Selective alpha-1 agonism would cause an unwelcome increase in blood pressure. It is one of the main adrenergic regulatory pathways for BP (constricts smooth muscle, in particular in the vascular system...arterioles, venules, and coronary arteries). Norepinephrine, epinephrine, etc activates alpha1, which is why they result in vasoconstriction and increased BP.
I would suspect that there is no relevant use for a selective alpha1 agonist in bodybuilding/powerlifting/anything without a medical use.
Alpha 2 is activated by norE as a negative feedback loop...agonism of alpha2 receptors leads to downregulation of NorE release, as well as vasoconstriction. Hence selective blocking of alpha2 (a la alpha-yohimbine) will lead to less downregulation of norE release, among other things.