When choosing an exercise ball, you can consider your height and how you plan to use the ball:
Height (diameter) of the exercise ball is based on your height
Here is the recommended height, or diameter, of the exercise ball based on your height:
| Exercise ball diameter | Person's height |
|---|---|
| 45 cm | 5' and under |
| 55 cm | 5'1"– 5'8" |
| 65 cm | 5'9"– 6'2" |
| 75 cm | 6'3"– 6'7" |
| 85 cm | 6'8" and taller |
The ideal size is when you sit on the ball, your knees are at a 90-degree angle and your hips align with your knees. If your hips are lower than your knees, the ball is too small.
If you have relatively long legs for your height, you might want to consider going up a size.
It is easier to maintain the natural inward curve of your lower spine if you have a slightly taller ball to sit on.
You can also slightly adjust the air pressure in the ball to reach the right height.
How to sit on the exercise ball
Follow these steps for posture that protects your back while sitting on the ball:
- Both feet should be flat on the floor - with an even weight distribution.
- Knees should be level or very slightly lower than the pelvis (hips) - creating an angle of 90 degrees or slightly greater at the hips and knees
- Both thighs are parallel to ground or pointing down very slightly
- Pelvis (hips), shoulders, and ears should be in a vertical line - the body should not be leaning in any direction as a counterbalance. Bouncing up and down lightly will usually produce this alignment.
See Commonly Prescribed Exercise Ball Workouts for Back Pain
Body weight may be a factor in your selection
If your body weight to height ratio (or BMI) is greater than the average proportion, sitting on the exercise ball will compress it down more, so individuals usually should try using the next larger exercise ball size to maintain the 90-degree rule.
A commercial grade exercise ball may also be preferable, as these generally are made more durable.
Exercise balls can be customized by adding or releasing air
Most exercise ball sizes have some adjustability to them. For example:
- If the angles at the hips and knees are much greater than 90 degrees, some air can be released to compensate.
- If your hips are lower than your knees, then some air can be added to compensate.
Bear in mind, releasing air from the exercise ball will make it flatter and more stable, as it has a larger contact area with the resisting surface and the body.
This means that stabilizing and balancing exercises will become both easier (good for beginners or anyone with balance issues) as well as less effective at building core strength as you make progress with building strength.
Here are examples of when you may want to add or let out some air:
Deflate the ball slightly for extra stability when:
- Initially beginning to use this type of ball for exercises and rehabilitation
- Using the ball as a chair while working at a desk
- When you have difficulty with balance and coordination
Inflate the exercise ball when:
- You are making progress with your exercise routine; your abdominal muscles and low back muscles are now stronger and you need to have more of a challenge to keep building strength
- Your exercise ball has deflated slightly with use, your knees are no longer at a right angle when you sit on the ball, so you need to add more air back in
As a general rule, the firmer the ball the more difficult it is to stay balanced on it because it takes more strength from your stabilizing muscles.
On one final note, congratulations on researching your options for an exercise ball, as physical therapy using an exercise ball is a part of rehabilitation and helps in pain relief for many people.
