Ergonomist's opinion

Steve Meagher, The Ergonomics Guy, Site Solutions Online Ergonomics San Francisco, USA

Need the flexibility of a ball and the support of a chair? This may be your answer!

I had a chance to test this new ACTIVE chair SpinaliS Hacker chair and honestly, I find it to be the best chair I have ever tried. The seat is adjustable and the backrest with great lumbar support is adjustable as well.
This active sitting is great for the posture and very good prevention from any back pain, therefore I recommend this chair to the people, who need to sit every day and want to stay fit.
Just bear in mind that if you start sitting on it, in the first days you might feel sore muscles in whatever area is the weakest in your body (it might be the core, back, neck) and it just the normal reaction of your body, that is how this active sitting works, it is like kind of exercise in the gym, but I am sure you already know why is that good for our body.

Generally, activity is much better for our muscles than inactivity, so you need to think about this chair as an effective way, how to stay fit at your workplace. 
To get back in shape or relieve an existing problem, is a process and this chair will definitely help you with it. So I am saying, it will not happen overnight, that you will feel great in it. Usually, the second week is much easier even for people having weak core or back muscles, when the muscles are adjusting and strengthening day by day, more and more. Then it is a huge relief even for people having back issues, back surgery, or even after a car accident suffering from the previous back pain.
The longer you will sit in it, the better you will feel. 
Yours Sincerely, Steve Meagher