Intraclass correlation coefficients ranged from 0.47 to 0.87 for the right arm and 0.62 to 0.84 for the left arm, indicating moderate to good intrarater reliability22 of our procedure, with a standard error of measurement of 5.8° for the right arm and 5.3° for the left arm. Interrater reliability for measurements was 0.20 for the right arm and 0.40 for the left arm. Percent agreement was high (>85%), and percent chance agreement (81%). Mullaney et al23 report that using a digital leveler to measure the ROM of the shoulder is reliable, with a rotation measurement error of ±3° and an ability to detect differences in ROM of 6° with the same examiner and 15° between different examiners.
In this study of asymptomatic minor league baseball players, we found that over half had measurable loss of shoulder motion compared with their contralateral shoulder. Many previous studies have offered treatment algorithms to improve shoulder ROM. Sleeper stretch and cross stretching most commonly have been shown to improve IR. Many experienced therapists and athletic trainers have developed their own treatment regimen of stretching. With this study, we attempted to validate scientifically what we had observed anecdotally about the relationship between SI joint tightness and posterior shoulder capsule tightness. Our results demonstrated that internal end-range rotation improved with the “benchmark” sleeper's stretch; however, rotation improved twice as much stretching the contralateral SI joint.
Although tightness of the pelvis causing tightness of the shoulder is a new concept and much more research needs to be done to understand the reason behind this phenomenon, several studies show the correlation between loss of motion in the hip with loss of motion in the shoulder in pitchers from youth to professional baseball.2 - 32
Commonly, baseball players have been noted to possess decreased trunk rotation, shoulder IR of the throwing arm, external rotation of the dominant hip, and IR of the nondominant hip.27 , 33 Zeppieri et al32 demonstrated that the nondominant (lead) hip ROM and strength decreased over the course of a season. Picha et al31 found differences in ROM of both the hip and shoulder in youth baseball pitchers.
At present, a paucity of literature exists to support the complex relationship between the lower back and GIRD. However, two studies investigated improvement in shoulder range of motion with rotating the trunk along with stretching the shoulder.7 , 34
The pitching motion is a kinetic chain. In the past, most of the literature focused on the upper extremity in pitchers. MacWilliams et al35 pioneered the importance of the lower extremity in contributing in the throwing motion and suggested that strengthening of the lower extremities could enhance performance and avoid injury. The force generated by the large muscles of the lower extremity and trunk during the wind-up and stride phases are transferred to the ball through the shoulder and elbow during the cocking and acceleration phases.36 Breaks in this kinetic chain are known to increase the risk of injury.
Perhaps the great forces generated in the wind-up and stance phases throw the pelvis out of alignment, producing GIRD. If this phenomenon proves to be true, orthopaedic surgeons must not simply focus on the shoulder of overhead athletes with GIRD, getting mixed results, but also evaluate the lower back, looking for the true source of an injury, thus, obtaining quick, long-lasting relief and preventing future injuries. As the saying goes, “The trunk must be stable to support the limbs.”
There are several limitations to this study. First, the sample size is small, and the sizes between randomized groups are uneven. In addition, the cohort included both pitchers and position players. Future studies should attempt to study a more homogenous group. We also had measurements only for one point in time; thus, it is impossible to conclude whether the range-of-motion gains were maintained over time. We do not have any data on our study subjects regarding injuries, pain, or games missed due to pain/injury. We used a novel approach to our range of motion measurements that has not been validated in the literature. On the basis of this small pilot study, we recommend future research to confirm our findings. Because our study focused on only minor league baseball players, our findings may not be generalizable to other athletes or patient populations.
On the basis of our data, there may be a subset of baseball players with a glenohumeral internal rotation deficit that is in part caused by SI joint tightness and may benefit or resolve from stretching the pelvis. Further anatomic and functional research studies are necessary to understand this pathophysiology.
The authors thank the entire Schaumburg Boomer Baseball Team, Jamie Bennet (manager), and Pat Salvi (owner) for graciously allowing them to conduct this research. They are also thankful to Ms. Nadia Poponne and Ms. Cynthia Wenham, Librarians, Ross University School of Medicine, and Ms. Lisa Blackwell, Director Library Services, Chamberlain University for their help in locating references used in this investigation. In addition, they thank the Resource Sharing and Print Resources Access Management units, Drexel University Libraries, for their help in locating references used in this investigation.
1. Burkhart SS, Morgan CD, Ben Kibler W: The disabled throwing shoulder: Spectrum of pathology Part I: Pathoanatomy and biomechanics. Arthroscopy 2003;19:404–420.
2. Bigliani LU, Codd TP, Connor PM, Levine WN, Littlefield MA, Hershon SJ: Shoulder motion and laxity in the professional baseball player. Am J Sports Med 1997;25:609–613.
3. Borsa PA, Dover GC, Wilk KE, Reinold MM: Glenohumeral range of motion and stiffness in professional baseball pitchers. Med Sci Sports Exerc 2006;38:21–26.
4. Borsa PA, Wilk KE, Jacobson JA, et al: Correlation of range of motion and glenohumeral translation in professional baseball pitchers. Am J Sports Med 2005;33:1392–1399.
5. Brown S: Knowledge for Health Care Practice: A Guide to Using Research Evidence. Philadelphia, PA, Saunders, 1999.
6. Reinold MM, Wilk KE, Macrina LC, et al: Changes in shoulder and elbow passive range of motion after pitching in professional baseball players. Am J Sports Med 2008;36:523–527.
7. Escamilla RF, Yamashiro K, Mikla T, Collins J, Lieppman K, Andrews JR: Effects of a short-duration stretching drill after pitching on elbow and shoulder range of motion in professional baseball pitchers. Am J Sports Med 2017;45:692–700.
8. Myers JB, Laudner KG, Pasquale MR, Bradley JP, Lephart SM: Glenohumeral range of motion deficits and posterior shoulder tightness in throwers with pathologic internal impingement. Am J Sports Med 2006;34:385–391.
9. Shanley E, Rauh MJ, Michener LA, Ellenbecker TS, Garrison JC, Thigpen CA: Shoulder range of motion measures as risk factors for shoulder and elbow injuries in high school softball and baseball players. Am J Sports Med 2011;39:1997–2006.
10. Wilk KE, Macrina LC, Fleisig GS, et al: Deficits in glenohumeral passive range of motion increase risk of elbow injury in professional baseball pitchers. Am J Sports Med 2014;42:2075–2081.
11. Lintner D, Mayol M, Uzodinma O, Jones R, Labossiere D: Glenohumeral internal rotation deficits in professional pitchers enrolled in an internal rotation stretching program. Am J Sports Med 2007;35:617–621.
12. Laudner KG, Sipes RC, Wilson JT: The acute effects of sleeper stretches on shoulder range of motion. J Athl Train 2008;43:359–363.
13. Manske RC, Meschke M, Porter A, Smith B, Reiman M: A randomized controlled single-blinded comparison of stretching versus stretching and joint mobilization for posterior shoulder tightness measured by internal rotation motion loss. Sports Health 2010;2:94–100.
14. McClure P, Balaicuis J, Heiland D, Broersma ME, Thorndike CK, Wood A: A randomized controlled comparison of stretching procedures for posterior shoulder tightness. J Orthop Sport Phys Ther 2007;37:108–114.
15. Pathoomvanh M, Feldbrugge C, Welsch L, Van Lunen B: The effectiveness of posterior shoulder stretching on reducing posterior shoulder tightness in overhead athletes: A critically appraised topic. Int J Athl Ther Train 2016;21:8–13.
16. Reuther KE, Larsen R, Kuhn PD, Kelly JD, Thomas SJ: Sleeper stretch accelerates recovery of glenohumeral internal rotation after pitching. J Shoulder Elbow Surg 2016;25:1925–1929.
17. Wilk KE, Hooks TR, Macrina LC: The modified sleeper stretch and modified cross-body stretch to increase shoulder internal rotation range of motion in the overhead throwing athlete. J Orthop Sport Phys Ther 2013;43:891–894.
18. Yamauchi T, Hasegawa S, Nakamura M, et al: Effects of two stretching methods on shoulder range of motion and muscle stiffness in baseball players with posterior shoulder tightness: A randomized controlled trial. J Shoulder Elbow Surg 2016;25:1395–1403.
19. Mine K, Nakayama T, Milanese S, Grimmer K: Effectiveness of stretching on posterior shoulder tightness and glenohumeral internal-rotation deficit: A systematic review of randomized controlled trials. J Sport Rehabil 2017;26:294–305.
20. Cools AM, Johansson FR, Cagnie B, Cambier DC, Witvrouw EE: Stretching the posterior shoulder structures in subjects with internal rotation deficit: Comparison of two stretching techniques. Shoulder Elbow 2012;4:56–63.
21. Wilk KE, Reinold MM, Macrina LC, et al: Glenohumeral internal rotation measurements differ depending on stabilization techniques. Sports Health 2009;1:131–136.
22. Portney LG, Watkins MP: Foundations of Clinical Research: Applications to Practice, ed 3. Upper Saddle River, NJ, Prentice-Hall, 2000.
23. Mullaney MJ, McHugh MP, Johnson CP, Tyler TF: Reliability of shoulder range of motion comparing a goniometer to a digital level. Physiother Theory Pract 2010;26:327–333.
24. Pappas AM, Zawacki RM, McCarthy CF: Rehabilitation of the pitching shoulder. Am J Sports Med 1985;13:223–235.
25. Sher JS, Uribe JW, Posada A, Murphy BJ, Zlatkin MB: Abnormal findings on magnetic resonance images of asymptomatic shoulders. J Bone Joint Surg 1995;77:10–15.
26. Reinold MM, Gill TJ: Current concepts in the evaluation and treatment of the shoulder in overhead-throwing athletes, part 1: Physical characteristics and clinical examination. Sports Health 2010;2:39–50.
27. Fortenbaugh D, Fleisig GS, Andrews JR: Baseball pitching biomechanics in relation to injury risk and performance. Sports Health 2009;1:314–320.
29. Sauers EL, Huxel Bliven KC, Johnson MP, Falsone S, Walters S: Hip and glenohumeral rotational range of motion in healthy professional baseball pitchers and position players. Am J Sports Med 2014;42:430–436.
30. Oliver G, Plummer H, Johnson R, Holt T, Henning L, Weimar W: Association of hip range of motion and upper extremity kinetics in youth baseball pitching. Br J Sports Med 2014;48:646.
31. Picha KJ, Harding JL, Bliven KC: Glenohumeral and hip range-of-motion and strength measures in youth baseball athletes. J Athl Train 2016;51:466–473.
32. Zeppieri G, Lentz TA, Moser MW, Farmer KW: Changes in hip range of motion and strength in collegiate baseball pitchers over the course of a competitive season: A pilot study. Int J Sports Phys Ther 2015;10:505–513.
33. Scher S, Anderson K, Weber N, Bajorek J, Rand K, Bey MJ: Associations among hip and shoulder range of motion and shoulder injury in professional baseball players. J Athl Train 2010;45:191–197.
34. Gamma SC, Baker RT, Iorio S, Nasypany A, Seegmiller JG: A total motion release warm-up improves dominant arm shoulder internal and external rotation in baseball players. Int J Sports Phys Ther 2014;9:509–517.
35. MacWilliams BA, Choi T, Perezous MK, Chao EYS, McFarland EG: Characteristic ground-reaction forces in baseball pitching. Am J Sports Med 1998;26:66–71.
36. Chalmers PN, Wimmer MA, Verma NN, et al: The relationship between pitching mechanics and injury: A review of current concepts. Sport Health 2017;9:216–221.