HMB builds strength for beginners, then the benefit all but disappears

HMB is a popular supplement in the resistance training community, sold on claims of increased strength, faster muscle growth and better recovery. The research behind those claims has been stubbornly inconsistent, with some studies finding benefits and others finding none. One plausible explanation for the mess is training experience: a compound that helps a novice adapting to brand-new stress might do nothing for a seasoned lifter. This analysis set out to pool the evidence and test exactly that split.

The researchers pooled nine qualifying studies, yielding 14 comparisons split by training experience, covering 394 subjects with an average age of 23. Interventions lasted around 5 weeks with roughly 5 hours of training per week. Their statistical model controlled for between-study differences in HMB dose, intervention duration, training load and dietary cointerventions. Outcomes included upper-body, lower-body and average strength, fat and fat-free mass, and creatine kinase, a marker of muscle damage.

In untrained lifters there were small benefits to lower-body strength (9.9%) and average strength (6.6%), but only negligible gains in upper-body strength (2.1%). In trained lifters, all strength outcomes were trivial. Combining every study, the overall average strength increase was a trivial 3.7%, although the uncertainty allows for a small benefit. Effects on fat mass and fat-free mass were trivial across the board, and the results for creatine kinase were unclear.

This helps explain why the HMB literature looked so contradictory: studies in novices and studies in experienced lifters were measuring different things. It undercuts the broad marketing pitch, since the body composition claims found no support here and the strength benefit was confined to beginners. Why untrained lifters responded at all remains unexplained, and the authors say that mechanism needs further research. Evidence in women and older adults is a separate open question this analysis could not address.

If you are an experienced lifter weighing up HMB, this pooled evidence suggests the strength and physique benefits are too small to notice. For someone brand new to resistance training, there is a small, genuine lower-body strength effect on record, though whether it matters next to the enormous gains novices make anyway is worth pondering. The muscle damage and recovery claims remain unproven either way. This is information for judging marketing claims, not a recommendation in either direction.