Arnold Press

Stand with your feet hip-width, holding a pair of dumbbells at shoulder height. Your elbows should be bent and your palms should face your body. In one motion, open your elbows to the sides, rotate your forearms so palms face forward, and press the dumbbells overhead until arms are straight and biceps are by your ears. Pause briefly at the top, then reverse the movement to return to start. That's 1 rep.