One Arm Tricep Extension (Dumbbell)

Grab a single dumbbell and stand upright with your feet shoulder-width apart.

Lift your arm up so that your elbow is bent at a 90° angle with your forearm pointing straight up.

Keep your upper arm close to your side and your elbow in, then lower the dumbbell behind your head as far as you can.

Squeeze your triceps and push the weight back up to the starting position.

Repeat the movement for the desired number of reps, then switch arms.