Do Pitching Restriction Policies Reduce Shoulder and Elbow Injuries in High School Baseball Players?

Abstract

Background:

Shoulder and elbow injuries (SEIs) remain prevalent among high school (HS) baseball players. Pitching restriction (PR) policies were mandated by the National Federation of State High School Associations (NFHS) in 2016 as an injury prevention strategy to set workload limits and reduce overuse injuries. The effect of PR policies on HS baseball SEIs remains unknown.

Hypotheses:

(1) SEI rates in HS baseball players would be lower in the 3 seasons after PR policy implementation when compared with the 3 seasons before PR policy implementation and (2) specific components of PR policies would be associated with statistically significant decreases in SEI rates.

Study Design:

Descriptive epidemiological study.

Methods:

NFHS member state PR policies were obtained from publicly available websites, and components of each policy were analyzed for similarities and differences. SEI/exposure data for US HS baseball players were obtained from High School Reporting Information Online, a sports injury surveillance system. Athletic trainers reported practice and competition injury and athlete-exposure (AE) data from a national school sample during the 2013-2014 through 2018-2019 academic years.

Results:

During the study period, 295 (164 shoulder, 131 elbow) injuries occurred during 1,554,708 AEs. No statistically significant changes were found in SEI rates, shoulder-specific rates, or elbow-specific injury rates after PR policy mandates were implemented. When analyzing injury rates for practices and competitions collectively, consecutive pitching day rest rules (incidence rate ratio [IRR], 0.32; 95% CI, 0.22-0.46), ≤105 pitch daily maximum (IRR, 0.40; 95% CI, 0.31-0.51), different PR policy rules for regular versus postseason (IRR, 0.43; 95% CI, 0.27-0.65), varsity versus subvarsity pitch count maximums (IRR, 0.46; 95% CI, 0.35-0.59), and ≥4 days’ rest if >105 pitch count (IRR, 0.53; 95% CI, 0.42-0.68) provided protective effects against SEIs compared with PR policies without these components.

Conclusion:

Specific components of PR policies rather than a national PR policy mandate were associated with significant reduction in SEI rates in HS baseball players. The presence of a consecutive pitching day rest rule and daily maximum pitch count of ≤105 pitches were associated with significant reductions in SEIs based on total (practice and competition) exposures, practice exposures, and competition exposures.

Shoulder and elbow injuries remain prevalent among high school (HS) baseball players. Approximately one-fourth of HS baseball players pitch, ¹⁴ and while shoulder injury rates in baseball players have been trending downward in some studies,^4,26 elbow injury rates and specifically ulnar collateral ligament (UCL) reconstruction surgeries have continued to increase significantly over the past few decades.^{2,3,6,9,10,25,28} Several recent studies have identified the 15- to 19-year age group as having an annual UCL reconstruction surgical incidence higher than any other demographic.^8,17 Numerous risk factors for shoulder and elbow overuse injuries in baseball players have been identified, including but not limited to pitch count, innings pitched per season, pitch velocity, throwing mechanics, days of rest between pitching outings, fatigue, and showcase participation.^3,5,9,13,28

In 2014, Major League Baseball and USA Baseball unveiled the Pitch Smart arm safety initiative in an effort to reduce overuse injuries in youth and adolescent baseball players. ²¹ As an integral part of this initiative, age-specific pitch count limits and required rest recommendations were provided to set workload limits for pitchers to reduce the likelihood of pitching with fatigue.^23,29

In June 2016, the National Federation of State High School Associations (NFHS) Baseball Rules Committee approved a revised pitching policy (in Rule 6-2-6) requiring each NFHS member state association to develop its own pitching restriction (PR) policy based on in-game pitch counts to afford pitchers a required rest period between pitching appearances. ¹² Before 2016-2017, only a handful of states had adopted PR policies: Vermont (2007-2008), South Dakota (2008-2009), Colorado (2015-2016), Florida (2015-2016), and Kentucky (2015-2016). The mandate was implemented for the 2016-2017 academic year for the majority of the 48 states who competed in HS baseball (Note: Montana sanctioned HS baseball as of 2022-23; as of 2025-26, South Dakota and Wyoming remain the only two states that do not offer state-sanctioned HS baseball among the 50 U.S. states. However, while South Dakota’s state athletic association does not officially sanction baseball, South Dakota high schools do compete in baseball and utilize a PR policy, with organization at the local level, but no state championship structure. Thus, South Dakota was included as one of 48 states with a PR policy during the study period). Eight of the 48 states (Arizona, Florida, Illinois, Kansas, Maryland, Missouri, North Carolina, and South Dakota) adopted policies fully compliant with USA Baseball pitching guidelines (https://www.mlb.com/pitch-smart/pitching-guidelines/ages-15-18) for 17- to 18-year-olds, ²³ while the remaining states adopted partially compliant policies with maximum pitch counts ranging from 100 to 125 pitches for varsity pitchers and 75 to 125 pitches for subvarsity pitchers, with rest day requirements after a maximum outing ranging from 0 to 5 days for both varsity and subvarsity pitchers. While the variability of pitch count rules in HS baseball as well as the theoretical effect of different pitch count limits and rest day combinations on game, weekly, and seasonal pitch totals in HS baseball pitchers has been evaluated ¹⁹ and a systematic review assessing support for Pitch Smart guidelines (PSG) in the literature has been performed, ²² no study has evaluated the effect of PR policies on shoulder and elbow injuries in HS baseball players.

The purpose of this study was to evaluate the effectiveness of current PR policies implemented by NFHS member states in reducing shoulder and elbow injuries in US HS baseball players. Our primary hypothesis was that shoulder and elbow injury rates in HS baseball players would be lower in the 3 seasons after implementation of PR policies as compared with the 3 seasons before implementation of a national mandate. Our secondary hypothesis was that specific components of PR policies, including lower pitch count maximum, higher required days of rest, longer consecutive pitching day rest rules, the presence of a weekly maximum pitch count, the presence of a “workup” plan, different rules for regular versus postseason play, and the presence of rule violation consequences, would have associations with decreased shoulder and/or elbow injuries.

Methods

Shoulder and elbow injury and exposure data for US HS baseball players were obtained from High School Reporting Information Online (HS RIO), a validated, internet-based sports injury surveillance system maintained by the Datalys Center for Sports Injury Research and Prevention (Indianapolis, Indiana). The methodology of this surveillance system has been previously described. ²⁴ In brief, HS RIO annually collects injuries and athlete-exposures (AEs) occurring in organized competitions and practices from a convenience sample of US HSs with a certified athletic trainer (AT) available to report data. Data for HS RIO during the 2013-2014 through 2018-2019 school years originated from 2 samples. While 883 HSs reported for baseball during the study period, 100 schools were randomly selected as a nationally representative sample that reported data for 9 sports. All schools were categorized into 8 sampling strata by geographic location (Northeast, Midwest, South, and West) and HS size (eg, enrollment ≤1000 or >1000 students). Schools not selected randomly were able to participate as part of a convenience sample. The expanded convenience sample reported the 9 sports mentioned in addition to sports that were less commonly sponsored. Given the nature of the study design, informed consent was not obtained from study participants. Institutional review board approval was granted from Boston Children’s Hospital.

Identification of PR Policies

PR policies for each NFHS member state were obtained from publicly available websites. The components of each state’s PR policy were analyzed for similarities and differences (Appendix 1). Maximum daily pitch counts and required days of rest (varsity vs subvarsity), consecutive pitching day rest rule, weekly maximum pitch count, in-season workup plans, different rules for regular versus postseason play, and rule violation consequences were among the rule distinctions identified. Details of each NFHS member state’s PR policy (including components included in the next section) can be found in Appendix 1.

Definitions and Data Categorizations

Shoulder and elbow injuries: For this paper, we defined these as injuries occurring during organized practices or competitions. HS RIO Codebook 2023-2024 was used to categorize the basic injury mechanism and baseball-specific injury mechanism or activity. As this study sought to evaluate the effectiveness of current PR policies in reducing throwing- and pitching-related shoulder and elbow injuries, injury mechanisms related to contact, batting, sliding, and running bases were excluded (Figure 1). In the few instances (such as unknown, fielding batted or thrown ball, other, general play, conditioning) in which the baseball-specific activity at the time of injury was not categorized as pitching or throwing, AT comments or other variables that documented a throwing- or pitching-related mechanism were identified in the HS RIO database, which verified these injuries as pitching- or throwing-related. An AE was defined as 1 athlete participating in 1 practice or competition. A reportable injury was defined as one that (1) occurred during an organized HS athletic practice or competition, (2) required medical attention from a team AT or physician, and (3) resulted in restriction or alteration of the athlete’s participation status. For each injury, the AT completed a detailed report that included date of injury, exposure (eg, practice vs competition), injury characteristics (eg, body site, diagnosis, severity, and time loss), and circumstances leading to injury (eg, mechanism and specific activity at time of injury).

Figure 1.

Flow diagram. Headings in all capital letters indicate basic mechanisms of injury. Subheadings not capitalized indicate baseball-specific mechanisms of injury or activity as defined by HS RIO Codebook 2023-2024. ATs, certified athletic trainers; HS, high school; HS RIO, High School Reporting Information Online.

PR policy (yes/no): Designates that an NFHS member state implemented/did not implement a PR policy during the school year a shoulder or elbow injury was recorded. It is important to recognize that 5 NFHS member states implemented PR policies in HS baseball before the 2016-2017 NFHS mandate, while 1 NFHS member state (Louisiana) implemented their PR policy in 2017-2018 (Appendix 1). Before 2019-2020, Massachusetts utilized Major League Baseball rules for their PR policy.

Daily maximum 105 pitches or less, 4 days’ rest if >105 pitch count (yes/no): According to current USA Baseball/PSG, the maximum number of recommended in-game pitches for a 17- to 18-year-old athlete is 105 pitches followed by 4 days of rest. ²³ While USA Baseball/PSG recommend 4 days’ rest once a daily pitch count of ≥81 pitches is exceeded for 17- to 18-year-olds, significant variability regarding maximum pitch count requiring 4 days’ rest exists among the 48 NFHS member states, with 105 pitches (range, 76-120 pitches) being the most common maximum number of pitches allowed for 4 days’ rest. ¹⁹ Additionally, while PSG recommends a daily maximum pitch count of 95 pitches for 15- to 16-year-olds followed by 4 days of rest once a daily pitch count of ≥76 pitches is exceeded, we elected not to further stratify HS pitchers by age-related maximum pitch counts (eg, 15- to 16-year-olds vs 17- to 18-year-olds) as only 5 states (Arizona, Florida, Illinois, Maryland, and Missouri) followed PSG for daily maximum pitch counts according to this distinction.

Pitch count maximum, varsity versus subvarsity (yes/no): USA Baseball/PSG recommend a maximum pitch limit of 95 pitches followed by 4 days of rest for players aged 13 to 16 years. Subvarsity designates either junior varsity (JV) or freshman team participation.

Consecutive pitching day rest rule (yes/no): While restricting pitching to no more than 2 consecutive days is the most common rule among NFHS member states that have such rules, rule distinctions vary widely.

Weekly maximum pitch count (yes/no): Only 4 (8%) states include weekly maximum pitch counts in their PR policies (range, 150-205 pitches in a 5- to 7-day calendar).

Workup plan (yes/no):“Ramp-up” or workup plans restrict the maximum allowable pitches from the first day of competition (ie, no more than 75 pitches in weeks 1-3, no more than 95 pitches in weeks 4-6) to allow for growth and arm strength to develop and as an approach to arm safety.

Rules regular versus postseason (yes/no): Pitch count maximums and weekly maximum pitch counts are frequently liberalized during postseason play in many NFHS states.

Rule violation (yes/no): Rule violation consequences reinforcing PR policies include forfeiture of game, monetary fines, and game suspension(s) for the offending team’s head coach, as well as HS program probations. In total, 37 (77%) states have rule violation consequences reinforcing their PR policies.

Statistical Analysis

Descriptive statistics delineated the number and rates of shoulder and elbow injuries sustained by HS baseball players during practices and competitions during NFHS-sanctioned baseball seasons 2013-2014 through 2018-2019. Incidence rate ratios (IRRs) were calculated with 95% confidence intervals and evaluated using the z test to determine whether PR policies or their components led to significantly reduced injury rates. Because the injury data represent rates per 10,000 AEs, Poisson log-linear regression modeling was used to compare incidence rates between groups. Data were analyzed using SPSS software Version 29 (IBM Corp) and MedCalc software (MedCalc Software Ltd). A 2-tailed P value <.05 was used for determining statistical significance.

Results

Comparison of Injury Rates: Pre- Versus Post-NFHS PR Policy Mandate (2016)

During the 2013-2014 through 2018-2019 school years, ATs reported a total of 405 shoulder and elbow injuries (236 shoulder, 169 elbow) in 1,554,708 AEs. After excluding injuries sustained by other mechanisms (Figure 1), there were 295 shoulder and elbow injuries (164 shoulder, 131 elbow), for a shoulder injury rate of 1.04 per 10,000 AEs and an elbow injury rate of 0.86 per 10,000 AEs. Comparing 3 seasons prior (school years 2013-2014 through 2015-2016) to 3 seasons after (school years 2016-2017 through 2018-2019) the NFHS PR policy mandate, rates for total shoulder and elbow injuries were not significantly different pre- versus post-PR policy mandate (1.93 vs 1.86 per 10,000 AEs; IRR, 1.03; 95% CI, 0.82-1.31; P = .78) (Table 1). Similarly, shoulder injury rates were not significantly different before the NFHS PR policy mandate (1.06 vs 1.01 per 10,000 AEs; IRR, 1.05; 95% CI, 0.76-1.45; P = .77), nor were elbow injury rates (0.87 vs 0.85 per 10,000 AEs; IRR, 1.02; 95% CI, 0.72-1.46; P = .92). Shoulder and elbow injury rate trends during the 6-season data collection period are illustrated in Figure 2. The overall total shoulder and elbow, shoulder, and elbow injury rates did not show significant trends over time from 2013-2014 to 2018-2019.

Table 1.

Total Shoulder and Elbow Injury Rates, 2013-2014 Through 2018-2019 School Years ^a

School Years	Total Shoulder and Elbow			Total Shoulder			Total Elbow
	Injuries, n	AEs, n	Rate per 10,000 AEs	Injuries, n	AEs, n	Rate per 10,000 AEs	Injuries, n	AEs, n	Rate per 10,000 AEs
2013-2014	60	305,925	1.96	36	305,925	1.18	24	305,925	0.78
2014-2015	56	286,729	1.95	30	286,729	1.05	26	286,729	0.91
2015-2016	48	258,797	1.85	24	258,797	0.93	24	258,797	0.93
2013-2014 through 2015-2016	164	851,451	1.93	90	851,451	1.06	74	851,451	0.87
2016-2017	36	221,948	1.62	18	221,948	0.81	18	221,948	0.81
2017-2018	52	239,316	2.17	28	239,316	1.17	24	239,316	1.00
2018-2019	43	241,993	1.78	25	241,993	1.03	18	241,993	0.74
2016-2017 through 2018-2019	131	703,257	1.86	71	703,257	1.01	60	703,257	0.85

^aThe mandated nationwide National Federation of State High School Associations pitching restriction policy was implemented in 2016. AE, athlete-exposure.

Figure 2.

Shoulder and elbow injury rates, US high school baseball players, 2013-2014 through 2018-2019. Total shoulder and elbow injuries (P = .97), shoulder injuries (P = .71), elbow injuries (P = .48). AE, athlete-exposure; NFHS, National Federation of State High School Associations.

Injury Characteristics: All Players, Pitcher Versus Position Players

Characteristics of shoulder and elbow injuries in all players are presented in Table 2. Most injuries to the shoulder (83.2%) and elbow (86.6%) were new. Most shoulder injuries were muscle strains (47.2%), whereas most elbow injuries were ligament sprains (40.3%). The proportion of shoulder (5.0%) and elbow (3.7%) injuries treated surgically did not differ significantly (injury proportion ratio [IPR], 1.33; 95% CI, 0.38-5.17). Pitching and throwing injuries comprised 93.2% of shoulder injuries and 97.8% of elbow injuries in all players, and the proportion of shoulder and elbow injuries due to pitching or throwing activity did not differ significantly. As pitchers sustained the highest proportion of shoulder (52.2%) and elbow (55.2%) injuries compared with other position players, further analysis was performed to compare shoulder and elbow injuries among pitchers and position players (Supplemental Table S1). Left-hand dominance being more prevalent in pitchers (IPR, 3.27; 95% CI, 1.31-9.75) and injuries requiring time loss <1 week being more prevalent among position players (IPR, 0.64; 95% CI, 0.41-0.99) were the most notable significant differences among these subgroups.

Table 2.

Characteristics of Shoulder and Elbow Injuries in All Players ^a

Characteristic	Shoulder (n = 161)	Elbow (n = 134)	IPR (95% CI) b
Side of body
Right	141 (87.6)	118 (88.1)	0.99 (0.77-1.28)
Left	20 (12.4)	14 (10.4)	1.19 (0.57-2.54)
Missing data	—	2 (1.5)	—
New injury or recurrence
New injury	134 (83.2)	116 (86.6)	0.96 (0.74-1.24)
Recurrence (this sport season) c	3 (1.9)	1 (0.7)	—
Recurrence (this sport season, non-HS sanctioned sport) c	1 (0.6)	1 (0.7)	—
Recurrence (this academic year)	5 (3.1)	2 (1.5)	2.08 (0.34-21.85)
Recurrence (prior academic year)	16 (9.9)	11 (8.2)	1.21 (0.53-2.89)
Other	—	3 (2.2)	—
Missing data	2 (1.2)	—	—
Position
Pitcher	84 (52.2)	74 (55.2)	0.94 (0.68-1.31)
Outfielder	23 (14.3)	18 (13.4)	1.06 (0.55-2.09)
Infielder	23 (14.3)	20 (14.9)	0.96 (0.50-1.83)
Catcher	21 (13.0)	17 (12.7)	1.03 (0.52-2.08)
Other/unknown	5 (3.1)	1 (0.7)	—
Missing data	5 (3.1)	4 (3.0)	1.04 (0.22-5.24)
Time loss
<1 wk	62 (38.5)	31 (23.1)	1.66 (1.07-2.65)
1-3 wk	60 (37.3)	51 (38.1)	0.98 (0.66-1.45)
>3 wk	14 (8.7)	16 (11.9)	0.73 (0.33-1.59)
Medical disqualification	4 (2.5)	10 (7.5)	0.33 (0.08-1.15)
Other d	16 (9.9)	21 (15.7)	0.63 (0.31-1.28)
Missing data	5 (3.1)	5 (3.7)	0.83 (0.19-3.62)
Surgery
Yes	8 (5.0)	5 (3.7)	1.33 (0.38-5.17)
No	152 (94.4)	129 (96.3)	0.98 (0.77-1.25)
Missing data	1 (0.6)	—	—
Injury mechanism e
Pitching	82 (50.9)	73 (54.5)	0.93 (0.67-1.30)
Throwing	68 (42.2)	58 (43.3)	0.98 (0.68-1.41)
Fielding	1 (0.6)	1 (0.7)	—
Catching	—	—	—
General play	3 (1.9)	—	—
Conditioning	2 (1.2)	—	—
Other	5 (3.1)	2 (1.5)	2.08 (0.34-21.85)
Diagnosis
Muscle strain	76 (47.2)	17 (12.7)	3.72 (2.18-6.72)
Tendinitis	39 (24.2)	27 (20.1)	1.20 (0.72-2.04)
Ligament sprain	7 (4.3)	54 (40.3)	0.11 (0.04-0.24)
Other	15 (9.3)	8 (6.0)	1.56 (0.62-4.25)
Tendon strain	9 (5.6)	7 (5.2)	1.07 (0.35-3.38)
Torn cartilage	6 (3.7)	—	—
Nerve injury	2 (1.2)	7 (5.2)	0.24 (0.02-1.25)
Fracture	1 (0.6)	6 (4.5)	—
Stress fracture	1 (0.6)	2 (1.5)	—
Apophysitis	—	3 (2.2)	—
Subluxation	2 (1.2)	—	—
Bursitis	1 (0.6)	1 (0.7)	—
Contusion	—	1 (0.7)	—
Avulsion	—	1 (0.7)	—
Dislocation	1 (0.6)	—	—
Missing data	1 (0.6)	—	—

^aData are expressed as n (%). Values in bold are statistically significant. Categories with ≤1 case count were not evaluated for significance. HS, high school; IPR, injury proportion ratio. Dashes indicate not applicable.

^bThe elbow is the reference for all IPRs.

^cThese recurrent injury subcategories were added by High School Reporting Information Online (HS RIO) in 2015-2016.

^dOther includes the athlete choosing not to continue or the season ending before the athlete could return.

^eCategorized by baseball-specific activity, per HS RIO Codebook 2023-2024.

Comparison of Injury Rates: School Years With Versus Without a PR Policy

As several states implemented PR policies before and after the 2016 NFHS mandate, an analysis of injury rates in school years with and without PR policies was also conducted (Table 3). Rates of practice shoulder and elbow injuries (combined) (IRR, 1.73; 95% CI, 1.07-2.94), total (practice and competition) elbow injuries (IRR, 1.78; 95% CI, 1.02-3.35), and practice elbow injuries (IRR, 2.35; 95% CI, 1.03-6.63) were significantly higher in seasons during which PR policies were in effect compared with seasons when PR policies were not in effect.

Table 3.

PR Policy (In Effect, Not in Effect), School Years 2013-2014 to 2018-2019 ^a

Injury	Exposure Type	PR Policy in Effect			PR Policy Not in Effect			IRR	95% CI	P Value
		Injuries, n	AEs, n	Injury Rate/ 10,000 AEs	Injuries, n	AEs, n	Injury Rate/ 10,000 AEs
Shoulder and elbow	Practice	158	833,709	1.90	19	173,040	1.10	1.73	1.07-2.94	.02
	Competition	97	453,880	2.14	21	94,079	2.23	0.96	0.59-1.62	.84
	Total	255	1,287,589	1.98	40	267,119	1.50	1.32	0.94-1.90	.09
Shoulder	Practice	90	833,709	1.08	13	173,040	0.75	1.44	0.80-2.80	.22
	Competition	45	453,880	0.99	13	94,079	1.38	0.72	0.38-1.45	.30
	Total	135	1,287,589	1.05	26	267,119	0.97	1.08	0.70-1.71	.75
Elbow	Practice	68	833,709	0.82	6	173,040	0.35	2.35	1.03-6.63	.03
	Competition	52	453,880	1.15	8	94,079	0.85	1.35	0.64-3.28	.45
	Total	120	1,287,589	0.93	14	267,119	0.52	1.78	1.02-3.35	.03

^aValues in bold are statistically significant. AE, athlete-exposure; PR, pitching restriction.

Comparison of Injury Rates: Participation Restriction Time, Medical Disqualification, and Surgical Treatment

Shoulder and elbow injuries (combined), shoulder injuries, and elbow injuries sustained in both practice and competition that required >21 days away from sport, medical disqualification (MDQ), and surgical treatment were compared 3 school years before and after the 2016 NFHS mandate (Supplemental Tables S2-S4). While the relative rate ratios comparing combined shoulder and elbow injuries, shoulder injuries, and elbow injuries pre- and post-mandate were not statistically significant for time loss >21 days, injuries requiring MDQ, or surgical treatment, the number of MDQ injuries was overall quite small and likely underpowered.

Comparison of Injury Rates: Specific Rule Distinctions

For total exposures (Figure 3), the presence of a consecutive pitching day rest rule was associated with the most significant reduction in injury rate ratio (IRR) for combined shoulder and elbow (IRR, 0.32; 95% CI, 0.22-0.46; P < .0001), shoulder (IRR, 0.33; 95% CI, 0.19-0.54; P < .0001), and elbow (IRR, 0.31; 95% CI, 0.17-0.54; P < .0001) injuries. Daily maximum pitch count of ≤105 pitches provided a protective effect compared with maximum daily pitch counts >105 pitches with regard to combined shoulder and elbow (IRR, 0.40; 95% CI, 0.31-0.51; P < .0001), shoulder (IRR, 0.35; 95% CI, 0.24-0.49; P < .0001), and elbow (IRR, 0.46; 95% CI, 0.32-0.67; P < .0001) injuries. Having different PR policy rules for regular versus postseason was also associated with a significant injury reduction for combined shoulder and elbow (IRR, 0.43; 95% CI, 0.27-0.65; P < .0001), shoulder (IRR, 0.41; 95% CI, 0.21-0.72; P < .001), and elbow (IRR, 0.45; 95% CI, 0.23-0.82; P = .004) injuries. Different pitch count maximums for varsity versus subvarsity provided a protective effect against combined shoulder and elbow (IRR, 0.46; 95% CI, 0.35-0.59; P < .0001), shoulder (IRR, 0.51; 95% CI, 0.36-0.71; P < .0001), and elbow (IRR, 0.41; 95% CI, 0.27-0.60; P < .0001) injuries. Four days’ rest if >105 daily pitch count was a rule distinction that was also particularly effective, with significant reductions in combined shoulder and elbow (IRR, 0.53; 95% CI, 0.42-0.68; P < .0001), shoulder (IRR, 0.57; 95% CI, 0.41-0.79; P < .001), and elbow (IRR, 0.50; 95% CI, 0.34-0.72; P < .0001) injuries.

Figure 3.

Injury rate ratios (IRRs) for specific pitching restriction (PR) policy rule distinctions, total (practice and competition) exposures. (A) Combined shoulder and elbow injuries. (B) Shoulder injuries. (C) Elbow injuries. PR policy rule distinctions are ordered on the y-axis from lowest to greatest IRR, in descending order.

For practice exposures (Figure 4), different pitch count maximums for varsity versus subvarsity was associated with significant reductions in IRR for combined shoulder and elbow (IRR, 0.33; 95% CI, 0.23-0.48; P < .0001), shoulder (IRR, 0.37; 95% CI, 0.23-0.58; P < .0001), and elbow (IRR, 0.29; 95% CI, 0.15-0.51; P < .0001) injuries. The presence of a consecutive pitching day rest rule provided a protective effect against combined shoulder and elbow (IRR, 0.34; 95% CI, 0.21-0.53; P < .0001), shoulder (IRR, 0.35; 95% CI, 0.18-0.62; P = .0001), and elbow (IRR, 0.33; 95% CI, 0.15-0.67; P < .001) injuries. Daily maximum pitch count of ≤105 pitches provided a protective effect for HS baseball players compared with maximum daily pitch counts >105 pitches regarding combined shoulder and elbow (IRR, 0.37; 95% CI, 0.26-0.51; P < .0001), shoulder (IRR, 0.34; 95% CI, 0.21-0.53; P < .0001), and elbow (IRR, 0.40; 95% CI, 0.23-0.68; P = .0002) injuries. Four days’ rest if >105 daily pitch count was a rule distinction that was also particularly effective, with significant reductions in combined shoulder and elbow (IRR, 0.46; 95% CI, 0.33-0.64; P < .0001), shoulder (IRR, 0.48; 95% CI, 0.31-0.73; P < .001), and elbow (IRR, 0.44; 95% CI, 0.26-0.73; P < .001) injuries.

Figure 4.

Injury rate ratios (IRRs) for specific pitching restriction (PR) policy rule distinctions, practice exposures. (A) Combined shoulder and elbow injuries. (B) Shoulder injuries. (C) Elbow injuries. PR policy rule distinctions are ordered on the y-axis from lowest to greatest IRR, in descending order.

For competition exposures (Figure 5), the presence of a consecutive pitching day rest rule was associated with a significant IRR reduction for combined shoulder and elbow (IRR, 0.30; 95% CI, 0.15-0.55; P < .0001), shoulder (IRR, 0.31; 95% CI, 0.11-0.71; P = .002), and elbow (IRR, 0.29; 95% CI 0.10-0.68; P = .0012) injuries. Daily maximum pitch count of ≤105 pitches provided a protective effect compared with maximum daily pitch counts >105 for combined shoulder and elbow (IRR, 0.45; 95% CI, 0.29-0.66; P < .0001), shoulder (IRR, 0.36; 95% CI, 0.19-0.65; P = .0002), and elbow (IRR, 0.54; 95% CI, 0.31-0.94; P = .02) injuries. Having different PR policy rules for regular versus postseason also was associated with a significant injury reduction for combined shoulder and elbow (IRR, 0.39; 95% CI, 0.17-0.76; P = .002) and shoulder (IRR, 0.17; 95% CI, 0.02-0.63; P = .001) injuries, but not elbow (IRR, 0.62; 95% CI, 0.24-1.37; P = .23) injuries.

Figure 5.

Injury rate ratios (IRRs) for specific pitching restriction (PR) policy rule distinctions, competition exposures. (A) Combined shoulder and elbow injuries. (B) Shoulder injuries. (C) Elbow injuries. PR policy rule distinctions are ordered on the y-axis from lowest to greatest IRR, in descending order.

Discussion

This study sought to determine whether (1) a national PR policy mandate reduced shoulder and elbow injuries in US HS baseball players and (2) specific components of PR policies were associated with a reduction in shoulder and elbow injuries among this population. Collectively, shoulder and elbow injury rates were not statistically higher in the 3 seasons before compared with the 3 seasons after the 2016 NFHS PR policy mandate. Shoulder- and elbow-specific injury rates were similarly not statistically higher in the 3 seasons before compared with the 3 seasons after the 2016 NFHS PR policy mandate. When analyzing injury rates for total exposures (practices and competitions) collectively, consecutive pitching day rest rules (IRR, 0.32; 95% CI, 0.22-0.46), ≤105 pitch daily maximum (IRR, 0.40; 95% CI, 0.31-0.51), different PR policy rules for regular versus postseason (IRR, 0.43; 95% CI, 0.27-0.65), varsity versus subvarsity pitch count maximums (IRR, 0.46; 95% CI, 0.35-0.59), and ≥4 days’ rest if >105 pitch count (IRR, 0.53; 95% CI, 0.42-0.68) provided statistically significant protective effects against shoulder and elbow injuries compared with PR policies without these components.

An unexpected finding was that significantly higher rates of practice shoulder and elbow, total (practice and competition) elbow, and practice elbow injuries were identified during school years when PR policies were in effect compared with school years when PR policies were not in effect. Plausible explanations for these results include 1) other extrinsic risk factors for shoulder and elbow injuries, including but not limited to trends in training (eg, year-round high-volume, high-intensity throwing with limited periods of rest/recovery), velocity programs among pitchers and position players, increasing rates of early sport specialization, and “pitcher only” designation among amateur baseball players as outlined in Major League Baseball’s recent Report on Pitcher Injuries ²⁰ ; 2) continuation of decades-long trends of increasing elbow injuries in HS baseball players^10,25; 3) noncompliance with PR policies among HS players and coaches ⁷ ; 4) lack of enforcement of PR policies among individual NFHS member states; 5) injuries occurring in states with PR policies in effect but containing components that potentially increase rather than reduce injury risk (eg, allowing a maximum of 140 pitches in a 4-day span without a specific rest day requirement and eliminating pitch limits altogether in the postseason) ¹⁹ ; and 6) the possibility that PR policies are too lenient, an assertion postulated by Mair et al ¹⁸ in a study examining the effect of different PR rules on the number of pitches thrown by 179 youth baseball pitchers aged 9 to 12 years in 3 leagues in Lexington, Kentucky, during the 2012 and 2013 seasons. The authors determined that despite following league PRs, 37% of pitchers exceeded 600 pitches per season in only the 10 weeks studied in these leagues (the 600-pitch count threshold was chosen based on previous research identifying >600 pitches in a season as a risk factor for elbow pain in youth baseball pitchers^15,16).

Worth mentioning in Figures 3 to 5 are the data plots for rule violation and PR policy. In nearly all the figures, these 2 rule distinctions had IRRs >1.0, and in the case of rule violation, the IRRs were frequently >1.5, which could be interpreted as an increased injury rate for each of these specific rule distinctions. However, in comparison to the other specific rule distinctions, both rule violation policy and PR policy data plots demonstrate wide confidence intervals throughout the figures. Wide confidence intervals indicate imprecise estimates and high uncertainty about the true population parameter. Common causes include small sample size and inconsistent data. ¹¹ Interpretation of these results with wide confidence intervals should be done with caution due to the high level of uncertainty about the exact value of the IRR.

While PR policies in amateur baseball have been implemented since the mid- to late 1990s, ²⁹ there is a paucity of peer-reviewed scientific literature demonstrating an association between PR policies and reduced injury rates in adolescent baseball players. ²² Norton et al ²² performed a systematic review of published literature (1990-2016) that identified 22 articles and 19 independent risk factors for elbow and shoulder injuries in adolescent baseball players. Among USA Baseball/PSG PR policy components, pitches per game (a significant risk factor for shoulder pain but not elbow pain), arm fatigue, and pitching for multiple teams were identified as clear risk factors for throwing arm injuries in adolescent players. Of these, only pitch count limits are enforced by NFHS member states for HS baseball, and notable variability in current HS pitch count rules continues to exist that deviate from USA Baseball/PSG. ¹⁹ Numerous author groups have called for standardization and enforcement of PR policies in both NFHS-affiliated and non-HS baseball competition (eg, tournaments and showcases), improved systems to monitor HS pitching workloads, and future research to better understand relationships between PR policy components and injury risk.^{1,7,19,22,29,30}

Other authors have investigated whether injury prevention policies versus their individual components are effective in reducing injury rates in adolescent sports. Soomro et al ²⁷ conducted a systematic review of injury prevention programs (IPPs) in adolescent team sports to determine whether programs incorporating a combination of warm-up, neuromuscular strength, and/or proprioception training effectively reduced injury rates. Across 10 studies, including 9 randomized controlled trials, a pooled overall point estimate yielded an IRR of 0.60 (95% CI, 0.48-0.75), a significant and clinically meaningful reduction in injury rates. ²⁷ The authors summarized that isolating the underlying explanations of IPP efficacy and benefits from specific factors is challenging, although they suggested that efficacy is likely associated with particular IPP components, sport context and performance requirements, or both. As a result of this landmark study, a reduction of 40% in injury rate (eg, IRR ≤0.60) is generally considered a substantial improvement in safety and an effective injury prevention strategy.

In line with the work of Soomro et al, ²⁷ we found that specific components of PR policies rather than a national PR policy mandate are associated with significant reduction in shoulder and elbow injury rates in HS baseball players. Specifically, the presence of a consecutive pitching day rest rule and daily maximum pitch count of ≤105 pitches were associated with significant reductions in shoulder and elbow injuries based on total (practice and competition) exposures (Figure 3A), practice exposures (Figure 4A), and competition exposures (Figure 5A) when IRR ≤0.60 and other inferential statistical measures of significance (eg, 95% confidence intervals and P value) were applied. When we evaluated specific components of PSG for 17- to 18-year-old athletes (maximum daily pitch count 105 pitches, 4 days’ rest if >105 daily pitch count, no more than 2 consecutive days of pitching, and different maximum daily pitch counts for 17- to 18-year-olds vs 15- to 16-year-olds), daily maximum pitch count of ≤105 pitches and 4 days’ rest if >105 daily pitch count components were collectively associated with significant reductions in shoulder and elbow injuries based on total (practice and competition) exposures (Figure 3A) and practice exposures (Figure 4). Unfortunately, the PSG consecutive day pitching rule could not be evaluated as consecutive day pitching rules varied among NFHS member states, with 5 states having consecutive day pitching rules but permitting pitching on >2 consecutive days (Illinois, New Mexico, Virginia, and West Virginia allow 3 consecutive days’ pitching; Nevada allows 4 consecutive days’ pitching). Similarly, while different pitch count maximums for varsity versus subvarsity was a PR policy component assessed in this study, only 23 (48%) of 48 states had different pitch count maximums for varsity versus subvarsity (eg, JV/freshman), and PSG-specific pitch count maximums (eg, 105 pitches for 17- to 18-year-olds and 95 pitches for 15- to 16-year-olds) were adopted by only 5 states (Arizona, Florida, Illinois, Maryland, and Missouri).

Our study results build on the work of Manzi et al, ¹⁹ assessing the variability and effectiveness of PR policies of NFHS member states using retrospective injury and AE data rather than a simulated, theoretical model to determine the effect of pitch count rules and rest days, in addition to other frequently utilized PR policy components. While a prospective survey study involving US HS pitchers conducted by Erickson et al ⁷ has shown that most players are not fully compliant with PSG during the HS season, noncompliance was most common with components of PSG other than pitch counts and days of rest, including playing for multiple teams at the same time (65% of players), not taking at least 3 consecutive months off from overhead throwing of a baseball each year (67% of players), and pitchers also playing catcher (12% of players). While 14% (9/63) HS pitchers surveyed reported at least 1 violation of pitch counts within the PSG when in-game pitch count data collected during the season were examined, it is quite possible that these HS pitchers participated in HS baseball in NFHS member states that did not adopt PSG pitch count maximums.

Limitations

Limitations of this study include likely underestimation of true injury burden (including minor injuries not resulting in time loss as well as major injuries ultimately treated surgically) due to a number of factors. Some are related to restrictions of the surveillance system (HS RIO). First, only HSs with ATs who chose to participate in surveillance programs were included in the random sample. Second, non–time loss injuries were not reported. Third, no injury diagnostic criteria were reported to HS RIO. Fourth, the HS RIO database is suboptimal for collecting diagnostic imaging results and assessing surgical risk and/or outcomes. Fifth, HS RIO does not collect injury or exposure data from HS-level baseball leagues, tournaments, or showcases other than NFHS-sanctioned baseball play involving school affiliated teams. Therefore, injuries from practices and competitions related to competitive club/travel baseball or select/invitational teams are not included in the HS RIO database. Sixth, HS RIO does not collect data on healthy, uninjured participants (other than AE data), so generating dependent variables requiring data from uninjured participants for use in multivariable comparisons in the context of this study and its objectives was not feasible. Consequently, this study’s univariate analysis cannot account for confounding variables, nor can a statistical relationship between several of the independent variables (ie, specific rule distinctions) be identified. Other limitations not inherent to the HS RIO database include the observational, retrospective nature of the study design, which inhibits confirmation of player, coach, and NFHS member state compliance with PR policies. Despite these limitations, this study provided a unique opportunity to investigate the association between shoulder and elbow injuries and PR policies among US HS baseball players using a large national database.

Conclusion

Specific components of PR policies rather than a national PR policy mandate were associated with significant reduction in shoulder and elbow injury rates in HS baseball players. The presence of a consecutive pitching day rest rule and daily maximum pitch count of ≤105 pitches were associated with significant reductions in shoulder and elbow injuries based on total (practice and competition) exposures, practice exposures, and competition exposures. While high-quality prospective studies are needed in this population, both NFHS-affiliated and non-HS baseball organizations should consider uniform adoption of these 2 PR policy components until such research to better understand relationships between PR policy components and injury risk can be conducted.