How to do Sit-ups
Begin lying on your back with your legs bent and feet flat on the ground. Place your hands behind your head with the elbows out to the side.
Tuck your chin toward your chest and then crunch up and forward as you lift your head off the ground. Press your belly button toward the ground as you tighten your abs.
Then, lower your head back down to the ground.
Repeat for the desired repetitions.