg kick of free style. The horizontal position during swimming resulted in a larger cardiac output and stroke volume. After the initial rise in heart rate the secondary rise followed parallel courses in the two situations. The rises were positively related to the measured increments in plasma catecholamine concentrations, which continued to increase as exercise progresssed. The secondary rise in HR could not be explained by changes in plasma volume or in water balance, nor by changes in plasma [K]. The plasma volume decreased 5–6% (225–250 ml) within the first 5 to 10 min of exercise both in bicycling and swimming, but thereafter remained virtually unchanged. The sweat loss during bicycling was four times greater than during swimming; but during swimming the hydrostatic conditions induced a diuresis, so that the total water loss was only 25% less than during bicycling.     

Glucoregulation and hormonal changes during prolonged exercise in boys and girls

A group of 17 children, 8.5–11 years old, performed a 60-min cycle exercise at 60% of maximal oxygen uptake (VO_2max) 2 h after a standardized breakfast. They were 10 young boys (pubertal stage =1) and 7 young girls (pubertal stage 2) of similarVO_2max (respective values were 48.5 ml min^–1 kg^–1, SEM 1.8; 42.1 ml min^–1 kg^–1, SEM 2.4). Blood samples of 5 ml were withdrawn by heparinized catheter, the subjects being in a supine position, 30 min before the test, then after 0, 15, 30 and 60 min of exercise and following 30 min recovery. Haematocrit was immediately measured. Thereafter plasma was analysed for glucose, non-esterified fatty acid, glycerol, catecholamine (noradrenaline, adrenaline), insulin and glucagon concentrations. This study showed two main results. First, the onset of exercise induced a significant glucose decrease (of about 11,4%) in all the children. Secondly, both the glycaemic and the hormonal responses were obviously different according to the sex. In boys only, the initial glucose drop was significantly correlated to the pre-exercise insulin values. Whatever the time, the glycaemic levels and the catecholamine responses were lower in girls than in boys, whereas the insulin values remained higher. However, none of these two hormonal parameters seemed to be really responsible for the lower glucose values in girls. On the one hand, the great individual variability of noradrenaline and adrenaline and differences in their relative intensity at the end of the exercise between boys and girls might contribute to the lower catecholamine levels in girls. On the other hand, the lack of a significant relationship in girls between the glucose decrease after exercise and the pre-exercise insulin values might be explained by a relative insulin insensitivity concomitant with the earlier growth spurt in girls, as demonstrated in subjects at rest by other authors. Finally the mechanisms of all these gender differences remain to be clarified and might be accounted for by a different maturation level in boys and girls.     

Psychological stress during exercise: cardiorespiratory and hormonal responses

The purpose of this study was to examine the cardiorespiratory (CR) and stress hormone responses to a combined physical and mental stress. Eight participants ( = 41.24 ± 6.20 ml kg⁻¹ min⁻¹) completed two experimental conditions, a treatment condition including a 37 min ride at 60% of with participants responding to a computerized mental challenge dual stress condition (DSC) and a control condition of the same duration and intensity without the mental challenge exercise alone condition (EAC). Significant interactions across time were found for CR responses, with heart rate, ventilation, and respiration rate demonstrating higher increases in the DSC. Additionally, norepinephrine was significantly greater in the DSC at the end of the combined challenge. Furthermore, cortisol area-under-the-curve (AUC) was also significantly elevated during the DSC. These results demonstrate that a mental challenge during exercise can exacerbate the stress response, including the release of hormones that have been linked to negative health consequences (cardiovascular, metabolic, autoimmune illnesses).     

Temperature-induced changes in metabolic and hormonal responses to intensive dynamic exercise

Seven male subjects performed intensive cycle exercise to exhaustion at subnormal muscle temperature (T_m, 29 ± 2.8 °C). Exercise at exactly the same rate of exercise and duration (370 ± 34 W, 1.5 ± 0.15 min) was then repeated with normal T_m (35 ± 0.9 °C). During exercise both the arterial (a) and femoral venous (fv) contents of oxygen were significantly higher at subnormal than at normal T_m, because of the higher haemoglobin concentration, but the a-fv oxygen difference was the same in the two situations. The rate of increase in lactate concentration in both arterial and venous blood during exercise was the same in the two situations. During exercise the plasma concentrations of adrenaline and noradrealine in arterial and venous blood were significantly higher at subnormal than at normal T_m. At rest and after exercise the calf blood flow was significantly reduced at subnormal T_m At the end of exercise the concentrations of glucose-6-phosphate and lactate in the muscle were significantly higher at subnormal T_m than in the muscle of normal temperature. These findings suggest that there was a greater increase in glycolysis in the muscle of subnormal temperature during exercise, possibly as a result of impaired work efficiency and/or reduced blood flow in the cold muscle.     

Lipid metabolic changes during hormonal treatment of endometriosis

Three groups of patients with pelvic endometriosis were treated with medroxyprogesterone acetate (MPA) 50 mg/day (n = 10), lynestrenol (LYN) 10 mg/day (n = 25) and danazol (DAN) 600 mg/day (n = 25) respectively. Total cholesterol, triglycerides, alpha-lipoprotein, prebetalipoprotein, beta-lipoprotein cholesterol, high-density (HDL) and low-density (LDL) lipoprotein and apolipoprotein A1 and B concentrations were determined before treatment and after 3 and 6 mth of therapy. Whereas lipid, lipoprotein and apolipoprotein levels did not change in the MPA group, the patients on LYN and in particular those on DNA showed marked changes in lipoportein patterns. Alpha-lipoprotein, HDL and apolipoprotein A1 levels fell, while beta-lipoprotein, LDL and apolipoprotein concentrations rose, these changes being statistically significant. No alterations were seen in the serum levels of cholesterol, triglycerides or prebetalipoprotein cholesterol. In view of a possible relationship between high LDL and low HDL levels and a risk of accelerated coronary arteriosclerosis in women it was concluded that progestogen-induced alterations in lipoprotein patterns should be avoided as far as long-term treatment is concerned and where additional risk factors are present.     

Analysis of hormonal changes during combined buserelin/HMG treatment

Changes of serum oestradiol, LH and progesterone have been analysed in view of the effect of the GnRH analogue buserelin on the late follicular and early luteal phase of cycles stimulated with combined buserelin/HMG (n = 31) in an IVF-ET/GIFT programme. Patients undergoing cycles with HMG only (n = 57) served as the control group. With the use of the GnRH analogue buserelin, a significantly higher amount of HMG (25 versus 20 ampoules; P less than 0.001) for a significantly longer stimulation period (10 versus 8 days; P less than 0.001) was necessary to achieve the same oestradiol response as seen in HMG cycles. Serum progesterone levels during a three day period before ovulation induction tended to be lower in the combined buserelin/HMG cycles than in cycles with HMG stimulation only. We did not observe any significant difference in the luteal phase progesterone levels of the buserelin/HMG and the HMG group. On the other hand, we found that an inadequate luteal phase in buserelin/HMG cycles could be avoided by HCG administration during the luteal phase. Both the elevation of basal serum LH and a premature LH rise could also be avoided by the use of buserelin.     

Nocturnal hormonal responses to resistance exercise

The effects of resistance exercise on the nocturnal responses of cortisol (CO), testosterone (TEST), human growth hormone (hGH), and thyroid hormones (T₃, T₄) were examined in eight trained weight lifters. Each subject completed two trials using a counterbalanced design: a control, no exercise trial (CON) and a heavy resistance exercise session of three sets of six exercises to exhaustion (RE). The exercise session took place between 1900 and 2000 hours. Blood was sampled prior to and at 20-min intervals after RE. For both trials blood was sampled at hourly intervals from 2100 hours until 0700 hours. The hGH and CO concentrations were increased up to 40-min post-exercise (P < 0.05), but returned to resting levels 1 h post-exercise. Nocturnal hGH concentration was not affected by RE (P > 0.26) and peaked at 0200 hours and declined until 0700 hours. Similarly, the CO responses were similar between the trails (P > 0.14). This CO concentrations declined from 2200 hours until 0100 hours, then increased steadily until 0700 hours. The TEST concentrations during both trials rose steadily from 2200 hours until 0700 hours; however, the rise in TEST from 0500–0700 hours during RE was greater than during the CON trails (P = 0.059). The T₃ concentrations were unchanged by exercise and were similar at all times between trails. The T₄ concentrations were elevated for 20 min after RE; however nocturnal T₄ concentrations were lower after RE than during CON. These results would suggest that bGH and CO may have limited nocturnal reactivity to resistance exercise. However, the nocturnal alterations of TEST and T4 after resistance exercise, although small, may have implications for muscle anabolism.     

Sonographic changes in the endometrium of climacteric women during hormonal treatment

Vaginal sonography of the endometrium is a new method of monitoring the effects of progestogen replacement therapy during the post-menopausal period. The advantages of transvaginal ultrasonic diagnosis are that the uterus can be seen from the fornix vaginae (that is from close range) and that the examination can be carried out whether the bladder is full or not. The differences in the thickness and structure of the endometrium, and the boundary with the surrounding myometrium, enable most of the endometrial changes that occur during the post-menopausal period to be detected sonographically. In the first group of patients we investigated, endometrial carcinoma was detected in 2 out of 60 women suffering from post-menopausal metrorrhagia, the findings subsequently being confirmed histologically. It was observed that post-menopausal women who have regular bleeding during post-menopausal hormone therapy show signs of endometrial proliferation during oestrogen therapy and of secretion during progestogen therapy.     

Monitoring exercise stress by changes in metabolic and hormonal responses over a 24-h period

Summary Metabolic and endocrine responses of 14 subjects of varying levels of fitness to an intensive anaerobic interval training session were assessed before exercise and at 2 h, 4 h, 8 h and 24 h postexercise. The endocrine response of the same subjects to a control day, where they were required not to exercise, was also assessed and compared with the values obtained on the interval training day. Uric acid, urea, and creatine phosphokinase concentrations still remained elevated above pre-exercise values 24 h postexercise. Lactate, creatinine, testosterone and cortisol concentrations were significantly elevated above pre-exercise values immediately postexercise but these had reversed by 2 h postexercise. Over the remainder of the recovery period testosterone concentrations remained significantly lower than values measured at similar times on the control day. This was shown to be due directly to a change in testosterone as sex hormone binding globulin concentration remained constant throughout the recovery period. The data indicate that when comparisons of data were made to control (rest) days, imbalances in homeostasis, due to intensive training, are not totally reversed within the next 24-h. The data also demonstrate that the parameters measured undergo the same variations in subjects with a wide range of physical fitness, indicating that these parameters could be used to monitor exercise stress and recovery in athletes of a wide range of abilities. The more acute responses to exercise could be mistaken for overtraining if insufficient recovery time were not permitted between the final exercise session and taking blood samples, further emphasising the need to be able to recognise the difference between the fatigue associated with acute exercise and a state of chronic fatigue that may result from too little regeneration time within the training programme.     

The CSF and arterial to internal jugular venous hormonal differences during exercise in humans

Strenuous exercise increases the cerebral uptake of carbohydrate out of proportion to that of oxygen, but it is unknown whether such enhanced carbohydrate uptake is influenced by the marked endocrine response to exercise. During exhaustive exercise this study evaluated the a-v differences across the brain (a-v diff) of hormones that could influence its carbohydrate uptake (n= 9). In addition, neuroendocrine activity and a potential uptake of hormones via the cerebrospinal fluid (CSF) were assessed by lumbar puncture postexercise and at rest (n= 6). Exercise increased the arterial concentration of noradrenaline and adrenaline, but there was no cerebral uptake. However, following exercise CSF noradrenaline was 1.4 (0.73-5.5) nmol l(-1), and higher than at rest, 0.3 (0.19-1.84) nmol l(-1) (P < 0.05), whereas adrenaline could not be detected. Exercise increased both the arterial concentration of NH(4)(+) and its a-v diff, which increased from 1 (-12 to 5) to 17 (5-41) micromol l(-1) (P < 0.05), while the CSF NH(4)(+) was reduced to 7 (0-10) versus 11 (7-16) micromol l(-1) (P < 0.05). There was no release from, or accumulation in the brain of interleukin (IL)-6, tumour necrosis factor (TNF-alpha), heatshock protein (HSP72), insulin, or insulin-like growth factor (IGF)-I. The findings indicate that for maximal exercise, the concentration of noradrenaline is increased within the brain, whereas blood borne hormones and cytokines are seemingly unimportant. The results support the notion that the exercise-induced changes in brain metabolism are controlled by factors intrinsic to the brain.     

Morphological changes in the ovaries during modeling of functional cysts of hormonal genesis

Morphological study of ovarian follicular cysts induced by chorionic gonadotropin (300 U) and insulin (Protafane HM; 2.5 U) in adult rats showed that superovulatory dose of chorionic gonadotropin and moderate hyperinsulinemia induced the development of ovarian cysts on days 3–5 in 100% cases. Dynamic study of ovarian morphology showed that changes were reversible and the cysts regressed within 60 days, which confirmed their functional nature. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 144, No. 9, pp. 338–341, September, 2007     

The effects of age on substrate depletion and hormonal responses during submaximal exercise in hamsters

Senescent hamsters display a marked reduction in volume of voluntary running. The purpose of this study was to determine whether age differences exist in the pattern of fuel utilization during submaximal exercise, which may account for the reduction in voluntary running. Further, we determined the effects of age on muscle oxidative capacity to assess its relationship to endurance performance in senescent hamsters. Depletion of carbohydrate and lipid content of skeletal muscle and liver, and changes in blood concentration of various hormones and substrates during one hour of exercise at 60 percent of VO2 max served to assess age effects on utilization of metabolic substrates. Exercise produced equivalent depletion of muscle glycogen and similar rise in plasma free fatty acids in young and old hamsters. No exercise effects on skeletal muscle triglyceride concentration or on plasma glycerol, glucagon or catecholamine concentrations were noted. With palmitoyl carnitine as substrate (but not with pyruvate) State 3 respiration of cardiac and skeletal muscle homogenates was lower in old compared to young hamsters. Although old hamsters have a reduced capacity to oxidize lipids in vitro, few age differences in fuel use are evident in vivo during submaximal exercise. Thus, these minor age differences in substrate utilization do not likely account for the substantial reduction in the levels of spontaneous running in senescent hamsters.     

Effects of hydration state on hormonal and renal responses during moderate exercise in the heat

The effects of hydromineral hormones and catecholamines on renal concentrating ability at different hydration states were examined in five male volunteers while they performed three trials. Each of these trials comprised a 60-min exercise bout on a treadmill (at 50% of maximal oxygen uptake) in a warm environment (dry bulb temperature, 35°C; relative humidity, 20–30%). In one session, subjects were euhydrated before exercise (C). In the two other sessions, after thermal dehydration (loss of 3% body mass) which markedly reduced plasma volume (PV) and increased plasma osmolality (osm_pl), the subjects exercised either not rehydrated (Dh) or rehydrated (Rh) by drinking 600 ml of mineral water before and 40 min after the onset of exercise. During exercise in the Dh compared to C state, plasma renin, aldosterone, arginine vasopressin (AVP), noradrenaline and adrenaline concentrations were increased (P < 0.05). A reduction in creatinine clearance and urine flow was also observed (P < 0.05) together with a decrease in urine osmolality, osmolar clearance and sodium excretion, while free water clearance increased (P < 0.05). However, compared to Dh, Rh partially restored PV and osm_pl and induced a marked reduction in the time courses of both the plasma AVP and catecholamine responses (P < 0.05). Values for renal water and electrolyte excretion were intermediate between those of Dh and C. Plasma atrial natriuretic peptide presented similar changes whatever the hydration state. These results demonstrate that during moderate exercise in the heat, renal concentrating ability is paradoxically reduced by prior dehydration in spite of high plasma AVP levels, and might be the result of marked activation of the sympatho-adrenal system. Rehydration, by reducing this activation, could partially restore the renal concentrating ability despite the lowered plasma AVP. Accepted: 23 April 1997     

Plasma renin and aldosterone changes during twenty minutes' moderate exercise

Summary The influence of posture on plasma renin and aldosterone changes during exercise performed at a constant relative work load (40%–50% maximal oxygen uptake) was studied in eight healthy men. Each subject carried out two 20-min exercises on an ergocycle at an interval of 8 days; the first exercise was performed in the normal sitting position (upright exercise), the second in a comfortable supine position (supine exercise). In both cases, heart rate and blood pressure were measured as well as plasma renin activity (PRA), aldosterone (ALDO) and osmolality, before and immediately after exercise, and 15 min following the end of exercise. An increase in heart rate, blood pressure, PRA, ALDO and osmolality was noted at the end of each exercise. This increase was greater in the supine exercise than when upright for PRA and ALDO; plasma osmolality and blood pressure showed identical increases for both types of exercise; increase in heart rate was greater when supine than when upright. PRA and ALDO were still elevated 15 min after the upright activity, but had regained their base values in that time after the supine exercise. Our results show that moderate, relatively brief periods of exercise stimulate the production of renin and aldosterone, but the response is less when supine than in the normal upright position.     

Metabolism changes in single human fibres during brief maximal exercise

Changes in high-energy phosphate levels in single human skeletal muscle fibres after 10 s of maximal (all-out) dynamic exercise were investigated. Muscle biopsies from vastus lateralis of two volunteers were collected at rest and immediately post exercise. Single muscle fibres were dissected from dry muscle and were assigned into one of four groups according to their myosin heavy chain (MyHC) isoform content: that is type I, IIA, IIAx and IIXa (the latter two groups containing either less or more than 50% IIX MyHC). Fragments of characterised fibres were analysed by HPLC for ATP, inosine-monophosphate (IMP), phosphocreatine (PCr) and creatine levels. After 10 s of exercise, PCr content ([PCr]) declined by approximately 46, 53, 62 and 59 % in type I, IIA, IIAx and IIXa fibres, respectively (P < 0.01 from rest). [ATP] declined only in type II fibres, especially in IIAx and IIXa fibres in which [IMP] reached mean values of 16 +/- 1 and 18 +/- 4 mmol (kg dry mass)(-1), respectively. While [PCr] was reduced in all fibre types during the brief maximal dynamic exercise, it was apparent that type II fibres expressing the IIX myosin heavy chain isoform were under a greatest metabolic stress as indicated by the reductions in [ATP].