Bind a Loop Band to the door with the proper Utility Strap, being careful to fix the band about 30 cm from the floor. Place the box at 2 mt away from the door and get in the band.
Place your left foot on the box, keeping your torso upright, step up on the box without bending your left knee beyond your left toe. Complete the set and repeat on the right side.
8 each side ( better without alternating) x 3 sets
Raising your heel, bending your knee beyond your toe, leaning forward.
Further information about the exercise in the technical article.