Tricep extensions are a simple way to target the muscles on the back of the arms. To do them correctly, position one dumbbell over head with both hands under the inner plate. Lower the dumbbell behind your head keeping your elbows close to your ears. Raise the dumbbell over your head and returning to the starting position. Some tips: Don’t arch your back, engage your core, press straight overhead while keeping your shoulders, and make sure you don’t hit yourself in the head with the dumbbell. : )