Plasma volume change during heavy-resistance weight lifting

Blood samples were obtained from six young men before, and over a 60-min period following a bout of heavy-resistance weight lifting to determine changes in plasma volume. Weight lifting consisted of three sets of four exercises (arm curl, bench press, bent-arm row, and squat) performed using 70% of one-repetition maximum for as many repetitions as possible. Plasma volume change was determined from haematocrit and haemoglobin concentration. During weight lifting, mean oxygen uptake and heart rate were 1.96 L X min-1 and 158 bt X min-1, respectively. Plasma volume was decreased -14.3% (p less than 0.05) immediately following exercise and -7.0% (p less than 0.05) at 15 min into recovery, but had returned to the resting level within 30 min. It was concluded that heavy-resistance weight lifting elicits a significant decrease in plasma volume, which is similar in magnitude to that observed during running and cycling at 80-95% of maximal oxygen uptake.     

Time-dependent influence of some sedating agents on basic haematological values in various artio- and perissodactylids

Basic haematological values in 32 animals of five species were estimated after administration of sedating agents. In all species under investigation, a time-dependent decrease of erythrocyte counts, haematocrit values and haemoglobin content was noted during the first 30 min after sedation, for the following 30 min the lowered values remained essentially without any change in zebras. Derived parameters, mean corpuscular haemoglobin, mean corpuscular Hb concentration and mean corpuscular volume did not change during the period of observation. Only insignificant changes in leukocyte count and in the proportion of lymphocytes and neutrophiles were registered. The shortest possible time between sedation and blood sampling is recommended to minimalize a distortion especially in the red blood picture.     

Haematological effects of stress on a teleost, Esox lucius L.

Stress produces a haemoconcentration, elevated blood lactate, increased glucose concentrations and alters the plasma electrolyte balance in two groups (brackish- and freshwater) of the northern pike, Esox leucius L., after one month's starvation. A method for dorsal aorta catheterization and a receptacle for cannulating fish is described.
The blood glucose level of the freshwater pike was twice that of the brackish-water group, and the plasma sodium and magnesium concentrations in the brackish-water pike were significantly higher. The haematocrit, haemoglobin and blood lactic acid concentrations were higher in freshwater pike. The plasma potassium and calcium concentrations in the two groups did not differ.
Haemoconcentration due to stress by handling for 1.5 min was shown by changes in haematocrit and haemoglobin values. The haemoglobin concentration returned to normal in freshwater pike after 4 h but in brackish-water pike after 12 h.
As a result of handling, the blood lactic acid level rose steeply and required 12 h to return to normal.
The blood glucose concentration rose to its maximum value within 1 h of handling and required two days to return to normal.
The plasma sodium level remained stable after handling, but the potassium level was erratic. In brackish-water, the potassium concentration of the pike remained high for 12 h after stress, but in the freshwater group, after a rise, the concentration fell to below the initial level within 4 h. The changes of the potassium concentrations in relation to sampling time are discussed. The changes in the divalent ion concentrations were marked and similar in the two groups; with an increase lasting 1–4 h and then a fall below the initial level, which was regained after two days.     

Comparison of stress induced by manual restraint and immobilisation in the estuarine crocodile,Crocodylus porosus

This study compared the stress induced in captive estuarine crocodiles, Crocodylus porosus, by two different handling methods: manual restraint (noosing with ropes) and immobilization by electro-stunning. To stun, a short charge (approx. 6 s) at 110 V was delivered to the back of the necks of C. porosus using a custom-built device, which immobilized the animals for 5-10 min. Immobilized and restrained animals were measured and sexed, and the condition of the skin assessed. Blood samples were taken from some animals immediately after restraint or immobilization. Other animals were returned to their pens to recover for periods of 30 min, 1, 4, 12, 24 or 48 hours after which they were stunned and blood samples taken. Individual animals (mean body length 1.96 m, N=99) were bled only once. Haematocrit and haemoglobin concentrations were measured and plasma samples were analysed for corticosterone, glucose and lactate levels. Following restraint, there were significant increases in haematocrit, haemoglobin, glucose, lactate and corticosterone concentrations in C. porosus. For restrained animals, recovery to baseline levels occurred after approximately 8 hours. The stress response of stunned animals was significantly reduced compared to manually captured and restrained crocodiles. Both groups showed a significant increase in haematocrit, haemoglobin concentration and lactate levels, however the magnitude of change was significantly reduced, and recovery was faster in stunned animals. No increase in either glucose or corticosterone levels occurred with immobilisation. The results imply that immobilization by electro-stunning is much less stressful.     

Oxygen consumption following exercise of moderate intensity and duration.

To study the effects of exercise intensity and duration on excess postexercise oxygen consumption (EPOC), 8 men [age = 27.6 (SD 3.8) years, VO2max = 46.1 (SD 8.5) ml min-1 kg-1] performed four randomly assigned cycle-ergometer tests (20 min at 60% VO2max, 40 min at 60% VO2max, 20 min at 70% VO2max, and 40 min at 70% VO2max). O2 uptake, heart rate and rectal temperature were measured before, during, and for 1 h following the exercise tests. Blood for plasma lactate measurements was obtained via cannulae before, and at selected times, during and following exercise. VO2 rapidly declined to preexercise levels following each of the four testing sessions, and there were no differences in EPOC between the sessions. Blood lactate and rectal temperature increased (P < 0.05) with exercise, but had returned to preexercise levels by 40 min of recovery. The results indicate that VO2 returned to resting levels within 40 min after the end of exercise, regardless of the intensity (60% and 70% VO2max) or duration (20 min and 40 min) of the exercise, in men with a moderate aerobic fitness level.     

Is there an optimal haematocrit for rainbow trout,Oncorhynchm mykiss (Walbaum)? An interpretation of recent data based on blood viscosity measurements

The viscosity of blood from rainbow trout was measured following manipulation of haematocrit by bleeding, hypoxia. exercise, and anaesthesia. Blood viscosity when measured at high shear rate (225 s ¹) was proportional to haematocrit, but the dependence of viscosity on shear rate was far less for swollen erythrocytes from exercised and anaesthetized trout. Erythrocyte swelling was most marked in exercised and anaesthetized trout, and is a confounding factor when considering the effect of haematocrit on viscosity.
The viscosity of blood with variable haematocrit, but constant mean cell Hb concentration, indicated that the relative oxygen transport capacity in trout was optimal at a haematocrit of 30%. Data from this, and earlier studies show that haematocrit in trout is variable and labile, yet none of the haematocrit values following manipulations are less than 85% of optimal. Optimal haematocrit is however, significantly higher than measured values from either cannulated or acutely venesected resting trout.     

The Ratio of sTfR/Ferritin is Associated with the Expression Level of TfR in Rat Bone Marrow Cells After Endurance Exercise

Currently, it is unclear which index of haematological parameters could be used to most easily monitor iron deficiency during endurance training. To address this question, 16 male Wistar rats were randomly assigned to two groups: a sedentary group (n = 8) and an exercised group (n = 8). Initially, animals in the exercise group started running on a treadmill at a rate of 30 m/min, on a 0% grade, for 1 min/session. Running time was gradually increased by 2 min/day. The training plan was one session per day during the initial 2 weeks and two sessions per day during the third to ninth week. At the end of the 9-week experiment, we analysed the blood of the experimental animals for haemoglobin levels, erythrocyte numbers, haematocrit, serum iron levels, total iron binding capacity, transferrin saturation, serum ferritin levels and soluble transferrin receptor (sTfR) levels, and we calculated the ratio of sTfR/ferritin. Erythrocyte numbers, haemoglobin levels and haematocrit values were decreased after 9 weeks of exercise, but sTfR and sTfR/ferritin values were increased (P < 0.01 or P < 0.05). The training regime significantly increased TfR mRNA levels in the bone marrow cells of the exercised rats compared with the sedentary group (1.8 ± 0.5 vs. 1.1 ± 0.2, P < 0.01). These results revealed a significant correlation between TfR levels in the bone marrow cells and the ratio of sTfR/ferritin (r = 0.517; P < 0.01) and sTfR levels (r = 0.206; P < 0.05) in sedentary and exercised rats. In conclusion, we show that sTfR indices and the ratio of sTfR/ferritin could be useful indicators for monitoring iron deficiency during endurance training.     

Ventilatory and treadmill endurance during acute semistarvation

Little is known about respiratory muscle function in acute undernutrition, although an inadequate caloric intake is common in numerous disease states. Twelve young-adult, healthy female volunteers performed two familiarization experiments and were then studied after 7 days of consuming 40% of normal daily caloric intake as well as after 1 wk of normal caloric intake. In each experiment subjects performed tests of resting pulmonary function, inspiratory muscle strength, and ventilatory endurance, the last of which involved two 60-s and two 6-min isocapnic maximum voluntary ventilation maneuvers. Subjects then walked to exhaustion in 8-20 min on a treadmill. The caloric restriction did not affect performance of any breathing test but did lower endurance time in severe treadmill exercise (P less than 0.05). Basal metabolic rate was lowered, resting blood levels of free fatty acids and beta-hydroxybutyrate elevated, and glucose lowered following the caloric restriction (P less than 0.05). Blood lactate levels were lower during and after exercise following caloric restriction (P less than 0.05). We conclude that ventilatory muscle strength and endurance are fully preserved in caloric restriction severe enough to cause mild ketoacidosis and hypoglycemia, lowered basal metabolic rate, and decreased endurance in severe treadmill exercise.     

Progesterone and LH variations after LH-RH administration in the luteal phase of the menstrual cycle

We have investigated the pituitary and luteal responses to LH-RH and their related changes. 11 normal women were studied during the luteal phase (day +4/+11). Blood samples were collected every 15 min for a basal period of 180 and 120 min after the intravenous administration of 25 micrograms of LH-RH. Progesterone (P) and LH were assayed by radioimmunoassay. Data were analyzed as maximum peak and its percent increase (delta max), integrated secretory area (ISA) and percent increase of ISA (delta A) in respect to basal values for both P and LH. LH-RH elicited a secretory response of both hormones in all cases. ISA of LH was significantly greater after LH-RH administration in respect to basal values (p less than 0.001) and delta max accounted to 475 +/- (SE) 36% of the basal concentration. Luteal responsiveness varied from about 115-130% to more marked increments. ISA of P differed from basal to stimulated conditions (p less than 0.05) and delta max was 166 +/- (SE) 14%. The analysis of temporal relationship between P and LH secretion showed that LH promptly rose after LH-RH, while the enhancement of P plasma levels occurred within 31 +/- 19 min after LH rise. Then P levels reached a plateau, values of which were statistically different from those observed before LH-RH administration. In two cases where luteal function was blunted or absent, in spite of marked increments of LH, P secretion did not occur. These data are consistent with the presence of close relationships between hypothalamic, pituitary and luteal functions and strengthen the contention about the usefulness of LH-RH during luteal phase for the lifespan and maintenance of corpus luteum.     

The influence of fitness on neuroendocrine responses to exhaustive treadmill exercise

Neuroendocrine and sympathoadrenal responses to exhaustive graded treadmill exercise were examined in 17 male subjects of varying degrees of fitness. The mean duration of exercise to exhaustion was 15.2 +/- 0.7 (+/- SE) min. Exercise duration was inversely correlated with baseline heart rate (P less than 0.05). Compared to standing baseline values, mean plasma norepinephrine and epinephrine levels increased 339% and 301%, respectively, in an integrated 2-min blood sample collected immediately after completion of exercise. Mean adrenocorticotrophic hormone (ACTH), beta-endorphin (beta-EP), beta-lipotropin (beta-LPH), and prolactin levels increased 282%, 720%, 372%, and 211%, respectively, in an integrated 4-min blood sample beginning 2 min after completion of exercise. Cortisol levels increased 183% in the sample collected 17-21 min after exercise. The magnitude of these neuroendocrine responses to exercise was similar among individuals at the same relative intensity of exhaustive exercise, regardless of the duration of exercise. The exercise-induced increases of the pro-opiomelanocortin (POMC)-derived peptides, ACTH, beta-EP, and beta-LPH, were highly correlated with each other (P values less than 0.001), and were correlated with prolactin increases, (P values less than 0.05). During a 20-min recovery period after exercise, changes in heart rate, ACTH, and beta-LPH levels were correlated with duration of exercise, (P less than 0.01, P less than 0.03, and P less than 0.03, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Prolonged decrease in cardiac volumes after maximal upright bicycle exercise

Sequential exercise-gated cardiac blood pool scintigrams provide a noninvasive technique for evaluating the effect of therapeutic interventions on cardiac volumes and function only if both exercise periods are equivalent in the absence of an intervention. To assess whether they are indeed equivalent, 14 healthy subjects underwent gated blood pool scintigraphy during two maximal upright exercise periods separated by 60 min without changing position. Although resting cardiac output and blood pressure returned to base-line values 60 min after the first exercise period, mean resting heart rate was markedly higher (89.4 +/- 2.7 vs. 66.5 +/- 2.5 beats/min, P less than 0.001) and upright cardiac volumes lower [39.1 +/- 4.9 vs. 56.3 +/- 6.0 ml, P less than 0.001, for end-systolic volume (ESV) and 112.6 +/- 8.0 vs. 144.9 +/- 9.0 ml, P less than 0.001, for end-diastolic volume (EDV)] than before the first exercise period. These differences persisted during low levels of the subsequent exercise but not at high and maximum work loads. Cardiac volumes and heart rate 60 min after an identical exercise protocol in a second group of 22 subjects who received propranolol, 0.15 mg/kg iv, after their initial exercise, however, were the same as those preexercise. Thus higher sympathetic tone may be responsible for the persistently higher heart rate and decreased cardiac volumes after exercise, and the assumption that cardiac volumes and function are similar during two closely spaced sequential exercise studies is not always valid.     

Glucose dependent insulinotropic polypeptide (GIP) infused intravenously is insulinotropic in the fasting state in type 2 (non-insulin dependent) diabetes mellitus

The effects of an intravenous infusion of porcine GIP on beta-cell secretion in patients with untreated type 2 diabetes mellitus have been studied. The subjects were studied on two separate days. After a 10 h overnight fast and a further 120 min basal period they were given an intravenous infusion of porcine GIP (2 pmol.kg-1.min-1) or control solution in random order from 120-140 min. Frequent plasma glucose, insulin, C-peptide and GIP measurements were made throughout and the study was continued until 200 min. Plasma glucose levels were similar throughout both tests. During the GIP infusion there was an early significant rise in insulin concentration from 0.058 +/- 0.006 nmol/l to 0.106 +/- 0.007 nmol/l (P less than 0.01) within 6 min of commencing the GIP infusion and insulin levels reached a peak of 0.131 +/- 0.011 nmol/l at 10 min (P less than 0.01). Insulin levels remained significantly elevated during the rest of the GIP infusion (P less than 0.01-0.001) and returned to basal values 20 min post infusion. No change in basal insulin values was seen during the control infusion. C-peptide levels were similarly raised during the GIP infusion and the increase was significant just 4 min after commencing the GIP infusion (P less than 0.05). GIP levels increased from 16 +/- 3 pmol/l prior to the infusion to a peak of 286 +/- 24 pmol/l 20 min later. At 4 min when a significant beta-cell response was observed GIP levels were well within the physiological range.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma cortisol and metabolite level profiles in two isogenic strains of common carp during confinement

A rapid increase in common carp Cyprinus carpio plasma cortisol levels was noted, in two experiments, after 30 mins of a 3 h net confinement, which was sustained while the fish were held in the nets. After release from the nets, cortisol levels returned to control values in 1 h. Plasma glucose and free fatty acid levels were elevated by the confinement. Glucose was increased after 30 min but returned to basal levels after 22 h of recovery while free fatty acids were not elevated until 3 h of confinement and remained high for the duration of the recovery period. After confinement for 3 h, plasma lactate levels were reduced and remained low for a further 1 h. No change in either plasma triglyceride or cholesterol levels were found during the study. Confinement had no effect on haematocrit levels but blood haemoglobin levels were reduced. In both experiments hypochloraemia occurred in response to confinement. However, values returned to pre-confinement levels 22 h after confinement. These results show that rearing isogenic carp strains, under identical conditions, results in a reproducable response to an acute stressor and that these carp respond in a similar manner to other teleost species.     

Inhalational administration of cocaine in sheep

A pipe for administration of inhaled cocaine and its pyrolytic products in laboratory animals was developed and tested. In-vitro trials showed 30.0 +/- 5.2% (mean +/- SE) recovery of cocaine in solvent. Five non-pregnant ewes were instrumented with tracheal T-tubes and vascular catheters. After surgical recovery, ewes received three doses of cocaine (free base) in a randomized fashion; 2 mg/kg and 4 mg/kg both by inhalation, and 2 mg/kg intravenously. Arterial blood samples were collected and assayed for cocaine and its major metabolites by high performance liquid chromatography. Blood pressure and heart rate were continuously recorded. Cocaine administered by inhalation was eliminated with a half-life of 1.6 +/- 0.5 min (mean +/- SE) compared to 3.4 +/- 0.9 following intravenous administration (p less than 0.03). Likewise, clearance values were greater following inhalation, 5532 +/- 1756 ml/min/kg, than following intravenous administration, 163 +/- 20.6 ml/min/kg (p less than 0.04). Both routes of administration led to significant elevations in blood pressure, 7.5% increase after smoking vs 20% increase after intravenous administration. No correlation was found between inhalational dose of cocaine and peak plasma cocaine concentration.     

Substrate usage during prolonged exercise following a preexercise meal

The effect of a high-carbohydrate meal 4 h before 105 min of exercise at 70% of maximal O2 uptake was determined in seven endurance-trained cyclists and compared with exercise following a 16-h fast. The preexercise meal produced a transient elevation of plasma insulin and blood glucose, which returned to fasting basal levels prior to the initiation of exercise. The meal also resulted in a 42% elevation (P less than 0.05) of glycogen within the vastus lateralis at the beginning of exercise. The 1st h of exercise when subjects were fed was characterized by a 13-25% decline (P less than 0.05) in blood glucose concentration, a suppression of the normal increase in plasma free fatty acids and blood glycerol, and a 45% (P less than 0.05) greater rate of carbohydrate oxidation compared with exercise when subjects were fasted. After 105 min of exercise, there were no significant differences when subjects were fed or fasted regarding blood glucose levels, rate of carbohydrate oxidation, or muscle glycogen concentration. The greater muscle glycogen utilization (97 +/- 18 vs. 64 +/- 8 mmol glucosyl units X kg-1; P less than 0.05) and carbohydrate oxidation when subjects were fed appeared to be derived from the glycogen synthesized following the meal. These results indicate that preexercise feedings alter substrate availability despite a return of plasma insulin to fasting levels prior to exercise and that these effects persist until the 2nd h of exercise.     

Why do fish die after severe exercise?

Trout fitted with dorsal aortic cannulae were subjected to 6 min of intensive exercise and monitored over the following 12 h recovery period. Delayed mortality was 40%; the majority of deaths occurred 4–8 h post-exercise. Surviving fish exhibited a short-lived haemoconcentration reflected in increased haematocrit, haemoglobin, plasma protein, Na⁺ and Ch^- levels; an extended rise in plasma [K⁺]; a quickly corrected respiratory acidosis; and a more prolonged metabolic acidosis in concert with a rise in blood lactate. Dying fish exhibited very similar trends except for a significantly greater metabolic acidosis, lower plasma [Cl^-], and the apparent accumulation of an unknown anion in the blood prior to death. Cardiac failure did not occur. Blood metabolic acid levels, while elevated, were only ∼ 50% of peak lactate anion levels and well within the normal range of tolerance, as were all other changes observed in the blood of non-survivors. The hypothesis that post-exercise mortality is due to excessive 'lactic acid' accumulation in the blood is discounted. It is suggested that intracellular acidosis may be the proximate cause of death.     

Effects of naloxone and animal temperament on serum luteinizing hormone and cortisol concentrations in seasonally anestrous Brahman heifers

The effect of endogenous opioid peptides (EOP) and individual animal temperament on serum luteinizing hormone (LH) were investigated in seasonally anestrous Brahman heifers (n = 24). Animals that had shown behavioral estrus in previous months but that had not returned to estrus for at least 30 d were selected. The heifers were ranked by temperament (tame = 1, normal = 2, wild = 3) and randomly allotted into three groups. Blood was collected from one heifer of each group per day. Blood samples were taken via jugular cannula every 15 min for 6 h and every 30 min for another 4 h. After the first hour of sampling, the heifers received intravenous saline (SAL, n = 8); naloxone (LN, 0.5 mg/kg i.v., n = 8); or naloxone (HN, 1.0 mg/kg i.v., n = 8). Three hours after naloxone treatment, each heifer was given gonadotropin releasing hormone (GnRH, 100 mug i.m.). All samples were processed to yield serum and were assayed for LH by radioimmunoassay (RIA). Hourly samples were assayed for cortisol by RIA. The area under the LH curve 60 min postnaloxone treatment was higher in LN and HN than in SAL (57.0 and 40.8 vs 6.1 units; P<0.01); and the area under the 180 min postnaloxone curve remained higher in LN than in SAL (106.2 vs 35.1 units; P<0.05). Cortisol concentrations 60 min postnaloxone administration were above prenaloxone levels(38.2 vs 26.7 ng/ml; P<0.0002). Temperament scores of heifers were positively correlated with cortisol release. The area under the cortisol curve had a negative correlation with mean LH. Serum LH concentrations appear to be suppressed by EOP in seasonally anestrous Brahman heifers, and EOP appear to reduce serum cortisol concentrations. Excitable heifers had higher concentrations of serum cortisol, which negatively affected serum LH concentrations.     

Exercise-induced functional desensitization of canine cardiac beta-adrenergic receptors

To test the hypothesis that the high levels of endogenous catecholamines associated with strenuous exercise produce functional desensitization of cardiac beta-adrenergic receptors, we measured the bolus chronotropic dose of isoproterenol necessary to produce a 25-beats/min increase in heart rate (CD25) in the resting state and after the return of heart rate to resting levels after 60 min of treadmill running in 13 normal dogs. Immediately after exercise, 12 of 13 dogs were less sensitive to the chronotropic effects of beta-adrenergic receptor stimulation: mean CD25 increased from 1.16 +/- 0.17 to 3.50 +/- 0.98 micrograms (P less than 0.02). A similar reduction in isoproterenol sensitivity was evident regardless of whether testing was performed in the presence or absence of vagal blockade with atropine. By 3 h after exercise, CD25 had returned to the preexercise level, with no further change noted 24 h after exercise. There was no change in the CD25 when measured serially in three unexercised dogs. We conclude that a single bout of dynamic exercise is sufficient to produce a significantly decreased chronotropic responsiveness to isoproterenol. This phenomenon may represent an acute but transient desensitization of cardiac beta-adrenergic receptors.     

Exercise-induced muscle glycogen depletion and repletion in diabetic rats.

The purpose of this experiment was to examine glycogen depletion in muscles of chronic diabetic rats during treadmill running of moderate intensity and glycogen repletion following the exercise bouts. Diabetes was induced with a single intravenous injection of streptozotocin (70 mg × kg^?1). Glycogen concentrations in muscles from diabetic and normal animals were determined at rest, after running either 10 or 30 min at 23 m × min^?1 (5% incline), or 2, 4, or 8 hr following 30 min of running at the same speed and incline. With the exception of soleus muscle after 30 min of running, there were no differences in muscle glycogen contents between normal and diabetic rats before exercise, immediately after exercise, or during the recovery period. All muscles showed a significant loss of glycogen during exercise, and most muscles had completely restored their glycogen by 2 hr following exercise. Blood lactate concentrations were also similar for normal and diabetic rats at rest and after exercise. It is concluded that the diabetic condition studied in this experiment did not significantly alter muscle glycogen metabolism during exercise of moderate intensity or during recovery from the activity.     

The influence of dietary manipulation on plasma ammonia accumulation during incremental exercise in man

The influence of a pattern of exercise and dietary manipulation, intended to alter carbohydrate (CHO) availability, on pre-exercise acid-base status and plasma ammonia and blood lactate accumulation during incremental exercise was investigated. On three separate occasions, five healthy male subjects underwent a pre-determined incremental exercise test (IET) on an electrically braked cycle ergometer. Each IET involved subjects exercising for 5 min at 30%, 50%, 70% and 95% of their maximal oxygen uptake (VO2max) and workloads were separated by 5 min rest. The first IET took place after 3 days of normal dietary CHO intake. The second and third tests followed 3 days of low or high CHO intake, which was preceded by prolonged exercise to exhaustion in an attempt to deplete muscle and liver glycogen stores. Acid-base status and plasma ammonia and blood lactate levels were measured on arterialised venous blood samples immediately prior to and during the final 15 s of exercise at each workload and for 40 min following the completion of each IET. Three days of low CHO intake resulted in the development of a mild metabolic acidosis in all subjects. Plasma ammonia (NH3) accumulation on the low-CHO diet tended to be greater than normal at each exercise workload. Values returned towards resting levels during each recovery period. After the normal and high-CHO diets plasma NH3 levels did not markedly increase above resting values until after exercise at 95% VO2max. Plasma NH3 levels after the high-CHO diet were similar to those after the normal CHO diet.(ABSTRACT TRUNCATED AT 250 WORDS)