From what I hear, it's not the fastballs that mess up their elbows but those funky breaking pitches. You look at the old school guys that lived on a primary diet of fastballs, they didn't have so many arm issues. But also they're being taught those funky pitches at a younger age and putting their arms under more stress playing with those traveling teams so by the time they get to the majors those young arms aren't so young. We'll see how long this new phenom Skenes in Pittsburgh lasts before he inevitably hits the Tommy John wall. They're saying he's the next Strasburg.