But what do they actually do?
Quite a lot, it turns out. Taking an EAA supplement can improve muscle growth, increase your endurance, and reduce soreness post exercise. In other words it helps you get back to the gym faster and happier.
It’s not the workouts that build muscle; it’s the opposite. When training we are in fact damaging our muscle fibers. It’s only in the hours following the workout when your body repairs itself in a process known as Muscle Protein Synthesis. 
This process helps us come back even stronger. Taking an EAA—along with sound nutrition and restful sleep—will boost the repair process. Think of Popeye after he eats his spinach. You can take on Bluto no probs.
EAAs change the way your body uses the main two fuel sources: carbs and fats. In workouts we see at Redleaf and in many other forms of exercise we need to sustain short energy bursts. But this depletes an essential energy store known as glycogen. Taking an EAA supplement and you can persuade your body to burn fat instead of the magical glycogen in a process called lipid oxidation. 
As well, taking EAAs before, during, or after exercise may reduce the dreaded DOMS. Clinically known as Delayed Onset Muscle Soreness, this is a fancy name for the aches and pains that haunts you for days after an intense workout .
In particular a trio of BCAAs, isoleucine, leucine and valine—found within EAAs—impact how you deal with DOMS. [3,4] But ingesting extra dollops of these good buddies will help your banish the soreness and get back to the gym, hitting the floor with a grin rather than a grimace. Yet it’s not the whole story.
There are many supplements available that isolate the BCAAs. You might think it would be easier just to zero in on the aches and pains of your body. But it’s not that simple. BCAAs are incomplete because they don’t provide other essential amino acids needed for growth and repair.
The simplest way to think about them is BCAA protects muscles and EAA builds muscles. Kind of like Hans Solo and Chewbaca—one heck of a team.
So what you should do is take a really great EAA that boosts and protects you during your challenging workouts. Research shows 10 to 20 grams is optimal. Take an EAA before and during your workouts and get ready to improve muscle growth, increase your endurance, and reduce soreness post exercise.