seated forearm supported wrist extension exercise using dumbbell with opposite hand assistance for controlled movement.
Sit on the chair, rest the forearm on arm rest with hand is off the arm rest such that palm facing towards the floor with holding a dumbbell. Using the asistance of other hand, move the wrist towards the ceiling, lower the hand to starting position and repeat.
Nothing here is a prescription. Your physiotherapist decides which of these are yours, and when.
