What is the purpose of curl-ups?

Curl-ups are abdominal exercises performed to strengthen the called the rectus abdominis muscle. This exercise also helps to tone your midsection. To perform a curl-up, you lie on your back with knees bent and the feet flat on the floor. Place your hands behind the head and tuck the chin to the chest. Curl the head, shoulders, and upper back off the floor. Roll back down to your starting position and repeat the movement.