What plane of motion is used in dumbbell shrugs?

I have a major health project to work on, and I can't seem to be able to find this answer. I know the three planes, sagittal, frontal,and transverse, however shrugs do not seem to fit in any of them. It is more of an up and down motion instead of forward or backward/ side to side/ or well a transversal kind of movement. Thanks for all your help!What plane of motion is used in dumbbell shrugs?I'd say frontal plane.