Skull Crushers / Lying Triceps Extensions (Dumbbell)
- Lie flat on a horizontal bench, grip two equally weighted dumbbells a neutral grip (thumbs facing backward, i.e. toward your shoulders when in the down position) at about shoulder-width apart, and press it vertically until your arms are extended (the weight should be somewhere within the range of above your chin to farther back in the direction of behind your head). Note: When you're training alone the safest way to get the dumbbells into position is to lift them off the ground, sit with them resting on your lap, and then, in one fluid motion, lie backward on the bench and position the dumbbells above your shoulders.
- Lower the dumbbells either to beside your forehead on each side or behind the top of your head on each side, inhaling throughout the movement. See "Further Clarification" for elucidation on how the difference in manner in which the bar is lowered (to your forehead or behind your head) changes how the muscles are worked.
- Raise the dumbbells until they reach the starting position, while exhaling throughout the movement. Do note that your elbows/upper-arms should remain in a relatively stationary position for both the negative and positive aspects of this exercise, unlike the pressing motion found in chest exercises.
- Repeat steps 2-3 for as many repetitions as are desired.
When the dumbbells are lowered to your forehead both the lateral and medial aspects of your triceps will primarily be worked. When the dumbbells are lowered behind the top of your head (remember, you are lying down) the long head of your triceps will primarily be worked.
For some, the completely free range of motion of this exercise may prove challenging, as the dumbbells are in a perilous position (above one's head) that can be wobbly, awkward, or uncomfortable. There are two good solutions to this potential problem: either lessen the amount of weight that your are lifting, or, instead, do lying triceps extensions with a barbell until you feel stable enough to do them with dumbbells. Also, most people will not be able to perform dumbbell lying triceps extensions with as much weight as they can with a barbell. This is normal.
Elbows are particularly vulnerable to injury with this exercise. Be mindful of any strain that you feel, and adjust the weight accordingly.