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The Effect of Pre-Exercise Galactose and Glucose Ingestion on High-Intensity Endurance Cycling

O'Hara, John P.1; Carroll, Sean2; Cooke, Carlton B.1; King, Roderick F.G.J.1

The Journal of Strength & Conditioning Research: August 2014 - Volume 28 - Issue 8 - p 2145–2153
doi: 10.1519/JSC.0000000000000372
Original Research

O'Hara, JP, Carroll, S, Cooke, CB, and King, RFGJ. The effect of pre-exercise galactose and glucose ingestion on high-intensity endurance cycling. J Strength Cond Res 28(8): 2145–2153, 2014—This study evaluated the effects of the pre-exercise (30 minutes) ingestion of galactose (Gal) or glucose (Glu) on endurance capacity as well as glycemic and insulinemic responses. Ten trained male cyclists completed 3 randomized high-intensity cycling endurance tests. Thirty minutes before each trial, cyclists ingested 1 L of either 40 g of glucose, 40 g of galactose, or a placebo in a double-blind manner. The protocol comprised 20 minutes of progressive incremental exercise (70–85% maximal power output [Wmax]); ten 90-second bouts at 90% Wmax, separated by 180 seconds at 55% Wmax; and 90% Wmax until exhaustion. Blood samples were drawn throughout the protocol. Times to exhaustion were longer with Gal (68.7 ± 10.2 minutes, p = 0.005) compared with Glu (58.5 ± 24.9 minutes), with neither being different to placebo (63.9 ± 16.2 minutes). Twenty-eight minutes after Glu consumption, plasma glucose and serum insulin concentrations were higher than with Gal and placebo (p < 0.001). After the initial 20 minutes of exercise, plasma glucose concentrations increased to a relative hyperglycemia during the Gal and placebo, compared with Glu condition. Higher plasma glucose concentrations during exercise, and the attenuated serum insulin response at rest, may explain the significantly longer times to exhaustion produced by Gal compared with Glu. However, neither carbohydrate treatment produced significantly longer times to exhaustion than placebo, suggesting that the pre-exercise ingestion of galactose and glucose alone is not sufficient to support this type of endurance performance.

1Research Institute for Sport, Physical Activity and Leisure, Leeds Metropolitan University, Leeds, United Kingdom; and

2Department of Sport, Health and Exercise Science, University of Hull, Hull, United Kingdom

Address correspondence to Dr. John P. O'Hara,

Copyright © 2014 by the National Strength & Conditioning Association.