Harger, S. G., McClaughry, A. E., Gaskill, S. E., & Ruby, B. C. (2006). Effects of carbohydrate supplementation in men and women during long duration exercise. Medicine and Science in Sports and Exercise, 38(5), Supplement abstract 1397.

This study evaluated the effects of CHO supplementation on whole body and muscle substrate utilization during prolonged, discontinuous exercise in recreationally trained males (N = 7) and females (N = 6). Ss performed a graduated exercise protocol on a treadmill and electronically braked cycle ergometer to determine ventilatory threshold (VT) and VO2peak. In a double blind, random crossover design, Ss received either a CHO [20% maltodextrin (0.6g/kg FFM/hr)] or flavored placebo drink each hour. Treadmill exercise was performed at 44±4% VO2peak, and 71±3% ventilatory threshold. Cycle ergometer exercise was performed at 42±1% VO2peak, and 72±4% ventilatory threshold. Hourly exercise included nine minutes on an upper body ergometer, 19 minutes on the cycle ergometer, and 20 minutes on the treadmill, followed by a 10-minute rest and feeding period. A standardized breakfast and lunch (5 g/kg BW CHO, and 1.2 g/kg BW PRO) were provided for both trials. Muscle biopsies of the vastus lateralis were performed pre- and post-exercise, and expired gases were collected every other hour during the treadmill segment of the trial. Blood glucose (BG) was measured continuously using an indwelling glucose sensor, and total urine void was collected.

Using a three-way ANOVA (gender*trial*time) there was no significant interaction in whole body and muscle substrate utilization. A main effect was seen for time in CHO oxidation, fat oxidation, and blood glucose. A main effect was also demonstrated for trial in muscle glycogenolysis rate.

Implication. Ingestion of CHO during long-duration, low-intensity exercise appears to have no gender specific effect on whole body substrate utilization. Although CHO ingestion decreases muscle glycogenolysis there is no gender specific effect.

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