Lying Leg Curl

Execution
1. Lie facedown on the machine and hook your heels under the roller pads.
2. Curl the weight by bending your knees, and raise your heels toward your buttocks.
3. Lower the weight back down to the start position.
Muscles Involved
Primary: Hamstrings.
Secondary: Gluteals, calf muscles.
Anatomic Focus
Foot position: Pointing your toes straight (a) targets all three hamstring muscles. Pointing the toes inward (b) emphasizes the inner hamstrings (semimembranosus and semitendinosus), whereas pointing the toes outward (e) focuses effort on the outer hamstrings (biceps femoris). Keeping your ankles bent at 90 degrees (dorsiflexed) minimizes contribution from the calf muscles and thereby helps isolate the hamstrings. Pointing your feet (tiptoe position) allows the calf muscles to participate in the exercise.

Foot spacing: your feet hip-width apart is the standard position. Wide foot spacing targets the inner hamstrings (semimembranosus and semitendinosus), whereas narrow foot spacing emphasizes effort of the outer hamstrings (biceps femoris). Foot spacing is limited by the size of the roller pad.
Body Position: The padded surface of most machines is angled at hip level, bending your torso forward slightly. This body position tilts your pelvis and stretches the hamstrings, thereby helping isolate the muscles. Keep your spine straight, and do not raise your chest upward.
Range of motion: Bend your knees as far as possible during the upward phase. Stop a few degrees short of full extension at the bottom to keep tension on the hamstrings and minimize stress across the knee joint.
Resistance: Resistance is fairly uniform, but on many new machines the resistance is lower at the start position, where the hamstrings are fully stretched and most vulnerable to injury.
Seated leg curl: The upright backrest of the seated leg curl machine creates a 90-degree hip flexion angle between your torso and thighs. While this body position affords a greater stretch, it prevents the hip extension that is required for a maximum contraction in the hamstrings.