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Effects of Four Weeks of High-Intensity Interval Training and Creatine Supplementation on Critical Power and Anaerobic Working Capacity in College-Aged Men

Kendall, Kristina L1; Smith, Abbie E1; Graef, Jennifer L1; Fukuda, David H1; Moon, Jordan R1; Beck, Travis W2; Cramer, Joel T2; Stout, Jeffrey R1

The Journal of Strength & Conditioning Research: September 2009 - Volume 23 - Issue 6 - p 1663-1669
doi: 10.1519/JSC.0b013e3181b1fd1f
Original Research

Kendall, KL, Smith, AE, Graef, JL, Fukuda, DH, Moon, JR, Beck, TW, Cramer, JT, and Stout, JR. Effects of four weeks of high-intensity interval training and creatine supplementation on critical power and anaerobic working capacity in college-aged men. J Strength Cond Res 23(6): 1663-1669, 2009-The critical power test provides 2 measures, critical power (CP) and anaerobic working capacity (AWC). In theory, the CP measurement represents the maximal power output that can be maintained without fatigue, and AWC is an estimate of work capacity associated with muscle energy reserves. High-intensity interval training (HIIT) has been shown to be an effective training method for improving endurance performance, including O2PEAK. In addition, creatine (Cr) supplementation has been reported to improve AWC without training; however, it has shown no effect on CP. The purpose of this study was to examine the effects of 4 weeks of HIIT with Cr supplementation on CP and AWC. Forty-two recreationally active men volunteered to participate in this study. Participants were randomly assigned to 1 of 3 groups: Cr (n = 16), 10 g Cr + 10 g dextrose; placebo (PL, n = 16), 20 g dextrose; control (CON, n = 10), no treatment. Before and after supplementation, each participant performed a maximal oxygen consumption test (O2PEAK) on a cycle ergometer to establish peak power output (PPO). Participants then completed a CP test involving 3 exercise bouts with the workloads set as a percentage of their PPO to determine CP and AWC. After a 2-week familiarization period of training and supplementing, PPO, CP, and AWC were remeasured before an additional 4 weeks of HIIT and supplementation were completed. Training consisted of 5 sets of 2-minute exercise bouts with 1 minute rest in between performed on the cycle ergometer, with intensities based on PPO. A significant improvement in CP was observed in the Cr group (6.72% ± 2.54%), whereas PL showed no significant change (3.87% ± 2.30%), and CON significantly decreased (6.27% ± 2.38%). Furthermore, no changes in AWC were observed in any of the groups after treatment. The current findings suggest that Cr supplementation may enhance the effects of intense interval endurance training on endurance performance changes.

1Metabolic and Body Composition Laboratory; and 2Biophysics Laboratory, Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, Norman, Oklahoma 73019

Address correspondence to Dr. Jeffrey R. Stout,

© 2009 National Strength and Conditioning Association