Most NO products use L-Arginine to create their effect. Unfortunately that is actually counterproductive, here is a nice study for you:
Oral L-arginine before resistance exercise blunts growth hormone in strength trained males.
“L-arginine ingested before resistance exercise significantly elevated plasma L-arginine concentration but attenuated plasma GH in strength trained individuals”
Here’s another one:
Growth hormone, arginine and exercise.
“Most studies using oral arginine have shown that arginine alone increases the resting growth hormone levels at least 100%, while exercise can increase growth hormone levels by 300-500%. The combination of oral arginine plus exercise attenuates the growth hormone response, however, and only increases growth hormone levels by around 200% compared to resting levels.”
So if you’re going to take it at all, don’t take it on workout days. Unfortunately even that has problems:
The chronic oral administration of arginine aspartate decreases secretion of IGF-1 and IGFBP-3 in healthy volunteers.
“In healthy volunteers, a chronic oral treatment with 30 g/day arginine aspartate is followed by a decrease in IGF-1 and IGFBP-3 secretions.”
So if you use it, then acute, sporadic dosing only on non-workout days. It has some other side effects that make even that probably not worth it, but I’ll leave that research to you.