IGF1 LR3 Peptide Review: Benefits, Before & After, Dose, & More 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 IGF1 stimulates greater muscle hypertrophy in the absence of myostatin in male mice in: Journal of Endocrinology Volume 234 Issue 2 (2017) IGF 1 lr3 Dosage and Duration Guide. MuscleChemistry