Their Mu (μ) receptors! A class of G-protein-coupled receptors in the nervous system that bind both internal (endogenous) pain-relieving peptides and external opioid drugs like morphine. All junkies know this

Yes I think this is very true of the empty handed arts in particular.
Ironically, I think itās the dignified presence/grace/character (āhinkakuā) that the martial arts bestows upon the practitioner that provides 99% of self-defence.
I had to walk through a dodgy area of town last night to and from a restaurant with my other half. I held her hand, stood tall and walked with vigilance (zanshin) making eye contact where necessary and I think I radiated confidence that made us an unpalatable target. That or the fact Iād obviously solid the back of my trousers
Rather than nutritionally-innutritive ice cream, a better analogy would be some sort of whole, plant-based food because like that kind of food, TMA are
very good for those that practice them.