Leg curl machine

The leg curl machine does a great job of strengthening your hamstring muscles.
Use caution if you have a history of lower back discomfort.

Getting set
Set the ankle pads of the machine so that when you lie on your stomach, the underside of the pads are flush with the tops of your heels. Lie down, rest the side of your face on the support pad, and grasp the handles. Gently flex your feet. Pull your abdominals in and tuck your hips down so your hipbones press into the pad. See photo A.

The exercise
Bend your knees to lift the ankle bar until your calves are perpendicular to the floor. Then slowly straighten your legs. See photo B.

Do’s and don’ts

• DO keep your hipbones pressed against the machine and your abdominals pulled in. You may want to lift your thighs just a hair upward before you bend your knees.
• DO lower your legs back down slowly so the weights you’re lifting don’t slam down against the rest of the stack.
• DON’T — and this is a big don’t — allow your butt to pop off the pad. This puts stress on your lower back and minimizes the work being done by your hamstrings.
• DON’T kick your heels all the way to your butt.

Other options
Other curl machines: Some machines work your hamstrings from a standing or seated position. Others have independent left and right sides so that each leg has to carry its own share of the weight. Still others have a “range limiting” device that allows you to cut off the movement at the top or bottom —a good variation if you’re experiencing any pain while doing this exercise.
Single-leg curl: Lift with both legs, straighten one out of the way, and lower the weight down with one leg only.

Kneeling leg curl

The kneeling leg curl targets your hamstring muscles.
Pay extra attention to good form if you have lower back or knee troubles.

Getting set
Kneel on your elbows and knees on a mat or thick towel, with your knees directly under your hips and your elbows directly under your shoulders. Clasp your hands together or turn your palms toward the floor. Flex your right foot so it’s perpendicular to the floor. Keeping your knee bent, lift your right leg and raise your knee up to hip level. Tilt your chin slightly toward your chest and pull your abdominals in so your back doesn’t sag. See photo A.

The exercise
Straighten your leg and then bend your knee. Complete all the repetitions with one leg before switching sides. See photo B.

Do’s and don’ts

• DO keep your neck still and your shoulders relaxed.
• DO move slowly so you feel the tension in the back of your thigh.
• DON’T use an ankle weight for this exercise: It places too much pressure on your knee.
• DON’T just throw your leg out straight and snap it back again.
• DON’T raise your leg above hip height.
• DON’T arch your back as you curl and uncurl your leg.

Other options
Variations (easier): To make this exercise easier, lie on the floor with your forehead resting on your forearms. Lift your thigh slightly off the floor, and then curl and uncurl. Or do this exercise while standing and holding onto the back of a chair or the back of an upright bench with your hands.
Weighted leg curl (harder): Add weight to this exercise by wrapping an ankle weight around your ankle or thigh. Or do a kneeling or standing version of the exercise with the low pulley of a cable machine that has a padded ankle strap.

Leg extension machine

The leg extension machine zeroes in on your quadriceps muscles. If this exercise bothers your knees, try the modified version or choose a different exercise.

Getting set
Set the machine so your back sits comfortably against the backrest, the center of your knee is lined up with the machine’s pulley, and your shins are flush against the ankle pads. (On most machines you can move the backrest forward and back and the ankle pads up and down.) Sit down and swing your legs around so your knees are bent and the tops of your shins are resting against the underside of the ankle pads. Hold on to the handles. Sit up tall and pull your abdominals in. See photo A.
The exercise
Straighten your legs to lift the ankle bar until your knees are straight. Hold for a second at the top position, and then slowly bend your knees. See photo B.

Do’s and don’ts

• DO make sure that you take the time to set the machine properly.
• DO move slowly.
• DON’T ram your knees at the top of the movement.
• DON’T arch your back in an effort to help you lift the weight.

Other options
Modified leg extension (easier): If one leg is noticeably stronger than the other, slide one leg out of the way and do this exercise one leg at a time. You probably will need less than half the weight you use when lifting both legs together.
Single-leg extension: Many leg extension machines have a mechanism you set to limit the distance that you bend and straighten your legs. Use this device if your knees give you trouble at any point of the exercise.
Ball squeeze leg extension (harder): Place a soccer ball, weighted ball, or rolled towel between your knees. As you extend your leg, concentrate on squeezing the ball so it doesn’t slip out of place. This version of the exercise forces your quads to work harder in order to hold onto the ball.