A fitness ball is a ball specifically developed for exercise.
This PVC ball is meant  specifically for use in exercises designed and set by medical practitioners and in therapy that involves light physical types of exercise.
A typical fitness ball is approximately 35 to 85 cm and is also referred to as a birth ball, body ball, gym ball, or physioball.
There are many more names for it in different cultures and communities.
This ball is larger and lighter than a regular medicine ball.
The ball for exercising was developed by a plastics manufacturer called Aquilino Cosani, in 1963.
This Italian plastics manufacturer had in time, perfected the manufacture of larger and puncture resistant balls made from plastic and he called the then manufactured balls 'Pezzi balls'.
The earliest ball for exercising were used in treatment programs designed by the medical fraternity for newborns in Switzerland and later in Basel at a number of Physical Therapy Schools.
The popularity and effectiveness of the ball for exercising soon influenced its use in neuro-developmental treatment and within the application of functional kinetics.
Today, the fitness ball for exercising is being used to treat adults with a number of orthopedic problems.
The use of the ball is usually part of a physical therapy program that is executed within a clinical setting.
The fitness ball for exercising is also being used in athletic training and yoga.
The primary benefit of using this ball for exercising is that unlike the traditional method of exercising on a hard and flat surface, the use of the fitness ball not only improves balance and body stability while trying to keep the ball balanced, but also engages more muscles in the attempt than irregular exercises.
With the use of the fitness ball for exercising, the core body muscles become stronger and more focused in application.
The exercise balls or fitness balls train the body in controlled movements and this in turn also impacts movements that are essential in sports.
There are many ways in which you can use the ball for exercising and some of them are listed below:

• You could sit on tit, instead of on a chair.
  In this way, the abdominal and back muscles remain active and in turn contribute to correct posture via the balancing act.
  The toned muscles give you a confidence boost and enable you to earn praise for an erect posture.
   
• You could make the use of a fitness ball or Swiss ball in physical therapy.
  There are a number of benefits associated with sitting or standing against a wall with the ball in between.
  Standing enables you to address back problems and the aches and pains connected with just sitting without additional exercises, in sedentary jobs.
  
• This ball designed for exercising is also known to be used during labor.
  It is known to help  to position the fetal head into the pelvis.
  Sitting on the ball and gently rocking the hips aids in the process of birth and thereafter in post natal body weight maintenance.
  

The use of a fitness ball for exercising can be done in a typical classroom setting or a home, in privacy and with or without the help of an instructor.
It could be used while you sit at the work desk or while you stand.
It addresses subtle but life altering issues like correct posture and body toning.
It that is designed for exercising can be stacked and carried around very easily and is accessible with a number of online and offline resources.