Purpose: To determine whether combined ingestion of maltodextrin and fructose during 150 min of cycling exercise would lead to exogenous carbohydrate oxidation rates higher than 1.1 g·min−1.
Methods: Eight trained cyclists (V̇O2max: 64.1 ± 3.1 mL·kg·min−1) performed three exercise trials in a random order. Each trial consisted of 150 min cycling at 55% maximum power output (64.2 ± 3.5% V̇O2max) while subjects received a solution providing either 1.8 g·min−1 of maltodextrin (MD), 1.2 g·min−1 of maltodextrin + 0.6 g·min−1 of fructose (MD+F), or plain water. To quantify exogenous carbohydrate oxidation, corn-derived MD and F were used, which have a high natural abundance of 13C.
Results: Peak exogenous carbohydrate oxidation (last 30 min of exercise) rates were ∼40% higher with combined MD+F ingestion compared with MD only ingestion (1.50 ± 0.07 and 1.06 ± 0.08 g·min−1, respectively, P < 0.05). Furthermore, the average exogenous carbohydrate oxidation rate during the last 90 min of exercise was higher with combined MD+F ingestion compared with MD alone (1.38 ± 0.06 and 0.96 ± 0.07 g·min−1, respectively, P < 0.05).
Conclusions: The present study demonstrates that with ingestion of large amounts of maltodextrin and fructose during cycling exercise, exogenous carbohydrate oxidation can reach peak values of ∼1.5 g·min−1, and this is markedly higher than oxidation rates from ingesting maltodextrin alone.
1School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, UNITED KINGDOM; and2Institute of Food, Nutrition, and Human Health, Massey University, Wellington, NEW ZEALAND
Address for correspondence: Dr. A. E. Jeukendrup, School of Sport and Exercise Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom; E-mail A.E.Jeukendrup@bham.ac.uk.
Submitted for publication April 2004.
Accepted for publication October 2004.
The authors do not have a professional relationship with companies or manufacturers who may benefit from the results of the present study. The results of the study do not constitute endorsement of the product by the authors or ACSM.
This research was supported by a grant from the International Life Sciences Institute (U.S.). David S. Rowlands was supported by a grant from Massey University MURF (NZ) (Grant PR568099) and by the Maurice and Phyllis Paykel Trust (NZ).