Category: Nerd Stuff

Photo: Thomas Schönenborn|

How do you throw harder?

Spoiler: There are many, many things that contribute to this, and this article is only about a tiny fraction of them. 

Pitching delivery is very complex and has many individual biomechanical sections and parts. Because there are so many parts, it is not so easy to find out which biomechanical characteristics are actually responsible for speed, movement and control. 

In principle, forces and speeds correlate much more strongly with throwing speed than positions that can be easily recognized in photos, for example. Roughly speaking, this means that it is not whoever looks better in the photo, but whoever moves faster, throws harder. However, it can be assumed that better positions generally allow faster movements. So it's not all that different after all. 

What is scapretraction?

One of the few correlations between such a position and throwing speed is horizontal abduction. Other terms for this are "scapload" or "scap retraction".

It sounds very complicated at first, but it's relatively easy to explain: it's about how far the elbow is pulled behind the line of the shoulder. 

Particular attention is paid to the following characteristics: The maximum value, the value at footplant, and subsequently how long the horizontal abduction can be maintained. (It should be noted, however, that values determined using different measurement methods are not as comparable as values determined using the same method - ideally under the same conditions).

Driveline Baseball has found the average at Footcontact (FC, not the same as Footplant, but very similar) to be about 40 degrees, the maximum value is about 57 degrees(https://www.drivelinebaseball.com/2019/03/interpret-biomechanics-reports/).

For pitchers under 75mph, the average horizontal abduction at FC was 35.6 degrees, and for pitchers over 87mph it was 53.8 degrees.

The exact correlations are much more complicated (more details can be found here: https://www.drivelinebaseball.com/2019/02/biomechanics-rewind-look-numbers-last-six-months/), but it can be said very roughly - and really only very roughly - that pitchers who throw harder also have more horizontal abduction on average. Conversely, of course, this does not mean that everyone who reaches 53.8 degrees of scapretraction will automatically throw over 87mph, nor that everyone who has less than 35 degrees of scapretration cannot throw faster than 75mph... However, the probability that this is the case is high.

What are the benefits of Scapretraction?

The retracted elbow is what is most noticeable. Less visible, but much more important, is what happens to the shoulder blade. 

It is pulled backwards along the ribcage. This allows it to tilt backwards better, which supports maximum external rotation - the layback. It also facilitates the extension of the thoracic spine, which also simplifies the layback and subsequent acceleration. This is very important for healthy and efficient throwing.

The arm therefore has more time to spend in the layback position and a longer acceleration path. A longer acceleration path allows higher speeds with less acceleration, which reduces the peak load on the arm. You can therefore throw faster and with less strain. 

Why does a longer acceleration distance reduce the load peaks?

Let's think of acceleration in a car. But to make it clearer, let's take negative acceleration, i.e. braking. If I want to get from 100 to 0 and have 10 seconds to do so, that's no problem for the body. We have all done this many times. But if you want to do it in less than a second (by driving into a wall, for example), it leaves permanent marks on the body. 

Of course, fewer forces act during the throw, and the acceleration distance is not increased 10-fold. The effects are much less drastic, but the principle is the same. 

How do I improve Scapretraction?

First of all, the necessary flexibility and mobility must be present. The large and small pectoral muscles, as well as the saw muscle, must therefore be long enough and be able to release precisely (trigger points, stretching exercises for the chest)

At the same time, the rhomboids and trapezius muscles must be sufficiently trained to be able to pull the shoulder blade towards the spine (rowing exercises, "band-pullaparts"). 

Plyoball pivot pickoffs, plyoball scapretraction throws and roll-in throws are particularly suitable for improving movement coordination in the throwing motion. 

However, avoid paying particular attention to it during the throw - this is almost impossible and can negatively affect the timing of your throw. Instead, try to prepare your body for this movement so that it allows and uses it during the throw.

Most arm injuries occur at the start of the season(https://mikereinold.com/mlb-tommy-john-injuries/). It is reasonable to assume that the strain during this time is often too high for the players' fitness level. For this reason, it is very important not to throw too much too quickly. If you do, it very often leads to arm pain. 

But what is the best way to build up the arm? How much should you throw, how often and how quickly should you increase? To answer this, we need to expand a little. 

To know how much strain you can put on an athlete without risking injury, I need to know how much strain they are used to. This is called the chronic load. It indicates how much stress the athlete has been exposed to on average (simplified) in the last four weeks. For a runner, for example, this would be kilometers. They should therefore be able to easily cope with this load today (the acute load), plus a little more. The acute load is the load of the last 7 days. The interesting question is: how much is "a little more"?

If you divide the acute workload by the chronic workload, you get a ratio. This is known as the acute to chronic workload ratio (ACWR).

Across all sports, it has been found that the increase in load can be controlled very well via the ratio of chronic to acute load (A/C ration). This makes it relatively easy to subsequently observe how the injury frequency changes with the ACWR.

In order to do the same for throwers, it is best to know the load of a throw. If you know this, you can simply multiply it by the number of throws and you will get your daily load. The problem, however, is that not every throw causes the same amount of strain. 

By measuring a large number of throws, from a large number of players, at different distances(Modeling Elbow Valgus Torque From Throwing Distance With 627,925 Baseball Throws by Competition Level, 2019, Ben Hanson), you can roughly assign load zones to distances. If you control the number of throws per distance/loading zone, you can also control the total load of the throwing day. 

That's exactly what I did. To keep the ratio of the acute load to the chronic load (the A/C ratio) around or below 1.5 over the 6-8 week on-ramp phase (see next page), I adjusted the load for each day and calculated the ACWR. This is how I arrived at the number of throws and distances for each day.

After the onramp phase, the arm is fit enough to have sufficient scope to work on the mound at higher intensities and to continue building up the chronic load. 

The graph shows a few important values. The green line is ACWR. If possible, it should lie between the two red lines.

In the first few days, the ACWR is significantly higher than the target - there are mathematical reasons for this. Since the chronic load is zero at the beginning (or very low even after a few adjustments and weighting), the ratio must be correspondingly high. In reality, however, the arm/body of a healthy athlete is never completely unfit for exercise. For this reason, the starting point is also the most "arbitrary" in this calculation. Even after that, the ACWR keeps jumping over the red line. I consider this to be justifiable for the following reasons:

1. If you don't allow this, you have to increase the program over many more weeks. A 12-week onramp program before pitchers go to the mound is not realistic and is more appropriate after injuries. You may lose more pitchers to boredom than to injury 😉
2. The shorter the break from throwing, the fitter the arm is. Even after one (or more) month(s) break(s) from throwing, the arm load capacity does not drop completely to the level of untrained people. However, since the chronic load is measured over 4 weeks, this would be the assumption in the model and therefore never works optimally in the first few days.
3. The lower the absolute daily load for these overloads, the less drastic the effects of the overload. In the beginning, a handful of litters to 120 can mean a calculated overload. I think we can agree that "one more litter" is unlikely to be the cause of overload dislocation. In this model, a few extra throws at the beginning of the program can give exactly this impression. But I think that's an exaggeration.
4. Exceeding the ACWR does not mean an immediate injury - merely an increase in risk. As already indicated, the amount and duration of the overrun must also be taken into account.
5. The goal is to minimize the risk of injury at an acceptable cost, not eliminate it at all costs. An overly cautious approach might still be a little "safer," but it costs more in performance gains and, most importantly, is extremely monotonous. What pitcher wants to throw slowly with hardly any progress for many many weeks?

The blue bars represent the daily load. These will be considerably higher later during matches than during this onramp phase. The orange line represents the chronic load - this will also continue to increase after the onramp phase.

The higher the chronic load, the higher the fitness level. A higher fitness level enables more pitches per day and week without risking overload. This in turn enables more, and above all better quality, training on the mound and more or longer matches.  

The model has some limitations that could be reduced, for example, by continuous individual measurements of each pitch (for example with a PULSE sensor) or at least by creating further and more accurate approximations. However, as a basic framework for an on-ramp phase for healthy pitchers, it seems to be a sensible first step.

You can find detailed instructions for implementation here and here.