The hamstrings consist of a group of muscles that run down the back side of the upper leg. Together, they work to flex or bend the knee joint and to extend the hip joint. It's important to adequately develop your hamstrings, as they're susceptible to injuries during sports and other physical activities if they lack strength. The hamstring curl is an exercise that strengthens the hamstrings. There are multiple variations of the hamstring curl, and it's suggested that you vary which type of exercise you use throughout your weight training routine.
Seated Hamstring Curl
Adjust the seated hamstring curl machine to appropriately fit your body. Move the seat forward or back so that your knees line up with the rotational axis of the machine.
Place your feet over the top of the ankle rest. The ankle rest should sit directly underneath your Achilles tendon, right above your heels.
Bend your knees and drive your heels down so that you force the ankle rest down and back. Keep your hips down in the seat, as they may have a tendency to rise up to assist in the exercise. Bend your knees as far as you comfortably can, then extend them slowly and under control back to the starting position.
Lying Hamstring Curl
Lie on top of the bench face down. Make sure that your knees end up just beyond the edge of the bench.
Place your feet underneath the ankle rest so that the ankle rest sits on your Achilles tendon, directly above your heels. Grasp the handles in front of you.
Bend your knees and drive your heels up so that you force the ankle rest up and toward your buttocks. Don't allow your hips to rise up off the bench. Bend your knees as far as you comfortably can, and then slowly and under control, extend your knees so that you lower the ankle rest back down to starting position.
Stability Ball Hamstring Curl
Lie on your back on the floor, or on a mat if you prefer. Place your feet so that they're hips-width apart and resting atop the stability ball.
Drive your heels down into the ball and pick your hips up off the floor so that your body is in a straight line.
Bend your knees and pull your heels toward your hips, which will cause the stability ball to roll back toward your butt.
Extend your knees slowly and roll the stability ball back out away from you. Repeat the curl component of the exercise for your assigned number of repetitions before lowering your hips back down to the floor.