IGF-1 LR3 bodybuilding overview IGF-1 LR3, also known as Insulin-like Growth Factor 1 Long Arginine 3, is a synthetic version of the natural hormone IGF-1. It is commonly used in the bodybuilding world to promote muscle growth and aid in recovery. IGF-1 LR3 works by increasing the number of muscle cells (myoblasts) and stimulating the growth of existing muscle cells (hypertrophy). …