Free Sample
The Complete Handbook of Exercise Balls
For Fitness Professionals, Facility Managers, and Equipment Specialists
by Alumigogo Books
Chapter 1: Understanding Exercise Balls
An exercise ball is a large, inflatable sphere typically made from vinyl or similar elastic material, designed to support a person's weight while remaining flexible enough to deform under load. Standard sizes range from 45 centimeters to 85 centimeters in diameter. Unlike a fixed, rigid surface such as a bench or chair, an exercise ball creates an unstable platform—the ball rolls, sinks, and shifts when weight is applied to it. This instability is the core feature that makes an exercise ball functionally different from other fitness equipment.
The mechanism is straightforward: when you sit on or lie against an exercise ball, your body weight compresses the ball, reducing its diameter. The air pressure inside the ball increases slightly, resisting further compression. At the same time, your muscles must constantly micro-adjust to keep your body centered on the unstable surface. You cannot remain passive; the ball demands active stabilization. This is why exercise balls are used in rehabilitation, core training, and office settings—not because they are inherently superior to chairs or benches, but because they require active postural engagement.
How Exercise Balls Work Under Load
The physics of an exercise ball is governed by a few basic principles. First is air pressure. A properly inflated exercise ball maintains internal pressure, measured in pounds per square inch (PSI), typically between 0.6 and 0.9 PSI depending on the ball's size and manufacturer specifications. This pressure pushes outward against the ball's shell material. When you sit on the ball,