Instructions:

1. Sit on a bench with your back straight and feet flat on the ground.
2. Hold a dumbbell in both hands with an overhand grip, and raise it above your head.
3. Bend your elbows and lower the dumbbell behind your head, keeping your upper arms close to your ears.
4. Extend your arms and raise the dumbbell back to the starting position.
5. Repeat for the desired number of repetitions.