A backbend is a common gymnastics

Gymnastics

Gymnastics is a sport involving performance of exercises requiring physical strength, flexibility, agility, coordination, and balance. Internationally, all of the gymnastic sports are governed by the Fédération Internationale de Gymnastique with each country having its own national governing body...

, contortion

Contortion

thumb|upright|Contortionist performingContortion is an unusual form of physical display which involves the dramatic bending and flexing of the human body. Contortion is often part of acrobatics and circus acts...

, or dance move, done by standing straight, bending the spine

Vertebral column

In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...

 backwards, and catching oneself with the hands. Throughout the move, the abdominal muscles, obliques, and legs are used to steady the performer while curving backwards.

Overview

The spine, obviously the most important part of a back bend, consists of 24 bone formations or blocks, called vertebrae. Between the vertebrae are small cushions referred to as disks. The movement of the vertebrae and the compression ability of the disks give the spine its flexibility.

It is easier to perform a backbend after mastering a bridge

Bridge (exercise)

Bridge is an exercise. Many variations of this exercise are employed throughout the world, most commonly the balancing of the body on the head and feet. Hands are occasionally used instead of or along with the head. It is effective in improving lower back strength...

. A bridge helps familiarize your bones and muscles to the positions and movements of a back bend.

Uses

The backbend is important in gymnastics because it is essential to perform a back handspring

Handspring (gymnastics)

A handspring is an acrobatic move in which a person executes a complete revolution of the body by lunging headfirst from an upright position into a handstand and then pushing off from the floor with the hands so as to leap back to an upright position. Handsprings are performed in various physical...

. There is also a back bend stand up.
When you first try a back bend go to a wall and have your back face it. Put your hands on the wall (with your back still towards the wall) and start "walking down the wall" using your hands.

Medical Aspects

Though the back bend is a popular move, it can also be a dangerous one for people with back or wrist problems. Back bends can be bad for your back when done incorrectly.