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Problems with the NPA's Sequence
of Critical Events


There would be no point in my doing what I am doing if Tom House and the National Pitching Association (NPA) got everything right.

The problem is that they don't.

The diagram below, which is from this page on the NPA web site and which purports to show what happens when during a throw, is a perfect example of this.

The NPA BioMechanical Efficiency Model

The NPA BioMechanical Efficiency Model

If you compare this timeline to video of the best pitchers in the world, or really just any higher-level pitcher, it is quite obvious that there are a couple of significant problems, or at least departures from reality, with it.

First and foremost, Event 7, in which the forearm lays back into external rotation, is placed much too late in the process. In truth, in most cases the forearm starts to lay back into external rotation at, or soon after, Event 4 when the Glove Side (GS) foot strikes. Even if the implication is that the marker for Event 7 represents the moment when the external rotation is completed, this is still wrong. In most cases the external rotation of the Pitching Arm Side (PAS) upper arm is completed before or as the shoulders square up to the target.

Roger Clemens

Roger Clemens

Second, it's physically impossible, in a high-level throw at least, for the shoulders to rotate 90 degrees and to square up to the target without any external rotation occurring. The rapid rotation of the shoulders causes the PAS upper arm to externally rotate and the PAS forearm to lay back.

This isn't just an academic, technical point.

This model represents the NPAs understanding of what happens when during a throw. As their web site makes clear, they are instructing and evaluating pitchers according to this model. Unfortunately, this model is flawed. As a result any advice based upon it is at least highly suspect if not actually dangerous due to the chance that it will encourage the creation of timing problems in pitchers.

If you are interested in understanding what actually happens when during a high-level throw, then I suggest that you read my piece that lays out a Revised Baseball Pitching Cycle.


I have already had people write me and tell me that I'm misinterpreting the NPA's diagram. They say I should pay more attention to the time stamps than the position of the arrows on the diagram.

My response is that doing that won't solve the problems with the diagram.

First, the meaning of the timestamps aren't at all clear. I believe that the timestamps represent the range during which that even either starts or finishes rather than the elapsed time it takes for the movement to occur. For example, that means that Event 6, where the shoulders square up to the target, generally happens between 1.23 and 1.33 seconds after the first forward movement.

Second, the scale (timeline) of the diagram is arbitrarily stretched and compressed at different points. For example, compare Event 6 which occurs at 1:23-1:33 and Event 9 which occurs at 1:24-1:34. In that case 1/100 of a second is represented by 1.25 inches. However, elsewhere on the chart the same horizontal distance, from Event 2 to Event 4, represents a full second. You can also see this by comparing the distance from Event 2 to Event 4, which represents 1 second, and the distance from Event 4 to Event 11, which also represents 1 second. You can see that those are two very different horizontal distances.

You can't stretch the X axis like that and not expect to confuse people.

Third, regardless of the issues with the timestamps and the scale, the fact is that Event 7 is out of sequence. In the case of most good, durable pitchers, the forearm lays back into external rotation at foot strike (Event 4) and finishes laying back into external rotation by the time the shoulders square up to the target (Event 6). At or shortly after Event 6 the Pitching Arm Side upper arm actually goes into internal rotation.

I'm not sure if the issue is that the diagram is wrong or just really poorly designed, perhaps out of a design to make things fit into a model of a linear series of discrete events. Regardless, people who try to teach according to it are going to be very confused and will likely draw some very wrong conclusions.

I'm trying to come up with a diagram that more accurately reflects what happens during a throw (and that uses the NPAs time stamps as a starting point). One of the ways I'm going to do that is by...

  1. Allowing for more than one thing to happen at a moment in time.
  2. Illustrating things as long-duration events rather than discrete moments in time.
  3. Maintaining a consistent timeline.
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