Place a pencil across your palm and bend your fingers around it so that one end sticks out of your fist on your thumb side.
When ready, move your thumb from one side of the pencil to the other.
Focus on the movement of the base joint of your thumb.
Aim to keep the end and the knuckle joint of your thumb straight or slightly bent during the exercise.
Modify the difficulty of the exercise by adjusting how much the tip of the pencil comes out of the fist.
