Stand upright while pressing a stability ball against the wall with the middle of your back.
With your legs extended and out in front of you, closer than shoulder-width apart, inhale and raise one leg while squatting down with the other.
Continue to squat down while consciously pressing back against the ball, bringing your straight raised leg forward, and lowering your body until the thigh of your planted leg is just above parallel to the ground.
Exhale and stand up while bringing your raised leg back toward your body while continuing to actively press your back against the ball, returning to the starting position.
After all reps are completed, switch sides and repeat the movement. 10 reps prescribed means you should perform 10 reps on each side (20 total).