The Perfect Deltoid Exercise
If you want arm definition, you need to add the dumbbell lateral raise into your routine. It is perhaps the best way to work the deltoids, particularly the medial deltoid.
To perform the exercise, start with a neutral grip (palms facing in). Raise the dumbbell to shoulder height turning your thumbs up in the process. This is important because it takes the stress off the rotator cuff. Your thumb should finish above your pinky,
Weight for this exercise will depend on the user, but in most cases a dumbbell between 10 and 20 pounds is appropriate when performing the lateral dumbbell raise.
When To Do The Lateral Raise
I usually recommend adding this routine to your shoulder day routine, towards the end of the workout. You can perform the lateral raise up to twice a week, but make sure that you get one to two days rest in between sessions.