PRE-EXERCISE CHO FEEDING DOES NOT IMPROVE EXTENDED PERFORMANCE
Gutch, C., Jentjens, R. L., Cale, C., & Jeukendrup, A. E. (2002). The effects of different amounts of pre-exercise carbohydrate feeding on metabolism and cycling performance. Medicine and Science in Sports and Exercise, 34(5), Supplement abstract 1602.
Male cyclists (N = 9) completed four exercise trials in random order. Ss consumed 500 ml of beverage 45 minutes before exercising. Beverages contained 0 gm (placebo), 25 gm, 75 gm, and 200 gm of glucose. The exercise trial was 20 minutes of cycling at 65% of maximal power output followed immediately by a controlled-load time trial.
Plasma insulin concentrations at the start of exercise were significantly higher in the two high doses of glucose than in the low and placebo doses. Plasma glucose fell rapidly in all glucose conditions but remained steady in the placebo condition. No differences in plasma glucose between conditions were observed at any stage of exercising. Hypoglycemia was observed in five Ss in the steady state stage after pre-exercise glucose feeding but not in the placebo condition. There were no differences in time trial performances.
Implication. Pre-exercise carbohydrate feeding does not influence subsequent performance. Some individuals initially respond with hypoglycemia but eventually that dissipates to normality.
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