Set a bench to about a 90-degree incline. Grab a pair of dumbbells and sit down on the bench, letting the dumbbells rest at your sides. Before starting, make sure your arms are straight and palms are facing away from you.
Curl the dumbbells to your shoulders while keeping your elbows at your sides. When you reach the top of the curl, rotate your wrists so your palms now face away from your body.
Lower the dumbbells under control, again keeping your elbows at your sides, until your arms are fully extended. At the end of the motion your palms should be facing behind you.
Before beginning another rep rotate your wrists so that your palms are facing away from you once again.
Pause and repeat.