Begin on the side of the speed ladder with your lead leg in the first hole and your trail leg outside.  Maintain a slight knee bend and keep your weight on the balls of your feet.  Moving both feet at the same time, bring your lead leg out of the ladder and place your trail leg in the first hole.  Continue alternating the position of your feet as you move down the entire length of the speed ladder.  Move your arms in conjunction with your legs as if you were running.  Perform the next repetition moving in the opposite direction by changing which foot is leading and which one is trailing.  Perform this motion as quickly as possible while maintaining control.