Muscled guy lifting plateL-Leucine is one of the branched chain amino acids which is often supplemented with either by itself or along with the other branched chain amino acids to increase strength and muscle gains and improve recovery from intense training. L-Leucine is believed to be important in signaling muscle building.

A study evalutating l-leucine supplementation for strength and muscle gains found that it did help to increase strength. The study included 26 men 20-36 years old who had no prior strength training experience. Half of the participants took 4g l-leucine daily, and the other half took a placebo supplement. All participants took part in a resistance training program including 8 different machine exercises. After 12 weeks of supplementation, the improvement in 5 rep maximum weight of all 8 exercises was measured. They found that while the placebo group increased the sum of their 5 rep max weights by about 31%, the group taking l-leucine increased the sum of their 5 rep max weights by 41%. They found no significant difference between the groups in changes in body composition.

This study definitely gives some evidence for the effectiveness of l-leucine for increasing strength gains, but it is odd that there was no significant between-group differences in body composition change. This may have to do with the fact that the participants were previously untrained, so their body composition likely made some big changes during the 12 week period which could throw off the results. A study done on elite athletes would likely yield more applicable results, but this is still evidence in favor of l-leucine supplementation for improved strength gains from weight training.



Ispoglou T, King RF, Polman RC, & Zanker C. (2011). Daily L-leucine supplementation in novice trainees during a 12-week weight training program. International Journal of Sports Physiology and Performance. 6(1), 38-50.

ABOUT THE AUTHOR: Cassie is a chemistry major and national level bodybuilder. Questions or comments? Talk to Cassie on the FORUM or on FACEBOOK.

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