Clear Muscle [Discontinued] by MuscleTech Performance Series

POSSIBLY EFFECTIVE

• Sarcopenia. Oral HMB seems to increase muscle mass and may attenuate muscle loss in older adults. However, it may not offer additional benefit when used in conjunction with exercise. Details: Meta-analyses of clinical research as well as individual clinical studies in healthy older adults, including those at risk for sarcopenia, show that HMB supplementation increases muscle mass or fat-free mass when compared with placebo or other control (96645,106027,108771). Furthermore, some clinical research in elderly people with a recent hip fracture who are undergoing rehabilitation shows that a specific liquid nutritional supplement (Ensure Plus Advance, Abbott) providing the calcium salt of HMB (Ca-HMB) 1.5 grams, calcium 500 mg, and calcidiol 500 IU, taken twice daily in addition to standard therapy, attenuates muscle loss, but does not affect function, when compared with standard therapy alone (96640). HMB has also been evaluated in combination with exercise. In a meta-analysis subgroup of healthy, older adults, HMB supplementation combined with exercise did not result in additional increases in fat-free mass when compared with supplementation alone (106027). Similarly, in an individual clinical study in older females at risk for sarcopenia, HMB supplementation did not enhance the effects of exercise on fat-free mass when compared with exercise alone (108770).

POSSIBLY INEFFECTIVE

• Physical performance. Oral HMB, when taken in conjunction with participation in an exercise regimen, does not seem to improve physical performance in older adults. Details: Most clinical research in elderly patients shows that HMB is not beneficial for improving overall physical performance (99245,99249,102869). A meta-analysis of 10 clinical studies in patients 50-80 years of age shows that taking HMB along with physical exercise does not improve muscle strength, physical performance measures, or body composition when compared with physical exercise alone (102869). Conversely, a small clinical study in older adults shows that taking the calcium salt of HMB (Ca-HMB) along with vitamin D for 12 months improves a composite functional index of physical performance at 6 and 12 months, but not at 3 and 9 months, when compared with control. The addition of moderate resistance exercise training 3 times weekly did not further improve the composite functional index among those receiving supplementation (106026).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Athletic performance. It is unclear if oral HMB, alone or in combination with other ingredients, is beneficial for improving performance in athletes at various levels. Details: A small clinical study in elite male rowers shows that taking HMB 1 gram three times daily for 12 weeks increases aerobic capacity and peak anaerobic power when compared with placebo. It also increases the maximum volume of oxygen consumed, compared with a small decrease following intake of placebo. However, anaerobic adaptation does not seem to be improved (99246). HMB has also been evaluated in combination with other ingredients. A small clinical study in adolescent, middle-distance runners aged 14-17 years shows that supplementation with a specific calcium salt of HMB (Ca-HMB) (HMB 1250 Mega Caps, Olimp Laboratories) 2.5 grams along with L-arginine alpha-ketoglutarate (AAKG 1250 Extreme Mega Caps, Olimp Laboratories) 2.5-3.75 grams, taken 3 times daily, attenuates reductions in countermeasure jump height during a 12-day intensive training camp when compared with placebo (106032). Conversely, a very small clinical study in male collegiate rugby players shows that supplementation with HMB along with creatine monophosphate for 6 weeks does not improve maintenance of performance and body composition when compared with creatine monophosphate alone (106031). Changes in markers of muscle damage and stress were similar between groups in both studies (106031,106032).
• Cachexia. Oral HMB has only been evaluated in combination with other ingredients; its effects when used alone is unclear. Details: A small clinical study in patients with cancer-related cachexia shows that taking HMB 3 grams daily in combination with arginine 14 grams and glutamine 14 grams daily in two divided doses for up to 24 weeks increases body weight and lean body mass by about 1 kg, compared with reduced body weight and lean body mass in those taking placebo (52280). Conversely, a small clinical study in patients with cachexia due to rheumatoid arthritis (RA) shows that taking this combination for 12 weeks does not improve body weight or lean body mass when compared with placebo (52340).
• Cirrhosis. It is unclear if oral HMB is beneficial in patients with liver cirrhosis. Details: A small clinical study in patients with liver cirrhosis shows that taking HMB 3 grams daily for 12 weeks improves muscle mass and some measures of muscle function when compared with baseline (108768). The lack of statistical comparison to placebo limits the validity of these findings. Additionally, it should be noted that the groups were unmatched at baseline in terms of cirrhosis etiology and liver frailty index.
• Critical illness (trauma). It is unclear if a calcium salt of HMB (Ca-HMB) can reduce muscle wasting in critically ill adults. Details: A small clinical study in patients with severe critical illness receiving mechanical ventilation shows that taking Ca-HMB 1.5 grams twice daily, beginning on day 4 of admission and continuing for 10-30 days, does not reduce muscle wasting when compared with placebo (108769).
• Diabetic foot ulcers. Oral HMB has only been evaluated in combination with other ingredients; its effects when used alone is unclear. Details: A clinical study in patients with diabetic foot ulcers shows that drinking a specific beverage (Juven/Abound, Abbott Nutrition) containing HMB 1.2 grams, L-arginine 7 grams, and L-glutamine 7 grams twice daily for 16 weeks does not improve wound healing when compared with placebo (96637).
• Exercise-induced muscle damage. It is unclear if oral HMB is beneficial for reducing exercise-induced muscle damage. Details: A small clinical study in resistance trained males shows that taking a free acid form of HMB (HMB-FA) 1 gram prior to a high-volume resistance training session, and then 2 grams in divided doses later that day, attenuates an increase in creatine kinase levels when compared with placebo. Also, perceived recovery 48 hours after exercise was approximately 38% higher than placebo (99250). Conversely, a very small clinical study in elite male rowers shows that taking HMB 3 grams within 30 minutes after each training session and 30 minutes before bed on non-training days for 10 weeks does not reduce markers of exercise-induced muscle damage, including aspartate aminotransferase, lactate dehydrogenase, and creatine kinase, when compared with placebo (102871).
• Exercise-induced muscle soreness. Small clinical studies suggest that oral HMB does not improve exercise-induced muscle soreness in trained and untrained males. Details: One small clinical study in resistance-trained males shows that taking a specific free acid form of HMB (HMB-FA) (Clear Muscle, Muscle Tech) or a specific calcium salt of HMB (Ca-HMB) (HMB, Millennium Sport Technologies, Inc.) 1 gram three times daily for 12 weeks does not improve participant ratings of delayed onset muscle soreness when compared with placebo (102872). Another small clinical study in untrained males participating in a resistance training program shows that taking HMB 3 grams daily for 2-4 weeks prior to resistance training does not reduce muscle soreness when compared with placebo (102873).
• HIV/AIDS-related wasting. Oral HMB has only been evaluated in combination with other ingredients; its effects when used alone is unclear. Details: A small clinical study in patients with AIDS-related wasting shows that taking HMB 3 grams in combination with arginine 14 grams and glutamine 14 grams daily in two divided doses for 8 weeks seems to increase body weight and lean body mass and possibly improve immune function when compared with placebo (1909).
• Kidney failure. It is unclear if oral HMB reduces the incidence of complications in patients with kidney failure receiving maintenance hemodialysis. Details: A small clinical study in patients on maintenance hemodialysis shows that taking HMB 3 grams daily for 6 months does not affect body composition, bone density, muscle strength, or physical function, when compared with placebo (99255). The validity of this study is limited by its small size and low rate of adherence.
• Malnutrition. It is unclear if an oral calcium salt of HMB (Ca-HMA) is beneficial in patients with, or at risk of, malnutrition. Details: A large clinical trial in older, community-dwelling adults at medium to high risk for malnutrition who are receiving dietary counseling shows that taking an oral nutrition supplement containing Ca-HMB 0.74 grams twice daily results in achievement of the goal outcome in 33% of patients, compared with 9% of those receiving placebo. The goal outcome was a composite of survival without hospital admission or readmission and at least 5% weight gain at 6 months. Ca-HMB supplementation also resulted in significant improvements in various nutritional and functional outcomes (106028). A retrospective study in patients with or at risk of malnutrition receiving dietary and exercise counseling shows that supplementation with an oral nutrition supplement(Ensure Plus Advance, Abbott Nutrition) containing Ca-HMB 1.5 grams twice daily for 3-6 months seems to improve anthropometrics and body composition when compared with baseline (108772). The validity of this finding is limited by the lack of statistical comparison to those taking a standard oral nutrition supplement.
• Muscle strength. The benefits of HMB for improving muscle strength seem to depend on the physical fitness of the individual. Although small clinical studies suggest HMB may be modestly beneficial in untrained adults, most research has shown no benefit in trained adults. Details: A meta-analysis of 11 studies in a mixed population of both trained and untrained healthy adults shows that HMB does not increase muscular strength outcomes or improve body composition when compared with placebo (106030). However, research in specific populations suggests that benefits may differ depending on baseline training level. Most research in previously untrained individuals seems to show that HMB offers a modest benefit on muscle strength (11003,96642,96643). Some preliminary clinical research shows that HMB might increase strength and body composition and reduce muscle damage when used during resistance training or intense endurance exercises (1929,2168,10062,55821,102873). A meta-analysis of clinical studies in mostly untrained males shows that taking HMB 3 grams daily can modestly increase lean body mass by 0.3% and strength by 1.4% weekly (21446). Another meta-analysis assessing untrained weightlifters shows that taking HMB results in small increases in upper body strength, but not lower body strength, when compared with control (96642). Another small clinical study in untrained males participating in a 12-week training program not included in the above meta-analyses shows that taking calcium HMB 1 gram three times daily does not increase muscle strength or reduce fat mass, but might increase fat-free mass in the legs, when compared with placebo (102870). Conversely, most research in trained athletes shows that salt formulations of HMB do not increase muscle strength, improve body composition, or reduce muscle damage (2167,55820,55825,55826,55831,96638,96641,96643,102872,102874). A small clinical study in resistance trained males shows that taking HMB 1 gram three times daily for 9 weeks does not increase muscle strength or lean mass overall, but does increase lower body strength by approximately 9%, when compared with placebo (99251). However, this finding has not been supported in other research in previously trained athletes (96642). Research using the free acid form of HMB (HMB-FA) has shown some benefit in previously trained males. A small clinical study in this population shows that taking HMB-FA 1 gram three times daily for 12 weeks increases muscle strength approximately three-fold when compared with placebo. There is also an approximate 90% prevention of muscle strength loss during a two-week overtraining phase when compared with placebo, as well as improvements in lean body mass and muscle power (99248).
• Muscle fatigue. It is unclear if oral HMB is beneficial for reducing muscle fatigue in trained males. Details: A small clinical study in trained males shows that taking a free acid form of HMB, 3 grams as a single dose, prior to a muscle damage protocol returns work capacity to pre-exercise levels within 24 hours, compared with more than 72 hours with placebo. However, there was no effect on other measures of muscle recovery (99253).
• Obesity. It is unclear if oral HMB is beneficial for reducing abdominal adiposity. Details: A small clinical study in elderly males shows that taking HMB 1.5 grams twice daily for 12 weeks while undergoing a resistance training program reduces abdominal adiposity by approximately 9.5% when compared with either the resistance exercise program alone, HMB alone, or placebo (99247). Another small clinical study in postmenopausal adults with overweight or obesity shows that taking a specific product (Abound, Abbott) containing a calcium salt of HMB (Ca-HMB), L-arginine, and L-glutamine twice daily for 4 weeks reduces visceral adipose tissue by 94 grams, compared with an increase of 60 grams in those taking placebo (108773). It is unclear if this effect is due to HMB, the other ingredients, or the combination.
• Oral mucositis. Oral HMB has only been evaluated in combination with other ingredients; its effects when used alone is unclear. Details: A small clinical study in patients with head and neck cancer undergoing chemoradiotherapy shows that taking a specific product (Abound, Abbott) containing HMB 1.2 grams, arginine 7 grams, and glutamine 7 grams in water twice daily during treatment does not reduce the incidence of moderate to severe functional changes from oral mucositis when compared with baseline (99243). The validity of this finding is also limited by the lack of a comparator group and the use of subjective measures.
• Postoperative recovery. Oral HMB has only been evaluated in combination with other ingredients; its effects when used alone is unclear. Details: A small clinical study in patients with abdominal malignancies shows that taking a specific product (Abound, Abbott) containing HMB 1.2 grams, arginine 7 grams, and glutamine 7 grams in water once daily for ten days, starting three days prior to surgery, does not reduce the incidence of wound complications or length of hospitalization when compared with placebo (99413).
• Radiation dermatitis. Oral HMB has only been evaluated in combination with other ingredients; its effects when used alone is unclear. Details: A small clinical study in patients with head and neck cancer undergoing chemoradiotherapy shows that taking a specific product (Abound, Abbott) containing HMB 1.2 grams, L-arginine 7 grams, and L-glutamine 7 grams in water twice daily, starting on the first day of chemoradiotherapy and continuing for up to 1 week after completing therapy, does not reduce the incidence of grade 3 dermatitis when compared with control (96639). More evidence is needed to rate HMB for these uses.

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POSSIBLY SAFE ...when used orally and appropriately. Doses up to 3 grams or 76 mg/kg daily for up to one year have been used with apparent safety (1909,2167,2168,3374,46606,55820,55822,96637,96645,99248)(99249,102872). The International Society of Sports Nutrition states that chronic use of HMB is safe for young and old patients (96644).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

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General ...Orally, HMB seems to be well tolerated.

Cardiovascular ...Orally, high blood pressure has been reported in one person taking HMB in a clinical trial (108770).

Dermatologic ...Orally, itching has been reported in two people taking HMB in clinical trials (99245,102872).

Gastrointestinal ...Orally, abdominal pain, constipation, dyspepsia, flatulence, heartburn, and nausea have been reported rarely in people taking HMB in clinical trials (99245,102872,108770).

Genitourinary ...Orally, increased urinary frequency has been reported in two people taking HMB in a clinical trial (108770).

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