Research investigating the effects of pre-exercise meals with varying glycemic indices on exercise performance in intermittent sports is scarce. This study determined whether whole foods of low glycemic index (GI) resulted in a metabolic and performance advantage, in comparison to high GI foods, when eaten prior to extended intermittent cardiovascular exercise, such as tournament soccer play. Consenting trained participants (10 males, 4 females, 25.8 ± 7.3 y) completed two simulated soccer tournaments separated by at least seven days. Each testing day included two 90-minute soccer matches separated by a three hour break. Using a randomized cross-over design, low-GI, lentil-based meals (GI~42) or high-GI, potato-based meals (GI~78) matched for caloric value were consumed two hours prior to and then within one hour after the first soccer match. Blood glucose, lactate, insulin, free fatty acids, and respiratory gases were measured throughout the post-prandial and testing periods. Ratings of perceived exertion (RPE) and gastrointestinal symptoms were also recorded. Performance was measured by the distance covered during five one-minute sprints, separated by two minute and thirty second rest intervals, at the end of each match. Peak post-prandial blood glucose was higher (p<0.05) in the high-GI trial (8.9 ± 2.2 molL-1 [SD]) compared to the low GI trial (5.9 ± 1.3 mmolL-1) as was insulin prior to the start of exercise (19.4 ± 2.0 versus 9.2 ¬± 1.3 umolL-1, p<0.05). Blood lactate levels were significantly higher (p<0.05) at the end of the second match during the high-GI trial (6.1 ± 1.2 mmolL-1) compared to the low-GI trial (2.5 ± 0.4 mmolL-1). Breath-by-breath analysis showed lower (p<0.05) carbohydrate oxidation during the low-GI trials compared to the high-GI at the start of the first soccer match (p<0.05). Subjects reported greater feelings of hunger during the high-GI trial versus greater feelings of fullness during the low-GI trial (p<0.05), but RPE during the low-GI (14.1 ± 0.3) was similar to the high-GI meal (14.2 ± 0.3). Sprint distance was not significantly different between treatments (p=0.27). Overall, these findings suggest that lentil-based, low-GI foods are a comparable alternative to traditional high-GI pre-exercise meals, as they result in similar performance outcomes but improved metabolic profiles. Over the long-term, improving metabolic conditions during exercise may be beneficial to the health of athletes.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-09182009-154558 |
| Date | 21 September 2009 |
| Creators | Bennett, Christine Brandy |
| Contributors | Whiting, Susan, Kendall, Cyril, Arnold, Catherine, Zello, Gordon, Chilibeck, Philip |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-09182009-154558/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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