Adjust the seated leg curl machine to position the footpad just above your heels. Ensure machine is set so feet are as high as is comfortable. Sit upright and engage your abs. Flex your feet towards your shins and then proceed to curl your legs towards you, exhaling as you do so and keeping your calves flexed. With control return to the start position, extending the legs again and inhaling as you do so. Try not to use momentum to perform the movement.