The effect of a forearm-strengthening program on medial elbow gapping in collegiate baseball pitchers

Abstract

Background

Injuries to the ulnar collateral ligament (UCL) are increasing among baseball players at all levels. Elbow forces during pitching routinely exceed levels that cause failure in UCL cadaver studies, highlighting the importance of identifying protective measures against UCL injury. The flexor–pronator mass has been demonstrated as a dynamic stabilizer of the elbow against valgus loads. Increasing dynamic stability of the elbow may help mitigate medial elbow gapping, a known risk factor for UCL injury. The purpose of this study was to determine the effect of an 8-week forearm-strengthening program on medial elbow gapping under ultrasound in collegiate baseball pitchers. We hypothesized that athletes who complete a forearm-strengthening program will have decreased medial elbow gapping under ultrasound in both gravity loaded and stress loaded conditions.

Methods

Fourteen healthy collegiate (National Collegiate Athletic Association Division I) baseball pitchers completed an 8-week forearm-strengthening program in their throwing arm. Forearm girth and forearm strength were measured in the throwing and nonthrowing arm before and after the forearm-strengthening intervention. Medial elbow gapping in gravity-loaded and stress-loaded conditions were measured by ultrasound in the throwing and nonthrowing arm before and after the intervention.

Results

There was a significant main effect of time on throwing-arm forearm girth (pre: 29.21 ± 1.72; post: 29.52 ± 1.64 cm, P = .01), peak grip strength (pre: 5.39 ± 0.76; post: 5.48 ± 0.74 N/kg, P = .03), and average grip strength (pre: 5.39 ± 0.76; post: 5.48 ± 0.74 N/kg, P = .05). There was no significant effect of time on either gravity-loaded (pre: 4.51 ± 0.59; post 4.44 ± 0.48 mm, P = .22) or stress-loaded (pre: 4.94 ± 0.46; post: 4.84 ± 0.54 mm, P = .15) medial elbow gapping in the throwing arm.

Conclusion

Although our forearm-strengthening program led to an increase in forearm girth and grip strength, the average medial elbow gap under a static valgus load was statistically unchanged. Further studies are warranted to explore the utility of strengthening the flexor–pronator mass as a preventive measure against injury in throwers.

Overhead athletes generate significant valgus forces at the elbow during the throwing motion.⁴² Valgus forces from 30°-120° of flexion are primarily resisted by the anterior bundle of the ulnar collateral ligament (UCL),⁷ with the greatest valgus forces occurring at 90° of elbow flexion.⁷ Repetitive valgus stress, as in overhead athletes, can result in microtrauma to the UCL and eventual ligament failure.²¹ Even in asymptomatic athletes, long-term throwing activity is associated with anatomic changes; studies have shown increased medial elbow joint space gapping in the throwing elbow of professional baseball pitchers.^16,43 Further studies have shown that this gapping is increased with more than 60 pitches per game.²⁵ Professional pitchers with greater than 5.6 mm gapping on valgus stress have been found to have a 6-fold greater risk of requiring UCL reconstruction.⁴⁵ Clinically, UCL laxity that occurs as an adaptation to repetitive throwing can make it more difficult to detect true pathology.¹⁶

The ultimate failure load of the UCL in cadaveric studies has been demonstrated to be 34 N m.² Interestingly, however, the valgus force generated during pitching has been reported to average 82 N m for fastballs, with peaks as high as 120 N m,^20,50 exceeding the failure strength of the UCL. This discrepancy between the forces required to resist valgus torque during pitching and the measured failure loads of the UCL has been theorized to be due to other static and dynamic sources of support, including the flexor–pronator mass (FPM).^2,33,36 Multiple studies examining the relative contribution of individual muscles of the FPM have found that the flexor carpi ulnaris (FCU) is the primary dynamic stabilizer of the elbow.^6,29 Other muscles providing a varus force to counteract the valgus stress during pitching include the flexor digitorum superficialis (FDS) and pronator teres.⁶ Weakness or fatigue of the forearm flexor muscles has been hypothesized to increase UCL tension and laxity, potentially leading to injury.^23,38

Previous studies have explored muscle strengthening to minimize risk of UCL injury due to fatigue. Maximal gripping has been shown to reduce medial elbow joint space gapping, likely due to increased muscle activity decreasing UCL stress.^22,38 Another study suggests maintaining muscle volume to avoid excessive elbow flexion range of motion can protect against UCL laxity during pitching.²⁴ While previous studies have shown that weighted baseball training on flat ground increases elbow varus torque,¹⁹ no studies have evaluated the effect of a focused forearm-strengthening program on medial elbow gapping specifically. Thus, the purpose of our study was to determine whether an 8-week forearm-strengthening program would have an effect on medial elbow gapping. We hypothesized that after the strengthening program, medial elbow gapping would be significantly decreased in both the gravity loaded and stress loaded conditions.

Materials and methods

This study was approved by the institutional review board at Seton Hall University prior to data collection. All subjects provided their written consent for inclusion in this study.

Subjects

Sixteen pitchers enrolled in a National Collegiate Athletic Association Division I baseball program were screened for participation. Subjects were excluded if they had a history of surgery to the upper extremity. Two participants were excluded because 1 had a history of a UCL reconstruction 3 years prior and the other had an arthroscopic procedure to débride loose bodies from the elbow 6 months prior, both in the throwing arm. After exclusions, 14 subjects were enrolled in the study. Eleven of the participants were right-handed, and three were left-handed pitchers. Participants had an average age of 20.4 ± 1.8 years, an average weight of 90.3 ± 10.3 kg, and an average height of 1.87 ± 0.09 m. Subjects were involved in the study from August 2023-December 2023.

Data collection

Timeline

Pretest measurements were conducted in the week before the start of fall baseball practices, prior to any throwing activities. Participants were also restricted from engaging in strength training sessions on the day of data collection. During the fall baseball practices, pitchers threw to live batters once weekly (2-4 innings), performed one bullpen session per week, and participated in daily throwing activities (eg, playing catch) on other days. Postintervention assessments, conducted after the 8-week intervention, were scheduled on a day when participants had neither strength training nor practice sessions.

Measurement protocol

We measured forearm girth with the arm at 90° shoulder flexion, forearm fully supinated, and elbow in full extension. The girth measurement was taken using a Baseline Gulik spring-loaded flexible measuring tape (Fabrication Enterprises, White Plains, NY, USA) from the widest part of the forearm three times, and the average of the three measures was recorded to the nearest millimeter.³⁰ This process was repeated on the nonthrowing arm. Then, we performed grip strength testing using the Vald Dynamo grip dynamometer (Vald, Charlotte, NC, USA), a technique previously found to be valid and reliable.⁴ Participants stood with their arm at their side, elbow flexed at 90° with forearm, and wrist at neutral position. Adjustments were made to the dynamometer to accommodate hand-size differences. To avoid active insufficiencies, the handle was set so that the distal phalanx of the thumb was able to overlap the distal phalanx of the second digit. These settings were recorded so they could be used for the post-test. Participants were instructed to squeeze maximally. A total of three repetitions were performed with 10 seconds rest between each. The throwing arm was tested first and then repeated for the nonthrowing arm. Force was measured in Newtons (N), and both the maximal and average grip strength were included for analysis. All girth and strength measures were taken by the same certified athletic trainer (RJB).

Ultrasound technique

The participants were placed supine with the throwing upper extremity in 90° shoulder abduction and maximal external rotation with 50° elbow flexion (Fig. 1). Fifty degrees of elbow flexion was chosen because it is most representative of arm slot used during pitching.⁴¹ This position was confirmed with a standard goniometer measured by a certified athletic trainer. A 15-6 MHz Fuji Film Sonosite Edge II MSK ultrasound transducer (Fuji Film Sonosite MSK Ultrasound, Fuji Film, Bothell, WA, USA) was used to measure medial elbow gapping. All ultrasounds were performed by the same fellowship-trained sports medicine physician (CC) and were assisted by the same certified athletic trainer (RJB).

Figure 1.

Stress ultrasound being performed of medial elbow under (A) gravity load then (B) stress load.

The physician ensured that similar striations and landmarks were viewed in each of the scans to make them comparable (Fig. 2).^11,43 The width of the ulnohumeral joint space at the level of the anterior band of the UCL were measured. Ulnohumeral joint distance measures was defined by a straight-line method between the apex of the humeral trochlea and ulnar coronoid process at the joint line. Measurements were taken under the gravity-loaded condition, followed by the stress loaded condition (2.27 kg dumbbell held lightly by participant, Fig. 1).^5,28 The same procedure was then used for the nonthrowing elbow. The same members of the research team took the post-test measures and were blinded to the pretest measures.

Figure 2.

Ultrasound of the elbow. A, Medial elbow gap distance; C, Coronoid process; T, Humeral trochlea; M, Medial epicondyle.

Eight-week forearm training intervention

All subjects underwent a standardized forearm-strengthening program under the supervision of a strength and conditioning coach (RJB) of the throwing arm only (Table I). The program was completed a total of 22 times over an 8-week span. The program was performed as a supplemental workout to the full body workout plan that was designed by the strength and conditioning coach. The strength and conditioning coach progressed load intensities for the next session when subjects completed the full repetition range of the last set without failure. Dumbbell exercises were able to be progressed in 1.14 kg increments. We used Council Tool (Lake Waccoman, NC, USA) 91.4-cm wood-handle sledgehammers for pronation/supination and radial/ulnar deviation exercises. For pronation/supination, subjects started and ended the strength intervention using the 4.54-kg sledgehammer. As they progressed through the intervention, they moved their hand down the handle (away from the sledgehammer head). For radial deviation/ulnar deviation, subjects started with the lighter 3.63-kg sledgehammer initially and progressed to using the 4.54-kg sledgehammer throughout the intervention. Again, during the progression, subjects moved their hand down the handle (away from the sledgehammer head) to create a larger moment arm and increase torque.

Table I.

Forearm strengthening program.

Exercise	Repetitions	Initial load	Final load	Image(s)
Warm up
Quadruped scapular protraction/retraction	15	BW	BW	Protraction	Retraction
Quadruped scapular elevation/depression	15	BW	BW	Elevation	Depression
Main set
DB wrist flexion curl (half kneel, forearm supported on bench or box)	3 × 10	4.54 kg	10.23 kg
DB wrist extension (half kneel, forearm supported on bench or box)	3 × 10	4.54 kg	7.95 kg
Sledgehammer pronation/supination (half kneel, forearm supported on bench or box)	3 × 10	4.54 kg	4.54 kg	Pronation	Supination
Sledgehammer ulnar/radial deviation (half kneel, forearm supported on bench or box)	3 × 10	3.63 kg	4.54 kg	Ulnar deviation	Radial deviation
Cool down
Quadruped wrist flexor/extensor stretches	1	30 s	30 s	Flexor stretch	Extensor stretch

DB, dumbbell; BW, body weight.

At the conclusion of the 8-week forearm strength training program, all participants underwent the post-test using the identical order and procedures from the pretest.

Statistical analysis

All data were analyzed using JASP statistical software, version 0.18.0.0 (JASP Team, Amsterdam). Descriptive statistics were run first for all measures and evaluated for normalcy. We used intraclass correlation coefficients (ICCs) to assess the intrarater reliability of girth, grip, and medial elbow gapping measures. Specifically, a two-way mixed-effects model with absolute agreement was used (denoted as an ICC [3,k] model). We used separate 2 × 2 analysis of variance to evaluate the interactive and main effects of time (pre vs. post) and arm (throwing vs. nonthrowing) on medial elbow gapping under gravity load (mm), medial elbow gapping under stress load (mm), maximal forearm grip strength normalized to body weight (N/kg), average forearm grip strength normalized to body weight (N/kg), and forearm girth (cm). Data were presented in the form of raincloud plots, which visualize individual subject data in the form of scatter plots, summary statistics (median and interquartile range) in the form of box plots, and distribution data in the form of violin curves. All alpha levels were set at P ≤ .05 a priori.

Results

Reliability

The intrarater reliability was high among the measurements for forearm girth (ICC = .965), grip strength (ICC = .896), medial elbow gapping (ICC = .894).

Forearm girth

After the throwing arm forearm-strengthening program, a significant increase in forearm girth was observed in both the throwing and nonthrowing arms from pretest to post-test (Table II, Fig. 3, P = .009). However, there was no significant interactive effect between arm and time (P = .296), and there was no main effect of throwing vs. nonthrowing arm on forearm girth (P = .529).

Table II.

Forearm girth measurements pre- and poststrengthening program.

Measurement	Pre	Post	P value
Forearm girth (cm)			.009
Throwing	29.21 ± 1.72	29.52 ± 1.64
Nonthrowing	28.90 ± 1.68	29.04 ± 1.52

Figure 3.

Raincloud plots of forearm girth measured pre- and postforearm-strengthening program in the (A) throwing and (B) nonthrowing arm.

Grip strength

When normalized to body weight, an increase in average grip strength was observed in both the throwing and nonthrowing arm (P = .050) (Table III, Fig. 4); however, there was no difference between arms (P = .957). There was no interactive effect between time and arm (P = .344). Normalized maximum grip strength increased after the intervention in both the throwing and nonthrowing arm (P = .031) (Table III, Fig. 5), but there was similarly no difference between the throwing and nonthrowing arm (P = .883), and there was no interactive effect of time and arm (P = .873).

Table III.

Normalized grip strength data pre- and postforearm-strengthening program.

Measurement	Pre	Post	P value
Mean grip strength (N/kg)			.050
Throwing	5.39 ± 0.76	5.48 ± 0.74
Nonthrowing	5.29 ± 0.80	5.55 ± 0.86
Max grip strength (N/kg)			.031
Throwing	5.67 ± 0.89	5.85 ± 0.87
Nonthrowing	5.61 ± 0.84	5.82 ± 0.88

Figure 4.

Raincloud plots of normalized average grip strength pre- and postforearm-strengthening program for the throwing arm (A) and the nonthrowing arm (B).

Figure 5.

Raincloud plots of normalized maximum grip strength pre- and postforearm-strengthening program for the throwing arm (A) and the nondominant arm (B).

Medial elbow gapping

No significant change in throwing-arm medial elbow gapping was observed before and after the forearm-strengthening program in the gravity-loaded trials (P = .218) (Table IV, Fig. 6) or in the stress-loaded trials (P = .145) (Table IV, Fig. 7). No interactive effect was observed between the strengthening program and arm dominance for the gravity-loaded (P = .789) or stress-loaded (P = .892) conditions. Similarly, no effect of throwing vs. nonthrowing arm was observed on gravity-loaded medial elbow gapping (P = .412) or stress-loaded medial elbow gapping (P = .161).

Table IV.

Medial elbow gapping data pre- and postforearm-strengthening program.

Measurement	Pre	Post	P value
Medial elbow gapping gravity-loaded (mm)			.218
Throwing	4.51 ± 0.59	4.44 ± 0.48
Nonthrowing	4.38 ± 0.60	4.26 ± 0.48
Medial elbow gapping stress-loaded (mm)			.145
Throwing	4.94 ± 0.46	4.84 ± 0.54
Nonthrowing	4.66 ± 0.69	4.53 ± 0.61

Figure 6.

Raincloud plots of medial elbow gapping in the gravity-loaded condition before and after the forearm-strengthening program in the throwing (A) and nonthrowing (B) arm. UCL, ulnar collateral ligament.

Figure 7.

Raincloud plots of medial elbow gapping in the stress-loaded condition before and after the forearm-strengthening program in the throwing (A) and nonthrowing (B) arm. UCL, ulnar collateral ligament.

Discussion

This study aimed to assess the effectiveness of an 8-week forearm-strengthening program in reducing medial elbow gapping among baseball pitchers. Our findings indicate that this program did not lead to a statistically significant decrease in average gravity-loaded or stress-loaded medial elbow gapping. The program did lead to increases in grip strength and forearm girth, albeit of unknown clinical significance. While most players had decreases in their medial elbow gap distance, our hypothesis that the forearm-strengthening program would lead to a statistically significant decrease in average medial elbow gapping under a valgus load was not supported.

Although the increases in forearm girth and peak grip strength were statistically significant, the clinical significance of these findings is unclear. The mean increase in forearm girth was approximately 0.3 cm; however, it is noteworthy that every player experienced growth in their throwing-arm girth postintervention. While the average and peak grip strength increased by 0.09 and 0.18 N/kg, respectively, 5 subjects had decreases in average grip strength and 4 had decreases in maximum grip strength. With a smaller cohort and large standard deviations compared to the effect sizes, these several subjects had a large impact on our results. Taken together, it is difficult to conclude that this forearm-strengthening program led to substantial strengthening of the FPM.

The adequacy of the intervention dosage in our forearm-strengthening program warrants scrutiny. A prior study on high school pitchers implemented a 12-week intervention, comparing a general full-body strength training program (three sessions per week) with a combined full-body and supplemental forearm-strengthening regimen (three sessions per week), including wrist curls, reverse wrist curls, plate squeezes, radial and ulnar deviation, and pronation-supination exercises.⁴⁷ Both groups exhibited significant pre-to-post grip strength improvements, with no intergroup differences at post-test. The authors suggested that full-body strength training alone may enhance forearm strength.⁴⁷ Similarly, our study observed increased grip strength and forearm girth in both the intervention (throwing arm) and control (nonthrowing arm) groups, indicating potential nonspecific training effects. In contrast, a 6-week study on collegiate baseball players, incorporating full-body lifting plus forearm exercises (wrist curls, extensions, rolls, and pronation-supination), reported no significant grip strength gains, possibly due to shorter duration or insufficient intensity.²⁶ A systematic review of strength training literature emphasizes that higher volume and intensity (eg, 3-6 sets of 1-12 repetitions at 70%-100% 1-repetition maximum, as recommended by the American College of Sports Medicine for trained individuals) drive optimal muscular strength and hypertrophy adaptations.^3,27 Critical evaluation of our intervention suggests that the exercise selection and dosage were sufficient to elicit strength and hypertrophy gains in our sample, aligning with established guidelines.

While the mean gravity-loaded and stress-loaded medial elbow gapping decreased in the throwing arm by 0.07 and 0.10 mm after the strengthening program, respectively, the average difference was not significant for either. It should be noted that many players decreased their medial elbow gap distance in the gravity-loaded (n = 6) and stress-loaded (n = 7) trials after the strengthening program, which provides merit for further investigation. The reason that several players showed increased medial elbow gapping after the strengthening program is presently unclear. Although the greater stiffness of a hypertrophied FPM musculature could theoretically resist valgus stress, the heterogeneity in our medial elbow gapping findings may stem from the application of a static valgus load, which may have failed to sufficiently activate the FPM as a dynamic stabilizer. A prior study has shown that electromyogram (EMG) activity of the FPM reaches a peak just before maximal external rotation during the throwing motion.⁴⁸

Medial elbow joint space gapping is significantly increased in baseball pitching due to repetitive elbow valgus stresses, which induce tensile stress across the UCL, increasing gapping and leading to degenerative changes.^22,23,49 These changes over time can exacerbate medial joint space gapping and compromise the integrity of the UCL. Hattori et al found that the medial ulnohumeral joint space significantly increases after 60 pitches.²⁵ Moreover, Shanley et al demonstrated that a medial elbow gap of over 5.6 mm under 5.5 lbs valgus stress increases the risk of sustaining UCL tear requiring surgery sixfold.⁴⁵ Currently, an increase of 1.5 mm in medial joint space under a valgus load is used as the threshold to indicate UCL injury.^9,12 However, it is important to note that asymptomatic throwers commonly exhibit greater medial elbow joint space gapping in their throwing arm compared to their nonthrowing arm.³⁴ This trend was reflected in our data, with throwing arms trending towards greater gap distances, both under gravity-loaded and loaded conditions, compared to nonthrowing arms.

UCL injuries have been increasing throughout amateur and adolescent baseball players in recent years, and 25% of major league baseball pitchers have undergone UCL reconstruction.^13,17,31 In response to this trend, several strategies have been explored to protect throwers from medial elbow injury, including managing pitch count and type, modifying pitch mechanics, and increasing glenohumeral joint range of motion.^{1,18,35,44,51} With the ongoing need to identify strategies to prevent UCL injury, this study investigated the effect of strengthening the dynamic stabilizers of the elbow on medial elbow gapping. Previous research has shown that medial elbow gapping is mitigated during valgus stress by the FPM (FCU, FDS, flexor carpi radialis, and pronator teres), which generates a counteracting varus moment.^{14,22,29,36,38}

Past studies have attempted to answer the question of whether forearm strength serves as a modifiable factor in preventing UCL injury. Hattori et al correlated grip strength with medial elbow joint space gapping at a single time point in pitchers and found no relationship.²³ In a subsequent study by Hattori et al using ultrasound elastography, it was shown that although medial elbow gapping decreased 19% during gripping compared with rest (3.1 mm from 3.8 mm), the strain ratio of the UCL vs. FPM did not change. This suggests that even when the FPM is contracted, there may not be any relative offset of tensile stress from the UCL to the FPM.²² As these prior studies were cross-sectional in design, our study aimed to build upon their results by implementing a strengthening program to see if players could develop their FPM to protect their UCL.

We measured medial joint space gapping with stress ultrasound (SUS) with the subjects supine, shoulder abducted to 90°, in maximal external rotation, and the elbow flexed to 50°. SUS has been established as a reliable and precise method for evaluating the UCL integrity and ulnohumeral joint space and has a sensitivity, specificity, and accuracy of 96%, 81%, and 87% for detecting UCL injury, respectively.^5,40 SUS offers the advantage of avoiding the invasive intra-articular contrast injection required for magnetic resonance arthrography and the radiation exposure of stress radiographs. Most prior studies have measured medial elbow gapping under either 30° or 90° of elbow flexion.9, 10, 11^,37,40 Recent studies have suggested that performing SUS with the elbow flexed to 90° is superior in demonstrating medial elbow laxity versus 30° of elbow flexion.^32,52 Rogers et al report maximum valgus laxity at 50° of elbow flexion in a cadaver model.⁴¹ We acknowledge the variability in previously reported SUS studies; however, we felt that 50° of elbow flexion would be a more representative position for the elbow as it transitions from the late cocking to acceleration phase of the throwing motion, when maximal valgus stress is applied to the elbow.^15,41

In our study, the loaded medial elbow gap distance was measured while patients held a 2.27 kg (5 lbs) weight, generating a 22.3 N valgus force. Various techniques have been reported in the literature for applying a valgus load to the elbow.^11,37,46 In a cadaver study by Ciccotti et al, a standardized stress device was used to apply 150 N of valgus force were applied across. The selection of 150 N was based on a prior study demonstrating that 150 N provided sufficient load to observe medial elbow joint space widening on stress radiographs.³⁹ The 2.27 kg load used in this study is similar to the load used in other SUS studies,^8,37,45 and is based on a study on healthy elbows that showed that 2.27 kg is sufficient to elicit a statistically significant increase in joint space gapping on stress radiographs.²⁸ Although 2.27 kg (22 N) has been used in prior studies, a recent study by Yoshioka et al showed that FPM recruitment primarily occurs with a valgus load of greater than 60 N, regardless of the elbow flexion angle. This represents a limitation of this study in that the valgus load used may not have been large enough to recruit the FPM to a meaningful degree. Participants held the weights in this study, with the reasoning that lightly gripping the weight would fire the FPM (specifically FCU and FDS) to a greater degree and more accurately simulate patients gripping a baseball, compared to if the participants had the weight strapped to their wrist.

Limitations

The authors acknowledge several limitations. The nonthrowing arm was used to control against the throwing arm, which received the treatment intervention. However, players underwent a simultaneous full-body strength training program, which invariably trained their nonthrowing arm. In addition, it was difficult to standardize the resistance in several of the exercises in the program, such as the sledgehammer exercises. In addition, we measured medial elbow gapping under a static load; however, the throwing motion places a dynamic load on the flexor pronator mass, so it is possible that under the static load, this muscle group did not fire to the degree that it would under a dynamic load. We had the players lightly grip the weight to try to mitigate this effect. While the valgus load used in this study is consistent with prior studies, the load may not have been sufficient to recruit the FPM to a meaningful degree. Our study also has the limitation of having a single individual perform all measurements; however, we calculated intrarater reliability to attempt to mitigate this bias. Lastly, with a relatively small sample size, the variation in our data had a large impact on the standard deviations of our measurements, with obvious implications for statistical analysis. Future study aimed at answering this question should be undertaken to include a larger cohort of baseball players with both a true treatment and control group.

Conclusion

This study showed that this 8-week forearm-strengthening study was not effective in decreasing medial elbow gapping in gravity-loaded or stress-loaded conditions in collegiate pitchers, despite modest increases in forearm girth and grip strength. Although the aggregate data did not support the hypothesis that strengthening the FPM would decrease medial elbow gapping, there was large heterogeneity among the subjects, with many players exhibiting decreased medial elbow gapping after the intervention. Further investigation is warranted with a larger cohort and potentially a more rigorous forearm-strengthening program.

Acknowledgment

We would like to thank Fuji Sonosite for loaning their Edge II MSK ultrasound unit to be used for data collection; Angelo Gingerelli, a strength and conditioning coach, for agreeing to add the supplemental program into the strength and conditioning program and supervise and track progress of the participants; and the coaching staff and players from the Seton Hall University Baseball team for their support and participation in the study.

Disclaimers:

Funding: No funding was disclosed by the authors.

Conflicts of interest: BJE discloses AAOS: board or committee member; American Orthopaedic Society for Sports Medicine: board or committee member; American Shoulder and Elbow Surgeons: Board or committee member; Arthrex, Inc.: paid consultant; DePuy, Johnson & Johnson Company: research support; Linvatec: research support; PLOS One: research support, editorial or governing board; Smith & Nephew: research support. The other authors, their immediate families, and any research foundation with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.