Acute exercise effect on postabsorptive serum leptin.

We postulated that high circulating cortisol levels during intense exercise would lead to increased serum leptin concentrations. Young, lean men ate a small meal and then exercised on a cycle ergometer for 41 min or rested on a control day. Serum leptin concentration was 10% greater during exercise than in the control condition (P < 0.05). Directly after exercise, serum leptin dropped to approximately 10% less than the control level (P < 0.05) but had recovered to the nonexercised level after approximately 2 h of recovery. Rapid exercise effects on circulating leptin were related to changes in hemoconcentration rather than changes in leptin mass. When serum leptin was normalized to serum protein, leptin increased by 10% in the exercise condition compared with control by the end of recovery (P < 0.05). Although exercise increased serum cortisol concentration threefold, there was no relation between differences in cortisol and exercise vs. control differences in normalized leptin. The increased leptin mass after exercise may have been related to greater plasma glucose concentration during recovery after exercise compared with the control condition.     

Effects of L-carnitine administration on VO2max and the aerobic-anaerobic threshold in normoxia and acute hypoxia

Seven healthy young male adults were subjected to a total of 56 tests to ascertain the effects of L-carnitine (L-C) and a placebo (P) on ventilation, O2 intake (VO2), CO2 output, heart rate, blood pressure and serum lactic acid, non-esterified fatty acid, glycerol and glucose during strenuous and aerobic/anaerobic threshold-level treadmill exercise. The tests were made in conditions of normoxia (O2 = 20.9%) and hypoxia (O2 = 13.0%, equivalent to 3,500 m above sea level). The only clear difference was in the respiratory quotient (RQ = 0.883, SD 0.025 vs 0.904, SD 0.035) after L-C and P administration respectively (P less than 0.01), under normal oxygenation and 0.861, SD 0.052 following L-C vs 0.926, SD 0.040 after P (P less than 0.01) in acute hypoxia at VO2 levels around the anaerobic threshold. The lower RQ values of the L-C-treated subjects during hypoxia indicate a lower rate of carbohydrate transformation.     

Benefits of short-term muscular training in reducing the effects of muscular over-exertion

Muscle soreness, serum creatine kinase (CK), and serum and urinary hydroxyproline levels were examined following muscle over-exertion and resistance training. Seven untrained men performed high intensity leg-extension exercises at a resistance at which they could initially accomplish 90% of their 10 repetitions maximum (10 RM), for 30 minutes to induce muscle over-exertion. In Phase 1 a single bout of muscular over-exertion was followed by a week of rest. Phase 2, the training period, was a repeat of the over-exertion workload of Phase 1 for five consecutive days. Phase 3 was a single bout of over-exertion at a higher 10 RM workload. Normo-responsive and hyper-responsive changes in serum CK were exhibited by different subjects in Phase 1. Muscle soreness was perceived by both groups but to a greater extent in the hyper-responsive group. Serum CK and muscle soreness values were lower during Phase 2 and 3 than in Phase 1. Neither serum nor urinary hydroxyproline levels changed significantly post-exercise. These findings show that a single bout of intense exercise and a brief period of muscular training reduces serum CK and muscle soreness responses following a subsequent single bout of exercise at a higher intensity.     

Effect of carbohydrate ingestion and hormonal responses on ratings of perceived exertion during prolonged cycling and running

This randomized, double-blind, placebo-controlled study was designed to determine the influence of exercise mode, and 6% carbohydrate (C) versus placebo (P) beverage ingestion, on ratings of perceived exertion (RPE) and hormonal regulation to 2.5 h of high-intensity running and cycling (approximately 75% maximum oxygen uptake) by ten triathletes who acted as their own controls. Statistical significance was set at P < or = 0.05. The pattern of change in RPE over time was significantly different between C and P ingestion (P < 0.001) and between running and cycling modes (P = 0.001). The lowest RPE values were seen in the C-cycling sessions and the highest in the P-running sessions. The pattern of change in the respiratory exchange ratio and fat and carbohydrate oxidation rates were significantly different between the C and P conditions but not between the running and cycling modes. C relative to P ingestion (but not exercise mode) was associated with higher plasma levels of glucose and insulin and lower plasma cortisol and growth hormone levels. The pattern of change in plasma levels of catecholamines and lactate did not differ between the C and P conditions. These data indicate that a lower RPE was associated with a higher level of carbohydrate oxidation, higher plasma glucose and insulin levels, and lower plasma cortisol and growth hormone levels during cycle exercise following C supplementation as compared to P feeding. These findings support a physiological link between RPE and carbohydrate substrate availability as well as selected hormonal regulation during cycle exercise.     

Haematology and serum biochemistry of captive unsedated chital deer (Axis axis) in Australia

Haematological and serum biochemical values were measured in blood samples collected over a 12-mo period from 37 unsedated chital deer (Axis axis). Stags and hinds, ranging in age from birth to maturity, were sampled. Haemoglobin, total erythrocyte and haematocrit values were low at birth and sex differences were not apparent in neonates and juveniles, but were in adults. Chital stags had higher erythrocyte parameters (P less than 0.001) and lower erythrocyte indices than hinds, and the total leucocyte count was higher in stags (P less than 0.01). Some parameters (erythrocytes, muscle enzymes, glucose, cortisol) decreased over successive serial sampling. The differential leucocyte count of older stags decreased during the initial handling period. The major rutting period in February and March was characterised by changes in the differential leucocyte count, elevations in serum muscle enzymes, and lower serum cortisol levels. Alkaline phosphatase activity in serum reflected the annual antler cycle of chital stags. Serial sampling over many weeks, either weekly or tri-weekly, produced haematological and biochemical changes in successive samples which may have reflected a reduction in stress and excitement associated with restraint.     

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

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 (VO2max), 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 pretraining 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 micrograms.l-1, SEM 36, respectively. After the physical training, VO2max 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 less than 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 micrograms.l-1, SEM 30) concentration were less than the pre-training value (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of a 24-h carbohydrate-poor diet on metabolic and hormonal responses during prolonged glucose-infused leg exercise

Extant literature dealing with metabolic and hormonal adaptations to exercise following carbohydrate (CHO) reduced diets is not sufficiently precise to allow researchers to partial out the effects of reduced blood glucose levels from other general effects produced by low CHO diets. In order to shed light on this issue, a study was conducted to examine the effects of a 24-h CHO-poor diet on substrate and endocrine responses during prolonged (75 min; 60% Vo2max) glucose-infused leg exercise. Eight subjects exercised on a cycle ergometer in the two following conditions: 1) after a normal diet (CHON), and 2) after a 24-h low CHO diet (CHOL). In both conditions, glucose was constantly infused intravenously (2.2 mg . kg-1 . min-1) from the 10th to the 75th min of exercise in relatively small amounts (10.4 +/- 0.8 g). No significant differences in blood glucose concentrations were found between the two conditions at rest and during exercise although a significant increase (p less than 0.01) in glucose level was observed in both conditions after 40 min of exercise. The CHOL as compared to the CHON condition, was associated with significantly (p less than 0.05) lower resting concentrations of insulin, muscle glycogen (8.7 vs 10.6 g . kg-1), and triacylglycerol, and greater concentrations of beta-hydroxybutyrate (0.5 vs 0.2 mmol . L-1), and free fatty acids. During exercise, the CHOL condition as compared to the CHON condition, was associated with significantly (p less than 0.05) lower insulin and R values, as well as greater free fatty acid (from min 20 to 60) and epinephrine (min 60 to 75) concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolic, thermoregulatory, and perceptual responses during exercise after lower vs. whole body precooling.

The purpose of this investigation was to compare the thermoregulatory, metabolic, and perceptual effects of lower body (LBI) and whole body (WBI) immersion precooling techniques during submaximal exercise. Eleven healthy men completed two 30-min cycling bouts at 60% of maximal O(2) uptake preceded by immersion to the suprailiac crest (LBI) or clavicle (WBI) in 20 degrees C water. WBI produced significantly lower rectal temperature (T(re)) during minutes 24-30 of immersion and lower T(re), mean skin temperature, and mean body temperature for the first 24, 14, and 16 min of exercise, respectively. Body heat storage rates differed significantly for LBI and WBI during immersion and exercise, although no net differences were observed between conditions. For WBI, metabolic heat production and heart rate were significantly higher during immersion but not during exercise. Thermal sensation was significantly lower (felt colder) and thermal discomfort was significantly higher (less comfortable) for WBI during immersion and exercise. In conclusion, WBI and LBI attenuated T(re) increases during submaximal exercise and produced similar net heat storage over the protocol. LBI minimized metabolic increases and negative perceptual effects associated with WBI.     

Influence of carbohydrate ingestion on oxidative stress and plasma antioxidant potential following a 3 h run

Concentrations of reactive oxygen species (ROS) increase during exercise secondary to increased oxygen uptake, xanthine oxidase activity, and immune system activation. Carbohydrate compared to placebo beverage ingestion is associated with an attenuated cortisol and catecholamine response. Catecholamines can undergo autooxidation to form ROS. We hypothesized that during intense exercise, ingestion of carbohydrate compared to placebo would diminish oxidative stress. Sixteen experienced marathoners ran on treadmills for 3 h at ∼70% VO

2max

on two occasions while receiving carbohydrate or placebo beverages (1 l/h, double-blinded) in a randomized, counterbalanced order. Blood samples were collected before and immediately after exercise, snap frozen in liquid nitrogen, and stored at -80°C until analysis. Plasma samples were analyzed for F2-isoprostanes (FIP) and lipid hydroperoxides (ROOH) as measures for lipid peroxidation, ferric reducing ability of plasma (FRAP) as a measure of plasma antioxidant potential and for cortisol. The pattern of change in cortisol was significantly different between carbohydrate and placebo conditions (P=0.024), with post-exercise levels higher in the placebo condition. Under both carbohydrate and placebo conditions, significant increases in FIP, ROOH, and FRAP were measured, but the pattern of increase was not different (FIP, interaction effect, P=0.472; ROOH, P=0.572; FRAP, P=0.668). Despite an attenuation in the cortisol response, carbohydrate compared to placebo ingestion does not counter the increase in oxidative stress or modulate plasma antioxidant potential in athletes running 3 h at 70% VO

2max

.     

Blood pressure and plasma catecholamine responses to various challenges during exercise-recovery in man

The purpose of this study was to assess the effects of a 2 h cycle exercise (50% VO2max) on heart rate (HR) and blood pressure (BP), and on plasma epinephrine (E) and norepinephrine (NE) concentrations, during the recovery period in seven normotensive subjects. Measurements were made at rest in supine (20 min) and standing (10 min) positions, during isometric exercise (hand-grip, 3 min, 25% maximal voluntary, contraction), in response to a mild psychosocial challenge (Stroop conflicting color word task) and during a 5-min period of light exercise (42 +/- 3% VO2max). Data were compared to measurements taken on another occasion under similar experimental conditions, without a previous exercise bout (control). The results showed HR to be slightly elevated in all conditions following the exercise bout. However, diastolic and systolic BP during the recovery period following exercise were not significantly different from the values observed in the control situation. Plasma NE concentrations in supine position and in response to the various physiological and/or psychosocial challenges were similar in the control situation and during the recovery period following exercise. On the other hand plasma E (nmol.1-1) was about 50% lower at rest (0.11 +/- 0.03 vs 0.23 +/- 0.04) as well as in response to hand-grip (0.21 +/- 0.04 vs 0.41 +/- 0.20) and the Stroop-test (0.21 +/- 0.05 vs 0.41 +/- 0.15) following the exercise bout.(ABSTRACT TRUNCATED AT 250 WORDS)     

Corticotropin releasing hormone and gonadotropin secretion in physically active males after acute exercise.

Plasma concentrations of corticotropin releasing hormone (CRH) and the serum concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone, adrenocorticotropic hormone (ACTH) and cortisol were measured in seven physically active males after acute exercise on a treadmill using the Bruce protocol. Measurements were made in the basal pre-exercise state, immediately after exercise, and at 30-min intervals for 3 h after exercise. Serum LH concentrations declined following exercise reaching nadir values between 60 and 180 min after exercise (90 min post exercise in the group). The nadir values in individual volunteers were significantly lower than both the baseline and post-exercise levels. This fall in serum LH concentration appeared to follow a slight but significant elevation of the plasma concentration of CRH which reached peak levels when measured immediately post exercise. Plasma ACTH concentrations paralleled the rise in CRH, but fell to undetectable levels of below 13.8 nmol.l-1 (less than 5 ng.l-1) 60 min after exercise. Plasma cortisol concentrations peaked approximately 30 min after the rise in ACTH, after which they gradually declined to baseline levels. Plasma testosterone concentrations paralleled the concentrations of LH. The data suggest that CRH, on the basis of its previously described gonadotropin-depressant property, may be the hormone involved in the exercise-mediated decline in serum LH. Alternatively, some as yet unidentified factor(s), may be involved in producing the altered concentrations of both LH and CRH.     

Cortisol response of green sturgeon to acid-infusion stress

Cortisol and lactate are classic indicators of stress in fishes and their interactive effects on metabolism during recovery from stress have recently become a subject of more intense study. We examined how stressing green sturgeon through acid infusion affected the cortisol response and lactate metabolism in green sturgeon (Acipenser medirostris). Both lactic acid (0.3 M) and HCl (0.3 N) infusion (infusion volumes 1.5 ml kg(-1)) elicited an immediate cortisol response (21.61+/-4.61 ng ml(-1) and 17.50+/-3.00 ng ml(-1), respectively). Lactic acid prolonged the cortisol response compared to HCl (90 min vs. 25 min). Neutralized lactate (0.23 M; with 1 N NaOH; final pH 7.8) and NaCl (0.9%) infusion (infusion volumes 1.5 ml kg(-1)) did not affect plasma cortisol. Sturgeon infused with lactic acid showed a faster rate of lactate disappearance from plasma than those with neutralized lactic acid. We relate these findings to lactate metabolism following exercise, acid-infusion and air immersion stress in fishes.     

Central venous pressure and plasma arginine vasopressin during water immersion in man

The influence of increased central venous pressure (CVP) on the plasma concentration of arginine vasopressin (pAVP) was examined in 7 healthy males subjected to water immersion (WI) up to the neck following overnight food- and fluid restriction. During WI the subject sat upright in a pool (water temperature = 35.0 degrees C) for 6 h. In control experiments the subject assumed the same position outside the pool wearing a water perfused garment (water temperature = 34.6 degrees C). CVP increased markedly during WI and after 20 min of immersion it attained a level which was significantly higher than the control value (10.9 +/- 1.5 (mean +/- SE) vs. 2.2 +/- 1.3 mm Hg, p less than 0.01). This increase was sustained throughout the 6 h WI period. Simultaneously, after 20 min pAVP during WI was significantly lower than control values (1.8 +/- 0.3 vs. 2.2 +/- 0.3 pg X ml-1, p less than 0.05) and sustained throughout WI. Systolic arterial pressure increased significantly by 7-10 mm Hg (p less than 0.05) after 2 h of WI, while diastolic arterial pressure was unchanged. Heart rate was decreased by 10 bpm throughout immersion. There was no change in plasma osmolality when comparing control with immersion. A pronounced osmotic diuresis, natriuresis and kaliuresis occurred during WI, counteracting an acute significant increase in plasma volume of 6.5 +/- 1.9% (P less than 0.01 within 20 min of immersion). We conclude that an increase in CVP due to WI is accompanied by suppressed pAVP.     

Chromium metabolism and its role in disease processes in man

Chromium is an essential element required for normal carbohydrate and lipid metabolism. Insufficient dietary Cr has been linked to maturity-onset diabetes and cardiovascular diseases. The dietary Cr intake of most individuals is considerably less than the suggested safe and adequate intake. Consumption of refined foods, including simple sugars, exacerbates the problem of insufficient dietary Cr since these foods are not only low in dietary Cr but also enhance additional Cr losses. Chromium losses are also increased due to pregnancy, strenuous exercise, infection, physical trauma and other forms of stress. Supplementation of Cr to normal free-living individuals often leads to significant improvements in glucose tolerance, serum lipids including high-density lipoprotein cholesterol, insulin and insulin binding. Chromium also tends to normalize blood sugar. Chromium supplementation of subjects with elevated blood sugar following a glucose load leads to a decrease in blood sugar while hypoglycemics respond to supplemental Cr by an increase in hypoglycemic glucose values, increased insulin binding and alleviation of hypoglycemic symptoms. In summary, dietary intake of Cr is suboptimal and this is exacerbated by increased Cr losses due to stress and certain refined foods including simple sugars that enhance Cr losses. Supplemental Cr is associated with improvements of risk factors associated with maturity-onset diabetes and cardiovascular diseases.     

Preconditioning with hydrogen peroxide (H2O2) or ischemia in H2O2-induced cardiac dysfunction

To assess whether allantoin levels in serum and urine are influenced by exhaustive and moderate exercise and whether allantoin is a useful indicator of exercise-induced oxidative stress in humans, we made subjects perform exhaustive and moderate (100% and 40% VO₂max) cycling exercise and examined the levels of allantoin, thiobarbituric acid reactive substances (TBARS) and urate in serum and urine. Immediately after exercise at 100% VO₂max, the serum allantoin/urate ratio was significantly elevated compared with the resting levels while the serum urate levels was significantly elevated 30 min after exercise. The serum TBARS levels did not increase significantly compared with the resting levels. Urinary allantoin excretion significantly increased during 60 min of recovery after exercise, however, urinary urate excretion decreased significantly during the same period. The urinary allantoin/urate ratio also rapidly increased during 60 min of recovery after exercise. Urinary TBARS excretion decreased during the first 60 min of the recovery period and thereafter significantly increased during the latter half of the recovery period. On the contrary, after 40% VO₂max of exercise, no significant changes in the levels of urate, allantoin and TBARS in serum or urine were observed. These findings suggest that allantoin levels in serum and urine may reflect the extent of oxidative stress in vivo and that the allantoin which appeared following exercise may have originated not from urate formed as a result of exercise but from urate that previously existed in the body. Furthermore, these findings support the view that allantoin in serum and urine is a more sensitive and reliable indicator of in vivo oxidative stress than lipid peroxidation products measured as TBARS.     

Is allantoin in serum and urine a useful indicator of exercise-induced oxidative stress in humans?

To assess whether allantoin levels in serum and urine are influenced by exhaustive and moderate exercise and whether allantoin is a useful indicator of exercise-induced oxidative stress in humans, we made subjects perform exhaustive and moderate (100% and 40% VO₂max) cycling exercise and examined the levels of allantoin, thiobarbituric acid reactive substances (TBARS) and urate in serum and urine. Immediately after exercise at 100% VO₂max, the serum allantoin/urate ratio was significantly elevated compared with the resting levels while the serum urate levels was significantly elevated 30 min after exercise. The serum TBARS levels did not increase significantly compared with the resting levels. Urinary allantoin excretion significantly increased during 60 min of recovery after exercise, however, urinary urate excretion decreased significantly during the same period. The urinary allantoin/urate ratio also rapidly increased during 60 min of recovery after exercise. Urinary TBARS excretion decreased during the first 60 min of the recovery period and thereafter significantly increased during the latter half of the recovery period. On the contrary, after 40% VO₂max of exercise, no significant changes in the levels of urate, allantoin and TBARS in serum or urine were observed. These findings suggest that allantoin levels in serum and urine may reflect the extent of oxidative stress in vivo and that the allantoin which appeared following exercise may have originated not from urate formed as a result of exercise but from urate that previously existed in the body. Furthermore, these findings support the view that allantoin in serum and urine is a more sensitive and reliable indicator of in vivo oxidative stress than lipid peroxidation products measured as TBARS.     

Effects of continuous and interval running training on serum growth and cortisol hormones in junior male basketball players

Effects of two different eight-week aerobic training programs consisting of continuous (CR) or extensive interval running (IR) on serum growth (GH) and cortisol hormones in 33 male basketball players aged 15-16 were assessed. The CR group ran 4.8 km and the IR group ran 4 x 1.2 km, using equal work-to-rest ratio, three times per week. Aerobic power scores of all subjects and anaerobic power marks of the training subjects increased (p<0.01). Upon exertion, though serum GH levels increased in both exercise groups (p<0.01) prior to and following training; cortisol levels increased only in the IR group prior to training, and in both exercise groups following training (p<0.05). Following the eight week period, resting cortisol levels rose in the training (p<0.05) and control (p<0.01) groups. To conclude, an 8-week training program consisting of continuous or extensive interval running has been effective on acute GH and cortisol secretion in 15-16 year-old male athletes.     

Glucose kinetics differ between women and men, during and after exercise.

As exercise can improve the regulation of glucose and carbohydrate metabolism, it is important to establish biological factors, such as sex, that may influence these outcomes. Glucose kinetics, therefore, were compared between women and men at rest, during exercise, and postexercise. It was hypothesized that glucose flux would be significantly lower in women than men during both the exercise and postexercise periods. Subjects included normal weight, healthy, eumenorrehic women and men, matched for habitual activity level and maximal oxygen uptake per kilogram lean body mass. Testing occurred following 3 days of diet control, with no exercise the day before. Subjects were tested in the overnight-fasted condition with women studied in the midluteal phase of the menstrual cycle. Resting (120 min), exercise (85% lactate threshold, 90 min), and postexercise (180 min) measurements of glucose flux and substrate metabolism were made. During exercise, women had a significantly lower rate of glucose appearance (Ra) (P<0.001) and disappearance (Rd) (P<0.002) compared with men. Maximal values were achieved at 90 min of exercise for both glucose Ra (mean+/-SE: 22.8+/-1.12 micromol.kg body wt-1.min-1 women and 33.6+/-1.79 micromol.kg body wt-1.min-1 men) and glucose Rd (23.2+/-1.26 and 34.1+/-1.71 micromol.kg body wt-1.min-1, respectively). Exercise epinephrine concentration was significantly lower in women compared with men (P<0.02), as was the increment in glucagon from rest to exercise (P<0.04). During the postexercise period, glucose Ra and Rd were also significantly lower in women vs. men (P<0.001), with differences diminishing over time. In conclusion, circulating blood glucose flux was significantly lower during 90 min of moderate exercise, and immediately postexercise, in women compared with men. Sex differences in the glucagon increase to exercise, and/or the epinephrine levels during exercise, may play a role in determining these sex differences in exercise glucose turnover.     

Exercise performance following a carbohydrate load in chronic airflow obstruction

We evaluated the effects of a large (920 cal) liquid carbohydrate (CHO) load on the maximum exercise capacity of 18 patients with chronic airflow obstruction [forced expiratory volume at at 1 s (FEV1) = 1.27 +/- 0.48 liters; FEV1/forced vital capacity = 0.41 +/- 0.11]. Patients underwent duplicate incremental cycle ergometer exercise tests to a symptom-limited maximum following CHO and a liquid placebo in single-blind fashion. Expired gas measurements were obtained during each power output. In 12 patients arterial blood gases were measured, and in six patients venous blood was obtained for measurement of glucose, electrolytes, and osmolality. With CHO, the maximum power output decreased from 86 +/- 30 to 76 +/- 31 W (P less than 0.001), whereas the ventilation at exhaustion was nearly identical (47.6 +/- 13.2 and 46.8 +/- 12.5 l/min). Arterial partial pressure of CO2 (PaCO2) at exhaustion decreased (P less than 0.025), arterial partial pressure of O2 (PaO2) increased (P less than 0.01), and the ventilatory equivalent for CO2 (VE/VCO2) increased (P less than 0.005) with CHO. At equivalent power outputs, CHO resulted in significant increases in VE (P less than 0.001) and VCO2 (P less than 0.001); PaCO2 was unchanged, whereas PaO2 increased (P less than 0.01). CHO increased the serum glucose at rest and during exercise. No changes in serum osmolality or electrolytes occurred during exercise following CHO. After CHO loading, the majority of patients appeared to reach their limiting level of ventilation at a lower power output. In contrast, there was no significant difference in the mean maximum power output with CHO in six normal control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fluid conservation in athletes: responses to water intake, supine posture, and immersion

The roles of antidiuretic hormone (ADH) and aldosterone in the elicited diuretic responses of trained and untrained men to seated, supine, and head-out water immersed conditions were studied. Volunteers were comprised of groups of six untrained individuals, six trained swimmers, and six trained runners. Each subject underwent three protocols, six hours in a seated position, supine position, or immersion (35 degrees C water). The last two protocols were preceded and followed by 1 h of seated position. After 10 h of fasting, 0.5% body wt of water was drunk. One hour later the trained groups had higher urine osmolalities (P less than 0.05) and urinary excretion rates of ADH (P less than 0.05) and lower urine flow rates (P less than 0.05) than untrained subjects. Throughout the sitting protocol, urinary ADH was also higher in both trained groups (P less than 0.05). Both supine posture and immersion resulted in significant decreases in urinary ADH in the untrained subjects (P less than 0.05) but no changes wer noted in swimmers and only during the second hour of immersion in the runners (P less than 0.05). The natriuresis and kaliuresis were greater during immersion than in the supine position but plasma renin activity, measured only in trained groups, and plasma aldosterone, measured in the untrained group, were decreased similarly with both protocols. The increases in urinary sodium excretion and urine flow rate were lower in trained than untrained subjects during the supine and immersion protocols (P less than 0.05). The data are compatible with an increased osmotic but decreased volume sensitivity of ADH control in trained men.