The majority of human studies I've seen with PA have been around 750mg/ed, but I've read a couple in the 1.5-2g/ed range as well.
Maybe someone with more SL / PA first hand experience can chime in with what's worked best for them.
One of the main things that attracted me to OL is that typically, when they add an ingredient, they add the full clinical dose. That's carried a lot of weight with me.
I've interacted quite a bit with Dr. Wilson and Dr. Stout, two of the three main researchers of PA. through Biotest's forums. I've also been using PA since it first became available. Here are the Cliff notes:
1) the effective dosage range for PA is ~ 450-750 mg. per single dose. Below ~ 450 mg. is of little use for stimulating mTOR, above ~750 mg. as a single dose seems to produce little in additional mTOR activation.
2) PA stimulates mTOR through a different mechanism than resistance training (through the ERK pathway), and thus serves to amplify the mTOR stimulation from resistance training. This is also why PA stimulates mTOR and protein synthesis independently of resistance training.
3) Various dosing schemes have been tried, including splitting the dose 1/2 pre, 1/2 post training. What they have found is that DOSING 1 HOUR PRE produces the best results. The idea is to increase PA levels as much and as fast as possible within the therapeutic limit, and to have these elevated levels WHEN YOU BEGIN TRAINING so as to magnify the mTOR activation from the training.
4) PA is active in your body for ~ 7 hours.
5) Additional 750 mg. doses HAVE been found to produce additive effects; the second dose should be consumed 6-7 hours after the first.
Hope that helps,
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