The player warms up his wrist before training. For this purpose, the forearm should remain stable. It is easier if the forearm is held with the other arm just before the joint. 

To mobilize the wrist, extend the hand flat with the palm facing up. Now swing the hand outward as far as possible and let it fold down from here. Then swing it inward as far as possible. Slowly place the wrist back up, making sure to keep the fingers extended. 

2 to 3 rounds and then switch hands.