Mixed drink increased carbohydrate oxidation but not performance during a 40 km time trial

Abstract

Background: The present study aimed to determine whether consuming a glucose polymer (GP) and fructose would result in increased carbohydrate oxidation rates and improve 40 km time trial performance compared with an isocaloric GP-only drink.

Methods: Eight well-trained male competitive cyclists (VO_2max 62.7 ± 9.4 ml/kg/min, power output 5.1 ± 0.6 Watts/kg) participated in three visits consisting of a peak power output (W_max) and VO₂ max test and two separate visits of a 105 minute steady state ride (at 65% W_max), followed by a 40 km time trial. Participants received 1.2 g/min of either a GP or mixed drink every 15 min.

Results: No differences were found in the 40 km performance between GP (69:14 min ± 4.12, mean ± SD) and the mixed drink (66:58 min ± 4.51, mean ± SD) trials (p = 0.289). There were no differences in blood glucose or lactate between the trials. No differences in total oxidation were found in either carbohydrate or fat oxidation rates; however, exogenous carbohydrate oxidation was significantly different between the GP drink trials at t=90 min (GP: 0.96 ± 0.36 g/min; mixed drink: 1.53 ± 0.48 g/min; p = 0.041, mean ± SD).

Conclusion: The present study found no improvement in 40 km time trial time between an isocaloric GP-only or a GP and fructose drink, and no differences in any of the measured variables other than exogenous carbohydrate oxidation at 90 minutes during the pre-time trial steady state ride.

Keywords: multiple carbohydrate, cycling, endurance, glucose, fructose