Lactic Acid

Lactic acid is a metabolic byproduct of intense exercise, it has been shown to be very highly correlated with GH secretion. AKA, more lactic, more GH!

And yes, cell swelling is more correlated with growth than muscle damage. So don’t sit on your butt for 5 minutes between sets if you want to grow. Create more lactic acid and more pump by using shorter rest periods.