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Paolo C. Colombani, Eva Kovacs, Petra Frey-Rindova, Walter Frey, Wolfgang Langhans, Myrtha Arnold and Caspar Wenk

A field study was performed to investigate the acute influence of a milk protein hydrolysate supplemented drink (CHO+PRO) on metabolism during and after a marathon run compared to the same drink without protein (CHO). Carbohydrate metabolites and hormones were not influenced by CHO+PRO. Levels of plasma free fatty acids were significantly lower and levels of urea and most amino acids were significantly higher with CHO+PRO. Sweat urea and ammonia nitrogen excretion during the run as well as urinary 3-methylhistidine excretion during the entire exercise day was similar with both treatments. Urinary total nitrogen was significantly increased and urinary pH decreased with CHO+PRO. It was concluded that the supplemented protein was absorbed and probably at least partially oxidized during the run and that no obvious negative metabolic effects occurred. CHO+PRO did not acutely affect myofibrillar protein breakdown as assessed by the 3-methylhistidine method: however, total body protein breakdown was not measured.

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Jeffrey J. Zachwieja, David L. Costill, Glenn C. Beard, Robert A. Robergs, David D. Pascoe and Dawn E. Anderson

To determine the effect of a carbonated carbohydrate (CHO) drink on gastric function and exercise performance, eight male cyclists completed four 120- min bouts of cycling. Each bout consisted of a 105-min ride at 70% VO2max followed by a 15-min self-paced performance ride. During each trial, one of four test solutions was ingested: carbonated CHO (C-10%), noncarbonated CHO (NC-10%), carbonated non-CHO (C), and noncarbonated non-CHO (NC). Following the performance ride, the subjects had their stomach contents removed by aspiration. There were no significant differences in gastric emptying (GE) except for Trial C-10%, which averaged 13.3% less than NC. However, there was no difference in the perception of gastrointestinal comfort between this trial and any other. Average power output during the performance ride was not significantly different between carbonated and noncarbonated trials, or between CHO-fed and no-CHO trials; however, the subjects worked at a greater intensity when fed CHO. Finally, acid base status did not change when a carbonated drink was ingested. This indicates that adding carbonation to a sport drink does not significantly alter gastric function, the perception of GI comfort, or exercise performance.

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Rebecca A. Skillen, Massimo Testa, Elizabeth A. Applegate, Eric A. Heiden, Andrea J. Fascetti and Gretchen A. Casazza

This study examined the effect of amino acids in a carbohydrate beverage on cycling performance. Twelve male athletes (28.5 pp2.1 yr) cycled at 75% VO2peak for 90 min followed by a ride to exhaustion at 85% VO2peak, before (T1) and on 2 consecutive days (T2 and T3) after 2 weeks of supplementation with 3.6% carbohydrate plus 1% amino acids (AA) or 4.6% carbohydrate-only (CHO) isocaloric beverages. Muscle damage was assessed by plasma creatine kinase (CK), and muscle fatigue by changes in vertical jump pre- to postexercise. Muscle soreness, overall fatigue, and changes in mood state were assessed using questionnaires. Plasma CK was lower for AA in T3 (214.0 ss13.5 vs. 485.9 11191.4 U/L immediately post, 213.9 ÷ 13.1 vs. 492.0 ÷ 199.4 U/L 5 hr post, and 194.9 ÷ 17.9 vs. 405.9 ÷ 166.6 U/L 24 hr postexercise in AA and CHO, respectively). Time to exhaustion decreased from T2 to T3 only in CHO (10.9 ÷ 2.5 to 12.6 ÷ 3.2 vs. 13.8 ÷ 2.8 to 7.8 ÷ 1.5 min in AA and CHO, respectively). Vertical-jump change from pre- to postexercise was greater in T3 for the CHO treatment. Total fatigue score and mood disturbance decreased significantly only with AA in T3. The addition of AA to a carbohydrate beverage after consecutive-day exercise bouts reduced muscle damage as indicated by CK levels, decreased fatigue, and maintained exercise performance compared with consuming carbohydrate alone.

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Allan H. Goldfarb, Changmo Cho, Hojune Cho, Brett Romano-Ely and M. Kent Todd

The purpose of this study was to determine whether an isocaloric beverage with added protein and vitamins (CHOPA) would influence oxidative stress and inflammation after cycling to exhaustion as indicated by plasma protein carbonyls (PC), lipid hydroperoxides (LOOH), and interleukin-6 (IL-6). Twelve trained men (18–33 yr) volunteered and performed this randomized crossover study. Participants cycled at 70% VO2peak until fatigue and at 80% VO2peak 22–24 hr later to fatigue with either carbohydrate or CHOPA. Blood collected before the cycling at rest and 24, 48, and 72 hr after the exercise was analyzed for PC and LOOH spectrophotometrically and for IL-6 via an enzyme-linked immunosorbent assay. The data were analyzed with SPSS using repeated-measures ANOVA. PC demonstrated significant treatment (p = .037) and time (p = .004) effects with no Treatment × Time interaction. PC was higher in the CHOPA treatment than with CHO independent of time and increased at 24 (48%), 48 (59%), and 72 (67%) hr after exercise compared with preexercise values. Resting LOOH and IL-6 did not have any significant changes with time or treatment. These data indicate that an isocaloric CHOPA drink after 2 cycling bouts to exhaustion will exacerbate the resting PC level compared with an isocaloric drink, with no influence on plasma LOOH or IL-6. In addition, a modest significant increase in PC over time independent of treatment occurred, which suggests a mild oxidative stress in the days after exhaustive exercise.

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Michael C. Riddell, Sara L. Partington, Nicole Stupka, David Armstrong, C. Rennie and Mark A. Tarnopolsky

Compared to males, females oxidize proportionately more fat and less carbohydrate during endurance exercise performed in the fasted state. This study was designed to test the hypothesis that there may also be gender differences in exogenous carbohydrate (CHOexo) oxidation during exercise. Healthy, young males (n = 7) and females (n = 7) each completed 2 exercise trials (90 min cycle ergometry at 60% VO2peak), 1 week apart. Females were eumenorrheic and were tested in the midfollicular phase of their menstrual cycle. Subjects drank intermittently either 8% CHOexo (1 g glucose · kg · h−1) enriched with U-13C glucose or an artificially sweetened placebo during the trial. Whole-body substrate oxidation was determined from RER, urinary urea excretion, and the ratio of 13C:12C in expired gas during the final 60 min of exercise. During the placebo trial, fat oxidation was higher in females than in males (0.42 · 0.07 vs. 0.32 · 0.09 g · min−1 · kg LBM–1 × 10–2) at 30 min of exercise (p < .05). When averaged over the final 60 min of exercise, the relative proportions of fat, total carbohydrate, and protein were similar between groups. During CHOexo ingestion, both the ratio of 13C:12C in expired gas (p < .05) and the proportion of energy derived from CHOexo relative to LBM (p < .05) were higher in females compared to males at 75- and 90-min exercise. When averaged over the final 60 min of exercise, the percentage of CHOexo to the total energy contribution tended to be higher in females (14.3 · 1.2%) than in males (11.2 · 1.2%; p = .09). The reduction in endogenous CHO oxidation with CHOexo intake was also greater in females (12.9 · 3.1%) than in males (5.1 · 2.0%; p = .05). Compared to males, females may oxidize a greater relative proportion of CHOexo during endurance exercise which, in turn, may spare more endogenous fuel. Based on these observations, ingested carbohydrate may be a particularly beneficial source of fuel during endurance exercise for females.

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Costas A. Anastasiou, Stavros A. Kavouras, Christina Koutsari, Charalambos Georgakakis, Katerina Skenderi, Michael Beer and Labros S. Sidossis

This study examined the effect of maltose-containing sports drinks on exercise performance. Ten subjects completed 4 trials. Each trial consisted of a glycogen depletion protocol, followed by a 15-min refueling, after which subjects performed an 1-h performance test while consuming one of the experimental drinks (HGlu, glucose; HMal, maltose; MalMix, sucrose, maltose, and maltodextrin; Plac, placebo). Drinks provided 0.65 g/kg body weight carbohydrates during refueling and 0.2 g/kg every 15 min during the performance test. Although no significant differences were found in performance (HGlu: 67.2 ± 2.0; HMal: 68.6 ± 1.7; MalMix: 66.7 ± 2.0; Plac: 69.4 ± 3.0 min, P > 0.05), subjects completed the MalMix trial 3.9% faster than the Plac. Carbohydrate drinks caused comparable plasma glucose values that were significantly higher during refueling and at the end of exercise, compared to Plac. The data suggest that although carbohydrate drinks help to maintain plasma glucose at a higher level, no differences in performance could be detected after glycogen-depleting exercise.

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Richard B. Kreider, Dawn Hill, Greg Horton, Michael Downes, Sarah Smith and Beth Anders

The purpose of this study was to determine the effects of carbohydrate supplementation during intense training on dietary patterns, psychological status, and markers of anaerobic and aerobic performance. Seven members of the U.S. National Field Hockey Team were matched to 7 team counterparts (N = 14). One group was blindly administered a carbohydrate drink containing 1 g·kg−1 of carbohydrate four times daily, while the remaining group blindly ingested a flavored placebo during 7 days of intense training. Subjects underwent pre- and posttraining aerobic and anaerobic assessments, recorded daily diet intake, and were administered the Profile of Mood States (POMS) psychological inventory prior to and following each practice. Results revealed that the carbohydrate-supplemented group had a greater (p < .05) total energy intake, carbohydrate intake, and change (pre vs. post) in time to maximal exhaustion following training while reporting less postpractice psychological fatigue. However, no significant differences were observed in remaining psychological, physiological, or performance-related variables.

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Mette Hansen, Jens Bangsbo, Jørgen Jensen, Bo Martin Bibby and Klavs Madsen

This trial aimed to examine the effect of whey protein hydrolysate intake before and after exercise sessions on endurance performance and recovery in elite orienteers during a training camp. Eighteen elite orienteers participated in a randomized controlled intervention trial during a 1-week training camp (13 exercise sessions). Half of the runners (PRO-CHO) ingested a protein drink before (0.3 g kg−1) and a protein-carbohydrate drink after (0.3 g protein kg−1 and 1 g carbohydrate kg−1) each exercise session. The others ingested energy and timematched carbohydrate drinks (CHO). A 4-km run-test with 20 control points was performed before and on the last day of the intervention. Blood and saliva were obtained in the mornings, before and after run-tests, and after the last training session. During the intervention, questionnaires were fulfilled regarding psychological sense of performance capacity and motivation. PRO-CHO and not CHO improved performance in the 4-km run-test (interaction p < .05). An increase in serum creatine kinase was observed during the week, which was greater in CHO than PRO-CHO (interactionp < .01). Lactate dehydrogenase (p < .001) and cortisol (p = .057) increased during the week, but the change did not differ between groups. Reduction in sense of performance capacity during the intervention was greater in CHO (p < .05) than PRO-CHO. In conclusion, ingestion of whey protein hydrolysate before and after each exercise session improves performance and reduces markers of muscle damage during a strenuous 1-week training camp. The results indicate that protein supplementation in conjunction with each exercise session facilitates the recovery from strenuous training in elite orienteers.

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Matthew S. Hickey, David L. Costill and Scott W. Trappe

This study investigated the influence of drink carbonation and carbohydrate content on ad libitum drinking behavior and body fluid and electrolyte responses during prolonged exercise in the heat. Eight competitive male runners completed three 2-hr treadmill runs at 60% VO2max in an environmental chamber maintained at 30 C° and 40% RH. Three test drinks were used: 8% carbohydrate, low carbonation (8%-C); 8% carbohydrate, noncarbonated (8%-NC), and water (0%-NC). Blood samples were taken preexercise (0), at 60 and 120 min of exercise, and at 60 min of recovery (+60 min). The data suggest that while reports of heartburn tend to be higher on 8% carbohydrate drinks than on 0%-NC, this does not appear to be a function of drink carbonation. Similarly, the increased frequency of heartbum did not significantly reduce fluid consumption either during exercise or during a 60-min recovery period. Importantly, no differences were observed between fluid and electrolyte, or thermoregulatory responses to the three sport drinks. Thus, consumption of low-carbonation beverages does not appear to significantly influence drinking behavior or the related physiological responses during prolonged exercise in the heat.

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Alan J. Ryan, Amy E. Navarre and Carl V. Gisolfi

These studies were done to determine the effect of carbonation and carbohydrate content on either gastric emptying or ad libitum drinking during treadmill exercise in the heat. Four test drinks were used: a 6% carbohydrate, noncarbonated; a 6% carbohydrate, carbonated; a 10% carbohydrate, noncarbonated; and a 10% carbohydrate, carbonated drink. For gastric emptying studies, subjects completed four 1-hr treadmill runs in the heat. They were given 400 mL of test drink at 0 rnin and 200 mL at 15, 30, and 45 min of exercise. For ad libitum drinking studies, subjects completed four 2-hr treadmill runs in the heat. Gastric residual volumes were similar during the four 1-hr runs. During the 2-hr runs, ad libitum drinking of the four beverages was also similar. Mean values for sweat rate, percentage of body weight lost, and percentage of fluid replaced by ad libitum drinking were similar for the four trials. Similar changes in heart rate, rectal temperature, and ratings of perceived exertion were also observed during the four 2-hr treadmill runs. We conclude that the presence of carbonation in a carbohydrate drink did not have a significant effect on either gastric emptying or ad libitum drinking.