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    by Mark Rippetoe

Entries in shoulder (4)


"Delayed Internal Rotation" revisited and elbow roll-in

Almost 4 years ago, I wrote an article that was sort of a spit-balled take on an arm action sequencing concept. Practically immediately, it was torn apart by Dr. Mike Marshall. I realized then that the article was poorly written. Part of that was the spit-ball nature of it, its kind of "thinking out loud" approach, but a big part was my wonderfully awful descriptions of and references to the kinetic chain.

Shortly thereafter, I threw a disclaimer at the top and promised to re-write the article. Well, there really isn't much point because, even cleaned up, I don't think the concept holds water.

Today, at Ron Wolforth's Pitching Central Ultimate Pitching Coaches Boot Camp (I typed out the whole thing for comedic effect. Did it work?), that exact article was mentioned in reference to an analysis of different types of layback, what causes layback, and how someone can have late forearm turnover and avoid the dreaded reverse forearm bounce.

It's an action that I've addressed before in my pitcher analyses. In my analyses (both professionally and on this site), I've drawn attention to when a pitcher decreases reverse forearm bounce by "picking up" his elbow. You can see this very well in my 2009 analysis of Brandon McCarthy. Back then, I described it like this:

It's hard to tell from this angle, but McCarthy's reverse forearm bounce might be exaggerated by some elbow flexion. By this, I mean that he picks his elbow up high enough that gravity plus natural elbow flexion - rather than inertia - appear to be causing some of the ball's downward motion. This view is inconclusive, but I don't believe his ulnar collateral ligament would hold up for very long if inertia alone caused a bounce that large.

You probably noticed that I was having trouble effectively articulating my thoughts about it. Chris Holt of Pro Bound USA in Clearwater, FL -- who didn't know I was in the audience -- has solved this problem for me by calling it "elbow roll-in".

With that term in mind, watch some of those McCarthy pitches again. Pay attention to his elbow and layback. While there is almost definitely an intertial lag component that helps with McCarthy's layback, the bulk of the layback was done by the way he rolled his elbow into position to lead his forearm.

This method of layback is something for which I've become a big proponent over the past 4 years (for a number of reasons that I don't have time to get into right now). I've needed a succinct way to describe it for some time, and I'm glad Chris was there to help me out.


McCarthy suffers another stress fracture

Jeff Wilson has reported that Brandon McCarthy has been placed on the 7-day DL in Oklahoma City with a stress fracture of his right scapula. Unbelievable.

Seriously unbelievable. Bones get stronger after stress fractures. It's part of the healing process sometimes referred to as overcompensation (or supercompensation). Bones respond to stress and stress fractures by growing thicker, stronger, and more dense.

This is the third diagnosis of a stress fracture in McCarthy's shoulder. Having been through this twice before, McCarthy's shoulder blade should be plenty strong enough to withstand two months of pitching, but it apparently isn't.


What is believable, though? I see a couple of possible explanations.

The original stress fracture from 2007 simply may not be healed. If this is the case, the cause is likely dietary, but it could be that the injury has never been given sufficient time to heal. Stress fractures often become pain-free well before they are actually healed.

Another explanation is that the problem is not actually a stress fracture. Soft tissue is much more susceptible to re-injury than is bony tissue, and the location of McCarthy's injury is a confluence of soft tissue that literally encapsulates the glenohumeral joint.

The recommendations here are running short.

McCarthy attempted a mechanical overhaul, but it doesn't seem to have accomplished its chief goal despite leading to a sparking ground ball rate at Oklahoma City where McCarthy has been excellent.

At this point, it looks like mechanics aren't McCarthy's real problem. If it isn't his mechanics, the culprit is one of the following: diet, strength/conditioning, and genetics.

Genetics, of course, can not be changed, but the other two can be addressed.

In addressing the diet, there are three things to watch for, and they all go hand-in-hand. The goal is improved bone density so the main focal points are calcium, vitamin D, and pH balance. I am not a dietician or a nutritionist, so I will stop short of making specific recommendations.

In addressing potential strength and conditioning issues that may be contributing to McCarthy's problems, a recently published DVD set contains just about everything anyone would ever need to know ranging from prehab and diagnosis to rehab and high performance.

You (and Brandon McCarthy) should check out Optimal Shoulder Performance.

[[Update: The evidence is apparently quite clear. This is, in fact, a scapular stress fracture. Someone who has seen recent video of McCarthy believes that McCarthy had fallen back into old mechanical habits.]]


Another post about Brandon McCarthy

If you're a betting man, you should know that the odds are good that this won't be my last article featuring the mechanics and health of the Texas Rangers starting pitcher Brandon McCarthy.

As my favorite subject, his mechanics have spent a lot of time on my computer monitor playing forward and backward, in slow motion, and in still shots. As a result, I have a small tendency to see a little bit of McCarthy in just about every pitcher. Every once in a while I run into a pitcher whose mechanics have a lot in common with him.

Meet University of Texas at Dallas junior Marvin Prestridge.

In light of recent mechanical changes, Prestridge doesn't look much like McCarthy does these days [Edit: this may not actually be true since I haven't seen high-speed video of McCarthy's new mechanics], but when I pulled up the video I shot of McCarthy last spring, the similarities were striking. The angles aren't quite the same, so you may have to use a little imagination in places.

McCarthy (left) and Prestridge (right) at the top of their leg kicks.

They don't look too similar at the top of their leg kicks, but they appear to have a similar degree of reverse rotation (turning their backs to the plate). McCarthy is more compact, and Prestridge lifts his knee much higher.

McCarthy and Prestridge at hand-break.

At hand-break, their mechanics are starting to run together. McCarthy sits a little lower on his back leg. Prestridge breaks his hands much closer to his body.

McCarthy and Prestridge right before their forearms start to turn over.

Before foot plant, this is the frame where their elbows stop moving upward and backward (toward 1B), and their arms begin external rotation. You can clearly see McCarthy's inverted W and that Prestridge's arm is below shoulder level with an extended elbow. Both pitchers have their arms well behind their shoulders.

I much prefer Prestridge's method of picking up the baseball to McCarthy's method from last spring. As a part of the changes he has made to his mechanics over the past 9 months or so, McCarthy's current pick-up features a full arm swing that positions his pitching arm much like Prestridge's arm.

McCarthy and Prestridge at foot plant.

By the time they hit foot plant, there's only one evident difference between the two: Prestridge is pulling his glove arm back toward second base. McCarthy's glove arm is essentially dead weight, while Prestridge's arm helps create additional rotational force through his shoulders.

McCarthy and Prestridge at peak elbow height just before elbow extension.

Again, the only difference is the glove arm action and position, though it appears that Prestridge has a greater degree of trunk tilt toward 1B.

McCarthy and Prestridge at full arm extension just prior to release.

At this point, the pitchers are literally inches away from letting go of the baseball. Prestridge is able to reach a little more toward vertical, thanks to his 1B-side trunk tilt.

McCarthy and Prestridge after primary arm deceleration.

After release, the pitching arm continues internal rotation while the body tries to keep the arm from flying out of socket. This frame attempts to capture the moment where internal rotation stops.

What's clear in this frame is that McCarthy's arm continued to fly forward, winding up closer to his head than to his chest. Prestridge's arm, on the other hand, is still essentially at shoulder level. This is the most significant difference between the two deliveries.

With McCarthy's arm positioned like this, the head of his humerus is placed in an anatomically questionable position while his rotator cuff applies extreme compressive force at the glenohumeral joint, driving the humerus awkwardly into the scapula.

Prestridge's arm is in a more natural position at this point, and as a result, I do not view his mechanics as risky despite their on-the-surface similarity to McCarthy's old, problematic mechanics.

McCarthy and Prestridge after complete deceleration of the arm.

McCarthy and Prestridge during the recovery stage after their follow-throughs.

You can follow Marvin Prestridge's season here: University of Texas at Dallas Baseball.

[Edit: For reference, here's a link to the video I shot of McCarthy at spring training in 2009.]


Delayed Internal Rotation: Performance Implications

[Last edited on: Tuesday, January 27, 2009 at 7:55 PM; I freely admit that this article isn't very good, and instead is actually pretty worthless. Read it if you want, but I advise that you take none of it as gospel or science or expert advice. I am re-writing it from the ground up, but I am not sure when it will be published.]

In the previous article Biomechanics: Ulnar Collateral Ligament, the discussion centered on what causes UCL tearing and how to prevent it.  In one of my conclusions, I suggested the delay internal rotation until after arm extension.  Now, I will discuss this concept in greater detail.

Delayed internal rotation is the term I use to describe arm action in which internal rotation does not occur until after the arm extends.  Done properly, this arm action allows the triceps brachii to maximally accelerate the forearm directly toward the target.

Internal rotation changes the orientation of the humerus and the direction in which the forearm moves during arm extension, so sequencing is important for efficient energy transfer through the kinetic chain.


The kinetic chain starts at the ground, moves up through the body, and ends in the finger tips.  Since the focus here is on arm acceleration, this analysis of the chain will start at the shoulder with the upper arm in an externally rotated position.

From the shoulder, a series of arm movements is responsible for completing the chain.  As the humerus is accelerated, it establishes a plane of motion.

Velocity of an object moving in an arc.Within this plane, the humerus moves in an arc.  The distal end of the humerus (near the elbow) reaches peak forward velocity shortly after the humerus is perpendicular to the line between second base and home plate.

Beyond this moment, the velocity of the humerus is directed somewhere other than the target.  If the humerus moves past perpendicular, the rest of the arm and the ball move with it.

The kinetic chain "breaks" when the forearm and wrist compensate to put the ball's path back in line with the target.  To maintain the integrity of the kinetic chain, all parts of the arm must apply force in the same direction.

Arm extension and internal rotation are motions that also create arcs, so the same rules apply.

When internal rotation occurs before arm extension, whether the internal rotation is intended or unintended, the forearm moves from the laid back position into a more upright position and the medial epicondyle faces the target.

From this position, the arc created by arm extension is in a plane that is perpendicular to the the line between second base and home plate.  Even though the arm extends rapidly, the contribution to pitch velocity is minimal.

This is a break in the kinetic chain that also negatively affects the potential velocity contribution of pronation.

Arm extension after this point may result in valgus extension overload syndrome which can lead to a number of pathophysiological conditions that may include ulnar collateral ligament tears.

[Note: Dr. Mike Marshall believes that valgus extension overload syndrome does not exist. I tend to believe that it does exist but that it may be irrelevant with regard to pitching. More to come on this.]

When the arm extends before internal rotation, the triceps can accelerate the forearm directly toward home plate in the same direction in which the humerus was accelerated.  In this sequence, the triceps can maximally contribute to pitch velocity and is a strong link in the kinetic chain.

After the arm extends, pronation, wrist flexion, and internal rotation can continue the kinetic chain and powerfully finish the pitch directly toward home plate.


Take a look at Nolan Ryan's arm action in the following image.

Nolan Ryan's arm action - extending the arm from an externally rotated position.

In the first frame, you can clearly see that external rotation has taken place.  The forearm must trail the elbow for the triceps to be able to accelerate the forearm toward homeplate.  External rotation positions the arm for this, but the method used to create this external rotation is as important to UCL health as the external rotation itself is to pitch velocity (see the previous article).

In frame 2, Ryan has nearly finished accelerating his elbow, and arm extension has begun.  You can see that his forearm still trails his elbow in a laid back position allowing arm extension to occur in the same direction as his humerus.

In frames 3 and 4, Ryan's arm approaches full extension, internal rotation begins, and his forearm starts to turn forward toward the plate.  As he releases the pitch, pronation occurs, and internal rotation continues through the deceleration phase.


They don't really agree on this issue, but they have some similar things to say.  In an article written for The Hardball Times in May 2008, Paul Nyman said the following:

What is critical in all arm actions is creating external rotation of the shoulder. Torso rotation (transverse and sagittal) creates the change in direction necessary to cause the forearm to lay back (external rotation of the throwing shoulder). The forearm lays back as a result of its inertia; i.e., a sudden change in direction (rotation of the upper torso) leaves the forearm behind.

Dr. Marshall agrees that the forerarm should lay back, specifically that the ball should be kept at full forearm length horizontally behind the elbow.

Similarly, both agree that a laid back forearm positions the triceps to maximally accelerate the forearm toward home plate.

In his articles for The Hardball Times, Nyman makes no claim regarding the effect of the elbow's path on forearm acceleration, but Dr. Marshall has something to say about elbow paths that have a large lateral component.  From an email he sent me:

When, after 'traditional' baseball pitchers take the baseball laterally behind their body, they drive their pitching arm back to the pitching arm side of their body, they generate forces toward the pitching arm side of their body that 'slings' their pitching forearm laterally away from their body.

In order to prevent this slinging action, the brachialis experiences an eccentric contraction.  This not only opposes passive arm extension - called "forearm flyout" - it also prevents active arm extension by the triceps.

In another point of contention, Nyman says that inertial forearm layback is necessary for maximizing pitch velocity.  Nyman's description of the inertial layback is identical to Dr. Marshall's description of late forearm turnover.

As discussed in my first article, late forearm turnover is the largest risk factor for UCL tears since the flexor-pronator mass does not strongly oppose the valgus torque that it creates.


The mechanics involved in over-hand throwing strongly indicate that the kinetic chain functions more efficiently when internal rotation is delayed until after arm extension.  This means that less energy is wasted on movement that doesn't directly contribute to pitch velocity.

Paul Nyman and Dr. Mike Marshall both agree on the principle reason behind delayed internal rotation - to utilize the triceps brachii as a key link in the kinetic chain - though Dr. Marshall does not agree with all of Nyman's reasoning.

My conclusion: delayed internal rotation has positive performance implications.

This information, coupled with my previous conclusions regarding UCL health, leads me to believe that there are both performance and health benefits to delayed internal rotation.

For more on Paul Nyman and Dr. Mike Marshall, check out my Online Reading list.