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The Physics of Tommy John



I thought I would do a quick post about some very interesting information I read about pitching and how it ties in with bio-physics.  As a lot of people know, Tommy John surgery is a dreaded operation that is used on mostly baseball players to correct the mother of all baseball injuries: a UCL tear.  The UCL, or Ulnar Collateral Ligament is a small ligament on the "pinky side" of your elbow.  Its main purpose is mainly to hold back all the torque generated by your arm when it goes into a whipping overhand motion.  Basically, its a convenient little piece of tissue tailor made for all of us throwing sport athletes.  The weird (and kind of scary) part is, for how much throwing revolves around this ligament, us humans punish it all the time.  In fact, multiple studies conducted among college and pro baseball pitchers have repeatedly shown that the UCL sustains anywhere from 65-70 Nm of torque on any given pitch.  And the point of complete failure for a UCL in a lab?  A mere 35 Nm of torque... In other words, every throw, athletes can be putting up to DOUBLE the amount of stress on their UCL than what it takes to completely snap it.  

Although this is a scary thought, one may wonder, "this must all not be true because I've never had an UCL injury before".  And although that statement is true, it raises another very valid point: mechanics.  The only reason the MLB does not see an average of 1 UCL failure per pitch is because of attenuation.  Basically the whole reason you twist your core, drive with your legs and tuck your opposite arm when you throw is to attenuate the torque on your elbow.  To put it simply, all of your body parts "help out" your elbow and contribute in their own way to driving the ball forward, meaning the velocity of the ball does not depend solely on your elbow and therefore all that 70 Nm of torque will not be put directly on your UCL.

So remember kids: attenuation is what is saving you from a career ending injury... so practice those mechanics!!  


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