Place stability ball between your lower back and a sturdy wall behind you and a lightweight medicine ball (or unweighted ball) between your thighs, just above the knees. Keep your spine in a neutral position, abs engaged, arms relaxed at your sides, and feet flat on the floor. With straight legs, walk your feet forward until they're approximately 12 inches in front of you (not pictured).
INHALE: With your back flat and abs engaged, squat straight down by bending the knees until the thighs come approximately parallel to the floor. EXHALE: Straighten your legs to push back up to the starting position to complete one rep.
Make sure your knees to not extend past your toes. If they do, stand back up and scoot your feet farther away from you. Push your back into the ball behind you and keep your back as straight as possible.
Muscles Worked: Quads, Hamstrings, Inner thighs