The Effects of Creatine Supplementation on Anaerobic Working Capacity

Anaerobic working capacity (AWC) estimated from the critical power test provides a theoretically and experimentally valid estimate of work capacity associated with muscle energy reserves adenosine triphosphate and phosphocreatine. Creatine monohydrate (CM) supplementation has been shown to increase phosphocreatine stores in skeletal muscle and, in theory, should increase AWC. Therefore, the purpose of this study was to examine the effects of supplementation with CM, CM plus carbohydrate (CHO), or CHO alone on AWC. Using a double-blind random design, 26 young men (mean age ± SD, 19.9 ± 1.6 years) were assigned to 1 of 3 treatment conditions: (a) 35 g of flavored CHO powder as a placebo (PL, n = 8); (b) 5.25 g of CM and 1 g of CHO in a flavored powder blend (CM, n = 9); and (c) 5.25 g of CM and 33 g of CHO in flavored powder blend (CM-CHO, n = 9). The subjects completed 3 phases of testing on an electronically braked cycle ergometer: (a) familiarization (3 learning trials to establish power outputs for subsequent testing); (b) pretesting (4 bouts performed at power outputs selected to elicit fatigue in 1-10 minutes); and (c) posttesting (4 bouts performed at the same power outputs as pretesting but completed after ingesting the supplements 4 times per day for 6 consecutive days). The results indicated that CM and CM-CHO supplementation significantly (p <0.05) increased AWC by 9.4 and 30.7%, respectively. These data suggest that 33 g of CHO may augment the effects of CM supplementation on AWC.