The spiraling movement of Tai Chi sports is known as reeling silk. With practice, reeling silk movement develops muscle memory that allows your skeletal system to align and coil like spring.

Tai Chi sports core movement of Reeling Silk embraces the principles of yin and yang.
Yin centrifugal action spirals out and away from the center, while yang centripetal action spirals in and towards the center.

Keeping your center geographical fixed will give your Reeling Silk centrifugal and centripetal action more force. We call this action "clutching" this is one of the keys in Tai Chi Sports.

This means that your knees, the front one should also be clutched, it should not move backward and forward when you are in a fixed stance, giving greater force to your Reeling Silk centripetal /centrifugal action.

This aspect of clutching is crucial to how you move when playing Tai Chi Sports. e.g. Your Spine should rotate on the spot but NOT shift geographically with weight changes from one leg to the other.