I think overwork or underwork is a problem, but it is only part of the main issue. Yes, it you work to often or to long, fatigue can set in and that increases the chance for injury. But, the biggest issue is no longer workload. The biggest issue is what pitchers are now trying to do with their pitches. Pitchers are trying to increase their pitch velocity to the upper nineties. They are trying to increase their spin rate, etc. As you mentioned, this is putting more stress on their arms. They have access to all these modern pitching metrics and they believe that in order to become a great pitcher you have to work on improving and increasing all these things. There is some truth to this. But these are also the things that are putting to much stress on pitching arms and it is ultimately what is causing these major injuries. Pitchers can work on improving velocity, spin rate, etc., but there needs to be balance to figure out how much is to much. The price they pay is sacrificing a long pitching career for a half dozen or less good years. The number of big injuries to pitchers has increased greatly in the last dozen or so years. We have the metrics, but there needs to be more science on how much these arms can take and how can a pitcher become a smarter pitcher and stay within what their arms can handle.