We've all heard it: Tommy John surgery makes you throw harder. Is it the fresh new ligament (well not new), but you know what I mean, all that time off, or some mental factor that makes pitchers throw faster than ever after leaving the operating table? "It felt so good when I came back, I said [sic] I recommend it to everybody...regardless what your ligament looks like," Billy Koch said in a 2003 USA Today article. "I hit my top speed (in pitch velocity) after the surgery," said Kerry Wood in the same article. "I'm throwing harder, consistently."
But is it the Tommy John surgery itself that really makes pitchers throw faster? In the same article, experts hypothesize that the extra velocity comes not only from the new tendons-which become ligaments themselves, replacing the old ones-but also because "[the rehab] exercises to build the shoulder and forearm make the entire arm stronger. And sometimes, the patient simply matures physically."
But this is just anecdotal evidence. Do pitchers actually gain any velocity at all from the process? As Cliff Corcoran of Sports Illustrated notes, "It's a bit of an urban legend that ligament-replacement surgery can add velocity to a pitcher's fastball."
I decided to go to the data and investigate the claim that Tommy John helps pitchers throw harder. Long story short: I'm beginning to think I agree with Cliff.
To do this project I used two wonderful resources: One is the invaluable, exhaustively detailed (and freely available) Injury Database; the other is the PITCHf/x tool (data from which is available freely from numerous sources including FanGraphs), and Texas Leaguers. The Injury Database includes records of every player who has received Tommy John surgery from 2002-2009 and the PITCHf/x data (taken from FanGraphs) has average fastball velocities for Major League pitchers for every season since 2007.
To build my data set, I first whittled down my list to pitchers who had Tommy John surgery in either 2008 or 2009 (I didn't think there was enough data to include the pitchers receiving the surgery in 2007), and from there I whittled further until I only had pitchers for whom there were average fastball velocity data for seasons before and after their surgery. I then calculated the average "before Tommy John" velocities and "after Tommy John" velocities. Finally, I calculated the differences between these velocities and performed a one-sample t-test (from AP Stat, remember?) My data and the t-test is available by clicking here.
I will not go into too many details concerning the t-test, but I will tell you that the results indicated that we could not detect a significant change in a pitcher's fastball velocity after he undergoes Tommy John surgery at the 95% confidence level. The relevant 95% confidence interval was from -0.45 MPH to 0.94 MPH (each number representing a change in the pitcher's fastball velocity in MPH post-surgery), which includes 0 MPH, that is, no change in velocity. This means, assuming he returns successfully (success rates after Tommy John are "close to 85 to 92 percent in elite pitchers," from the SI article), we shouldn't count on an increase in velocity from our friend Stephen Strasburg.
Caution should be exercised, of course, in taking these conclusions too seriously: My data set was fairly small (19 observations), as was the number of seasons used for calculating the before and after velocities. Further, I did not attempt to control for potential confounding factors (changes in mechanics, age, and so on). Also, the sampled distribution is not exactly normal (though the sample size seems large enough to not have to worry about the normality assumption, which applies to the population). These are the main shortcomings that spring to mind.
There are, however, some other interesting tidbits to be gleaned from the data. Of the 19 pitchers in the study, only six experienced an increase in velocity after Tommy John, with Jake Westbrook (2.6 MPH) and Carl Pavano (2.25 MPH) seeing the greatest increases (Billy Wagner, often cited as proof of the faster-after-Tommy-John argument, only experienced a 0.77 MPH increase). Of these pitchers there was a median gain of 1.24 MPH on their fastball. The rest of the pitchers suffered a loss of velocity, with a median decrease of 0.45 MPH (B.J. Ryan suffered the most-a 2.6 MPH loss).
What I find most interesting, however, especially since we are thinking about Stephen Strasburg here, is that the pitchers who received Tommy John are not necessarily hard throwers-in fact, fewer than half throw harder than 93 MPH on average, and the same holds true even when looking at the whole list (all those pitchers receiving Tommy John surgery between 2002 and 2009). Now, this doesn't include other serious arm injuries, mind you, but it does mean that if you got Tommy John then you weren't necessarily throwing too hard. Maybe it was your body type? Your mechanics? Your age? Your pitch selection? Or your workload when you were young (which, in fairness, Kevin Blackistone mentions in the article linked above). So many questions and none of them will be addressed here; these are all studies for another day. Even if he isn't throwing harder, will Stephen Strasburg get hurt again? We'll have to keep waiting for the answer to that one.