I know nothing on this, but find it interesting. Found this on another forum:
LGD-4033 is pretty good for muscle building, but it is HIGHLY suppressive. I personally like S4 and MK-2866 (andarine and ostarine) since they are not suppressive. S4 is great for recomp and MK2866 is great for muscle building. Neither one has any adromophic affects, both are non-liver toxic, and both do not increase DHT or E2 levels. They are not as strong as AAS, but since they have none of the bad sides they are a good alternative.
Anyone use these things? Seems too good to be true. Activating the androgen receptor only in muscle