Introduction: Previous research has demonstrated that ingestion of essential amino acids and their metabolites induce anabolic effects with the potential to augment gains in lean body mass and strength after resistance exercise training.
Purpose: The purpose of the present study was to examine the effects of an essential amino acid-based formula (Muscle Armor™ (MA); Abbott Laboratories, Abbott Park, IL) containing β-hydroxy-β-methylbutyrate (HMB) on hormonal and muscle damage markers in response to 12 wk of resistance exercise.
Methods: Seventeen healthy men (mean body mass: 77.9 ± 7.2 kg; mean height: 174.3 ± 12.4 cm; mean age: 22.9 ± 3.8 yr) were matched and randomized into two groups and performed 12 wk of periodized heavy resistance training while supplementing with either MA or an isocaloric, isonitrogenous placebo (CON). Every 2 wk during the 12-wk intervention, resting blood draws were obtained, and muscle strength and power were measured. In addition, blood draws were obtained before, during, and after a standardized resistance exercise challenge performed pre-, mid-, and posttraining.
Results: Lean body mass, muscle strength, and muscle power significantly (P ≤ 0.05) increased in both groups after training; however, MA supplementation augmented these responses to a significantly greater extent when compared with the CON group. MA supplementation promoted increases in resting and exercise-induced testosterone and resting growth hormone concentrations. In addition, MA reduced preexercise cortisol concentrations. Throughout the training protocol, MA attenuated circulating creatine kinase and malondealdehyde compared with the CON group, suggesting that MA might have influenced a reduction in muscle damage.
Conclusion: MA supplementation beneficially affected training-induced changes in lean body mass, muscle strength, and power, as well as hormonal responses and markers of muscle damage in response to 12 wk of resistance exercise training when compared with an isonitrogenous control.