You don't need weights to get a challenging leg workout. The prone hamstring curl, demonstrated here by celebrity trainer Harley Pasternak and featured on his "Harley's Hollywood Workout" video game, can bring the burn without them.
What it does
This exercise tones your hamstrings, the muscles that run along the backs of your thighs. The propped up-prone position creates a situation of "passive insufficiency," Pasternak says, tightening the hamstrings and therefore creating an intense muscle contraction with very little movement.
What to do
Start by lying stomach down on a mat, propping yourself up on your elbows, with your chest open and facing forward. Lift legs back from the knee toward your rear as far as your flexibility allows, with the soles of the feet facing up. Lower legs back to the starting position. Make sure to keep your lower abdominals slightly contracted to protect your back.
To make it more difficult, you can add ankle weights on both legs, or do it one leg at a time, stacking the ankle of one leg behind the heel of the other, to provide additional weight. Cross legs the other way and repeat the movement.
Work up to two to three sets of 20.