The gym ball in question is the one used in yoga or Pilates training. They come in two sizes, 65 cm 75cm (diameter). I had recurring back pain, and decided to give it a try at home. I don't think my University would allow me to switch a 100€ office chair for a 8€ gym ball, also there is no place to put my chair.
For more than two months I have been using it at home. In July I gave up: if it is too hot, it is not very comfortable. You can solve it putting a cloth over it.
But the results have been very, very interesting. I'll explain you the results as a list of questions and answers.
Can't you fall off the ball? Absolutely not! Unless, of course, the ball is not the right size. If you are less than 1m80cm (around 6 feet), you need a 65cm ball, and consider a bigger one if you are taller. If the ball is the correct size, your body will be in the vertical of the ball and you can't fall, at least you can't fall easily. Also, try several inflate strengths. A 75cm ball is different at full strength than at half strength. Try different inflate levels.
Don't you get tired? Indeed. At first your back muscles are not used to that much support work, and you will get tired and have strange feelings in the lower part of your back. It will be getting better over time. For the first weeks or months, keep your old chair around just in case. Also, try not to sit on it for longer than 5 hours every day the first weeks.
Won't you roll around on it? Yes and no! The good point of using a gym ball is that you are not completely steady. You move a little (no more than a few cm around) and this keeps you from being completely still. This helps a lot with back pain, which usually comes from a very tight posture for long stretches of time. With a ball, there are no big stretches in the same position. Also, when you are feeling high, you'll start rolling your hips back and forth over the ball, or start bouncing off it. It is kind of fun seeing, but more fun doing.
Won't it explode leaving you on the floor with a bruise in your arse? In my experience, no. I have bought the cheapest available and it doesn't look as if it will explode any time soon. It is very thick, and from seeing it, I think it would deflate very, very slowly if a hole appeared on it.
What if I have back problems? If they are severe or you have a medical condition, don't try it without asking your physician. If you just have "standard" back pain, give it a try. I did, and I don't regret it at all.
In case you are wondering, I weight 70kg! And 8 people I know (either friends or friends of friends) started using them at their offices or homes. And I heard no regrets!
You can find a gym ball in your local sports store, Amazon (affiliate link) or shopping mall. Give it a try and let me know how it felt.
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