Do you mean the arm guards? There have been ones like that in history and they double as an offensive weapon. They're not rounded, though, like those. They did that for the obvious but subtle turtle shell effect like the pattern on the sides.
They usually were rectangular and flat with a ribbing that reinforced them and you could bend your arm and whop someone in the jaw with the part that protrudes, picture a sideways uppercut where your fist misses the target but that cocksucker connects sideways. It hurts like a son of a bitch and can potentially crush your carotid but I don't know if it ever happening. It's essentially a wearable version of a shield with very limited offensive capabilities.
If you did mean shoulder guards that's just their Friday the 13th part two style bag mask loosely draping on their shoulders.>>7753623>>7753731