Stand with your back against a wall, placing your feet about two feet in front of you. Feet should be hip-distance apart.
Bending your knees, slide your back down the wall until your knees are at 90-degree angles. Your knee joints should be over your ankle joints, so you may need to inch your feet farther from the wall to create proper alignment. Don't let your knees fall into the midline of your body or sway outward.
Hold for 30 to 60 seconds, and then stand up to complete the rep.
Make this even more challenging by resting a soft medicine ball on your lap.