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

Abstract

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 VO2PEAK. 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 VO2PEAK 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.

Energetics of Muscular Exercise

“…Not all conditions, however, have been investigated in terms of effects on _ w cr . In any case, and coherently with the principles pointed out here above, it has been demonstrated that both continuous (Heubert et al 2003;Jenkins and Quigley 1992) and high-intensity interval training (Gaesser and Wilson 1988;Jenkins and Quigley 1993;Kendall et al 2009;Poole et al 1990;Vanhatalo et al 2008) increase _ w cr . Moreover, strength training was shown to increase the time to exhaustion during high-intensity exercise by an effect on W′ without changes of _ w cr (Sawyer et al 2014).…”

“…Coherently with this prediction, glycogen depletion reduces W′ (Miura et al 2000), whereas creatine supplementation increases it (Kendall et al 2009;Smith et al 1998).…”

Creatine supplementation attenuates hemodynamic and arterial stiffness responses following an acute bout of isokinetic exercise

“…Although we did not measure serum Cr concentration, a dose similar to the one used in the present study (10 g/day) has been shown to significantly increase serum Cr levels. (Jones et al 2009;Kendall et al 2009) However, a larger dose (20 g/day) may be required to improve isokinetic performance (Gilliam et al 2000). We used baPWV as an index of arterial stiffness instead of aortic PWV.…”

“…Creatine (Cr) supplementation has shown to improve anaerobic performance (Andrews et al 1998;Kendall et al 2009). This effect has been attributed to an increase in muscle phosphocreatine stores that may delay the accumulation of muscle metabolites (Andrews et al 1998).…”

Drug abuse in athletes

“…Creatine is not currently on the WADA banned list and is the most popular nutritional supplement for performance enhancement 3. Studies demonstrate increased maximum power output and lean body mass from creatine 43,44. As such, some allowable nutritional supplements may have ergogenic effects, but may have insufficient evidence supporting their ergogenic properties to rise to the level of being banned.…”