Nutritional and fluid intake in a 100-km ultramarathon.

The fluid and food intakes of 7 male participants in a 100-km ultramarathon were recorded. The mean exercise time was 10 hr 29 min. Nutrient analysis revealed a mean intrarace energy intake of 4,233 kJ, with 88.6% derived from carbohydrate, 6.7% from fat, and 4.7% from protein. Fluid intake varied widely, 3.3-11.1 L, with a mean of 5.7 L. The mean decrease in plasma volume at 100 km was 7.3%, accompanied by an estimated mean sweat rate of 0.86 L.hr-1. Blood glucose concentrations remained normal during the event, and free fatty acids and glycerol were elevated both during and at the conclusion of the event. No significant correlations were found between absolute amounts and rates of ingestion of carbohydrate and/or fluid and race performance.