Start with the feet hip-width apart, with the right foot forward and the left foot placed back behind the body on a bench or box that is about knee-height. Hold a dumbbell in both hands in a vertical position in front of the chest and keep the elbows close to the rib cage during the exercise. Keep the back straight while lowering the left knee towards the floor. Before the left knee hits the floor, press the right foot into the ground, pull back on the right knee, and push the top of the left foot into the box to return to standing.