HOW: Stand to the side at one end of the ladder. While keeping the outside foot out the whole time, move forward as the inside foot going in and out of each block. Use your arms to help with speed. Quicker the feet the better, but stay in control.
FEEL: You should feel the muscles in your legs working.
COMPENSATION: Stay on the balls of your feet and in control of your feet and body. Keep your chest upright.