Muscle glycogen repletion and pre-exercise glycogen content: effect of carbohydrate loading in rats previously fed a high fat diet

We have recently reported that rates of muscle glycogen repletion during the early period of recovery were increased by carbohydrate (CHO) loading in rats previously fed a high fat diet. However, the reason for this remained unanswered. The purpose of this study was to examine whether an increase of glycogen utilization due to an elevated pre-exercise glycogen store would enhance rates of glycogen repletion in muscle. Despite an equal degree of glycogen depletion, the rates of glycogen repletion of soleus, red and white gastrocnemius muscles by postexercise administration of glucose (3.0 g · kg^–1 body mass) and citrate (0.5 g · kg^–1 body mass) were faster in the CHO loaded (3 days) rats than in the nonloaded rats, as a result of elevated pre-exercise glycogen content and consequently the greater glycogen utilization. The higher rate of muscle glycogen repletion may in part be explained by increased postexercise glycogen synthase activity.     

The effects of diet on muscle pH and metabolism during high intensity exercise

Summary Five healthy male subjects exercised for 3 min at a workload equivalent to 100% on two separate occasions. Each exercise test was performed on an electrically braked cycle ergometer after a four-day period of dietary manipulation. During each of these periods subjects consumed either a low carbohydrate (3±0%, mean ±SD), high fat (73±2%), high protein (24±3%) diet (FP) or a high carbohydrate (82±1%), low fat (8±1%), low protein (10±1%) diet (CHO). The diets were isoenergetic and were assigned in a randomised manner. Muscle biopsy samples (Vastus lateralis) were taken at rest prior to dietary manipulation, immediately prior to exercise and immediately post-exercise for measurement of pH, glycogen, glucose 6-phosphate, fructose 1,6-diphosphate, triose phosphates, lactate and glutamine content. Blood acid-base status and selected metabolites were measured in arterialised venous samples at rest prior to dietary manipulation, immediately prior to exercise and at pre-determined intervals during the post-exercise period. There was no differences between the two treatments in blood acid-base status at rest prior to dietary manipulation; immediately prior to exercise plasma pH (p<0.01), blood (p<0.01), plasma bicarbonate (p<0.001) and blood base-excess (p<0.001) values were all lower on the FP treatment. There were no major differences in blood acid-base variables between the two diets during the post-exercise period. Compared with the CHO diet, the FP diet resulted in plasma alanine (p<0.05), blood lactate (p<0.05), and plasma glutamine (p<0.01) levels being lower immediately prior to exercise; plasma free fatty acids (FFA; p<0.05), glycerol (p<0.01), urea (p<0.001) and blood 3-hydroxybutyrate (3-OHB; p<0.01) levels were all higher. After the FP diet blood alanine, lactate and plasma glutamine levels were lower for the whole or the majority of the post-exercise period, while the concentrations of plasma FFA, glycerol, urea and blood 3-OHB and glucose were higher. There was no difference between the diets in pre-exercise glucose and insulin levels and post-exercise insulin levels. There was no difference in muscle pH between the two diets immediately prior to exercise; the decline in muscle pH was 104% greater during exercise on the FP diet resulting in a significant difference in post-exercise pH (p=0.05). The FP diet resulted in 23% decline in muscle glutamine levels, resulting in lower levels (p<0.05) immediately prior to exercise. Exercise had no influence on muscle glutamine levels after the FP diet but produced a 17% decline on the CHO diet. Muscle glycogen content increased by 23% on the CHO diet, but was unchanged after the FP diet. This resulted in levels being significantly different prior to exercise (p<0.05). The decline in muscle glycogen content during exercise was 50% greater on the CHO diet. There were no differences when comparing the two dietary treatments in any of the pre-exercise glycolytic intermediates measured. Immediately post-exercise glucose 6-phosphate levels were 22% higher and fructose 1,6-diphosphate levels were 130% lower on the FP diet. There were no differences between the two diets in muscle triose phosphate or lactate levels at any point of the study. The present study demonstrates that a FP diet can induce metabolic acidosis and may reduce pre-exercise muscle buffering capacity, which may then influence subsequent exercise performance. However, this appears not to influence the efflux of H⁺ from muscle during and after high intensity exercise.     

Effect of different types of high carbohydrate diets on glycogen metabolism in liver and skeletal muscle of endurance-trained rats

Male Wistar rats were fed ad libitum four different diets containing fructose, sucrose, maltodextrins or starch as the source of carbohydrate (CH). One group was subjected to moderate physical training on a motor-driven treadmill for 10 weeks (trained rats). A second group received no training and acted as a control (sedentary rats). Glycogen metabolism was studied in the liver and skeletal muscle of these animals. In the sedentary rats, liver glycogen concentrations increased by 60%–90% with the administration of simple CH diets compared with complex CH diets, whereas skeletal muscle glycogen stores were not significantly affected by the diet. Physical training induced a marked decrease in the glycogen content in liver (20%–30% of the sedentary rats) and skeletal muscle (50%–80% of the sedentary rats) in animals fed simple (but not complex) CH diets. In liver this was accompanied by a two-fold increase of triacylglycerol concentrations. Compared with simple CH diets, complex CH feeding increased by 50%–150% glycogen synthase (GS) activity in liver, whereas only a slight increase in GS activity was observed in skeletal muscle. In all the animal groups, a direct relationship existed between tissue glucose 6-phosphate concentration and glycogen content (r = 0.9911 in liver, r = 0.7177 in skeletal muscle). In contrast, no relationship was evident between glycogen concentrations and either glycogen phosphorylase activity or adenosine 5-monophosphate tissue concentration. The results from this study thus suggest that for trained rats diets containing complex CH (compared with diets containing simple CH) improve the glycogenic capacity of liver and skeletal muscle, thus enabling the adequate regeneration of glycogen stores in these two tissues.     

Effect of short-term exercise training on muscle glycogen in resting conditions in rats fed a high fat diet

Summary It has been reported that exercise training increases muscle glycogen storage in rats fed a high carbohydrate (CHO) diet in resting conditions. The purpose of this study was to examine whether a 3-week swimming training programme would increase muscle glycogen stores in rats fed a high-fat (FAT) diet in resting conditions. Rats were fed either the FAT or CHO diet for 7 days ad libitum, and then were fed regularly twice a day (between 0800 and 0830 hours and 1800 and 1830 hours) for 32 days. During this period of regular feeding, half of the rats in both dietary groups had swimming training for 3 weeks and the other half were sedentary. The rats were not exercised for 48 h before sacrifice. All rats were killed 2 h after their final meal (2030 hours). The glycogen contents in red gastrocnemius muscle, heart and liver were significantly higher in sedentary rats fed the CHO diet than in those fed the FAT diet. Exercise training clearly increased glycogen content in soleus, red gastrocnemius and heart muscle in rats fed the CHO diet. In rats fed the FAT diet, however, training did not increase glycogen content in these muscles or the heart. Exercise training resulted in an 87% increase of total glycogen synthase activity in the gastrocnemius muscle of rats fed the CHO diet. However, this was not observed in rats fed the FAT diet. The total glycogen phosphorylase activity in the gastrocnemius muscle of the rats of both dietary groups was increased approximately twofold by training. These results suggested that muscle glycogen was enhanced in rats fed the CHO diet and that the glycogen content of the muscle of rats fed the FAT diet was not increased by exercise training.     

The role of central command in ventilatory control during static exercise

The role of central command in the respiratory response to 15 min of rhythmic-static (isometric) exercise was studied in humans. Voluntary exercise (VE) was compared with electrically induced exercise (EE) at three different work intensities, i.e. 5%, 15% and 25% of maximal voluntary contraction. A group of 12 volunteers participated in the study and each of them performed six sessions. A session consisted of at least 5 min rest, 15 min rhythmic-static single leg exercise (4 s contraction/12 s relaxation) and at least 5 min recovery. Force, minute ventilation (V _E) and oxygen uptake (VO₂) were measured. In EE, both V _E and VO₂ increased continuously during the entire exercise period after an initial rapid increase at all three work intensities. Correlation between VE and VO₂ was highly significant during EE. During all three work intensities of VE, VE and VO₂ achieved a steady-state after the initial increase. During VE, VE did not correlate as closely with VO₂ as during EE. All these findings indicate that central command was not imperative for an adequate ventilatory response to exercise within all three work intensities investigated. Without the influence of central command, correlation between VE and VO₂ was even better than during VE.     

Oxidation of exogenous carbohydrate during prolonged exercise: the effects of the carbohydrate type and its concentration

Summary We studied rates of exogenous carbohydrate (CHO) oxidation during 90 min of cycling exercise in trained cyclists exercising at 70% of maximal oxygen consumption (VO_2max) when they ingested glucose, sucrose, or glucose polymer solutions at concentrations of 7.5%, 10% or 15%. Drinks were labelled with [U-¹⁴C]glucose or sucrose and were ingested at a rate of 100 ml · 10 min^–1. Rates of oxidation of the ingested CHO were calculated from the specific radio-activity of the labelled CHO, expired¹⁴CO₂ and carbon dioxide output (VCO₂). Total CHO oxidation, determined from oxygen consumption andVCO₂ was not influenced by CHO type or concentration. Gastric emptying (P=0.01) and the rate of exogenous CHO oxidation (P=0.028) was greatest for the glucose polymer solutions, and least for glucose. Although gastric emptying (P=0.006) decreased with increasing CHO concentration, CHO delivery to the intestine and exogenous CHO oxidation increased linearly with increasing CHO concentration. The percentage of the CHO delivered to the intestine that was oxidized ranged from 30.0% for 7.5% CHO to 38.1% for 15% CHO. Our results indicated that the rate of gastric emptying for CHO was not controlled to provide a constant rate of energy delivery as is commonly believed and that factors subsequent to gastric emptying limit the rate of exogenous CHO oxidation from the ingested solution.     

Effects of prolonged physical exercise and fasting upon plasma testosterone level in rats

Summary Prolonged physical exercise and fasting in male rats were studied to determine the effect of these two treatments on plasma testosterone level. Blood and tissue samples were drawn after 1 h, 3 h, 5 h, and 7 h treadmill running, and after 24 h, 48 h, and 72 h of fasting. Both treatments resulted in a significant fall in plasma testosterone, plasma luteinizing hormone (LH), plasma Insulin (IRI) and in liver and muscle glycogen stores. In the course of these two treatments the injection of a supra maximal dose of Human Chorionic Gonadotropin (HCG) produced a rise in plasma testosterone similar to that in control rats. This indicates that the decrease of plasma LH may be responsible for the decrease in plasma testosterone, which is time-related with the decrease in glycogen stores. The possible metabolic role of the decrease in plasma testosterone is discussed.     

Post-exercise ketosis and the glycogen content of liver and muscle in rats on a high carbohydrate diet

Summary Post-exercise ketosis is known to be suppressed by physical training and by a high carbohydrate diet. As a result it has often been presumed, but not proven, that the development of post-exercise ketosis is closely related to the glycogen content of the liver. We therefore studied the effect of 1 h of treadmill running on the blood 3-hydroxybutyrate and liver and muscle glycogen concentrations of carbohydrate-loaded trained (n=72) and untrained rats (n=72). Resting liver and muscle glycogen levels were 25%–30% higher in the trained than in the untrained animals. The resting 3-hydroxybutyrate concentrations of both groups of rats were very low: <0.08 mmol·1⁻¹. Exercise did not significantly influence the blood 3-hydroxybutyrate concentrations of trained rats, but caused a marked post-exercise ketosis (1.40±0.40 mmol·1⁻¹ 1 h after exercise) in the untrained animals, the time-course of which was the approximate inverse of the changes in liver glycogen concentration. Interpreting the results in the light of similar data obtained after a normal and low carbohydrate diet it has been concluded that trained animals probably owe their relative resistance to post-exercise ketosis to their higher liver glycogen concentrations as well as to greater peripheral stores of mobilizable carbohydrate.     

The effect of exercise training on glycogen,glycogen synthase and phosphorylase in muscle and liver

Summary It is thought that exercise training in both man and the rat results in a protective effect against the depletion of carbohydrate stores during exercise (glycogen-sparing). However there has been no comprehensive study of the effects of training on glycogen anabolic and catabolic enzymes with liver or muscle. The aim of this study was to examine whether changes in these enzymes occur and whether these changes may provide an explanation for the glycogen-sparing which results from exercise training.Male rats were trained by a treadmill running program at three different workloads. In addition, there were three control groups: free eating (SF), food restricted (SR), and one SF with a single bout of exercise prior to sacrifice.Exercise training was associated with a 60–150% increase in glycogen synthase and phosphorylase and a 50–70% increase in glycogen content in soleus, an intermediate muscle, but not in extensor digitorum longus (EDL), a white muscle nor in liver. The increase in glycogen synthase and phosphorylase in intermediate muscle was proportional to the degree of training and there was a significant correlation between glycogen content, glycogen synthase, and phosphorylase activity in intermediate muscle. Cytochrome c oxidase activity, an indicator of respiratory capacity, increased 50% in gastrocnemius of trained rats and was significantly correlated with glycogen synthase and phosphorylase in soleus.These results indicate a significant effect of exercise training on glycogen anabolic and catabolic enzymes in intermediate muscle, with no significant effects in white muscle or liver. The changes do not provide an explanation for glycogen-sparing, but are consistent with improved capacity of intermediate muscle for rapid glycogen mobilisation and repletion.     

Effect of a high-carbohydrate diet intake on muscle glycogen repletion after exercise in rats previously fed a high-fat diet

Summary The effect of a high-carbohydrate (C) diet intake on muscle glycogen repletion during the early period of recovery from exercise was studied in rats previously fed a high-fat (F) diet. In experiment 1, 3 weekold male and in experiment 2, 3 week-old female rats were used. Rats were fed either the F or the C diet for 2–10 weeks ad libitum and then were meal-fed regularly twice a day for 25 days in experiment 1, or for 5 weeks in experiment 2. During the period of regular feeding, half of the rats in both dietary groups continued to eat as before (F-F and C-C) but the other half of the rats were switched to the counterpart diets (F-C and C-F) in experiment 1. In experiment 2, half of the F-F group were switched to the C diet (F-C) for 3, 7, and 14 days after the period of regular feeding. Pre-exercise glycogen content in soleus, red gastrocnemius, and heart muscles and liver was higher in rats fed the C diet (C-C and F-C) than in rats fed the F diet (F-F and C-F) in experiment 1. Glycogen repletion in red muscle 2 h after the ingestion of a glucose and citrate (3.0 and 0.5 g, respectively, per kg body mass) drink was also higher in the former than in the latter. There was a positive relationship in skeletal muscles between pre-exercise glycogen content and the rate of glycogen repletion. Compared with the rats maintained on the F diet (F-F), the rats switched to the C diet (F-C) for 3 and 7 days showed faster glycogen repletion in soleus and/or red gastrocnemius muscles in experiment 2. These results indicated that the poor capacity of restoration of skeletal muscle glycogen in rats previously fed the F diet was improved by the short-term dietary switch to the C diet.     

Dynamics of anaerobic and aerobic energy supplies during sustained high intensity exercise on cycle ergometer

Eight male subjects were examined for the transition from anaerobic to aerobic energy supplies during supramaximal pedalling for 120s on a cycle ergometer. The O₂ debt and O₂ deficit were measured for anaerobic supply, while O₂ intake during exercise was measured for aerobic supply. The lactic acid system was also observed through postexercise peak blood lactate concentration [la^–]_b,peak. Since a continuous observation of O₂ debt and [la^–]_b,peak during a single period of pedalling is not possible, pedalling of seven varying durations (5,15,30,45,60,90 and 120 s) were repeated. Mechanical power output reached its peak immediately after the beginning of exercise, then rapidly declined, becoming gradual after 60 s. The O₂ debt and O₂ deficit were highest immediately after the beginning of exercise, then rapidly decreased to nil in 60 s. The 0₂ intake was small at the beginning, then rapidly increased to attain a steady state in 30 s at 80%–90% of the maximal 02 intake of the subject. Energy supply from the lactic acid system indicated by the increment in [la^–]_b,peak reached its highest value during the period between 5 and 15 s, then rapidly decreased to nil in 60 s. The results would suggest that anaerobic supply was the principal contributor during the initial stage of exercise, but that aerobic supply gradually took over. In 60 s anaerobic supply ceased, and aerobic supply became the principal contributor. The cessation of anaerobic energy supply took place much sooner than the 2 min that is conventionally suggested.     

Single and choice reaction time during prolonged exercise in trained subjects: influence of carbohydrate availability

The aim of the present study was to examine the effects of prolonged exercise at the ventilatory threshold and carbohydrate ingestion on single (SRT) and choice (CRT) reaction time. Eight well-trained triathletes completed three testing sessions within a 3-week period. Maximal oxygen uptake was determined in the first test, whereas the second and the third sessions were composed of a 100-min run (treadmill 15 min, overground 70 min, treadmill 15 min) performed at the velocity associated with the ventilatory threshold. During these submaximal tests, the subjects ingested (in random order) 8 ml·kg^–1 body weight of either a placebo (Pl) or 5.5% carbohydrate (CHO) solution prior to the first submaximal run and 2 ml·kg^–1 body weight every 15 min after that. The cognitive tasks were performed before and after exercise for CRT, and before, during each submaximal run and after exercise for SRT. Furthermore, at the end of each submaximal test subjects were asked to report their rating of perceived exertion (RPE). Results showed a significant positive effect of CHO ingestion on RPE and CRT performance at the end of exercise, while no effect of exercise duration was found in the Pl condition. After a 100-min run, during the CHO condition, CRT mean (SD) group values decreased from 688.5 (51) ms to 654 (63) ms, while during the Pl condition, RPE mean group values increased from 11 (2) to 16 (1.02) and CRT mean values remained stable [688 (104) ms vs 676 (73.4) ms, P>0.05]. No similar effect was observed for SRT. These results suggest that CHO-electrolyte ingestion during a100-min run results in an improvement in the complex cognitive performance measured at the end of that run. Electronic Publication     

The effects of various warming up intensities and durations during a short maximal anaerobic exercise

Summary In the literature, few experiments deal with the study of warming up before short exercises. The present paper investigates the influence of different warming up procedures on a short maximal anaerobic exercise leading to exhaustion in 1 min or less.Performance, heart rate, oxygen consumption, and lactic acid level are measured. The performance is improved when light warming up (30% VO₂ max) is used just before the criterion exercise, while it is impaired with a more strenuous warming up (75% VO₂ max). After light warming up, heart rate and oxygen consumption are slightly higher during the criterion exercise as compared with the values without warming up. Warming up itself does not lead to an increase in lactic acid level. When a resting period is introduced between warming up and exercise, no modification of performance occurs whatever the warming up intensity, and no important variation of the physiological measures are observed in this case.     

The effect of corrective surgery on energy expenditure during ambulation in children with cerebral palsy

Summary Mechanical efficiency, heart rate, blood lactate, and some other variables were studied in six children with cerebral palsy who walked on a treadmill before and after corrective surgery. During each test, conducted at each child's naturally selected speed, two situations were studied: steady state level walking for 9 min, and then walking at an increasing inclination up to 20% for another 10 min. During the test the subjects were allowed to hold on to a handrail to eliminate the risk of falling off the treadmill. The corrective surgery resulted in a 5% reduction in oxygen consumption per kg body mass during level walking. The subjects' levels of physical fitness, as estimated from oxygen pulse, however, were unchanged. These results are indicative of a biomechanical improvement due to the corrective surgery. While walking at a 20% inclination the subjects off loaded themselves to different degrees on the handrail which influenced the results. Their feeling of exhaustion at this load was probably due to local factors, since heart rate was well below maximal values, and blood lactate, respiratory exchange ratio and ventilatory equivalent also indicated that they were below their anaerobic thresholds (50–60% of maximal oxygen uptake).     

Prolonged stage duration during incremental cycle exercise: effects on the lactate threshold and onset of blood lactate accumulation

The aim of this study was to investigate whether increasing the duration of workloads from 3 min to 8 min during incremental exercise would influence workload (W), oxygen consumption ( ) and heart rate (HR) at the lactate threshold (LT) and the onset of blood lactate accumulation(OBLA). Two groups of six male cyclists were assigned to a well-trained (WT) and recreational (REC) group on the basis of their performance in a maximal incremental ramp test. Each subject then performed two incremental lactate tests (EXT) consisting of six workloads of either 3 min (EXT_3-min) or 8 min (EXT_8-min) duration. At the completion of each workload whole capillary blood samples were obtained for the determination of blood lactate (BLa) concentration (mM). Power output (Watts, W), HR and were averaged in the final minute of each workload as well as in the third minute of the EXT_8-min. The workload, HR and at the LT and OBLA were subsequently determined from the data of EXT_3-min and EXT_8-min. The results demonstrate that workload and , but not HR, at the LT and OBLA were higher in the WT cyclists. At the same time, the workload at the LT obtained from the results of the EXT_3-min was significantly (P<0.05) higher then the value obtained in the EXT_8-min in the WT subjects but not the REC subjects. However, the workload, and HR at the OBLA, together with the and HR at the LT were not significantly different when calculated from data obtained from EXT_3-min or EXT_8-min. The data obtained in this study suggest that incremental exercise protocols using workloads of duration longer than 3 min have the effect of increasing the workload at the LT in well-trained cyclists. However, the OBLA determined in exercise tests using stage increments of either 3 min or 8 min is similar in cyclists of different training status. Electronic Publication     

Metabolic effects of testosterone during prolonged physical exercise and fasting

Summary Previous studies have shown a decrease in plasma testosterone during prolonged physical exercise and 72 h fasting in rats.To determine whether this hormonal change has an influence upon energy metabolism, two experiments were carried out, in which the plasma levels of testosterone were elevated during prolonged physical exercise and fasting in male wistar rats.The effects of acute and chronic increases in the levels of circulating testosterone were studied, on the one hand after human chorionic gonadotropin (H.C.G.) injection, and on the other by prolonged testosterone perfusion with an osmotic minipump. Blood and tissue sampling were performed to evaluate blood glucose, alanine, and lactate, and tissue glycogen. The results in fed and rest control rats showed no changes in blood parameters under the effect of hypertestosteronemia but there was an increase in muscle glycogen after testosterone perfusion.In 72 h fasted rats both types of hypertestosteronemia were associated with a decrease in blood alanine and lactate ranging from 25% to 35%. Only testosterone perfusion was associated with higher concentrations of muscle glycogen.After 7 h of treadmill running, testosterone perfusion and H.C.G. injection induced a 35% decrease in blood alanine and a slight decrease in blood glucose, with no change in other parameters.Whereas an elevation in the level of testosterone can induce muscle glycogen compensation in the fed resting state, it cannot counteract the exhaustion of muscle glycogen during running.     

The effects of induced alkalosis on the metabolic response to prolonged exercise in humans

To examine the effects of alkalosis on the metabolic response to prolonged exercise, seven healthy males cycled for 1 h at approximately 70% of maximum oxygen uptake on two occasions, 1-week apart. Starting 3 h prior to exercise, subjects consumed either CaCO₃ (placebo) or NaHCO₃ (0.3 g · kg^–1 body mass) over a 2-h period. Arterialised-venous blood samples were drawn before and during exercise for the determination of acid-base status and blood metabolites (lactate, glucose, glycerol and plasma free fatty acids). Expired gas was collected during exercise for determination of oxygen uptake and respiratory exchange ratio to estimate fuel oxidation rates. Ratings of perceived exertion (RPE) and heart rates were also recorded. A significant (P < 0.01) alkalosis was observed at all times following bicarbonate ingestion. Blood lactate was significantly (P < 0.05) higher at all sample times throughout exercise following bicarbonate ingestion. Blood lactate concentration [mean (SEM)] reached peak values of 2.90 (0.16) and 4.24 (0.45) mmol · l^–1 following 20 min of exercise following placebo and bicarbonate, respectively. No differences between treatments were noted at any time for the other metabolites. and RPE were significantly higher (P < 0.01) with the bicarbonate trial. At a constant power output increases in are generally associated with increases in fat oxidation, however, no evidence for an altered fuel oxidation was obtained in the present study. The differences in blood lactate indicate that induced alkalosis increased lactate efflux from muscle, but it cannot be confirmed whether this represents an increased rate of glycolysis within the muscle.     

The effects of a single bout of exercise on resting energy expenditure and respiratory exchange ratio

We investigated the effects of a single bout of aerobic and resistance exercise of similar relative intensity and duration on resting energy expenditure (REE) and substrate utilisation. Ten young healthy males volunteered [age 22 (1.8) years, weight 76 (7.9) kg, height 176 (4.1) cm, percentage body fat 10.5 (4.0)%; mean (SEM)]. They randomly underwent three conditions in which they either lifted weights for 60 min at 70–75% of 1-RM (WL), ran for 60 min at 70–75% of maximal oxygen intake (R) or did not exercise (C). REE and substrate utilisation, determined via respiratory exchange ratio (R), were measured prior to exercise, and 10, 24, 48 and 72 h post-exercise. It was revealed that REE was significantly elevated (P<0.05) 10 and 24 h after the end of WL [2,124 (78) and 2,081 (76) kcal, respectively] compared to pre-exercise [1,972 (82) kcal]. REE was also significantly increased (P<0.05) 10 and 48 h after the completion of R [2,150 (73) and 1,995 (74) kcal, respectively] compared to pre-exercise data [1,862 (70) kcal]. R was lower 10 and 24 h following either WL or R [0.813 (0.043); 0.843 (0.040) and 0.818 (0.021); 0.832 (0.021), respectively] compared to baseline measurements [0.870 (0.025) and 0.876 (0.04), respectively]. Creatine kinase was significantly elevated (P<0.05) 24 h after both WL and R, whereas delayed onset muscle soreness became significantly elevated (P<0.05) 24 h after only WL. There were no significant changes for any treatment in thyroid hormones (T₃ and T₄). These results suggest that a single bout of either WL or R exercise, characterised by the same relative intensity and duration, increase REE and fat oxidation for at least 24 h post-exercise.     

Effects of short-term dietary change from high fat to high carbohydrate diets on the storage and utilization of glycogen and triacylglycerol in untrained rats

The effects of short-term diet change from high fat (F) to high carbohydrate (C) (or vice versa) on the storage and utilization of glycogen and triacylglycerol (TG) in muscle and liver were studied in untrained rats. Rats were fed on an F or C diet for 28 days. For an additional 3 days, half of the rats in both F and C groups were fed the same diets as before (F-F and C-C) and the other half of the rats were switched to the counterpart diets (F-C and C-F). On the final day of the experiment, half of the rats in each diet group were exercised by swimming for 1.5 h and the other half were rested. Short-term diet change from F to C diets increased, but the change from C to F diets decreased, glycogen stores of soleus and plantaris muscles and liver, resulting in no difference in glycogen stores between F-C and C-C, and between F-F and C-F. The dietary change also had an affect on TG stores of red gastrocnemius muscle and liver - however, muscle TG stores were still higher in F-C than in C-C and C-F, and there were no differences in liver TG stores between F-C and C-F. Exercise decreased muscle glycogen contents markedly in F-C and C-C, whereas, it decreased muscle TG concentrations in F-F and C-F. Liver glycogen depletion was lower in F-C than in other groups. Lipolytic activities of epididymal adipose tissue at rest and postexercise were no differences between F-F and F-C, and were higher in F-C than in C-C and C-F. -adrenergic receptor binding was determined with [¹²⁵I] iodocyanopindolol, and maximal numbers of -adrenergic receptor of plasma membrane from perirenal adipose tissue were approximately 170%–200% higher in F-C than in other groups at rest and postexercise. These results suggested that short-term C diet fed rats adapted to F diet enhanced not only glycogen stores of muscle and liver but also did not decrease lipolytic activity of adipose tissue with increased -adrenergic receptor density, resulting in the preservation of energy reserves (glycogen and TG) of muscle at rest, and liver glycogen sparing during exercise.     

Effects of low and high levels of moderate hypoxia on anaerobic energy release during supramaximal cycle exercise

The purpose of this study was to investigate whether hypoxia can alter anaerobic energy release during supramaximal exercise. Seven male subjects performed 12 submaximal cycling tests to establish the relationship between workload and O₂ demand. The subjects also performed 40 s Wingate tests (WT) under normoxia (room air), two levels of moderate hypoxia of 16.4% O₂ and 12.7% O₂. We measured the power output and oxygen uptake (VO₂) during each test and estimated the O₂ demand, O₂ deficit and percentage of anaerobic energy release (%AnAER). These data were analyzed for each 20 s interval. At all intervals, there were no differences in Pmean·body mass (BM)⁻¹, O₂ demand·BM⁻¹ or O₂ deficit·BM⁻¹ among the three O₂ conditions. However, under hypoxia of 12.7%, VO₂·BM⁻¹ was significantly decreased and %AnAER was significantly increased in the late phase (20–40 s) of the WT, compared to normoxia (P<0.05). There were no such significant differences between normoxia and hypoxia of 16.4%. Thus, the present results show that the degree of hypoxia affects the magnitude of the hypoxia-induced increase in anaerobic energy release in the late phase of the WT and suggest that certain degrees of hypoxia induce significant increases in the amount of anaerobic energy released, compared to normoxia.