The inventor of the balance chair thinks about the backrest

This is a video of a conversation between the inventor, Hans Christian Menscholl, and Balance Lab's president, Sakamoto.
We asked the inventor of the Balance Chair some common questions.

In this video, we ask the question, "What do you think about backrests?"
Is it better to have a backrest? What are the benefits of not having one? We asked the inventor of the balance chair about his thoughts on backrests.