question

is there an actual limit to how fast a persons fastball can be, based on genetics, no matter how freakishly good their mechanics are and if they lift and eat right?

Yes.

Supposedly, the UCL can only withstand 80N or something of force, the same amount a 100mph fastball puts on the arm. Something like that…

yes there are genetic limits you inherit. no it is not 100 mph. jr richard routinely hit 103 to 105 until his tragic stroke ended an unbelievable career. what about zumaya and 103? his injury was not from pitching but a box fell on his arm (unbelievable). ryan throw 100+ in his youthful prime.

[quote=“Spencer”]Supposedly, the UCL can only withstand 80N or something of force, the same amount a 100mph fastball puts on the arm. Something like that…[/quote]ASMI had a video a couple of years ago (maybe more but that’s when I got it) that discussed cadaveric studies on the UCL. They stated that the breaking point for the ligament was at about a 3rd of the stresses that pitching puts on it. The moral of that story was that, in order for it to not fail on every pitch, the muscles, tendons and ligaments around it must contribute significantly. This is one reason why some say that early pronation protects the UCL. The pronator teres muscle runs nearby and pretty much parallel with the UCL. Early pronation is said to take some of the load away from the UCL because it activates that muscle more. Thanks to Chris for that description. It seems to make sense.