HOW: Get set-up seated on the edge of a surface with your feet hanging off at a 90˚ angle. Place a band around your ankles. On the side you want to perform this exercise, kick the leg straight until your thigh and shin make a 45˚ angle, hold for a moment, then slowly return to starting position and repeat. Your other leg shouldn't move to keep tension on the band.
FEEL: You will feel your quadriceps, the muscles on top of your thigh working with this exercise.
COMPENSATION: Do not move the other leg, do not move the rest of your body, limit the motion to your knee