When you sit you are putting weight on your back neck feet legs and your entire body. Yet, your weight is not distributed equally. Depending on the structure of your chair, your posture and how you sit you may be putting extra stress on certain areas. A FoMI footrest allows you to align your weight, place stress on the mat and reduce stress on your body.
The rocking motion allows you to transfer weight from one side of your body to the other which may reduce long term stress on your legs and back.