Cole, M., Coleman, D. A., & Wiles, J. D. (2012). The influence of nutritional interventions on the measurement of gross efficiency during cycling. Presentation 2364 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

This study determined whether manipulation of nutritional intake before, during, and after cycling exercise could influence subsequent gross-efficiency measurement. Cyclists (N = 36) were split into three groups and undertook one of three studies. All studies involved repeated 2-hour cycling tests at submaximal exercise intensity (60% of Power at VO2max) in a randomized, crossover design. During Study A, carbohydrate intake was manipulated in the three days preceding cycling trials. Ss consumed isocaloric diets (~4000 kcal) that contained a high (70%), moderate (45%), or low (20%) proportion of carbohydrate, with the remaining proportions derived from fat and protein (10%) intake. For Study B, cyclists consumed a standard 3-day pre-exercise diet and conducted four exercise tests where they consumed either water (600 ml/hour), carbohydrate (36 g/hour), caffeine (5 mg/kg), or both carbohydrate and caffeine in combination during the test. During Study C, cyclists undertook four exercise trials. Following a standard 3-day pre-exercise diet, Ss completed the first two tests on consecutive days and consumed either a high- or a low-carbohydrate diet (identical to study A) in the twenty-four hours between tests. A week later, this was repeated with the alternative diet ingested in the recovery between trials. During all tests, expired air was measured at 30-minute intervals in order to calculate gross efficiency

In Study A, gross efficiency was significantly greater following the high- carbohydrate diet than the moderate-carbohydrate diet. In Study B, the decline in gross efficiency over time was significantly attenuated after the ingestion of carbohydrate. In Study C, dietary intervention did not alter gross efficiency.

Implication. Significant differences in gross efficiency were obtained following the alteration of nutritional intake in the three days preceding and during exercise. This suggests that nutritional intake should be carefully controlled and monitored to ensure the validity of gross efficiency measurements.

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