When sitting on a Wigli you make small involuntarily movements to keep yourself in balance. This keeps the muscles in your back and abdomen working, rather than that they are slacking while sitting.
A major difference between a Wigli and most other solutions for active sitting is that the tipping point of the seat is at Wigli just below the seat. This allows your pelvis to tilt in all directions. When your pelvis tilts, the spine moves along. Your back will thus remain smooth and the vertebrae do not collapse, such as when sitting on a static chair.
If you sit on a Wigli, you prevent back problems. Do you suffer from back pain caused by sitting? Wigli helps.