Edward R. Laskowski, M.D.: The hamstring curl is an exercise you can do with resistance tubing to work the muscles in the back of the thigh. As the name implies, the hamstring curl targets the hamstring muscles in the back of the thigh. The hamstring curl also works the gluteal muscles in the buttocks. Strong hamstring muscles actually can protect the knee from injury.
Nicole L. Campbell: To do a hamstring curl with resistance tubing, start by looping one end of the tubing around your ankle. Then step on the open end of the tubing with your other foot. The less tubing between your ankle and the opposite foot, the greater the resistance. Stand with your feet shoulder-width apart and your knees slightly bent. Bending only at the knee, raise your foot behind your body and toward your buttock as far as you can, and then slowly return to the starting position. You'll feel tension in the muscles in your legs and buttocks.
When you're doing hamstring curls, you might want to place your opposite hand on a wall for support. Keep the opposite knee slightly bent, and the opposite foot planted firmly on the ground.
Keep your back in a stable, neutral position, and keep your abdominal muscles nice and tight.
For most people, one set of 12 to 15 repetitions is adequate.
For best results, remember to keep your movements smooth and controlled.