HOW: Place your back against a wall then slide down into a wall squat. Shift your weight onto one side and lift the opposite leg off the floor. Have a partner pull a band wrapped around your knee. The stronger the band and the more force your partner pulls with, the more challenging this exercise will be. Avoid allowing your partner to pull your into a bend, you will drive your knee back towards the wall.
FEEL: You will feel the muscles on the front of your thigh working with this exercise.
COMPENSATION: Avoid leaning your trunk forward. The more you lean into the band the easier it will be to keep your trunk upright.