Medicine & Science in Sports & Exercise:
F-22C Free Communication/Slide Carbohydrate and Performance
Widzer, M O.1; Boon, N1; Lichtenberg, L C.1; Ivy, J L. FACSM1
1Department of Kinesiology, University of Texas, Austin, TX
Previous research has demonstrated that a subsequent bout of exercise performed on the same day results in an exaggerated stress hormone response and cytokine production compared with a single exercise bout and is strongly mediated by carbohydrate availability.
This study was conducted to determine the effects of carbohydrate supplementation during a previous exercise bout and 2 h of recovery on fuel utilization, stress response and performance during a subsequent exercise bout.
After an overnight fast, 8 trained male cyclists (75.1±3.2 kg, 60.0±1.9 ml/kg/min) completed 2 exercise trials (EX1 and EX2) in random order. EX1 consisted of 90 min of cycle ergometry at sub-lactate threshold (218.9±8.4 watts, 2.7±0.1 l/min), followed by a 2 h recovery period. During EX1 and recovery period, subjects received at predetermined times either an 8% carbohydrate supplement (CHO) or placebo (PLA). Subjects then performed a second exercise bout lasting 75 min (EX2), at the same intensity as used in EX1. Immediately following EX2, a 278.7±20.5 KJ time trial was performed. PLA was provided during EX2 to prevent dehydration.
During EX1 and recovery plasma insulin levels were higher during CHO compared to PLA (p < 0.05). However, during EX2 plasma insulin and IL-6 levels were similar between treatments, but plasma free fatty acids, glycerol, cortisol and growth hormone levels were suppressed during CHO (p < 0.05). This plasma profile corresponded with a lower fat and higher carbohydrate oxidation rate during CHO compared to PLA (p < 0.05). Despite differences in substrate utilization between CHO and PLA, no difference in time trial performance was observed.
The availability of carbohydrate during EX1 and recovery will suppress fat utilization, elevate carbohydrate utilization and suppress the rise in several hormones related to stress without a concomitant increase in IL-6. Furthermore, carbohydrate supplementation during EX1 does not enhance performance as assessed by a time trial following EX2.