Carbohydrate-electrolyte Beverage Research Articles

Comparison of hydration efficacy of carbohydrate-electrolytes beverages consisting of isomaltulose and sucrose in healthy young adults: A randomized crossover trial

Isomaltulose is a low glycemic and insulinaemic carbohydrate now used as an alternative sweetener in beverages. However, it remains unclear if hydration status may be impacted differently with the consumption of beverages containing isomaltulose as compared to sucrose, a common beverage sweetener. Thirteen young adults (7 women) consumed 1 L of a carbohydrate beverage (with low electrolyte content) containing either 6.5%-sucrose, 6.5%-isomaltulose, or water within a 15 min period. For each beverage, beverage hydration index (BHI, a composite measure of fluid balance after consuming a test beverage relative to water) was calculated from urine volume produced over a 3 h period following ingestion of the carbohydrate beverages relative to water. The change in plasma volume (ΔPV), blood glucose, and lactate concentrations were assessed every 30 min post-beverage consumption. Isomaltulose ingestion attenuated urine production as compared to water and sucrose (P ≤ 0.005) over the 3 h post-ingestion period. However, no differences were observed between sucrose and water (P = 0.055). BHI was 1.53 ± 0.44 for isomaltulose (P ≤ 0.022 vs. sucrose and water) and 1.20±0.29 for sucrose (P = 0.210 vs. water). A transient reduction in ΔPV was observed following the ingestion of the isomaltulose beverage (at 30 min, P = 0.007 vs. sucrose). Thereafter, no differences in ΔPV between beverages were measured. Increases in blood glucose and lactate, indices of absorption and utility of glucose, were delayed in the isomaltulose as compared to sucrose beverage. In summary, we demonstrated a greater BHI with a carbohydrate-electrolyte beverage containing isomaltulose as compared to sucrose. This may in part be attributed to a delayed absorption of isomaltulose reducing diuresis.

Effect of the Seasonal Adaptability on Carbohydrate-electrolyte Beverage Efforts on Post-exercise Rehydration in Healthy Young Men

Objective To compare the effects of carbohydrate-electrolyte beverage on post-exercise rehydration of healthy young men in different seasons,and to explore the influence of seasonal adaptability on fluid and electrolyte balance.Methods Fifteen healthy men,aged(24.4±0.5)years,completed 2 trails in a random crossover design both in summer and winter.During recovery,they consumed a drink volume equivalent to 100% of their sweat loss with plain boiled water(the water group)or carbohydrate-electrolyte beverage(the beverage group).Recovery was monitored for further 180 minutes by the collection of blood and urine samples.Results The dehydration time in summer was significantly shorter by about 20 minutes than that in winter(t=3.045,P=0.004).In summer,the fluid retention rate of the beverage group was significantly higher than that of the water group at 120 minutes after rehydration [(83.7±2.8)% vs.(73.7±3.7)%,F=5.312,P=0.028],and significantly higher than the water group at 180 minutes [(74.8±3.6)% vs.(66.1±4.3)%,F=4.340,P=0.046].In winter,the fluid retention rate of the beverage group at 180 minutes after rehydration was significantly higher than that of the water group [(74.9±4.7)% vs.(68.0±6.0)%,F=4.128,P=0.048].There was no significantly seasonal difference in the fluid retention effect of carbohydrate-electrolyte beverage at 180 minutes after rehydration.In the beverage group,the changes of blood glucose and serum sodium levels(all P<0.05)in summer were significantly higher than those in winter at 10-180 minutes after rehydration,and the fractional excretion of sodium in summer was significantly higher in summer than in winter at 120 and 180 minutes after rehydration(F120=4.972,P=0.034;F180=8.425,P=0.007);however,there was no significant difference in plasma osmolality(all P> 0.05).For the water group,the plasma osmolality in winter was lower than that in summer,while the degree of dryness and thirst was higher in winter than in summer.Conclusions Seasonal adaptability influenced the hydration status and its regulating factors.People dehydrated faster after exercise in summer than in winter,and the hydration status was relatively stable in winter.However,in summer,the blood glucose and electrolytes responded more rapidly to carbohydrate-electrolyte beverage supply,and the plasma osmolality and subjective perception recovered faster.Therefore,during the 180-minute recovery period,the carbohydrate-electrolyte beverage had a higher rehydration efficiency in a short recovery time in summer although there was no significantly seasonal difference in the fluid retention rate.

Assessing Overall Exercise Recovery Processes Using Carbohydrate and Carbohydrate-Protein Containing Recovery Beverages.

We compared the impact of two different, but commonly consumed, beverages on integrative markers of exercise recovery following a 2 h high intensity interval exercise (i.e., running 70–80% V̇O2max intervals and interspersed with plyometric jumps). Participants (n = 11 males, n = 6 females) consumed a chocolate flavored dairy milk beverage (CM: 1.2 g carbohydrate/kg BM and 0.4 g protein/kg BM) or a carbohydrate-electrolyte beverage (CEB: isovolumetric with 0.76 g carbohydrate/kg BM) after exercise, in a randomized-crossover design. The recovery beverages were provided in three equal boluses over a 30 min period commencing 1 h post-exercise. Muscle biopsies were performed at 0 h and 2 h in recovery. Venous blood samples, nude BM and total body water were collected before and at 0, 2, and 4 h recovery. Gastrointestinal symptoms and breath hydrogen (H2) were collected before exercise and every 30 min during recovery. The following morning, participants returned for performance assessment. In recovery, breath H2 reached clinical relevance of >10 ppm following consumption of both beverages, in adjunct with high incidence of gastrointestinal symptoms (70%), but modest severity. Blood glucose response was greater on CEB vs. CM (P < 0.01). Insulin response was greater on CM compared with CEB (P < 0.01). Escherichia coli lipopolysaccharide stimulated neutrophil function reduced on both beverages (49%). p-GSK-3β/total-GSK-3β was greater on CM compared with CEB (P = 0.037); however, neither beverage achieved net muscle glycogen re-storage. Phosphorylation of mTOR was greater on CM than CEB (P < 0.001). Fluid retention was lower (P = 0.038) on CEB (74.3%) compared with CM (82.1%). Physiological and performance outcomes on the following day did not differ between trials. Interconnected recovery optimization markers appear to respond differently to the nutrient composition of recovery nutrition, albeit subtly and with individual variation. The present findings expand on recovery nutrition strategies to target functionality and patency of the gastrointestinal tract as a prerequisite to assimilation of recovery nutrition, as well as restoration of immunocompetency.

Systematic literature review: The effect of dairy milk on markers of recovery optimisation in response to endurance exercise

The food and fluid provided in the acute post-exercise period plays an essential role in endurance exercise recovery and adaptation. The current systematic literature review (SLR) aimed to identify and synthesize research that investigated the effect of dairy milk beverages in comparison to alternative post-exercise beverages on markers of ‘exercise recovery optimisation’, which may influence subsequent endurance exercise performance. Seventeen papers met the inclusion criteria. Quality assessment was undertaken using the Cochrane Collaboration’s tool for assessing risk of bias. Intervention beverages included fresh dairy milk (n= 3), chocolate flavoured dairy milk (n= 6), dairy milk-based sports beverages (n= 4), or a combination of the aforementioned beverages (n= 4). Results indicate dairy milk enhanced muscle protein synthesis (i.e., mixed fractional synthetic rate: 0.11%/h dairy milk vs. 0.08%/h control), and elicited similar rates of muscle glycogen resynthesis (5.9 mmol/kgWW/h) compared to a carbohydrate replacement beverage (7.6 mmol/kgWW/h). Seven studies investigated the effect of dairy milk beverages on hydration status, three of which found no differences in restoring net fluid balance after consumption of a dairy milk or dairy milk-based beverage compared to a carbohydrate-electrolyte beverage and (or) water, when consumed ad libitum. The remaining four studies observed a greater net fluid balance after consumption of a dairy milk or dairy milk-based beverage compared to an isovolumetric dose of a carbohydrate-electrolyte beverage and (or) water. To date, no study has investigated the effect of dairy milk consumption after endurance exercise on markers of immune competency or gastrointestinal status. Five studies observed enhanced time-trial or time-to-exhaustion performance (7.4% to 52.4%) with a dairy milk beverage compared to an isocaloric beverage, while another study found no differences. It is concluded that dairy milk may provide either comparable or superior recovery nutrition qualities with regards to muscle protein synthesis, glycogen replenishment, rehydration, and subsequent endurance exercise performance, when compared to non-nutritive, carbohydrate replacement, and (or) carbohydrate-electrolyte alternatives.

Effects of isomaltulose ingestion on postexercise hydration state and heat loss responses in young men.

What is the central question of this study? What are the effects of isomaltulose, an ingredient in carbohydrate-electrolyte beverages to maintain glycaemia and attenuate the risk of dehydration during exercise heat stress, on postexercise rehydration and physiological heat loss responses? What is the main finding and its importance? Consumption of a 6.5% isomaltulose-electrolyte beverage following exercise heat stress restored hydration following a 2h recovery as compared to a 2% solution or water only. While the 6.5% isomaltulose-electrolytes increased plasma volume and plasma osmolality, which are known to modulate postexercise heat loss, sweating and cutaneous vascular responses did not differ between conditions. Consequently, ingestion beverages containing 6.5% isomaltulose-electrolytes enhanced postexercise rehydration without affecting heat loss responses. Isomaltulose is a disaccharide carbohydrate widely used during exercise to maintain glycaemia and hydration. We investigated the effects of ingesting a beverage containing isomaltulose and electrolytes on postexercise hydration state and physiological heat loss responses. In a randomized, single-blind cross-over design, 10 young healthy men were hypohydrated by performing up to three 30min successive moderate-intensity (50% heart rate reserve) bouts of cycling, each separated by 10min, while wearing a water-perfusion suit heated to 45°C. The protocol continued until a 2% reduction in body mass was achieved. Thereafter, participants performed a final 15min moderate-intensity exercise bout followed by a 2h recovery. Following cessation of exercise, participants ingested a beverage consisting of (i) water only (Water), (ii) 2% isomaltulose (CHO-2%), or (iii) 6.5% isomaltulose (CHO-6.5%) equal to the volume of 2% body mass loss within the first 30min of the recovery. Changes in plasma volume (ΔPV) after fluid ingestion were greater for CHO-6.5% compared with CHO-2% (120min postexercise) and Water (90 and 120min) (all P≤0.040). Plasma osmolality remained elevated with CHO-6.5% compared with consumption of the other beverages at 30 and 90min postexercise (all P≤0.050). Urine output tended to be reduced with CHO-6.5% compared to other fluid conditions (main effect, P=0.069). Rectal and mean skin temperatures, chest sweat rate and cutaneous perfusion did not differ between conditions (all P>0.05). In conclusion, compared with CHO-2% and Water, consuming a beverage consisting of CHO-6.5% and electrolytes during recovery under heat stress enhances PV recovery without modulating physiological heat loss responses.

Ingesting a 12% Carbohydrate-Electrolyte Beverage Before Each Half of a Soccer Match Simulation Facilitates Retention of Passing Performance and Improves High-Intensity Running Capacity in Academy Players.

This study investigated the influence of ingesting a 12% carbohydrate plus electrolyte (CHO-E) solution providing 60g of carbohydrate before each half of a 90-min soccer match simulation (SMS) protocol on skill performance, sprint speed, and high-intensity running capacity. Eighteen elite academy (age: 18 ± 2 years) soccer players ingested two 250-ml doses (pre-exercise and at halftime) of a 12% CHO-E solution or electrolyte placebo administered in a double-blind randomized cross-over design. During an indoor (artificial grass pitch) SMS, dribbling, passing, and sprint performance were assessed, and blood was drawn for glucose and lactate analysis. High-intensity running capacity was assessed following the SMS. Dribbling speed/accuracy and sprint speed remained unchanged throughout the SMS. Conversely, passing accuracy for both dominant (mean percentage difference [95% confidence interval, CI]: 9 [3, 15]) and nondominant (mean percentage difference [95% CI]: 13 [6, 20]) feet was better maintained during the SMS on CHO-E (p < .05), with passing speed better maintained in the nondominant foot (mean percentage difference [95% CI]: 5.3 [0.7, 9.9], p = .032). High-intensity running capacity was greater in CHO-E versus placebo (mean percentage difference [95% CI]: 13 [6, 20], p = .010). Capillary blood glucose concentration was higher in CHO-E than placebo at halftime (CHO-E: 5.8 ± 0.5mM vs. placebo: 4.1 ± 0.4mM, p = .001) and following the high-intensity running capacity test (CHO-E: 4.9 ± 0.4mM vs. placebo: 4.3 ± 0.4mM, p = .001). Ingesting a 12% CHO-E solution before each half of a match can aid in the maintenance of soccer-specific skill performance, particularly on the nondominant foot, and improves subsequent high-intensity running capacity.

The rehydration potential of zea mays juice compared to carbohydrate-electrolyte beverage

The rehydration potential of zea mays juice compared to carbohydrate-electrolyte beverage

The influence of a 12% carbohydrate-electrolyte beverage on self-paced soccer-specific exercise performance.

To assess the physiological and performance effects of a 12% carbohydrate-electrolyte beverage consumed at practically applicable time-points (i.e., before each half) throughout simulated soccer match-play. Randomised, counterbalanced, crossover. Fed players (n=15) performed 90-min of soccer-specific exercise (including self-paced exercise at the end of each half). Players consumed carbohydrate-electrolyte (CHO; 60g×500ml-1, Na+ 205mg×500ml-1), placebo-electrolyte (PL) or water (Wat) beverages at the end of the warm-up (250ml) and half-time (250ml plus ad-libitum water). Blood was drawn before each half and every 15-min during exercise. Physical (15-m sprinting, countermovement jumps, self-paced distance, acceleration/deceleration count), technical (dribbling) and cognitive (memory, attention, decision-making) performance was assessed. Ratings of perceived exertion (RPE) and abdominal discomfort were measured. Against Wat and PL, CHO increased (all p<0.05) mean accelerations >1.5m·s-2 during self-paced exercise (>+25%) and dribbling speed from 60-min onwards (>+3%). Mean sprinting speed improved (+2.7%) in CHO versus Wat. Blood glucose increased before and during each half in CHO versus PL and Wat (all p<0.05). A 27% decline in glycaemia occurred at 60-min in CHO. RPE was comparable between trials. Cognition reduced post-exercise (p<0.05); this decline was not attenuated by CHO. Abdominal discomfort increased during exercise but was similar between trials. Using more realistic fluid ingestion timings than have been examined previously, consuming a 12% carbohydrate-electrolyte beverage increased blood glucose, self-paced exercise performance, and improved dribbling speed in the final 30-min of exercise compared to water and placebo. Carbohydrates did not attenuate post-exercise reductions in cognition.

Individual fluid plans versus ad libitum on hydration status in minor professional ice hockey players

BackgroundDespite exercising in cool environments, ice hockey players exhibit several dehydration risk factors. Individualized fluid plans (IFPs) are designed to mitigate dehydration by matching an individual’s sweat loss in order to optimize physiological systems and performance.MethodsA randomized control trial was used to examine IFP versus ad libitum fluid ingestion on hydration in 11 male minor professional ice hockey players (mean age = 24.4 ± 2.6 years, height = 183.0 ± 4.6 cm, weight = 92.9 ± 7.8 kg). Following baseline measures over 2 practices, participants were randomly assigned to either control (CON) or intervention (INT) for 10 additional practices. CON participants were provided water and/or carbohydrate electrolyte beverage to drink ad libitum. INT participants were instructed to consume water and an electrolyte-enhanced carbohydrate electrolyte beverage to match sweat and sodium losses. Urine specific gravity, urine color, and percent body mass change characterized hydration status. Total fluid consumed during practice was assessed.ResultsINT consumed significantly more fluid than CON (1180.8 ± 579.0 ml vs. 788.6 ± 399.7 ml, p = 0.002). However, CON participants replaced only 25.4 ± 12.9% of their fluid needs and INT 35.8 ± 17.5%. Mean percent body mass loss was not significantly different between groups and overall indicated minimal dehydration (<1.2% loss). Pre-practice urine specific gravity indicated CON and INT began hypohydrated (mean = 1.024 ± 0.007 and 1.024 ± 0.006, respectively) and experienced dehydration during practice (post = 1.026 ± 0.006 and 1.027 ± 0.005, respectively, p < 0.001). Urine color increased pre- to post-practice for CON (5 ± 2 to 6 ± 1, p < 0.001) and INT (5 ± 1 to 6 ± 1, p < 0.001).ConclusionsParticipants consistently reported to practice hypohydrated. Ad libitum fluid intake was not significantly different than IFP on hydration status. Based on urine measures, both methods were unsuccessful in preventing dehydration during practice, suggesting practice-only hydration is inadequate to maintain euhydration in this population when beginning hypohydrated.

Impact of Carbohydrate-Electrolyte Beverage Ingestion on Heart Rate Response While Climbing Mountain Fuji at ~3000 m.

We sought to investigate whether carbohydrate-electrolyte beverage ingestion reduced heart rate (HR) in twenty-three healthy young adults while climbing Mount Fuji at a given exercise intensity. Twenty-three healthy adults were randomly divided into two groups: the tap water (11 males [M] and 1 female [F]) and the carbohydrate-electrolyte group (10 M and 1 F). HR and activity energy expenditure (AEE) were recorded every min. The HRs for the first 30 minutes of climbing were not significantly different between the groups [121 ± 2 beats per min (bpm) in the tap water and 116 ± 3 bpm in the carbohydrate-electrolyte]; however, HR significantly increased with climbing in the tap water group (129 ± 2 bpm) but showed no significant increase in the carbohydrate-electrolyte group (121 ± 3 bpm). In addition, body weight changes throughout two days ascending and descending on Mount Fuji were inversely related to changes in resting HR. Further, individual variation of body weight changes was suppressed by carbohydrate-electrolyte drink. Collectively, carbohydrate-electrolyte beverage intake may attenuate an increase in HR at a given AEE while mountaineering at ~3000 m compared with tap water intake.

Caffeine Does Not Affect Improvements in Cognition During Prolonged High-Intensity Exercise in Alert Well-Trained Individuals

Background: Recent research has demonstrated improvements in cognitive function during bouts of high-intensity endurance exercise. Caffeine, the most commonly used ergogenic aid in the world, can improve cognition both at rest and during exercise and can also improve exercise performance during simulated cycling races. Purpose: To determine if caffeine ingestion in conjunction with prolonged high-intensity exercise can synergistically improve cognitive function, and whether the type of exercise trial affects the cognitive response. Methods: Seven well-trained cyclists and triathletes (26.9 ± 3.9 years, VO2 peak 67.7 ± 10.3 mL/kg/h) completed two trials to exhaustion (TTE) at 90% VO2 peak and two 50 km time trials (TTD), 1 hour after consuming a carbohydrate–electrolyte beverage (5 mL/kg, 6.3% CHO, 18 mM sodium) and a capsule containing either 6 mg/kg of caffeine or a placebo (double-blind crossover design). A second CHO beverage was consumed at the onset of each trial. Cognitive function was measured before and after exercise using a computerized ANAM® test and Stroop word–color test (also conducted during exercise). Results: Average wakefulness scores at baseline indicated that subjects were at near peak alertness. Caffeine ingestion did not influence exercise performance, ANAM thruput scores, or Stroop word–color test response times in either trial type. However, exercise significantly improved ANAM and Stroop cognitive results, regardless of exercise trial. Conclusion: In alert well-trained athletes, high-intensity endurance exercise can significantly improve tests of simple and complex cognitive function. Neither exercise trial type nor caffeine ingestion impacts the exercise-induced changes in cognitive function.

Beverage Composition Influences Ad Libitum Consumption, Hydration Status And Affect During Exercise In The Heat

Maintaining a sufficient level of hydration can have a substantial effect on performance outcomes, especially in endurance exercise. How an exerciser feels (pleasure vs. displeasure) could in theory, depend on their ability to maintain fluid balance, ultimately affecting their performance. PURPOSE: To determine the effect of ad libitum consumption of either a carbohydrate-electrolyte beverage (CES), water (WAT), or a electrolyte-free, non-caloric, flavor-matched placebo drink (PLA) on hydration status and affective responses. METHODS: Seventeen trained men (mean±SD; 25.4±4.0 y, VO2peak = 53.3±6.8mL kg-1 min-1) completed three intervention trials in a randomized, double-blind, counter-balanced, cross-over design. Trials involved two hours of steady state (SS) cycle ergometry at 68.4±9.3% VO2peak in the heat (WBGT=24.4±1.7°C) with ad libitum WAT, PLA, or CES. Indices of affective responses and fluid balance were recorded prior to and every 30 min during SS cycling exercise. RESULTS: Physiologically, plasma glucose was significantly greater with CES than WAT and PLA for all time points during SS (p<0.05). A significant difference was found in plasma sodium levels at 120 min (p<0.05). Plasma osmolality was significantly greater with CES compared to WAT at 90 min (p<0.05), and significantly greater than WAT and PLA at 120 min (p<0.05). Greater fluid intake was observed at all time points with CES compared to water (p<0.05). CES elicited significantly greater mean affective response than PLA and WAT only at 120 min (p<0.05). CONCLUSION: Greater affect during CES appears to be supported by a greater fluid intake and plasma osmolality, possibly due to the higher plasma glucose and sodium levels compared to other treatments. Thus, the improved fluid balance in the CES condition may have contributed to the improved feelings of affect (more pleasure) at the end of 2 hrs of SS cycling exercise, which was independent of flavor due to the flavor-matched PLA. Collectively, affective responses appear sensitive to changes in indices of hydration status during prolonged endurance exercise in hot environmental conditions. As such, affect may reflect a signal to induce drinking behaviors that maintain fluid balance and protect bodily homeostasis. Funded by The Coca-Cola Company NCT01893853

Milk: An Alternative Beverage for Hydration?

The hydration status of a physically active individual or athlete can influence his/her physical or mental performance. The degree of hypohydration may lead to serious health problems, and consequently to impair athletic performance. The consumption of water or carbohydrate-electrolyte beverages before, during and after exercise is essential to maintain fluid balance and prevent dehydration. Besides these drinks, research findings have pointed using bovine milk as an alternative to sports drinks to optimize hydration levels in athletes and physically active individuals. The nutritional composition of cow’s milk promotes post-exercise rehydration process, due to the natural presence of water and electrolytes such as sodium and potassium. Although most studies have confirmed that bovine milk is a viable alternative for rehydration, recent studies have not reported significant differences between milk and some sports drinks for hydration process. Thus, milk consumption could be used as an alternative beverage for the hydration process.

Effects Of Low-fat Chocolate Milk, Carbohydrate-protein Supplement, And Carbohydrate-electrolyte Beverage On The Restoration Of Muscle Glycogen Following Exhaustive Exercise

Effects Of Low-fat Chocolate Milk, Carbohydrate-protein Supplement, And Carbohydrate-electrolyte Beverage On The Restoration Of Muscle Glycogen Following Exhaustive Exercise

Fluid Balance and Performance are Improved with Ad Libitum Carbohydrate-electrolyte Beverage Intake in the Heat

Fluid Balance and Performance are Improved with Ad Libitum Carbohydrate-electrolyte Beverage Intake in the Heat

PENGARUH PEMBERIAN AIR KELAPA TERHADAP KEBUGARAN ATLET SEPAK BOLA

Background: The athlete’s fitness is one of the supporting factor for athlete’s performance. Consumption of carbohydrate-electrolyte beverage during training maintain hydration status and athlete’s performance. Coconut water is potential natural fluid that can be used as natural sport drink. Objective: The aim of this study was to verify the effect of additional sugar in coconut water on soccer athlete’s fitness Methode: An experimental study was done in randomized pretest - post test design with a control group. The subject were 18 soccer’s player aged 14-18 years at Persatuan Sepak Bola Kudus in August 2012. The control group is consumed pure coconut water and the treatment group is consumed coconut water which added with 3 g of sugar every 100 ml. The amount of fluid given based on fluid requirement during training. After physical training during 90minutes, all player completed the fitness test with cooper test 12 minutes run. Result: Consumption of coconut water affect the results of VO2 max on control group (p=0.016), and has no significant effect on treatment group (p=0,871). There no significant different between two groups in consumption of energy(p=0.643), fluid before training(p=0.385), body fat(p=0,698) and muscle mass(p=0.919) Conclusion: Consumption of pure coconut water affected on change value of VO2 max compared with coconut water which added with sugar

Skeletal muscle volume following dehydration induced by exercise in heat

BackgroundIntracellular skeletal muscle water is redistributed into the extracellular compartment during periods of dehydration, suggesting an associated decline in muscle volume. The purpose of this study was to evaluate skeletal muscle volume in active (knee extensors (KE)) and less active (biceps/triceps brachii, deltoid) musculature following dehydration induced by exercise in heat.MethodsTwelve participants (seven men, five women) cycled in the heat under two conditions: (1) dehydration (DHYD) resulting in 3% and 5% losses of estimated total body water (ETBW), which was assessed by changes in body mass, and (2) fluid replacement (FR) where 3% and 5% losses of ETBW were counteracted by intermittent (20 to 30 min) fluid ingestion via a carbohydrate-electrolyte beverage. During both conditions, serum osmolality and skeletal muscle volume (assessed by magnetic resonance imaging) were measured at baseline and at the 3% and 5% ETBW loss measurement points.ResultsIn DHYD, serum osmolality increased at 3% (p = 0.005) and 5% (p < 0.001) ETBW losses, while FR decreased serum osmolality at the 5% loss of ETBW time point (p = 0.009). In DHYD, KE muscle volume declined from 1,464 ± 446 ml to 1,406 ± 425 ml (3.9%, p < 0.001) at 3% ETBW loss and to 1,378 ± 421 ml (5.9%, p < 0.001) at 5% ETBW loss. The largest decline in KE volume in DYHD occurred in the mid-belly (31 ml, p = 0.001) and proximal (24 ml, p = 0.001) regions of the grouped vasti muscles. There were no changes in volume for the biceps/triceps (p = 0.35) or deltoid (p = 0.92) during DHYD. FR prevented the loss of KE muscle volume at 3% (1,430 ± 435 ml, p = 0.074) and 5% (1,431 ± 439 ml, p = 0.156) ETBW loss time points compared to baseline (1,445 ± 436 ml).ConclusionsFollowing exercise in the heat, the actively contracting muscles lost volume, while replacing lost fluids intermittently during exercise in heat prevented this decline. These results support the use of muscle volume as a marker of water loss.

The Effect of Carbohydrate-Electrolyte Beverage Drinking Strategy on 10-Mile Running Performance

The purpose of the current study was to investigate the influence of ingesting a carbohydrate-electrolyte (CHO-E) beverage ad libitum or as a prescribed volume on 10-mile run performance and gastrointestinal (GI) discomfort. Nine male recreational runners completed the 10-mile run under the following 3 conditions: no drinking (ND; 0 ml, 0 g CHO), ad libitum drinking (AD; 315 ± 123 ml, 19 ± 7 g CHO), and prescribed drinking (PD; 1,055 ± 90 ml, 64 ± 5 g CHO). During the AD and PD trials, drinks were provided on completion of Miles 2, 4, 6, and 8. Running performance, speed (km/hr), and 10-mile run time were assessed using a global positioning satellite system. The runners' ratings of perceived exertion and GI comfort were recorded on completion of each lap of the 10-mile run. There was a significant difference (p < .10) in performance times for the 10-mile race for the ND, AD, and PD trials, which were 72:05 ± 3:36, 71:14 ± 3:35, and 72:12 ± 3.53 min:s, respectively (p = .094). Ratings of GI comfort were reduced during the PD trial in comparison with both AD and ND trials. In conclusion, runners unaccustomed to habitually drinking CHO-E beverages during training improved their 10-mile race performance with AD drinking a CHO-E beverage, in comparison with drinking a prescribed volume of the same beverage or no drinking.

Effect of betaine supplementation on cycling sprint performance

PurposeTo examine the effect of betaine supplementation on cycling sprint performance.MethodsSixteen recreationally active subjects (7 females and 9 males) completed three sprint tests, each consisting of four 12 sec efforts against a resistance equal to 5.5% of body weight; efforts were separated by 2.5 min of cycling at zero resistance. Test one established baseline; test two and three were preceded by seven days of daily consumption of 591 ml of a carbohydrate-electrolyte beverage as a placebo or a carbohydrate-electrolyte beverage containing 0.42% betaine (approximately 2.5 grams of betaine a day); half the beverage was consumed in the morning and the other half in the afternoon. We used a double blind random order cross-over design; there was a 3 wk washout between trials two and three. Average and maximum peak and mean power were analyzed with one-way repeated measures ANOVA and, where indicated, a Student Newman-Keuls.ResultsCompared to baseline, betaine ingestion increased average peak power (6.4%; p < 0.001), maximum peak power (5.7%; p < 0.001), average mean power (5.4%; p = 0.004), and maximum mean power (4.4%; p = 0.004) for all subjects combined. Compared to placebo, betaine ingestion significantly increased average peak power (3.4%; p = 0.026), maximum peak power max (3.8%; p = 0.007), average mean power (3.3%; p = 0.034), and maximum mean power (3.5%; p = 0.011) for all subjects combined. There were no differences between the placebo and baseline trials.ConclusionsOne week of betaine ingestion improved cycling sprint power in recreationally active males and females.

Comparison of coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men

BackgroundSport drinks are ubiquitous within the recreational and competitive fitness and sporting world. Most are manufactured and artificially flavored carbohydrate-electrolyte beverages. Recently, attention has been given to coconut water, a natural alternative to manufactured sport drinks, with initial evidence indicating efficacy with regard to maintaining hydration. We compared coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men.MethodsFollowing a 60-minute bout of dehydrating treadmill exercise, 12 exercise-trained men (26.6 ± 5.7 yrs) received bottled water (BW), pure coconut water (VitaCoco®: CW), coconut water from concentrate (CWC), or a carbohydrate-electrolyte sport drink (SD) [a fluid amount based on body mass loss during the dehydrating exercise] on four occasions (separated by at least 5 days) in a random order, single blind (subject and not investigators), cross-over design. Hydration status (body mass, fluid retention, plasma osmolality, urine specific gravity) and performance (treadmill time to exhaustion; assessed after rehydration) were determined during the recovery period. Subjective measures of thirst, bloatedness, refreshed, stomach upset, and tiredness were also determined using a 5-point visual analog scale.ResultsSubjects lost approximately 1.7 kg (~2% of body mass) during the dehydrating exercise and regained this amount in a relatively similar manner following consumption of all conditions. No differences were noted between coconut water (CW or CWC) and SD for any measures of fluid retention (p > 0.05). Regarding exercise performance, no significant difference (p > 0.05) was noted between BW (11.9 ± 5.9 min), CW (12.3 ± 5.8 min), CWC (11.9 ± 6.0 min), and SD (12.8 ± 4.9 min). In general, subjects reported feeling more bloated and experienced greater stomach upset with the CW and CWC conditions.ConclusionAll tested beverages are capable of promoting rehydration and supporting subsequent exercise. Little difference is noted between the four tested conditions with regard to markers of hydration or exercise performance in a sample of young, healthy men. Additional study inclusive of a more demanding dehydration protocol, as well as a time trial test as the measure of exercise performance, may more specifically determine the efficacy of these beverages on enhancing hydration and performance following dehydrating exercise.