Dumbbell Extensions are a strength training exercise primarily targeting the triceps, the muscles located at the back of the upper arm. To perform this exercise, you typically hold a dumbbell with both hands above your head, arms fully extended. Then, you lower the dumbbell behind your head by bending your elbows, keeping your upper arms stationary, before raising it back to the starting position. This exercise can be done seated or standing and is effective for building upper arm strength and improving overall arm definition. It's important to maintain proper form to avoid injury, ensuring that your elbows stay close to your head throughout the movement.