Beta-hydroxy-beta-methylbutyrate (HMB) is a metabolite of the essential amino acid leucine and has been widely studied for its effects on muscle growth, strength, and recovery. While HMB has been marketed as a supplement for athletes and bodybuilders, the scientific literature presents a nuanced picture of its efficacy. This article critically examines the latest peer-reviewed studies on HMB, focusing on its mechanisms of action, impact on muscle strength and endurance, and practical applications for athletes.

Mechanisms of Action

HMB’s purported benefits stem from its ability to:

1. Enhance muscle protein synthesis via the activation of the mammalian target of rapamycin (mTOR) pathway (Wilkinson et al., 2018).
2. Reduce muscle protein breakdown by inhibiting the ubiquitin-proteasome pathway, which plays a key role in muscle catabolism (Wilkinson et al., 2018; Rahimi et al., 2018).
3. Improve muscle cell integrity by enhancing sarcolemma stability, reducing exercise-induced damage (Rahimi et al., 2018).

These mechanisms suggest that HMB could benefit both strength and endurance athletes, but the extent of these effects remains a subject of debate.

HMB and Muscle Strength: Trained vs. Untrained Athletes

Untrained or Beginner Athletes

Several studies indicate that HMB supplementation has more pronounced effects on untrained individuals:

• A meta-analysis by Rahimi et al. (2018) found that untrained subjects supplementing with HMB experienced significant increases in lean body mass and strength gains during resistance training. This aligns with earlier studies, such as Nissen et al. (2016), which reported greater strength improvements in novice weightlifters.
• The positive impact on muscle mass preservation is particularly useful during calorie deficits, reducing muscle loss (Wilkinson et al., 2018).

Trained Athletes and Strength Gains

Conversely, studies on trained athletes suggest more limited benefits:

• Rahimi et al. (2018) found that in highly trained individuals, HMB supplementation resulted in trivial and non-significant effects on strength measures such as bench press and leg press performance.
• These findings are consistent with Wilson et al. (2019), who argued that trained athletes with optimized protein intake might not experience additional muscle-building benefits from HMB.

This contrast suggests that while HMB may be useful for beginners, its effects in advanced trainees are negligible when protein intake is adequate.

HMB and Endurance Performance

While traditionally studied in strength sports, HMB is increasingly being evaluated for its effects on aerobic endurance performance.

• Fernández-Landa et al. (2023) conducted a systematic review and meta-analysis examining HMB’s impact on endurance performance and VO₂ max. Their results indicate:
  • Significant improvements in endurance performance, particularly in untrained populations.
  • Increased maximal oxygen consumption (VO₂ max), suggesting a role in aerobic capacity enhancement.
  • Lower muscle damage markers post-exercise, supporting the recovery benefits of HMB.

These findings align with earlier work by Wilson et al. (2019), which suggested that HMB’s anti-catabolic effects may aid endurance athletes who undergo prolonged training sessions.

HMB and Recovery: The Anti-Catabolic Effect

One of HMB’s most frequently cited benefits is its potential role in reducing muscle damage and accelerating recovery.

• Reduced Muscle Soreness:
  • Wilkinson et al. (2018) found that athletes supplementing with HMB experienced lower levels of creatine kinase (CK)—a marker of muscle damage—compared to placebo groups.
  • This aligns with Rahimi et al. (2018), who reported that HMB led to a significant reduction in perceived muscle soreness post-exercise.
• Faster Recovery:
  • Fernández-Landa et al. (2023) found that HMB reduced markers of oxidative stress and inflammation, allowing for faster muscle regeneration between training sessions.
  • This supports findings by Wilson et al. (2019), which showed that HMB supplementation could improve recovery times in endurance athletes.

Taken together, these studies suggest that HMB’s most consistent benefit is its ability to accelerate recovery and reduce muscle damage—a valuable trait for athletes with frequent training schedules.

HMB and Hormonal Responses

Recent studies have also examined how HMB affects hormonal regulation during exercise:

• Cortisol Reduction: Fernández-Landa et al. (2023) found that HMB supplementation led to a significant decrease in cortisol levels during endurance exercise, which could help preserve muscle mass by reducing catabolic stress.
• Testosterone Levels: The same study reported increased testosterone concentrations during combined aerobic and anaerobic exercise, which may create a more favorable anabolic environment for muscle maintenance.

These hormonal effects support the findings of Wilson et al. (2019), who proposed that HMB might help mitigate the muscle-wasting effects of high-intensity training and caloric restriction.

Dosage, Safety, and Practical Considerations

Recommended Dosage

• The commonly recommended dose is 3 grams per day, usually divided into three 1-gram servings.
• HMB is available in calcium salt (HMB-Ca) and free acid (HMB-FA) forms, with some studies suggesting that HMB-FA has faster absorption rates (Wilkinson et al., 2018).

Safety and Long-Term Use

• Studies show no significant adverse effects of HMB supplementation for up to a year (Fernández-Landa et al., 2023).
• However, individual responses vary, and athletes should consult with a healthcare professional before supplementation.

Conclusion: Is HMB Worth It for Athletes?

Who Benefits Most from HMB?

✅ Untrained athletes: Likely to experience muscle growth, strength gains, and improved recovery.
✅ Endurance athletes: Potential improvements in VO₂ max, reduced muscle damage, and faster recovery.
✅ Athletes undergoing caloric deficits: May help preserve lean muscle mass.

Who May Not Benefit?

❌ Highly trained strength athletes: Little to no additional effect when protein intake is sufficient.
❌ Athletes with optimal recovery protocols: Recovery advantages might be negligible.

Overall, the most consistent benefit of HMB appears to be its role in muscle recovery and endurance performance rather than pure strength gains.

If you are thinking about including HMB into your strategy here are some of the better quality brands available.

HMB-CA (Calcium Salt)

HMB-FA (Free Acid)