LEUCINE IS KING
Leucine acts much like a key to the ignition of a car. The car, in this case, is a muscle cell or fiber. The ignition turns on the process of muscle protein synthesis (MPS), which builds up the muscle protein that leads to more muscle growth. In more "science-y" terms, leucine activates a complex called mTOR, which ramps up muscle protein synthesis and therefore muscle growth.
"RESEARCH SUGGESTS THAT PEOPLE WHO ADD EXTRA LEUCINE TO THEIR POST-WORKOUT PROTEIN AND CARBS EXPERIENCED SIGNIFICANTLY GREATER MUSCLE PROTEIN SYNTHESIS THAN THOSE JUST GETTING PROTEIN AND CARBS."
Research suggests that people who add extra leucine to their post-workout protein and carbs experienced significantly greater muscle protein synthesis than those just getting protein and carbs. Because leucine is so critical for muscle growth, you want to make sure you use a BCAA product that has more leucine than its counterparts, isoleucine and valine.
THE RIGHT RATIO
I recommend you go with a BCAA product that uses a 2:1:1 ratio of leucine to isoleucine and valine. Many products bump up the ratio much higher in favor of leucine, with some coming in at an 8:1:1 ratio and some hitting a 10:1:1 ratio. Many people assume that, given leucine's critical role in muscle growth, a BCAA product with a 10:1:1 ratio is five times better than one with a 2:1:1 ratio. But, before you go spend your hard-earned cash on these supposedly superior BCAA products, hear me out.
The most critical time to take BCAAs is around your workouts, whether you take them before, during, or after. (And yes, that's in addition to the BCAA-rich protein shake you should also be drinking.) One reason for this is that you want ample leucine to instigate muscle protein synthesis. It's this fact that leads many people to assume that the highest ratio is best.
Some products even suggest you should forgo the other two BCAAs and just take leucine. That is a big mistake. To back it up, one study pitted leucine by itself against all three BCAAs in a 2:1:1 ratio. Scientists from Baylor University gave college-aged men either a leucine supplement, a 2:1:1 BCAA supplement, or a placebo before and after a leg workout. They discovered that while leucine increased MPS after the workout better than the placebo did, the BCAAs increased protein synthesis even better than leucine and the placebo. That's one reason for sticking with a 2:1:1 ratio (or something close to it) when supplementing with BCAAs.
Another reason to use a 2:1:1 BCAA supplement is to increase energy and lessen fatigue. BCAAs are used directly by muscle fibers as a fuel source. This is especially true during intense exercise, such as weight training. Numerous studies suggest that supplementing with BCAAs before exercise promotes muscle endurance. More importantly, the BCAAs help reduce fatigue during workouts. And this comes down to the role that valine plays in the body.
During exercise, tryptophan is taken up by the brain in large amounts. Tryptophan is converted in the brain to 5-hydroxytryptamine (5-HT), better known as serotonin. Having higher serotonin levels during exercise signals the brain that the body is fatigued. This leads to a reduction in muscle strength and endurance. Valine competes with tryptophan for entry into the brain. Typically, valine wins.
This means that when you take the BCAA valine before and/or during workouts, less tryptophan gets into the brain to get converted to serotonin. This allows your muscles to contract with more force for a longer time before getting fatigued. In other words, you can crank out more reps in the gym, recover quicker between sets, and maintain better strength and endurance in the later portion of your workouts. Valine can also help you to stay more alert and keep your brain sharper during the day when you aren't working out.
For these reasons, I recommend sticking to a 2:1:1 ratio of leucine to isoleucine and valine when supplementing with BCAAs before, during, and/or after training.