King, R. F., O'Hara, J. P., & Carlton, C. B. (2006). Effects of pre-exercise ingestion of galactose, glucose, and fructose on endurance performance. Medicine and Science in Sports and Exercise, 38(5), Supplement abstract 736.

This study examined the effects of pre-exercise ingestion of galactose, glucose, and fructose on cycling endurance performance. Well trained male cyclists and/or triathletes (N = 10) completed five intermittent tests on an air braked cycle ergometer after an overnight fast of at least 12 hours. Each trial started 30 minutes post-ingestion of 1 litre of fluid. The four different isotonic formulations contained 4% carbohydrate(s) at w/v [galactose, glucose, galactose/glucose/fructose, galactose/glucose/fructose containing caffeine]. A placebo drink was used as a control. All treatment drinks contained the same electrolyte composition and were spaced weekly. The protocol comprised: (1) 20 minutes of progressive incremental exercise, where the power output was increased by 5% Wmax every 5 minutes from 70% Wmax to 85% Wmax; (2) ten 90-second bursts at 90% Wmax, separated by 180 seconds at 55% Wmax; and (3) 90% Wmax until volitional exhaustion.

Time to exhaustion was significantly different between the five formulations. Galactose produced 17.3% (10.2 minutes), 9.4% (5.92 minutes), 7.4% (4.74 minutes) and 7.3% (4.69 minutes) longer times to exhaustion than glucose, galactose/glucose/fructose, galactose/glucose/fructose containing caffeine, and placebo, respectively. Seven of ten Ss performed the longest time to exhaustion whilst on galactose. All Ss performed longer times to exhaustion whilst on galactose in comparison to glucose.

Implication. A 4% galactose sports drink provided an ecologically significant ergogenic benefit to endurance performance in terms of time to exhaustion compared to a pure glucose sports drink, blended-carbohydrate sports drinks, one of which included caffeine, and a placebo. Glucose ranked as the worst formulation even in comparison to a placebo.

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