I think people put way too much emphasis on just the pitch count and nothing more. It doesn't matter that your mechanics were horrible, it doesn't matter how you train, it doesn't matter what you do in between starts- as long as you didn't go over 120 pitches, you're OK!
I do think that pitch counts are important, but I think they're more important in something like youth league baseball because you're dealing with individuals who have not matured- and that includes their bones. Around about high school, I think there should be less emphasis on pitch counts, and more emphasis on things like mechanics, weight training, throwing programs and things like that.
To me the problem seems to be that most of these youth coaches, even today with the wealth of information out there, do not know or place enough emphasis on those things that I've mentioned. When a kid gets into pitching, there needs to be a HEAVY emphasis on mechanics. Mechanics will not prevent an arm injury, but they will minimize the risk. Pitchers should not begin weight training until they are in high school, and and any weight training that is done should be very, very light- if at all. I think what the pitchers do on their off days are equally as important as mechanics. They need to be on a regimented throwing program, and that should start in Little League as well. I know it's cliche on here, but they need ice after starts and light stretching before starts.
Once a pitcher gets to high school, they should work on endurance- pitching longer than 100 pitches up to 160 in my opinion. And like Briuser said, this is dependent on the pitcher. Some pitcher can go longer than others no matter how they train or what they do.
Basically, what's happening now is all of these pitchers are on these strict pitch counts- it's almost a "badge of honor" for your coach to not exceed these counts- "Look we're classy, no one went over 120 this year"- and some of these pitcher are getting to college and even MLB and they've never gone past 120 in their life, and then ne one is getting past the 6th inning. These pitchers aren't learning how to build their endurance, and they aren't learning how to compete late in a game.
To me, a bigger issue is all of these Little League pitchers throwing curve balls and no one is stopping it. They should fine a coach 100 dollars if one of their pitchers throws a curveball. Teach these pitchers to pitch using their fastball and teach them a changeup. It's unreal how many pitchers go through high school without a change up. Heck, I saw a pitcher that got drafted in the first round and he can throw 98, but he doesn't have a changeup to speak of. It's ridiculous.
That said, I applaud Nolan Ryan for his crusade. I think people need to be educated. That's what a lot of this is- a lack of education. (And why I knew that what the UM fans were railing Cohen about was going to come back and bite them in the *** before very long) And the thing about pitching is that it is a very unnatural motion for your body. The reason softball pitchers can throw just about every game is because underhand is a more natural throwing position for the body. Pitching put a ton of stress on the muscles of the arm, the joints and ligaments of the arm- especially if you can throw really hard and especially if you do it for any length of time. The injuries are repetitive motion injuries. It's hard to say- and not very objective- to say that OK- you threw 150 pitches against the Orioles that day, so that's where you hurt your arm. Arm injuries are something that are caused by a build up over time.