The hamstring curl exercise strengthens and tones the backs of your upper thighs. You also improve the muscles of your lower legs, backside and core depending on the position you select. The leg curl is performed while face down, seated or standing for exercise variety and comfort. You also have the option of changing your level of resistance. You may do all of the exercises on weight machines, but you may also replicate the exercises using a resistance band.
The hamstring muscle group is located on the backs of your upper thighs. While you know this muscle by one name, it is actually consists of three muscles that work together. The biceps femoris, semitendinosus and semimembranosus muscles begin either high on your upper leg bone or even higher on your sit bones. The muscles end on either side of the outer or inner portion of your lower leg bone. Because the muscle group crosses your knee joint, it contracts when you bend your knee and raise your foot behind you, which is the movement in a leg curl exercise.
During the lying leg curl, you are face down on the machine's bench with your legs straight behind you. You bend your knees and raise your feet, which are under the lever pads, toward your backside to contract the hamstrings. In this position, your inner thighs and calves assist the upward movement. On the downward movement, the fronts of your upper thighs and your shins control the lowering of the weight.
You do the standing leg curl one leg at a time. The resistance is located above your ankle. You bend your knee to raise your foot toward your backside to contract the hamstrings. To maintain your balance and upright body position, your core contracts, specifically your transverse abdominus, which you contract when you tighten your navel toward your spine. Your erector spinae, which is located on both sides of your spine, contracts to maintain your posture. Your inner and outer thighs tighten as you balance on one leg.
The seated leg curl machine positions your straight legs in front of you. Your calves rest on a pad and then your legs push down to curl your feet underneath you. The hamstrings perform this motion. Your feet are flexed and your toes face the ceiling, which contracts your anterior tibialis, or shins. Your core, consisting of the abdominals and back, tighten to maintain good posture and keep you in the seat as you pull down on the weight. Your inner thighs tighten to maintain the alignment between your knees and hips.
A mother of two and passionate fitness presenter, Lisa M. Wolfe had her first fitness article published in 2001. She is the author of six fitness books and holds an Associate of Arts in exercise science from Oakland Community College. When not writing, Wolfe is hula-hooping, kayaking, walking or cycling.