This movement is used to isolate the triceps, and build mass in the back of your arms.
Start by placing one arm and one knee onto a flat bench. Pick up a dumbbell with your free hand. Next, raise your elbow up, so it is above your core. Your upper arm should be parallel with the floor and your forearm should be hanging straight down. Begin the movement by squeezing your tricep and pushing the dumbbell back and up until your arm is fully extended. Hold the top position and squeeze your triceps muscles hard. Next, lower the dumbbell back to the starting position using the same arc that you pushed the dumbbell with. Repeat this movement until you complete your set.
Keep your upper arm still as you complete this movement. There is a tendency to cheat by swinging the upper arm, but make sure to control the weight throughout the entire exercise.
This movement can be done standing with two arms or one arm at a time. Stand up with the dumbbells by your side, bend at the waist, and complete the movement as described above. This movement can also be done on a low pulley machine.