Leucine Metabolites Do Not Enhance Training-induced Performance or Muscle Thickness

Leucine metabolites, α-hydroxyisocaproic acid (α-HICA) and β-hydroxy-β-methylbutyrate (calcium, HMB-Ca and free acid, HMB-FA), have been proposed to augment resistance training-induced changes in body composition and performance. PURPOSE We aimed to conduct a double-blind randomized controlled pragmatic trial to evaluate the effects of off-the-shelf leucine metabolite supplements of α-HICA, HMB-FA and HMB-Ca, on resistance training-induced changes in muscle thickness, and performance. METHODS Forty men were randomly assigned to receive α-HICA (n=10, fat-free mass [FFM]=62.0 ± 7.1 kg), HMB-FA (n=11, FFM=62.7 ± 10.5 kg), HMB-Ca (n=9, FFM=65.6 ± 10.1 kg), or placebo (PLA; n=10, FFM=64.2 ± 5.7 kg). The training program consisted of whole body thrice weekly resistance training for 8wk (7 exercises/session, 3–4 sets per session, at 70-80% 1RM). Skeletal muscle thickness by ultrasound, performance measures, and blood measures (creatine kinase [CK], insulin-like growth factor 1 [IGF-1], growth hormone [GH], cortisol and total testosterone) were evaluated at baseline and at the end of weeks 4 and 8. RESULTS Time-dependent changes were observed for muscle thickness (p

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