Here is my take :
GHB is NOT, i repeat " NOT " in the least useful to bodybuilders, ESPECIALLY those who do AAS.
Now for my reasoning :
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I'd heard the same thing you heard, a couple of years back and decided to try the shit. And it is pretty much accessible at where i live. I tried it for a couple of months as i wanted to desperately increase my GH levels without actually injecting GH and seeing ghb as a possibility to safely do so, i went ahead and tried. Please remember bro, i don't drink. Neither do i smoke or do drugs.
I'm a disciplined health freak who is extremely health conscious and lead a serious responsible life with wife, kids and my old parents...
All i got from it was deep sleep for a couple of hours maxx and then i would be fully awake and try to get back to sleep again, albeit unsuccessfully. It did nothing to my musculature and / or strength. Yet, i gave it a fair shot before deciding never again.
A very important thing to understand is...GHB is a serious recreational drug that can destroy lives and although i was strictly using it for body building purposes, i saw and felt the urge to have it even after i quit. But i restrained myself and got over the urge in a couple of days. But unfortunately, there are people whose lives have turned hell and run amuck, thanks to this killer.
I would strongly recommend reading ' tears on a keyboard ' - google it.
To sum it up, ghb can put you into a deeply restful state for a couple of hours thereabouts, nothing more. I would be better off with needto's needtosleep to get that kind of deep rest for my body and muscles, not to mention staying on the safe side of law