I don't keep all of the links on the information I have read over the years, but will look through some of my stuff and see what I can find. The two places I know I have read is at Eric Cressey's and drivelinebaseball's site. Dr Bogonzi did his Phd on weighted baseball development over 20 years ago and I know I have some PDF's on the subject, but the modern weighted baseball programs are completely different now, drivelinebaseball has some stuff on them and of course Ron Wolforth. I believe ASMI (or one of their Dr's) did the lactic acid study if I recall correctly. Check out the p3 sports web page it will give you a very good perspective on what is going on in the high performance training of athletes.
I have an interesting story on the long distance running. When my son was a Soph in HS (my goodness 5 years ago....) I ran into a track coach who was working with HS sprinters and he agreed to help my son on speed development, technique, etc. So he would go out a couple days a week with a group of sprinters and work with them. I was talking to the coach and he said that he does not allow any of his sprinters to do any distance running as it slowed them down. At the time that is what baseball players were told to do, and I thought to myself this does not make sense. So I followed up with him and we discussed it. He did not know much about baseball training but said that in his opinion baseball players should be doing repetitive sprints just like he did with his track athletes. He had data that for his track athletes who did cross country running that they came back in track season much slower than when they left him. Looking back now it makes total sense, but not long ago distance running was considered the optimal exercise.