Sit-ups

For this one lie on your back. Proceed by bringing your feet to a point where your knee caps are extended into the air. Then, place your hands either behind your head, next to your face, or on your chest crossed. Last step is to continually sit up and to lie down while severely restricting the aid of your arm's motion. An optional step is to have somebody to hold down your feet.

Exercises abdominals(core)