CS #4: Youth Pitcher, 75 pitches, 17 DVS Score

 

cs #4: Youth pitcher, 75 pitches, 17 dvs score

 

INTRODUCTION

As part of the ongoing series looking at the relationship between a DVS Score and range-of-motion (ROM), we wanted to do a case study capturing the effects of high-intensity throwing on the arm of a 12 year old pitcher. Prior to reading this, if you need to brush up on the significance of ROM, and how it relates to the baseball player, read Range-of-Motion: A Pitcher's Best Friend...or Not. Not only that, but if you're curious as to why they exist, and where they stem from, refer to Range-of-Motion: The Fundamental Truth (Part 1) and Part 2, respectively.

However, as a brief review, keep in mind that a DVS Score is a reflection of mechanical efficiency, and greater efficiency is correlated with less stress. Therefore, because high amounts of stress can cause the body to restrict motion in order to protect itself, individuals with higher DVS Scores won't undergo the same deficit in motion, or exhibit injurious ROM patterns to the same degree, as someone with a lower DVS Score (assuming all other variables held constant). 

HYPOTHESIS

Based on the fact that the subject in this study has a DVS Score of 17, he will endure less relative stress during throwing, and therefore not experience any significant loss of motion in the throwing shoulder. Additionally, we expect he will also exhibit less injurious ROM patterns immediately after throwing. This will be assessed by looking at trends in Dominant Total Arc Motion Deficit (DTAMD), Glenohumeral Internal Rotation Deficit (GIRD), and Glenohumeral External Rotation Deficit (GERD). More specifically, we expect each of these measurements to trend in a positive direction, which would be considered a less injurious direction as defined by research.   

Methods

  • Setting: Controlled, High-Intensity Bullpen
  • Number of Subjects: 1
  • Age of Subject: 12
  • Number of High-Intensity Throws: 75
  • Average Ball Velocity: 53 mph
  • Max Ball Velocity: 55 mph
  • DVS Score: 17

One asymptomatic, 12 year-old male baseball pitcher with a minimum DVS Score of 17 participated in the study. Passive ROM measurements were recorded using a digital inclinometer for shoulder Total Arc Motion (TAM), Internal Rotation (IR), and External Rotation (ER) on both the throwing and non-throwing arms. For each shoulder, the limb was moved passively in each direction until maximal motion occurred. In order to ensure each shoulder achieved its full range of motion, the examiner used a combination of capsular end-feel and visualization of compensatory movement. The humeral head was not stabilized in order to allow for natural shoulder motion to occur. For each measurement of internal rotation and external rotation, the scapula was securely stabilized on the table. Measurements were taken at rest prior to throwing, and then post measurements were taken immediately after completion of throwing. As this study was conducted in a controlled setting, the pitch-count was set at a maximum of 75 pitches. 

results

Post throwing, the subject gained 1º in Dominant Total Arc Motion (DTAM), and exhibited an 8º improvement in DTAMD relative to pre-throwing measures. Overall, the subject didn't exhibit a significant decrease in dominant-arm ROM (i.e. DTAM), nor trend in a more injurious direction, relative to other studies in existence (see CS #1 under "Discussion"). On the contrary, the subject actually gained motion within the dominant arm, and showed patterns similar to that of a healthy throwing shoulder. The full data set and analysis are posted below.

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BREAKDOWN

Before we break down the table above, keep in mind that aside from DTAM, DTAMD, GIRD, and GERD are characterized by the relationship of the throwing arm to the non-throwing arm. And as the primary throwing-related risk factors hinge upon the throwing arm becoming restricted in motion to a certain degree relative to the other side, any negative trends in these categories can be considered injurious. On a more general note, because restrictions in motion usually relate to overuse and dysfunction, significant losses in DTAM (i.e. total motion within the throwing arm) can also be considered injurious. 

With that said, you can see DTAM actually improved by 1º relative to resting, which is contrary to what is expected after high-intensity throwing. Furthermore, notice that DTAMD, GIRD, and GERD all trended in a positive direction from resting to immediately post throwing. Once again, these are patterns that trended in the opposite direction from what research considers to be injurious. Lastly, if you look at the "DTAMD" column, you can see that at no point does the subject become less than -5. This is significant because when DTAMD becomes less than -5, the likelihood of sustaining a throwing-related injury exponentially increases. 

discussion

It is no secret that the epidemic surrounding throwing-related injuries in baseball is just as prevalent, if not more so, in the youth population than in the amateur and professional ranks. This largely stems from a culture that demands more practice, more games, and more throwing. The classic "more is better" mentality. Combine this with the inefficient throwing pattern commonly seen in today's culture, and injuries are just around the corner. This has been shown to be true by not just the spike in injuries amongst youth and adolescent players, but by the existence of injurious shoulder ROM patterns that are prevalent throughout all levels of baseball. Regardless of all the theories as to why these trends exist, they all boil down to a simple fact: the stress being applied on the outside exceeds what the body and muscular system can effectively tolerate on the inside. 

Although there are numerous factors that play a role in this equation, an individual's throwing mechanics can drastically influence the amount of stress endured from each throw. This can be further substantiated by correlating mechanics with ROM. As a DVS Score quantifies the efficiency within any pitcher's throwing pattern, it can be expected that higher DVS Scores correlate with better, less injurious ROM patterns. And once again, this is exactly what we saw in CS #4. The 12 year-old subject in this study portrayed a DVS Score of 17, was able to throw 75 pitches at max-effort intensity, and yet failed to exhibit any signs or patterns that indicated injury or overuse. Why? His body and muscles were able to effectively support the task at hand, which is at least partially, if not largely due to his throwing efficiency.  

conclusion

Throwing-related injuries are rarely the result of a single, large, traumatic event; instead, they occur in response to the accumulation of smaller, sometimes unrecognizable injuries sustained over a longer period of time. How well a player can handle the acute demands of any given throwing session is everything when dealing with these types of injuries. Players with higher DVS Scores are going to be better at doing this, as a higher DVS Score correlates with greater efficiency, and thus less stress exerted onto the throwing arm. How do we know this, (aside from what our extensive statistical database shows)? By correlating a DVS Score with proven, shoulder range-of-motion risk factors that have been consistently linked to throwing-related injuries over the last several decades. 

-Will