We studied the effects of different CHO supplements on exercise metabolism (1 hr at 75% ) and performance (fatigue time at 85% ) in 8 male endurance athletes Four treatments were administered in a randomized, double-blind fashion: Trial A = 3-day pretest, postexercise supplementation (177 kcal [81% carbohydrate, 19% protein] consumed < 10 min after exercise) + 600 ml 8% glucose polymers/ fructose 1 hr pretesting + 600 ml 8% glucose polymers/glucose during testing; Trial B = placebo during 3-day pretest + remainder same as Trial A; Trial C = placebo at all time points; and Trial D = same as Trial B with 8% glucose 1 hr before the test as well as during the test. Time to fatigue at 85% (Í24%) and total CHO oxidation were greater for A versus C (p < .05). Plasma glucose concentration was higher for A and B versus C, while increases in plasma potassium concentration were attenuated for A versus C (both p < .05). None of the supplements had differential effects upon hematocrit, plasma sodium [Na+] and lactate, , or rating of perceived exertion during exercise. Three-day preexercise protein + carbohydrate supplements followed by 1-hr pre- and during-exercise mixed carbohydrate supplements increased time to fatigue and carbohydrate oxidation and attenuated rises in plasma [K+] com pared to placebo.
M. Tarnopolsky is with the Departments of Physical Medicine and Rehabilitation and Kinesiology, Room 201B, Ivor Wynne Center, McMaster University, Hamilton, ON, Canada L8S 4K1. K. Dyson and J.D. MacDougall are with the Department of Kinesiology, and S.A. Atkinson and C. Cupido are with the Department of Pediatfics, McMaster University.