I don't believe that igf or ghrp will elicit site growth. I have tried using igf bi-laterally, in the muscle trained. I've tried using it in just one shot, in whatever muscle I wanted to use, and I've also shot igf in just my biceps for over the course of 8 months. I have never seen a difference using any of these methods. I believe that once you inject your peptide, it will circulate through the body within a few minutes. I would just inject whichever muscle is easiest for you