This is a semi-single leg stability exercise to help strengthen the knee, patello-femoral joint, glute max and VMO muscles, gain knee stability early on and help with the squat movement pattern. It is a precursor for one leg work.
Demonstration and Instructions
Stand in split stance, make sure that your pelvis is level and in neutral. Externally rotate the knee so the knee cap is over the middle of the foot (outside of the big toe). Lunge forward and down, making 80% of your body weight go onto the front heel and take the weight out of the back leg to 20%. Keep your front shin, back leg and spine all the same forward angle (30 deg) and don't let your front heel come up of the floor. Your spine should stay neutral as your body comes forward and your pelvis should stay level. Return by pushing the ground away from you through your front heel, feeling the front leg glutes and quads doing the work. Keep you knee slightly externally rotated so your knee cap tracks over the outside of the big toe.
Special Notes
You may need to hold onto something to keep your balance and technique good intially but ultimately after practice you should be able to do it without holding on.