Hamstring injuries are common in some sports, including running and sprinting. Conditioning is key to helping avoid these injuries. The hamstring isn't an easy area to work, but several exercises help you target that area. Concentric hamstring exercises contract the muscle when it's shortened, or when your foot moves closer to your hip.
Seated Leg Curl
The seated leg curl uses a weight machine that creates resistance as you push down on the weight bar with your feet. While sitting on a weight bench, place your feet on top of the padded bar, which should be straight out in front of you. Press down with your feet, contracting your hamstring muscles. Continue pushing down and back until your feet are under you and back as far as the machine allows. To strengthen the muscle without becoming bulky, use low weights with high repetitions; MayoClinic.com recommends one set of 12 to 15 repetitions. You can also perform this exercise using resistance bands by connecting the band to a door anchor or installed wall anchor, with the other end connected to an ankle strap. Sit on a chair or weight bench facing the resistance band anchor with your leg in front, and pull your foot under you.
Lying Leg Curl
Although you can use a weight machine for this exercise, you can also use resistance bands. Lie on your stomach on a weight bench or the floor with your legs flat. If you're using a weight machine, put your heels under the padded bar. Pull your heels in toward your hips, contracting the hamstring muscle. Start with one set of 12 repetitions, then work your way up to 15 repetitions.
This exercise uses concentric hamstring contraction to strengthen the leg while allowing other leg muscles to work to stabilize the leg. Connect a resistance band to your ankle and the door or wall anchor. Sit on the floor with both feet in front of you. Lean back and rest your upper body on your elbows. Bend one knee, bringing the heel in toward your hip without letting your foot touch the floor. Keep your leg moving in a straight line without wavering out or in. Start with one set of eight repetitions per leg, and work your way up to three sets of eight reps per leg.
Exercise Ball Roll
For a more advanced concentric hamstring workout, grab an exercise ball. Lie on your back on the floor with the back of your heels on top of the ball. Lift your hips off the floor so your body is flat; only your shoulders, head and arms should be on the floor, with your legs straight. Bend your knees to 90 degrees, rolling the ball in toward your body, tightening the back of your hamstring. Lift your hips so your body maintains a straight line between your chest and hips. Start with one set of 10 repetitions, and increase to three sets of 10. To make this exercise more difficult, cross your arms over your chest or use only one foot to move the ball while the other leg is raised in the air.