What muscle does it work? Bicep? Lats? Tricep? Do dumbell skull crushers do the same for you as normal skull crushers with the use of the normal barbell?
It works your triceps; your secondary muscle group would be your biceps. If you feel it anywhere else, like lats or delts, your form is off (it's an isolation exercise), so stabilize your body and shoulders. Dumbbells are always more difficult than barbells, because the weight isn't being balanced by both arms -- it utilizes your body's natural muscle stabilizers, which take awhile to get stronger. If it's too difficult to do dumbbells, either drop the weight or go to barbell until you have strengthen up your tricep muscles and can do the full range of motion. Good luck!
