Lying Leg Curls
Lay facedown on the leg curl machine. Curl the weight up with your ankles. Exhale on the way up. Inhale on the way down.
Before beginning this exercise, you will first need to set up the machine to fit your body. The first thing to note is your knees should be directly to the side of the machine's pivot point. Your legs should bend in the same way as the machine rotates to maintain pressure throughout the set and avoid unnatural lifting that may lead to injury. This means that your quads are on the pads with your knees slightly below, free for a full range of motion. Now that you know where you will be lying down, adjust the foot pad so it's directly above your ankles. Lay down and position your feet shoulder width on the ankle pad, lying flat on your quads (leg shouldn't be rotated in or out). Grab the hand grips and curl the weight up. Do it slowly. Bring the weight all the way up, however, dont't let the pad hit your butt. Control the weight as you lower it. Do not lock out your knees on extension.
Keep your back straight throughout the exercise. Some people even prefer to rest on their elbows to maintain a straight back throughout the motion. That is not necessary because your back remains straight lying down. By looking directly at the floor throughout the exercise, you will keep your neck and back straight. You could point your toes to emphasize hamstrings, or flex the legs and position your feet as if you are standing to focus on the glutes. Keep legs stationary in performing this exercise - do not rotate your legs in or out on your quads.
Just like with any other isolation exercise many people rely on the leg curl to balance leg strength. To avoid favoring one leg over the other, you could perform the exercise using one leg at a time.