Creatine Supplementation: Effects on Young Men's Body Composition and Performance
A systematic review and meta-analysis published in Frontiers in Nutrition has examined the effects of creatine supplementation on body composition and anaerobic performance in young men, comparing outcomes between resistance-trained and non-resistance-trained individuals. The analysis of 39 randomized controlled trials found that while certain performance benefits occurred regardless of training type, gains in lean body mass were specific to contexts involving resistance training.
Study Design and Methodology
Researchers synthesized data from 39 randomized controlled trials involving healthy men aged 18 to 30. The studies were sourced from databases including PubMed, Web of Science, Scopus, Embase, the Cochrane Library, and SPORTDiscus.
- Participant Groups: Studies were classified by training context: 25 involved resistance training, while 14 involved non-resistance training (e.g., sprint or jump training). Participants' training status ranged from sedentary to elite athletes.
- Supplementation Protocol: Creatine supplementation protocols varied from 4 days to 12 weeks, with most utilizing a loading dose followed by a maintenance phase. Control conditions used carbohydrate-based placebos or inert substances.
- Risk of Bias: Approximately 64% of the included trials were assessed as having a low risk of bias. No evidence of publication bias was detected, and sensitivity analyses indicated the results were not driven by any single study.
Key Findings on Performance and Strength
The meta-analysis reported the following outcomes for strength and anaerobic performance measures:
Squat Strength: Creatine supplementation produced significant improvements in the one-repetition maximum (1RM) for the squat exercise. This improvement was observed in both resistance and non-resistance training contexts.
- Leg Press Strength: No significant effect was observed for the leg press 1RM.
- Jump Performance: Countermovement jump height showed a small but statistically significant improvement overall. This improvement was significant only in non-resistance training studies and in trials lasting 8 weeks or longer.
- Anaerobic Power: Significant improvements were recorded in both peak and mean power output during Wingate anaerobic tests. These gains occurred regardless of training type.
Key Findings on Body Composition
The analysis reported specific outcomes related to changes in body composition:
Pooled Analysis: When data from all studies were combined, creatine supplementation was associated with an average increase of 2.32 kg in fat-free mass and 1.61 kg in lean body mass.
- Training Context Effect: These body composition gains were confined to studies conducted in resistance training settings. No significant changes in fat-free mass or lean body mass occurred in the non-resistance training studies.
Analysis of Training Context
The study highlighted how the training context influenced the outcomes of creatine supplementation:
- Body Composition: Gains in lean mass were exclusive to resistance training settings.
- Strength: Squat strength improved in both contexts.
- Power & Jumping: Wingate power improvements occurred in both contexts. Jump height improvements were significant only in non-resistance training studies.
- Additional Notes: The researchers noted that competitive athletes showed significant jump improvements where recreational participants did not. They also stated that short-term increases in lean mass may partly reflect intracellular water retention.
Certainty of Evidence and Limitations
The researchers graded the certainty of the evidence for the reported outcomes:
- High Certainty: Evidence for Wingate peak power improvement.
- Moderate Certainty: Evidence for squat strength and body composition outcomes.
- Low Certainty: Evidence for leg press strength and jump height outcomes.
The analysis noted several limitations, including that the finding of squat strength effects in non-resistance settings is based on a limited number of studies, substantial heterogeneity in jump height results, and that the analysis was restricted to young men aged 18-30.
Background on Creatine
Creatine is a naturally occurring compound found primarily in skeletal muscle. Dietary intake accounts for an estimated 60-80% of total creatine stores, and supplementation can increase intramuscular creatine by 20-40%. The phosphocreatine-creatine kinase system plays a key role in rapidly restoring adenosine triphosphate (ATP) during short bursts of high-intensity activity.