IGF 1 LR3 and Penis Enlargement: What the Evidence Actually Shows What is the effect of Insulin like Growth Factor 1 (IGF 1) Long Arg3 (LR3) on muscle growth? IGF 1 LR3 is a powerful growth factor that helps build muscle, burn fat, and speed up recovery. It works by boosting protein synthesis, which helps muscles grow and heal faster. It also improves how IGF 1 LR3 in Aesthetic and Anti Aging Medicine: Benefits and Risks Hubmed