The effects of low and high glycemic index meals on time trial performance

Brown, Laura and Midgley, Adrian and Thomas, Gemma and Thurlow, Shane and McNaughton, Lars R. (2009) The effects of low and high glycemic index meals on time trial performance. International journal of sports physiology and performance., 4 (3). p. 331.

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The aim of this work was to determine whether the consumption of preexercise
high– or low–glycemic index (GI) meals has a beneficial effect on time trial
performance. Methods: Eight male cyclists were provided with either a high-GI or
low-GI meal, providing 1 g·kg−1 body mass of carbohydrate, 45 min before performing
a 40-km time trial on a Velotron cyclePro. Results: Time trial performance was
significantly improved in the low-GI trial (92.5 ± 5.2 min) compared with the high-GI
trial (95.6 ± 6.0 min) (P = .009). Blood glucose concentrations at the point of exhaustion
were significantly higher in the low-GI trial (5.2± 0.6 mmol·L−1) compared with
the high-GI trial (4.7 ± 0.7 mmol·L−1) (P = .001). There was no significant difference
in estimated carbohydrate oxidation data between the low-GI (2.51 ± 1.74 g·min−1)
and high-GI (2.18 ± 1.53 g·min−1) meals (P = .195). No significant difference in estimated
fat oxidation was observed between the low-GI (0.15 ± 0.15 g·min−1) and
high-GI (0.29 ± 0.18 g·min−1) diets (P = .83). Conclusions: The improvement in time
trial performance for the low-GI trial may be associated with an increased availability
of glucose to the working muscles, contributing additional carbohydrate for oxidation
and possibly sparing limited muscle and liver glycogen stores.

Item Type: Article
Status: Published
Subjects: G Geography. Anthropology. Recreation > GV Recreation Leisure
Q Science > QP Physiology
School/Department: School of Health Sciences
URI: http://ray.yorksj.ac.uk/id/eprint/375

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