This is how you prepare your upper body for the training session before you go on court, as part of the mobilisation in the warm-up program

Stand upright with your legs about hip-wide and cross your arms in front of your chest.
Tense your trunk, buttocks and leg muscles and slowly lower your upper body forward. In this position turn your upper body to the right and start to circle.
Pay attention to the stability in your legs and torso. Change direction after each round.

Repeat:
Two or three times in each direction.

The joint fluid and the cartilage layer take over the function of a shock absorber in every joint and reduce the frictional forces that arise. The more synovial fluid and the thicker the layer of cartilage, the better the joint is protected against injuries and the longer it remains efficient. In order to achieve this, it is important to regularly activate blood circulation and synovial fluid.

My recommendation: mobilize each joint at least once a day with circular movements.