Crunch is one of the most popular abdominal exercises to make a person’s stomach flatter and stronger. The crunch primarily works the rectus abdominis muscle but it also works the obliques.

A crunch begins with lying face up on the floor with knees bent. Then movement continues by curling the shoulders towards the pelvis. The hands can be behind or beside the neck or crossed over the chest.

Injury can be caused by pushing against the head or neck with hands.