The USA Baseball Medical/Safety Advisory Committee recommends limits of 50 pitches per game and 2,000 pitches per year for 9- and 10-year-olds, and 75 pitches per game and 3,000 per year from 11-14. The limit rises to 90 at ages 15-16 and 105 for ages 17-18, with no more than two games a week.
Looking back, Harvey said he ramped up his arm for events as a teenager.
"At 16 how much strengthening or throwing are you really doing in between those tournaments before you have to go blow it out again?" he said.
Dr. Gary Green, MLB's medical director, said the sport has been collecting data on injuries and lengths of layoffs in both the major and minor leagues since 2010. However, innings and pitch counts as amateurs aren't tracked. Dr. Bert Mandelbaum, MLB's director of research, is heading the probe.
"We're looking at it in terms of the demographics: Can we predict who is going to get this injury? Is there something in their training? Is there something in their biomechanics?" Green said.
Fleisig concluded "how much you pitch and how hard you throw are the dominant factors."
After Dr. Frank Jobe's pioneering operation on John in 1974, there were no more than four similar operations annually until a spike to 12 in 1996, according to research by Jon Roegele, who writes for the Hardball Times and Beyond the Box Score. The figure rose to 43 by 2003 and 69 in 2012 before dropping to 49 last year.
Tom House, the former big league pitcher and pitching coach, has advocated strengthening muscles in the kinetic chain involved in throwing. John thinks the opposite approach should be taken.
"These guys today, they spend more time in the weight room than they do on the mound. Strengths and weights are fine, but if that was everything, then Arnold Schwarzenegger would be a 20-game winner," John said. "They just get so big and strong that there's very little elasticity in their arms."
AP Sports Writers Mike Fitzpatrick, Jon Krawczynski and Paul Newberry contributed to this report.
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