Zottman Curl

Hold two dumbbells at arm's length and stand straight up. Turn your palms up and curl both dumbbells up toward your shoulder. Keep your upper arms against your side at all times! When you reach the top, rotate your wrists so that your palm faces almost straight down. Your thumb will be a little higher than your pinky. Go back to the starting position and repeat. You can also do these one arm at a time alternately or over a preacher bench