Monday, May 14, 2012
Chris Sale and his faulty elbowPosted by Kyle Boddy
Chris Sale has been the subject of much discussion in 2012, as he's been jerked around from the starting role to the bullpen with reports of inconsistent velocity. To compound all of this, he's had an MRI on his elbow due to tightness, though it's been reported that it's due to normal soreness and not major injury.
Keith Law is not impressed with Sale's mechanics or the idea of him in the starting rotation:
I've asked Keith on Twitter (@keithlaw if you decide to do the same) why he thinks Sale's arm action has a higher propensity for elbow injury, but he hasn't commented on the specifics of his claims.
Sale's Mechanics: Then and now
Here are two clips of Chris Sale pitching against Oakland, both in the Coliseum. These are two different years. One clip has Sale throwing a 95 mph fastball, the other a 93 mph fastball. Both came in the eighth inning. Can you tell me which one came from 2012 and which one came from 2011?
If I hadn't cut the video, I bet I wouldn't have been able to do better than simply flipping a coin and guessing, though I might choose the clip where Sale is throwing 95 mph over the one where he came in as a reliever in 2011.
I'd be wrong. Sale was throwing 95 mph in Oakland in the eighth inning as a starter on April 25.
My point is that Sale's mechanics between 2011 and 2012 have not meaningfully changed. (If you slow the clip you can see some minor differences with the glove leg and trunk flexion, though.)
But why does Law think that Sale is an injury risk? I won't speculate on his reasons; rather, I'll discuss some scientific research that might shed a light on Sale's pitching mechanics.
Sidearmers, valgus stress, and you
Generally speaking, Sale has a fairly internally rotated humerus at stride foot contact (SFC) and, combined with his high rates of pelvic and shoulder rotation, he lays his forearm back into external rotation during arm cocking quite fast. This certainly will increase the eccentric load on the shoulder, though whether or not this is specifically injurious is debatable.
However, Sale is also a sidearmer, and research does indicate that sidearm pitchers are generally at higher risk for increased elbow valgus torque. (Source: Aguinaldo et al; ignore the "conclusion" contradiction, Aguinaldo has said it's a typo/mistake in the abstract that isn't there in the full paper. Read it here if you like). Increased elbow valgus stress is highly correlated with UCL tears/sprains, especially when combined with a more-extended elbow at ball release (which Sale does have).
The theory that sidearm pitchers are at higher risk for elbow injuries seems to hold water based on previously conducted research out there, though it's worth noting most sidearm pitchers have lower ball velocity than high three-quarters and overhand pitchers (for whatever reason). Ball velocity is obviously very highly correlated with valgus stress, so the net effect may be lowered amongst all sidearmers. Of course, Sale throws very hard, so that's not applicable to him.
Whether or not Law looked at Sale's mechanics through this type of research lens is unknown, but he's probably onto something. It should be interesting to watch Sale's velocity over the rest of the year, and beyond.
Kyle Boddy is the owner of Driveline Baseball and Driveline Biomechanics Research, both in Seattle, Washington. At his facility, he's melded statistical analysis, strength & conditioning, prehab/rehab, and advanced biomechanical analysis concepts to develop improved efficiency, durability, and fastball velocity of baseball pitchers. He can be reached via email at email@example.com and found on Twitter: @drivelinebases.