Sit on a bench with your back straight and hold a dumbbell in your left hand. Extend your arm fully overhead with your elbow close to your head. Slowly bend your elbow to lower the dumbbell behind your head while keeping your upper arm stationary. Pause briefly at the bottom, then extend your arm back up to the starting position, squeezing your triceps at the top. Keep the movement controlled and avoid flaring your elbow.
Log your dumbbell seated single arm overhead triceps extension (left) sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.