The effects of 12 weeks of beta-hydroxy-beta-methylbutyrate free acid supplementation on muscle mass, strength, and power in resistance-trained individuals: a randomized, double-blind, placebo-controlled study

Studies utilizing beta-hydroxy-beta-methylbutyrate (HMB) supplementation in trained populations are limited. No long-term studies utilizing HMB free acid (HMB-FA) have been conducted. Therefore, we investigated the effects of 12 weeks of HMB-FA supplementation on skeletal muscle hypertrophy, body composition, strength, and power in trained individuals. We also determined the effects of HMB-FA on muscle damage and performance during an overreaching cycle. A three-phase double-blind, placebo- and diet-controlled randomized intervention study was conducted. Phase 1 was an 8-week-periodized resistance-training program; Phase 2 was a 2-week overreaching cycle; and Phase 3 was a 2-week taper. Muscle mass, strength, and power were examined at weeks 0, 4, 8, and 12 to assess the chronic effects of HMB-FA; and assessment of these, as well as cortisol, testosterone, and creatine kinase (CK) was performed at weeks 9 and 10 of the overreaching cycle. HMB-FA resulted in increased total strength (bench press, squat, and deadlift combined) over the 12-week training (77.1 +/- A 18.4 vs. 25.3 +/- A 22.0 kg, p < 0.001); a greater increase in vertical jump power (991 +/- A 168 vs. 630 +/- A 167 W, p < 0.001); and increased lean body mass gain (7.4 +/- A 4.2 vs. 2.1 +/- A 6.1 kg, p < 0.001) in HMB-FA- and placebo-supplemented groups, respectively. During the overreaching cycle, HMB-FA attenuated increases in CK (-6 +/- A 91 vs. 277 +/- A 229 IU/l, p < 0.001) and cortisol (-0.2 +/- A 2.9 vs. 4.5 +/- A 1.7 mu g/dl, p < 0.003) in the HMB-FA- and placebo-supplemented groups, respectively. These results suggest that HMB-FA enhances hypertrophy, strength, and power following chronic resistance training, and prevents decrements in performance following the overreaching.