Palmer, G. S., Backx, K., & van Someren, K. A. (2003). The importance of high dietary carbohydrate intake during repeated days cycling performance. Medicine and Science in Sports and Exercise, 35(5), Supplement abstract 1659.

Male cyclists (N = 5) completed two laboratory-based three-day simulated stage races consisting of: Day 1 - a 30-minute self-paced time trial in the afternoon; Day 2 - 150-minute variable intensity effort followed by a 30-minute time trial in the morning and a 60-minute time trial in the afternoon; and Day 3 - 150-minute variable effort followed by a 30-minute time trial in the morning. Experiences were 7-14 days apart. Before all rides, Ss received 300 ml of a 6.4% carbohydrate beverage and during time trials water was freely available. In one trial, Ss received moderate carbohydrate (6.6 g/kg) and in the other, high carbohydrate (10.2 g/kg).

Despite Ss being well-trained and the exercise protocol replicating an actual event, only three of the five Ss were able to complete the time trial on day three when using moderate carbohydrate. As the trial progressed, distance covered in the 30-minute efforts fell, average power declined, and heart rate was suppressed in the moderate carbohydrate condition.

Implication. In very high-demand repetitive competitions, a diet rich in carbohydrate is needed to preserve performance. Moderate intake carbohydrate diets may be insufficient to sustain performance whereas high carbohydrate diets are likely to be sufficient.

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