Lie supine on mat with lower legs on bench. Cross wrists on chest.
Flex waist to raise upper torso from mat. Keep low back on mat and raise torso up as high as possible. Return until back of shoulders contact mat. Repeat.
Leg elevation keeps pelvis tilted back, keeping low back on mat. See Spot Reduction Myth.
Movement can be made easier by placing arms further down away from head or extended up above knees. Deconditioned individuals can start on slightly declined board.
Exercise can be made more challenging by placing hands further up toward head. See Arm Position During Waist Exercises. Exercise can also be performed on incline board or with additional weight.