From a discount store I had even a stability ball for a few EUR for test can not get used to it and concerned. In addition was the then ball - I've given away later - quietschpink. Now after a few more years, it was supposed to be one for the office again, but with a more subdued color. In other reviews I read, that many a buyer after a short time of use of backache complains (which should be actually prevented by the ball). My experience with the ball after about 1 week is that I indeed stronger than usual my cross, the shoulder muscles and your thighs feel, but it feels more like slight soreness. That would be a plausible explanation for me. Because I looked years ago a comfortable office chair, which should relieve my cross by the high back, the legs by a somewhat flexible seat and arms through the arm rests. This he did quite well. Well, with the result that sitting by a well to well-intentioned physical relief by the chair, the muscles just regressed by lack of exercise before the monitor at important places. Or at least not keep active. At least I have a feeling. Well and now by the ball, the body must constantly certain muscle areas enable so I do not fall out of this rubber ball. Even a small mittägliches nap as earlier in the stool is almost impossible. I am concentrated at work and to rest I leave now rather office. One star deduction there yet, as soon as you can once the ball unoccupied cools the little rubber quickly. On cold days, he feels with every new plan set only once at a little cold. When will the first heatable rubber bullets? In addition, under the vulcanized film with the company logo was a brown piece of something. I can out friemeln's and identified the most likely as a Bruchstückchen dark chocolate. A taste test but I better not made. As the ball otherwise has no technical shortcomings, I have taken from a distance exchange.