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0363-5465/102/3030-0136$02.00/0 THE AMERICAN JOURNAL OF SPORTS MEDICINE, Vol. 30, No. 1 © 2002 American Orthopaedic Society for Sports Medicine

Current Concepts Current Concepts in the Rehabilitation of the Overhead Throwing Athlete

Kevin E. Wilk,* PT, Keith Meister, MD, and James R. Andrews,§ MD From *HealthSouth Rehabilitation Corporation and American Sports Medicine Institute, Birmingham, Alabama, Tampa Bay Devil Rays Baseball Team, Tampa Bay, Florida, Department of Orthopaedics, Division of Sports Medicine, University of Florida, Gainesville, Florida, and §Alabama Sports Medicine and Orthopaedic Center, Birmingham, Alabama

ABSTRACT

The overhead throwing motion is an extremely skillful and intricate movement that is very stressful on the shoulder joint complex. The overhead throwing athlete places extraordinary demands on this complex. Excessively high stresses are applied to the shoulder joint because of the tremendous forces generated by the thrower. The thrower's shoulder must be lax enough to allow excessive external rotation, but stable enough to prevent symptomatic humeral head subluxations, thus requiring a delicate balance between mobility and functional stability. We refer to this as the "thrower's paradox." This balance is frequently compromised, which leads to injury. Numerous types of injuries may occur to the surrounding tissues during overhead throwing. Frequently, injuries can be successfully treated with a well-structured and carefully implemented nonoperative rehabilitation program. The key to successful nonoperative treatment is a thorough clinical examination and accurate diagnosis. Athletes often exhibit numerous adaptive changes that develop from the repetitive microtraumatic stresses observed during overhead throwing. Treatment should focus on the restoration of these adaptations during the rehabilitation program. In this article, the typical musculoskeletal profile of the overhead thrower and various rehabilitation programs for specific injuries are discussed. Rehabilitation follows a structured, multiphase approach with emphasis on controlling inflammation, restoring muscle balance, improving soft tissue flexibility, enhancing proprioception and neuromuscular control, and efficiently returning the athlete to competitive throwing.

The repetitive microtraumatic stresses placed on the athlete's shoulder joint complex during the throwing motion challenge the physiologic limits of the surrounding tissues. Frequently, alterations in throwing mechanics, muscle fatigue, muscle weakness or imbalance, and excessive capsular laxity may lead to tissue breakdown and injury. These injuries frequently involve the glenohumeral capsule, glenoid labrum, and the rotator cuff musculature. It has been our experience that most injuries to the thrower's shoulder can be effectively treated with a proper nonoperative rehabilitation program. Generally, the rehabilitation program consists of activity modification, flexibility exercises, strengthening exercises, and a gradual return to throwing activities. In part one of his "Current Concepts" series, Meister 64 described a four-group classification system to categorize shoulder injuries in the overhead throwing athlete. We will discuss the rehabilitation program for each of the classifications. Bison and Andrews10 have also offered a classification system for injuries to the thrower's shoulder. Each of these abnormalities develops because of unique etiologic factors. On the basis of these etiologic factors and the clinical examination, a proper rehabilitation program can be developed for each category. The key to effective treatment is a thorough clinical examination and appropriate differential diagnosis. In this article, we will discuss a typical nonoperative rehabilitation program for various shoulder injuries that have been discussed in the previous two articles.

Address correspondence and reprint requests to Kevin E. Wilk, PT, HealthSouth Rehabilitation Corporation, 1201 11th Avenue South, Suite 100, Birmingham, AL 35202. No author or related institution has received financial benefit from research in this study.

REHABILITATION OVERVIEW

Before the specifics of the rehabilitation program can be discussed, a thorough understanding of the clinical exam136

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ination of the shoulder joint complex must be established. The evaluation of the thrower's shoulder has been discussed in part two of the series by Meister.63 The physician must evaluate the thrower to establish a differential diagnosis, then the physical therapist or athlete trainer must evaluate the thrower to establish a list of physical limitations or problems that may be contributing to or resulting from the disorder. The rehabilitation specialist must evaluate range of motion, muscle strength, laxity, and proprioception. In addition, the rehabilitation specialist should address the athlete's throwing program, exercise schedule, and throwing mechanics. Once these areas have been assessed, a comprehensive rehabilitation program can be established. Furthermore, during the evaluation process, the clinician must have an understanding of what is considered to be the "normal" or acceptable physiologic characteristics for the overhead throwing population. The purpose of the following sections is to convey to the reader the typical physical characteristics of the overhead throwing athlete. Specific range of motion, strength, laxity, and proprioceptive characteristics exhibited in throwing athletes will be discussed. The clinician must possess a complete understanding of what is typical for this unique athletic population so that abnormalities or differences can be appropriately identified and addressed. Range of Motion Most throwers exhibit an obvious motion disparity whereby external rotation is excessive and internal rotation is limited at 90° of abduction.8, 15, 47, 92 Several investigators have documented that pitchers exhibit greater external rotation of the shoulder than do position players.8, 47, 93 Brown et al.15 reported that professional pitchers exhibited 141° 15° of shoulder external rotation measured at 90° of abduction. This was approximately 9° more than the nonthrowing shoulder, and approximately 9° more than the throwing shoulder of position players measured in 90° of abduction. Recently, Bigliani et al.8 examined the range of motion of 148 professional players. The investigators reported that the pitchers' external rotation at 90° of abduction averaged 118° (range, 95° to 145°) in the dominant shoulder, whereas the position players' dominant shoulder averaged 108° (range, 80° to 105°). In an ongoing study of professional baseball players, Wilk and Arrigo (unpublished data, 2000) assessed the range of shoulder motion of 372 professional baseball players. We have noted that pitchers exhibit an average of 129.9° 10° of external rotation and 62.6° 9° of internal rotation when passively assessed at 90° of abduction. In pitchers, the external rotation is approximately 7° greater in the throwing shoulder when compared with the nonthrowing shoulder, while internal rotation is 7° greater in the nonthrowing shoulder. In addition, the total motion (external rotation and internal rotation added together) in the throwing shoulder is equal (within 5°) when compared with the nonthrowing shoulder. This was consistent in all 372 baseball players. We refer to this as the "total motion concept" (Fig. 1). We have also noted that pitchers exhibit

Fig. 1. The total motion concept: ER IR ER, external rotation; IR, internal rotation.

total motion.

the greatest total arc of motion; that is, external and internal rotation at 90° of abduction, followed closely by catchers, then outfielders, and finally infielders. Furthermore, when comparing left-handed with right-handed pitchers, the left-handed throwers exhibit approximately 7° more external rotation and 12° more total motion when compared with right-handed throwers. These findings were statistically significant (P 0.01). Laxity Most throwers exhibit significant laxity of the glenohumeral joint, which permits excessive range of motion. The hypermobility of the thrower's shoulder has been referred to as "thrower's laxity." 92 The laxity of the anterior and inferior glenohumeral joint capsule may be appreciated by the clinician during the stability assessment of the overhead thrower's shoulder joint. Some clinicians have reported that the excessive laxity exhibited by the thrower is the result of repetitive throwing and they have referred to this as "acquired laxity" (J. R. Andrews, unpublished data, 1996), while others have documented that the overhead thrower exhibits congenital laxity.8 Bigliani et al.8 examined laxity in 72 professional baseball pitchers and 76 position players. The investigators noted a high degree of inferior glenohumeral joint laxity, with 61% of pitchers and 47% of position players exhibiting a positive sulcus sign in the throwing shoulder. Additionally, in the players who also exhibited a positive sulcus sign in the dominant shoulder, 89% of the pitchers and 100% of the position players exhibited a positive sulcus sign in the nondominant shoulder. Thus, it would appear that some baseball players exhibit inherent or congenital laxity, with superimposed acquired laxity, as a result of adaptive changes from throwing.

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Wilk et al. TABLE 1 Glenohumeral Muscular Strength Values (in percent) in Professional Baseball Playersa

180 deg/s 300 deg/s 450 deg/s

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Bilateral comparisons External rotation Internal rotation Abduction Adduction Unilateral muscle ratios External/internal rotation Abduction/adduction External rotation/abduction Isokinetic torque/body weight ratios External rotation Internal rotation Abduction Adduction

a

95­109 105­120 100­110 120­135 63­70 82­87 64­69

85­95 100­115 100­110 115­130 65­72 92­97 66­71

80­80 100­110

62­70

18­23 27­33 26­32 32­36

15­20 25­30 20­26 28­33

Data condensed from Wilk et al.94,96

Muscle Strength Several investigators have examined muscle strength parameters in the overhead throwing athlete with varying results and conclusions.1, 7, 15, 20, 22, 39, 89, 91 Wilk et al.89, 91 performed isokinetic testing on professional baseball players as part of their physical examinations during spring training. The investigators demonstrated that the external rotation strength of the pitcher's throwing shoulder is significantly weaker (P 0.05) than the nonthrowing shoulder, by 6%. Conversely, internal rotation strength of the throwing shoulder was significantly stronger (P 0.05), by 3%, compared with the nonthrowing shoulder. In addition, adduction strength of the throwing shoulder is also significantly stronger than in the nonthrowing shoulder, by approximately 9% to 10%. We believe that an important isokinetic value is the unilateral muscle ratio, which describes the antagonist/agonist muscle strength ratio. A proper balance between agonist and antagonist muscle groups is thought to provide dynamic stabilization to the shoulder joint. To provide proper muscle balance,

the external rotator muscles should be at least 65% the strength of the internal rotator muscles.94 Optimally, the external-to-internal rotator muscles strength ratio should be 66% to 75%.91, 94, 96 This provides proper muscle balance. Table 1 illustrates the expected muscle strength values of professional baseball players. Magnusson et al.60 used a hand-held dynamometer to study the isometric muscle strength of professional pitchers and compared it with strength of a control group of nonthrowing, nonathletic persons. In pitchers, the supraspinatus muscle was significantly weaker on the throwing side compared with the nonthrowing side; this was tested by performing an isometric manual muscle test of the empty can maneuver. Additionally, pitchers were weaker than the control group of nonbaseball players for shoulder abduction, external rotation, internal rotation, and muscle strength of the supraspinatus muscle. The scapular muscles play a vital role during the overhead throwing motion.26 Proper scapular movement and stability are imperative for asymptomatic shoulder function.48, 49 These muscles work in a synchronized fashion and act as force couples about the scapula, providing both movement and stabilization. Wilk et al.97 documented the isometric scapular muscle strength values of professional baseball players. The results indicated that pitchers and catchers exhibited a significantly different strength increase of the protractor and elevator muscles of the scapula when compared with position players. All players (except infielders) exhibited significantly stronger depressor muscles of the scapula on the throwing side compared with the nonthrowing side. In addition, we believe that the agonist/antagonist muscle ratios are important values when considering how the scapula provides stability, mobility, and symptom-free function. Table 2 illustrates the scapular muscle strength values in the overhead throwing athlete.

Proprioception Proprioception is defined as the conscious or unconscious awareness of joint position, whereas neuromuscular con-

TABLE 2 Scapular Muscle Values and Their Unilateral Ratiosa

Scapular muscle values (in foot-pounds) Protraction D ND D Retraction ND D Elevation ND D Depression ND

Pitchers Catchers Position players

71 68 58

10 10 10

74 73 58

13 10 11

62 63 57

8 5 6

60 59 56

7 7 6

83 88 65

14 15 12

84 85 66

5 8 11

22 21 19

6 4 5

18 16 18

5 5 5

Unilateral muscle ratios (in percent) Protraction/Retraction D ND D Elevation/Depression ND

Pitchers Catchers Position players

a

87 93 98

81 81 94

27 24 29

21 19 27

D, dominant; ND, nondominant.

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trol is the efferent motor response to afferent (sensory) information.53 The thrower relies on enhanced proprioception to influence the neuromuscular system to dynamically stabilize the glenohumeral joint in the presence of significant capsular laxity and excessive range of motion. Allegrucci et al.2 tested the shoulder proprioception in 20 healthy overhead throwing athletes participating in various sports. Testing of joint proprioception was performed on a motorized system with the subject attempting to reproduce a specific joint angle. The investigators noted that the dominant shoulder exhibited diminished proprioception compared with the nondominant shoulder. The investigators also noted improved proprioception near the end range of motion when compared with the starting point. Blasier et al.12 reported that, in persons with clinically determined generalized joint laxity, the laxity is significantly less sensitive during proprioceptive testing. Wilk et al. (unpublished data, 2000) studied the proprioceptive capability of 120 professional baseball players. The investigators passively positioned the player's arm at a documented point within the player's external rotation range of motion. The athlete was then instructed to actively reposition the shoulder in the same position. The researchers noted no significant difference between the throwing shoulder and nonthrowing shoulder. In addition, Wilk et al. (unpublished data, 2000) compared the proprioceptive ability of 60 professional baseball players with that of 60 nonoverhead throwing athletes. The investigators noted no significant differences between baseball players and the others. However, baseball players exhibited slightly improved proprioceptive abilities at external rotation end range of motion compared with nonoverhead athletes, but these results were not significantly different.

TABLE 3 Rehabilitation of the Overhead Thrower--Phases and Goals Phase one--acute phase Goals Diminish pain and inflammation Normalize motion Retard muscular atrophy Reestablish dynamic stability (muscular balance) Control functional stress/strain Exercises and modalities: Cryotherapy, ultrasound, electrical stimulation Flexibility and stretching for posterior shoulder muscles (improve internal rotation and horizontal adduction) Rotator cuff strengthening (especially external rotator muscles) Scapular muscles strengthening (especially retractor, protractor, depressor muscles) Dynamic stabilization exercises (rhythmic stabilization) Closed kinetic chain exercises Proprioception training Abstain from throwing Phase two--intermediate phase Goals Progress strengthening exercise Restore muscular balance (external/internal rotation) Enhance dynamic stability Control flexibility and stretches Exercises and modalities Continue stretching and flexibility (especially internal rotation and horizontal adduction) Progress isotonic strengthening Complete shoulder program Thrower's Ten program Rhythmic stabilization drills Initiate core strengthening program Initiate leg program Phase three--advanced strengthening phase Goals Aggressive strengthening Progress neuromuscular control Improve strength, power, and endurance Initiate light throwing activities Exercises and modalities Flexibility and stretching Rhythmic stabilization drills Thrower's Ten program Initiate plyometric program Initiate endurance drills Initiate short-distance throwing program Phase four--return-to-activity phase Goals Progress to throwing program Return to competitive throwing Continue strengthening and flexibility drills Exercises Stretching and flexibility drills Thrower's Ten program Plyometric program Progress interval throwing program to competitive throwing

THE REHABILITATION PROGRAM FOR THE OVERHEAD THROWER

The nonoperative rehabilitation program used for treatment of shoulder injuries to the overhead thrower involves a multiphased approach that is progressive and sequential. The specific goals of each of the four phases of the program are outlined in Table 3. Each phase represents a progression from the prior phase: the exercises become more aggressive and demanding, and the stresses applied to the shoulder joint gradually increase. We will briefly discuss the specific rehabilitation exercises and drills that we use to treat the overhead throwing athlete. There are 10 rehabilitation principles that we follow when treating a throwing athlete. These principles are shown in Table 4. Phase One--Acute Phase The primary goals of the initial rehabilitation phase are to improve flexibility, reestablish baseline dynamic stability, normalize muscle balance, and restore proprioception without causing shoulder irritation or pain. One of the goals--to diminish the athlete's pain and inflammation--is accomplished through the use of local therapeutic

modalities such as ice, ultrasound, and electrical stimulation. In addition, the athlete's activities (such as throwing and exercises) must be modified to a pain-free level. The thrower is often instructed to abstain from throwing until advised by the physician or rehabilitation specialist. Additionally, active-assisted motion exercises have been shown to assist in reducing the athlete's pain.69 Another essential goal during the first phase of rehabil-

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Wilk et al. TABLE 4 Principles of Rehabilitation in the Thrower

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1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Never overstress healing tissue Prevent negative effects of immobilization Emphasize external rotation muscular strength Establish muscular balance Emphasize scapular muscle strength Improve posterior shoulder flexibility (internal rotation range of motion) Enhance proprioception and neuromuscular control Establish biomechanically efficient throwing Gradually return to throwing activities Use established criteria to progress

itation is to normalize shoulder motion, particularly shoulder internal rotation and horizontal adduction. It is common for the overhead thrower to exhibit a significant loss of internal rotation. This may be due to soft tissue tightness, which may be from muscle inflexibility due to significant and repetitive eccentric muscle forces during arm deceleration. If the posterior soft tissue structures such as the infraspinatus and teres minor muscles are tight, increased anterior translation of the humeral head may result.35 Therefore, the thrower should perform specific stretches and flexibility exercises for the benefit of the posterior rotator cuff muscles. We believe that the loss of internal rotation is due to osseous adaptation of the humerus and posterior muscle tightness.21 We do not believe that the loss of internal rotation is routinely due to posterior capsular tightness. It appears that most throwers exhibit significant posterior laxity when evaluated.21 Thus, to improve internal rotation motion and flexibility, we prefer the stretches illustrated in Figures 2 and 3. These stretches are performed to maintain the flexibility of the posterior musculature, which may become tight because of the muscle contraction during the deceleration phase of throwing. We do not recommend performing stretches for the capsule unless the capsule has been shown on clinical examination to be excessively hypomobile. The rehabilitation specialist, in addition to helping restore glenohumeral motion, should assess the resting position and mobility of the scapula. Frequently, we have seen overhead throwers who exhibit a posture of rounded shoulders and a forward head. This posture may lead to muscle weakness of the scapular retractor muscles due to prolonged elongation or sustained stretches. In addition, the scapula may often appear protracted and anteriorly tilted. An anteriorly tilted scapula has been shown to contribute to subacromial impingement.58 In overhead throwers, we have seen this scapular position abnormality correlate to pectoralis minor muscle tightness and lower trapezius muscle weakness. Tightness of the pectoralis minor muscle can lead to axillary artery occlusion and neurovascular symptoms such as arm fatigue, pain, tenderness, and cyanosis.6, 70, 75, 78 The lower trapezius muscle is an important muscle in arm deceleration in that it controls scapular elevation and protraction.26 Weakness of the lower trapezius muscle may result in improper mechanics or shoulder symptoms. Thus, the rehabilitation

Figure 2. Internal rotation stretch: the arm is placed in the throwing position and passively stretched into internal rotation to stretch the external rotator muscles.

Figure 3. To improve posterior shoulder flexibility, the horizontal adduction stretch can be performed at 90° of shoulder abduction. The arm is horizontally adducted while the scapula is stabilized to enhance the posterior shoulder stretch. specialist should carefully assess the position, mobility, and strength of the overhead thrower's scapula. We routinely have throwers stretch their pectoralis minor muscle and strengthen the lower trapezius muscle and scapular retractor and protractor muscles. Additional primary goals of this first phase are to restore muscle strength, reestablish baseline dynamic stability, and restore proprioception. In this early phase of rehabilitation, the goal is to reestablish muscle balance.94, 96 Therefore, the focus is on improving the strength of the weak muscles such as the external rotator muscles, the supraspinatus muscle, and the scapular muscles.94, 96 The scapular muscles we routinely focus on in rehabilitation are the trapezius, serratus anterior, and rhomboid muscles. If the injured athlete is extremely sore or painful, submaximal isometric exercises should be employed; conversely, if the athlete exhibits minimal soreness,

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then lightweight isotonic exercises may be safely initiated. Additionally, during this phase we use rehabilitation exercise drills (see the next paragraph) that are designed to restore the neurosensory properties of the shoulder capsule that has experienced microtrauma and to enhance the sensitivity of the afferent mechanoreceptors.53, 55 Specific drills that restore neuromuscular control during this initial phase are rhythmic stabilization and reciprocal isometric muscle contractions for the internal/external rotator muscles of the shoulders. Additionally, proprioceptive neuromuscular facilitation patterns are used with rhythmic stabilization and slow reversal hold to reestablish proprioception and dynamic stabilization.51, 53, 55, 79, 93, 96 The purpose of these exercise drills is to facilitate agonist/antagonist muscle cocontractions. Efficient coactivation assists in restoring the balance in the force couples of the shoulder joint, thus enhancing joint congruency and joint compression.37 Padua et al.71 used proprioceptive neuromuscular facilitation patterns for 5 weeks and significantly improved their subjects' shoulder function and enhanced functional throwing performance test scores. Uhl et al.83 reported improved proprioception after specific neuromuscular training that challenged the glenohumeral musculature. Other exercise drills commonly used during this first rehabilitation phase include joint repositioning tasks52, 53, 54 and axial loading exercises (such as closed kinetic chain). Active joint compression stimulates the articular receptors.19, 52 Thus, axial loading exercise drills such as weight shifts, weight shifting on a ball, wall pushups, and quadruped positioning drills are beneficial in restoring proprioception.90, 92, 95 Phase Two--Intermediate Phase In phase two of the rehabilitation program, the primary goals are to progress the strengthening program, continue to improve flexibility, and facilitate neuromuscular control. During this phase, the rehabilitation program is progressed to more aggressive isotonic strengthening activities with emphasis on the restoration of muscle balance. Selective muscle activation is also used to restore muscle balance and symmetry. In the overhead thrower, the shoulder external rotator muscles, scapular retractor muscles, and protractor and depressor muscles are frequently isolated because of weakness. We have established a core exercise program for the overhead thrower that specifically addresses the vital muscles involved in the throwing motion.90, 98 This exercise program was developed on the basis of the collective EMG research of numerous investigators,11, 24, 30, 38, 45, 46, 56, 65, 66, 73, 81 and is referred to as the "Thrower's Ten Program ."90 Sidelying external rotation (Fig. 4) and prone rowing into external rotation (Fig. 5) have been shown to elicit the highest amount of EMG activity of the posterior rotator cuff muscles.30

Figure 4. External rotation with a dumbbell, with the patient lying on his side, is one of the exercises to increase external rotation strength. The scapula provides proximal stability to the shoulder joint, enabling distal segment mobility. Scapular stability is vital for normal asymptomatic arm function. Several authors have emphasized the importance of scapular muscle strength and neuromuscular control in contributing to normal shoulder function.23, 48, 49, 72 Isotonic exercise techniques are used to strengthen the scapular muscles. Furthermore, Wilk and Arrigo93 developed specific exercise drills to enhance neuromuscular control of the scapulothoracic joint. These exercise drills are designed to maximally challenge the scapulothoracic muscle force couples and to stimulate the proprioceptive and kinesthetic awareness of the scapula. These scapular neuromuscular control drills are illustrated in Figure 6. Another popular exercise used by athletes is the "empty can" exercise (Fig. 7). With this exercise movement, the arm is placed in the scapular plane with the hand placed

To request a copy of this four-page illustrated program, please write to the corresponding author.

Figure 5. Prone rowing into external rotation is another exercise to enhance external rotation strength.

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Figure 7. The empty can exercise movement. This exercise can produce pain in some athletes. For this exercise, the subject elevates the arm in the plane of the scapula with the thumb pointed downward. The hand position appears to resemble that of emptying a can, hence comes the name of the exercise.

Figure 6. Neuromuscular control exercise drill for the scapular muscles: the athlete lies on his side with the hand placed on the table (A) and the clinician applies manual resistance to resist scapular movements (such as protraction and retraction) (B). The athlete is instructed to perform slow and controlled movements. in full internal rotation (thumb down).44 Originally, Jobe and Moynes44 reported high levels of EMG activity in the supraspinatus muscle during this exercise. Recently, several investigators have tested the efficiency of this exercise. Townsend et al.81 reported that the best exercise to activate the supraspinatus muscle was the military shoulder press, but this exercise is not recommended for the overhead throwing athlete. Furthermore, the investigators noted that the empty can exercise produced high EMG activity but only when the arm was elevated from

90° to 120°, which places the upper extremity into an impingement type of position.81 Blackburn et al.11 noted that the position with the patient lying prone and with the arm abducted to 100° and full external rotation (Fig. 8) produced the highest EMG activity in the supraspinatus muscle, compared with the empty can position. This exercise maneuver, advocated by Blackburn et al.,11 has been substantiated by Malanga et al.61 Many times when athletes perform the empty can exercise they complain of shoulder pain during this maneuver. We believe the shoulder pain may be occurring because of superior displacement of the humeral head due to weakness of the external rotator muscles. Overhead throwing athletes often exhibit external rotator muscle weakness; thus, we advocate the "full can" exercise (Fig. 9) instead of the empty can exercise in an attempt to avoid the possibility of causing superior humeral head displacement, which may lead to pain and inflammation. Also during this second rehabilitation phase, the overhead throwing athlete is instructed to perform core

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Figure 8. Prone horizontal abduction at 110° of shoulder abduction and full external rotation. This exercise produces high levels of EMG activity of the posterior rotator cuff, supraspinatus, and lower trapezius muscles. Figure 10. Rhythm stabilization exercise drill: the subject throws a 2-pound Plyoball (Functional Integrated Technologies, Watsonville, California) against the wall, at the endrange of external rotation (late cocking). strengthening exercises for the abdomen and lower back musculature. Plus, the athlete should perform lower extremity strengthening and participate in a running program, including jogging and sprint timing. Upper extremity stretching exercises are continued as needed to maintain soft tissue flexibility. Phase Three--Advanced Strengthening Phase In phase three, the advanced strengthening phase, the goals are to initiate aggressive strengthening drills, enhance power and endurance, perform functional drills, and gradually initiate throwing activities. During this phase, the athlete performs the Thrower's Ten exercise program, continues manual resistance stabilization drills, and initiates plyometric drills. Dynamic stabilization drills are also performed to enhance proprioception and neuromuscular control. These drills include rhythmic stabilization exercise drills by throwing a ball into a wall (Fig. 10), push-ups onto a ball (Fig. 11), and ball throws. Plyometric training (described in the next paragraph) may be used to enhance dynamic stability, enhance proprioception, and gradually increase the functional stresses placed on the shoulder joint. Plyometric exercise employs three phases, all intended to use the elastic and reactive properties of the muscle to generate maximum force production.13, 16, 18 The first phase is the eccentric phase, where a rapid prestretch is applied to the musculotendinous unit, stimulating the muscle spindle. The second phase is the amortization

Figure 9. The full can exercise movement. This exercise is performed in the plane of the scapula. The subject elevates the arm with the thumb pointed upward, as if not to spill contents of an imaginary can, stopping at 90° of elevation.

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Figure 13. A plyometric exercise drill: a two-handed overhead soccer throw.

Figure 11. Rhythm stabilization exercise drill: the subject performs a push-up into a Plyoball. At midrange, the subject holds that position.

Figure 14. A plyometric exercise drill: a two-handed side throw using an 8-pound Plyoball. Note the use of the lower extremity and hips to produce trunk and shoulder rotation.-

Figure 12. A plyometric exercise drill: a two-handed chest pass using an 8-pound Plyoball that is thrown into a Plyoback (Functional Integrated Technologies). phase, representing the time between the eccentric and concentric phases. This time should be as short as possible so that the beneficial neurologic effects of the prestretch are not lost. The final phase is the resultant concentric contraction. Wilk et al.88, 98 established a plyometric exercise program for the overhead thrower. The initial plyometric program consists of two-handed exercise drills such as a chest pass, overhead soccer throw, side-to-side throws, and side throws (Figs. 12 through 14). The goal of the plyometric drills is the transfer of energy from the legs and trunk to the upper extremity. Once these two-handed exercise drills are mastered, the athlete is progressed to

Figure 15. A plyometric exercise drill: a one-handed baseball throw with use of a 2-pound Plyoball.

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one-handed drills. These drills include standing onehanded throws in a functional throwing position (Fig. 15), wall dribbling, and plyometric step and throws. Swanik et al.80 reported that a 6-week plyometric training program resulted in enhanced joint position sense, enhanced kinesthesia, and decreased time to peak torque generation during isokinetic testing. Fortun et al.32 noted improved shoulder internal rotation power and throwing distance after 8 weeks of plyometric training in comparison with conventional isotonic training. Additionally, muscle endurance exercises should be emphasized for the overhead thrower. Recently, Murray et al.67 documented the effects of fatigue on the entire body during pitching using kinematic and kinetic motion analysis. Once the thrower was fatigued, shoulder external rotation decreased and ball velocity diminished, as did lead knee flexion and shoulder adduction torque. Voight et al.86 documented a relationship between muscle fatigue and diminished proprioception. Chen et al.17 demonstrated that once the rotator cuff muscles are fatigued, the humeral head migrates superiorly when arm elevation is initiated. Recently, Gladstone et al. (unpublished data, 1996) documented that once the shoulder musculature fatigues in professional baseball pitchers during game situations, the humeral head translates superiorly. Furthermore, Lyman et al.59 reported that the predisposing factor that correlated to the highest percentage of shoulder injuries in Little League pitchers was complaints of muscle fatigue while pitching. Thus, the endurance exercise drills described here appear critical for the overhead thrower. Specific endurance exercise drills we use include wall dribbling with a Plyoball (Functional Integrated Technologies, Watsonville, California), wall arm circles, upper body cycle, or isotonic exercises using lower weights with higher repetition. Other techniques that may be beneficial to enhance endurance include throwing an underweighted or overweighted ball (that is, a ball that is either less than or more than the weight of an official baseball).14, 18, 25, 27, 57, 84 These techniques are designed to enhance training, coordination, and the transfer of kinetic energy. Fortun et al.32 noted an increase in internal rotation strength and power after an 8-week plyometric training program using a weighted ball. Most commonly, the underweighted ball is used to improve the transfer of energy and angular momentum.25, 27, 84 Conversely, the overweighted ball is generally used to enhance shoulder strength and power.25, 27, 84 Also, during this third rehabilitation phase an interval throwing program may be initiated. Before initiating such a program, we occasionally suggest that the athlete perform "shadow" throwing or mirror throwing, which is the action of mimicking the throwing mechanics into a mirror, but not actively throwing. This is designed to allow the athlete to work on proper throwing mechanics before throwing a baseball. The interval throwing program is initiated once the athlete can fulfill these specific criteria: 1) satisfactory clinical examination, 2) nonpainful range of motion, 3) satisfactory isokinetic test results, and 4) appropriate rehabilitation progress. The interval throwing

program is designed to gradually increase the quantity, distance, intensity, and type of throws needed to facilitate the gradual restoration of normal biomechanics. Interval throwing is organized into two phases: phase I is a long-toss program (from 45 to 180 feet) and phase II is an off-the-mound program for pitchersa.90 During this third rehabilitation phase, we usually initiate phase I of the interval throwing program at 45 feet and progress to throwing from 60 feet. The athlete is instructed to use a crow-hop type of throwing mechanism and lob the ball with an arc for the prescribed distance. Flat ground, longtoss throwing is used before throwing off the mound to allow the athlete to gradually increase the applied loads to the shoulder while using proper throwing mechanics. In addition, during this phase of rehabilitation, we routinely allow the position player to initiate a progressive batting program. We routinely use a program that progresses the athlete from swinging a light bat, to hitting a ball off a tee, to soft-toss hitting, to batting practice. Phase Four--Return-to-Throwing Phase Phase four of the rehabilitation program, the return-tothrowing phase, usually involves the progression of the interval throwing program. For pitchers, we progress the long-toss program to 120 or 145 feet, whereas position players would progress to throwing from 180 feet. Once the pitcher has successfully completed throwing from 120 or 145 feet, the athlete is instructed to throw 60 feet from the windup on level ground. Once this step is successfully completed, phase II, throwing from the mound, is performed. Position players continue to progress the long-toss program to 180 feet, then perform fielding drills from their specific position. While the athlete is performing the interval throwing program, the clinician should carefully monitor the thrower's mechanics and throwing intensity. In a study conducted at our biomechanics laboratory, we objectively measured the throwing intensity of healthy pitchers. When pitchers were asked to throw at 50% effort, radar gun analysis indicated that the actual effort was approximately 83% of their maximum speed. When asked to throw at 75% effort, the pitchers threw at 90% of their maximum effort.31 This indicates that these athletes threw at greater intensities than were suggested, which may imply difficulty of controlling velocity at lower throwing intensities. In addition, during this fourth phase the thrower is instructed to continue all the exercises previously prescribed to improve upper extremity strength, power, and endurance. The athlete is also instructed to continue the stretching program, core exercise training, and lower extremity strengthening activities. Lastly, the athlete is counseled on a year-round conditioning program based on the principles of periodization.85 Thus, the athlete is instructed when to begin such things as strength training and throwing.96 To prevent the effects of overtraining or

a To request copies of the phases of the interval throwing program, please write to the corresponding author.

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Figure 16. The concept of periodization for the overhead throwing athlete. The graph illustrates that volume, intensity, and technique should be adjusted based on the time of the year (that is, preseason, in-season, and postseason). (From Wilk et al.90)

Figure 17. Rhythmic stabilization drills to enhance dynamic glenohumeral joint stability. The athlete is instructed to maximally externally rotate, then perform reciprocal isometric contractions to enhance dynamic joint stability. The goal of this exercise is to maintain a specific joint angle.

throwing when poorly conditioned, it is critical to instruct the athlete specifically on what to do through specific exercises throughout the year (Fig. 16). This is especially critical in preparing the athlete for the following season. Wooden et al.99 demonstrated that performing a dynamic variable resistance exercise program significantly increases throwing velocity.

SPECIFIC REHABILITATION GUIDELINES

To successfully rehabilitate the overhead thrower, an accurate differential diagnosis is imperative. Once the diagnosis is established, an appropriate rehabilitation program can be formulated. Often, the previously mentioned program must be modified based on the specific disorder exhibited by the thrower. In this section, we will discuss the rehabilitation guidelines for several common injuries that occur in the overhead thrower. Posterosuperior Glenoid Impingement Posterosuperior glenoid impingement, often referred to as internal impingement, is one of the most frequently observed injuries to the overhead throwing athlete (Refs. 3­5, 40 ­ 42, 62, 87; J. R. Andrews, unpublished data, 1996). We believe that one of the underlying causes of symptomatic internal impingement is excessive anterior shoulder laxity. One of the primary goals of the rehabilitation program is to enhance the athlete's dynamic stabilization abilities, thus controlling anterior humeral head translation. Another essential goal is to restore flexibility to the posterior rotator cuff muscles of the glenohumeral joint. We strongly suggest caution against aggressive stretching of the anterior and inferior glenohumeral structures as this may result in increased anterior translation. Additionally, the program emphasizes muscle strengthen-

ing of the posterior rotator cuff to reestablish muscle balance and improve joint compression abilities. The scapular muscle must be an area of increased focus as well. Restoring dynamic stabilization is an essential goal to minimize the anterior translation of the humeral head during the late cocking and early acceleration phases of throwing. Exercise drills such as proprioceptive neuromuscular facilitation patterns with rhythmic stabilization are incorporated.92, 94 Also, stabilization drills performed at end-range external rotation are beneficial in enhancing dynamic stabilization (Fig. 17). Perturbation training of the shoulder joint is performed to enhance proprioception, dynamic stabilization, and neuromuscular control. We believe that this form of training has been extremely effective in treating the thrower who has posterior/superior impingement. Once we have restored posterior flexibility, normalized glenohumeral strength ratios, enhanced scapular muscle strength, and diminished the patient's symptoms, an interval throwing program may be initiated. Jobe40 suggested abstaining from throwing for 2 to 12 weeks before the throwing program, depending on the thrower's symptoms. Once the thrower begins the interval throwing program, the clinician or pitching coach should observe the throwing mechanics frequently. Occasionally, throwers who exhibit internal impingement will allow their arm to lag behind the scapula, thus throwing with excessive horizontal abduction and not throwing with the humerus in the plane of the scapula (Fig. 18). Jobe and colleagues40, 43, 46 referred to this as "hyperangulation" of the arm. This type of fault leads to excessive strain on the anterior capsule and to internal impingement of the posterior rotator cuff.40 ­ 42 Correction of throwing pathomechanics is critical to returning the athlete to asymptomatic and effective throwing.

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Figure 18. Hyperangulation during the overhead throwing motion. During the late cocking phase of the overhead throw, as the thrower's humerus excessively abducts horizontally, posterosuperior impingement of the shoulder joint may occur. To prevent this, the thrower must stay in the plane of the scapula. A, normal angular relationship; B, hyperangulation. (Reprinted with permission from Davidson PA, Elattrache NS, Jobe CM, et al: Rotator cuff and posterior-superior glenoid injury associated with increased glenohumeral motion: A new site of impingement. J Shoulder Elbow Surg 4: 384 ­ 390, 1995.)

Overuse Syndrome Tendinitis Occasionally, throwers will describe the symptoms and exhibit the signs of overuse tendinitis of the shoulder musculature. The tendinitis signs and symptoms can be of the rotator cuff or of the long head of the biceps brachii muscles, or both. These signs frequently occur early in the season, when the athlete's arm is not in the best condition. They can also occur at the end of the competitive season when the athlete begins to fatigue. Additionally, we see these signs develop when the athlete does not perform the in-season strengthening program while throwing. Mere participation in throwing activities does not ensure the maintenance of proper shoulder muscle strength and flexibility. Specific muscles (external rotator muscles, scapular muscles) often become weak and painful because of the stresses involved with throwing. The rehabilitation program for overuse rotator cuff muscle tendinitis should concentrate on treating the cause(s) of the tendinitis and not merely the symptoms. The athlete is often instructed to discontinue throwing for a short period (2 to 4 weeks) to reduce inflammation and restore strength and flexibility. Other times, the athlete is instructed to reduce the number of throws during competition or practice. Thus, a strict pitch count is enforced. The rehabilitation program will be successful if the cause is identified, throwing activities are modified, and proper strength and flexibility are restored. Often, the thrower will complain of bicipital pain, occasionally referred to as "groove pain." The biceps brachii muscle appears to be moderately active during the overhead throwing motion. DiGiovine et al.26 reported peak

EMG activity of 44% 32% maximum voluntary isometric contraction during the deceleration phase of throwing. In our opinion, bicipital tendinitis that is present in the overhead thrower usually represents a secondary condition. The primary disorder may be instability, a SLAP (superior labral, anterior and posterior) lesion, or some similar malady. The rehabilitation of this condition focuses on improving dynamic stabilization of the glenohumeral joint through muscle training drills. Knatt et al.50 studied the synergistic action of the capsule and shoulder muscles in a feline model and described a glenohumeral joint capsule-biceps reflex. The authors reported that stimulation of the anterior capsule caused a reflexive biceps muscle contraction. They demonstrated that the biceps brachii muscle was the first muscle to reflexively respond to stimulation of the capsule, occurring in 2.7 msec. Therefore, it is the belief of one of the authors (KEW) that the biceps brachii muscle is activated to a greater extent when the thrower exhibits hyperlaxity or inflammation of the capsule. Glousman et al.33 reported that throwers with instability exhibited a higher level of rotator cuff EMG activity compared with throwers without instability. Furthermore, Gowan et al.34 noted higher EMG activity in amateur throwers compared with skilled throwers. Nonoperative rehabilitation for this condition usually consists of a reduction in throwing activities and reestablishment of dynamic stability and modalities such as ice, ultrasound, iontophorosis, and electrical stimulation to reduce bicipital inflammation. Posterior Rotator Cuff Musculature Tendinitis The successful treatment of posterior rotator cuff musculature tendinitis, or tensile rotator cuff musculature failure, depends on its differential diagnosis from internal impingement. Frequently, the athlete complains of pain in the same location for both lesions. However, subjectively the athlete notes posterior shoulder pain during the deceleration phase of throwing. Conversely, athletes who exhibit internal impingement complain of pain during the late cocking and early acceleration phases. During the deceleration phase of the overhead pitch, the distraction forces at the glenohumeral joint approach one to one and a half times body weight.29 These are excessive forces that must be dissipated and opposed by the posterior rotator cuff muscles. Pitchers occasionally exhibit this condition. Once the athlete is examined, the most common findings are significant posterior rotator cuff muscle weakness, weakness of the lower trapezius muscle and scapular retractor muscles, and tightness of the posterior rotator cuff muscles. The rehabilitation program focuses on several key areas. First, throwing activities are discontinued until the athlete exhibits proper muscle strength ratios between the external and internal rotator muscles. This ratio should be at least 64% (optimal goal, 66% to 75%).94 Second, the athlete is placed on an aggressive strengthening program for the posterior rotator cuff muscles and the retractor and depressor muscles of the scapula. Exercises

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that we emphasize are sidelying external rotation, prone rowing into external rotation, prone horizontal abduction with external rotation, scapular retraction, and prone horizontal abduction. Fleisig et al.30 have shown that teres minor muscle EMG activity can be enhanced with the use of a towel roll placed between the humerus and the side of the body. Once strength levels have improved, the exercise program should emphasize eccentric muscle training. In particular, the external rotator muscles and the lower trapezius muscle are the focus of the eccentric program (Fig. 8). DiGiovine et al.26 determined that the EMG activity of the teres minor muscle is 84% and that of the lower trapezius muscle is 78% of a maximum voluntary isometric contraction during the deceleration phase of the throw. These two muscles are the most active during this phase and, thus, must be the focus of the strengthening program. In addition, flexibility and stretching exercises for the posterior rotator cuff muscles are performed throughout the rehabilitation program. We also use heat and ultrasound before stretching to enhance tissue extensibility while increasing circulation to the area. Once flexibility and muscle strength are improved and the athlete's pain and inflammation have abated, an interval throwing program can be initiated. The interval throwing program should be progressed slowly so that the stresses of throwing are gradually increased. The athlete is instructed to be sure to follow through properly and not to terminate the deceleration phase abruptly, which may lead to increased stresses on the posterior rotator cuff muscles. SLAP Lesions The nonoperative treatment of SLAP lesions depends on the type of lesion present. Using the classification system developed by Snyder et al.,76 type I SLAP lesions appear as fraying of the labrum and often respond favorably to a nonoperative treatment regimen. Throwers who exhibit this type of lesion are treated with a program similar to the posterosuperior glenoid impingement protocol (previously discussed). Conversely, players with a type II or type IV SLAP lesion are probably best served by undergoing surgical intervention. If rehabilitation is indicated before surgery, the program should emphasize restoration of range of motion through stretching exercises within the patient's tolerance. Avoidance of overhead motions with excessive internal/external rotation is enforced because of possible joint snapping and pain. A strengthening program should be performed in an attempt to prevent muscle atrophy. The strengthening exercises should be performed with the arm below shoulder level to prevent further damage to the glenoid labrum. Strengthening exercises such as external/internal rotation with the arm at the side or scapular plane, scapular strengthening, and deltoid muscle exercises to 90° of abduction can be safely performed. Exercises such as shoulder press, bench press, and latissimus dorsi muscle pulldowns (behind the neck) are avoided because of increased stress applied to the superior labrum and anterior gleno-

humeral joint capsule. Furthermore, the clinician should be cautious with closed kinetic chain exercises that result in excessively high joint compressive loads that could result in further compromise of the glenoid labrum.

Subacromial Impingement Primary subacromial impingement in the young professional baseball player is unusual, but it may occur.46 Subacromial impingement complaints in this group of athletes usually represent primary hyperlaxity leading to secondary impingement.46 Neer and Walsh68 and Bigliani et al.9 reported that abnormal acromial architecture may lead to rotator cuff muscle disease. In cases of abnormal acromial architecture, the athlete may require surgical treatment. Hawkins and Kennedy36 and Penny and Welsh74 stated that the coracoacromial ligament can be a primary source of abnormality in the athlete. The nonoperative treatment for subacromial impingement should focus on a five-step program. First, abstain from irritating activities such as throwing or other overhead motions for 7 to 10 days, until inflammation is diminished. Second, normalize glenohumeral motion and capsular mobility. Harryman et al.35 reported that posterior capsular tightness results in anterosuperior migration of the humeral head, thus leading to subacromial impingement. We have noted that patients with inferior capsular tightness frequently complain of subacromial pain. Thus, the rehabilitation program must focus on restoring normal capsular and soft tissue mobility posteriorly and inferiorly. The third step is to enhance dynamic stability of the glenohumeral and scapulothoracic joint. Jobe et al.46 noted subacromial impingement may be secondary to hyperelasticity of the capsular ligaments. Thus, the rehabilitation program must focus on rotator cuff muscle strength to adequately compress and stabilize the humeral head within the glenoid fossa. Furthermore, scapular strengthening should also be an area of focus. During arm elevation, the scapula upwardly rotates, retracts, and posteriorly tilts. Lukasiewicz et al.58 reported that patients with impingement exhibit less posterior tilting than do subjects without impingement. We have clinically noted this phenomenon for some time. Thus, the rehabilitation program should include pectoralis minor muscle stretching and inferior trapezius muscle strengthening to ensure posterior scapular tilting. This is especially true with the recreational baseball player who performs a sedentary job. The fourth step is to emphasize the retractor muscles of the scapula and to correct any forward-head posture. Solem-Bertoft et al.,77 using MRI, have demonstrated that excessive scapular protraction reduces anterior tilt of the scapula and diminishes the acromial-humeral space, whereas scapular retraction increases the subacromial space. Thus, we employ scapular retractionstrengthening exercises. The last step is a gradual return to throwing activities once pain has significantly diminished.

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Bennett's Lesion The successful nonoperative treatment of throwing athletes with ossification of the posterior capsule (Bennett's lesion) is often difficult. It has been our clinical experience that the thrower with symptomatic thrower's exostosis can be conservatively managed for some time; however, long-term success is limited and often surgical debridement of the ossification may become necessary. Nonoperative treatment includes abstaining from throwing until pain subsides, restoring posterior capsule and muscle flexibility, improving posterior rotator cuff musculature and scapular strength, and a gradual return to throwing activities. Primary Instability Most skillful throwers exhibit significant hyperelasticity of their anterior glenohumeral joint capsule, which allows excessive external rotation and proper throwing mechanics. Because of the repetitive microtraumatic forces of throwing, the hyperelasticity may progress to primary instability and associated lesions and complaints. This is a very common occurrence in the overhead thrower. The nonoperative treatment for this condition has been thoroughly discussed in the rehabilitation program in this article. The key aspects are reduction of throwing activity to allow diminished inflammation, normalization of motion, restoration of proper strength of glenohumeral and scapular muscles, enhancement of proprioception, and a gradual return to throwing. In the majority of cases, this treatment will be effective. Acute Traumatic Instability An acute traumatic dislocation to a throwing athlete's dominant shoulder can be devastating. The injury may include a Bankart lesion, rotator cuff muscle tear, labral tear, or even injury to the brachial plexus muscle. The treatment for a dislocation in the thrower is surgical correction. Before surgery, the athlete's shoulder should be placed in a sling for comfort. In addition, gentle range of motion exercises should be performed to gradually restore motion before surgery. A mild strengthening program for the glenohumeral and scapular muscles should also be performed with the goal of preventing muscle atrophy and weakness and loss of dynamic stabilization. Improper Mechanics Throwing with improper or faulty mechanics can lead to shoulder pain or injury, or both, because of the abnormal stresses that are applied across various tissues. To determine whether the thrower exhibits improper throwing mechanics, the clinician should carefully observe the athlete throw. Obvious flaws can be seen occasionally. The clinician may often require assistance from an experienced and knowledgeable baseball coach. The skilled eye of an experienced coach can frequently determine subtle abnormalities in the throwing mechanics. Perhaps the

most objective analysis is a high-speed video biomechanical evaluation. This can be done at a biomechanics laboratory using specialized high-speed video cameras and computer analysis of the data. When evaluating an athlete's throwing mechanics, we commonly look at several different aspects of the movement. The clinician can use a video recorder to film the thrower and analyze the biomechanics during slow-motion playback to pinpoint improper mechanics. Filming should be performed from multiple views to accurately assess the athlete, including lateral (facing the athlete), posterior, and anterior views. We normally analyze several aspects of the throwing motion in sequential order to detect subtle pathomechanical deviations through the phases of throwing. Biomechanical analysis of the throwing motion begins with the lateral view; there are several critical moments to observe from this view. During the wind-up phase, the pitcher should be in a balanced position when the lead leg reaches the highest point. Forward movement should not begin until the lead leg is fully raised. Rushing the delivery by falling toward home plate during the wind-up phase may decrease the amount of energy generated by the lower body and result in a loss of velocity. As the athlete begins the early cocking phase, the path of motion as the thrower removes the ball from the glove should be smooth, with the elbow flexed and the fingers on top of the ball. As the lead leg comes in contact with the ground, the knee should be slightly flexed and the elbow should be level with the shoulder. A right-handed pitcher will show the ball to the shortstop and a left-handed pitcher will show the ball to the second baseman. The stride should be long enough to allow sufficient rotation and force generation from the hips and trunk, approximately equal to the height of the thrower. At maximal external rotation during the late cocking phase, the arm should be abducted approximately 90° to 100°. Fleisig28 reported that throwing with reduced external rotation at the time of foot contact causes an increase in strain on the shoulder during acceleration and ball release. Furthermore, the thrower should begin straightening the elbow before shoulder internal rotation during the acceleration phase. At this time, the lead leg extends, or straightens, to stabilize the body and provide a fulcrum for body rotation. During the deceleration and follow-through phases, the throwing shoulder should internally rotate and horizontally adduct across the body. The upper extremity should cross the front of the body and end outside the lead leg. Abbreviating the follow-through and ending with the hand toward the target may increase the stresses applied to the shoulder. Observing the thrower from a posterior view allows the clinician to observe two instants during the throwing motion. As the thrower removes the ball from the glove during early cocking, the arm path should move smoothly in a down, back, and upward motion as the thrower strides toward the target. A thrower whose arm moves behind the body may cause excessive anterior capsular straining and possible internal impingement. Also of interest from the posterior view is the hand position during late cocking. As

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3. Andrews JR, Angelo RL: Shoulder arthroscopy for the throwing athlete. Techn Orthop 3: 75­79, 1988 4. Andrews JR, Carson WG Jr: The arthroscopic treatment of glenoid labrum tears in the throwing athlete. Orthop Trans 8: 44, 1984 5. Andrews JR, Kupferman SP, Dillman CJ: Labral tears in throwing and racquet sports. Clin Sports Med 10: 901­911, 1991 6. Baker CL, Liu SH, Blackburn TA: Neuromuscular compression syndrome of the shoulder, in Andrews JR, Wilk KE (eds): The Athlete's Shoulder. New York, Churchill Livingstone, 1994, pp 261­273 7. Bartlett LR, Storey MD, Simons DB: Measurement of upper extremity torque production and its relationship to throwing speed in the competitive athlete. Am J Sports Med 17: 89 ­91, 1989 8. Bigliani LU, Codd TP, Connor PM, et al: Shoulder motion and laxity in the professional baseball player. Am J Sports Med 25: 609 ­ 613, 1997 9. Bigliani LU, Ticker JB, Flatow EL, et al: The relationship of acromial architecture to rotator cuff disease. Clin Sports Med 10: 823­ 838, 1991 10. Bison LJ, Andrews JR: Classification and mechanics of shoulder injuries in throwers, in Andrews JR, Zarins B, Wilk KE (eds): Injuries in Baseball. Philadelphia, Lippincott-Raven Publishing, 1998, pp 47­56 11. Blackburn TA, McLeod WD, White B, et al: EMG analysis of posterior rotator cuff exercises. Athl Training 25: 40 ­ 45, 1990 12. Blasier RB, Carpenter JE, Huston LJ: Shoulder proprioception: Effect of joint laxity, joint position, and direction of motion. Orthop Rev 23: 45­50, 1994 13. Bosco C, Komi PV: Potentiation of the mechanical behavior of the human skeletal muscle through prestretching. Acta Physiol Scand 106: 467­ 472, 1979 14. Brose DE, Hanson DL: Effect of overload training on velocity and accuracy of throwing. Res Q 38: 528 ­533, 1967 15. Brown LP, Niehues SL, Harrah A, et al: Upper extremity range of motion and isokinetic strength of the internal and external shoulder rotators in major league baseball players. Am J Sports Med 16: 577­585, 1988 16. Cavagna GA, Dusman B, Margaria R: Positive work done by a previously stretched muscle. J Appl Physiol 24: 21­32, 1968 17. Chen SK, Wickiewicz TL, Otis JC, et al: Glenohumeral kinematics in a muscle fatigue model: A radiographic study. Orthop Trans 18: 1126, 1994 ­95 18. Chu D, Panariello RA: Sport specific plyometrics; baseball pitchers. Natl Strength Conditioning Assoc J 11(3): 81­ 84, 1989 19. Clark FJ, Burgess PR: Slowly adapting receptors in cat knee joint: Can they signal joint angle? J Neurophysiol 38: 1448 ­1463, 1975 20. Cook EE, Gray UL, Savinar-Nogue E, et al: Shoulder antagonistic strength ratios: A comparison between college-level baseball pitchers and nonpitchers. J Orthop Sports Phys Ther 8: 451­ 461, 1987 21. Crockett HC, Gross LB, Wilk KE, et al: Osseous adaptation and range of motion at the glenohumeral joint in professional baseball pitchers. Am J Sports Med 30: 20 ­26, 2002 22. Davies CJ: Compendium of Isokinetics in Clinical Usage. Fourth edition. Onalaska, WI, S&S Publishing, 1992, p 445 23. Davies GJ, Dickoff-Hoffman S: Neuromuscular testing and rehabilitation of the shoulder complex. J Orthop Sports Phys Ther 18: 449 ­ 458, 1993 24. Decker MJ, Hintermeister RA, Faber KJ, et al: Serratus anterior muscle activity during selected rehabilitation exercises. Am J Sports Med 27: 784 ­791, 1999 25. DeRenne C, Ho K, Blitzblau A: Effects of weighted implement training on 5throwing velocity. J Appl Sport Sci Res 4: 16 ­19, 1990 26. DiGiovine NM, Jobe FW, Pink M, et al: An electromyographic analysis of the upper extremity in pitching. J Shoulder Elbow Surg 1: 15­25, 1992 27. Egstrom GH, Logan GA, Wallis EL: Acquisition of throwing skill involving projectiles of varying weights. Res Q 31: 420 ­ 425, 1960 28. Fleisig GS: The Biomechanics of Baseball Pitching. Dissertation, University of Alabama at Birmingham, Birmingham, Alabama, 1994 29. 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previously stated, the ball should be facing the shortstop for right-handed throwers and the second baseman for left-handed throwers. An anterior view of the throwing motion is helpful to the clinician to determine the position of the stride leg as the foot comes into contact with the ground. At this time, the lead foot should be pointed toward the target. Often young and inexperienced throwers overrotate and place the lead foot on the first base side of the mound. This results in the pitcher's "opening up too soon" and causes the hips to rotate early, resulting in loss of velocity and increased strain to the anterior shoulder. Fleisig28 has shown that as the lead foot angle becomes more open, the thrower tends to throw across the body and increases the loads applied to the shoulder. Furthermore, "leading with the elbow" (increased horizontal adduction and elbow flexion) during the acceleration phase correlated to decreased loads at the shoulder but increased loads on the medial aspect of the elbow.28 The orientation of the shoulder at the moment of ball release can also be assessed from the anterior view of the throwing motion. The throwing elbow should be in line with the shoulder with minimal flexion of the elbow. The nonthrowing elbow should be tucked at the side. As the athlete progresses into the deceleration and followthrough phases, the throwing arm should follow a long arc of deceleration, allowing proper dissipation of forces from the arm to the trunk and lower extremities.

SUMMARY

Overhead throwing athletes typically have a unique musculoskeletal profile. The overhead thrower frequently experiences shoulder pain because of anterior capsular laxity and increased demands placed on the dynamic stabilizers. This may be the result of repetitive high stresses imparted to the shoulder joint and may lead to the development of injuries. Most commonly, these injuries are overuse injuries and can be successfully managed with a well-structured rehabilitation program. The rehabilitation program should focus on the correction of adaptive changes seen in the overhead thrower, such as loss of internal rotation and muscle weakness of the external rotator muscles and scapular muscles. The rehabilitation specialist may then initiate the athlete's gradual throwing program to return to competition. The athlete's overhead throwing motion should be examined to determine whether improper biomechanics are contributing to the injury. Lastly, education of the athlete in the area of year-round conditioning is imperative. The overhead throwing athlete should be instructed as to when to begin conditioning and throwing to prepare for the next competitive season and prevent subsequent injury. REFERENCES

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