Eighteen highly-trained runners ran two half marathons in mild environmental conditions, 3 wk apart, consuming either 426 ± 227 mL of a flavored placebo drink (PLACEBO) or an equivalent volume of water (386 ± 185 mL) and a commercial gel (GEL) supplying 1.1 ± 0.2 g/kg body mass (BM) carbohydrate (CHO). Voluntary consumption of this fluid was associated with a mean BM change of ~ 2.4%. Runners performed better in their second race by 0.9% or 40 s (P = 0.03). Three runners complained of gastrointestinal discomfort in GEL trial, which produced a clear impairment of half-marathon performance by 2.4% or 105 s (P = 0.03 ) . The effect of GEL on performance was trivial: time was improved b y 0.3% or 14 s compared with PLACEBO (P = 0.52). Consuming the gel was associated with a 2.4% slower time through the 2 × 200 m feed zone; adding a trivial ~ 2 s to race time. Although benefits to half marathon performance were not detected, the theoretical improvement during 1-h exercise with CHO intake merits further investigation.
Burke and Wood are with the Dept of Sports Nutrition, Australian Institute of Sport, Belconnen, ACT 2616 Australia; Burke is also with the School of Exercise and Nutrition Sciences, Deakin University, Burwood, Victoria 3025, Australia. Pyne and Saunders are with the Dept of Physiology, Australian Institute of Sport, Belconnen, ACT 2616, Australia. Telford is with the Track and Field Program, Australian Institute of Sport, Belconnen, ACT 2616, Australia.