Get your shoulder ready for fast punches with warming up the external rotators
This exercise isolates the external rotators of the shoulder during arm extension. The upper arm is held horizontally, with the shoulder and elbow forming a 90-degree angle. The hand pulls the tube backwards and then returns to its starting position, while maintaining the elbow’s position in the air.
In the video you can see ATP Pro Dominik Koepfer in his time just before moving to college