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Int J Sports Phys Ther. 2012 October; 7(5): 548–557.
PMCID: PMC3474308

SHOULDER RANGE OF MOTION, PITCH COUNT, AND INJURIES AMONG INTERSCHOLASTIC FEMALE SOFTBALL PITCHERS: A DESCRIPTIVE STUDY

Ellen Shanley, PhD, PT, OCS, CSCS,1,2,3 Lori A. Michener, PhD, PT, ATC,1,4 Todd S. Ellenbecker, DPT, OCS, SCS,1,5 and Mitchell J. Rauh, PhD, PT, MPH, FACSM1,6

Abstract

Background/Purpose:

Injury rates for softball players are similar to baseball players yet information regarding risk factors, pitching, and physical characteristics for high school windmill softball pitchers is limited. This information is needed to guide prevention, training, and rehabilitation efforts. The purpose of this study was to report descriptive data regarding the physical characteristics and pitching volume experienced by high school softball pitchers during one academic season. A secondary aim was to track and describe upper extremity injuries suffered by high school softball pitchers throughout the course of the 2009 season.

Methods:

Twelve uninjured female softball pitchers (13‐18y) from 5 Greenville, South Carolina high schools participated. Prior to the 2009 season, the pitchers' shoulder internal, external, total arc of rotation and horizontal adduction PROM was measured. During the 10‐week season, aggregate pitch counts (pitch volume) and occurrence of upper extremity injury were tracked for each pitcher.

Results:

Mean preseason internal, external, and total arc of rotation PROM was observed to be similar between the pitchers' dominant and non‐dominant shoulders. The PROM measures of horizontal abduction (HA) appear to demonstrate a side‐to‐side difference with less HA on the dominant arm of the pitchers who were examined. Subjects threw in an average of 10.1 games (±4.9) during the season. Six pitchers threw in 60% or more of the team's games and 3 of 12 pitchers pitched less than 25% of games. Pitchers averaged 61.8 pitches per game (±31.5) and 745.8 (±506.4) per season. Pitch count data did not appear to be different between injured and non‐injured pitchers.

Conclusions:

Knowledge of pitch volume can be used to prepare windmill softball pitchers for the seasonal stresses, guide establishment of goals when recovering from injury, or assist in training for an upcoming season. Further research is needed to examine larger samples of pitchers over multiple seasons and years.

Level of Evidence:

III

Keywords: Pitch count, shoulder, softball

INTRODUCTION

Softball has continued to be a popular sport for high school athletes. In the past decade, participation at the high school level has grown by 16%.1,2 During the 2008‐09 school year, girls' softball was the third most popular high school sport for girls.2 As participation has risen over the past decade, the number of players at risk for overuse injury has also increased.2 The overall incidence of injury, per 1000 athletic exposures (AEs), during an interscholastic season has ranged between 0.95 and 5.6 per 1,000 AEs for softball players.35 The upper extremity has been reported to be among the most commonly injured body regions in softball (40‐52%).3,4,6,7 Shanley et al reported that the upper extremity was the most commonly injured body region for softball players with an overall rate of 2.9/1,000 AEs.3 Further, Rauh et al reported a 2‐ and 3‐fold risk of shoulder and rotator cuff re‐injury (an injury occurring after the initial injury to the same body location after recovery from the initial injury) in high school softball players.8 While the prevalence of overuse injuries has varied widely (30‐85%) among softball athletes, these injuries have primarily been related to pitching and throwing in the field.911 Recently, Shanley et al. suggested that most high school softball shoulder injuries occurred early in the season and were related to an increase in game participation.3

In order to institute prevention strategies aimed at minimizing injuries in softball, a thorough understanding of the population at risk, participation level, incidence of injury, and risk factors for injury should be established. For baseball players, extrinsic factors including performance characteristics (pitching with pain or fatigue, pitch types, innings pitched, and pitch counts)1214 have been suggested as contributors to non‐contact baseball‐related injuries. Intrinsic factors, such as, range of motion (ROM) deficits in internal rotation (IR) greater than 20° without concurrent increases in external rotation (ER) ROM combined with a reduction in side‐to‐side horizontal adduction (HA) have been associated with posterior shoulder tightness and are hypothesized to be pathological.1519 Currently, few, if any, prospective studies are available on intrinsic or extrinsic risk factors risk factors for adolescent softball players, especially pitchers.20 Risk factors theorized to contribute to arm injuries among windmill softball pitchers include pitching with fatigue, decreased shoulder proprioception, posterior shoulder tightness, and innings pitched.2123

In softball, participation is non‐continuous and varies from outing to outing. For non‐continuous sports, accounting for the actual number of plays is the more useful method of assessing risk as compared with the number of games played.24 Kerut et al reported that the number of pitches thrown was the risk factor most strongly correlated with pitching injuries among youth baseball players.24 They concluded that the overall number of pitches likely better accounted for the stresses placed on an athlete's arm rather than merely tracking participation in games or innings. However, innings and games played have not been found to predict overall injury or the severity of injury for high school pitchers.14,22

The American Academy of Pediatrics Committee on Sports Medicine and Fitness has recommended restrictions on the number of pitches thrown in games, as well as instruction in throwing mechanics and training principles for both softball and baseball athletes.25 In 2007, Little League Baseball published regulations for game pitch counts and pitching rest days by age group.26 While these regulations became mandatory for baseball in 2010, no guidelines have been established for softball. The recommendations for baseball were based on three descriptive research reports from 2001‐2006 indicating an association between injured youth (9‐12 years) players and an increased number of pitches thrown as compared to healthy controls.14,27,28 Similar descriptive studies for high school softball pitchers are not available.

The associations between injuries, pitch count data, and innings played are not well documented. In a descriptive study of collegiate softball players, Loosli et al21 reported softball pitching injuries and categorized them according to mean innings pitched for each injury severity category. Specific pitch counts have not been associated with injury at the collegiate level. At the interscholastic competition level, the National Federation of State High School Associations has not recommended pitch count standards for high school softball or baseball.1 High school baseball pitch counts are regulated by each state, but pitch counts remain unregulated for high school softball.1

To the knowledge of the authors, tracking of pitch counts has not been reported for high school aged softball pitchers. Thus, the objectives of this study were to 1) describe the pitch volume for high school windmill softball pitchers, 2) to describe the shoulder passive range of motion (PROM) of internal rotation, external rotation, and horizontal adduction for high school windmill softball pitchers, and 3) to describe and compare pitch counts for those athletes developing arm injuries versus those remaining uninjured throughout an interscholastic season.

METHODS

The study prospectively examined 12 female high school windmill softball pitchers in 5 Greenville, SC high schools during their 10‐week season. Players between the ages of 13 and 18 were recruited to participate in the study. Subjects were excluded from the study if 1) they were being treated for a shoulder or elbow injury at the beginning of the season, or 2) unable to participate on the first day of practice because of upper extremity injury or soreness. The Rocky Mountain University of Health Professions Institutional Review Board approved the study. Parental consent and athlete assent were obtained.

Data Collection

Questionnaire

Prior to the 2009 spring interscholastic season, the pitchers completed a study questionnaire on baseline characteristics. Included were questions regarding years of playing experience, hand dominance, and history of prior injury (Appendix 1).

Shoulder Passive Range of Motion (PROM)

Shoulder PROM of IR and ER were measured using a standard goniometer with a bubble level affixed to the stationary arm for dominant and non‐dominant upper extremities.2931 Subjects were placed in supine and their shoulders positioned in 90° of abduction. Measurements for IR and ER were performed in the plane of abduction and a small towel roll placed under the distal humerus was used to maintain the position of the humerus. A posterior force by the thenar eminence and thumb was then applied through the coracoid process to stabilize the scapula prior to the arm being rotated,29,3234 and the humerus was passively positioned at the end of either IR or ER PROM with the force of gravity acting on the arm.32 The goniometer stationary arm was placed along the midline of the lateral forearm and the axis of the goniometer was aligned with the olecranon.32 Two examiners performed all IR and ER measurements with one examiner providing stabilization force to maintain the shoulder position while the other examiner obtained the PROM measurement.35 The mean of 2 trials for was used for data analysis.

Shoulder Horizontal Adduction (HA) PROM

Shoulder HA PROM was measured in the supine position on the standard table with the scapula retracted and stabilized via examiner pressure with the thenar eminence contacting the lateral border of the scapula.11,36 The upper extremity was passively horizontally adducted across the body with the arm starting at 90 degrees of abduction in neutral rotation and the elbow flexed to 90 degrees.11,36 The angle between the humerus and the horizontal plane from the superior aspect of the shoulder was measured via goniometry, which has been described in the literature to be reliable and valid.11,36 Two measurements of HA PROM were performed and the mean calculated for each arm.11,36

Pitch count

Over the course of the season, aggregate pitch counts and upper extremity injuries were tracked for each pitcher. A team coach collected pitch counts during each game for her pitcher. The pitch counts were recorded on the official game‐scoring sheet. The primary investigator (ES) visited the school weekly to answer any questions and verify the previous week's pitch counts. All teams emailed weekly pitch counts per game to the primary investigator.

Injuries

Prior to the 2009 spring interscholastic season, participating athletic trainers were trained in the use of the Athletic Health Care System Daily Injury Report form.37,38 From the first official day of practice until the last regular or postseason competition, two parallel recording procedures, the Simtrak mobility system (Premier Software, Inc. Winfield, Illinois) and the Athletic Health Care System Daily Injury Report form,37,38 were used to track upper extremity injury incidence. An upper extremity injury was defined as any pitcher's shoulder or elbow muscle, joint, tendon, ligament, bone or nerve complaint reported by the player that occurred during any softball team sponsored game or practice during the season.37 All upper extremity injuries regardless of onset type, gradual or immediate, and time loss were recorded and confirmed by the school's athletic trainer.

DATA ANALYSIS

Means and standard deviations were calculated for all demographic data, range of motion variables, and pitch counts for softball pitchers. The number of subjects and injuries were too small to warrant tests of statistical comparison. All descriptive data was calculated using SPSS (SPSS for Windows, SPSS Science INC, Chicago, ILL).

RESULTS

At the beginning of the season, all pitchers (n= 12) were without injury and were capable of full participated in team activities. Two thirds of the pitchers reported playing an additional position in games during the season but denied participation as a catcher. Demographic data for the pitchers is presented in Table 1. Prior to the start of the season, 17% of the pitchers reported a previous upper extremity time loss injury. Preseason PROM variables are shown in Table 2. The PROM data for IR, ER, and total rotation seems to suggest similarity between the dominant and non‐dominant shoulders. The HA PROM appears less similar, with an average side‐to‐side difference of 6.25° less on the dominant compared to the non‐dominant arm.

Table 1.
Characteristics of high school softball pitchers during the 2009 interscholatic softball season
Table 2.
Preseason shoulder passive range of motion (PROM) data for high school softball pitchers.

Pitch count data for the softball players is presented in Table 3. On average, softball pitchers threw in 10.1 games (± 4.9) during the season. Six of the 12 pitchers threw in 60% or more of their games, and 25% (n=3) pitchers appeared in less than 25% of the team's contests. Softball pitchers threw on average 4.3 innings per game and 14.9 pitches per inning. Game and seasonal pitch volumes averaged 61.8 (± 31.5), and 745.8 (± 506.4) respectively.

Table 3.
Means and standard deviations for pitch counts among high school pitchers.

Only two (16.7%) of the pitchers incurred a shoulder injury during the 10‐week season. Pitchers who sustained an upper extremity injury during the season had similar pre‐season shoulder PROM compared to non‐injured pitchers for dominant IR (59.8 ± 3.9 vs 60.8 ± 9.0), side‐to‐side IR loss (8.8 ± 13.1 vs 1.0 ± 7.3), and dominant total arc of motion (180.5 ± 18.4 vs 176.0 ± 5.6). In this small sample, the injured pitchers appeared on average to have less dominant HA than uninjured pitchers (20.3 ± 3.2 vs 32.6 ± 11.8) but appeared with to have similar non‐dominant HA (34.5 ± 2.1 vs 37.2 ± 13.7). The mean pitch count per season for the injured pitchers (1170.5 ± 567.8) was higher than the non‐injured pitchers (660.8 ± 479.0), yet examination of the standard deviations demonstrates clear overlap of pitch count between some athletes in each group. (Table 4). Mean game pitch totals for the injured and uninjured pitchers appeared similar (Table 4).

Table 4.
Pitch count means and standard deviations in injured versus non‐injured high school softball pitchers.

DISCUSSION

In efforts to minimize the occurrence of shoulder and elbow injury among baseball pitchers, several individuals and organizations have published recommendations for the modification of pitch volume in baseball.14,2528 These recommendations have been directed toward game,14 season,14 and yearly pitch counts.28 Although the regulation of pitch counts among windmill softball players has been recommended,39 to the authors' knowledge, actual pitch count limits for softball have not been established and high school softball rules do not address game or seasonal pitch counts.1 The current study's descriptive data documents PROM and pitch counts for high school windmill softball pitchers representing an initial phase in establishing safe guidelines for participation. While the mean pitch count was higher for injured pitchers than for uninjured pitchers, the standard deviations in each group seems to suggest that the pitch count totals could be similar between groups. The descriptive data from this study should be interpreted with caution based on the small sample size and number of injured pitchers.

Shoulder PROM

While shoulder PROM measures have been reported for high school softball players in general, the authors are unaware of data specifically describing pitchers therefore making comparisons difficult due to limited reports.20 The side‐to‐side shoulder PROM for IR and ER found in this study's pitchers appear to differ from those reported in previous studies of high school20 and collegiate softball players.23,40 Specifically, no differences were found between the pitchers dominant and non‐dominant shoulder PROM which contrasts with other reports documenting an altered total arc of PROM in softball players.20,23,40 The lack of agreement with prior reports may be partially related to the differences in the player position studied; the current study examined pitchers only whereas the other reports measured both pitchers and position players. As pitchers primarily use a windmill motion and position players exclusively use an overhand throwing motion, the differences in throwing mechanics may affect their shoulder rotational motion composition, thus accounting for the differences in ROM. The current methods should be replicated using a larger sample of softball pitchers in order to be able to compare to the results of this study.

Horizontal adduction PROM measures appear to demonstrate a side‐to‐side difference with less HA on the dominant arm of the studied pitchers. These results appear similar to the documented patterns of HA of other athletes.31,41,42 The similarity in the horizontal adduction measure may be associated with the comparable mechanics following ball release (cross body adduction, internal rotation, and pronation) between baseball and softball athletes. Further research is needed to investigate these results in a larger sample of pitchers.

Average Pitch Count: Game

Overall, the mean number of pitches thrown per game by a pitcher in the current sample was 61.8± 31.5, which is lower than those reported among collegiate softball players where an average of 90 pitches were thrown per game (range 60‐141).43 Only 2 pitchers in the current sample averaged 90 or more pitches per game. Thus, the findings of the current study indicate that although these high school softball pitchers (14.9/inning) were throwing a similar number of pitches per inning (collegiate: 12.7/inning) they threw fewer innings and pitches per game with a resultant lower total volume than the collegiate softball pitchers.43

Injury by Average Pitch Count: Game

While the injured softball pitchers demonstrated a pattern toward throwing more pitches per game on average than the non‐injured softball pitchers no clear differences were observed. Only two of the 12 studied pitchers averaged 90 or more pitches per game. In comparison to prior reports, the injured pitchers in the current study averaged approximately 78.3 (± 20.1) pitches per game which was slightly lower than collegiate softball pitch counts among uninjured pitchers (mean: 90).43 The low number of injuries in the pitchers who threw more than 90 pitches per game may be partially related to the small number of pitchers that exceeded this average number of pitches.

Average Pitch Count: Season

In the current study, the softball players threw an average of 745 pitches and 2 pitchers threw more than 1500 pitches during their season. Werner et al. reported that adolescent windmill softball pitchers often throw more pitches during a weekend tournament (1200‐1500 pitches) than the same age baseball pitchers throw in a season.23 However, the softball pitchers in the current cohort had lower total pitch volume over their 10 week season than Werner reported for those who participated in elite weekend softball tournaments.23

Injury by Average Pitch Count: Season

The two injured softball players averaged almost 1200 pitches/season while the other 10 uninjured players' averaged 660 pitches/season (approximately 55% less). While injured softball players threw more pitches on average per season than their uninjured counterparts examination of the standard deviations associated with these means demonstrates clear overlap of pitch count between athletes in each group and probably indicates a similar seasonal pitch count between groups. The small number of softball pitchers participating and few injuries sustained among the players in the current study limited the authors' ability to perform statistical analysis and further study is required in this area. To the authors' knowledge, game and seasonal pitch counts for high school softball pitchers (injured or non‐injured) have not previously been reported. Two prior survey studies recorded the number of pitched innings reported by injured collegiate softball pitchers (82‐93, mean = 88.322 and 86‐209, mean = 145).21 Axe et al.44 stated that collegiate softball pitchers averaged 12.7 pitches per inning. For comparative purposes, the injured softball pitchers would have thrown an average of 1,121 pitches per season in the cohort presented by Hill et al22 and 1,837 pitches in the Loosli survey21 if they averaged 12.7 pitches per inning (range 1041‐2654). The injured high school softball pitchers in the current study threw a similar number of pitches per season as the number that would be attributed to the collegiate pitchers in the Hill study22 but fewer than those reported by Loosli et al.21

Strengths

The overall prospective study design helped minimize several study biases. Recall bias and misclassification of injuries were minimized as trained health care professionals collected the data in a controlled, systematic, and prospective manner. The authors contacted coaches and athletic trainers on a weekly basis to verify injuries and pitch count data. Injury data were collected with parallel systems in order to increase the accuracy of such data. The subjects in this study were high school athletes that were supervised carefully during each game and throughout their season. The amount of exposure was consistently monitored throughout a short season. Additionally, the study was conducted over a relatively small geographical area, which allowed the researchers to control factors related to exposure (climate and competition level) and documentation of injury circumstances.

Limitations

Several limitations of the current study should be noted. The sample size was small, because each team had 1‐2 softball pitchers that participated in most games. The relatively low incidence of injury in softball and the smaller sample size also limited the ability of the authors to perform statistical analysis and identify risk factors. The characteristics and practice patterns of the included high school softball teams may differ from those in other geographical regions limiting the generalizability of the findings. In this study sample, pitch types were not studied but may be important as a potential risk factor for injury as theorized by other researchers.1214

CONCLUSION

PROM data for IR, ER, and total rotation seem to suggest similarity between the dominant and non‐dominant shoulders for windmill pitchers. Several authors have documented altered patterns of rotational ROM for softball position players.20,23,40 The average number of pitches per game and per season for the current sample of high school softball pitchers appeared similar to estimates of collegiate pitchers but less than elite pitchers described by Loosli in 1992.21 While mean counts per game and season tended to be higher for injured pitchers than non‐injured pitchers, when examining the ranges and standard deviations it is possible that no differences between these groups existed. Several authors have documented a need for pitch counts to be documented and implemented in windmill softball.21,39,45 Differences in ball weight,46 pitching surface,46 biomechanics23,39,47,48 and field dimensions46 make it difficult to justify and questionable to use established baseball pitching guidelines. Baseline descriptive data are needed to establish tolerance and response to the windmill pitching motion. Recommendations for pitch count limitations, preseason/ in‐season conditioning, and performance enhancement programs should only be recommended after norms are established. Future studies with larger sample sizes are recommended to continue examining pitch count and also examine variations in pitch type as potential risk factors for upper extremity injury risk in high school softball players.

APPENDIX

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Articles from International Journal of Sports Physical Therapy are provided here courtesy of The Sports Physical Therapy Section of the American Physical Therapy Association