The Katapult™ Training System and its scientific methodology is by far the most advanced plyometric workout available for the serious athlete. Athletic Training Innovations (ATI) has created a 52-week in-season/off-season workout (patent pending) that will increase an athlete’s vertical jump, speed, lower leg strength and flexibility while decreasing the risk of injury. In a normal standing position with conventional athletic shoes roughly 2/3rds of the body’s weight is supported or rests on the heels with little effort from the calf muscles. Training in the Katapult™ shoe eliminates the heel and forces the calf muscles to support the full body load. This overload works the calves and Achilles tendons with a force equal to several times the body's weight upon impact. Used correctly, the Katapult training shoe stretches and overloads these muscles, which in time will lengthen and strengthen The Katapult™ plyometric training shoe comes with a 52-week in-season off-season training methodology and DVD (patent pending), a laminated card to take to your workout and a stretch strap that will allow you to pre and post stretch. Sizes available in men’s 5 through 13.5 with 14 and 15 full sizes only.