Cerebral palsy (CP) describes "a group of permanent disorders of the development of movement and posture, causing activity limitation that is attributed to non progressive disturbances that occurred in the developing fetal or infant brain. Hemiplegia is a condition involving paralysis or partial paralysis of one side of the body. "Balance" is defined as the ability to maintain equilibrium in a gravitational field by keeping the body mass centered over its base of support. It is also defined as the ability to react to destabilizing forces quickly and efficiently to regain stability via postural adjustments before, during, and after voluntary movement and in response to external perturbation. Walking backward is nearly a mirror image or time-reversed copy of walking forward.