Sonne-ding off on a problem like Aaron Sanchez

Aaron Sanchez on the mound at Rogers Centre July 4, 2016 against Kansas City

Aaron Sanchez on the mound at Rogers Centre July 4, 2016 against Kansas City


It has sparked a fascinating debate in baseball circles. But in the end the Blue Jays appear to have made the right call keeping Cy Young Award contender Aaron Sanchez in the starting rotation, a leading biomechanics and muscle fatigue researcher has concluded.


Mike Sonne is an ergonomist and alumnus of McMaster University in Hamilton. His work studying the effects of muscle fatigue on Major League Baseball pitchers is getting more and more notice from those around the game.   Sonne and Jim Potvin (a Professor Emeritus at McMaster and long-time personal acquaintance of mine, full disclosure!) published a paper on the “complicated” relationships between muscle fatigue, recovery time and injury in 2013.  They studied the recovery time needed for muscles to recuperate 100 per cent of their force-generating capacity to optimize muscle usage and performance.

“In my evidence-based opinion, I would say this is the best thing for Aaron Sanchez,” Sonne said of the Blue Jays’ sudden reversal this week to keep him in a six-man rotation instead of moving him to the bullpen. Offseason work to build  a reported 25 pounds of muscle is paying off for Sanchez and the Blue Jays, Sonne believes.

“Really focusing on his conditioning, building up his strength to be able to push himself through this season, I think that’s going a long way for him,” he said. “ You rely on the muscles that span your elbow to essentially contract and make sure that joint stays together.”

While Sonne notes there are differing schools of thought on the relationship between arm muscle strength and injury risk, the notion that moving Sanchez to the bullpen would protect him doesn’t pass muster.

“If you’re truly trying to protect that (UC) ligament, and avoid things like Tommy John surgery, moving him into the bullpen may not necessarily be the right thing to do,” said Sonne, who points to the direct relationship between pitch velocity and arm stress. Sanchez has averaged 95 miles per hour with his fastball this year, while he clocked an average of 97 last year out of the bullpen, and he’s among MLB leaders in pitch economy per inning.

“Above all else, throwing fewer pitches per inning is the number one way for a pitcher to minimize their fatigue levels,” said Sonne, who views innings limits as an increasingly “antiquated measure” to reduce injury potential among pitchers. Recovery time is the lynchpin of Sonne and Potvin’s research, and Sonne believes the Blue Jays move to a six man rotation will not only help Sanchez, but Marco Estrada, who’s been dealing with lingering back pain this season.

“(Sanchez) trained for this, and it appears his training is paying off.”

Indeed, more and more research is finding biomechanical links to injury potential in professional athletes, and teams like the Blue Jays have access to this kind of data. Sonne noted a device called a Motus sleeve is now helping to measure stress on the arm, and a study released in June from Cornell University has linked heart rate variability to injury potential.

“What they’re saying is if you have less variability, your body is less able to adapt to these situations and you’re going to be more likely to sustain an injury,” said Sonne, who noted heart rate variability is one thing measured by the Catapult device used in Marcus Stroman’s injury rehabilition last year.

The Sanchez situation obviously draws comparisons to Stephen Strasburg, who was 22 years old when he tore his UCL in 2010, and was shut down early by the Nationals in 2012; Sanchez is 24. While age in and of itself isn’t likely to be a direct risk factor, younger hurlers could be susceptible to an indirect one.

“They haven’t had enough time to be exposed to advanced weight training programs to really strengthen themselves, they’re still putting on muscle, they’re still working on getting stronger and improving their fitness, so that might be something to consider,” Sonne said.

Sonne decided to use the muscle fatigue model he and Potvin created to also look at the potential impact of implementing pitch clocks in Major League Baseball could have on injuries to pitchers.   He found muscle fatigue, constantly linked to injury risk,  could increase 7% with a pitch clock.

Purposely implementing something where they have to pitch faster and recover less, it really doesn’t make sense,” he said. In fact, Sonne contends pitch clocks could have the opposite impact of their intended purpose to shorten games if fatigue means pitchers throw more balls out of the strike zone.

“So you end up having a couple more walks a game, and now you have got somebody on base, and when somebody’s on base, the pace slows down too,” he theorizes.

“It doesn’t necessarily speed up the game I don’t think…it’s kind of a short-sighted approach.”

It would not be surprising if the Major League Baseball Players Association uses Sonne’s findings to argue against the addition of pitch clocks in the upcoming round of collective bargaining with MLB owners.

If you want to ask Sonne more about his work, he plans to attend the upcoming Pitch Talks event in Toronto September 8 (

As for Sanchez, he appeared to be on his way to another stellar start until giving up four runs in the 5th and 6thinnings Saturday in a 4-2 loss in Kansas City, tossing only 58 strikes out of 92 pitches thrown. The loss ended his 10-game winning streak.


More from Mike Sonne

Sonne/Potvin research

Cornell research: pubmed/27379956

Pitch clocks article

Catapult device reference