UF studies pitch clocks, overuse injuries in baseball pitchers

player holds two baseballs by his side
By Jose Francisco Morales on Unsplash

A high school pitcher looking back at early baseball aces might wonder why the modern arm — their arms — are so prone to overuse injuries.

Today, managers at the high school level and beyond limit a player’s pitch count and pull them from a game after a set number of throws, often short of 100. A complete game is a rarity.

In the age of Hall of Famer Cy Young and pros of his day, arms seemed touched by the gods. Nobody counted throws. Players threw as much and as often as needed, often without injury. Complete, nine-inning games were common. In 1920, two opposing pitchers tossed 26 innings in a marathon ended by darkness with a tie score.

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So, what’s up?


A new study led by University of Florida Health sports medicine physicians and researchers introduces what they call a unique workload model that moves beyond pitch count in assessing the risk of chronic, overuse-arm injuries in high school pitchers. The model incorporates pitching velocity, intensity and a teenager’s age, suggesting higher measures of each aspect heighten injury risk.

The study, led by UF Health musculoskeletal and sports medicine specialist Dr. Jason Zaremski, is a window into the race to throw harder and faster in high school as teens seek an edge to advance to college competition and, just maybe, the pros.

Dr. Jason Zaremski
Courtesy UF Health Dr. Jason Zaremski

“Players of previous generations mostly weren’t throwing as hard as players do today,” said Zaremski, an associate professor in the UF College of Medicine’s department of physical medicine and rehabilitation and director of the UF Health Throwing Clinic. “They weren’t throwing all year round like many do today. And quite honestly, they were smaller, not as fast, and not as strong as players now. It was a different game.”

The study was published in the American Journal of Sports Medicine earlier this month and is funded by the Orthopaedic and Research Education Foundation and the Aircast Foundation.

Many high school players now participate in six- to eight-week weighted-ball programs, in which they practice with heavier baseballs to increase arm strength. This training, increasingly common among older teenagers, can speed a fastball by up to 5 mph. However, they also increase the risk of injury by up to 25%, Zaremski said.

The UF Health study followed 71 pitchers, ages 13 to 18, primarily in Alachua County, between 2019 and 2023, recording 313 pitching outings, more than 24,000 throws, and tracking injuries.

All players were monitored using a new workload model developed by Zaremski’s team that incorporates pitching velocity and pitch counts, as well as a new measure of pitching intensity.

Game pitch counts and a focus on reducing overuse arm injuries have transformed baseball since the 1970s, especially in the last decade. Coaches and sports performance experts have increasingly realized, however, that a new paradigm might be needed.

A young child can play catch with their dad all day long. Pitchers, however, with mature or maturing bodies test the mechanical limits of their arms each time they throw a ball over 80 mph.

Zaremski and collaborators introduced a new way to measure pitching intensity.

The study divided a player’s preseason throwing velocity by their speed in the season. If a pitcher throws 70 mph before the season and 70 during a regular-season outing, their workload is 1.0.

“That tells us they’re working as hard as they can in the season,” Zaremski said.

The idea is that throwing at a greater velocity in the season pushes the workload greater than 1.0, which would be expected to increase arm injury risk.

The study showed that higher intensity, velocity, and older age in high school athletes heightened the risk of throwing-related injuries.

“An older adolescent has gone through some skeletal maturity, which means you’re going through puberty, which means you can develop more power, more muscle mass, and can throw harder,” Zaremski said. “That heightens injury risk.”

While high school leagues impose pitch-count restrictions, he said, they are not measuring either velocity or the change in velocity from preseason to regular season games.

That combined measure, Zaremski said, needs to be considered.

“We know that the bigger, older player that’s throwing faster, they’re the ones with the increased risk of injury,” Zaremski said. “We have to be a little bit more cautious with them. We also have to come up with better ways to prepare for the season to prevent arm injuries, looking at different types of conditioning, maybe more rest off-season, and strengthening young arms in different ways.”

This, he noted, is the next evolution in baseball.

“Go back to Babe Ruth’s day,” Zaremski said. “Today, the average major league fastball approaches 95 miles per hour. Babe Ruth didn’t face anything close to that average velocity.”

Zaremski’s study, focused on high school players, does not argue that one era’s players are better than any others. Even so, all athletes, in all sports, are bigger, stronger, and faster today, even in high school.

He acknowledged it’s difficult to check a 15-year-old’s baseball ambition.

“That training for higher velocity might mean making the varsity team and maybe attracting the eye of a college scout,” Zaremski said. “The tradeoff can be injury.”

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