One-legged Squats

Stand on one foot; lift the other and keep it close to the ankle of your stance foot. Keeping the head up, the chest lifted, and the abdominal muscles tight, squat until that knee is bent to 90 degrees. Pause briefly, then stand upright by pressing heel into the floor and keeping the glutes (the rump muscles) tight.

Bench squat: stand on one foot on the edge of a solid platform about 2 feet tall with the other foot hanging down. Squat down on the stance leg and let the other leg hand down beside the bench.
Resistance cord: stand firmly on the cord with the stance foot. The unstretched cord should reach your knee. Stretch the cord until the handle reaches your waist; keep it there throughout the exercise. Perform as above.