/b/sixpacksmackdown/posts/what-is-l-arginine-and-what-does-l-arginine-do-know-your-pre-workout-supplement-ingredients If you're taking any sort of preworkout supplement odds are it contains an amino acid called L-arginine. If you've never looked at the label or wondered what does L-arginine do - it's time to take a minute and learn about the substances y...en-USTelligent Community 11 Non-Production