Believe it or not I recently talked to Jake LaMotta- I asked him about this- He said, "I trained myself." What he was saying was his not going down, his being so tough was nurture not nature- mind over matter- make of it what you will.
During the 1970s, he discussed this with Curt Gowdy when reviewing the Valentine's Day Massacre on Gowdy's "The Way it Was." He actually used the term "self-hypnosis" to describe the mental conditioning with which he convinced himself he could not be hurt by the other guy. And because he consequently didn't flinch, he could see the punches coming and move that imperceptible fraction of an inch necessary to ride out the maximum impact of a blow. (Keep in mind that the knockout blow is often a punch not seen by the victim.) He obviously had terrific vision. (Is there a photograph of Jake anywhere showing him wearing corrective lenses?) That fraction of an inch in movement and protest of having underrated defensive skills is something LaMotta shares with Chuvalo. George also thoughtfully and articulately analyzed the physical template for punch resistance, and it's a template Jake shares with Chuvalo. Beyond that, keep in mind that LaMotta was a LHW in the amateur ranks, supplying him with additional punch resistance when he moved down from 175 to 160 to compete in punch for pay. There does seem to be elements of both nurture and nature involved with Jake. (Younger brother Joey will turn 87 in April, and the brothers LaMotta certainly appear to share favorable genetics.)
Well said! I agree that there is an element of nature as well. 'Course, he needn't concern himself with that because that is there or it is not. That fraction of an inch movement is so evident when you watch him. He sure was a cool customer in there, never rattled.