dumbbell standing one arm extension

Stand with your feet shoulder-width apart, holding a dumbbell in one hand. Raise the dumbbell overhead, fully extending your arm. Keep your upper arm close to your head and perpendicular to the ground. Slowly lower the dumbbell behind your head, bending your elbow. Pause for a moment, then raise the dumbbell back to the starting position. Repeat for the desired number of repetitions.