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INJURY PREVENTION & PERFORMANCE ENHANCEMENT Joe J. Piccininni, EdD, CAT(C), Report Editor Plyometric Supraspinatus Strengthening in High School Baseball Players Matthew J. Somma, PT, DPT, CSCS • OA Center for Orthopaedics and Travis L. Orth, PT, MS, DPT • Therapeutic Associates, Inc. C omplex coordination of numerous muscle contractions is required to effectively throw a baseball. The complexity of the task is heightened during a game, during which the velocity and location of the pitch determine success. The inherent instability of the shoulder makes baseball players highly susceptible to injury, and adolescent players are especially susceptible.1 Shoulder injuries in baseball range in severity from general tenderness to Little Leaguer’s shoulder, which involves a stress fracture of the proximal humeral epiphysis.2,3 Such injuries are often associated with overuse and pitching while fatigued.4 Previous research has demonstrated that type of pitch, number of pitches thrown per game, and number of pitches thrown during the season can contribute to shoulder pain in youth baseball pitchers.5 Fleisig et al.6 reported that fundamental pitching mechanics remain constant during progression through youth, high school, college, and professional levels of competition, but joint forces increase as an athlete matures. Thus, players at high levels of competition possess elevated risk for injury. Fortunately, increasing strength as the body matures can help prevent such injuries. The incidence rate of injuries requiring medical intervention in adolescent baseball players appears to be increasing,7 which is believed to be associated with an increase in both the intensity and frequency of competition.8 Many overuse shoulder injuries do not develop until the mid to late teens (i.e., high school age).9Guidelines for injury prevention in baseball have been focused on limitation of the total number of pitches thrown during a game or season and regulation of the types of pitches thrown.4,5 Research has demonstrated that proper preparation and strengthening of the shoulder musculature can prevent injuries in throwing athletes.7,10-12 Many of the training programs developed exclusively for baseball players have focused on strengthening the rotator cuff muscles (i.e., subscapularis, supraspinatus, infraspinatus, and teres minor),13,14 which dynamically stabilize the glenohumeral joint.15 The supraspinatus tendon is especially vulnerable to injury during performance of the throwing motion due to its anatomical proximity to the inferior surface of the acromion. Both overuse tendinosis and also impingement of the supraspinatus tendon between the head of the humerus and the acromion are associated with muscular weakness.16 Supraspinatus weakness has been related to the incidence of shoulder injury in professional baseball players.17 Yanagisawa et al.18 identified increased MRI signal intensity in the supraspinatus muscle after a pitching session. Thus, adequate strength of the supraspinatus muscle appears to be an important factor for prevention of throwing injuries in baseball players. Plyometric exercises, which involve rapid transitions from eccentric to concentric muscle contractions, have been advocated for rotator cuff strengthening.19 Rapid transition in contraction mode during the stretchshortening cycle is believed to enhance muscle reactive capabilities that improve dynamic joint stability.20 Plyometric training regimens often use medicine balls for performance of exercises that replicate the eccentric and concentric forces associated with pitching. © 2011 Human Kinetics - IJATT 16(6), pp. 21-25 international journal of Athletic Therapy & training november 2011 21 Despite widespread use of plyometric training, very little research has been done to assess the effectiveness of such programs. The “Ballistic Six” is a sport-specific plyometric training program designed to strengthen the rotator cuff muscles in the throwing athlete.21 Carter et al.22 found that this program significantly improved throwing velocity in college baseball players, but the strength increase that resulted was not significantly greater than that observed in players who performed an alternate off-season strengthening program that involved elastic resistance and dumbbells, and they did not specifically assess strength increase in the supraspinatus muscle. We examined the effectiveness of the “Ballistic Six” for strengthening of the supraspinatus musculature in high school baseball players. Discussion Numerous studies have documented that high school baseball players are at high risk for the occurrence of a shoulder injury,2,8,29 which is primarily due to the ballistic nature of the throwing motion.6,15 The supraspinatus muscle is particularly susceptible to injury.17,18 Procedures and Findings Four high school baseball players were recruited from two high schools in Portland, Maine: one catcher, one pitcher, one infielder, and one outfielder (average 16.25 years of age, 174.1 cm height, 71.4 kg weight). Three of the participants played at the varsity level and one was on a freshman baseball team. One participant who was also engaged in a separate off-season program of exercises and baseball pitching was dismissed after shoulder fatigue precluded continued participation in the “Ballistic Six” training program. Hand-held dynamometry was used to obtain two pretraining assessments of the supraspinatus strength that were at least seven days apart (Figure 1). Kelly et al.23 demonstrated that isolated activation of the supraspinatus muscle is best achieved in a position of 90 degrees of scapular elevation and 45 degrees of glenohumeral external rotation, and hand-held dynamometry is an accepted method for determination of upper extremity strength.24-28 The two pretraining strength assessments were averaged to establish baseline strength level, after which participants completed a 10-week training program (Table 1).The “Ballistic Six” program consists of six plyometric exercises that are performed two times per week (Figure 2).21 Each exercise session was supervised by the principal investigators to ensure program completion and to monitor participant safety. A single post-training strength assessment was performed within one week of completion of the 10-week training program. All three of the athletes demonstrated an increase in supraspinatus strength (Table 2), which averaged 4.28 kg of increased force output. 22 november 2011 Figure 1 Positioning for hand-dynamometer measurement of supraspinatus strength. Table 1. Progression of the Ballistic Six Exercise Program Phase Volume Intensity Weeks 1-4 3 sets of 10 repetitions, 30 seconds rest between sets 2.2-lb ball for onehanded throws 6 lb-ball for twohanded throws Weeks 5-7 3 sets of 15 repetitions, 30 seconds rest between sets 2.2-lb ball for onehanded throws 8-lb ball for twohanded throws Weeks 8-10 3 sets of 20 repetitions, 30 seconds rest between sets 2.2-lb ball for onehanded throws 10-lb ball for twohanded throws international journal of Athletic Therapy & training Figure 2 Components of the “Ballistic Six” exercise program: (a) external rotation in adducted position against elastic resistance, (b) external rotation exercise in abducted position against elastic resistance, (c) overhead weighted-ball toss, (d) externally rotating weighted-ball toss, (e) deceleration catch of weightedball toss, (f) acceleration toss of weighted-ball. Table 2. Athletes Demonstrating an Increase in Supraspinatus Strength Player Pretraining Strength Trial 1 Pretraining Strength Trial 2 Pretraining Strength Mean of Trials 1 & 2 Pre- to Posttraining Posttraining Strength Strength Change 1 10.85 8.05 9.45 13.40 3.95 S2 6.10 7.10 6.60 12.95 6.35 3 10.55 10.05 10.30 13.15 2.85 international journal of Athletic Therapy & training november 2011 23 Trakis et al.12 reported that adolescent baseball pitchers with shoulder pain demonstrated less supraspinatus strength compared to those without pain and suggested that it might result from repetitive eccentric loading. They also suggested that prophylactic strengthening of the rotator cuff muscles might prevent injury in adolescent baseball players. Weakness of the supraspinatus in professional baseball players has been associated with elevated risk for in-season throwing-related shoulder injuries that require surgical intervention.30 Several studies have assessed the effectiveness of different exercises for strengthening of the supraspinatus muscle,31-33 but none of them involved multidirectional functional movement patterns that replicate components of the baseball throwing action. The “Ballistic Six” program was designed to replicate the stresses imposed by throwing a baseball through plyometric exercises, which have been shown to be very effective for realization of strength gains.34 Carter et al.22 examined the effect of an 8-week “Ballistic Six” exercise program on pitch velocity, as well as internal and external rotation strength, in collegiate baseball players, but the strength measurements did not isolate the force output of the supraspinatus muscle. The exercise program we administered closely followed the progression described by Pretz.21 The players were encouraged to perform both single-arm and double-arm throwing exercises with the greatest amount of force possible, without compromising form. Each athlete was closely monitored during each training session to ensure compliance with proper exercise performance technique, with verbal cues provided when necessary to correct improper form. An advantage of this program is the minimal amount of equipment that is required. The entire program can be completed with resistive elastic tubing material and four weighted balls (2.2-lb, 6-lb, 8-lb, and 10-lb). The exercises can be performed by pairs of athletes, with one player throwing the weighted ball while the second player monitors form and tosses the weighted ball back to the exercise partner. Conclusion The results of this pilot study suggests that supraspinatus muscle strength can be improved through a 10-week, sport-specific, plyometric training program, which may reduce the risk of shoulder injuries in male high school baseball players. 24 november 2011 End Note A detailed Study Methods file for this study can be found on the IJATT website under Extras. References 1.Radelet MA, Lephart SM, Rubinstein EN, et al. Survey of the injury rate for children in community sports. Pediatrics. 2002;110:e28. 2.Paterson PD, Waters PM. Shoulder injuries in the childhood athlete. Clin Sports Med. 2000;19:681-692. 3.Carson WG, Gasser SI. Little leaguer’s shoulder: a report of 23 cases. Am J Sports Med. 1998;26:575-580. 4.Olsen SJ, Fleisig GS, Dun S, et al. Risk factors for shoulder and elbow injuries in adolescent baseball pitchers. Am J Sports Med. 2006;34:905912. 5.Lyman S, Fleisig GS, Andrews JR, et al. Effect of pitch type, pitch count, and pitching mechanics on risk of elbow and shoulder pain in youth baseball pitchers. Am J Sports Med. 2002;30:463-468. 6.Fleisig GS, Barrentine SW, Zheng N, et al. Kinematic and kinetic comparison of baseball pitching among various levels of development. J Biomech. 1999;32:1371-1375. 7.Andrews JR, Fleisig GS. Preventing throwing injuries. J Orthop Sports Phys Ther. 1998; 27:187-188. 8.Paterson PD, Waters PM. Shoulder injuries in the childhood athlete. Clin Sports Med. 2000;19:681-692. 9.Albright JA, Jokl P, Shaw R, et al. Clinical study of baseball pitchers: correlation of injury to the throwing arm with method of delivery. Am J Sports Med. 1978;6:15-21. 10.Park SS, Loebenberg ML, Rokito AS, et al. The shoulder in baseball pitching: biomechanics and related injuries – part 1. Hosp Joint Dis. 2002-2003;61:68-78. 11.Park SS, Loebenberg ML, Rokito AS, et al. The shoulder in baseball pitching: biomechanics and related injuries – part 2. Hosp Joint Dis. 2002-2003;61:80-88. 12.Trakis JE, McHugh MP, Caracciolo PA, et al. Muscle strength and range of motion in adolescent pitchers with throwing-related pain: implications for injury prevention. Am J Sports Med. 2008;36:2173-2178. 13.Szymanski DJ. Collegiate baseball in-season training. Strength Cond J. 2007;29:68-80. 14.Jeran JJ, Chetlin RD. Training the shoulder complex in baseball pitchers: a sport-specific approach. Strength Cond J. 2005;27:14-31. 15.Mazoue CG, Andrews JR. Injuries to the shoulder in athletes. South Med. 2004;97:748-754. 16.Braun S, Kokmeyer D, Millett PJ. Shoulder injuries in the throwing athlete. J Bone Joint Surg Am. 2009;91:966-978. 17.Byram IR, Bushnell BD, Dugger K, et al. Preseason shoulder strength measurements in professional baseball pitchers: identifying players at risk for injury. Am J Sports Med. 2010;38:1375-1382. 18.Yanagisawa O, Niitsu M, Takahashi H, et al. Magnetic resonance imaging of the rotator cuff muscles after baseball pitching. J Sports Med Phys Fitness. 2003;43:493-499. 19.Wilk KE, Arrigo C. Current concepts in the rehabilitation of the athletic shoulder. J Orthop Sports Phys Ther. 1993;18:365-378. 20.Komi PV. Stretch-shortening cycle: a powerful model to study normal and fatigued muscle. J Biomech. 2000;33:1197-2006. 21.Pretz R, “Ballistic six” plyometric training for the overhead throwing athlete. Strength Cond J. 2004;26:62-66. 22.Carter AB, Kaminski TW, Douex AT, et al. Effects of high volume upper extremity plyometric training on throwing velocity and functional strength ratios of the shoulder rotators in collegiate baseball players. J Strength Cond Res. 2007;21:208-215. international journal of Athletic Therapy & training 23.Kelly BT, Kadrmas WR, Speer KP. The manual muscle examination for rotator cuff strength. An electromyographic investigation. Am J Sports Med. 1996;24:581-588. 24.Sullivan SJ, Chesley A, Hebert G, et al. The validity and reliability of hand-held dynamometry in assessing isometric external rotator performance. J Orthop Sports Phys Ther. 1988;10(6):213-217. 25.Magnusson SP, Gleim GW, Nicholas JA. Subject variability of shoulder abduction strength testing. Am J Sports Med. 1990;18(4):349-353. 26.Kolber MJ, Cleland JA. Strength testing using hand-held dynamometry. Phys Ther Rev. 2005;10:99-112. 27.Donatelli R, Ellenbecker TS, Ekedahl SR et al. Assessment of shoulder strength in professional baseball pitchers. J Orthop Sports Phys Ther. 2000;30(9):544-551. 28.Bohannon RW, Saunders N. Hand-held dynamometry: a single trial may be adequate for measuring muscle strength in healthy individuals. Physiothe Can. 1990;42(1):6-9. 29.Wilk KE, Meister K, Andrews JR. Current concepts in the rehabilitation of the overhead throwing athlete. Am J Sports Med. 2002;30:136-151. 30.Byram IR, Bushnell BD, Dugger K et al. Preseason shoulder strength measurements in professional baseball pitchers: identifying players at risk for injury. Am J Sports Med. 2010;38:1375-1382. 31.Boettcher CE, Ginn KA, Cathers I. Which is the optimal exercise to strengthen supraspinatus? Med Sci Sports Exerc. 2009;41:1979-1983. 32.Reinold MM, Macrina LC, Wilk KE, et al. Electromyographic analysis of the supraspinatus and deltoid muscles during 3 common rehabilitation exercises. J Athl Train. 2007;42:464-469. 33.Takeda Y, Kashiwaguchi S, Endo K. The most effective exercise for strengthening the supraspinatus muscle: evaluation by magnetic resonance imaging. Am J Sports Med. 2002;30:374-381. 34.Saez-Saez de Villarreal E, Reguena B, Newton RU. Does plyometric training improve strength performance? A meta-analysis. J Sci Med Sport. 2010;13:513-522. Matthew Somma is a staff physical therapist with OA Center for Orthopaedics in Saco, ME. Travis Orth is a staff physical therapist, Seattle PT, Therapeutic Associates Inc. in Seattle, WA. Don’t miss a single issue! Frequency: Bimonthly (January, March, May, July, September, November) ISSN (print): 2157-7277 ISSN (online): 2157-7285 International Journal of Athletic Therapy & Training (IJATT) is dedicated to the unique needs of athletic trainers and therapists. IJATT provides insights into professional practice issues, highlights sports health care techniques, shares experiential knowledge, and presents practical applications of current research. IJATT strives to present these subjects in a simple, streamlined format that focuses on clinical applications and athlete and patient care practices. IJATT is also available in an online format that offers the same great content available in the print edition with all the convenience of electronically formatted material. HUMAN KINETICS www.ATT-Journal.com Vist the new website! ______ I already subscribe to IJATT. 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