Leg curls is that exercise that works the back of your legs, those muscles called hamstrings.
Curls is the only isolation movement that can work those muscles.
Maybe you're different than me, but I find hamstring curls a hard exercise and I have less strength than I would expect, that's why lately I am trying to work that area more than usual.
PRIMARY MUSCLE: Hamstrings
SECONDARY MUSCLES: None
EQUIPMENT: Lying Leg Curl Manchine
INITIAL POSITION: Lie on the machine with your body facing down and grab the handles in front of you (if present). Position your body so that your knees are free outside the machine. Adjust the leg pad so that it's positioned behind your ankles. Not too high towards your calves, not too low on your heels.
MOVEMENT: Curl the pad towards your glutes as much as you can, squeeze your hamstrings and then lower your feet to the initial position.
BREATHING: Exhale while you curl, inhale during the negative phase.
TIPS and ERRORS: Curl as much as you can and feel the contraction for some moments. Try to do a full range of motion. When you return to the initial position go slow, don't slam the weights and don't lose tension. Don't arch your body when you curl, keep it flat against the machine.
There are basically three ways to do leg curls:
Each of them, in my opinion, is equally effective. I'd go ahead and say do what you prefer or what works better for you.
I personally prefer the lying curls, but when I change my routine I like to do something different, a new exercise that gives me more motivation for the next six weeks. So yeah, basically I switch from one to another depending on how I feel at that moment.
No matter which version you do the exercise is always the same. Curl your legs bringing the heels towards the glutes and keep your upper body rigid and straight.