Carbohydrate Electrolyte Research Articles

Caffeine improves cognitive performance after strenuous physical exercise.

The effects of three carbohydrate electrolyte solutions (CES) containing different amounts of caffeine on cognitive function and the combined effects of these drinks and exercise on cognitive functions were investigated in a double-blind, cross-over study. On five separate occasions, fifteen endurance trained male athletes (23.3 years) received water placebo, CES placebo (68.8 g/l), and three CES drinks containing low, medium and high dosages of caffeine (150, 225 and 320 mg/l). Each occasion, 8 ml/kg of the drink was consumed before -- and 6 ml/kg of the drink was consumed during an all-out 1 hour time trial on a bicycle ergometer. Cognitive (attentional, psychomotor, and memory) tests were carried out immediately before and immediately after exercise. Before exercise, long term memory was improved by CES plus low dose caffeine compared to both placebos. Immediately after exercise, all cognitive functions were improved by CES plus low- and medium-dose caffeine compared to placebo. These results comprise the first practical demonstration of the cognition improving effects of low amounts of caffeine in CES after strenuous physical exercise.

WATER AND ELECTROLYTE REQUIREMENTS FOR EXERCISE

Exercise performance can be compromised by a body water deficit, particularly when exercise is performed in hot climates. It is recommended that individuals begin exercise when adequately hydrated. This can be facilitated by drinking 400 mL to 600 mL of fluid 2 hours before beginning exercise and drinking sufficient fluid during exercise to prevent dehydration from exceeding 2% body weight. A practical recommendation is to drink small amounts of fluid (150-300 mL) every 15 to 20 minutes of exercise, varying the volume depending on sweating rate. Core temperature, heart rate, and perceived effort remain lowest when fluid replacement comes closest to matching the rate of sweat loss. During exercise lasting less than 90 minutes, water alone is sufficient for fluid replacement. During prolonged exercise lasting longer than 90 minutes, commercially available carbohydrate electrolyte beverages should be considered to provide an exogenous carbohydrate source to sustain carbohydrate oxidation and endurance performance. Electrolyte supplementation is generally not necessary because dietary intake is adequate to offset electrolytes lost in sweat and urine; however, during initial days of hot-weather training or when meals are not calorically adequate, supplemental salt intake may be indicated to sustain sodium balance.

Effect of a carbohydrate-electrolyte drink on endurance capacity during prolonged intermittent high intensity running.

OBJECTIVE: To examine the effect of a carbohydrate-electrolyte solution on endurance capacity during prolonged intermittent running. METHODS: Nine subjects (eight men and one woman) ran to exhaustion on a motorised...

Effect of medium-chain triacylglycerol and carbohydrate ingestion during exercise on substrate utilization and subsequent cycling performance

The aim of this study was to investigate the effect of medium-chain triacylglycerol (MCT) ingestion during exercise on subsequent time-trial cycling performance. Seven well-trained cyclists performed four exercise trials consisting of 2 h at 60% of maximal oxygen uptake followed by a simulated time trial (ie, completion of a preset amount of work as fast as possible) of approximately 15 min duration. During the trials, subjects ingested 1) a 10% carbohydrate solution (CHO; 170 +/- 6 g glucose), 2) a 10% carbohydrate electrolyte with 5% MCT solution (CHO + MCT; 85 +/- 3 g MCT), 3) a 5% MCT solution, or 4) artificially colored and flavored water (placebo). Neither CHO nor CHO + MCT ingestion had any effect on performance compared with placebo ingestion, whereas ingestion of MCT had a negative effect on performance. Average work rates during the time trial were 314 +/- 19, 314 +/- 13, and 312 +/- 18 with CHO, CHO + MCT, and placebo, respectively, and was 17-18% lower in the MCT trial (263 +/- 22 W). In addition, compared with placebo ingestion, MCT ingestion had no effect on total rates of fat or carbohydrate oxidation, nor did it affect exogenous or endogenous carbohydrate utilization. The negative effect of MCT ingestion was associated with increased gastrointestinal complaints (ie, intestinal cramping). These data suggest that large amounts of MCTs (85 g) ingested during prolonged submaximal exercise may provoke gastrointestinal problems leading to decreased exercise performance.

The physiological effects of beverage ingestion during cross country ski training in elite collegiate skiers.

The purpose of this study was to investigate the effects of beverage ingestion on fluid balance during 1.5 hr of low intensity cross country skiing. In Part I, 6 skiers drank water ad libitum during ski training. In Part II, 10 skiers were matched by body weight (BW) and assigned to ingest 2.5 ml.kg-1 BW of water or a carbohydrate/electrolyte (CE) beverage every 2.5 km. Skiing speed averaged 11.5 km.hr-1 for 90 min around a 5 km groomed track. Following 20 min of seated rest, blood samples were collected immediately before and approximately 30 min after skiing. Part I data indicated that subjects ingested 576 +/- 189 ml of fluid and produced 266 +/- 205 ml of urine; BW, plasma and urine osmolality, and plasma protein decreased significantly. In Part II, the CE group produced less urine (135u75 vs. 450 +/- 262 ml) and had smaller decreases in plasma osmolality (-1.0 +/- 1.0 vs. -7.0 +/- 2.4 mOsm.kg H2O) and protein (-0.11 +/- 08 vs. -0.42 +/- 0.24 gL-1) than the water group. No differences were observed for BW loss, % change in PV, FWC, or change in urine osmolality. It was concluded that ad lib water ingestion was inadequate to minimize fluid balance disruption. Plain water ingestion also led to significant dilution of the plasma and increased urine output. However, the ingestion of CE led to attenuation of fluid balance disruption, presumably due to the maintenance of osmotic balance in the plasma.

The effects of beverage carbonation on sensory responses and voluntary fluid intake following exercise.

The effects of carbonated beverages on sensory acceptability and voluntary fluid intake after exercise were examined. The level of carbonation in a 6% carbohydrate (CHO) electrolyte drink was systematically varied (0, 1.1, 2.3, and 3.0 volumes of CO2), and its impact was assessed in 52 adults following 30 min of exercise. The perception of carbonation intensity closely tracked the differences in physical carbonation levels presented, with all perceived intensities significantly different from each other (p < .01). Overall sensory acceptability, perceived thirst quenching, and perceived sweetness were significantly lower for 2.3-vol CO2 and 3.0-vol CO2 than for 0-vol CO2 and 1.1-vol CO2 (p < .01). Perceived throatburn was significantly higher for 2.3-vol CO2 and 3.0-vol CO2 than for 0-vol CO2 and 1.1-vol CO2 (p < .01). Total fluid intake for 0-vol CO2 and 1.1-vol CO2 was significantly higher than for 2.3-vol CO2 (p < .05), which was significantly higher than for 3.0-vol CO2 (p < .05). It was concluded that levels of carbonation equal to or in excess of 2.3-vol CO2 negatively impact drink acceptability and voluntary fluid intake.

Acute Effects of Exercise or Sauna on Appetite in Obese and Nonobese Men

Westerterp-Plantenga, M. S., C. R. T. Verwegen, M. J. W. IJedema, N. E. G. Wijckmans And W. H. M. Saris. Acute effects of exercise or sauna on appetite in obese and nonobese men. PHYSIOL BEHAV 62(6) 1345–1354, 1997.—To study the effect of exercise on appetite in men, hunger, thirst, taste perception, energy intake, and macronutrient choice were assessed in relation to exercise and to sauna; the latter was done to correct for dehydration and rise in body temperature. Since exercise is used to prevent and cure obesity, subjects included obese as well as nonobese men. Thirty subjects (25 ± 7 years, BMI 22.8 ± 1.6 and 28.5 ± 1.9) were given twice, in random order before and after 2 h of cycling at 60% of W max, 2 h of sauna, or 2 h of rest, an ample choice from solid and liquid almost single-macronutrient food items and a taste perception test with solutions of sucrose, citric acid, NaCl, quinine, a mixture of these, and a carbohydrate electrolyte solution. After cycling as well as after sauna, in comparison to after rest, subjects lost 3 ± 0.5% of body mass, while thirst, fluid intake, perception of sweet at relatively low concentrations, and percentage of energy coming from carbohydrate increased significantly. Only after cycling compared to after rest did perception of bitterness at a low concentration increase and hunger and energy intake decrease. We conclude that exercise induced a short-term reduction in hunger and energy intake, whereas exercise and sauna induced a short-term increase in taste perception of sweet at the lower concentration, while macronutrient preference of carbohydrate increased.

EFFECTS OF CARBOHYDRATE INGESTION ON SOCCER SPECIFIC SKILL TESTS PERFORMED IN THE HEAT 721

The effects of carbohydrate ingestion on the performance of soccer specific skills during a simulated match undertaken in hot humid conditions was evaluated. Subjects were six internationally competitive junior soccer players from the Australian Institute of Sport Soccer Team (16.8±0.5 yr; 75.8±7.1 kg; VO2peak = 56±3 ml·kg-1.min-1, mean ± SD). Subjects were familiarised with a battery of soccer-specific skill tests including a 20m sprint, ball dribbling, goal shooting, and 3 Acuvision™ tests which measured pro-action/reaction (PRO/REAC), visual concentration, and reaction time. Each subject completed 2 trials separated by one week during which these tests were performed before, during and after a 60-min treadmill protocol(=9.5 km) in hot humid conditions (32°C, 60% r.h.). The treadmill protocol was designed to simulate the typical exercise requirements of a soccer match, and consisted of exercise of varying intensities (5-19 km hr-1), with a change in running velocity each 15 sec. During each trial subjects consumed 1.6 L of either a carbohydrate-electrolyte (CHO) or an artificially sweetened electrolyte (PLACEBO) drink tested in a randomised counterbalanced order. Mean total sweat loss (=2.8 L) did not differ between trials. Blood glucose concentrations were significantly higher following the CHO trial (P= 0.03), although mean glucose concentrations remained above pre-exercise levels during the placebo trial. All subjects reported that they felt and performed better during the CHO trial. Despite a perception of fatigue following the treadmill run, there were no significant decrements in soccer specific performance tests with either trial with the exception of PRO/REAC scores which were significantly lower on the PLACEBO trial (50.5±4.0 v 52.2±3.2; P = 0.04). Additional research is required to understand the effects of CHO on soccer performance in hot humid conditions.

Water versus carbohydrate-electrolyte ingestion before and during a 15-km run in the heat.

Twelve highly trained male runners ran 15 km at self-selected pace on a treadmill in warm conditions to demonstrate differences in physiological responses, fluid preferences, and performance when ingesting sports drinks or plain water before and during exercise. One hour prior to the start of running, an equal volume (1,000 ml) of either water or a 6% or an 8% carbohydrate-electrolyte (CE) drink was ingested. Blood glucose was significantly higher 30 min following ingestion of 6% and 8% CE compared to water, significantly lower at 60 min postingestion with both sports drinks than with water, but similar after 7.5 km of the run for all beverages. During the first 13.4 km, oxygen uptake and run times were not different between trials; however, the final 1.6-km performance run was faster with both CE drinks compared to water. Despite a lower preexercise blood glucose, CE consumption prior to and during exercise significantly improved performance in last 1.6 km of a 15-km run compared to water.

RUNNING PERFORMANCE IN HOT, HUMID CONDITIONS: EFFECT OF BEVERAGE CARBOHYDRATE CONTENT 1197

In an attempt to determine the influence of beverage carbohydrate content on running performance during prolonged exercise in the heat, 10 well-trained male runners were studied. The mean age, height, weight, VO2max, and% body fat were 37.2±3.1 yrs, 177.2±2.1 cm, 73.5±2.6 kg, 61.2±2.6 ml·kg1·min-1, and 12.2%, respectively. Subjects completed four 15 mile treadmill runs in an environmental chamber maintained at 80°C and 70%RH. The first 12 miles of each run was paced at 70% VO2max, and the final 3 miles was considered a time-trial. For all runs, subjects consumed 400 ml of a designated carbohydrate electrolyte (CE) beverage prior to running, and 200 cc at 3 mile intervals. The first run was considered a familiarization trial, and subsequent trials were randomized and counterbalanced such that subjects consumed one of three CE drinks (6%, 8%, and 10% C, with 5% HFCS and balance as maltodextrin, with 10mM Na+, 3.3 mM K+, and 5.4 mM CL-). Mean 3 mile run time was 41.3 seconds (3.5%) faster on 6% CE vs. 10% CE and 37.8 seconds (3.2%) faster on 8% CE vs. 10% CE (p=0.09 for both). Analysis of 0.5 mile split times demonstrated that the final split was run 14 seconds (7%) faster on 6% CE vs. 10% CE and 9.4 seconds (4.7%) faster on 8% CE vs. 10% CE (p=0.06). Taken together, these results suggests that consumption of a 10% CE beverage may impair performance relative to CE beverages with lower carbohydrate content.

The Influence of Ingesting a Carbohydrate-Electrolyte Beverage during 4 Hours of Recovery on Subsequent Endurance Capacity

Recovery from prolonged exercise involves both rehydration and replenishment of endogenous carbohydrate stores. The present study examined the influence of ingesting a carbohydrate-electrolyte (CE) solution following prolonged running, on exercise capacity 4 hr later. Twelve men and 4 women were divided into two matched groups, which were randomly assigned to either a control (P) or a carbohydrate (CHO) condition. Both groups ran at 70% of maximal oxygen uptake (VO2max) on a level treadmill for 90 min or until volitional fatigue (R1), and they ran at the same % VO2max to exhaustion 4 hr later to assess endurance capacity (R2). The CHO group ingested a 6.9% CE solution providing 1.0 g CHO.kg body weight-1 immediately post-R1 and again 2 hr later. The P group ingested equal volumes of a placebo solution. Run times (mean +/- SEM) for R1 did not differ between the groups (P 86.3 +/- 3.8 min; CHO 87.5 +/- 2.5 min). The CHO group ran 22.2 (+/- 3.5) min longer than the P group during R2 (P 39.8 +/- 6.1 min; CHO 62.0 +/- 6.2 min) (p < .05). Thus, ingesting a 6.9% carbohydrate-electrolyte beverage following prolonged, constant-pace running improves endurance capacity 4 hr later.

A comparison of a carbohydrate–electrolyte beverage versus a placebo beverage in maintaining thermoregulatory and blood homeostasis during the training of fire fighters

The efficacy of ingesting carbohydrate–electrolyte (GP) beverages during intermittent and protracted aerobic exercise has been clearly demonstrated. Therefore, the present investigation focused on the practical application of ingesting GP beverages during intermittent fire fighting. This investigation included the determination of the efficacy of a carbohydrate–electrolyte beverage in maintaining blood and temperature homeostasis during fire-fighter training. Healthy fire fighters ( n =7, age 31.5–37.5 years) volunteered for participation. Subjects completed two field tests in which they consumed either 473 ml of a placebo (P = non-nutrient beverage) or GP beverage (7% glucose polymers) at baseline and every 30 min during a 120-min fire-fighting training session. The experimental design was double blind. Venous blood samples were drawn pretest, midtest, and posttest and analyzed for [hematocrit], [glucose], [Na + ], [K + ], cortisol, and osmolality. Heart rate (HR) was determined via a holter monitor. Rating of perceived exertion (RPE) via the Borg 15-point scale and oral temperature were also measured. Analysis of variance revealed no significant differences across time or between beverages in maintaining blood electrolyte or temperature homeostasis. Cortisol, RPE, and HR increased ( p

Fluid intake in male and female runners during a 40‐km field run in the heat

To compare physiological responses, hydration status and exercise performance in similarly trained men and women in a hot, humid environment, 12 highly trained runners were studied during a simulated 40-km race. A 7% carbohydrate-electrolyte (CE) beverage was consumed prior to exercise (400 ml) and every 5 km (approximately 250 ml) during the run. The run times of the males and females did not differ significantly (173.5 +/- 8.5 and 183.8 +/- 4.2 min, respectively); nor did the rate of fluid intake relative to body mass (10.3 +/- 0.7 and 10.7 +/- 0.8 ml kg-1 h-1, respectively) or percent body mass loss (4.0 +/- 0.1% and 3.9 +/- 0.1%, respectively). During the run, %VO2 max, heart rate, concentrations of blood lactate, serum total protein and plasma osmolality were also similar for both groups. However, some significant sex differences (P < 0.05) were observed: the females had lower plasma volume losses and higher serum potassium and sodium concentrations than the males during the run. Rectal temperatures were lower in the female runners compared with the males during the last 10 km of the run (0.7 degrees C) and recovery (1.1 degrees C). Findings from this 40-km field run in hot, humid conditions suggest that CE fluid replacement at a relatively similar dosage (approximately 10 ml kg-1 h-1) may have sex-specific physiological effects. These observations warrant further investigation to assess the need for sex-specific fluid replacement guidelines.

Influence of carbohydrate-electrolyte drinks on marathon running performance

The aim of this study was to compare the effects of drinking two carbohydrate (CHO) electrolyte solutions and water on marathon running performance. Seven endurance-trained runners completed three 42.2-km treadmill time-trials which were randomly assigned and 4 weeks apart. On each occasion the subjects ingested 3 ml.Kg-1 body weight of either water (W), a 6.9% CHO solution (O) or a 5.5% CHO solution (L) immediately prior to the start of the run and 2 ml.kg-1 body weight every 5 km thereafter. The total volume of fluid ingested [mean (SEM)] was 1112 (42), 1116 (44) and 1100 (44) ml, respectively. Running times for W, O and L trials were 193.9 (5.0), 192.4 (3.3) and 190.0 (3.9) min, respectively. Performance time for the L trial was faster (P < 0.05) compared with that of the W trial. Running speed was maintained in the L trial, whereas it decreased after 10 km (P < 0.05) in the W and after 25 km (P < 0.05) in the O trial. Blood glucose and lactate, and hormonal responses to fluid ingestion were similar in all three trials. Higher plasma free fatty acid and glycerol concentrations were observed at the end of the W trial compared with those obtained after the O and L trials, respectively (P < 0.05). Plasma ammonia concentration was higher (P < 0.01) at the end of the L trial compared with the W trial. Plasma creatine kinase concentration was higher (P < 0.05) 24 h after the completion of the L trial than after the W trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of cycle exercise on intestinal absorption in humans

Intestinal absorption was measured in six trained male cyclists during rest, exercise, and recovery periods with the segmental perfusion technique. Each subject passed a multilumen tube into the duodenojejunum. The experiments consisted of 1) a sequence of 1-h bouts of cycling exercise at 30, 50, and 70% maximal O2 uptake (Vo2max) separated by 1-h rest periods or 2) a 90-min bout at 70% VO2max. The cycling was performed on a constant-load Velodyne trainer. Absorption of water and a 6% carbohydrate-electrolyte (2% glucose, 6% sucrose, 20 meq Na+, 2.6 meq K+) solution (both perfused at 15 ml/min) were compared. The effects of perfusing an isotonic electrolyte solution during mild (30% VO2max) exercise were also studied. Fluid was sampled every 10 min from ports 10 and 50 cm distal to the infusion site. Water flux was determined by differences in polyethylene glycol concentration across the 40-cm test segment. Results showed 1) no difference in water or electrolyte absorption rates among rest, exercise, and recovery periods; 2) no difference in absorption rates among the three exercise intensities or different exercise durations; and 3) significantly greater fluid absorption rates from the carbohydrate-electrolyte (CE) solution than from water. Water flux during rest, exercise, and recovery was about sixfold greater from the CE solution than from the isotonic solution without carbohydrate. We conclude that 1) exercise has no effect on water or solute absorption in the duodenojejunum, 2) fluid absorption occurs significantly faster from a CE solution than from water, and 3) fluid absorption is increased sixfold by addition of carbohydrate to an electrolyte solution.

Physiological effects of dehydration and rehydration with water and acidic or neutral carbohydrate electrolyte solutions

Five healthy young men exercised on an ergocycle for six 25-min periods separated by 5-min rest intervals in a warm dry environment (36 degrees C). After 1 h of exercise without fluid intake, the subjects continued to be dehydrated or were rehydrated either with water (W) or with isosmotic electrolyte carbohydrate solutions, either acidic (AISO) or close to neutrality (NISO). The average amount of the fluid ingested progressively every 10 min (120 ml) at 20 degrees C was calculated so as to compensate for 80% of the whole body water loss due to exercise in the heat. Dehydration associated with hyperosmotic hypovolaemia elicited large increases in heart rate (HR), and in rectal temperature (Tre), while no decrease was found in either whole body or local sweat rates. Rehydration with water significantly reduced the observed disturbances, except for plasma osmolality and Na+ concentration which were significantly lower than normal. With both AISO and NISO there was no plasma volume reduction and osmolality increase. Although a plasma volume expansion was induced by NISO ingestion, the cardiac cost was not improved, as reflected by the absence of a decrease in HR. With NISO, sweating was not enhanced and Tre tended to remain higher. It is concluded that efficient rehydration requires the avoidance of plasma volume expansion at the expense of interstitial and intracellular rehydration. During rehydration by oral ingestion of fluid, the pH of the drink may be an important factor; its effect remains unclear, however.

Fluid replacement during and after exercise in the heat

This study sought to determine whether ad libitum drinking of a carbohydrate-electrolyte (CE) beverage would minimize the physiological disturbances associated with prolonged (3 h) continuous exercise in the heat (Tdb = 31.5 degrees C, percent RH = 22.3). Seven male subjects performed two bouts of cycle exercise (60% VO2max) drinking either a CE beverage (4.85% polycose, 2.65% fructose) or distilled water. Subjects continued to drink ad libitum for 3 h during recovery in the heat. No significant differences were observed between drinks for rectal temperature, heart rate, or sweat rate during exercise. Subjects tended to drink more (P less than 0.0565) water than the CE beverage during exercise, but plasma volume (percent PV) decreased less (P less than 0.0253) and plasma [( glucose], P less than 0.0001 and [K+], P less than 0.0047) were higher when subjects drank the CE solution. At the end of exercise, plasma osmolality and [Na+] were also higher (P less than 0.05) when subjects drank the CE beverage rather than water. Rating of perceived exertion was higher (P less than 0.0001) when drinking water. In recovery, ingesting the CE beverage, 1) subjects drank more (P less than 0.0012); 2) plasma volume increased to a higher level (P less than 0.0017); 3) plasma osmolality (P less than 0.0001), [Na+] (P less than 0.0001), glucose (P less than 0.0001), and [K+] (P less than 0.0015) were greater; and 4) body weight increased more (P less than 0.0422) than when water was ingested. Thus, in terms of minimizing physiological disturbances, ad libitum drinking of the CE beverage was as effective as drinking water during exercise but was more effective in recovery.

Oral solutions for infantile gastroenteritis--variations in composition.

Four different carbohydrate electrolyte solutions were provided for children under 18 months with acute gastroenteritis treated as outpatients. Osmolality and sodium content were measured in samples of solutions as given by the parents. All types of feed were made up with marked inaccuracy. Osmolality was sometimes unacceptably high in solutions containing glucose, while the highest osmolality for sucrose solutions hardly exceeded the correct value for glucose solutions. Most parents could use a sachet with reasonable accuracy although there were still wide extremes of errors. The ideal preparation for use in developed countries may be a sachet containing sucrose and electrolyte, particularly if such sachets could be made generally available and not just for use in hospitals and clinics.

Availability of substrates and capacity for prolonged heavy exercise in man.

Availability of substrates and capacity for prolonged heavy exercise in man.

Carbohydrate metabolism and electrolyte changes in human muscle tissue during heavy work.

Carbohydrate metabolism and electrolyte changes in human muscle tissue during heavy work.