Hold a barbell with a pronated grip and sit into a squat above parallel and rest your forearms on your thighs with the wrists in front of the knees.
 
Allow your wrists to flex, then extend them to lift the bar back up as far as possible.
 
Purpose
The barbell wrist extension strengthens the wrist and helps keep the wrist healthy by adding some balance to the large volume of wrist and finger flexor work in weightlifting.
 
Programming
Generally sets of 10-30 are appropriate.