After years of sitting in a conventional office chair, I tried this seat variant due to lumbar spine problems. The approach seemed to me during the ordering process is still somewhat risky, but worth a try. The experiment paid off. The lumbar problem due to the rigid sitting on the conventional desk chair barely registers. I use this 'chair' daily 4-10 hours. The structure of the seat a miraculous took place smoothly, about 1 x per month requires the Fitness Ball inside an air supply. Recommendation on the edge: If you like soft sitting should definitely inferior to a ceiling.