MGF (type of IGF) will do it. Just don't inject too much in one muscle, the only question is what is too much. Although, no one can tell you exactly what will happen, especially not in each individual case, because the research didn't go that far yet. But for right now, it is thought that it will activate satellite cells, but they are not sure how much of this happens in adults VS teenagers. It should at least help repair the cells, therefore allow them to grow in size. MGF is primary for repair after the resistant training, shorter action, and then IGF-1 comes into the play with less action and longer duration of action.