Introduction
Several acute studies have suggested that leucine is a key amino acid to drive muscle protein synthesis. However, there are very few studies on the long-term effects of leucine supplementation on resistance training (RT)–induced gains in muscle mass and strength. We sought to determine the impact of 10 g of leucine on muscle mass and strength in response to RT in healthy young men.
Methods
Twenty-five, resistance-trained men (27 ± 5 yr; 78.4 ± 11.6 kg; 24.8 ± 3.0 kg·m−2) consuming 1.8 ± 0.4 g protein·kg−1·d−1, were randomly assigned to receive 2 × 5 g·d−1 supplementation of either free leucine (LEU n = 12) or alanine (PLA n = 13) while undergoing a supervised 12-wk, twice-weekly lower-limb RT program. One-repetition maximum (leg-press 1RM) and muscle cross-sectional area (mCSA) of the vastus lateralis were determined before (PRE) and after (POST) the intervention. Additionally, three 24-h dietary recalls were also performed at PRE and POST.
Results
Protein intake was roughly double that of the RDA in both groups and remained unchanged across time with no differences detected between groups. Similar increases were observed between groups in leg-press 1RM (LEU, 19.0% ± 9.4% and PLA, 21.0% ± 10.4%, P = 0.31) and mCSA (LEU, 8.0% ± 5.6% and PLA, 8.4% ± 5.1%, P = 0.77).
Conclusions
High-dose leucine supplementation did not enhance gains in muscle strength and mass after a 12-wk RT program in young resistance-trained males consuming adequate amounts of dietary protein.
The aim of this study was to compare the potential additional effect of chia flour, whey protein, and a placebo juice to resistance training on fat-free mass (FFM) and strength gains in untrained young men. Eighteen healthy, untrained young men underwent an 8-week whole-body resistance training program, comprising three sessions per week. Subjects were randomized into three groups that after each training session consumed: (1) 30 g whey protein concentrate containing 23 g protein (WG), (2) 50 g chia flour containing 20 g protein (CG), or (3) a placebo not containing protein (PG). Strength tests (lower- and upper-limb one repetition maximum (1 RM) tests) and body composition analyses (dual-energy X-ray absorptiometry; DXA) were performed before (PRE) and after (POST) the intervention. Resistance training increased FFM and the 1 RM for each of the strength tests similarly in the three groups. FFM increased by 2.3% in WG (p = 0.04), by 3.6% in CG (p = 0.004), and by 3.0% in PG (p = 0.002)., and 1 RM increased in the different strength tests in the three groups (p < 0.05) with no difference between PG, CG, and WG. In conclusion, neither chia flour nor whey protein supplementation elicited an enhanced effect on FFM and strength gains after an 8-week resistance training program in healthy, untrained young men consuming a habitual high protein mixed diet (>1.2 g/kg/day).
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