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Will An Innings Limit In 2021 Actually Reduce Injury Risk For Pitchers?

Stephen Strasburg Dougmurraygetty
(Getty Images)

Thanks to 2020, many expect 2021 to be the year of innings limits.

After a coronavirus pandemic wiped out the 2020 minor league season and cut Major League Baseball's season to 60 games, there has been plenty of time spent this spring wondering how teams will fill the many innings that need to be pitched in a 162-game MLB season.

For many years, the conventional wisdom in baseball has revolved around the idea of limiting innings as a means to prevent injury. Increases in workload from one year to the next were restrained by a percentage increase.

If that approach is carried into 2021, we will see a lot of pitchers, but none of whom would throw all that much. Lance Lynn led all of MLB with just 84 innings pitched in 2020. Even with the postseason included, no pitcher threw 100 innings last year. 

How, then, does one remedy the notion of moving from one pandemic-shortened 60-game season into a 162-game regular season without much concern for the increase in innings that pitchers will see across the board in 2021? The answer seems quite simple—with the advanced science, technology and biometric data specific to each player and his arm, and available to teams, the industry is beginning to shift to letting pitchers pitch while focusing more on monitoring than on fixed rules.

Conventional wisdom may lead many to believe that it would be too risky to allow pitchers to once again throw 200 or more innings in 2021, but a team with strict innings limits in 2021 will be constricting its pitchers in the name of caution, not in the name of medical science.

“It's all arbitrary. Like nobody, nobody knows." said Dr. Hillary Plummer, a biomechanist who is secretary general of the American Baseball Biomechanics Society. "If you go back when Stephen Strasburg was having inning limits, there's no data to support that. I mean, it's all arbitrary in baseball, and a lot of it seems to be like, well, that's just what we've always done. You see injury rates continue to increase. So maybe we need to look at doing something different."

In talking to a variety of experts in sports medicine, biomechanics and pitching development, Baseball America could not find anyone who has found any statistically significant health benefit in limiting the innings of pitchers based on the innings they threw in a previous year.

Baseball America first studied this in 2011, finding that among first-round high school pitchers, those who threw more innings in their first full professional season had more successful careers than those who saw their innings strictly restricted.

Much more robust academic research has followed.

A study by three researchers in 2015 looked at the workloads for the previous three seasons (minors and majors) for professional pitchers. The study found no correlation between the amount of innings pitched and/or the difference in innings pitched from one year to another and risk of injury.

In 2016, a group of doctors looked at the numbers of innings pitched by MLB pitchers in the year they returned from Tommy John surgery. Since all of the pitchers studied were recovering after elbow ligament replacement surgery, these were all pitchers who had thrown very few innings or no competitive innings over the previous season (Tommy John surgery requires a 12 to 15 month recovery period).

Among those pitchers, the study found no correlation between the number of innings pitched in their first season back and the risk of a further elbow injury. The pitchers put on strict innings limits were no less likely to re-injure their elbows. Those who threw more innings seemed at no larger risk.

“We found that there is no threshold. It isn’t 150-180 innings," said Dr. Anthony Romeo, one of the authors of the 2016 study. "There was an absence of evidence. The data we have today doesn’t set a clear line."

Now that doesn’t mean that every pitcher should go out and emulate Nolan Ryan’s 300-inning seasons from the 1970s. Pitcher overuse is a serious issue, but the best current science indicates that overuse and fatigue-based injuries have much more to do with how well a pitcher ramps up into the season’s workload then ensuring they don’t pitch while worn out.

From an injury standpoint, a study by Dr. Sameer Mehta found that pitchers were most likely to injure their elbows if they ramped up their pitching workload too fast.

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That’s why teams often see injuries during spring training and early in the season—ramping up after the offseason is a risk factor. But during the season, the most significant thing a team can do appears to be keeping a pitcher from pitching when fatigue has caused their mechanics to deteriorate.

So what should a team do? The best science we have right now indicates that pitchers need to be closely monitored throughout the season. A pitcher’s interactions with a trainer and/or coach should be used to provide a wealth of useful information. But there are also biomechanics indicators. Multiple studies have found that fatigued pitchers generally shorten their stride length in their delivery. They also often drop their elbow at their release point, get less shoulder rotation and lessen the bend of their trunk.

“There’s nothing replacing the human to human feedback,” America Sports Medicine Institute Research Director Dr. Glenn Fleisig said. “Certainly you can use in-game biomechanics to see about (a pitcher’s) trends and directions. It’s a wonderful complement to radar gun speed and pitch location.”

Other studies have shown that pitchers put more stress on their elbows when they throw while fatigued (with mechanical alterations) than they do when they are fresh.

Nowadays, some MLB teams are using markerless motion capture to study mechanics of pitchers in game. Such biomechanical analysis can provide early indicators of a fatigued pitcher who may need to be pulled from a game, skipped for a start or even sent to the injured list for rest and recovery. It also opens the door for much more individualized decision-making.

“That's one of the big variables that not only us but all teams have to work through. How do we navigate what was such an atypical year last year and how do we factor that in our planning for this year?” Indians general manager Chris Antonetti said. “The way we generally look at that time is we don't have hard and fast rules in place. What we try to do is think about each player as an individual, and what positions them to be healthy and successful.

“So, for instance, Triston Mackenzie's career path, and recent history is very different than Shane Bieber’s. So to set this similar workload restrictions for Shane as Triston probably doesn't make a lot of sense. So what we do is we look at each player individually and think about what makes sense for them, develop a plan, and then continue to monitor that plan. How are guys doing? How well are they recovering from starts? How well are they maintaining their stuff? Are they showing signs of fatigue with their deliveries or are there other markers? That will be one of our continued challenges. You can't really sit here today and say, ‘OK, this is the limit.’ This will kind of be just uncharted waters, where you're gauging it as the year goes on.”

Using biomechanical analysis could help teams comfortably allow pitchers to keep throwing throughout the season. If the pitcher says he feels good and he isn’t demonstrating the markers for fatigue, a team can feel reasonably comfortable that they aren’t risking the pitcher’s health.

When it comes to pitching injuries, there are no certainties, but nowadays teams have tools that they didn’t have a decade ago.

“The analytical people will help me in terms of that as the season progresses, if you see a regression of stuff, movement patterns, pitch shapes, things like that, that will dictate what kind of move that I'll go to (Astros manager) Dusty (Baker) or to the front office and say we might need to give someone so a rest,” Astros pitching coach Brent Strom said.

Teams are understandably going to be somewhat cautious in 2021. The fear of what teams don’t know after an unprecedented 2020 season will keep front office officials, trainers and coaches on edge this year. But a team that manages to properly monitor its pitchers throughout the upcoming season could find significant advantages by getting more work out of its best pitchers while also speeding the development of its minor leaguers.

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