This exercise works the entire tricep most specifically the medial and lateral heads. It especially works the beginning range of the tricep. It gives a fuller range of motion than does the two handed exercise.
How to do:
1. Stand erect with your feet shoulder width apart ,a dumbbell resting on your shoulder with both hands supporting its weight(thumbs wrapped around bar
2. You should hold the dumbbell with a regular "curl" grip. The starting position should look like the weight is being used to scratch the upper back.
3. Holding the upper arms still, inhale, lift the weight, keeping your elbows pointed straight up throughout the movement.
4. Pause at the top of the movement, exhale, lower and repeat the entire movement.
5. You do not need to fully extend your arm(s) during this movement. The tricep is at it's strongest when your arm is bent at a 90 degree angle. If you fully extend your arm using heavy weights you can cause major compression and possible serious injury to the elbow joint.