Little League Baseball Pitch Counts Vastly Underestimate Throws Throughout a Season
Elizabeth P. Wahl, MD; Tyler S. Pidgeon, MD; Marc J. Richard, MD
Duke University Medical Center, Durham, NC
Shoulder and elbow injuries in youth baseball players have been associated with an increased number of pitches. Accordingly, Little League Baseball (LLB) regulates the number of pitches thrown by athletes per game. Despite these limits, studies have demonstrated ongoing injuries despite guideline compliance. Additionally, pre-season side-to-side difference (SSD) in shoulder horizontal adduction (HA) >15° and internal rotation (IR) >13° has been demonstrated to identify adolescent athletes at increased risk for injury. We hypothesized that official pitch counts significantly underestimate throws in season and that throwing arm pre-season SSD in shoulder ROM predicts loss of playing time related to upper extremity impairment.
Materials & Methods
Eleven and 12-year-old players from an LLB league were provided an elbow sleeve and sensor to wear each time they threw a baseball for an entire season. Parents downloaded a smartphone application to read the sensor. The sensor tracked total throws and pitch-equivalent "high-effort" throws. Shoulder ROM was collected using a digital inclinometer and any loss of playing time related to upper extremity impairment was recorded. Subjects who wore the sensor less than 75% of the time were excluded from the throw count analysis but kept in the ROM analysis.
Nineteen LLB players participated in the study and 18/19 were compliant with sensor use. The sensor-determined mean total throws and mean high-effort throws per player were both significantly higher than the mean official pitch count (Figure 1). No player (0/19) demonstrated an SSD in HA >15° pre- or post-season. Four (4/19) players had a pre-season SSD in IR>13° that did not persist post-season. However, four different players (4/19) had a new SSD in IR>13° post-season. Three players missed playing time due to shoulder or elbow pain. Two of these were considered "at risk" pre-season (SSD in IR>13°) and one was not considered "at risk" pre- or post-season.
Our findings demonstrate that LLB players make significantly more total throws and more high-effort (pitch-equivalent) throws than is recorded by official pitch-counts. Since LLB throwing guidelines designed to reduce upper extremity injury are based on official pitch counts alone, this suggests that young players stress their throwing arms much more over a season than is accounted for by pitch counts. Further, our data supports pre-season SSD in shoulder ROM as a predictor for upper extremity impairment.
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