International society of sports nutrition position stand: β-hydroxy-β-methylbutyrate (HMB)

Position Statement: The International Society of Sports Nutrition (ISSN) bases the following position stand on an analysis of the literature regarding the effects of β-Hydroxy-β-Methylbutyrate (HMB). The following 12 points have been approved by the Research Committee of the Society: 1. HMB is a metabolite of the amino acid leucine that is naturally produced in both humans and other animals. Two forms of HMB have been studied: Calcium HMB (HMB-Ca) and a free acid form of HMB (HMB-FA). HMB-FA appears to lead to increased appearance of HMB in the bloodstream when compared to HMB-Ca, though recent results are mixed. 2. The available safety/toxicity data suggest that chronic HMB-Ca and HMB-FA consumption are safe for oral HMB supplementation in humans up to at least one year. 3. There are no negative effects of HMB-Ca and HMB-FA on glucose tolerance and insulin sensitivity in humans. There may be improvements in glucose metabolism in younger adults. 4. The primary mode of action of HMB appears to be through its dual mechanism to enhance muscle protein synthesis and suppress muscle protein breakdown. HMB's activation of mTORC1 is independent of the leucine-sensing pathway (Sestrin2-GATOR2 complex). 5. HMB may help reduce muscle damage and promote muscle recovery, which can promote muscle growth/repair. HMB may also have anti-inflammatory effects, which could contribute to reducing muscle damage and soreness. 6. HMB consumption in close proximity to an exercise bout may be beneficial to increase muscle protein synthesis and attenuate the inflammatory response. HMB can provide a beneficial physiological effect when consumed both acutely and chronically in humans. 7. Daily HMB supplementation (38 mg/kg body weight) in combination with exercise training may improve body composition through increasing lean mass and/or decreasing fat mass with benefits in participants across age, sex, and training status. The most pronounced of these improvements in body composition with HMB have been observed in studies with robust resistance training programs and dietary control. 8. HMB may improve strength and power in untrained individuals, but its performance benefits in trained athletes are mixed and increase with an increase in study duration (>6 weeks). HMB's beneficial effects on athletic performance are thought to be driven by improved recovery. 9. HMB supplementation appears to potentially have a positive impact on aerobic performance, especially in trained athletes. The mechanisms of the effects are unknown. 10. HMB supplementation may be important in a non-exercising sedentary and aging population to improve muscle strength, functionality, and muscle quality. The effects of HMB supplementation with exercise are varied, but the combination may have a beneficial effect on the treatment of age-associated sarcopenia under select conditions. 11. HMB may be effective in countering muscle disuse atrophy during periods of inactivity due to illness or injury. The modulation of mitochondrial dynamics and lipid metabolism by HMB may be a potential mechanism for preventing disuse atrophy and aiding rehabilitation beyond HMB's effects on rates of muscle protein synthesis and degradation. 12. The efficacy of HMB in combination with certain nutrients may be enhanced under select conditions.

Ergogenic Benefits of β-Hydroxy-β-Methyl Butyrate (HMB) Supplementation on Body Composition and Muscle Strength: An Umbrella Review of Meta-Analyses

BACKGROUND

β-Hydroxy-β-methyl butyrate (HMB) is a metabolite of the amino acid leucine, known for its ergogenic effects on body composition and strength. Despite these benefits, the magnitude of these effects remains unclear due to variability among studies. This umbrella review aims to synthesize meta-analyses investigating the effects of HMB on body composition and muscle strength in adults.

METHODS

A comprehensive literature search was conducted in Scopus, PubMed and Web of Science without date or language restrictions until August 2024. The study protocol was registered at Prospero (No. CRD42023402740). Included studies evaluated the effects of HMB supplementation on body mass, fat mass (FM), fat-free mass (FFM), muscle mass and performance outcomes. Effect sizes (ESs) and 95% confidence intervals (CIs) were calculated, and a random-effects model was used for meta-analysis. Standard methods assessed heterogeneity, sensitivity and publication bias. The methodological quality of included studies was assessed using the AMSTAR2 tool.

RESULTS

Eleven studies comprising 41 data sets were included, with participants aged 23-79 years. HMB supplementation significantly increased muscle mass (ES: 0.21; 95% CI: 0.06-0.35; p = 0.004), muscle strength index (ES: 0.27; 95% CI: 0.19-0.35; p < 0.001) and FFM (ES: 0.22; 95% CI: 0.11-0.34; p < 0.001). No significant changes were observed in FM (ES: 0.03; 95% CI: -0.04 to 0.35; p = 0.09) or body mass (ES: 0.09; 95% CI: -0.06 to 0.24; p = 0.22). The quality assessment revealed that five studies were of high quality, three were of low quality and three were of critically low quality.

CONCLUSIONS

HMB supplementation may benefit individuals experiencing muscular atrophy due to physiological conditions, particularly enhancing muscle mass and strength without significant changes in fat mass or body weight.

β-Hydroxy β-Methyl Butyric Acid (HMB) and Its Potential Doping Relevance: A Pilot Study on Its Urinary Excretion Profile

β-hydroxy β-methyl butyric acid (HMB), either as the free acid or in the form of its calcium salt, is a component of several dietary supplements marketed to enhance sports performance, due to its role in protein synthesis. In this pilot study, we investigated the urinary excretion profile of HMB, an endogenous metabolite of the essential amino acid leucine. The endogenous reference ranges of HMB, in human urine samples, were monitored by collecting samples from 20 volunteers. Data obtained were compared with those from controlled excretion studies, following the intake of a 3-g oral dose of HMB. Urine samples were analyzed through a targeted procedure employing a conventional GC-MS system operating in SIM mode. Our results show that the excreted urinary concentration of HMB significantly exceeds the range of endogenous concentrations for at least 24 h, making possible to detect its exogenous origin.

Effects of β-hydroxy-β-methylbutyrate (HMB) supplementation on lipid profile in adults: a GRADE-assessed systematic review and meta-analysis of randomized controlled trials

Background and aim

The regulation of lipid metabolism is crucial for preventing cardiovascular diseases, which are among the leading causes of mortality worldwide. β-hydroxy-β-methylbutyrate (HMB) has garnered attention for its potential role in modulating lipid profiles. However, the magnitude of these effects are unclear due to the heterogeneity of the studies. This study aimed to provide a comprehensive overview of the randomized controlled trials (RCTs) that have examined the effects of HMB on lipid profiles in adults.

Methods

Databases including PubMed, Web of Science, and Scopus, were searched for relevant studies through January 2024. The study protocol was also registered at Prospero (no. CRD42024528549). Based on a random-effects model, we calculated WMDs and 95% confidence intervals (CIs). The outcomes assessed included total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C). Sensitivity, subgroup and meta-regression analyses were also conducted.

Results

Our analysis included a total of 10 RCTs comprising 421 participants. The pooled data revealed no significant effect of HMB supplementation on TC (WMD: -2.26 mg/dL; 95%CI: -6.11 to 1.58; p = 0.25), TG (WMD: -2.83 mg/dL 95% CI: -12.93 to 7.27; p = 0.58), LDL-C (WMD: 0.13 mg/dL; 95%CI: -3.02 to 3.28; mg; p = 0.94), and HDL-C (WMD: -0.78 mg/dL; 95%CI: -2.04 to 0.48; p = 0.22). The quality of evidence was rated as moderate to low for all outcomes.

Conclusion

The current evidence from RCTs suggests that HMB supplementation does not significantly alter lipid profiles, including TC, TG, LDL-C, and HDL-C. Further research is warranted to confirm these results and explore the potential mechanisms of action of HMB.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=528549, CRD42024528549.

Effects of exercise with or without β-hydroxy-β-methylbutyrate supplementation on muscle mass, muscle strength, and physical performance in patients with sarcopenia: a systematic review and meta-analysis

Objectives

This systematic review and meta-analysis aimed to assess the effects of exercise with/without β-hydroxy-β-methylbutyrate (HMB) supplementation on muscle mass, muscle strength, physical performance, and body composition in patients with sarcopenia.

Methods

A literature search for randomized controlled trials (RCTs) on the effects of exercise with or without HMB supplementation on muscle mass, muscle strength, physical performance, and body composition in patients with sarcopenia was conducted using PubMed, Web of Science, EBSCO, The Cochrane Library, EMBASE, Scopus, Science Direct, China Knowledge Resource Integrated Database (CNKI), and Wan Fang database. The search was limited to studies published up to April 2024 for each database. The outcome measures included muscle mass, muscle strength, physical performance, and body composition. The Cochrane Risk of Bias Assessment Tool was used to evaluate the quality of the included literature, and RevMan 5.4 software was employed to perform a meta-analysis of the outcome indicators.

Results

Five RCTs involving 257 elderly patients with sarcopenia were included in this study. Meta-analysis showed that in terms of physical performance, exercise with HMB supplementation significantly increased gait speed in sarcopenic patients compared to the exercise combined with the placebo group (SMD = 0.48, 95% CI: 0.15 to 0.82, p = 0.005), but exercise combined with HMB supplementation did not have significant effects on SMI (SMD = 0.06, 95% CI: -0.20 to 0.32, p = 0.66), grip strength (SMD = 0.23, 95% CI: -0.05 to 0.52, p = 0.11), five-time chair stand test (SMD = -0.83, 95% CI: -1.88 to 0.21, p = 0.12), fat-free mass (SMD = 0.04, 95% CI: -0.26 to 0.35, p = 0.78), BMI (SMD = -0.09, 95% CI: -0.43 to 0.25, p = 0.60), and fat mass (SMD = 0.01, 95% CI: -0.25 to 0.27, p = 0.94).

Conclusion

The current evidence indicates that exercise with HMB supplementation may enhance physical performance in patients with sarcopenia compared to exercise with the placebo group. However, the effects on muscle mass, muscle strength, and body composition are likely minimal. The above findings are limited by the number of included studies and require further validation through high-quality studies.

Systematic Review Registration

Prospero (CRD42024500135).

Amino acids regulating skeletal muscle metabolism: mechanisms of action, physical training dosage recommendations and adverse effects

Maintaining skeletal muscle mass is important for improving muscle strength and function. Hence, maximizing lean body mass (LBM) is the primary goal for both elite athletes and fitness enthusiasts. The use of amino acids as dietary supplements is widespread among athletes and physically active individuals. Extensive literature analysis reveals that branched-chain amino acids (BCAA), creatine, glutamine and β-alanine may be beneficial in regulating skeletal muscle metabolism, enhancing LBM and mitigating exercise-induced muscle damage. This review details the mechanisms of these amino acids, offering insights into their efficacy as supplements. Recommended dosage and potential side effects are then outlined to aid athletes in making informed choices and safeguard their health. Lastly, limitations within the current literature are addressed, highlighting opportunities for future research.

Effects of HMB on Endurance Performance in a Healthy Population: A Systematic Review and Meta-Analysis

ABSTRACT

Fernández-Landa, J, Todorovic, N, Santibañez-Gutierrez, A, Ostojic, SM, Calleja-González, J, Sekulic, D, and Mielgo-Ayuso, J. Effects of HMB on endurance performance in a healthy population: a systematic review and meta-analysis. J Strength Cond Res 38(4): e202-e210, 2024-β-hydroxy-β-methylbutyrate (HMB) has been used extensively as a dietary supplement for athletes and physically active people. However, the ergogenic effect of HMB supplementation on endurance performance is still unclear. Therefore, this systematic review and meta-analysis (SRMA) aimed to assess HMB supplementation on endurance performance and V̇O 2 max . This SRMA followed PRISMA guidelines. Three electronic databases were searched (PubMed/Medline, Web of Science [WOS], and Scopus) from inception until April 3, 2023. In this SRMA, human experimental trials, controlled with a placebo group, assessing the effect of HMB supplementation on endurance performance in a healthy population were included. The quality of the studies was assessed by the Physiotherapy Evidence Database (PEDro) scale. The study protocol was registered in the Prospective Register of Systematic Review (PROSPERO): CRD42022341790. Eleven studies involving 279 participants met the inclusion criteria. The results displayed a significant improvement on endurance performance (pooled standardized mean difference [SMD] = 0.58 [0.28-0.87]) and V̇O 2 max (pooled SMD = 0.58 [0.21-0.95]) after HMB ingestion. Moreover, after the exclusion of the studies not evenly distributed around the base of the funnel plot, the results continued to be significantly positive in endurance performance (pooled SMD = 0.38 [0.22-0.53]) and V̇O 2 max (pooled SMD = 0.25 [0.09-0.42]). In conclusion, HMB (3 g·d -1 ) ingestion during 2-12 weeks significantly improves endurance performance and V̇O 2 max .

Age-related muscle anabolic resistance: inevitable or preventable?

Age-related loss of muscle mass, strength, and performance, commonly referred to as sarcopenia, has wide-ranging detrimental effects on human health, the ramifications of which can have serious implications for both morbidity and mortality. Various interventional strategies have been proposed to counteract sarcopenia, with a particular emphasis on those employing a combination of exercise and nutrition. However, the efficacy of these interventions can be confounded by an age-related blunting of the muscle protein synthesis response to a given dose of protein/amino acids, which has been termed "anabolic resistance." While the pathophysiology of sarcopenia is undoubtedly complex, anabolic resistance is implicated in the progression of age-related muscle loss and its underlying complications. Several mechanisms have been proposed as underlying age-related impairments in the anabolic response to protein consumption. These include decreased anabolic molecular signaling activity, reduced insulin-mediated capillary recruitment (thus, reduced amino acid delivery), and increased splanchnic retention of amino acids (thus, reduced availability for muscular uptake). Obesity and sedentarism can exacerbate, or at least facilitate, anabolic resistance, mediated in part by insulin resistance and systemic inflammation. This narrative review addresses the key factors and contextual elements involved in reduction of the acute muscle protein synthesis response associated with aging and its varied consequences. Practical interventions focused on dietary protein manipulation are proposed to prevent the onset of anabolic resistance and mitigate its progression.

Effect of Resistance Training Combined with Beta-Hydroxy-Beta-Methylbutyric Acid Supplements in Elderly Patients with Sarcopenia after Hip Replacement

Objectives

To evaluate the efficacy of resistance training (RT) combined with beta‐hydroxy‐beta‐methylbutyric acid (HMB) in the treatment of elderly patients with sarcopenia after hip replacement.

Methods

From January 1, 2018 to December 31, 2018, 200 elderly patients (68 men, mean age 76.3 years and 137 women, mean age 79.1 years) who experienced femoral neck fracture with sarcopenia after hip arthroplasty were assigned to four groups: RT + HMB group, RT group, HMB group, and negative control group. Baseline data, body composition, grip strength, Barthel index (BI), Harris hip score (HHS), and visual analog scale score (VAS) were compared among the four groups before and 3 months after surgery.

Results

A total of 177 participants completed the trial, including 43 in the HMB + RT group, 44 in the HMB group, 45 in the RT group, and 45 in the negative control group. At the 3‐month follow‐up, the body composition and grip strength of the HMB + RT group and RT group were significantly improved compared with those before operation. The HMB group had no significant change, while the measures in the negative control group significantly decreased. Postoperative BI and HSS did not reach pre‐injury levels in any of the four groups, but postoperative VAS score was significantly improved. However, there was no significant difference in BI, HSS, or VAS among the four groups.

Conclusion

RT, with or without HMB supplementation, can effectively improve body composition and grip strength in elderly patients with sarcopenia after hip replacement at short‐term follow‐up. Simultaneously, use of exclusive HMB supplementation alone may also help to prevent decreases in muscle mass and grip strength in these patients.

Effects of β-Hydroxy β-Methylbutyric Supplementation in Combination with Conservative Non-Invasive Treatments in Athletes with Patellar Tendinopathy: A Pilot Study

The aim of the present study was to analyze the effect of conservative non-invasive treatments based on eccentric training, stretching and extracorporeal shock wave therapy (ESWT) supplemented with β-Hydroxy β-methylbutyric (HMB) or placebo (PLAC) on body composition, pain and muscular function (jump ability, muscular power and muscular strength) in athletes with patellar tendinopathy (PT). In a double-blind randomized trial, 8 athletes (4 males and 4 females) performed a physical rehabilitation for 4 weeks. They were randomly divided into two experimental groups (two males and two females in each one) that ingested HMB (HMBG) or PLAC (PLACG). In pre- and post-intervention were assessed body composition, pain, countermovement jump (CMJ), back-squat (BS) for analyzing peak power (W) (PPPP), load (kg) associated to PPPP (PPKG) and mean velocity (m/s) (PPMV) in addition to a 5-RM leg extension tests. An interaction intervention·supplementation (p = 0.049; Ƞ2p = 0.774) was observed in the height reached in the CMJ as an intervention effect in PPPP detected for the HMBG (p = 0.049). In addition, an enhancement in PPKG (p = 0.028; Ƞ2p = 0.842) was detected in the intervention, but not in PPMV, as an increase in the intervention in the 5-RM test (p = 0.001; Ƞ2p = 0.981) was observed. No changes were noted on body composition or pain (p > 0.05). The combination of eccentric training with stretching and ESWT increased concentric muscular power and strength after 4 weeks without changes in body lean mass or pain. In addition, HMB supplementation could enhance the power muscular performance in athletes with PT, optimizing the intervention adaptions.

Effects of exercise and/or β-hydroxy-β-methylbutyrate supplementation on muscle mass, muscle strength, and physical performance in older women with low muscle mass: a randomized, double-blind, placebo-controlled trial

BACKGROUND

The interaction between exercise and nutritional supplementation is unclear among older adults at risk of sarcopenia.

OBJECTIVES

We aimed to examine if β-hydroxy-β-methylbutyrate (HMB) supplementation enhances the effects of exercise on muscle mass, strength, and physical performance and observe potential residual effects in older women with low muscle mass.

METHODS

This 12-wk, randomized, double-blind, placebo-controlled, 2 × 2 factorial design (exercise-only, HMB-only, both, and none) trial included 156 women aged 65-79 y with skeletal muscle index <5.7 kg/m2, and was followed by a 12-wk observational period. Resistance training twice weekly or education programs every 2 wk and calcium-HMB (1500 mg) or placebo supplements daily were provided. The primary outcome was the change in muscle mass from baseline to postintervention. Secondary outcomes included changes in muscle strength and physical performance.

RESULTS

In total, 149 and 144 participants completed the assessment at weeks 12 and 24, respectively. ANOVAs based on the intention-to-treat principle showed no significant interactions between exercise and HMB on any primary outcomes. The main-effect analyses revealed that exercise improved the usual and maximal gait speed by 0.16 m/s (95% CI: 0.10, 0.21 m/s) and 0.15 m/s (95% CI: 0.09, 0.22 m/s), respectively; the knee extensor and hip adductor strength by 22.0 N (95% CI: 10.1, 33.9 N) and 21.8 N (95% CI: 12.9, 30.7 N), respectively; and timed up-and-go and sit-to-stand time by -0.5 s (95% CI: -0.7, -0.3 s) and -1.7 s (95% CI: -2.1, -1.3 s), respectively, relative to education. HMB improved usual gait speed by 0.06 m/s (95% CI: 0.01, 0.11 m/s) relative to placebo. Most improvements disappeared during the subsequent 12-wk observation period.

CONCLUSIONS

HMB additively improved gait performance with negligible benefit and provided no enhancements in the effects of exercise on other outcomes. Exercise appeared to be the only effective intervention to improve outcomes in older women with low muscle mass.This trial was registered at www.umin.ac.jp/ctr/as UMIN000028560.

How to Increase Muscle Mass in Critically Ill Patients: Lessons Learned from Athletes and Bodybuilders

PURPOSE OF REVIEW

Decades of research on nutrition and exercise on athletes and bodybuilders has yielded various strategies to promote anabolism and improve muscle health and growth. We reviewed these interventions in the context of muscle loss in critically ill patients.

RECENT FINDINGS

For critically ill patients, ensuring optimum protein intake is important, potentially using a whey-containing source and supplemented with vitamin D and leucine. Agents like hydroxyl β-methylbutyrate and creatine can be used to promote muscle synthesis. Polyunsaturated fatty acids stimulate muscle production as well as have anti-inflammatory properties that may be useful in critical illness. Adjuncts like oxandralone promote anabolism. Resistance training has shown mixed results in the ICU setting but needs to be explored further with specific outcomes. Critically ill patients suffer from severe proteolysis during hospitalization as well as persistent inflammation, immunosuppression, and catabolism syndrome after discharge. High protein supplementation, ergogenic aids, anti-inflammatories, and anabolic adjuncts have shown potential in alleviating muscle loss and should be used in intensive care units to optimize patient recovery.

Why Are Masters Sprinters Slower Than Their Younger Counterparts? Physiological, Biomechanical, and Motor Control Related Implications for Training Program Design

Elite sprint performances typically peak during an athlete's 20s and decline thereafter with age. The mechanisms underpinning this sprint performance decline are often reported to be strength-based in nature with reductions in strength capacities driving increases in ground contact time and decreases in stride lengths and frequency. However, an as-of-yet underexplored aspect of Masters sprint performance is that of age-related degradation in neuromuscular infrastructure, which manifests as a decline in both strength and movement coordination. Here, the authors explore reductions in sprint performance in Masters athletes in a holistic fashion, blending discussion of strength and power changes with neuromuscular alterations along with mechanical and technical age-related alterations. In doing so, the authors provide recommendations to Masters sprinters-and the aging population, in general-as to how best to support sprint ability and general function with age, identifying nutritional interventions that support performance and function and suggesting useful programming strategies and injury-reduction techniques.

Leucine metabolites do not induce changes in phase angle, bioimpedance vector analysis patterns, and strength in resistance trained men

We aimed to assess the effects of off-the-shelf leucine metabolite supplements on phase angle (PhA), bioimpedance vector analysis (BIVA) patterns and strength during an 8-week resistance training protocol. Fifty-three male participants were allocated into 4 groups: α-hydroxyisocaproic acid (n = 12, age = 30.9 ± 9.3 years), β-hydroxy-β-methylbutyrate free acid (n = 12, age = 31.0 ± 9.3 years), calcium β-hydroxy-β-methylbutyrate (n = 15, age = 32.1 ± 5.2 years) or placebo (n = 14, age = 28.9 ± 6.6 years). Bioimpedance parameters and 1-repetition maximum (1RM) for back squat and bench press were assessed at baseline and at the end of weeks 4 and 8. Additionally, fat-free mass and fat mass were evaluated by dual-energy X-ray absorptiometry. No statistically group by time interactions were found, even adjusting for age. PhA and vector did not change over the training period, while time-dependent increases were observed for 1RM back squat and 1RM bench press. A direct association was observed between PhA and 1RM bench press changes (whole sample), while PhA and strength were correlated throughout the study, even when adjusting for fat-free mass and percentage of fat mass. Leucine metabolites have no effect on PhA, BIVA patterns or strength during an 8-week resistance training program, in resistance trained subjects. The trial was registered at ClincicalTrials.gov: NCT03511092. Novelty: Supplementation with leucine metabolites is not a supplementation strategy that improves bioelectrical phase angle, cellular health, and strength after an 8-week resistance training program. When consuming a high protein diet, none of the α-hydroxyisocaproic acid, β-hydroxy-β-methylbutyrate free acid, and calcium β-hydroxy-β-methylbutyrate metabolites resulted in an ergogenic effect in resistance trained men.

Supplementation with the Leucine Metabolite β-hydroxy-β-methylbutyrate (HMB) does not Improve Resistance Exercise-Induced Changes in Body Composition or Strength in Young Subjects: A Systematic Review and Meta-Analysis

β-hydroxy-β-methylbutyrate (HMB) is a leucine metabolite that is purported to increase fat-free mass (FFM) gain and performance in response to resistance exercise training (RET). The aim of this systematic review and meta-analysis was to determine the efficacy of HMB supplementation in augmenting FFM and strength gains during RET in young adults. Outcomes investigated were: total body mass (TBM), FFM, fat mass (FM), total single repetition maximum (1RM), bench press (BP) 1RM, and lower body (LwB) 1RM. Databases consulted were: Medical Literature Analysis and Retrieval System Online (Medline), Excerpta Medica database (Embase), The Cumulative Index to Nursing and Allied Health Literature (CINAHL), and SportDiscus. Fourteen studies fit the inclusion criteria; however, 11 were analyzed after data extraction and funnel plot analysis exclusion. A total of 302 participants (18-45 y) were included in body mass and composition analysis, and 248 were included in the strength analysis. A significant effect was found on TBM. However, there were no significant effects for FFM, FM, or strength outcomes. We conclude that HMB produces a small effect on TBM gain, but this effect does not translate into significantly greater increases in FFM, strength or decreases in FM during periods of RET. Our findings do not support the use of HMB aiming at improvement of body composition or strength with RET.