Clinical comment

Creatine is predominately stored in skeletal muscle (fast twitch, type II fibers) where it serves as the energy substrate for muscle contraction.³ In its phosphorylated form, creatine contributes to the re‐synthesis of adenosine triphosphate (ATP) from adenosine diphosphate (ADP) which occurs during short‐duration and high‐intensity exercises.⁴ This suggests and therefore serves as the rationale for creatine supplementation as an ergogenic aid.⁵

Available literature and quality of the evidence

A number of randomized controlled trials (RCTs) exist to answer this question.

Findings

A double‐blind study tested 12 adult male cyclists pre‐ and post‐ a 28‐day creatine supplementation regimen. The changes in plasma volume from pre‐ to post‐supplementation were significantly greater in the creatine group (14.0 ± 6.3%) than the placebo group (−10.4 ± 4.4%; p <0.05) at 90 minutes of exercise.⁶

In short‐interval exercise it was concluded that creatine supplementation increases short‐terms bursts, such as dribble and power tests (vertical jumping) with young soccer players.⁷

In a double‐blinded, placebo‐controlled RCT, 14 men ingested 25 g/day of creatine monohydrate for seven days. Subjects performed five sets of bench press to failure and a jump squat (five sets of 10 repetitions using 30% of each subject’s one repetition max [RM]). It was concluded that one week of creatine supplementation (25 g/day) enhances muscular performance during repeated sets of bench press and jump squat exercises.⁸

A study on cyclists for five days of 20 g creatine supplementation testing maximal power output to exhaustion found oxygen consumption larger after creatine supplementation (10.40 ± 0.65 L) to (11.82 ± 0.34 L).⁹

Reardon et al. looked at the potential effect of creatine supplementation on aerobic long durance exercise. Subjects completed 45‐minute cycling sessions. It was concluded that the ergogenic potential of creatine supplementation in endurance performance does not produce significant results.¹⁰

A test on 12 regional class triathletes for five days on a 6 g/day creatine dosing and cycling 30 minutes to exhaustion found endurance performance was not influenced as interval power was only increased by 18%.¹¹

Fourteen female and eight male collegiate athletes supplemented with seven days of 25 g/day creatine were subjected to three timed 60 m sprints trials. Results showed creatine supplementation did not enhance speed during 60 m sprints.¹²

Recent literature has illuminated the anabolic/performance‐enhancing mechanisms of creatine,¹³ suggesting that these effects may be due to satellite cell proliferation, myogenic transcription factors, and insulin‐like growth factor‐1 signaling.¹⁴ Changes in myogenic transcription factors occur when creatine supplementation and resistance training are combined in young healthy males. It was observed that serum levels of myostatin, a muscle growth inhibitor, were decreased in the creatine group.¹⁵

Resolution of clinical scenario

The suggestion from various sports and training regimens is that creatine supplementation may be effective as an ergogenic aid in short bursts of intense exercise, but that it does not seem to be beneficial in aerobic, endurance exercises.

Creatine has been demonstrated to be of performance benefit in modes of exercise such as high‐intensity sprints or endurance training. The evidence also demonstrates that it appears that the effects of creatine diminish as the length of time spent exercising increases.