It helps with breathing and gives you energy as it's a stimulant and it is an asthma medication. However, from my personal experience, the side affects can be so bad that it can stop you from having a good workout. You have to dose it intelligently and also, I would not suggest doing cardio or weight lifting right after taking a dose. I'd give it a few hours for the side affects to cool down. Everybody reacts differently though so the only way to know is to try it. Some love it and some hate it.
ECA is safer and more predictable.