NUTRITIONAL INTAKE ALTERS TEST RESPONSES
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 in cyclists (N = 36). Ss were divided into three groups and participated in one of three studies. All studies involved repeated 2-hour cycling tests at submaximal exercise intensity (60% of Power at VO2max). During study A, carbohydrate (CHO) intake was manipulated in the three days preceding cycling trials. Ss consumed isocaloric diets (~4000kcal) 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 water (600ml/h), CHO (36g/h), caffeine (5mg/kg), or both CHO and caffeine in combination during the test. During study C, Ss 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 24-hours between tests. A week later, this was repeated with the alternative diet ingested in the recovery period 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-CHO diet than the Moderate-CHO diet. In study B, decline in gross-efficiency over time was significantly attenuated after the ingestion of CHO. In study C, dietary intervention did not alter gross-efficiency.
Implication. Significant differences in gross-efficiency were obtained following alteration of nutritional intake in the 3-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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