How long does it take for IGF receptors to up-regulate after a work-out? It seems inefficient for all the muscle cells to have stores of IGF receptors and I doubt they do. So after you workout, the cells would need to produce the new receptors before they could be exposed. My point being, I dont understand the whole rush home within an hour to inject, since your muscles will probably be increasing IGF receptors for quite some time. Just a thought.