Abstract
Background: β-Hydroxy-β-methylbutyrate-free acid (HMB-FA) has been ingested prior to exercise to reduce muscle damage, however the effects of HMB-FA supplementation on hormonal, strength and power adaptation are unclear. Methods: Sixteen healthy men were matched and randomized into two groups and performed six-week resistance training while supplementing with either HMB-FA or placebo (3 g per day). The subjects were evaluated for 1 repetition maximum (1RM) bench press and leg press and vertical jump (VJ) prior to and after training intervention. In addition, blood samples were obtained before and after resistance training to evaluate resting growth hormone (GH), insulin like growth factor 1 (IGF-1), testosterone (TEST), cortisol (CORT), and adrenocorticotropic hormone (ACTH) responses. The HMB-FA supplementation group showed greater gains compared with the placebo group in peak power (effect size ES = 0.26 vs. 0.01) and 1RM leg press (ES = 1.52 vs. 0.96). In addition, the HMB-FA supplementation group indicated greater decrements in ACTH and CORT responses to training in comparison to the placebo group (p < 0.05). Likewise, in GH (ES = 1.41 vs. 0.12) and IGF-1 (ES = 0.83 vs. 0.41), the HMB-FA indicated greater training effects when compared with the placebo group. Conclusions: These findings provide further support for the potential anabolic benefits associated with HMB-FA supplementation.
Highlights
Resistance training is one of the best training modalities to enhance muscle strength, power and hypertrophy [1]
Regarding critical roles of muscle strength and power to succeed in sport [25], many studies examined the effects of resistance training on strength and power performance and reported that resistance training can improve strength performance and enhance the ability to express high power outputs during jumping movements [21,25,26], which are in line with our findings
With review of hormonal changes (Table 2), these results suggest that Hydroxy-β-methylbutyrate-free acid (HMB-FA) may affect growth hormone/ insulin like growth factor 1 (GH/IGF-1) axis signaling; the effect on skeletal muscle protein synthesis requires more investigation
Summary
Resistance training is one of the best training modalities to enhance muscle strength, power and hypertrophy [1]. Activation of muscle fibers to produce maximal force needs some events including elevation of protein synthesis, activation of satellite cells, muscle cell signaling pathways and hormone responses [1,2]. These events can promote capability of force production and strength development [3]. HMB is a metabolite of the amino acid leucine, a potent stimulus of translation initiation and protein synthesis [8], and several studies indicated that HMB could enhance muscle size and strength performance [7,9], elevate anabolic hormones [10]
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