Previ Fitness: Choosing the Correct Size Stability Ball

Stability (or exercise) balls have become extremely popular for workouts and even to use while sitting at your desk! While they come with many different names, they are an inexpensive piece of equipment that can ramp up all of your exercise efforts. The instability caused by the round surface makes your entire body work harder to maintain balance no matter what exercise you are performing. However, most people are not aware that effectively performing stability ball activities requires the correct ball size.

There are several guidelines to use when selecting the proper stability ball. When sitting upright on a stability ball:

exercise ball

  • Feet should be flat on the floor – with weight evenly distributed.
  • Knees should be level or slightly lower than the pelvis – creating an angle of 90 degrees or slightly greater at the hips and knees (thighs parallel to ground or pointing down slightly).
  • Pelvis, shoulders, and ears should be in a vertical line – the body should not be leaning in any direction (acting as a counterbalance). Try lightly bouncing up and down it will usually produce this alignment.

Stability balls generally come in five different sizes, according to body composition. Height alone is not the only factor in determining ball size! Stability balls are flexible and therefore when selecting a ball, body weight is another important factor to consider.

A general guideline for using height to determine the correct diameter of the stability ball is as follows (this is assuming average body weight that is proportional to height):


If your body weight to height is larger than average, sitting on the stability ball will compress it more. To prevent this, try using the next larger ball size in order to maintain the 90-degree rule.  Another thing to keep in mind is that stability balls do have some adjustability to them. If the angles at the hips and knees are  greater than  or less than 90 degrees, some air can be released  or added to obtain the proper 90 degree leg angle.

You should remember that releasing air from the stability ball will cause the ball to flatten. When the ball has a larger contact area with the floor and the body it becomes more stable. This means that balancing exercises become easier and lose some of the desired effectiveness. Alternatively, adding  more air to the exercise ball will increase the difficulty of balancing and stabilizing, as the contact area decreases;  just be sure not to over inflate your ball (each manufacturer will have suggested guidelines). Additionally, stability balls tend to lose pressure with regular use due to stretching so keep an eye on the inflation level and adjust as necessary.

Now that you know how to pick the proper size stability ball you can feel confident making a selection!  They come in a wide variety of colors, not to mention they are great for increasing balance, strengthening the core and make every exercise (or sitting at your desk!) seem a little more fun. Happy exercising!

If you are interested in learning more about our exercise program and how it can complement your nutrition plan, please contact us at 855.773.8463 or email us at

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