this is just my opinion, but i've found it to be a load a bull-honkey.
I read once in some mag (when i was more gullible) that the key to growth was stretching, and they gave some russian stretching routine- start off stretching, then stretch during your rest break between sets, etc.... I didn't notice any change, and, if anything, I was almost weaker (because instead of resting between sets I was busy stretching).
Myself, all I do is do a few light sets with the bench, pressdowns, curls,
lat pulldown, etc..., then hit it hard and heavy. Hasn't failed me yet.