Citrulline, arginine, and nitric oxide pathways can be used to enhance performance without the stimulant effects of caffeine.

“there's actually another line of supplementation we can go down here which is not technically a stimulant but it's something I use to help performance when you don't want caffeine and so this think specifically if you're one of those folks who have to exercise at night and you want a little bit of boost for your training but you don't want to have caffeine because it messes up your sleep and this is when you can turn to the whole like citrine Arginine nitric oxide sort of route”