The best ways to maximize mobility and even prevent back pain. Walk, work and wake better with these hamstring stretches. Breakthroughs, discoveries, and DIY tips sent six days a week. We have some news you're gonna want to sit down for--but you probably shouldn't: Your hamstrings are, in all likelihood, an anatomical disaster for a number of possible reasons, not least of which being excessive time spent seated on them. "The hamstrings are three muscles located on the back of your thigh, and they're responsible for bending your knee and extending your hip," says Marissa Cummo, PT, DPT, assistant director of physical therapy at NYC Health + Hospitals Bellevue .