K3a Lumbricals Right Hand
Place the hand trigger on the top of your left wrist with your left arm flat on a table.
Extend your right wrist so your hand is pointing upwards, bend all 4 fingers from the knuckle so they hover over the hand trigger. Tap in time to the beat by flexing the fingers from the knuckle joint trying to keep the fingers straight as you do this your wrist should not move as you do this exercise.

K3b Lumbricals Left Hand

As K3a but swap hands