CARBOHYDRATE-LOADING DIETS IN WOMEN CYCLISTS

Abstract

880 The effects of a high-carbohydrate diet (CD) in female athletes are unclear. Therefore, in six well-trained women, we compared the effects of CD vs. habitual diets (HD) on muscle glycogen and on cycling performance. On three occasions-a familiarization trial followed 1-2 wk later by two experimental trials-the subjects completed 6 × 15 min intervals of cycling (12 min at 72% VO2peak, 1-min at maximal effort, and 2 min at 50% VO2peak) followed by a time trial (TT) 15 min later. The women consumed HD (7-8 g carbohydrate/kg fat-free mass) for 3.5 d before the second trial, followed by 3.5 d of CD (9-10 g carbohydrate/kg fat-free mass) prior to the third 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), and this effect occurred in each of the six subjects. Concentrations of blood lactate (CD: 6.0 ± 0.6; HD: 5.6 ± 0.5 mM) and glucose (CD: 5.40 ± 0.27; HD: 5.28±0.24 mM) were similar for both diets during the 90 min rides, but post-TT blood lactate was greater after CD (10.6 ± 0.77 mM) compared to HD (7.22 ± 0.75 mM) (P < 0.005). Mean time for the TT was not significantly different between diets (CD: 12.55 ± 0.5; HD: 12.73 ± 0.6 min). Thus, female cyclists can increase their muscle glycogen stores after a carbohydrate-loading diet, even when their habitual diets contain rather large amounts of carbohydrate. However, we found no evidence of a dietary effect on performance of a cycling time trial. Supported by a Student Research Grant from The Gatorade Sports Science Institute