The rotating bicep curl is an awesome way to strengthen both the biceps and the forearms in one fluid movement.
Simply start off holding the dumbbells at your sides with a hammer grip (palms facing each other), and bring the weights up ½ way through the curl. This Hammer grip is wonderful for strengthening the forearms! Then at the halfway point, rotate your grip so palms are now facing up, and continue to bring the dumbbells up to the shoulders. This Supine grip (with palms up) isolates and builds bicep muscle like no other. Then retrace the movement as you lower the dumbbells to their original position and for fabulous arm toning and strengthening!