Outcome
    Moderate Evidence

    HMB for Enhanced Athletic Performance

    HMB helps mainly untrained individuals and catabolic states; effects in trained athletes are small or absent.

    Overview

    HMB helps mainly untrained individuals and catabolic states; effects in trained athletes are small or absent.

    Verdict

    Mixed evidence

    How It Works

    HMB suppresses proteolysis through the ubiquitin-proteasome pathway and modestly stimulates mTOR-dependent protein synthesis.

    Dosing & Protocol

    Typical dose

    Recommended dose
    3 g/day HMB in three 1 g doses with meals; the calcium salt taken 60 minutes pre-exercise, or free acid form 30 minutes before
    Expected timeframe
    8-12 weeks

    Protocol

    form
    Calcium HMB is the standard and cheapest form; HMB free acid is absorbed faster and was used in some later trials, taken 30 minutes pre-exercise versus 60 minutes for the calcium salt
    duration
    8-12 weeks minimum alongside a structured training programme
    co factor
    Take with meals, with one dose timed before training. Evidence is mixed and splits sharply by population. In untrained individuals starting resistance training, and in older or catabolic populations, HMB trials report improvements in lean mass and strength. In trained athletes the results are largely null, and the field carries a specific credibility problem: several dramatically positive trials from one research group reported effect sizes far beyond anything plausible and were subsequently the subject of formal expert criticism. Independent trials in trained lifters generally find no benefit. HMB is a leucine metabolite that reduces muscle protein breakdown, which is why it does more where breakdown is elevated than where training and protein intake are already optimised.
    titration
    No titration; 3 g/day is the dose used in essentially all trials, and more has not been shown to help
    starting dose
    3 g/day split as 1 g three times daily with meals

    Evidence

    What the studies say

    Meta-analyses show small strength gains in untrained participants and minimal effect in trained lifters. Some widely cited positive trials in athletes have been criticised for implausible effect sizes.

    No studies are yet linked to both HMB and Enhanced Athletic Performance.

    Safety

    Caveats

    HMB is not a substitute for adequate protein - 1.6-2.2 g/kg/day of total protein, progressive overload and sleep account for the overwhelming majority of training adaptation, and leucine-rich protein already supplies HMB precursor. Safety: HMB has a good safety record at 3 g/day over months, with no consistent adverse effects on liver, kidney or lipid markers in trials, but there is no established upper intake level and no long-term data beyond a year. Avoid in pregnancy and breastfeeding, where safety is not established, and in children and adolescents, where data are minimal. Use caution in renal or hepatic impairment given limited data. There are no well-characterised drug interactions, but tell your clinician if you are taking it. Athletes subject to testing should choose batch-tested products, since supplements marketed for muscle are a recurrent source of contamination.

    Less likely to help if

    Trained athletes with adequate protein intake, in whom independent trials show no benefit.

    Medical Disclaimer

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    Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.