Dietary carbohydrate, muscle glycogen content, and endurance performance in well-trained women

This study examined the ability of well-trained eumenonrheic women to incre ase muscle glycogen content and endurance performance in response to a high -carbohydrate diet (HCD; similar to 78% carbohydrate) compared with a moder ate-carbohydrate diet (MD; similar to 48% carbohydrate) when tested during the luteal phase of the menstrual cycle. Six women cycled to exhaustion at similar to 80% maximal oxygen uptake (VO2max) after each of the randomly as signed diet and exercise-tapering regimens. A biopsy was taken from the vas tus lateralis before and after exercise in each trial. Preexercise muscle g lycogen content was high after the MD (625.2 +/- 50.1 mmol/kg dry muscle) a nd 13% greater after the HCD (709.0 +/- 44.8 mmol/kg dry muscle). Postexerc ise muscle glycogen was low after both trials (MD, 91.4 +/- 34.5; HCD, 80.3 +/- 19.5 mmol/kg dry muscle), and net glycogen utilization during exercise was greater after the HCD. The subjects also cycled longer at similar to 8 0% VO2max after the HCD vs. MD (115:31 +/- 10:47 vs. 106:35 +/- 8:36 min:s, respectively). In conclusion, aerobically trained women increased muscle g lycogen content in response to a high-dietary carbohydrate intake during th e luteal phase of the menstrual cycle, but the magnitude was smaller than p reviously observed in men. The increase in muscle glycogen, and possibly li ver glycogen, after the HCD was associated with increased cycling performan ce to volitional exhaustion at similar to 80% VO2max.