Made of elastic rubber, gym balls range in size from 35 to 85 cm (diameter), with most in the 55 - 65 cm range. They are used extensively in both physical therapy and exercise.
Much larger and lighter than a medicine ball, gym balls go by numerous names, including:
- Balance ball
- Birth ball
- Body ball
- Exercise ball
- Fit ball
- Fitness ball
- Physioball
- Pilates ball
- Sports ball
- Stability ball
- Swedish ball
- Swiss ball
- Therapy ball
- Yoga ball
They work on the principle of creating instability. When used on a flat, firm surface, the body responds to the instability by engaging a wide range of muscles to remain balanced. Most programs that use these focus on the core muscles (abs and back).
Physiotherapists commonly use them for individuals with low back pain, and as an aid in developing proproiception in patients with lower limb injuries.
Mainstream users have also taken to them in large numbers, finding them an excellent way to build control and strength in the body's core muscles.
