UPDATE:
1) If you guys aren't familar with it there is an excellent discussion of GW on a site called Invalid Link Removed . What's really interesting is the discussion after the article, which includes a lot of discussion by a PH.D. in biochemistry from the University of Chicago.
2) The article confirms many of the observations I've made of GW:
a) it does NOT work well for max effort type training; or even, I find, relatively fast paced straight sets. In fact, over time I became weaker at high effort sets (> 85-90%)
b) it DOES work well for longer duration/higher rep sets, high work density (e.g., supersets, antagonistic supersets, giant sets, etc.), conditioning/GPP work, circuits, barbell complexes, LISS, etc.
3) I honestly think the endurance aspect of GW is a bit overrated, unless your training is optimized to take advantage of it, and even then I don't think it's as dramatic for me as some have claimed.
4) One very important effect from GW is the insulin sensitizing. Over time, this can really assist in body composition shifts--more LBM. and less fat. This effect was VERY strong. In fact, at 21 mg. it was too strong! I had outright hypoglycemic episodes, mainly after training. This is what gives that hard muscle "perma pump" that I get from cardarine--I mean 24 Hrs. a day!
5) 21 mg. a day made me feel like ****! I have now backed it down to 14 mg. day and immediately feel better. bad in what way you ask? Well, several weeks into my cycle I started experiencing really sore achy muscles and joints--but mainly muscles. It was enough to make me take notice. Lo and behold, the PH.D. from the University of Chicago believes that Cardarine can, in high doses, induce rhabdomyolysis (a condition causing the rapid breakdown of muscle tissue)!
The PH.D. does believe GW has potential ergogenic uses, but advises to use it in much smaller doses with a more conservative cycle length.