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Davidson, C J.1; Zderic, T W.1; Schenk, S1; Walker, S L.1; Coyle, E F. FACSM1

Medicine & Science in Sports & Exercise: May 2003 - Volume 35 - Issue 5 - p S298
F-22C Free Communication/Slide Carbohydrate and Performance

1The Human Performance Laboratory, The University of Texas, Austin, Texas 78712

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This study quantified the effect of three breakfast cereals on maximal neuromuscular cycling power during the 3h postprandial period.

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Six endurance-trained cyclists [mean±SD, age:29.3±3.5y; VO2 peak:4.36±0.4L/min, peak power: 15.3±2.1 W/kg] participated. Subjects consumed one of five meals: All Bran [AB][Glycemic Index=53.8], Oatmeal [OT][GI=77.1], Cornflakes [CF][GI=112.2], a glucose solution [GLU][GI=100], or a placebo [PLA]. The three cereals and the glucose solution each contained 50g of available carbohydrate. Maximal neuromuscular power was tested, using inertial load ergometry, at three time points [30, 90 and 150 min] after the meal.

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At 30 and 60 min after the feedings, plasma glucose concentration was increased significantly from PLA in all meals [AB, OT, CF, GLU; P < 0.05]. By 90 min into the experiment, plasma glucose concentration in only the CF treatment was still significantly elevated above PLA. Thereafter [120, 150 and 180 min], plasma glucose for all the treatment groups was not different from initial values. We found no main effect for treatment in maximal neuromuscular cycling power with values averaged for the 3 time points [AB:1077±40; OT:1078±43; CF:1076±40; GLU:1084±43; PLA:1090±41 W]. However, there was a main effect for time, with power increasing significantly across the three time points [30min:1065±30 <90min:1083±33; 150min:1095±32 W, P < 0.05]. Additionally, there was a significant difference between the power produced in GLU between time points 30 min [1050±78 W] and 90 min [1105±81 W, P < 0.05].

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The increases in power over the 3 h period after a breakfast meal or placebo were independent of the metabolic changes presented by meals of differing glycemic response. Also, feeding a pre-exercise meal or placebo lowered maximal cycling power at 30 min compared to 90 and 150 min postprandial. Finally, a pre-exercise glucose feeding reduced maximal neuromuscular power at 30 min postprandial compared to that at 90 min. Supported by the Quaker Oats Company.

©2003The American College of Sports Medicine