A few days ago I posted a preliminary look at Cardinals top prospect Shelby Miller’s mechanics. In it, I offered a different perspective on some of the ideas presented by Kiley McDaniel in a recent write up on Miller over at ESPN. With a few of those ideas in mind, I hope to accomplish two objectives in this post: (A) investigate Miller’s lower body mechanics as they pertain to his velocity and (B) evaluate a few parameters with relation to injury risk.

(A) Miller’s Lower Body Mechanics

I’ll evaluate Miller’s lower body mechanics on two dimensions:

  1. How much momentum Miller generates with his lower body and how efficiently he generates it.
  2. How efficiently he translates that momentum up the kinetic chain.
Shelby Miller at "Stride Foot Contact"

1. The magnitude of momentum generated.

Miller seems to do a pretty good job creating energy with his lower body. One of the more controversial topics when it comes to pitching mechanics is the idea of a balance point. The traditional balance point is achieved when a pitcher has yet to begin moving forward until his lead leg has begun to drop back down from it is maximum height. The term that has been given to pitchers who begin to move forward as they raise their lead leg is “dynamic balance.” Miller falls into this second category. As you can see here at the 3:00 mark, his leg kick brings his center of mass forward. One reason this sort of move may be beneficial is that it may reduce the initial moment of inertia that the pitcher must overcome to get his body moving towards home.

Miller’s next move is to “sit into” his delivery. An effective way for pitchers to generate momentum towards home is for them to use enlist the help of gravity. A pitcher can use gravity to help him accelerate his body towards home, making a pitchers stride as much of a “controlled fall” as it is a “push off” from the rubber. This use of gravity is reflected by that “sitting motion” with a pitchers hips and butt, and increased flexion in a pitcher’s back knee is often the result. This is not to say that “pushing off” the rubber can’t increase the momentum a pitcher generates towards home. As long as the force is being applied in the x-dimension (a line perpendicular to the rubber and through home plate) and not in the z-dimension (directly into the ground) then a pitcher can generate momentum towards home with added force applied to the ground by his lower body.  Miller seems to generate a pretty good amount of momentum and does so fairly efficiently, taking advantage of gravity while not putting excessive force vertically into the ground.

I also like two other things that Miller does with his lower body. Miller takes a good stride towards the plate that is slightly closed (see previous article for more on the stride direction). Increased stride length has been shown to increase velocity without impacting command. While Miller’s stride looks to be far from a Lincecum-esque 120% of his body height, he does take an aggressive stride towards the plate and that stride length gives him a longer distance over which he can accelerate his body towards home. This next point is as much about his delivery as a whole as it is about his lower body, but is worth mentioning here. Miller has a fast tempo to his delivery. He gets from his maximum knee height to ball release in around 20-21 frames (as measured on a 30 Hz camera). This quick tempo is helped by that dynamic balance and effective use of gravity to accelerate home (and hence why it is mentioned here). Pitcher’s with big velocity tend to have a more aggressive tempo than do soft-tossers.


2.  Efficiency with which Miller translates this momentum up the kinetic chain.

When discussing how efficiently a pitcher utilizes the momentum he created with the early movements of his lower body, we are primarily evaluating the movements of his lead knee. It is in fact the breaking force applied by the lead leg that is translated up the kinetic chain, not the momentum generated towards home. A pitcher who is strong with his lead knee or extends it after stride foot contact (SFC) will generate a greater breaking force with his lead leg. Conversely, a pitcher who flexes more on his lead knee will generate less breaking force. This explains why a parameter correlated with velocity across multiple studies is “lead knee extension angular velocity.” As the name implies, the faster a pitcher extends his lead knee after SFC and as he approaches ball release the higher we would expect the resulting ball velocity to be. Now, landing on a stiff front leg is thought to cause command issues, so all this assumes that the pitcher lands on a flexed knee and extends it from there. Miller lands well, but flexes on his knee a surprising amount thereafter. This creates a less efficient momentum transfer from his lower body up the kinetic chain (which ends with the ball). If Miller was stronger with his lower body block after stride foot contact then we may see a few more 97’s and maybe even a few 8’s and 9’s. Here is an example of a guy who does this really well (you may have heard of him).


(B) Injury Risk

This is one of the most important aspects when evaluating a pitcher and trying to create an expectation about his long-term performance. I think that Miller looks fairly good from an injury risk standpoint. I have neither the ability nor the capacity to evaluate at least some of the parameters that are related to injury risk for a pitcher, but there are a few things worth mentioning, even though this evaluation will be far from complete. I tried my best to avoid the overly technical jargon, which hopefully makes this a little more readable than it otherwise would have been.

Miller may have a few very minor red flags, but I see no big reasons for concern moving forward. First, Miller may get his elbow up a little high in back. Additionally, he may leave his forearm in an overly horizontal position (think, parallel to the ground) as his stride foot hits the ground. You can see both these parameters in the photograph above. He doesn’t appear to be grossly out of bounds on either of these issues, and I don’t think either will be a problem long term. The main reason for my lack of concern is that both those parameters (back elbow height and forearm position) can create a timing flaw with the pitchers arm, which stresses both the pitcher’s elbow and anterior (front of the) shoulder. Miller’s timing looks quite clean, however, which gives me reason to believe that the minor risk those two issues pose is negated somewhat. Now, that doesn’t mean that they become non-issues, but I don’t see a Strasburg-ian injury risk here.

**Quick disclaimer**: Given the poor video quality that I have access to, all these evaluations (especially the ones on injury risk) are subject to a good deal of uncertainty. In addition to being conducted by someone much smarter than myself, an ideal biomechanical breakdown would utilize a 3-dimensional camera set up that capture video at a rate of at least 200 frames a second. I am working with 2-dimensional youtube videos at 30 frames a second.

Summing up:

Miller does some things quite well in his delivery that contribute to his above average velocity. A Cardinals fan could even be optimistic about seeing an extra tick or two on Miller’s fastball if he improves with his lead knee. I think that the best news for Cardinals fans is that I don’t see too much in Miller’s delivery that would put him at risk for injury beyond what is simply normal for someone who specializes in the action that produces some of the highest angular velocities in all of sports. That is not to say that Miller won’t get hurt. However, from what I can see, Miller ought to be considered a safer asset than most pitchers.