I shed some pounds then practicing low kicks went "shin to shin" with a guy, nearly broke my fucking leg, was hobbling around the mat, instructor told me I had to toughen my shins by hitting them with the butt of a pool cue and then rolling it up and down my shins..
I went traditional boxing not long after that.
LOL! Can't blame you.
When I was a "musclehead" from my early teens to late thirties, I guess I was smart because I intuitively understood a trained fighter would fuck me up. THE only advantage I ever thought I had was an intimidation factor over a much smaller, generally laid back scrapper: a self-doubter who was plenty tough but maybe hadn't fought a built guy before.
That advantage as such would end if he didn't back down and we fought.
I could bluster about my pain tolerance, how I would fight dirty, etc., but that's all bullshit. Even if I somehow made the trained fighter "feel it" later, I'd be the dude staggering around later, probably looking for the nearest ER
Specificity. Selye tackled the subject with aplomb decades ago. That's not to suggest very muscular, strong men cannot fight. They can. But as with everything, they need to train to fight to be good at it.