A crunch begins with lying face up on the floor with knees bent. The movement begins 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

Yoga has become popular as a form of physical exercise based upon asanas (physical poses) to promote improved control of mind and body and to enhance well-being. ... The word "yoga" is derived from the Sanskrit root yuj meaning "to yoke or join together.