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Leucine Metabolites Do Not Enhance Training-induced Performance or Muscle Thickness
Filipe J Teixeira 1, Catarina N Matias 1 2 3, Cristina P Monteiro 1 3, Maria J Valamatos 3 4, Joana F Reis 1 3 5, Francisco Tavares 6, Ana Batista 1, Christophe Domingos 1, Francisco Alves 1 3, Luís B Sardinha 2 3, Stuart M Phillips 7
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PMID: 30102677 DOI: 10.1249/MSS.0000000000001754
Erratum in
Corrigendum.
[No authors listed]
Med Sci Sports Exerc. 2021 Jan;53(1):247. doi: 10.1249/MSS.0000000000002556.
PMID: 33323831 No abstract available.
Abstract
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 8 wk (seven exercises per session, three to four sets per session, at 70%-80% one repetition maximum). Skeletal muscle thickness by ultrasound, performance measures, and blood measures (creatine kinase, insulin-like growth factor 1, growth hormone, 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 < 0.001), one repetition maximum bench press and squat (P < 0.001), Wingate peak power (P = 0.02), countermovement jump height (P = 0.03), power (P = 0.006), creatine kinase, insulin-like growth factor-1, growth hormone, and cortisol (all P < 0.001). No significant between-group or time-group interactions were observed.

Conclusions: No leucine metabolite resulted in any ergogenic effects on any outcome variable. Supplementation with leucine metabolites-α-HICA, HMB-FA, or HMB-Ca-is not a supplementation strategy that improves muscle growth and strength development in young adult men.