The hammer curls will target your biceps.
Muscles Involved in order of importance:
To perform this exercise stand with your feet shoulder width apart with a dumbbell in each hand and have your arms fully extended down by your sides.
The palms of your hands should be facing inwards, towards your thighs.
Keep your body still and curl the dumbbells up, your forerms should only be moving, while keeping the weight facing inwards.
Slowly bring the weights back down to the starting posistion.If you find that you are swinging your back to curl the weight up then it is probaly to heavy lower the weight and concentrate on form rather than weight
Safety: Doing this exercise should be done with a spotter if you think the weight will be a bit too much, I also have a spotter when doing this exercise just to be on the safe side.