IGF 1 LR3 The Muscle Building Peptide Everyone's Talking About IGF 1 LR3 is one of the most powerful performance peptides used for muscle growth, recovery, and fat loss. It's a modified version Mechanisms of IGF 1 Mediated Regulation of Skeletal Muscle Hypertrophy and Atrophy IGF 1 LR3 does not promote growth in late gestation growth restricted fetal sheep American Journal of Physiology Endocrinology and Metabolism American Physiological Society Domain dependent effects of insulin and IGF 1 receptors on signalling and gene expression Nature Communications