A stability ball is a large, squishy ball that’s used during workouts to improve strength and balance.
Normally around two to three feet in diameter, they’re used to provide a base for exercises like push-ups and planks. Because they’re wobbly and unstable, the body needs to use more muscles to keep steady, so stability balls are a good way to engage a lot of muscles while improving balance and stability  They can also reduce strain on the muscles and spine, so stability balls can be a good way to help people who are recovering from injuries get back into shape.
Also known as a Swiss ball, exercise ball, and a balance ball.
- Electromyographic comparison of a stability ball crunch with a traditional crunch. Sternlicht E, Rugg S, Fujii LL, Tomomitsu KF, Seki MM. Department of Kinesiology, Occidental College, Los Angeles, California.Journal of Strength and Conditioning Research, 2007 May; 21(2):506-9.⤴
- Do exercise balls provide a training advantage for trunk extensor exercises? A biomechanical evaluation. Drake JD, Fischer SL, Brown SH, Callaghan JP. Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, Ontario, Canada. J Manipulative Physiol Ther. 2006 Jun; 29(5):354-62⤴