this is why.. check out the studies on mice below
In 2008, researchers at the Salk Institute discovered that AICAR injected in experimental mice significantly improves their performance in endurance-type exercise, apparently by converting fast-twitch muscle fibers to the more energy-efficient, fat-burning, slow-twitch type. They also looked at the administration of GW 501516 (also called GW1516) in combination with AICAR. Given to mice that did not exercise, this combination activated 40% of the genes that were turned on when mice were given GW1516 and made to exercise. This suggests it may be possible to obtain some of the benefits of exercising without actually exercising.
That I have seen. What I don't understand is why more aren't using it if the potential benefits are so fantastic. But I guess with most here being interested in adding lean mass that conversion of fast-twitch to slow-twitch may not be what they want.
I am still considering adding it into my cycle but the cost is pretty high from what I've seen and I have only found one place that even has it.