Effect of carbohydrate feeding during recovery from prolonged running on muscle glycogen metabolism during subsequent exercise

This study examined the effect of carbohydrate (CHO) intake during a 4 h recovery from prolonged running on muscle glycogen metabolism during subsequent exercise. On 2 occasions, 7 male subjects ran for 90 min at 70 % maximum oxygen uptake VO(2 max) on a motorized treadmill (R1) followed by a 4 h rest period (REC) and a 15 min run (R2) consisting of 5 min at 60 % and 10 min at 70 % VO(2 max) During REC, each subject ingested a total of 2.7 l of an isotonic solution containing either 50 g of CHO (LOW) or 175 g of CHO (HIGH). Biopsy samples were obtained from the vastus lateralis immediately after R1, REC and R2. During REC, a higher muscle glycogen resynthesis was observed in HIGH when compared with LOW trial (75 +/- 20 vs. 31 +/- 11 mmol x kg dry matter (dm) -1, respectively; p < 0.01). Muscle glycogen utilization during R2 was similar between the HIGH and LOW trials (39 +/- 10 vs. 46 +/- 11 mmol x kg dm -1, respectively). These results suggest that ingestion of a large amount of CHO at frequent intervals during recovery from exercise does not affect the rate of muscle glycogen utilization during subsequent exercise.     

Effect of carbohydrate feedings on muscle glycogen utilization and exercise performance

Ten men were studied during 4 h of cycling to determine the effect of solid carbohydrate (CHO) feedings on muscle glycogen utilization and exercise performance. In the experimental trial (E) the subjects ingested 43 g of sucrose in solid form along with 400 ml of water at 0, 1, 2 and 3 h of exercise. During the control trial (C) they received 400 ml of an artificially sweetened drink without solid CHO. No differences in VO2, heart rate, or total energy expenditure were observed between trials; however, respiratory exchange ratios were significantly (P less than 0.05) higher during E. Blood glucose was significantly (P less than 0.05) elevated 20 min post-feeding in E; however, by 50 min no differences were observed between trials until 230 min (E = 4.5 +/- 0.2 mmol X l-1 vs C = 3.9 +/- 0.2, means +/- SE; P less than 0.05). Muscle glycogen utilization was significantly (P less than 0.05) lower during E (100.7 +/- 10.2 mmol X kg-1 w.w.) than C (126.2 +/- 5.5). During a sprint (100% VO2max) ride to exhaustion at the end of each trial, subjects performed 45% longer when fed CHO (E = 126.8 +/- 24.7 s vs C = 87.2 +/- 17.5; P less than 0.05). It was concluded that repeated solid CHO feedings maintain blood glucose levels, reduce muscle glycogen depletion during prolonged exercise, and enhance sprint performance at the end of such activity.     

Effect of fructose ingestion on muscle glycogen usage during exercise

Eight healthy males were studied to compare the effects of preexercise fructose and glucose ingestion on muscle glycogen usage during exercise. Subjects performed three randomly assigned trials, each involving 30 min of cycling exercise at 75% VO2max. Forty-five min prior to commencing each trial, subjects ingested either 50 g of glucose (G), 50 g of fructose (F), or sweet placebo (C). No differences in VO2 or respiratory exchange ratio were observed between the trials. Blood glucose was elevated (P less than 0.05) as a result of the glucose feeding. With the onset of exercise, blood glucose declined rapidly during G, reaching a nadir of 3.18 +/- 0.15 (SE) mmol X 1(-1) at 20 min of exercise. This value was lower (P less than 0.05) than the corresponding values in F (3.79 +/- 0.20) and C (3.99 +/- 0.18). No differences in exercise blood glucose levels were observed between F and C. Muscle glycogen utilization was greater (P less than 0.05) during G (55.4 +/- 3.3 mmol X kg-1 w.w.) than C (42.8 +/- 4.2). No difference was observed between F (45.6 +/- 4.3) and C. There was a trend (P = 0.07) for muscle glycogen usage to be lower during F than G. These results suggest that the adverse effects of preexercise glucose ingestion are, in general, not observed with either fructose or sweet placebo.     

Exogenous carbohydrate spares muscle glycogen in men and women during 10 h of exercise

PURPOSE: The purpose of the study was to evaluate the effects of carbohydrate (CHO) supplementation on whole-body and net muscle substrate use during 10 h of discontinuous exercise, simulating occupational settings in men and women. METHODOLOGY: Recreationally trained subjects (N = 7 males, N = 6 females) performed a graded exercise test on a treadmill (TM) and cycle ergometer (CE) to determine ventilatory threshold (VT) and V O2peak. In a double-blind, randomized crossover design, subjects received either CHO [20% maltodextrin (0.6 g.kg FFM.h)] or flavored placebo (PLA) drink each hour across 10 h of exercise. Exercise intensity was 71.3 +/- 3% and 72.4 +/- 4% VT for TM and CE, respectively. Hourly exercise included 9 min of upper-body ergometery, 19 min of cycling, and 20 min of treadmill walking, with a 1-min transition between modes, followed by a 10-min rest and feeding period. The protocol was selected to simulate arduous occupational settings. Vastus lateralis biopsies were obtained before and after exercise. Expired gases were collected every other hour to establish average rates of whole-body CHO and fat oxidation. Blood glucose (BG) was measured continuously. RESULTS: Whole-body CHO oxidation was maintained during CHO trial compared with the PLA trial. Net muscle glycogen use was 52% higher for the PLA trial (176.0 +/- 16.7, 117.0 +/- 20.9 and 164.5 +/- 11.0, 133.8 +/- 10.9 mmol.kg w.w. for PLA and CHO, respectively, P < 0.05). There were no significant sex-specific differences in glycogen use, whole-body substrate oxidation, or BG values. CONCLUSION: The ingestion of CHO during long-duration exercise decreases net muscle glycogen use while better maintaining whole-body carbohydrate oxidation, and potentially increasing performance in field settings. There are limited differences in sex-specific substrate oxidation.     

Effects of exercise mode on muscle glycogen restorage during repeated days of exercise

The purpose of this study was to examine differences in muscle glycogen storage during three successive days of running or cycling. In a crossover design, seven male subjects performed two 3-d trials of either running (trial R) or cycling (trial C) for 60 min at 75% VO2max. Biopsy samples were obtained before and after each day's exercise from the gastrocnemius (trial R) or vastus lateralis (trial C) muscle. Diets in the 2 d preceding and during each trial contained 5 g carbohydrate.kg-1.d-1 and 14,475 +/- 402 kJ.d-1. Mean pre-exercise glycogen content (mmol.kg-1 wet wt.) was significantly reduced in both trials on day 3 (103.4 +/- 6.0) when compared to day 1 and day 2 (119.9 +/- 6.8 and 116.4 +/- 5.7, respectively). Day 1 glycogen reduction was significantly greater in trial C (P less than 0.03), and glycogen restorage was greater (P less than 0.02) only in trial C between the 1st and 2nd d. On day 3, spectrophotometric analysis of PAS strains showed that pre-exercise glycogen content in either muscle group was significantly (P less than 0.01) less in Type I as compared to Type II fibers. This difference in fiber glycogen storage did not appear to be attributable to muscle damage as negligible leukocyte infiltration and low blood CK levels were obtained. No difference between modes were observed for CK values throughout the trials. These data suggest that the depressed glycogen storage before the 3rd d of exercise was due to the moderate carbohydrate intake.     

Effectiveness of carbohydrate feeding in delaying fatigue during prolonged exercise

Prolonged exercise in the fasted state frequently results in a lowering of blood glucose concentration, and when the intensity is moderate (i.e. 60-80% of VO2 max), muscle often becomes depleted of glycogen. The extent to which carbohydrate feedings contribute to energy production, and their effectiveness for improving endurance during prolonged exercise, are reviewed in this article. Prolonged exercise (i.e. greater than 2 hours) results in a failure of hepatic glucose output to keep pace with muscle glucose uptake. As a result, blood glucose concentration frequently declines below 2.5 mmol/L. Despite this hypoglycaemia, fewer than 25% of subjects display symptoms suggestive of central nervous system dysfunction. Since fatigue rarely results from hypoglycaemia alone, the effectiveness of carbohydrate feeding should be judged by its potential for muscle glycogen sparing. Carbohydrate feeding during moderate intensity exercise postpones the development of fatigue by approximately 15 to 30 minutes, yet it does not prevent fatigue. This observation agrees with data suggesting that carbohydrate supplementation reduces muscle glycogen depletion. It is not certain whether carbohydrate feeding increases muscle glucose uptake throughout moderate exercise or if glucose uptake is higher only during the latter stages of exercise. In contrast to moderate intensity exercise, carbohydrate feeding during low intensity exercise (i.e. less than 45% of VO2 max) results in hyperinsulinaemia. Consequently, muscle glucose uptake and total carbohydrate oxidation are increased by approximately the same amount. The amount of ingested glucose which is oxidised is greater than the increase in total carbohydrate oxidation and therefore endogenous carbohydrate is spared. The majority of sparing appears to occur in the liver, which is reasonable since muscle glycogen is not utilised to a large extent during mild exercise. Although carbohydrate feedings prevent hypoglycaemia and are readily used for energy during mild exercise, there is little data indicating that feedings improve endurance during low intensity exercise. When the reliance on carbohydrate for fuel is greater, as during moderate intensity exercise, carbohydrate feedings delay fatigue by apparently slowing the depletion of muscle glycogen.     

Effect of hypoxia on heart glycogen utilization during exercise

An investigation was made into the effects of physical exercise upon heart glycogen change in rats exposed to decreased barometric pressure in hypobaric chamber simulating the effects of 3,000 m and 5,000 m altitude. Blood and cardiac tissue samples were examined after 1 h and 5 h of treadmill running at sea level and at 3,000 m, and after 1 h at 5,000 m. At sea level, cardiac glycogen level showed a classic biphasic evolution which was not affected by running. At 3,000 m, 1 h of running promoted an initial increase of 16% from control values, while a secondary decrease of 15% was measured after 5 h of running. Running for 1 h at 5,000 m induced a total depletion in cardiac glycogen level, the latter being depressed by 90% from control values. Free fatty acid (FFA) plasma level was increased by physical exercise at all barometric pressures, but the response was gradually enhanced by hypoxia. These data indicate that heart glycogen utilization during prolonged physical exercise is stimulated by acute altitude exposure, which suppresses the sparing effect observed at sea level upon dependence of enhanced FFA availability. The great differences in cardiac glycogen utilization support the views that enhanced glycogenolysis during hypoxia is promoted by different parameters, thus affecting various pathways. The slight decrease at 3,000 m suggests a moderate increase in anaerobic metabolism while the exhaustion observed after 1 h of running at 5,000 m indicates a decrease in cellular respiration response and enhanced heart anaerobic metabolism.     

Glycaemic control, muscle glycogen and exercise performance in IDDM athletes on diets of varying carbohydrate content.

The aim of this study was to examine the effects of a high carbohydrate diet on glycaemic control, resting muscle glycogen levels and exercise performance in athletes with insulin dependent diabetes (IDDM). Seven trained (mean +/- S.D., VO2max 50.3 +/- 7.4 ml/kg/min) IDDM males consumed a high carbohydrate diet (HCD) or a normal mixed diet (NMD) for 3 week periods in a randomised crossover trial with a one week wash-out. Carbohydrate provided 59% or 50% of total energy intake, respectively, on the two diets. Fasting plasma lipids, mean blood glucose (over 96 h), fructosamine and muscle glycogen were measured and insulin use recorded. Exercise performance was evaluated by a 15 min time trial following a 50 min pre-loading block. Statistical significance was assessed using two tailed paired Student t-tests. Mean blood glucose was 10% higher on HCD than NMD (p = 0.005), fructosamine levels were 375 +/- 54 and 353 +/- 51 (mol/L on HCD and NMD, resp., p = 0.04) and daily insulin requirements were 15% higher on HCD than NMD (p = 0.02). Fasting blood lipids were similar on the two diets. Muscle glycogen was significantly lower on HCD than NMD (88.2 +/- 19.2 and 95.6 +/- 14.6 mmol/kg ww, respectively, p = 0.02). Exercise completed during the time trial was 6% less on HCD than on NMD (p = 0.007). An increased carbohydrate intake for three weeks, in IDDM athletes, is associated with a deterioration in glycaemic control, increased insulin requirements, decreased muscle glycogen and reduced exercise performance. These data do not support recommendations for IDDM athletes to consume a high carbohydrate diet, at least not when glycaemic control worsens upon following this advice, as was observed in this short-term study.     

Effect of carbohydrate on portal vein blood flow during exercise

Effects of carbohydrate ingestion and exercise on portal vein blood flow were studied. Flow was measured by pulsed-electronic Doppler. Eight male subjects performed four tests after a standardised breakfast and 5 h fast. Beverages were CHO (10 % glucose, 30 mmol . l (-1) NaCl) and W (water, 30 mmol . l (-1) NaCl). Exercise experiments comprised a resting measurement, 10 min warm-up and 60 min 70 % VO(2)max cycling. Every 10 min subjects stopped cycling briefly (approximately 30 s) for measurements. Beverage was consumed after warm-up (500 ml) and at 20 and 40 min (250 ml). Similar tests were done at rest. Blood samples were taken concurrently with flow measurements for hormonal concentrations. Exercise decreased blood flow (repeated measures ANOVA, p < 0.0001) and carbohydrate ingestion increased flow (p = 0.015). At rest, flow was greater with CHO than with W at 20 (177 +/- 31; 101 +/- 25 %, resp.) (mean +/- SE), 30 (209 +/- 37; 120 +/- 20 %), 40 (188 +/- 32; 108 +/- 12 %), and 60 min (195 +/- 19; 112 +/- 12 %) (1-way ANOVA, Fisher's PLSD, p < 0.05). Flow was similar during exercise with CHO and W, with a tendency for CHO to maintain flow better, at 10 (124 +/- 27; 77 +/- 21 %), 20 (81 +/- 10; 60 +/- 13 %), 30 (106 +/- 26; 56 +/- 10 %), 40 (109 +/- 28; 54 +/- 8 %), 50 (85 +/- 17; 54 +/- 13 %), and 60 min (61 +/- 15; 47 +/- 7 %). A positive correlation between glucagon and flow and an inverse correlation between noradrenaline and flow were observed. Exercise reduces, and carbohydrate increases, portal vein flow. Changes in plasma concentrations suggest that noradrenaline and glucagon, respectively, may play a role in modulating flow.     

Recovery of muscle glycogen concentrations in sled dogs during prolonged exercise

PURPOSE: To determine the depletion of muscle glycogen during five consecutive days of endurance exercise in Alaskan sled dogs consuming a high-fat, low-carbohydrate diet. METHODS: Forty-two fit Alaskan sled dogs were used in the study, of which six dogs served as nonexercising control animals. The remaining 36 dogs ran 160 km x d(-1) for up to 5 d while consuming a diet providing approximately 50% of calories as fat and 15% as carbohydrate. Muscle biopsies were performed on six randomly selected dogs before feeding and within 4 h after each 160-km run was completed. Muscle samples were prepared for analysis of glycogen content and myosin ATPase staining. Serum creatine kinase (CK) activity was measured once before exercise and after each 160-km run. RESULTS: Thirty-three of 36 dogs completed the runs. Muscle glycogen concentration was highest in sedentary dogs (340 +/- 102 mmol x kg(-1) dry weight), declined to 73 +/- 16 after 160 km and subsequently increased to similar levels between 320 and 800 km (320 km: 177 +/- 34; 800 km: 213 +/- 44). Postexercise serum CK activity was significantly elevated throughout the study. CONCLUSION: Skeletal muscle in Alaskan sled dogs has remarkable glyconeogenic ability as demonstrated by repletion to greater than 50% of resting muscle glycogen concentrations after the second of five consecutive 160-km runs even when fed a low-carbohydrate, high-fat diet. Whether this finding is attributable to rapid repletion of muscle glycogen during brief recovery periods versus progressive utilization of alternative substrates remains to be investigated.     

Novel aspects of skeletal muscle glycogen and its regulation during rest and exercise

Although it is often viewed as a homogenous substrate, glycogen is comprised of individual granules or 'glycosomes' that vary in their composition, subcellular localization, and metabolism. These differences result in additional levels of regulation allowing granules to be regulated individually or regionally within the cell during both rest and exercise.     

Effects of caffeine, fructose, and glucose ingestion on muscle glycogen utilization during exercise

Five competitive cyclists were used to determine the effects of fluid intake (16 ml.kg-1) consisting of: (i) non-nutrient control (CON); (ii) fructose (1 g.kg-1) before exercise (FRU); (iii) caffeine (5 mg.kg-1) before exercise (CAF); (iv) glucose (1 g.kg-1) during exercise (GLU); and (v) fructose/caffeine before and glucose during exercise (CFG) on blood glucose, free fatty acids, muscle glycogen, and other parameters. Exercise consisted of 90 min of cycling at 65 to 70% VO2max. Following exercise, blood glucose was found to be significantly (P less than 0.05) higher for CFG and GLU (117 and 109 mg%) compared to CON, CAF, and FRU (92, 89, and 86 mg%). Blood free fatty acids rose (P less than 0.05) further for CON (1,336), CAF (1,126), and FRU (1,034) over CFG (737) and GLU (714 mumol.l-1). Muscle glycogen utilization was greater (P less than 0.05) for CON (91) vs CAF (63) and GLU (62 mumol/g-1 wet muscle weight). It was concluded that GLU and CAF decrease muscle glycogen utilization, FRU is likely to cause gastric upset, and ingestion of multiple substances produces the greatest variability in muscle glycogen utilization and may provide added endurance benefits in some individuals.     

Effect of carbohydrate and vitamin B6 on fuel substrates during exercise in women

Pyridoxal 5'-phosphate is an essential co-factor for glycogen phosphorylase and certain enzymes in the alanine-glucose cycle. Glycogen phosphorylase is also proposed as a storage reservoir for vitamin B6. To examine the effect of vitamin B6 and carbohydrate on fuel substrates during exercise, 5 young/trained, 5 young/un-trained, and 5 post-menopausal/un-trained women were alternately fed four diets (varying carbohydrate and B6 level) over a 7-wk period. Subjects were exercised at the end of each dietary period at 80% VO2max for 20 min on a cycle ergometer. Blood was drawn pre-, post-, post-30, and post-60 min of exercise and analyzed for plasma pyridoxal 5'-phosphate, glucose, free fatty acid, and lactate. ANOVA showed no difference among groups or diets for lactate, although lactate was significantly different over time (P less than 0.0001) on all diets. ANOVA showed significant time x group x diet inter-actions for free fatty acid (P less than 0.05) and significant diet x time (P less than 0.04) and time x group (P less than 0.03) inter-actions for glucose. Supplementation and/or increased carbohydrate resulted in lower free fatty acid during exercise in all groups. ANOVA showed no difference in pyridoxal 5'-phosphate for groups with respect to diet or time, but did show a significant increase from pre- to post-exercise and a significant decrease from post- to post-60 min of exercise. These results indicate that a high-carbohydrate diet and/or supplemental vitamin B6 can alter plasma fuel substrates during exercise in women; however, the effect depends on age and level of training.     

Effect of a high carbohydrate diet on core temperature during prolonged exercise.

This study compared the effects of a high-carbohydrate and a mixed diet on core temperature responses to prolonged exercise in six male competitive cyclists (age = 22.2 +/- 1.9 years). This study, the first to investigate the effect of a high-carbohydrate diet on exercise core temperature in humans, therefore suggests that three days of increased dietary carbohydrate intakes do not evoke any deleterious thermoregulatory responses during prolonged submaximal exercise.     

Effect of glycerol feeding on endurance and metabolism during prolonged exercise in man

This study evaluated the effectiveness of pre-exercise glycerol feeding in protecting against development of hypoglycemia and sparing muscle glycogen during prolonged, intense exercise. Thirty minutes after ingesting either glycerol (1 gm X kg-1 body weight) or a placebo, 10 cyclists performed as much exercise on a cycle ergometer as they were able in 150 min. The average exercise intensity was 72% of VO2max during both trials. Glycerol ingestion increased blood glycerol concentration 100-fold, but did not alter the respiratory exchange ratio (R), plasma levels of insulin and free-fatty acids, or blood lactate and beta-hydroxybutyrate. The only significant effect of glycerol feeding was to postpone the decline in blood glucose by about 30 min. This suggests that glycerol served, to a limited extent, as a gluconeogenic substrate; however, glycerol ingestion did not spare muscle glycogen during 90 min of treadmill exercise at 71% VO2max. It appears that man cannot utilize glycerol as gluconeogenic substrate rapidly enough to serve as a major energy source during strenuous exercise.     

A signalling role for muscle glycogen in the regulation of pace during prolonged exercise

Introduction: In this study we examined the pacing strategy and the end muscle glycogen contents in eight cyclists, once when they were carbohydrate loaded and once when they were non-loaded.

Methods: Cyclists completed 2 hours of cycling at ~73% of maximum oxygen consumption, which included five sprints at 100% of peak sustained power output every 20 minutes, followed immediately by a 1 hour time trial. Muscle biopsies were performed before and immediately after exercise, while blood samples were taken during the 2 hour steady state rides and immediately after exercise.

Results: Carbohydrate loading improved mean power output during the 1 hour time trial (mean (SEM) 219 (17) v 233 (15) W; p<0.05) and enabled subjects to use significantly more muscle glycogen than during the trial following their normal diet. Significantly, the subjects, kept blind to all feedback except for time, started both time trials at similar workloads (~30 W), but after 1 minute of cycling, the workload average 14 W higher throughout the loaded compared with the non-loaded time trial. There were no differences in subjects' plasma glucose and lactate concentrations and heart rates in the carbohydrate loaded versus the non-loaded trial. Of the eight subjects, seven improved their time trial performance after carbohydrate loading. Finishing muscle glycogen concentrations in these seven subjects were remarkably similar in both trials (18 (3) v 20 (3) mmol/kg w/w), despite significantly different starting values and time trial performances (36.55 (1.47) v 38.14 (1.27) km/h; p<0.05). The intra-subject coefficient of variation (CV) for end glycogen content in these seven subjects was 10%, compared with an inter-subject CV of 43%.

Conclusions: As seven subjects completed the time trials with the same end exercise muscle glycogen concentrations, diet induced changes in pacing strategies during the time trials in these subjects may have resulted from integrated feedback from the periphery, perhaps from glycogen content in exercising muscles.

     

Effect of muscle oxygenation during resistance exercise on anabolic hormone response

PURPOSE: The mechanisms that underlie the affect of acute program variables on muscle growth and strength development for strength/power athletes have been of great interest. This investigation examined the affects of two different resistance exercise protocols on muscle oxygenation, and the anabolic hormonal response to such exercise. METHODS: Eleven experienced resistance-trained male athletes performed four sets of the squat exercise using either a low-intensity, high-volume (LI; 15 repetitions at 60% one-repetition maximum [1-RM]) or high-intensity, low-volume (HI; 4 repetitions at 90% 1-RM) load. Venous blood samples were obtained before (Pre), immediate (IP), 20- (20P), and 40-min (40P) postexercise. Continuous-wave near-infrared spectroscopy was used to measure oxygen desaturation during exercise. RESULTS: No differences in muscle deoxygenation were seen between LI and HI. However, time-dependent postexercise reoxygenation was significantly different between the two exercise sessions (35.3 +/- 17.4 s vs 24.5 +/- 14.3 s in LI and HI, respectively). Testosterone and growth hormone (GH) concentrations were significantly elevated from Pre at IP, 20P, and 40P in both LI and HI. GH concentrations were higher (P<0.05) for LI than at HI at 20P and 40P. CONCLUSION: Muscle oxygen recovery kinetics appeared to be influenced by differences in the intensity and volume of exercise, and delayed reoxygenation appears to affect the GH response to exercise.     

Effect of carbohydrate and prolonged exercise on affect and perceived exertion

INTRODUCTION: It has been reported that perceptions of exertion are attenuated during prolonged cycle exercise, following CHO ingestion. However, no studies to date have examined the influence of such feedings on psychological affect during prolonged exercise, even though affect and perceived exertion are different constructs. PURPOSE: To examine the influence of regular CHO beverage ingestion on affect (pleasure-displeasure) and perceived exertion during prolonged cycle exercise. METHODS: In a randomized, double-blind, counterbalanced design, nine endurance trained males cycled for 2 h at 70% VO2max on two occasions, separated by 1 wk. On each occasion, they consumed either a water placebo (PLA) or a 6.4% carbohydrate-electrolyte solution (CHO) immediately before they cycled (5 mL x kg(-1) body mass) and every 15 min thereafter (2 mL x kg(-1) body mass). Pleasure-displeasure was assessed before, during, and after the prolonged bout of cycling. RESULTS: During exercise, reported pleasure initially improved and was subsequently maintained in the CHO trial, in contrast to a decline reported in the PLA trial. Ratings of pleasure-displeasure were more positive during recovery in the CHO trial compared with the PLA trial (P < 0.05) and the only significant increase (P < 0.05) in pleasure occurred 15 min postexercise in the CHO trial only. RPE increased (P < 0.05) over the course of the bout of cycling and was lower (P < 0.05) 75 min into exercise in the CHO trial. Immediately postexercise, plasma glucose concentration was higher in the CHO compared with the PLA trial (P < 0.05). A main effect of trial was found for plasma cortisol concentration, with higher values reported in PLA trial. CONCLUSION: Results suggest that CHO ingestion enhanced feelings of pleasure during and following prolonged cycling and highlighted the importance of assessing not only "what," but also "how" a person feels.