Introduction: The aim of the present study was to investigate the effect of ingesting a glucose plus fructose drink compared with a glucose-only drink (both delivering carbohydrate at a rate of 1.8 g·min−1) and a water placebo on endurance performance.
Methods: Eight male trained cyclists were recruited (age 32 ± 7 yr, weight 84.4 ± 6.9 kg, V˙O2max 64.7 ± 3.9 mL·kg−1·min−1, Wmax 364 ± 31 W). Subjects ingested either a water placebo (P), a glucose (G)-only beverage (1.8 g·min−1), or a glucose and fructose (GF) beverage in a 2:1 ratio (1.8 g·min−1) during 120 min of cycling exercise at 55% Wmax followed by a time trial in which subjects had to complete a set amount of work as quickly as possible (~1 h). Every 15 min, expired gases were analyzed and blood samples were collected.
Results: Ingestion of GF resulted in an 8% quicker time to completion during the time trial (4022 s) compared with G (3641 s) and a 19% improvement compared with W (3367 s). Total carbohydrate (CHO) oxidation was not different between GF (2.54 ± 0.25 g·min−1) and G (2.50 g·min−1), suggesting that GF led to a sparing of endogenous CHO stores, because GF has been shown to have a greater exogenous CHO oxidation than G.
Conclusion: Ingestion of GF led to an 8% improvement in cycling time-trial performance compared with ingestion of G.
Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Birmingham, UNITED KINGDOM
Address for correspondence: Asker E. Jeukendrup, M.Sc., Ph.D., Professor of Exercise Metabolism, Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Birmingham, B15 2TT, United Kingdom; E-mail: email@example.com.
Submitted for publication April 2007.
Accepted for publication September 2007.