Effect of carbohydrate feedings on muscle glycogen utilization and exercise performance

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Abstract
Ten men were studied during 4 h of cycling to determine the effect of solid carbohydrate (CHO) feedings on muscle glycogen utilization and exercise performance. In the experimental trial (E) the subjects ingested 43 g of sucrose in solid form along with 400 ml of water at 0, 1, 2 and 3 h of exercise. During the control trial (C) they received 400 ml of an artificially sweetened drink without solid CHO. No differences in .ovrhdot.VO2 heart rate, or total energy expenditure were observed between trials; however, respiratory exchange ratios were significantly (P < 0.05) higher during E. Blood glucose was significantly (P < 0.05) elevated 20 min post-feeding in E; by 50 min no differences were observed between trials until 230 min (E = 4.5 .+-. 0.2 mmol .cntdot. l-1 vs. C = 3.9 .+-. 0.2, .hivin.X .+-. SE; P < 0.05). Muscle glycogen utilization was significantly (P < 0.05) lower during E (100.7 .+-. 10.2 mmol .cntdot. kg-1 w.w. [wet weight]) than C (126.2 .+-. 5.5). During a sprint (100% .ovrhdot.VO2 max [maximum O2 consumption]) ride to exhaustion at the end of each trial, subjects performed 45% longer when fed CHO (E = 126.8 .+-. 24.7 svs. C = 87.2 .+-. 17.5; P < 0.05). Repeated solid CHO feedings evidently maintain blood glucose levels, reduce muscle glycogen depletion during prolonged exercise and enhance sprint performance at the end of such activity.