IGF-1 is basically a polypeptide hormone that has the same some of the same molecular properties as insulin. IGF dose actually stand for insulin-like growth factor. IGF-1 is mainly responsible for long bone growth in children and it also affects muscle growth and repair of adults. Long R3 IGF-1 is a more potent version of IGF-1. It’s chemically altered i like to think “enhanced” to prevent deactivation by IGF-1 binding proteins in the bloodstream. This results in a longer half-life of 20-30 hours instead of 20 min… So that means a far more effective version than the short chain we we re perhaps more familiar with.