The determination of blood glucose response to various carbohydrate foods may help athletes in their choice of preexercise feedings. This case study documented the postprandial glycemic responses of three male endurance athletes at rest after ingestion of 50-gram portions of three carbohydrate foods: graham crackers, orange juice, and oatmeal. Plasma glucose response differed in each subject for each test food. Two of the three subjects exhibited similar glycemic responses, but not to the same test food. Future studies will clarify the relationship between carbohydrate ingestion and postprandial glucose response.
Marie Dunford and Charlotte Saunders
Yan Burelle, François Péronnet, Denis Massicotte, Guy R. Brisson and Claude Hillaire-Marcel
The oxidation of 13C-labeled glucose and fructose ingested as a preexercise meal between 180 and 90 min before exercise was measured on 6 subjects when either a placebo or sucrose was ingested during the exercise period. Labeled hexose oxidation, which occurred mainly during the first hour of exercise, was not significantly modified when sucrose was ingested, but exogenous glucose oxidation was significantly higher than exogenous fructose oxidation in both situations. The results suggest that the absorption rate of exogenous hexoses was high when exercise was initiated but diminished thereafter, and that glucose and fructose released from sucrose ingested during exercise did not compete with glucose or fructose ingested before exercise for intestinal absorption, for conversion into glucose in the liver (for fructose), or for uptake and oxidation of glucose in peripheral tissues. However, as already shown, in terms of availability for oxidation of carbohydrates provided by the preexercise meal, glucose should be favored over fructose.
Stephen A. Mears, Kathryn Dickinson, Kurt Bergin-Taylor, Reagan Dee, Jack Kay and Lewis J. James
been observed. 5 The preexercise feeding recommendation for exercise greater than 60 minutes is to ingest carbohydrate in the 1 to 4 hours before exercise. 7 The 90-minute preexercise breakfast ingestion in the current study found similar results to Galloway and colleagues 20 when ingestion occurred
Rachel B. Parks, Hector F. Angus, Douglas S. King and Rick L. Sharp
carbohydrate type, amount or timing, and method of performance assessment have likely contributed to the differing results obtained in studies of preexercise feedings ( Jeukendrup & Killer, 2010 ). In a previous study where cyclists worked at a slightly higher intensity (∼75% W max ) for ∼40 min, the outcome