Starting Position: Holding two dumbbells, kneel and rest your elbows on a bench with approximately a 90 degree bend at the elbows and the dumbbells hanging freely off the edge of the pad. Supinate your forearms (rotate the forearms so that the tops are along the bench and the palms are facing upward) keep your wrists in a neutral position (not in flexion or extension).
Downward Phase: Inhale and slowly allow the wrists to move into extension (allow dumbbells to move towards the floor) without releasing your grip, extending your arms or leaning forward / backward. Hold this end position briefly.
Upward Phase: Exhale and slowly contract your forearm flexor muscles (along the top of the forearm) rolling your wrists towards you in order to return the dumbbells back to the starting position.
Individuals sometimes release their grip during the lowering phase, allowing the dumbbells to roll towards their finger tips. While this may increase the load on the forearm muscles, it also increases the risk of wrist injury and dropping the dumbbells. To increase strength think about squeezing the weights as hard as possible during both phases of the movement.