Because I work in a library and consequently I always have some books around me, I can do today’s exercise to increase the strength of my wrists and the forearms conveniently during a short coffee break or occasionally during work.
I take a large and heavy book in my right hand. The palm looks upwards, my forearm straight forward and my elbow is close to my torso. The right arm should move as less as possible. Now I start lowering my right wrist with the book as far as possible and then I bring it back up. After a few repetitions I take the same bock into the other hand and go on.