Small joints at the extremities: wrists and ankles. They have the strength to take the weight of the whole body, sensitivity to give us feedback about subtle changes in placement, and can give precise direction to our efforts.
This session is mostly drills to bring relief to our abused wrists/elbows/shoulders, from over-use of electronic gadgets. These actions are good by themselves, and also good preparation for asanas where wrist/ elbow/shoulder strength is called for.