Effects of beta-hydroxy-beta-methylbutyrate supplementation during resistance training on strength, body composition, and muscle damage in trained and untrained young men: a meta-analysis.
Level 1 - systematic review of randomized trials
Meta-analysis of resistance training trials
PubMed 19387395 · doi:10.1519/JSC.0b013e3181a00c80
What was done
Meta-analysis of 9 qualifying studies (14 comparisons, 394 male subjects, mean age 23 ± 2 years, mean intervention duration 5 ± 2 weeks, 5 ± 6 h/week training) evaluating the effects of beta-hydroxy-beta-methylbutyrate (HMB) during resistance training. A meta-analytic mixed model weighted by sample size evaluated upper-body, lower-body, and overall strength, fat and fat-free mass, and creatine kinase, adjusting for training status (trained vs. untrained), HMB dose, intervention duration, training load, and dietary cointerventions.
What was found
In untrained lifters, HMB supplementation resulted in small gains in lower-body strength (mean ± 90% confidence limit: 9.9% ± 5.9%) and average strength (6.6% ± 5.7%), with negligible upper-body gains (2.1% ± 5.5%). In trained lifters, all strength outcomes were trivial. Across all participants combined, overall strength improvement was trivial (3.7% ± 2.4%). Effects on fat and fat-free mass were trivial, and effects on creatine kinase were unclear.
Why it matters
This meta-analysis indicates that HMB offers modest strength benefits strictly to novice lifters during early training, whereas it has trivial effects on strength or body composition in trained individuals.
Limits
The total sample was relatively small (394 subjects across 9 trials) with short durations averaging 5 weeks. Findings apply only to young men, and outcomes for muscle damage (creatine kinase) remained unclear.
Cited by
- supports HMB (beta-hydroxy beta-methylbutyrate) is a breakdown metabolite of leucine that has been shown in studies to improve muscle strength when taken as a supplement.