SETUP: Set up a secure barbell or a Smith machine to about thigh height. Lean into the bar and take an overhand-grip, arms extended. Keep your abs tight to maintain a straight line with your body.
REP: Bend at the elbows, gripping the bar hard, to enable you to drop down level with (or even slightly lower than) the bar, then flex your triceps HARD to drive your body back up to the start point.
TIP: Although bodyweight versions of exercises are usually slightly easier than weighted versions, this exercise is SIGNIFICANTY HARDER than weighted skullcrushers due to the sheer number of assistance muscles activated to prevent you from faceplanting the ground.