Equivalent Hypertrophy and Strength Gains in HMB or Leucine Supplemented Men

Abstract

Ingestion of proteins with high leucine content during resistance training (RT) can augment hypertrophy. There are data suggesting that a leucine metabolite, β-hydroxy, β-methylbutyrate (HMB), may, however, be substantially more anabolic than leucine. Purpose: We aimed to test whether supplementation with HMB versus leucine, added to whey protein, would result in different muscle hypertrophy and strength gains in young men performing resistance training (RT). Methods: Twenty-six resistance-trained men (23 ± 2 y) performed 12 wk of RT with 3 phases. Phase 1: 8 wk of periodized RT (3 training sessions/wk). Phase 2: 2 wk overreaching period (5 sessions/wk). Phase 3: 2 wk taper (3 sessions/wk). Participants were randomly assigned to twice daily ingestion of: whey protein (25 g) plus HMB (1.5 g) (Whey+HMB; n=13) or whey protein (25 g) plus leucine (1.5 g) (Whey+Leu; n=13). Skeletal muscle biopsies were performed before and after RT. Measures of fat and bone-free mass (FBFM), vastus lateralis (VL) muscle thickness and muscle cross-sectional area (CSA – both by ultrasound), muscle fiber CSA, and 1-repetition maximum (1-RM) strength tests were determined. Results: We observed increases in FBFM, VL muscle thickness, muscle CSA and fiber type CSA and 1-RM strength, with no differences between HMB and leucine at any phase. Furthermore, no differences were observed in hormone concentrations between groups, or in time-by-group interactions in hormone concentrations at any phase of the RT program. Conclusion: HMB did not result in greater increases in any measure of muscle mass, strength, or hormonal concentration compared to leucine during 12 weeks of RT.