Free leucine supplementation during an 8-week resistance training program does not increase muscle mass and strength in untrained young adult subjects.
Study Goal
The researchers aimed to determine whether free leucine supplementation enhances muscle mass and strength gains during resistance training in untrained young adults.
Results Summary
The study found no significant difference in muscle strength or cross-sectional area between the leucine and placebo groups after 8 weeks of resistance training, indicating leucine supplementation did not enhance these outcomes. Dietary intake remained similar between groups, suggesting adequate protein intake may negate additional leucine benefits.
Population
Healthy, untrained young adults (22 ± 2 years).
Effective Dosage
3.0 g/day of leucine, administered as a single post-training dose.
Duration
8 weeks.
Interactions
None mentioned.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
free leucine supplementation | no change | muscle strength | healthy young subjects consuming adequate dietary protein intake | - | does not increase | #1 |
free leucine supplementation | no change | CSA | healthy young subjects consuming adequate dietary protein intake | - | does not increase | #2 |
resistance training program | increase | muscle strength (Leg press) | previously untrained, young subjects | +33% | improvement in | #3 |
resistance training program | increase | muscle strength (knee extension) | previously untrained, young subjects | +31% | improvement in | #4 |
resistance training program | increase | CSA (VL) | previously untrained, young subjects | 8.9% | improvement in | #5 |
resistance training program | increase | CSA (RF) | previously untrained, young subjects | +21.6% | improvement in | #6 |
placebo supplementation | increase | muscle strength (Leg press) | previously untrained, young subjects | +37% | improvement in | #7 |
placebo supplementation | increase | muscle strength (knee extension) | previously untrained, young subjects | 34% | improvement in | #8 |
placebo supplementation | increase | CSA (VL) | previously untrained, young subjects | 9.6% | improvement in | #9 |
placebo supplementation | increase | CSA (RF) | previously untrained, young subjects | +16.4% | improvement in | #10 |
free leucine supplementation | no change | daily dietary intake | LEU and PLA groups | - | no significant difference in | #11 |
The purpose of this study was to examine the effects of free leucine supplementation on changes in skeletal muscle mass and strength during a resistance training (RT) program in previously untrained, young subjects. In a double-blind, randomized, placebo-controlled study, 20 healthy young (22 ± 2 years) participants were assigned to two groups: a placebo-supplement group (PLA, N = 10) or a leucine-supplement group (LEU, N = 10). Both groups underwent an 8-week hypertrophic RT program (2 days/week), consuming an equivalent amount of leucine (3.0 g/day in a single post-training dose) or placebo (cornstarch). Quadriceps muscle strength, cross-sectional area (CSA) of the vastus lateralis (VL), and rectus femoris (RF), as well as the habitual dietary intake were assessed before and after the 8-week intervention period. There was a similar improvement in muscle strength (Leg press, LEU: +33% vs. PLA: +37%; P > 0.05, and knee extension, LEU: +31% vs. PLA: 34%; P > 0.05) and CSA (VL, LEU: 8.9% vs. PLA: 9.6%; P > 0.05, and RF, LEU: +21.6% vs. PLA: + 16.4%; P > 0.05) in the both groups from pre- to post-training. In addition, there was no significant (P > 0.05) difference in daily dietary intake between the LEU and PLA groups before and after the intervention period. Free leucine supplementation (3.0 g/day post-training) does not increase muscle strength or CSA during RT in healthy young subjects consuming adequate dietary protein intake.