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Effect of the glycaemic index of a pre-exercise meal on metabolism and cycling time trial performance

Moore, Laura J.S. and Midgley, Adrian W. and Thurlow, Shane and Thomas, Gemma and Mc Naughton, Lars R. (2010) Effect of the glycaemic index of a pre-exercise meal on metabolism and cycling time trial performance. Journal of Science and Medicine in Sport, 13 (1). pp. 182-188.

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Abstract

Objectives

Some athletes train/compete multiple times in a single day and rapid restoration of muscle and hepatic glycogen stores is therefore important for athletic performance.

Design

Randomised, counterbalanced, crossover, single blinded study investigated the effects of low/high glycaemic index (GI) meals on the physiological responses to a 3-h recovery period and subsequent 5-km cycling time trial (TT).

Methods

Seven male cyclists completed glycogen-depleting exercise followed by a 3-h recovery period, when participants consumed either a high or low GI meal providing 2 g kg−1 BM of carbohydrate. Participants then performed a 5-km cycling TT. Blood samples were analysed for glucose insulin, free fatty acid (FFA) and triglyceride.

Results

There was no significant difference between the median (IQR) cycling TT time of 8.5 (3.0) min in the LGI condition and 8.4 (1.8) min in the HGI condition (p = 0.45). Serum insulin was significantly higher in the HGI condition throughout the 3-h recovery period (p = 0.025), FFA concentrations were higher in the HGI condition only at 30 min into recovery (p = 0.008). The respiratory exchange ratio (p = 0.028) and carbohydrate oxidation rate (p = 0.015) increased over time in the HGI condition, whereas the rate of fat oxidation demonstrated the opposite response (p = 0.001). No significant differences between conditions were observed for any physiological variables at the end of the 5-km TT.

Conclusions

Although the GI of the two meals indicated important metabolic differences during the recovery period, there was no evidence suggesting these differences influenced subsequent 5-km TT performance.

Item Type: Article
Status: Published
DOI: 10.1016/j.jsams.2008.11.006
Subjects: G Geography. Anthropology. Recreation > GV Recreation Leisure
R Medicine > RC Internal medicine > RC1200 Sports Medicine
School/Department: School of Health Sciences
URI: http://ray.yorksj.ac.uk/id/eprint/512

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