G-15F FREE COMMUNICATION/SLIDE THIRST, BEVERAGE COMPOSITION, AND HYDRATION
The osmolyte betaine offers interesting promise as an ingredient in rehydration fluids.
To compare the effects of rehydration with betaine, versus other fluids, on running performance, metabolism, and blood constituents.
Ten male runners (mean±SE age, 20.1±0.6y; body mass, 70.6±2.3kg; VO2max, 63.5±1.4ml/kg/min) were studied using a double-blind, randomized, crossover design. Subjects participated in four controlled tests, using a different rehydration solution during each: 6% carbohydrate-electrolyte fluid replacement beverage (C); C+5g betaine (C+B); a non-nutritive, flavored placebo beverage (P); or P+5g betaine (P+B). Runners dehydrated to −2.7±0.1% body weight overnight, performed morning exercise, then rehydrated to −1.3% body weight. Treadmill trials (75 min, 65%VO2max) in 31°C heat included a timed sprint to exhaustion (90%VO2max).
There were no significant between- treatment differences in diet, hydration indices, sprint time to exhaustion, rectal temperature, skin temperature, heart rate, sweat rate, and ratings of perceived exertion, thermal sensation, or thirst. In trial C+B (228±58 sec) versus C (196±40 sec), sprint time to exhaustion approached significance (P=.09). Further, a significant increase in plasma lactate and in oxygen consumption (C+B >C, p < .05) occurred during the sprint (lactate and VO2) and 15-min post- sprint (lactate). Regarding the two placebo trials, betaine induced plasma volume expansion after resting rehydration (P+B >P, p < .05); during exercise, this state was reversed (P >P+B, p < .05).
Addition of betaine (5g/L) to C resulted in (a) a 32 sec improvement in mean sprint time to exhaustion (C+B versus C, P > .05, NS), and (b) evidence of enhanced anaerobic and aerobic metabolism, despite sprinting at an identical treadmill speed. Rehydration with the osmolyte betaine also resulted in differential plasma volume changes (P+B versus P) at rest and during exercise. Supported by Danisco USA Inc.