Since using the Gaiam chair at my computer, my back and hip pains have almost completely disappeared. IT forces you into good posture and you automatically pull in your stomach muscles while you sit.
Be sure to get the right size for your height. The chair is very easy to assemble and was a great bargain. It has been a great ergonomic addition to my office and has improved my posture and reduced my neck and back strain. The chair is also a space saver compared to the previous office chair I used.
I use the chair everyday at my office, but not for any exercise. It is good for that, but I cannot speak for exercising and stretching. The material is all plastic with one metal bar holding the ball on the front of the chair. The materials are on the cheap side. The plastic is about what I would expect in a toddler's play toy and the metal bar should be about twice the diameter with a better method for how it is connected to the chair. The bar has broken on my chair after about 8 months of use, but support was very nice and quickly sent me a replacement piece. The nuts for the ends of the bar should be much wider so they have a better purchase on the plastic. Even with the lower quality, it is sufficient for my uses and I am happy with it.
I was a bit concerned reading the description and the reviews because the chair is recommended for people 5 '6" or taller--and I'm 5' 3", maybe 5' 2.5". In any case, it's perfect! I sit on the top of the "chair" and my feet easily sit flat on the ground. However, it is hard to "bounce" very much while trying to read or type so I'm not about to use the lymph circulating properties as much as I would like.
Metal bar in the front that holds the weight of the ball as it expands when I sit on it pulled through the plastic on both sides. I kept it inflated but it didn't help relieve the pressure. Once the plastic broke the chair is worthless. Disappointing!
I needed a new chair for my desk and I am so happy I bought this one. If you are hesitant, just purchase it- you won't be disappointed. Very easy assembly. I only had to pump up the ball again the second day. I am a graduate student and this chair is perfect for studying while maintaining a healthy posture. I did buy the extenders to make it taller.