Stand tall with feet shoulder-width apart and hold a dumbbell in one hand. Raise the dumbbell overhead until your arm is fully extended, keeping your elbow close to your head. Slowly bend your elbow to lower the dumbbell behind your head in a controlled motion while keeping your upper arm still. Pause briefly at the bottom, then extend your arm back to the starting position, squeezing your triceps at the top. Repeat and switch sides.
Log your dumbbell standing one arm extension sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.