IMO, that is the worst possible method while educating your bow to bend. Using a rope and pulley allows you to exercise the limbs as you lengthen the draw without holding it statically. You can observe the bend of each limb and mark the stiff spots or weak spots without overstraining the bow. Holding a bow statically at full draw or on the way to full draw can be very detrimental to the bow at any time in its life.