The effects of creatine monohydrate loading on anaerobic performance and one-repetition maximum strength

Journal Title (Medline/Pubmed accepted abbreviation): J. Strength Cond. Res.
Year: 2012
Volume: 26
Issue :6
Page Numbers : 1651-1656

Summary of Background and Research Design

Background: Creatine is one of the most popular supplements used by athletes to increase strength and physical performance.  Loading is the process of taking a high dose of a supplement every day for about 1 week, usually after not taken the supplement for at least several weeks.  There is currently conflicting data on whether short-term creatine supplementation is effective at increasing power and strength and/or if it affects body weight.

Hypothesis:Supplementation with 20 g creatine per day for 7 days will increase mean and peak power but have no effect on body weight in sedentary subjects.

Subjects: 22 healthy males, age 22.1 ± 2.0 y, involved in 4 hours or less of physical activity per week

Experimental design: randomized, double-blind, placebo-controlled trial with independent groups

Treatments : Creatine or placebo (maltodextrin), 20 g/day, mixed with 12 oz. of water

Protocol :The participants were first evaluated for anaerobic performance using the Wingate Anaerobic Test.  On a stationary bicycle, participants pedaled as fast as possible for 30 sec.  Resistance was adjusted according to body weight.  The number of repetitions was monitored and both peak power and mean power were calculated.  To evaluate strength, the participants were evaluated for 1 repetition maxima (1RM) for leg extension and bench press.  The participants then consumed one of the two supplements for 7 days and then repeated the exercises.

Summary of Research Findings
  • There was no difference in average daily caloric intake between the two groups.
  • There were no significant differences in strength, power output, or body weight between groups before the supplement was taken.
  • Those taking creatine displayed an increase in mean power during the Wingate Anaerobic test (average 624.6 ± 73.8 W at the pre-test to 658.3 ± 80.0 W at the post-test) whereas the placebo group showed no gain on average (591.8 ± 98.1 W at the pre-test to 590.1 ± 82.0W at the post-test; p = 0.03).
  • There was no significant difference in peak power during the Wingate Anaerobic test between groups.
  • Body weight did not change significantly for either group over the course of the week.
  • There were no significant differences between groups for 1RMs.

Key practice applications

Even in sedentary males, creatine loading (20 g/day for 7 days) can increase one’s ability to generate power.


The authors did not state whether the creatine was taken the day of the post-test, which may have affected the participants positively (due to ergogenic effects) or negatively (due to side effects such as gastrointestinal discomfort).  It would also have been helpful if the authors asked the participants to complete questionnaires that assessed side effects.  The dose used here, 20 g, is very high compared to maintenance daily doses (2-5 g/day) and it was not clear from this article if the entire 20 g daily dose was given at one time.  Whether or not the total daily dose was subdivided, it would have been good to evaluate this parameter, especially in a sedentary population with no previous creatine supplementation experience. 
A t-test is not an appropriate post-hoc analysis for an ANOVA.  A more appropriate test would be the Least Square Difference or Tukey’s post-hoc analysis.  Differences in statistical analyses can affect the interpretation of the data.

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