Leg Curl

The leg curl is a machine exercise that isolates the hamstrings, the muscles on the back of your thighs. Your calves help out a little. It builds knee-bending strength and adds hamstring size without loading your lower back, and it pairs well with a Romanian deadlift for full hamstring coverage.

Set up on a leg curl machine with the padded lever sitting just above your heels or lower calves. Lie face down (or sit upright on a seated version) so your knees line up with the machine's hinge, and grip the handles or sides of the bench to keep your hips pressed into the pad.

Start with your legs straight but knees unlocked. Curl your heels toward your glutes by bending your knees. Squeeze briefly at the top, then lower the pad back down under control all the way. Do not let the weight stack snap down at the bottom.

Breathe out as you curl up and breathe in as you lower. Keep your core gently braced so your hips stay still. To make it easier, use less weight or shorten the range slightly. To make it harder, slow down the lowering phase or pause for a second at the top.

Fault: Lifting your hips off the pad to curl heavier weight. Fix: Keep your hips and thighs pressed against the pad through the whole rep; if you cannot, lower the load.

Fault: Letting the weight stack crash down at the bottom. Fix: Resist the pad on the way down and control the eccentric until your legs return to the start.

Fault: Cutting the range short or swinging through the reps. Fix: Use a full, controlled motion from straight legs to heels near the glutes, and avoid using momentum to get the pad up.