Help me settle a "discussion" with a co-worker:  what are these contraptions on the utility lines?

utility lines

My co-worker thinks that they are "splices" in the cable; I think that they are "stress relief" device, designed to "give way' before the cable snaps.  Do you have any idea what the purpose is??  Here is a closer shot:

utility wires (Staff photo)

Someone please help us settle this "discussion"... thank you!!