Citation

Rowlands DS, Bonetti DL, Hopkins WG. Int. J. Sport Nutr. Exerc. Metab. 2013; ePub(ePub): ePub.

Affiliation

School of Sport and Exercise, Massey University, Wellington, New Zealand.

Copyright

(Copyright © 2013, Human Kinetics Publishers)

DOI

unavailable

PMID

21975013

Abstract

Isotonic sports drinks are often consumed to offset the effects of dehydration and to improve endurance performance, but hypotonic drinks may be more advantageous. The purpose of the study was to compare absorption and effects on performance of a commercially available hypotonic sports drink (Mizone Rapid: 3.9% carbohydrate, 218 mOsmol·kg-1) with an isotonic drink (Powerade: 7.6%, 281 mOsmol·kg-1), a hypertonic drink (Gatorade: 6%, 327 mOsmol·kg-1), and non-caloric placebo (8 mOsmol·kg-1). In a crossover, 11 cyclists consumed each drink on separate days at 250 ml·15 min-1 during a 2-h preload ride at 55% peak power followed by an incremental test to exhaustion. Small to moderate increases in D2O enrichment in the preload were observed with Mizone Rapid relative to Powerade, Gatorade, and placebo (differences of 88, 45, and 42 parts per million respectively; 90% confidence limits ±28). Serum osmolality was moderately lower with Mizone Rapid vs Powerade and Gatorade (-1.9, -2.4; mOsmol·L-1; ±1.2 mOsmol·L-1) but not clearly different vs placebo. Plasma volume reduction was small to moderate with Mizone Rapid, Powerade and Gatorade relative to placebo (-1.9%, -2.5%, -2.9%; ±2.5%). Gut comfort was highest with Mizone Rapid but clearly different (8.4%; ±4.8%) only vs Powerade. Peak power was highest with Mizone Rapid (380 W) vs placebo and other drinks (1.2-3.0%; 99% confidence limits ±4.7%), but differences were inconclusive with reference to the smallest important effect (~1.2%). The outcomes are consistent with fastest fluid absorption with the hypotonic sports drink. Further research should determine if the effect has meaningful impact on performance.

Language: en