Lie on your back and lift one leg towards your chest.
Place a belt around the top of the leg behind the calf.
Aiming to keep the leg as straight as possible, press your leg down into the belt (as if you were placing your leg back on the floor).
Press at a comfortable resistance (~20% resistance to start). Make sure your leg does not move and that you relax your head and shoulders.
Hold for 10-20 seconds.
Release and repeat 2-4 times on each leg.