Oxidation of Solid versus Liquid CHO Sources during Exercise


Medicine & Science in Sports & Exercise:
doi: 10.1249/MSS.0b013e3181e0efc9
Basic Sciences

The ingestion of CHO solutions has been shown to increase CHO oxidation and improve endurance performance. However, most studies have investigated CHO in solution, and sporting practice includes ingestion of CHO in solid (e.g., energy bars) as well as in liquid form. It remains unknown whether CHO in solid form is as effectively oxidized as CHO in solution.

Purpose: To investigate exogenous CHO oxidation from CHO provided in either solid (BAR) or solution (DRINK) form during cycling.

Methods: Eight well-trained subjects (age = 31 ± 7 yr, mass = 73 ± 5 kg, height = 1.79 ± 0.05 m, V˙O2max = 69 ± 6 mL·kg−1·min−1) cycled at 58% ± 4% V˙O2max for 180 min while receiving one of the following three treatments in randomized order: BAR plus water, DRINK, or water. The BAR and DRINK was delivered glucose + fructose (GLU + FRC) in a ratio of 2:1 at a rate of 1.55 g·min−1, and fluid intake was matched between treatments.

Results: During the final 2 h of exercise, overall mean exogenous CHO oxidation rate was −0.11 g·min−1 lower in BAR (95% confidence interval = −0.27 to 0.05 g·min−1, P = 0.19) relative to DRINK, whereas exogenous CHO oxidation rates were 15% lower in BAR (P < 0.05) at 120, 135, and 150 min of exercise. Peak exogenous CHO oxidation rates were high in both conditions (BAR 1.25 ± 0.15 g·min−1 and DRINK 1.34 ± 0.27 g·min−1) but were not significantly different (P = 0.36) between treatments (mean difference = −0.9 g·min−1, 95% confidence interval = −0.32 to 0.13 g·min−1).

Conclusions: The present study demonstrates that a GLU + FRC mix administered as a solid BAR during cycling can lead to high mean and peak exogenous CHO oxidation rates (>1 g·min−1). The GLU + FRC mix ingested in the form of a solid BAR resulted in similar mean and peak exogenous CHO oxidation rates and showed similar oxidation efficiencies as a DRINK. These findings suggest that CHO from a solid BAR is effectively oxidized during exercise and can be a practical form of supplementation alongside other forms of CHO.

Author Information

1School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, England, UNITED KINGDOM; and 2Nestlé Research Center, Lausanne, SWITZERLAND

Address for correspondence: Asker E. Jeukendrup, Ph.D., School of Sport and Exercise Sciences, University of Birmingham, Birmingham, England B15 2TT, United Kingdom; E-mail: A.E.Jeukendrup@bham.ac.uk.

Submitted for publication April 2009.

Accepted for publication March 2010.

©2010The American College of Sports Medicine