Pre-exercise carbohydrate ingestion : effect of the glycemic index on endurance exercise performance

Sparks, Matthew J., Selig, Steve E. and Febbraio, Mark A. 1998, Pre-exercise carbohydrate ingestion : effect of the glycemic index on endurance exercise performance, Medicine and science in sports and exercise, vol. 30, no. 6, pp. 844-849.

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Title Pre-exercise carbohydrate ingestion : effect of the glycemic index on endurance exercise performance
Author(s) Sparks, Matthew J.
Selig, Steve E.
Febbraio, Mark A.
Journal name Medicine and science in sports and exercise
Volume number 30
Issue number 6
Start page 844
End page 849
Publisher American College of Sports Medicine
Place of publication Madison, Wis.
Publication date 1998-06
ISSN 0195-9131
1530-0315
Summary Purpose: This study aimed to examine the effect of glycemic index of pre-exercise carbohydrate (CHO) ingestion on exercise metabolism and performance.

Methods: Eight endurance trained men ingested a high glycemic index (HGI), low glycemic index (LGI), or a placebo (CON) meal 45 min before exercise and then cycled for 50 min at 67% V·O2max. Subjects subsequently performed a 15-min self-paced performance ride in which total work (kJ) was recorded.

Results: Plasma glucose concentrations were higher (P < 0.01) after ingestion in HGI compared with LGI and CON (7.53 ± 0.64 vs 5.55 ± 0.21 and 4.65 ± 0.14 mmol·L-1 for HGI, LGI, and CON, respectively, 30 min postprandial; mean ± SE) but declined at the onset of exercise and were lower (P < 0.01) compared with LGI and CON (4.03 ± 0.31 vs 4.64 ± 0.24 and 5.09 ± 0.16 mmol·L-1 for HGI, LGI, and CON respectively; mean ± SE) at 10 min of exercise. Plasma glucose remained depressed (P < 0.01) until 30 min into exercise in HGI compared with other trials. Plasma insulin concentrations were higher (P < 0.01) following ingestion during rest and exercise in HGI compared with LGI and CON. Plasma FFA concentrations were lower (P < 0.05) following ingestion in HGI and LGI compared with CON and higher (P < 0.05) in LGI compared with HGI at the start and end of exercise. RER and CHO oxidation was higher (P < 0.01) in HGI compared with LGI and CON during submaximal exercise. There were no differences in work output during the performance cycle.


Conclusions: These data indicate that pre-exercise CHO feedings with varying glycemic indexes do not affect exercise performance following short term submaximal exercise despite alterations in metabolism.
Language eng
Field of Research 119999 Medical and Health Sciences not elsewhere classified
Socio Economic Objective 970111 Expanding Knowledge in the Medical and Health Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©1998, Williams & Wilkins
Persistent URL http://hdl.handle.net/10536/DRO/DU:30033446

Document type: Journal Article
Collection: School of Exercise and Nutrition Sciences
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