Barefoot Science progressive approach is inline with athletic training programs in that muscles are constantly and gradually challenged, producing a manageable improvement in the strengthening of the muscles. This version has been designed with extra material around the toe area for trimming and is appropriate for shoes that feature a removable insole, such as most athletic and recreational shoes. Typically, the generic insole that comes with these types of shoe is slightly contoured and may interfere with how flat the Barefoot Science System is able to rest in the shoe, so it must be removed. After removing the generic insole, trim the Barefoot Science insole according to the Instructions and place it in the shoe, making sure it lies flat and flush against the ends and sides of the interior of the shoe.