Ready, S. L., Siefert, J. G., & Burke, E. (1999). The effect of two sports drink formulations on muscle stress and performance. Medicine and Science in Sports and Exercise, 31(5), Supplement abstract 458.

Creatine kinase (CK) level is frequently used as an indication of muscle damage and stress. The leakage is believed to result from cell membrane damage. Two formulations were compared for their effects on post-exercise muscle stress and performance time in a moderate-intensity duathlon. College males and females (N = 10) ingested a 15% CHO/protein/electrolyte beverage (CP - CHO:protein 4:1) or a 6% CHO/electrolyte beverage (CE). Ss completed a 45-min run, rested for 10-min, cycled for 90-min, and the performed a 90kJ time trial. The drinks (360 ml) were ingested during the 10-min rest.

The time trial was enhanced in 7 of 10 Ss by an average of 27 seconds, but this difference was not statistically significant. Glucose was significantly increased in the CP group. No differences were observed for lactate, heart rate, VO2, or RPE. In the CP group, there was a significant reduction in the 24-hr post-exercise CK level.

Implication. A CHO-protein drink might reduce post exercise muscle stress.

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