The Effect of Pre-exercise Glucose Ingestion on Performance during Prolonged Swimming

in International Journal of Sport Nutrition and Exercise Metabolism
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The purpose of this study was to determine if pre-exercise glucose ingestion would improve distance swimming performance. Additionally, pre-exercise glucose was provided at 2 different feeding intervals to investigate the affects of the timing of administration. Ten male triathletes (X¯±SD: age, 29.5 ± 5.0 years; V̇O2peak, 48.8 ± 3.2 ml · kg’1 · min’) swam 4000 m on 3 occasions following the consumption of either a 10% glucose solution 5 min prior to exercise (G5), a 10% glucose solution 35 min prior to exercise (G35), or a similar volume of placebo (PL). Despite a significant difference (p < ,01) in blood glucose concentration prior to exercise (X¯±SD in mmol · L ’: G" 8.4 ± 1.1 vs. G5 5.2 ± 0.5 or PL 5.3 ± 0.4), no significant differences were observed in total time (X¯±SD in minutes: G* 70.7 ± 7.6, Gs 70.1 ± 7.6. PL 71.9 ± 8.4). post-exercise blood glucose (X¯±SD inmmol · L−1: G35 5.1 ± 1.1, G5 5.1 ± 0.9, PL 5.3 ± 0.4), and average heart rate (X¯±SD in bpnv.G" 155.8±10.8, G5 153.6±12.6. PL 152.0± 12.5; p > .05). While not reaching statistical significance, glucose feedings did result in improved individual performance times, ranging from 24 s to 5 min in 8 of the 10 subjects compared to the placebo. These results were found despite significant differences in blood glucose between trials immediately prior to exercise.

The authors are with the J.M. Buchanan Exercise Science Laboratory in the School of Human Kinetics at the University of British Columbia, Vancouver, B.C., Canada V6T 1Z1.