I came across a couple articles on pub med discussing GABA and Melatonin taken BEFORE training. With melatonin, studies initially find that supplementation prior to training increases both HGH and IGF-1, and decreases levels of somatostatin (sounds pretty good, right?).
With GABA (though I'm sure it comes as no surprise) studies suggest that pre-training supplementation increases HGH by between 175-400% after exercise.
The catch? Well, in the instance of melatonin, several studies conducted used levels of 5 mg of melatonin prior to training. I found this interesting because I take melatonin for sleep, at the level of 1 mg, and find that it can knock me out fairly well.
Similarly, the studies addressing GABA used levels of 3 g, the same that I (and many others) use for sleep (4X750 mg caps).
Both of these supplements are used regularly for sleep aids, but in these studies it has been suggested that both can have a profound effect on hormone levels, suggesting a great benefit for strength and or bodybuidling training.
Of course, it is worth noting how much I (or I expect most people) would be affected by increases in an inhibitory neurotransmitter like GABA and a hormone so closely associated with our circadian rhythm as melatonin. You might find yourself waking up from an "uncomfortable" nap from beneath a barbell.
I just thought I'd throw that out here.
I may even give it a try, that is if i can stay awake through the workout, or keep my eyes open during squats.
I'm not trying to be clever here, but supposedly smoking ganja releases BIG amounts of melatonin. The question is, why not take this supplement, or have a puff immediately AFTER training? I can't see why it wouldn't have the same benefit without the drawback of being drowsy during training.