Effects of moderate dietary manipulation on intermittent exercise performance and metabolism in women

The aim of the current study was to examine the effect of a moderate alteration in pre-exercise diet composition on the performance of, and metabolic response to, intermittent treadmill exercise in a group of normally menstruating females. Eight recreationally active women performed two intermittent, incremental exercise trials, one preceded by 2 days of a high [61 (1)%] carbohydrate (CHO) diet and the other by 2 days of a low [31 (1)%] CHO diet. Oxygen uptake (VO2) was measured during, and blood samples were obtained immediately after, each bout for the determination of blood lactate, glucose, glycerol, plasma free fatty acids and plasma ammonia. Performance, as assessed by time to exhaustion in the final bout, was found to be similar whether preceded by a high- or low-CHO diet [median (range): 28.0 (18–54) s, 29 (18–54) s, respectively]. No significant between trial differences were found in VO2, heart rate, or any of the blood metabolites. The results of the current study indicate that moderate alterations of pre-exercise diet do not affect intermittent, high-intensity exercise performance in women, despite some evidence of an alteration in the pattern of the metabolic response to exercise.