The Effects of Leucine Metabolites in Performance, Body Composition and Biochemical Markers of Muscle Damage

Overview

This study aimed to conduct a double-blind randomized pragmatic trial to evaluate the effects of off-the-shelf leucine metabolite supplements HMB-FA, HMB-Ca, alfa-HICA, on resistance training-induced changes in body composition, performance and biochemical markers of muscle damage. The investigators' working hypothesis is that so long as subjects adhered to a diet containing adequate energy and dietary protein, there would be no differences between those receiving the leucine metabolites - HMB-FA, HMB-Ca and alfa-HICA - when compared to a placebo consuming group.

This was a randomized, double blind, placebo-controlled study with additional control of diet. The investigators compared the effect of 8 weeks of supplementation with HMB-FA, HMB-Ca, or alfa-HICA on performance, body composition, and biochemical markers of muscle damage. The study involved fifty-three participants engaged in resistance training for at least one year (≥3 training sessions per week). Performance measures - To evaluate aerobic performance an incremental test to volitional exhaustion was performed. Peak power and strength was assessed by maximum strength and the participants also performed a Wingate and vertical jump tests. Perceived performance and recovery was measured by the perceived recovery status scores in training days. This tool allowed to evaluate both fatigue, general muscle soreness, sleep quality, stress levels and mood throughout the study. Performance tests were performed at baseline, prior to the beginning of the study, and at the end of weeks 4 and 8, in a fed state (a meal replacement bar was provided to participants before the tests). Body composition measures - To evaluate body composition a dual-energy X-ray absorptiometry (DXA) scan was performed; Muscle thickness was measured by ultrasonography; Total body water and both the extracellular water and intracellular water were assessed by bioelectrical impedance spectroscopy (BIS). These tests were performed at baseline and at the end of weeks 4 and 8, with participants reporting to the lab in a fasted state, refraining from exercise, alcohol or stimulant beverages for at least 8 h. Biochemical markers of muscle damage - To assess biochemical markers (total testosterone and cortisol, creatine kinase, insulin-like growth factor 1, growth hormone), blood was collected at baseline and at the end of weeks 4 and 8, in a fasted state with participants also refraining from exercise, alcohol or stimulant beverages for at least 12 h. Training protocol - The training program was designed according to the guidelines for hypertrophy type of resistance training for intermediate-trained individuals and consisted on 3 sessions per week during an 8-week period. Statistics - sample size was calculated through an a priori power analysis (G\*Power Version 3.1.9.2, Heinrich Heine Universitat Dusseldorf, Germany), based on FFM changes from previous studies and power of 0.80. Statistical analysis will be performed using IBM SPSS statistics version 22.0 (IBM, Chicago, Illinois, USA). Normality of the distribution of variables will be tested by Shapiro-Wilk test. Baseline characteristics between groups were analyzed by a 1-way analysis of variance (ANOVA) since normality was observed. Time and time x group interactions will be evaluated by repeated-measures ANOVA. The equality of the matrix of variance and sphericity will be explored with the Levene F test and Mauchly's test, respectively. Overall significance level for α was set at p ≤ 0.05.