# The kinetic chain and efficient mechanics

This week, I wanted to talk more generally about pitching mechanics, and specifically the fundamental concept of the kinetic chain. Apologies if this post is a little bit late, as winter term finals are getting going here at Caltech, and so I haven’t been able to finish writing this post until now! Anyways, lets get to it.

No two pitchers are going to have exactly the same set of mechanics for a variety of reasons…even if two pitchers have exactly the same body (i.e., the same height, weight, body composition, limb lengths, etc.), there are still essentially an infinite number of variables that determine your mechanics. For simplicity, we break up certain movement patterns into groups, like “arm action” or “hip-shoulder separation,” but in reality these movements are extremely complex, and creating these groups is just our attempt to simplify this infinite degree of freedom problem into something bearable! With all of this being said, at the core of an efficient set of throwing mechanics is an efficient kinetic chain, and getting the kinetic chain sequenced properly can really set you up to optimize (or come close to optimizing) this infinite-dimensional mechanical problem.

What is the kinetic chain?

As Paul Nyman describes in this article, which I originally found through this Tread Athletics video, the kinetic chain in its simplest form refers to the transfer of energy through different segments of your delivery, with energy being transferred from the larger muscles of your legs and lower body, through your torso and shoulders and ultimately to the baseball at release. In an ideal kinetic chain, the transfer of energy from one segment to the next is a smooth one, and there is relatively little “wasted” energy (i.e., energy that doesn’t end up being transferred to the baseball at release) as a by-product. In creating this optimal kinetic chain, it is the timing of these movements that is critical. Obviously, if your body is weak and you aren’t able to produce a lot of force to begin with, chances are you’re not going to throw very hard, even if your kinetic chain is sequenced optimally. However, you can look like the rock and still throw 75 if your sequencing isn’t good.

As Nyman talks about in his article, the optimal sequencing pattern is one in which, just as one section of the chain is reaching maximum velocity (i.e., once it is done accelerating), the next section of the chain is beginning to accelerate. This is known as the “summation of speed principle,” and in an ideal system the speed of the final section of the chain would be equal to the sum of the maximum speeds of all the other segments. While this is an idealization, it is certainly true that sequencing the different segments of the kinetic chain (for example, your trunk, shoulder, forearm, and hand, as in the image above) in this manner will result in a velocity that is close to optimal.

Where does the kinetic chain show up in your delivery?

An example of a kinetic chain link or segment is the relationship between the hips and the shoulders, and the concept of “hip-shoulder separation.” I have some firsthand experience with this concept, and it’s been somewhat of a recurring “bug” in my mechanics over the past offseason and even more recently than that. When I first got to Driveline last June (June 2018), my initial motion capture showed that my “raw” hip-shoulder separation (i.e., the maximum angle I created between the line of my hips and the line of my shoulders) was pretty good, but the timing difference between the two segments (i.e., the difference between the time in which my hips hit maximum velocity and the time my shoulders hit maximum velocity) was almost 0 (.0083 s). Coming off an injury during the 2018 season, I wasn’t throwing very hard in this assessment compared to usual (I couldn’t break 86) and this “break” in the kinetic chain due to my hip-shoulder separation timing was a major culprit. Driveline’s director of player development Sam Briend wrote a blog post on their website about something similar (check out the “What does it look like?” section).

After about a month of really focusing on this concept during daily throwing, I was able to get my separation timing up to around .05 s in my exit assessment in July, which is more or less where it should be. As a result, my velocity began to climb, and although I wasn’t touching 90+ like I had during the 2018 season, over the remainder of the summer I got back up to around that range. It’s also important to note the timescale of .01 seconds that this hip-shoulder separation occurs on, and that it’s extremely difficult to see this even on slow motion video. While it is certainly possible to diagnose and correct a lot of mechanical bugs, getting objective motion capture data can be a game changer if it’s available to you.

There are obviously a lot of other places that the kinetic chain manifests itself throughout the delivery, and we can look at the “links” between different segments to see this. For example, the elbow spiral encompasses movements of the shoulder, elbow, and hand, all of which are important links in the kinetic chain. The body is a complex system, but simplifying it using the kinetic chain can aid significantly in optimizing your mechanics.

How do you train the kinetic chain?

So we know that we want all of these different segments of the kinetic chain to move sequentially, according to the summation of speed principle, but how do we train our body to do this? For those of you that are familiar, I’m a big fan of Driveline’s plyocare drills, which allow you to isolate certain components of the kinetic chain separately, and then eventually blend them together into your overall delivery. For example, in pivot picks, you can isolate the arm action and the later-occuring sections of the chain, whereas in roll-ins you can really work on the hip-shoulder link of the kinetic chain (among other things). Of course, any drill can be modified to work on a specific focus, but the general theory of the kinetic chain holds across this group of plyo drills. For a more detailed look at these drills (and at the kinetic chain in general), check out Driveline’s training manual, suitably named Hacking the Kinetic Chain.

There are, of course, other ways of training the kinetic chain as well. For smaller breaks or bugs in the kinetic chain, often times your body can self-organize and fix the issues automatically through high intensity throwing. In other words, if you have a small timing issue somewhere in your mechanics, by attempting to throw the ball at higher and higher intensities, your body can sometimes “figure out” a way to fix minor issues. However, for larger issues, this can sometimes do more harm than good! Determining the best way to address mechanical inefficiencies is a difficult skill to acquire (and one that I struggle with), and having a good trainer to work with can be very helpful in figuring things like this out.

As somebody who’s had his fair share of issues sequencing wise, the fundamentals of the kinetic chain are often a good place to start when trying to make mechanical adjustments. The last week or two at practice, I had really been focusing on working hip/shoulder separation through the roll-in drill. I ended up seeing some fairly significant improvements in this area, although I also noticed on video from my most recent bullpen that my shoulder abduction was a bit low. This shoulder abduction is related to how energy is transferred through the upper part of the kinetic chain, and will definitely be a focus moving forward in plyo drills. You can see what I mean in this video from Tuesday:

This mechanical issue was backed up by Motus sleeve data, which had my peak valgus torque (aka arm stress) in the 70+ Nm range (for comparison, when I used the Motus sleeve over the summer, my stresses were in the 50’s…I had a Motus sleeve before that broke, and I bought a new one last week as they just came off back order). Especially given that I was throwing this pen at about 80-90%, this is a bit high, although I didn’t really feel very much at all in my elbow during this pen. Either way, I’ll definitely be monitoring my shoulder abduction moving forward during plyo drills.

I didn’t have any stats from the past weekend, as we only had a single game that I didn’t get into (although I did get hot in the pen in the 8th inning), although I do have stats from our game yesterday:

3/15/19 vs. Ithaca College: .2 IP, 1 H 3 R, 3 ER, 4 BB, 2 K, 0 HR, 1 HBP

Obviously, this wasn’t a good outing, and moving forward I’ve got to really trust my stuff a more than I did yesterday. A lot of times I’ll get into the trap of trying to take something off and “aim” the ball when I throw 2 or 3 balls in a row, and this really just sets me up for failure. Going out into a game and trying to PR every pitch is probably not the best strategy, but at the same time neither is not throwing hard and aiming the ball because I’m afraid of walking or hitting guys. In the future, I’m just going to trust that I can still throw strikes at 87-88+ and work with that.

Even though the results weren’t there, my elbow at least felt fine, and even today it wasn’t really in much discomfort or pain at all during catch play. Also, stuff wise I was still dominated pretty much every at bat and generated a ton of swings and misses on my four and two seam fastballs, which is always a good sign. Once I get my command dialed in and really start trusting my stuff, I should produce some better results.

Image credits: https://www.quora.com/What-does-kinetic-chain-mean

https://theperformancelabinc.wordpress.com/2014/09/16/the-kinematic-sequence/