Two keys with this exercise:

  1. You don't have to elevate the back leg as high as you may think you need to. Many people use a bench that's too high for them. You want to go just high enough to shift the weight to the front leg.
  2. Keep your torso upright as you go up and down.

For variety, you can use dumbbells or a barbell held in the back or front squat position.

Related:  The Absolute Best Way to Build Quads

Related:  Strong Legs, Big Round Butts