international journal of athletic therapy & training november 2011 21

© 2011 Human Kinetics - IJATT 16(6), pp. 21-25

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 suc-cess. The inherent instability of the shoulder makes baseball players highly susceptible to injury, and ado-lescent 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 dem-onstrated 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 funda-mental 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

Joe J. Piccininni, EdD, CAT(C), Report Editor

Plyometric Supraspinatus Strengthening in High School Baseball Players

INJURY PREVENTION & PERFORMANCE ENHANCEMENT

Matthew J. Somma, PT, DPT, CSCS • OA Center for Orthopaedics and Travis L. Orth, PT, MS, DPT • Therapeutic Associates, Inc.

pitches thrown during a game or season and regulation of the types of pitches thrown.4,5

Research has demonstrated that proper prepara-tion 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, infraspina-tus, 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 acro-mion are associated with muscular weakness.16 Supra-spinatus 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 preven-tion of throwing injuries in baseball players.

Plyometric exercises, which involve rapid transi-tions from eccentric to concentric muscle contractions, have been advocated for rotator cuff strengthening.19 Rapid transition in contraction mode during the stretch-shortening cycle is believed to enhance muscle reac-tive capabilities that improve dynamic joint stability.20 Plyometric training regimens often use medicine balls for performance of exercises that replicate the eccen-tric and concentric forces associated with pitching.

C

22 november 2011 international journal of athletic therapy & training

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 supra-spinatus muscle. We examined the effectiveness of the “Ballistic Six” for strengthening of the supraspinatus musculature in high school baseball players.

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 dyna-mometry is an accepted method for determination of upper extremity strength.24-28 The two pretraining strength assessments were averaged to establish base-line 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 princi-pal 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.

DiscussionNumerous 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 supra-spinatus muscle is particularly susceptible to injury.17,18

Table 1. Progression of the Ballistic Six Exercise Program

Phase Volume IntensityWeeks 1-4

3 sets of 10 repeti-tions, 30 seconds rest between sets

2.2-lb ball for one-handed throws6 lb-ball for two-handed throws

Weeks 5-7

3 sets of 15 repeti-tions, 30 seconds rest between sets

2.2-lb ball for one-handed throws8-lb ball for two-handed throws

Weeks 8-10

3 sets of 20 repeti-tions, 30 seconds rest between sets

2.2-lb ball for one-handed throws10-lb ball for two-handed throws

Figure 1 positioning for hand-dynamometer measurement of supra-spinatus strength.

international journal of athletic therapy & training november 2011 23

Table 2. Athletes Demonstrating an Increase in Supraspinatus Strength

PlayerPretraining Strength Trial 1

Pretraining Strength Trial 2

Pretraining Strength Mean of Trials 1 & 2

Posttraining Strength

Pre- to Post-training 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

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 weighted-ball toss, (f) acceleration toss of weighted-ball.

24 november 2011 international journal of athletic therapy & training

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 adoles-cent 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 supraspi-natus muscle,31-33 but none of them involved multidi-rectional 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 plyo-metric 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 train-ing 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 pro-gram 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.

ConclusionThe results of this pilot study suggests that supraspi-natus 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.

End Note

A detailed Study Methods file for this study can be found on the IJATT website under Extras.

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20. Komi PV. Stretch-shortening cycle: a powerful model to study normal and fatigued muscle. J Biomech. 2000;33:1197-2006.

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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.

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32. Reinold MM, Macrina LC, Wilk KE, et al. Electromyographic analysis of the supraspinatus and deltoid muscles during 3 common rehabilita-tion exercises. J Athl Train. 2007;42:464-469.

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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 Associ-ates Inc. in Seattle, WA.

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