Submitted to: International Journal of Sport Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2001
Publication Date: N/A
Interpretive Summary: The purpose of this investigation was to determine the effect of carbohydrate-loading diets on muscle carbohydrate stores and exercise performance in female cyclists during the follicular phase of the menstrual cycle. 6 female cyclists consumed their habitual diets for 3.5 days, then were provided with a diet that was high in carbohydrate for 3.5 days. Exercise performance following each of the diets was determined. The carbohydrate-loading diet increased muscle carbohydrate stores, but did not improve exercise performance. This paper was intended to benefit competitive female endurance athletes.
Technical Abstract: The effects of employing a high-carbohydrate diet (carbohydrate-loading) to increase glycogen storage in skeletal muscle are not well established in female athletes. On four occasions two familiarization trials and two experimental trials six well-trained female subjects completed 6 x 15-min continuous intervals of cycling (12 min at 72% VO2max, 1 min at maximal effort, and 2 min at 50% VO2max) followed by a time trial 15 min later. The women consumed their habitual diets (HD; 6-7 g carbohydrate/kg lean body mass) for 3 d after the second familiarization trial and before the first experimental trial. During the 3 d following the first experimental trial, the subjects consumed a high-carbohydrate diet (CD; 9-10 g carbohydrate/kg lean body mass) prior to the second experimental trial. Mean (+/- SEM) pre-exercise muscle glycogen concentrations were greater after CD vs. HD (171.9 +/- 8.7 vs. 131.4 +/- 10.3 mmol/kg wet weight, P < 0.003). Although four of the six subjects improved their time-trial performance after CD, mean performance for the time trial was not significantly different between diets (HD: 763.9 +/- 35.6; CD: 752.9 +/- 30.1 sec). Thus, female cyclists can increase their muscle glycogen stores after a carbohydrate-loading diet during the follicular phase of the menstrual cycle, but we found no compelling evidence of a dietary effect on performance of a cycling time trial performed after 90 min of moderate-intensity exercise.