Systematic Review of Clinical and Performance Outcome Measures Reported for
     Softball Pitchers

Katie Sloma; Kaila Holtz; Lauren Butler; Jessica Downs Talmage; Nicole Bordelon; Sophia Ulman; Gretchen Oliver

doi:10.1055/a-2713-7372

International Journal of Sports Medicine, Inhaltsverzeichnis

Int J Sports Med
DOI: 10.1055/a-2713-7372

Review

Systematic Review of Clinical and Performance Outcome Measures Reported for Softball Pitchers

Autor*innen

Katie Sloma

¹Center for Excellence in Sports Medicine, Scottish Rite for Children, Frisco, United States
Kaila Holtz

²The University of British Columbia Faculty of Medicine, Vancouver, Canada (Ringgold ID: RIN12358)
Lauren Butler

³Physical Therapy, Florida International University, Miami, United States (Ringgold ID: RIN5450)
Jessica Downs Talmage

⁴Sport Sciences, Northern State University, Aberdeen, United States (Ringgold ID: RIN27714)
Nicole Bordelon

⁴Sport Sciences, Northern State University, Aberdeen, United States (Ringgold ID: RIN27714)
Sophia Ulman

¹Center for Excellence in Sports Medicine, Scottish Rite for Children, Frisco, United States

⁶Department of Orthopaedic Surgery, The University of Texas Southwestern Medical Center, Dallas, United States (Ringgold ID: RIN12334)
Gretchen Oliver

⁶Department of Orthopaedic Surgery, The University of Texas Southwestern Medical Center, Dallas, United States (Ringgold ID: RIN12334)

Abstract

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Keywords

Softball Pitching - Clinical Outcomes - Functional Outcomes - Clinical Assessment - Functional Assessment

Introduction

Softball is recognized as one of the top five most popular sports among youth and adults in the United States.[1] Despite the growing popularity, research efforts have historically focused on baseball athletes.[1] However, in recent years, there has been a steady rise in softball research aimed at addressing the increasing incidence of injuries, particularly among pitchers.[1–] [2] [] [4]

Softball pitching requires coordination of the entire kinetic chain to optimize performance and minimize stress on the throwing arm.[5] [6] [7] This population is especially vulnerable to shoulder overuse injuries, which are partially attributed to the repetitive nature of the pitch and the high stress placed on the long head of the biceps tendon near ball release.[6] [7] Emerging evidence suggests that clinical outcomes such as altered range of motion (ROM), muscular weakness, lumbopelvic–hip complex instability, and anthropometrics[8] [9] are associated with increased shoulder stress and upper extremity pain in softball athletes.[10] [11] Consequently, it is theorized that these factors may elevate the risk of overuse injuries in softball pitchers.

Traditionally, recommendations for injury prevention and management in softball pitchers have been adapted from the baseball literature. However, recent data indicate that collegiate softball players generally experience nearly twice the number of injuries compared to their baseball counterparts.[2] Additionally, softball athletes are more prone to shoulder overuse injuries, whereas baseball players tend to sustain more elbow overuse injuries.[4] Given the differences in injury rates, injury locations, and pitching mechanics between the two sports, it is reasonable to suggest that clinical assessment protocols and prevention strategies should be tailored to each sport.[12]

Overall, there is a clear need to integrate the expanding body of research on clinical outcomes in softball pitching into practical recommendations for a range of clinicians and sport medicine professionals including physicians, physical therapists, athletic trainers, coaches, and strength and conditioning specialists. Therefore, this systematic review aims to synthesize the existing literature on clinical and performance outcome measures in softball pitchers.

Methods

Study design

The aim of this systematic review was to evaluate the clinical and performance outcome measures reported in softball pitchers in the existing literature using the PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) for systematic reviews.[13]

Search strategy

A search of PubMed, Embase, CINAHL and SPORTDiscus databases was conducted on December 3, 2024, to identify all softball pitching studies reporting clinical and performance outcomes. Search terms included “softball” AND “pitching” OR “injuries”.

Identification of relevant studies

Authors (K. H. and K. S.) independently reviewed abstracts using Covidence Systematic Review Software, Veritas Health Innovation, Melbourne, Australia. www.covidence.org. All duplicates were removed.

Abstracts were excluded if they (1) did not report softball pitchers, (2) reported outcomes of other sports pooled with softball pitching, (3) were review articles, or (4) were expert opinions only. Podium presentations or abstracts were not included.

Study selection

Full-text articles were read by all authors. Articles were included if they were published in peer-reviewed journals and reported clinical or performance outcomes like strength, ROM, anthropometrics, and patient-reported measures.

Final determination of inclusion/exclusion decisions was resolved by a third reviewer, S.O.

Risk of bias

Risk of bias and methodological quality were assessed for all included studies using the Joanna Briggs Institute Critical Appraisal Checklist for cross sectional studies.[14]

Results

Search results

The initial search of all databases identified 1,963 articles and 7 articles were identified from citation searching. After removing 326 duplicates, 1,637 articles were screened and included/ excluded based on criteria. Fifty-seven studies were assessed for eligibility. Four were removed as they reported non-softball pitching outcomes, and 10 were removed due to the wrong patient population (i.e., not softball pitchers). Five citations were podium presentations of case studies. A total of 37 peer-reviewed studies were included in this systematic review ([Fig. 1] [Table 1]).

Fig. 1 Preferred Reporting Items for Systematic Reviews and Meta-Analyses flowchart.[13]

Table 1 Summary of studies included in this systematic review
Authors	Study design	Primary outcome variables	Status	Subject groups
Friesen et al.[8]	Cross-sectional	Hip ROM	Healthy	Healthy pitchers divided into BMI categories.
Friesen et al.[8]	N=147	Shoulder ROM	Healthy	Healthy pitchers divided into BMI categories.
Friesen et al.[9]	Cross-sectional	Hip isometric strength	Healthy	Healthy high school pitchers and high vs. low body fat percentage groups.
	N=41	Shoulder isometric strength
		ROM
		Arm bone and lean mass
Czeck et al.[14]	Cross-sectional	Regional and total mass, fat mass, lean mass, and bone mineral content.	Healthy	Healthy pitchers (N=32).
Czeck et al.[14]	N=128		Healthy	Healthy pitchers (N=32).
Peart et al.[15]	Prospective cohort	Total body mass, lean body mass, fat mass, and body fat percentage	Healthy	NCAA Division I collegiate softball athletes.
Peart et al.[15]	N=42		Healthy	NCAA Division I collegiate softball athletes.
Friesen et al.[16]	Cross-sectional	Shoulder and hip ROM	Healthy	Youth softball athletes, N=29 pitchers.
Friesen et al.[16]	N=52	Shoulder and hip ROM	Healthy	Youth softball athletes, N=29 pitchers.
West et al.[17]	Cross-sectional	Shoulder, elbow, and hip strength and ROM	Healthy	High school pitchers (N=24) and collegiate pitchers (N=9).
West et al.[17]	N=33	Shoulder, elbow, and hip strength and ROM	Healthy	High school pitchers (N=24) and collegiate pitchers (N=9).
Guy et al.[18]	Prospective cohort	Shoulder and hip ROM and strength	Healthy	College softball pitchers and position players.
Guy et al.[18]	N=54	Shoulder and hip ROM and strength	Healthy	College softball pitchers and position players.
Shanley et al.[19]	Prospective Cohort	Shoulder ROM	Healthy	High school softball pitchers.
Shanley et al.[19]	N=12	Injury rates	Healthy	High school softball pitchers.
Oliver et al.[20]	Prospective Cohort	Shoulder and hip ROM	Healthy	Collegiate pitchers.
Oliver et al.[20]	N=49	Shoulder and hip ROM	Healthy	Collegiate pitchers.
Talmage et al.[21]	Cross-sectional	Shoulder and hip ROM	Healthy	High school pitchers.
Talmage et al.[21]	N=30	Shoulder and hip ROM	Healthy	High school pitchers.
Oliver et al.[22]	Cross-sectional	Shoulder and hip ROM	Healthy	Collegiate softball pitchers.
	N=5	Shoulder and hip isometric strength
	N=5	Vertical jump height
Yang et al.[23]	Prospective Cross-sectional	Shoulder and elbow strength	Healthy	High school fast-pitch softball pitchers.
	N=17	Shoulder and elbow ROM		Tested pre- and post-game, once at the beginning of the season, and once at the end.
	N=17	Pain and fatigue
Oliver et al.[10]	Cross-sectional	Shoulder and hip ROM and strength	Pain vs. no pain	NCAA Division I softball pitchers.
Oliver et al.[10]	N=53	Shoulder and hip ROM and strength	Pain vs. no pain	NCAA Division I softball pitchers.
Oliver et al.[24]	Cross-sectional	Hip ROM	Healthy	Youth softball pitchers.
	N=29	Hip isometric strength
	N=29	Pitching biomechanics
Verhey et al.[25]	Case series	MRI	Ulnar shaft stress fracture	Fastpitch softball pitchers aged 12–17 y.
Verhey et al.[25]	N=4	Radiographs	Ulnar shaft stress fracture	Fastpitch softball pitchers aged 12–17 y.
Wiltfong et al.[26]	Case study	Radiographs	Ulnar shaft stress fracture	An 18-y-old fastpitch softball pitcher.
Wiltfong et al.[26]	N=1	Radiographs	Ulnar shaft stress fracture	An 18-y-old fastpitch softball pitcher.
Fujioka et al.[27]	Case study	Radiographs	Ulnar stress fracture	A 13-y-old fastpitch softball pitcher.
Fujioka et al.[27]	N=1	Radiographs	Ulnar stress fracture	A 13-y-old fastpitch softball pitcher.
Smith et al.[28]	Case series	MRI	Medial elbow pain and ulnar digit paresthesia	Softball pitchers who underwent ulnar nerve transposition.
Smith et al.[28]	N=6	MRI	Medial elbow pain and ulnar digit paresthesia	Softball pitchers who underwent ulnar nerve transposition.
Jenkins et al.[29]	Case study	Radiographs	Intramuscular Angioma	A 16-y-old softball pitcher.
Jenkins et al.[29]	N=1	MRI	Intramuscular Angioma	A 16-y-old softball pitcher.
Kotob et al.[30]	Case study	Radiographs MRI	Coracoid Apophysiolysis	An 11-y-old softball pitcher.
Kotob et al.[30]	N=1	Radiographs MRI	Coracoid Apophysiolysis	An 11-y-old softball pitcher.
Jowett et al.[31]	Case study	Radioisotope scan	Fifth metacarpal stress fracture	A female softball pitcher.
Jowett et al.[31]	N=1	Radioisotope scan	Fifth metacarpal stress fracture	A female softball pitcher.
Ferry et al.[32]	Case study	MRI	Long-head of biceps tendon rupture	A 24-year-old professional softball pitcher.
Ferry et al.[32]	N=1	MRI	Long-head of biceps tendon rupture	A 24-year-old professional softball pitcher.
DeFranco et al.[33]	Case study	MRI	Isolated musculocutaneus nerve injury	A 30-year-old professional fast-pitch softball pitcher.
DeFranco et al.[33]	N=1	Electromyography (EMG)	Isolated musculocutaneus nerve injury	A 30-year-old professional fast-pitch softball pitcher.
Rothermich et al.[34]	Retrospective cohort	American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form score	47 fast-pitch softball players treated surgically for SLAP tear, recalcitrant biceps tendonitis, or a combination with greater than 2-year follow-up.
	N=47	Andrews Carson Score		Superior labrum anterior posterior (SLAP) tear and recalcitrant biceps tendonitis
		Kerlan-Jobe Orthopaedic Clinic Shoulder and Elbow Score
		Numeric Rating Scale for Pain
		Return-to-play questionnaire
Pfefferle et al.[36]	Case study	Radiographs	Rib stress fracture	A 21-year-old collegiate softball pitcher.
Pfefferle et al.[36]	N=1	Radiographs	Rib stress fracture	A 21-year-old collegiate softball pitcher.
Oliver et al.[37]	Cross-sectional	Bicep tendon thickness, width, and an area on the dominant arm measured with ultrasound	Healthy	Youth softball pitchers.
	N=23	Trunk and lower extremity kinematics		Measured pre- and post-simulated game.
	N=23	Shoulder kinetics pitch speed		Measured pre- and post-simulated game.
Barfield et al.[38]	Cross-sectional	Long-head biceps tendon (LHBT) longitudinal thickness and transverse width/thickness measured with ultrasound	Healthy	Softball pitchers.
Barfield et al.[38]	N=19		Healthy	Measured pre- and post-simulated game.
Skoumal et al.[39]	Case report	Manual muscle testing (MMT)	Scapular dyskinesis	A youth softball pitcher
Skoumal et al.[39]	N=1	Manual muscle testing (MMT)	Scapular dyskinesis	A youth softball pitcher
Corben et al.[40]	Cross-sectional	Forearm, elbow, shoulder, scapula, and hip strength	Healthy	Youth softball pitchers.
Corben et al.[40]	N=19	Fatigue	Healthy	Tested before and after pitching a game.
Stamm et al.[41]	Systematic review	Shoulder ROM	Biceps tendon injuries	536 softball players (average age of 14–25 y).
Stamm et al.[41]	N=536	Shoulder strength	Biceps tendon injuries	536 softball players (average age of 14–25 y).
Pletcher et al.[42]	Cross-sectional	Isokinetic strength for the knee, hip, trunk, pitching elbow flexion and extension, and trunk rotation	Healthy	Fourteen softball pitchers.
Pletcher et al.[42]	N=14		Healthy	Tested before and after pitching a simulated game.
Skillington et al.[43]	Cross-sectional	Should and elbow strength	Healthy	Softball pitchers between the ages of 14 and 18 y.
Skillington et al.[43]	N=14	Visual Analog Scale (VAS) score	Healthy	Tested across 2- and 3-day tournaments.
Everhart et al.[48]	Cross-sectional	Single-leg squat	Pain vs. no pain	Collegiate softball pitchers
Everhart et al.[48]	N=75	Pitching biomechanics	Pain vs. no pain	Collegiate softball pitchers
Barfield et al.[49]	Cross-sectional	Single-leg squat	Healthy	Youth softball pitchers.
Barfield et al.[49]	N=26	Pitching biomechanics	Healthy	Youth softball pitchers.
Friesen et al.[11]	Cross-sectional	Single-leg squat	Healthy	Youth softball pitchers.
Friesen et al.[11]	N=55	Pitching kinematics at foot contact	Healthy	Youth softball pitchers.
Holtz et al.[50]	Prospective cross-sectional	Missed time due to injury in the past year	Pain vs. no pain	Youth softball pitchers.
	N=23	Current pain patterns
	N=23	Kerlan-Jobe Orthopaedic Clinic (KJOC) Shoulder and Elbow Score
Sauers et al.[51]	Cross-sectional	Self-report questionnaire of arm injury history and current pain	Pain vs. no pain	High school pitchers (N=10)
	N=25	Disabilities of the Arm, Shoulder, and Hand (DASH) score		Collegiate pitchers (N=15)
	Functional Arm Scale for Throwers (FAST) score			Collegiate pitchers (N=15)

Abbreviations: BMI, body mass index; NCAA, National Collegiate Athletic Association; ROM, range of motion.

Note: Case reports and case studies are not included. See the Results section for text summary.

Methodological quality

Risk of bias was low in all included studies.

Clinical outcomes—anthropometrics

Four studies were related to anthropometrics in softball pitchers. Two studies investigated the relationship between body composition and shoulder and hip ROM.[8] [9] There were group differences in dominant shoulder internal rotation (IR) between the high body fat and healthy body fat percentage groups. Significantly more dominant shoulder IR ROM was found in the high body fat group compared to the healthy body fat percentage group.[9] When comparing bilateral differences, the healthy body fat percentage group had significantly less throwing shoulder IR ROM than the non-throwing shoulder. Another study comparing body composition groups reported differences in hip IR ROM. Lead and trail hip IR ROM were significantly higher in the underweight group than the obese group when categorized via a body mass index.[8] There were two proposed explanations for the group differences. It was hypothesized that the differences may be attributed to activity levels. In other words, the high body fat group may be less active and thus complete fewer repetitions compared to the healthy body fat group.[9] However, activity levels were not measured. The other explanation is that those with higher body fat exhibit higher amounts of fatty tissue around the joint, resulting in a less ROM due to obstruction.[8] [9]

When comparing bilateral anthropometric differences, studies indicated that pitcher’s throwing arms had a significantly higher total mass, fat mass, lean mass, bone mineral density, and bone mineral content (BMC) than their non-throwing arms.[9] [15] Additionally, Czeck et al. compared across positions and revealed that pitchers were significantly taller than outfielders and infielders and had significantly more total mass, fat mass, percent body fat, and BMC than outfielders.[15] Peart et al. also determined that pitchers had significantly more fat mass and body fat percentage than catchers, outfielders, and infielders.[16] From pre-season to post-season, outfielders, infielders, and catchers demonstrated a decrease in body fat percentage and fat mass while pitchers displayed differing adaptions.[16] Softball pitchers had an increase in fat mass from pre- to post-season. Furthermore, they exhibited a decrease in body fat percentage from pre- to post-season but an increase from mid-season to the post-season.[16] However, it is unclear based on the article whether these changes were statistically significant.

Clinical outcomes—ROM

A total of 10 papers reported assessments of shoulder and/or hip ROM in softball pitchers ([Table 2]). Six papers were descriptive in nature and four tracked ROM across various time points in response to workload. Descriptive studies have consistently reported that softball pitchers have no bilateral differences in shoulder and/or hip IR, external rotation (ER), or total ROM (TROM).[17] [18] [] [] [21]

Table 2 Summary of clinical outcomes—ROM
Study	ROM assessed	Testing position	Key findings
Friesen et al.[16]	Hip and shoulder IR, ER, & TROM	Hip: seated position with knees flexed 90°	No significant bilateral differences. Differences between pitchers and positional players were found.
Friesen et al.[16]	Hip and shoulder IR, ER, & TROM	Shoulder: supine position with shoulder and elbow in 90°
West et al.[17]	Hip IR, ER, flexion and extension; shoulder IR, ER, and flexion; elbow flexion and extension	Hip flexion and extension: supine position	Greater lead hip extension than the trail hip and greater non-throwing shoulder extension compared to the throwing side. Differences between college and high school pitchers were found.
		Hip IR and ER: prone position with knees flexed to 90°
		Shoulder IR and ER: supine position with shoulder and elbow in 90°
		Shoulder flexion: supine position
		Elbow: supine position with shoulder in 30° abduction
Guy et al.[18]	Hip and shoulder IR, ER, and TROM	Hip IR and ER: prone position with knees flexed to 90°	Pitchers increased dominant shoulder IR and TROM but decreased hip ER and TROM over the season. Differences between positional players and pitchers response to workload were found.
Guy et al.[18]	Hip and shoulder IR, ER, and TROM	Shoulder IR and ER: supine position with shoulder and elbow in 90°
Shanley et al.[19]	Shoulder IR, ER, TROM, and horizontal adduction	Shoulder IR and ER: supine position with shoulder in 90° of abduction	Decreased dominant shoulder horizontal adduction compared to non-dominant shoulder.
Shanley et al.[19]	Shoulder IR, ER, TROM, and horizontal adduction	Shoulder horizontal adduction: supine position
Oliver et al.[20]	Hip and shoulder IR, ER, and TROM	Hip: seated position with knees flexed 90°	No changes in ROM were found for pitchers. Differences between positional players and pitchers’ responses to workload were found.
Oliver et al.[20]	Hip and shoulder IR, ER, and TROM	Shoulder: supine position with shoulder and elbow in 90°
Talmage et al.[21]	Hip and shoulder IR and ER	Hip: seated position with knees flexed 90°	Decreases in all hip and shoulder ROM variables were found except dominant shoulder ER.
Talmage et al.[21]	Hip and shoulder IR and ER	Shoulder: supine position with shoulder and elbow in 90°
Oliver et al.[10]	Hip and shoulder IR and ER	Hip: seated position with knees flexed 90°	Pain group had significantly less trail hip ER ROM than the no-pain group.
Oliver et al.[10]	Hip and shoulder IR and ER	Shoulder: supine position with shoulder and elbow in 90°
Oliver et al.[24]	Hip IR and ER	Hip: seated position with knees flexed 90°	A main effect for drive hip ER ROM and a peak rate of distal energy outflow but not post-hoc testing lacked significance.
Oliver et al.[22]	Hip and shoulder IR and ER	Shoulder: spine position with shoulder and elbow in 90°	No significant changes in hip or shoulder ROM were found before and after games.
Oliver et al.[22]	Hip and shoulder IR and ER	Hip: seated position with knees flexed 90°
Yang et al.[23]	Shoulder forward flexion, abduction, ER at 90° abduction, and ER at 0° abduction	Used previously described methods.	At the end of the season, a decrease in shoulder abduction was found after the game compared to pre-game measurements.

Abbreviations: ER, external rotation; IR, internal rotation; ROM, range of motion; TROM, total range of motion.

Alternatively, shoulder flexion/extension and horizontal adduction ROM differences between the throwing and non-throwing shoulders were determined. West et al. indicated that the non-throwing shoulder had significantly greater shoulder flexion (177.27°±2.82°) compared to the throwing side ((175.64°±3.71°), p=0.004) in pitchers.[18] The authors speculated that this may be due to the passive nature of the methods, suggesting that future studies consider implementing both passive and functional methods for ROM measurements.

Additionally, in a descriptive study by Shanley et al., there was a 6.2° deficit in throwing (30.5°±11.7°) shoulder horizontal adduction compared to the non-throwing (36.8°±12.5°) shoulder.[20]

In the hip joint, the only bilateral difference documented was for hip extension.[18] Specifically, the lead hip (18.23°±5.06°) had significantly more hip extension ROM than the trail hip (16.33°±6.12°; p=0.005) in pitchers. The authors hypothesized that the increased lead hip extension ROM is a positive adaptation to absorb energy and assist with forward momentum during the acceleration and follow-through phases of the pitch.

Four studies investigated changes in shoulder and hip ROM in response to workload in softball pitchers.[19] [22] [23] [24] One study documented no differences in hip and shoulder ROM immediately pre- and post-game in collegiate pitchers.[23] In contrast, three studies identified a relationship between ROM and workload.[19] [22] [24]

In collegiate pitchers, a significant increase in throwing shoulder IR (pre-season: 28.8°±3.6°; post-season: 34.4°±3.4°; p=0.002) and TROM (preseason: 123.5°±6.3°; postseason: 130.3°±6.6°; p=0.016) was seen throughout a season.[19] In high school pitchers, Talmage et al. documented a significant decrease in throwing and non-throwing shoulder IR between the pre-simulated game (throwing: 47.9°±4.3° and non-throwing: 46.9°±5.3°) and post-double header (throwing: 44.9°±4.5°, p=0.004 and non-throwing: 43.8°±14.4°, p=0.033) time points.[22] Additionally, non-throwing shoulder ER ROM significantly decreased across almost all time points (pre-simulated game: 106.0°±4.5°, post-simulated game: 102.0°±12.2°, p=0.021; pre-simulated game: 106.0°±4.5, post-double header: 100.0°±12.9°, p< 0.001; pre-double header: 102.5°±4.4°, post-double header: 100.0°±12.0°, p=0.005) which was hypothesized to be due to insufficient recovery time between games.[22] The conflicting responses to the workload for dominant shoulder IR ROM highlight the need for future work in the area.

Finally, Yang et al. tracked shoulder ER, flexion, and abduction ROM before and after a game during the first week of the season as well as during the last week of the season in high school pitchers. No significant dominant shoulder ROM changes were found at the beginning of the season before and after the game; however, at the end of the season, a significant decrease in dominant shoulder abduction (−2.82°, p=0.021) ROM was exhibited after the game.[24] Nonetheless, these studies agree that throwing shoulder ROM is susceptible to adaptations from the physical demands of the windmill softball pitch.

At the hip, both studies presented evidence of decreased ROM in response to the workload. Specifically, there were decreases in bilateral hip TROM (lead hip preseason: 34.7°±5.0°, postseason: 28.5°±3.5°, p=0.006; trail hip preseason: 37.3°±4.4°, postseason: 30.4°±3.3°, p=0.004) and trail hip ER before and after (preseason: 23.0°±3.4°, postseason: 16.3°±2.7°, p=0.001) a competitive season.[19] Likewise, significant losses in bilateral hip IR were also observed between multiple time points during the simulated double header (lead hip pre-simulated game: 28.3°±7.3°, post-double header: 24.7°±7.0°, p=0.002; trail hip pre-simulated game: 29.7°±6.3°, pre-double header: 26.2°±6.6°, p=0.011; trail hip pre-simulated game: 29.7°±6.3°, post-double header: 26.6°±7.2°, p=0.010) and ER ROM (lead hip pre-simulated game: 31.7°±13.5°, pre-double header: 28.1°±14.3°, p< 0.001; lead hip post-simulated game: 30.2°±13.9°, pre-double header: 28.1°±14.3°, p=0.048; lead hip pre-simulated game: 31.7°±13.5°, post-double header: 28.0°±14.6°, p=0.005; trail hip pre-simulated game: 29.8°±6.5°, pre-double header: 25.5°±5.8°, p< 0.001; trail hip pre-simulated game: 29.8°±6.5°, post-double header: 24.6°±6.3°, p< 0.001; trail hip post-simulated game: 27.6°±7.0°, post-double header: 24.6°±6.3°, p=0.007).[22]

Oliver et al. compared shoulder and hip ROM between collegiate pitchers with and without upper extremity pain. The findings showed pitchers with pain had significantly less trail hip ER ROM than those without pain (pain: 39°±5°, no pain: 44°±8°, p=0.012).[10] Finally, from a performance perspective, our search resulted in one study that explored hip ROM and trunk energy flow during the pitch in youth softball pitchers. The regression did result in a significant main effect for trail hip ER ROM with a peak rate of distal trunk energy outflow.[25] However, post hoc tests failed to achieve statistical significance which the authors contributed to the population used. During the windmill pitch, the trail hip performs ER during the stride phase. Decreased trail hip ER ROM can alter pitching mechanics by inhibiting pelvic rotation. This may lead to mechanical changes further up the kinetic chain and increased susceptibility to throwing arm pain and injury.

Clinical outcomes—imaging

Softball pitchers experience a high prevalence of upper extremity pain; therefore, medical imaging (X-ray, magnetic resonance imaging [MRI], ultrasound, etc.) is an essential clinical measure when a fracture or soft tissue injury is suspected. Although research is limited, studies support the need to consider specific injuries in softball pitchers based on their clinical presentation and imaging results. A total of 10 case studies included medical imaging as a clinical outcome measure in softball pitchers.[26] [27] [] [] [] [] [] [] [] [35] Despite epidemiological reports of softball injuries, the most frequently studied injury in softball pitchers was an ulnar stress fracture, which was attributed to high bending and torsional forces placed on the forearm during ball release.[26] [27] [28] [36] An ulnar stress fracture can be confirmed with an X-ray or MRI and should be considered when a pitcher presents with a sudden onset of forearm pain. Another compilation of six case reports utilized MRI to evaluate medial elbow pain and ulnar digit paresthesia in softball pitchers who underwent an ulnar nerve transposition.[29] Using medical imaging, a retrospective softball pitching study confirmed superior labrum anterior posterior tears and recalcitrant biceps tendonitis.[35] Finally, single case reports also used imaging to examine scapular dyskinesis, intramuscular angioma, rib stress fracture, coracoid apophysiolysis, metacarpal stress fracture, biceps tendon rupture, and musculocutaneous nerve injury.[30] [31] [32] [33] [34] [37]

Due to the repetitive nature of the softball pitch, a high prevalence of upper extremity overuse injury, and a lack of pitch count regulations, it is important to study the clinical effects of a simulated game. Ultrasound imaging provides a unique opportunity for understanding upper extremity pathology by measuring acute soft tissue changes. Oliver et al. (2021) and Barfield (2018) determined significant differences in long-head biceps tendon morphology across a simulated game. The findings suggest an inflammatory process may occur at the biceps tendon following a bout of approximately 60 pitches.[38] [39]

Clinical outcomes—strength

A total of 12 papers (30.76%) reported clinical assessments of muscular strength in softball pitchers[9] [10] [18] [19] [23] [25] [40] [41] [42] [43] [44] ([Table 3]). Of the 12 papers, 8 assessed isometric hip strength,[9] [10] [18] [19] [23] [25] [41] [42] 10 assessed isometric shoulder strength,[9] [10] [18] [19] [23] [24] [40] [–] [42] [44] 5 assessed isometric elbow strength,[18] [40] [41] [44] 2 assessed isokinetic upper extremity, lower extremity, or trunk strength,[40] [43] and 1 assessed isometric forearm and wrist/hand strength.[41]

Table 3 Summary of clinical outcomes in strength
Study	Hip strength assessed	Testing method and position	Key findings
Isometric hip strength
Oliver et al.[24]	Hip IR and ER	Make test with HHD, seated, and 90° hip/knee flexion	Drive side hip ER strength associated with energy outflow from the trunk to the arm
Freisen et al.[9]	Hip IR and ER	Make test with HHD, seated, and 90° hip/knee flexion	Greater dominant hip IR strength vs. non-dominant
Oliver et al.[22]	Hip IR and ER	Make test with HHD, seated, and 90° hip/knee flexion	Less hip ER/IR strength on the non-throwing side after the game
Oliver et al.[10]	Hip IR and ER	Make test with HHD, seated, and 90° hip/knee flexion	Greater hip IR strength (throwing side) and ER strength (glove side) in pitchers without pain
West et al.[17]	Hip IR, ER, flexion, extension, and abduction	Make test with HHD, seated, and 90° hip/knee flexion	No difference in hip strength between lead and trail legs
Corben et al.[40]	Hip flexion, extension, abduction, and adduction	Break test with HHD sidelying (abduction and adduction), and prone (flexion and extension)	Dominant side stronger at baseline; fatigue in all tests on both limbs after the game
Guy et al.[18]	Hip abduction and extension	Make test with HHD sidelying (abduction) and prone (extension)	Decreased non-dominant hip abduction strength from pre- to post-season
Isometric shoulder strength
Freisen et al.[9]	IR and ER	Make test with HHD, supine with 90° shoulder ABD and 90° elbow flexion	Greater ER strength in the dominant arm
Oliver et al.[22]	IR and ER	Make test with HHD, supine with 90° shoulder ABD and 90° elbow flexion	No change from pre- to-post-game exposure
Oliver et al.[10]	IR and ER	Make test with HHD, supine with 90° shoulder ABD and 90° elbow flexion	Greater IR strength (glove side) and greater ER strength (both sides) in the pain free group
Guy et al.[18]	IR and ER	Make Test with HHD, prone with shoulder abducted at 90° and elbow flexed at 90°.	Decreased IR and ER strength in non-dominant and decreased ER strength in dominant
West et al.[17]	Flexion, abduction, IR, and ER	Make test with HHD, seated with 90° flexion (flexion), 90° abduction (abduction), 0° abduction and 90° elbow flexion (IR/ER)	Greater abduction and IR strength in the throwing arm
Skillington et al.[43]	Flexion, IR (two positions), ER (three positions), and scaption	HHD (various positions)	Strength decreased in multiple positions over tournament
Yang et al.[23]	ER (three positions), IR, flexion, and scaption	HHD, “make” and “break” tests, and various positions	Decreased supraspinatus, flexion, and ER strength over seasons
Corben et al.[40]	Flexion, abduction, adduction, scaption, IR, ER, and periscapular	Break test with HHD and various positions	Baseline strength greater in the dominant arm (flexion, abduction, adduction, scaption, and periscapular); fatigue post-game (all tests and both arms)
Skoumal et al.[39]	Flexion, abduction, IR, ER, and periscapular	MMT	Strength ranged 4- to 5/5 MMT bilaterally
Isometric elbow strength
West et al.[17]	Flexion and extension	Make test with HHD, seated (flexion), and supine (extension)	Greater elbow flexion and extension strength in the throwing arm
Corben et al.[40]	Flexion	Break test with HHD and supine	Increased elbow flexion and extension strength (dominante side) at baseline and fatigue (both arms) after the game
Skillington et al.[43]	Flexion and extension	HHD and arm at side with elbow flexed 90°	Decreased strength over tournament
Skoumal et al.[39]	Flexion	MMT	5/5 MMT strength observed bilaterally
Isokinetic strength
Skoumal et al.[40]	Shoulder IR and ER	90° and 270°/s	Decreased peak torque for IR and ER
Pletcher et al.[43]	Knee, hip, trunk, and elbow flexion and trunk rotation	150–300°/s	Greater stride leg knee extension peak torque after pitching and greater trunk flexion peak torque after pitching.
Isometric forearm, wrist, and hand strength
Corben et al.[41]	Grip, wrist flexion/extension, and forearm supination/pronation	Break test with HHD in the neutral glenhohumeral position with elbow at 90° flexion (Grip), seated with elbow flexed 90° (wrist flexion/extension, and forearm supination/pronation)	Greater pronation, supination, and grip strength (dominant arm) at baseline, fatigue for supination, wrist flexion (both arms), fatigue for pronation, wrist extension, and grip (dominante arm)
Athletic shoulder test
Skoumal et al.[40]	ASH test	Prone	Symmetrical and good strength observed in all three positions

Abbreviations: ER, external rotation; HHD, handheld dynamometry; IR, internal rotation; MMT, manual muscle testing.

Isometric hip strength

Hip IR and ER isometric strength were the most frequently cited assessments (n=6). [9] [10] [18][23] [25][42] Isometric hip IR and ER strength was most tested using a “make test” with handheld dynamometry (HHD) in the seated position, with the hip and the knee flexed to 90°.[9] [10] [18] [19] [23] [25] Oliver et al. examined the relationship between hip isometric strength and energy flow during the windmill pitch in 29 youth softball pitchers. The authors identified an association between increased drive side hip ER isometric strength and increased net energy flowing out of the trunk during the pitch (trunk: F _1,27=4.403, p=0.045, Δr ²=0.140, β=0.374, achieved power=0.68; humerus: F _1,27=12.107, p=0.002, Δr ²=0.310, β=0.556, achieved power=0.97).[25] Freisen et al. compared hip IR and ER isometric strength between pitchers with high and healthy body fat percentages. While no differences were observed in hip strength between body fat percentage groups, the authors reported significantly greater hip IR isometric strength on the dominant hip compared to the nondominant hip (mean difference=10 kgf) for all pitchers.[9]

Oliver et al. assessed the effect of game exposure on hip IR and ER isometric strength in five collegiate softball pitchers. The authors reported less hip IR isometric strength (mean difference=−2.02%, p=0.013) and ER (mean difference=−1.95%, p=0.026) in pitchers on the non-throwing side from pre- to post-game exposure.[23] In a different study, Oliver et al. assessed isometric hip IR and ER strength in collegiate softball pitchers with and without upper extremity pain. The authors reported greater throwing-side hip IR isometric strength (no pain=18±4% body weight, pain=16±3% body weight, mean difference=2, p=0.038) and glove side hip ER isometric strength (no pain=16%±4% body weight, pain=13%±4% body weight, mean difference=2, p=0.025) in pitchers without pain.[10]

West et al. assessed isometric hip IR, ER, flexion, extension, and abduction strength to assess whether differences exist between the lead and trail legs in high school and collegiate pitchers. The authors reported no differences in hip strength between the lead and the trail limb.[18] Two additional papers assessed isometric hip flexion,[41] extension,[19] [41] abduction,[19] [41] and adduction strength.[41] Corben et al. assessed muscular fatigue after pitching a game in a group of 19 youth softball pitchers. Isometric hip flexion, extension, abduction, and adduction strength were assessed with HHD. The authors reported greater dominant side hip flexion (6.4%±7.5%, p<0.01) and abduction (7.3%±7.3%, p<0.001) at baseline, with fatigue in all four strength tests on both limbs after game performance.[41] Finally, Guy et al. assessed isometric hip abduction and extension strength changes across a competitive season in 53 collegiate softball players. The authors reported decreased hip abduction strength on the non-dominant hip from pre-season to post-season in pitchers (change=−5.0 lb, p=0.001).[19]

Isometric shoulder strength

Isometric IR and ER strength testing were the most frequently used assessments of shoulder strength. Specifically, these measures were reported in all 10 papers examining isometric shoulder strength.[9] [10] [18] [19] [23][40] [–] [42] [44] Isometric shoulder IR and ER strength was most assessed using a “make test” with HHD in a supine position, with the shoulder abducted to 90°, and the elbow flexed to 90°.[9] [10] [19] [23] [41] The study by Freisen et al. included isometric shoulder IR and ER strength testing in their assessment of pitchers with healthy and high body fat percentages. The findings showed significantly greater ER isometric strength on the dominant arm compared to the non-dominant arm for all softball pitchers included in the study, regardless of body composition (mean difference=10 kg).[9] Oliver et al. also assessed isometric shoulder IR and ER strength in their assessment of the effects of game exposure on isometric strength. They reported no differences in shoulder strength from pre- to post-game exposure.[23] The study by Oliver et al. examining functional characteristics in softball pitchers with and without upper extremity pain also included an assessment of isometric shoulder IR and ER strength. The authors reported significantly greater isometric shoulder IR strength on the glove side (pain=19±5% body weight, no pain=15±4% body weight) and isometric ER strength on both the throwing (pain=21±5% body weight, no pain=17±6% body weight) and glove sides (pain=21±5% body weight, no pain=18±4% body weight) in pitchers without pain.[10] Guy et al. assessed changes in isometric IR and ER shoulder strength across a competitive season. Pre- to post-season changes were observed in pitchers, with a decrease in both ER (pre-season=21.6±2.2 lbs, post-season=18.3±3.4 lbs, p<0.001) and IR (pre-season=24.0±4.0 lbs, post-season=19.1±3.4 lbs, p=0.002) strength in the non-dominant shoulder as well as a decrease in ER strength in the dominant throwing shoulder (pre-season=21.1±3.1 lbs, post-season=19.2±3.6 lbs, p=0.045).[19]

Four additional papers assessed IR and ER isometric shoulder strength as well as isometric shoulder flexion,[18] [24] [41] [42] abduction,[18][41] [42] adduction,[41] scaption in full IR (empty can),[24] [41] [42] and periscapular[41] [42] isometric strength. West et al. assessed differences in isometric shoulder flexion, abduction, IR, and ER strength between throwing and non-throwing arms. The authors assessed shoulder flexion and abduction in the seated position with the shoulder flexed or abducted to 90° and forearm in full pronation.[18] HHD was used to measure isometric strength. The authors reported that the throwing-arm had significantly increased shoulder abduction and IR strength compared to the non-throwing arm, with no other significant strength differences reported for the shoulder.[18] The systematic review by Stamm et al. presented two papers that included a clinical assessment of shoulder strength in softball pitchers.[42] The work of Oliver et al., highlighted above, and Skillington et al., assessed shoulder pain, fatigue, and isometric shoulder strength with HHD in 14 youth softball pitchers throughout a tournament.[10] [44] Skillington et al. measured dominant isometric shoulder scaption with the shoulder in full IR (empty can), flexion, ER in three positions, and IR in two positions. The authors reported a significant decrease in shoulder strength in flexion, abduction, ER at 0° abduction, ER at 90° abduction, IR at 90° abduction, and IR lift off during the tournament.[44] Yang et al. also examined the effect of fatigue on youth softball pitchers’ shoulder strength during the season with HHD. The authors assessed shoulder ER in three positions using a “make test” with the elbow flexed at 90°; (1) with the arm by the side in neutral rotation, (2) with the shoulder abducted 90° in 0° ER, and (3) with the shoulder abducted 90° in 90° ER. The authors assessed IR using a “make test”, with the shoulder abducted to 90° in 0° ER and with the hand behind the back using a lift off technique. Finally, the authors assessed shoulder flexion strength with the shoulder flexed to 90°, the elbow fully extended, and the forearm in complete supination. Supraspinatus strength was measured with the shoulder in scaption and full IR (empty can). Shoulder flexion and supraspinatus tests were performed using a break test.[24] The authors reported empty can, flexion, and ER strength measured in abduction decreased significantly from pre- to post-game as well as across a season (supraspinatus pitched<10 games, strength change=0.35 lbs vs.>10 games strength change=−1.88 lbs, p=0.033; flexion pitched<10 games, strength change=0.41 lbs vs. pitched>10 games strength change=−1.64 lbs, p=0.004; ER pitched<10 games, strength change=1.47 lbs vs.>10 games strength change=−0.59 lbs, p=0.002). Corben et al. included an assessment of isometric shoulder flexion, abduction, adduction, ER, IR, scaption in full IR (empty can), and periscapular muscle strength in their assessment of muscular fatigue after pitching performance.[41] The authors reported increased shoulder flexion (7.8%±8.4%, p<0.001), abduction (10.2%±7.5%, p<0.001), adduction (11.6%±6.6%, p<0.001), and empty can strength (8.3%±13.6%, p<0.01) in the dominant arm at baseline, with post-game fatigue in all shoulder tests on both arms. For periscapular strength tests, the authors reported increased strength on the dominant side for middle (5.0%±7.9%, p<0.01) and lower trapezius (8.3%±11.3%, p<0.01) at baseline, with post-game fatigue in the middle and lower trapezius as well as the rhomboids in bilateral arms.[41] Finally, Skoumal et al. described a case report of a youth softball pitcher with scapular dyskinesis. The authors included an assessment of isometric shoulder strength using manual muscle testing (MMT) for shoulder flexion, abduction, ER, IR, and periscapular musculature, with strength ranging from 4- to 5/5 MMT bilaterally.[40]

Elbow isometric strength testing

Five papers included an assessment of isometric elbow strength.[18] [24] [40] [41] [44] West et al. included a measure of isometric elbow flexion strength using HHD between high school and collegiate pitchers. Elbow strength was assessed with a “make test” in the seated position with the shoulder at 0° abduction, elbow at 90° flexion, and the forearm in full supination. Elbow extension strength was examined in the supine position with the shoulder at 90° flexion, elbow at 90° flexion, and the forearm held in neutral. The authors reported greater elbow flexion (21.77±2.95 kg vs. 19.11±2.57 kg) and extension strength (14.96±2.33 kg vs. 14.27±2.60 kg) in the throwing arm compared to the non- throwing arm.[18] Corben et al. assessed isometric elbow flexion strength with HHD to determine the effects of pitching game performance on muscular strength. The authors performed testing in a supine position with the shoulder abducted to 90° and the elbow flexed to 90° using a “break test”. The authors reported increased elbow flexion (5.9%±8.3%, p<0.01) and extension strength (16.8%±11.5%, p<0.01) on the dominant side at baseline, with bilateral and symmetrical fatigue for elbow flexion post-game. Post-game fatigue for elbow extension was only observed in the dominant limb.[41] Yang et al. also examined the effect of fatigue on elbow flexion and extension strength in their study of high school softball pitchers. The authors tested elbow flexion and extension strength with the elbow flexed at 90° using a “break test” with HHD. No significant changes were found in elbow flexion or extension strength.[24] Similarly, Skillington et al. assessed shoulder pain, fatigue, and isometric elbow strength in youth softball pitchers throughout a tournament. The authors measured isometric elbow flexion and extension strength using a HDD with the arm held by the side, the elbow flexed to 90°, and the forearm supinated for flexion testing and pronated for extension testing. The authors reported a significant loss in both elbow flexion (median difference with 95% confidence interval=3.5 [2.1–4.9] kg) and extension strength (median difference with 95% confidence interval=2.5 [1.6–3.3] kg) in a single competition day and an entire tournament.[44] Finally, Skoumal et al. included an assessment of isometric elbow flexion strength in their case study of a pitcher with scapular dyskinesis. The authors utilized a MMT to assess elbow flexion strength and observed 5/5 strength bilaterally.[40]

Isokinetic strength

Two papers used isokinetic dynamometry to assess strength in softball pitchers.[40] [43] The case study of a youth pitcher with scapular dyskinesis by Skoumal et al. examined shoulder IR and ER strength at 90 and 270°/s with an isokinetic dynamometer. The authors reported deficits in peak torque of the internal and external rotators, which improved after a 2-month course of physical therapy. This was focused on increasing the strength of the middle trapezius, lower trapezius, serratus anterior, and rotator cuff. However, despite improved IR and ER peak torque, the patient reported pain and difficulty returning to pitching.[40] Pletcher et al. investigated upper and lower extremity muscular strength after pitching a simulated game in 14 youth and collegiate softball pitchers. The authors measured concentric and isokinetic flexion and extension strength of the knee, hip, trunk, and elbow, and trunk rotation strength at 300°/s, 150°/s, 180°/s, and 180°/s, respectively. They reported the stride leg knee extension peak torque was significantly higher post-simulated game. Furthermore, trunk flexion peak torque was significantly higher after pitching. The authors attribute these findings to post-activation potentiation that may have occurred from the increased trunk flexion angle reported to occur at the end of a simulated game.[43,45]

Forearm, wrist, and hand isometric strength

Forearm, wrist, and hand isometric strength testing was only reported in one paper by Corben et al. who assessed muscle fatigue before and after pitching a game.[41] The authors measured grip strength in a neutral glenohumeral position with the elbow at 90° flexion. Additionally, wrist flexion/extension and forearm supination/pronation strengths were examined in the seated position with the elbow flexed at 90°. When comparing strength in the dominant vs. non-dominant limb, there was greater pronation (5.4%±11.4%, p<0.05), supination (9.3%±9.4%, p<0.001), and grip strength (13.9%±13.1%, p<0.001) in the dominant limb at baseline. Fatigue was experienced in both limbs for supination, with greater fatigue observed in the dominant limb. Bilateral fatigue and symmetric fatigue were observed for wrist flexion, and fatigue for pronation, wrist extension, and grip was only observed on the dominant side.[41]

Athletic shoulder test

One paper, by Skoumal et al., reported using the Athletic Shoulder Test (ASH) to assess upper extremity muscle strength.[40] The test is performed in the prone position with the shoulder in the I position (shoulder at 180° abduction), the Y position (shoulder at 135° abduction), and the T position (shoulder at 90° abduction). At the same time, the subject exerts maximum forces through the hand into a force plate.[46] The authors reported symmetrical and good strength in all three positions without significant deficits in a youth softball pitcher with scapular dyskinesis.[40]

Elbow flexion and extension isometric strength testing with HHD

During the arm acceleration phase of the windmill pitch, the biceps labral complex must resist large distraction forces at the glenohumeral joint.[5] [9] [47] Furthermore, significantly greater elbow flexion and extension isometric strength has been observed in the pitcher’s throwing arm, with post-game fatigue observed bilaterally for flexion strength and in the dominant limb for extension strength.[18] [41] Given the demands during pitching on the biceps muscle and the post-game fatigue reported for flexion and extension strength, an isometric assessment of elbow flexion and extension isometric strength with HHD is recommended. West et al. described performing the elbow flexion test using a “make test” in a seated position with the upper arm held at 0° abduction, 90° elbow flexion, and the forearm in full supination.[18] A systematic review reported good to excellent intrarater reliability with this assessment technique.[48] Elbow extension strength testing was described by West et al. using a “make test” in a supine position with the upper arm held at 90° shoulder flexion, 90° elbow flexion, and the forearm in neutral.[18]

Clinical outcomes—functional testing

A total of four papers reported functional clinical outcome measures in softball pitchers.[11] [23] [49] [50] Two studies included youth and adolescent athletes,[11] [50] and two included collegiate level athletes.[23] [49] Of these, three studies only included softball players.[23] [49] [50] The others including baseball and softball players reported outcomes for each group separately.[50] One paper assessed the countermovement jump (CMJ) [23] and three assessed the single leg squat (SLS) as functional outcomes.[11,49,50]

Countermovement jump

One study examined the effects of pitching a simulated game on outcomes of ROM, strength, and vertical jump performance. Oliver et al. assessed CMJ performance as a measure of lower body power before and after the simulated game play with five collegiate level pitchers and four collegiate catchers.[23] The authors wanted to determine how game exposure affected various outcome measures between pitchers and catchers. They determined there was no difference in jump height (measured in centimeters) or peak power (measured in Watts) following a simulated game in either pitchers or catchers.[23] The performance demands of specific positions throughout a game vary, and the authors concluded that there is a further need to evaluate position-specific functional outcomes to determine the effects of game performance on injury risk.

Single leg squat

The SLS was used to examine lumbopelvic–hip complex stability in three studies.[11] [49] [50] Everhart et al. compared performance on the SLS to reported pain outcomes in 75 collegiate softball pitchers. The authors compared measures of knee valgus, trunk rotation, and trunk lateral flexion during the SLS. There were no significant difference in SLS mechanics in pitchers who reported pain and those who did not.[49] Freisen et al. examined the association between SLS performance and windmill pitching mechanics in 55 youth softball players and observed SLS compensations were associated with faulty pitching mechanics. They reported an association between increased trunk flexion during the SLS and greater knee valgus at foot contact during the windmill pitch. They also identified an association between increased trunk rotation during the SLS and increased trunk flexion at foot contact during the windmill pitch.[11] This highlights the importance of addressing single leg stability and neuromuscular control to prevent potential injury and optimize performance in softball pitchers.

Clinical outcomes—performance reported outcomes

Two studies reported performance outcomes for softball pitchers following injury. The first study was a retrospective analysis by Rothermich et al. of 15 fastpitch players (78% of pitchers were of high school age and 22% of pitchers were of collegiate age) treated surgically superior labrum anterior–posterior (SLAP) repairs vs. tenodesis.[35] They found 97% of pitchers returned to competition following either procedure.

Holtz et. al determined that adolescent softball pitchers reported a lower pre-season Kerlan-Jobe Orthopedic Questionnaire (KJOC) than baseball pitchers.[51] Pitchers scoring less than 90 on the KJOC had a significantly increased risk of reporting an injury in the subsequent season.

Disabilities of the Arm, Shoulder, and Hand (DASH) and the Functional Arm Scale for Throwers© (FAST©) were used in adolescent and collegiate softball pitchers.[52] Mild to severe pain was reported by 60% of participants and both pain and injury were associated with lower quality of life scores.

Patel et al. reported a prospective evaluation of injuries in eight pitchers in the Women’s National Professional Fastpitch league over the 2017 season.[53] One pitcher had a season ending overuse injury to their shoulder. Patel et. al.’s findings suggested that for each 100 pitches thrown per season, they were 5% more likely to sustain an injury.

Discussion

In this study, we performed a systematic review of the existing softball literature on clinical and performance outcomes. Clinicians have leaned on the abundant baseball literature when softball outcome measures are unavailable. A total of 37 studies met inclusion criteria.

From our findings, some key clinical recommendations have emerged. Friesen et al. revealed that whole body fat mass was related to hip rotation and shoulder IR ROM.[8] [9] Body composition is a risk factor that a pitcher could modify to decrease injury risk, and it would be reasonable to monitor the body composition of pitchers at least once per year.

Baseball research has extensively explored clinical outcomes related to performance and injury risk with established age, sport, and position specific normative values. The overhead throwing motion leads to distinct musculoskeletal adaptations, such as differences in shoulder IR ROM between the throwing and non-throwing side (glenohumeral IR deficits (GIRDs)).[54] However, this study showed that GIRD was not identified in the softball pitching population. Additionally, a difference in TROM greater than 5° between throwing and non-throwing shoulders is established as a risk factor for injury in baseball.[55] [56] This clinical recommendation may be applied with caution in softball pitchers, since no bilateral differences in TROM were identified in our study. Furthermore, no studies have officially been conducted in the softball population to establish a relationship with injury risk and TROM differences.

The greatest amount of the literature for softball pitchers existed for strength testing. During the wind-up phase of the windmill pitch, the pitcher must have adequate gluteal muscle strength to maintain neutral frontal plane knee alignment and to position the body for adequate force production down the mound. During the follow-through phase, the pitcher must maintain balance and stability over the stride leg while decelerating the trunk and upper extremity, which also requires considerable gluteal muscle strength. Throughout the acceleration phase of the windmill pitch, the pitcher must have adequate trunk and shoulder strength to maintain the arm path close to the body and resist distraction forces at the glenohumeral joint.[5] [9] [47] Furthermore, significantly greater elbow flexion and extension isometric strength has been observed in the pitcher’s throwing arm, with post-game fatigue observed bilaterally for flexion strength and in the dominant limb for extension strength.[18] [41] Additionally, during the follow-through phase, the pitcher must have adequate shoulder strength to decelerate the arm. Given the associations with shoulder isometric rotational strength, elbow flexion and extension strength, glueal strength, and pain in softball pitchers, post-game fatigue of these muscles, and adequate shoulder strength to reduce glenohumeral joint distraction forces, an assessment of isometric shoulder IR and ER, elbow flexion and extension, and hip IR and ER is recommended. While there is a lack of normative data on shoulder IR and ER strength in softball pitchers, based on the work of Oliver et al., it is recommended that pitchers demonstrate equal throwing and glove side shoulder IR and ER isometric strength. Furthermore, pitchers should aim to achieve a throwing side IR:ER strength ratio of 1.00.[10] During the windmill pitch, scapular stabilization is needed to create a stable base for shoulder rotation. High activation of the serratus anterior muscle has been reported during the acceleration phase of the pitch.[57] The ASH and modified M-AST test was designed to assess neuromuscular activity of the shoulder girdle in contact and overhead sports.[46] The M-AST is recommended to assess periscapular strength and neuromuscular control in softball pitchers due to the high demand for strength in these muscle groups during the windmill pitch.

With the minimal literature regarding functional testing in softball pitchers, the baseball literature has been utilized for clinical decision making recommendations. However, our findings show that the CMJ is a reliable measure of lower body explosive power and neuromuscular coordination in softball pitchers.[58] [59] Performance on the CMJ has also been shown to be correlated with recognized measures of multi-joint strength.[60] Previous studies emphasize the importance of lower body evaluations in predicting upper extremity injury risk, highlighting that more than half of the energy required in a throwing motion originates from the lower body.[5] [25] [61] [62] [63] Since overuse shoulder injuries are common in softball athletes, effective kinetic chain energy transfer from the lower body is crucial to assess in windmill pitching. Reduced hip strength has been identified as a potential risk factor for injuries among softball pitchers.[17] [23] [25] Given the relationship between SLS performance and both strength and pitching pathomechanics, as well as the unilateral nature of windmill pitching, the SLS test is suggested to be used to assess trunk, hip, and single leg neuromuscular control.[11] [49] [64] [65] A stable trunk, hips, and pelvis are essential for optimizing performance and minimizing injury risk during the windmill pitch.[25]

Several case studies in the softball literature have been reported and are summarized in [Table 1]. There was high variability in the reporting of outcomes following an injury. Most included a general comment regarding return to play or throwing. Timelines were not included in most of the studies, primarily due to the nature of clinical follow-up. A standardized template for follow-up in clinical studies is recommended, including time of medical clearance to start an interval throwing program and return to play timing (in months). Other indicators like pre- vs. post-injury season ERA and WHIP should be considered.

It has been suggested that instead of return to play as the sole criterion for recovery following an injury, additional indicators of a baseball pitcher’s recovery to consider might include a return to previous level of play, a subsequent ERA within 2.0 points of pre-injury ERA and whether walks plus hits per inning pitched (WHIP) was within 0.500 of pre-injury rates over the next one to two seasons. In the baseball literature, the most common recent (within the last 5 years) PROs included the Kerlan-Jobe Orthopedic Clinic (KJOC) Questionnaire, the Timmerman-Andrews subjective scoring system, and the Disability of the Arm, Shoulder and Hand (DASH) questionnaires.[66] Both baseball and softball would benefit from a minimal time of follow-up needed in studies. One, and preferably two seasons of subsequent data for an injury with significant time lost from pitching was suggested by van der List et al. as best practice when collecting follow-up data.

A limitation of our study is the small number of studies across multiple clinical outcome measures, which limits our ability to extract and group the data. Another limitation of the literature is the variable ways in which strength, ROM, pain and workload are collected. While clinical outcomes have been extensively explored in baseball athletes, further research is necessary to determine normative and pathological values for ROM, strength, functional tests and return to play readiness.

Conclusions

This review establishes the current picture of reported outcomes in the softball pitching literature. Clinical assessment of the softball pitcher should include an assessment of body composition, bilateral hip and shoulder ROM, imaging when pain occurs, hip and shoulder strength, single and double leg measures of power and stability, measures of pitch count and pitch performance, and functional questionnaires screening for injury history and pain. This review underscores the need for education among providers of softball pitchers, including physicians, physical therapists, athletic trainers, coaches, and strength and conditioning professionals. With the unique demands of a windmill pitch, a standardized reporting framework is necessary, and further research is needed to assist in clinical decision making and return to play recommendations specific to the softball pitcher.

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Fig. 1 Preferred Reporting Items for Systematic Reviews and Meta-Analyses flowchart.[13]