Understanding Branched-Chain Amino Acids

BCAAs: What They Do

The essential amino acids leucine, isoleucine, and valine collectively form what is referred to as the branched-chain amino acids (BCAAs). These amino acids are essential because they cannot be produced in the body and must be provided through supplementation or diet.

BCAAs comprise approximately 30% of the total muscle protein pool and are the primary amino acids oxidized in the muscle during exercise and catabolic stress. For these reasons, athletes supplement with BCAAs to support increased muscle mass, reduced muscle damage, blunting fatigue, and increased energy during exercise.

LEUCINE

Leucine is one of the essential BCAAs. By itself, it can stimulate muscle protein synthesis, the process responsible for muscle growth and recovery. This is why it is often referred to as the "main" amino acid.

Supplementation with at least 2 grams daily of leucine has been shown to decrease muscle soreness, lessen recovery time between workouts, and increase lean muscle mass.

ISOLEUCINE

Isoleucine, like leucine, is another BCAA that can stimulate muscle protein synthesis but to a lesser extent when not combined with the other BCAAs. However, isoleucine significantly increases glucose uptake and the use of glucose during exercise, leading to greater energy production.

Isoleucine may also play a role in the fat-burning abilities of BCAAs.

VALINE

Valine, the third BCAA, supports muscular endurance and decreases fatigue during exercise.

When exercising, tryptophan is converted to serotonin and signals the brain that the body is fatigued—ultimately leading to a decrease in muscle strength and endurance.

Since valine competes with tryptophan for entry into the brain and prevails, less serotonin gets to the brain, which ultimately leads to stronger muscular contractions, quicker recovery between sets, and prolonged muscular strength and endurance.

 

Backed by Studies

Studies exist on the ergogenic benefits of BCAAs. Most of them show that BCAAs, whether consumed throughout the day or pre, during, or post-exercise, decrease protein catabolism (breakdown) and support muscle protein synthesis, a physiological process responsible for muscle growth and repair. Furthermore, BCAAs are vitally important to glucose (energy) production, contributing to more than 40% of glucose production during sustained endurance exercises.

A study done in 2009 found that subjects who were supplemented with BCAAs while following an 8-week resistance training program had a greater decrease in body fat, an increase in lean mass, and greater strength gains on the bench press and squat compared to the non-BCAA group.