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

• Published in: Medicine and science in sports and exercise Vol. 51; no. 1; pp. 56 - 64
• Main Authors: TEIXEIRA, FILIPE J, MATIAS, CATARINA N, MONTEIRO, CRISTINA P, VALAMATOS, MARIA J, REIS, JOANA F, TAVARES, FRANCISCO, BATISTA, ANA, DOMINGOS, CHRISTOPHE, ALVES, FRANCISCO, SARDINHA, LUÍS B, PHILLIPS, STUART M
• Format: Journal Article
• Language: English
• Published: United States American College of Sports Medicine 01-01-2019
• Subjects: Adolescent; Adult; Athletic Performance - physiology; Biomarkers - blood; Body Composition; Caproates - administration & dosage; Creatine Kinase - blood; Dietary Supplements; Double-Blind Method; Human Growth Hormone - blood; Humans; Hydrocortisone - blood; Insulin-Like Growth Factor I - metabolism; Male; Middle Aged; Muscle Strength - physiology; Muscle, Skeletal - anatomy & histology; Muscle, Skeletal - physiology; Performance-Enhancing Substances - administration & dosage; Resistance Training; Valerates - administration & dosage; Young Adult
• ISSN: 0195-9131; 1530-0315
• DOI: 10.1249/MSS.0000000000001754

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.
PURPOSEWe 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.
METHODSForty 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.
RESULTSTime-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.
CONCLUSIONSNo 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.