Hold two dumbbells in front of your chest with your palms facing toward your body, keeping your elbows close to your body. This is your starting position.
Press the dumbbells up above your head, rotating your palms out so that when you reach the overhead position, they face away from your body.
Reverse the motion to lower the dumbbells back down, corkscrewing your hands so your palms end facing your body, and repeat.