This strengthens your quads, hamstrings, glutes, and even works your calves. It’s a great alternative to the forward lunge for those who are worried about knee injury (like Ali, who has crummy knees), as it does not allow your knees to extend beyond your toes. Regardless, always be careful when performing this exercise, especially if you have a history of poor knees.
Stand up tall with your arms at your hips or at your sides. Take a big step backward with your left foot so that your left foot is in back, and your right foot is apart, toward the front of the room. Now lower your hips to the floor until your front leg (your right leg) is at a 90 degree angle. Now push yourself up, returning your back foot (left) to the starting position next to your right foot. When pushing up, most of the strength should come from your front (right) foot. Now alternate sides, stepping your right foot to the back, lowering to a 90 degree angle, and pushing up with your left foot. Back to the starting position. Continue to alternate legs.
As you work through the sets, really focus on pressing the heel of your front foot into the ground as you lift up in order to engage your glutes to their full potential.
Resist the temptation to put your hands on your knees to help push yourself up. Not only does pushing on your knees lessen the effect of the exercise, but it can cause injury.