Title: PHYSIOLOGICAL AND PERFORMANCE RESPONSES OF FEMALE ENDURANCE CYCLISTS TO SUPPLEMENTATION WITH MEDIUM-CHAIN TRIGLYCERIDES AND CARBOHYDRATE
Abstract: 459 Van Zyl et al. (JAP, 1996) reported that male cyclists supplemented with medium chain triglycerides (MCT) and carbohydrate (CHO) had a decrease in the rate of muscle glycogen oxidation, a 10% contribution of MCT oxidation to the total energy production, and an improvement in cycling time-trial performance. Considering the reported gender differences in fat and CHO metabolism, and also the complete absence of studies evaluating the effect of MCT supplementation in females, it was the purpose of this study to compare the physiological and performance responses of female endurance cyclists to supplementation with either a 10% CHO solution (C) or a combination of CHO (10%) and MCT (4.3%) solution (C-MCT). Using a randomized, double-blind crossover design, eight trained females (27 ± 1 yr, VO2max 46.0 ± 1.2 ml·kg−1·min−1) cycled for 120-min at ∼58% VO2max followed by a simulated 10-km time trial. Prior to each of the two trials, diet was controlled and 5-min prior to each trial subjects ingested 400-ml of either the C or C-MCT solution. During the 2-h ride, 100-ml of the assigned solution was consumed every 10-min. VO2, RER, and HR were recorded every 30-min and RPE, plasma lactate, and plasma glucose were recorded every 20-min during the 120-min of steady state. 10-km time was recorded as the performance measure. As expected, significant within-group time effects were observed for RPE, HR, and RER; however, there were no significant between-group differences (P>0.05) at any steady-state measurement point or during the cycling time trial (C, 20.50 ± 0.59, C-MCT, 20.46 ±0.67 min) (p=0.97). These results suggest that C-MCT supplementation does not alter steady-state substrate utilization or 10-km cycling performance in trained female cyclists. Medium chain triglycerides provided by Mead Johnson Nutritionals