CARBOHYDRATE SUPPLEMENTATION ELEVATES BLOOD GLUCOSE BUT NOT PERFORMANCE
Guth, L. M., Hanna, L. E., Lee, J. D., & Mahon, A. D. (2008). The effects of carbohydrate supplementation on fatigue during intermittent cycling. ACSM 55th Annual Meeting Indianapolis. Presentation number 850.
This study examined the effect of carbohydrate supplementation on fatigue in healthy young men (N = 6) during an intermittent cycling protocol. Ss consumed 1.5 g/kg of either a 22% carbohydrate or a placebo beverage 30 minutes before and throughout exercise. The exercise consisted of three 12-minute sets; each set consisted of four 3-minute bouts. Each 3-minute bout involved cycling for 60 seconds at 150 W, a 10-second sprint against 0.05 kg/kg body mass resistance, 50 seconds at 100 W, and 60 seconds of active rest with no resistance.
Mean power decreased across sets in both trial conditionss. There were no significant effects for trials or interactions. Rating of perceived exertion increased over time, but was similar between trials. There was a significant time x trial interaction effect for blood glucose. Blood glucose was higher in the placebo trial after the third set. Within the carbohydrate trial, glucose after each set was lower than the pre-exercise measure, but not significantly different between sets. In the placebo trial, there were no significant differences between sets. Pre-exercise blood lactate concentration was similar for both trials and increased after the first set and remained elevated to the end of the protocol.
Implication. Carbohydrate supplementation elevated blood glucose level but did not affect high-intensity intermittent cycling performance, anaerobic exercise metabolism, or perceived exertion.
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