Lying on your back, knees bent and feet flat on the floor, place a belt above or below the knee and push the knees out slightly so they are in line with the hips and pressing against the belt.
Press both thighs outwards into the belt at a comfortable resistance (~20% resistance to start).
Make sure your legs do not move and that you relax your head and shoulders.
Hold for 10-20 seconds.
Release and repeat 2-4 times.
You can also perform this seated.