Difficulty - Moderate
Muscle Groups Addressed - Delts, Triceps, Lats
A favorite I picked up from a friend in college, these are named for the absolute opposite of what you're supposed to do! In the gym, pick a dumbell or barbell weight that you can curl comfortably. Lie down on a bench and put your feet flat on the floor. Grip the weight with both hands and hold it above your chest.
To execute this exercise, you can perform it one of two ways.
1.) Keeping your upper arms and elbows locked in place, slowly bring the weight directly down to your forehead (hence, skullcrushers) but do not touch your forehead and, goes without saying, definitely don't DROP it to your forehead, unless you're training for a headbutting competition. You should feel tension solely in your triceps. The motion looks like this:
2.) To take some tension out of your elbows, and to work more secondary muscles, you can also perform the exercise by keeping your arms locked and bringing the weight behind your head in a sweeping motion. You should still feel this in your triceps, but also in your lats (upper back) and delts (front shoulders).
Perform the same motion with a ream of papers or a heavy book at your desk. Sit up tall in your chair. For the first variation, bring the book from behind your head, straight to the ceiling. For the second variation, bring the book from behind your head down to your lap and up again. Good luck, and in the immortal words of Tony Horton... "Don't smash your face!"