system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: do workout supplements (such as pre-workout that claims to increase the ability of your blood to deliver oxygen to muscles) actually work, and if so what actually happens to your body?
gpt
Somewhat. They work by increasing levels of nitric oxide in the body, which regulates blood pressure by relaxing the blood vessels. You can't supplement nitric oxide directly, but two amino acids, L-arginine and L-citrulline, cause the body to produce it. While L-arginine is a popular product, it is poorly absorbed by the body, so L-citrulline is the better choice of the two.