Short sword of sloth does not affect speed
I didn't even know this is may exist, but I got two of them (and nothing else) from one of the new boss monsters (Dolly, master swordsman).
My speed without wielding one was 101, wielding one it also wasl 101 and while wielding both it still was 101. Also energy cost was unaffected.
Edit: attached save file (for p14).