Muscles Used in the Backstroke. Even though you're swimming on your back, you use your abdominals in addition to the muscles of your back -- the latissimus dorsi and spinus erectors -- to support you as you flow through the water during the backstroke.
The average distance for a pitching wedge is 130 to 135 yards; for a sand wedge 115 to 120 yards; and for lob wedges 75 to 95 yards.
The official rules do not specify the shape, height, or composition of the wall, or a specific mandatory distance from home plate (though Major League Baseball mandates a minimum distance of 250 feet (76 m) and recommends a minimum distance of 320 feet (98 m) at the foul poles and 400 feet (120 m) at center field).