Journal of Orthopaedic & Sports Physical Therapy
2000;30(9) :544-551
Assessment of Shoulder Strength in
ProfessionaI Baseball Pitchers
Robert Donatelli, PhD, PT; OCS1
Todd S. Ellenbecker, MS, PT; SCS, OCS, CSCS2
Sheila R. Ekedahl, BS3
Joseph S. Wilkes, MD4
Keith Kocher, PTS
John Adam, ATCb
Study Design: A bilateral comparison of strength and range of motion testing in professional
baseball pitchers.
Objective: We studied 39 professional male baseball pitchers to determine if the shoulder
used for throwing was weaker or had kss passive range of motion, compared to the
nondominant arm.
Background: Shoulder muscle weakness has been proposed as a possible risk factor for
developing injury. Therefore, objective quantification of the strength of glenohumeral and
scapular rotator muscle groups should be studied in a population of professional baseball
pitchers.
Methods and Measures: Passive internal and external range of motion was bilaterally
measured at 90' of abduction. Muscle strength of the following muscles was measured
bilaterally with a hand-held dynamometer: external and internal glenohumeral rotators,
supraspinatus, middle trapezius, lower trapezius, and serratus anterior.
Results: Passive external rotation of the glenohumeral joint at 90' of abduction on the
pitching side was significantly greater than on the nonpitching side. Passive internal rotation
range of motion on the nonpitching side was significantly greater than on the pitching side.
The pitching arm's internal rotators, when tested in abduction, were significantly stronger
than the nonpitching arm. The nonpitching arm's external rotators in the plane of the
scapula, and in abduction, were significantly greater than those of the pitching arm. The
pitching arm's middle and lower trapezius muscles were significantly stronger than those of
the nonpitching arm.
Conclusion:The range of motion and strength characteristics measured in this study can
assist clinicians in evaluating athletes who use overhead throwing motions. ) Orthop Sports
Phys Ther 2OOO;30:544-551.
Key Words: professional baseball pitchers, rotator cuff strength, scapular muscle
strength
Physiotherapy Associates, Alphama, Ga.
* Physiotherapy Associates, Scottsdale, Ariz.
Research and Development Department, Physiotherapy Associates, Memphis, Tenn.
' The Hughston Clinic, Atlanta, Ga.
Physiotherapy Associates, Tempe, Ariz.
Milwaukee Brewers, County Stadium, Milwaukee, Wis.
Send correspondence to: Robert Donatelli, 10160 Medlock Bridge Road, Alpharetta, GA 30022.
he action of overhead
throwing places significant demands on the
shoulder. Shoulder injuries in overhead
throwing athletes include rotator
cuff tendinitis, subtle instabilities,
labral degenerative changes and
tears, and secondary subacromial
and parascapular
Repetitive microtrauma and eccentric overload occur commonly in
professional baseball pitchers, resulting in muscle-tendon injury.
Subtle instabilities of the glenohumeral joint may cause impingement within the subacromial
spa~e.'~J~.~
Wuelker et a132-ssstudied the
forces and translational movements
of the glenohumeral joint during
elevation. Increased forces were
observed during the final stages of
shoulder elevation. Humeral head
translation was found to be 9 mm
superiorly and 4.4 mm anteriorly
during elevation of the glenohumeral joint. Subtle changes in the
translation of the humeral head,
combined with the forces under
the acromion and coracoid process, are the proposed etiological
factors of shoulder impingement.
Weakness of the rotator cuff m u s
T
Inconsistent with the studies mentioned above, the
cles could be a contributing factor in the subtle
studies of Wilk et alS1and HintonI5 reported that the
changes of the humeral head translations.
external rotator muscles of the nonpitching shoulder
Using high-speed motion analysis, Fleisig et a19
were significantly stronger than the pitching side.
evaluated elbow and shoulder kinetics in 26 highly
skilled, nonimpaired adult pitchers. The biomechani- The throwing shoulder exhibits a natural tendency
toward relative external rotation weakness. Shoulder
cal analysis of the pitching motion identified large
muscle weakness has been proposed as a possible risk
forces at the shoulder and elbow. The compressive
forces and varus torques were identified as predispos- factor for developing injury.lGIRTherefore, objective
quantification of the strength of glenohumeral and
ing factors in the development of overuse injuries
scapular rotator muscle groups should be studied in
such as glenohumeral labral tears, impingement, rotator cuff and elbow tendon overload. Pappas et alZ6 a population of professional baseball pitchers.
The purposes of this study were to compare the
also used high-speed motion analysis to determine
passive range of motion and muscle strength of the
normal kinetic and kinematic patterns of the throwglenohumeral and scapular rotators in the pitching
ing motion. They developed graphs showing the
and the nonpitching arms in a group of professional
forces in internal and external rotation and torque
in the shoulder and elbow as a result of the throwing baseball pitchers.
motion. These motion analysis studies demonstrate
that shoulder stability is controlled, to a large extent, METHODS
by proper positioning of the arm and appropriate
Forty-three minor league male professional basebalance of musculature around the shoulder.
ball pitchers volunteered to participate in this study.
Magnusson et aP2 reported significant muscle
weakness in the pitching arm of professional baseball Subject consent was obtained before the data were
pitchers. The study identified significant muscle defi- collected. The Institutional Review Board of Stryker
Physiotherapy Associates (Memphis, Tenn) approved
cits of 3 glenohumeral muscles: the supraspinatus,
the testing methodology and protocol prior to data
the external rotators, and the abductors. Injury histcollection. The pitchers had played professional base
ry had no effect on strength and range of motion;
ball for an average of 1.8 years (range, 0.082-6
however, the study suggested that muscle weakness
years).
The average number of innings pitched at the
resulted from the demands of the pitching motion.
professional
level was 103.9 innings (range, 0-800 inFurthermore, weakness of the supraspinatus muscle
nings).
The
average
age of the pitchers tested was
in pitchers was implicated as a subclinical pathology
20.7
years
(range,
17-28
years).
or chronic fatigue. Their study did not test scapular
Testing
was
performed
during the first week of exrotator muscles, and reliability was not reported for
tended
spring
training.
All
players were asked to fill
the manual muscle testing positions used in the data
out
questionnaires
regarding
history of shoulder-arm
collection. The only muscle testing reliability reportpain
or
existing
injuries.
To
be
included in this
ed in the study was based on previous studies investistudy,
subjects
had
to
be
currently
free from injury
gating inter- and intra-rater reliability of hand-held
in
the
shoulder
and
elbow
bilaterally,
and had not
dynamometry.
been
on
the
disabled
list
for
a
period
of 8 months
Pitching requires scapular and glenohumeral stabiprior
to
the
date
of
data
collection.
Four
of the
lization. The balance of the scapulothoracic and glepitchers
had
prior
surgical
treatment
for
shoulder
nohumeral joints is sustained by the strength of the
scapular and glenohumeral rotator m u s ~ l e s . ~ ~ . ~ T hand
e elbow injuries, and were excluded from the
study.
This left 39 study participants. None of the
scapular rotator muscles control the scapula, providpitchers
were presently experiencing pain from an
ing a stable glenoid, and they maintain optimal
injury,
nor
did they have pain during the muscle
length-tension relationships of the glenohumeral
testing
or
range
of motion measurements.
m u s ~ l e s . ' ~The
J ~ rotator cuff muscles dynamically staRange of motion and muscle testing were perbilize the humeral head in the glenoid fossaZ0and
formed on both the pitching arm and the nonpitchprovide the main deceleration forces to the pitching
ing arm. Otis et aP5 established normative values for
arm during the follow-through phase of pitching.I7
arm
strength by comparing the dominant and nonSeveral studies have investigated shoulder strength of
dominant
arms of adult men. Comparison of domibaseball p i t c h e r ~ . ~ ~ ~ ~ ~ nfindings
s i s t e namong
t
these
nant with nondominant arm strength allows the clinistudies are as follows: (1) isokinetic studies of base
cian to assess strength deficits more accurately in a
ball pitchers show significantly greater pitching arm
specific p~pulation.'~
internal rotation muscle strength with no apparent
difference in external rotation2." (2) the ratio of external rotation to internal rotation strength ranges
Range of Motion Measurement
from 63 to 70% in the pitching arm,4.5.7and (3) the
One tester, masked to each subject's pitching arm,
pitching shoulder's adductors are significantly stronmeasured all subjects' passive internal and external
ger than those of the nonpitching side.
J Orthop Sports Phys Ther .Volume SO Number 9. September 2000
-
1
I
FIGURE 1. Measurement of passive external rotation. The arm is at 90"of
abduction, the elbow is flexed to 90°, and the forearm is in neutral.
ranges of motion using a standard goniometer. All
measurements were taken 3 times, and a mean of
the 3 measurements was calculated and used in the
investigation. Rotational measurements were taken
with the subject in the supine position, with the
shoulder abducted to 90" in the coronal plane. The
elbow was flexed to 90" and the forearm was in neutral rotation (Figure 1).
Passive external rotation range of motion was measured by moving the subject's extremity into external
rotation, maintaining the positions of abduction, elbow flexion, and forearm rotation. The extremity
was rotated externally until end range of motion was
obtained. No passive overpressure was exerted during
measurement, and the weight of the arm against
gravity provided the end range of motion measurement during this study. The axis of the goniometer
was aligned with the olecranon process of the elbow.
The stationary arm of the goniometer was aligned
along the midline of the lateral forearm.
Passive internal rotation was measured with the
subject's shoulder in 90" of abduction and elbow and
forearm positioning was identical to that described
for external rotation. The subject's arm was internally rotated while an anterior force was applied to the
coracoid and humerus to ensure that scapular compensation did not occur.8 No scapular protraction or
upward rotation was allowed. Maximum passive internal rotation was then recorded using identical goniometric landmarks.
Manual Muscle Testing
Muscle strength was measured with a hand-held
dynamometer (Nicholas Manual Muscle Test, Lafayette Instruments, Lafayette, Ind), capable of registering from 0 to 199.9 kg. A digital display registered
to 0.1 sensitivity. The unit was calibrated before testing as recommended by the manufacturer. The validity and reliability of hand-held dynamometer mea546
surements in the upper extremity is well estab
lished.23.24.2R
Methods of Strength Testing
One experienced tester, masked to the subject's
pitching and nonpitching arms, performed all the
manual muscle tests. A second tester stabilized the
subject's arm during the muscle testing. None of the
manual muscle tests were done the day of, the day
before, or the day after the subjects pitched in a
game situation.
All muscle testing positions elicit contraction of
several muscle groups. However, the manual muscle
test positions that were chosen as the optimal test position for the glenohumeral and scapular muscles
were based on good test-retest reliability, no provocation of pain, and minimal contribution from involved
shoulder synergist^.^^ Three active resistance tests
were performed bilaterally for each muscle group.
An active resistance test is manual resistance against
an actively contracting muscle or muscle group (ie,
against the direction of the movement as if to prevent that movement). The resistance was increased to
meet the demands of the contracting muscle. After
the hand-held dynamometer was located proximal to
the styloid process of the radius, the subject was instructed to increase force gradually until maximum
contraction was achieved.
Shoulder internal and external rotation strength
was measured with the subject in the supine position,
with the humerus placed on a wedge at 30" anterior
to the frontal plane and elevated to 45", and in the
frontal plane with 90" of abduction (Figure 2). The
elbow was flexed to 90" in both positions and the
hand-held dynamometer was placed on the ulnar styloid process. In a study by Greenfield et al,13external
rotator muscle strength was shown to be markedly
greater in the plane of the scapula (30" anterior to
the frontal plane) than in the frontal plane.
The supraspinatus muscle's strength was measured
with the subject in the sitting position. The subjects
stabilized themselves by grasping the stool with the
arm not being tested. The humerus was held in maximum internal rotation (thumb pointing downward).
The position of "scaption" has been reported to p r e
duce maximal levels of supraspinatus muscle activat i ~ nThe
. ~ arm
~ was held at 90" of abduction and 30"
anterior to the frontal plane. A goniometer was used
to determine and verify the 30" anterior position by
placing the stationary arm of the goniometer on the
spine of the scapula. The axis of the goniometer was
placed on the tip of the acromion and the moving
arm was placed on the proximal humerus.
The muscle strength for the serratus anterior muscle was measured with the subject in the supine position, with the arm held at 90" of flexion and the elbow fully extended. The subject was asked to reach
J Orthop Sports Phys Ther.Volume SO. Number 9. September 2000
FIGURE 2. Manual muscle test for the glenohumeral rotator muscles. (A) The hand-held dynamometer is placed on the ulnar styloid process. The
humerus is laced on a wedge at 30" anterior to the frontal plane (plane of scapula). The humerus is abducted to 45", and the elbow is flexed to 90".
(0)The huAerus is abducted'io 90°, and the elbow is flexed io 900.'
with the test arm projecting the upper extremity anteriorly (upward from the table). Pressure with the
hand-held dynamometer was against the subject's fist,
transmitting the pressure downward through the extremity, to the scapula.
Lower trapezius muscle strength was measured
with the subject in the prone position (Figure 3).19
The arm was positioned diagonally overhead with the
thumb pointing upward. The arm was held in 145"
of abduction. The strength of the middle trapezius
muscle was also measured with the subject prone.
The arm was held at 90" of abduction and the
thumb pointing upward. The degree of abduction
was determined by placing the goniometer along the
lateral border of the scapula, the axis on the head of
the humerus, and the moving arm on the proximal
humerus.
Data Analysis
FIGURE 3. Manual muscle test for the lower trapezius muscle group. The
arm is abducted to 145" and the thumb is pointing upward (external rotation of the humerus). The hand-held dynamometer is placed on the styloid process of the ulna.
J Orthop Sports Phys Ther*Volume 30-Number 9-September 2000
Shoulder range of motion was analyzed by first taking the mean of 3 trials of each measurement. A repeated measures ANOVA was used to determine initial significance. The repeated factor was dominance
(pitching and nonpitching arms) and range of m e
tion (external rotators in neutral and in 90" of a b
duction, and internal rotators in 90" of abduction).
The dependent variable was range of motion. Once
significance was established, further analysis consisted
A
rn
rn
4
TABLE 1. Range of motion measurements* ( N = 39).
External rotation (neutral)
External rotation (90" abduction)
Internal rotation (90" abduction)
Pitching
am,
" (SD)
Nonpitching
am,
" (SD)
54.48"
(10.47)
103.69"
(8.82)
40.33"
(8.99)
54.75"
(13.69)
95.03"
(8.53)
50.37"
(9.63)
t ratio
df
P wlw
NS
-.I50
38
.882
pitching > nonpitching (P < .001)
6.393
38
.OW
pitching < nonpitching (P < .MI)
-6.858
38
.OW
Significance
Each number is followed by the standard deviation (SD).
of paired sample t tests to compare the differences
in means. The alpha level was set at .05.
Shoulder strength was also analyzed by first taking
the mean of 3 trials of each strength measurement.
A repeated measures ANOVA was used to determine
initial significance. Our repeated factors were dominance (pitching and nonpitching arms) and muscle
(middle trapezius, lower trapezius, supraspinatus, internal rotators [POS], external rotators [POS], internal rotators [90° of abduction], and external rotators
[90° of abduction]). The dependent variable was isometric force. Once significance was established, further analysis consisted of paired sample t tests to
compare the differences in means across groups,
dominance, and strength. The alpha level was set at
0.05.
To examine test-retest reliability of the muscle and
range of motion testing, the examiner retested every
fifth subject. An intraclass correlation coefficient
(ICC 2,k) was used to determine the degree of testretest reliability.27
tion (neutral) range of motion between pitching and
nonpitching arms. However, external rotation range
of motion at 90" of abduction was significantly greater in the pitching arm than in the nonpitching arm
(Table 1). Furthermore, internal rotation passive
range of motion at 90" of abduction was significantly
less in the pitching arm than in the nonpitching arm
(Table 1).
Strength
The second analysis of variance revealed that there
were significant differences between the pitching and
nonpitching arms. On further analysis (paired sample t tests), the means for external rotation (POS
and at 90" of abduction), internal rotators (at 90" abduction), lower trapezius and middle trapezius muscle groups indicated significant strength differences
(Table 2). The pitching arm showed significantly
stronger middle trapezius muscles, lower trapezius
muscles, and internal rotators in 90" of abduction.
Of particular importance, the pitching arm's external rotators were significantly weaker than those of
the nonpitching arm, when tested in the POS (P<
.01) and in 90" of abduction (P < .001).
Unilateral strength ratios (external-internal rotation ratios) were formed manually by dividing each
subject's external rotation strength by their corresponding internal rotation strength values. The ex-
RESULTS
Range of Motion
There were significant differences in internal and
external rotation passive range of motion between
the dominant and nondominant extremity (Table 1).
On further analysis (paired sample t tests), there
were no significant differences in the external rotaTABLE 2. Strength measurements* ( N = 39).
t
df
P value
pitching > nonpitching (p < .01)
pitching > nonpitching (p < .05)
NS
3.221
2.543
-.743
38
38
38
.003
.015
.462
18.75 kg (3.18)
NS
1.626
38
.I12
13.27 kg (3.59)
14.50 kg (3.11)
nonpitching > pitching (p < .01)
38
.002
18.20 kg (3.96)
17.43 kg (3.65)
pitching > nonpitching (p < .05)
2.275
38
.029
15.05 kg (3.67)
17.14 kg (4.09)
nonpitching > pitching (p < .001)
-4.528
38
.OOO
Muscle
Pitching
Nonpitching
Middle trapezius
Lower trapezius
Supraspinatus
Internal rotators
(plane of scapula)
External rotators
(plane of scapula)
Internal rotators
(90")
External rotators
(90")
6.66 kg (1.66)
6.85 kg (1.90)
8.78 kg (2.06)
5.84 kg (1.73)
6.08 kg (122)
8.98 kg (2.50)
19.57 kg (4.03)
-3.253
Each measurement is followed in parentheses by the standard deviation.
548
J Orthop Sports Phys Ther .Volume SO. Number 9. September 2000
TABLE 3. Extemal-internal rotation ratios.
Position
Plane of the
scapula
90 degrees
Pitching arm
Mean, SD
Nonpitching arm
Mean, SD
68.5%, 15.92
78.4'10, 16.96
ternal-internal rotation ratios in this study were 68%
on the pitching arm and 78% on the nonpitching
arm when measured in the plane of the scapula, and
83% on the pitching arm and 99% on the nonpitching arm in 90 of glenohumeral joint abduction (Table 3).
Reliability
Intraclass correlation coefficients (ICC) showed
high intrarater reliability of the muscle tests for the
middle trapezius (0.933), lower trapezius (O.891), supraspinatus (0.955), internal rotator muscles in the
plane of the scapula (0.822) and at 90" of abduction
(0.932), and external rotator muscles in the plane of
the scapula (0.815) and at 90" of abduction (0.960).
The range of motion measurement intrarater reliability was 0.969 for internal rotator muscles at 90" of
abduction and 0.792 for external rotation at 90" of
abduction. There was poor intrarater reliability for
the serratus anterior muscle test (0.266). For this reason, we did not include the results of the manual
muscle strength testing for the serratus anterior m u s
cle group in the data analysis.
DISCUSSION
Passive Range of Motion
When compared with the nonpitching arm, the bilateral glenohumeral passive range of motion tests
showed statistically greater passive external rotation
in 90" of abduction and less passive internal rotation
range of motion in the pitching arm. This finding is
consistent with previous research on athletes who
throw using one arm, and identifies a consistent pattern of glenohumeral rotation in the athletic shoulder.4.6The consequences of internal rotation loss, according to Harryman et al,I4 include increased anterior humeral head translation and superior migration. The exact mechanism for the loss of internal
rotation range of motion is still being investigated.
Hypotheses include fibrous tissue formation in the
posterior capsule, musculotendinous tightness in the
posterior rotator cuff, as well as osseous changes secondary to the repetitive demands of throwing and
overhead activity." Changes in glenohumeral rotation, in response to sport-specific demands, are an
example of anatomic variation found in athletes durJ Orthop Sports P h p Ther -Volume SO. Number 9. September 2000
ing musculoskeletal evaluation, and may have consequences when evaluating and treating athletes in this
population.
Glenohumeral Muscle Strength
The eccentric overload of the glenohumeral external rotator muscles has been implicated as a destructive force in the sh~ulder."~
These muscles are responsible for decelerating the humerus during the
follow-through phase and they undergo extreme eccentric overload with repetitive overhead throwing.
Andrews and Angelos found that most rotator cuff
tears in throwers were located from the midsupraspinatus posterior to the mid infraspinatus area. They
believe these tears are a consequence of tensile failure as the rotator cuff muscles try to resist distraction, horizontal adduction, and internal rotation at
the shoulder during arm deceleration. Fleisig et a19
believe that the posterior shoulder muscles are susceptible to injury during arm deceleration as they resist glenohumeral distraction and horizontal adduction.
The strength of the glenohumeral rotators in professional baseball pitchers has been reported in previous studies primarily using isokinetic dynamomet e r ~ . ~ . Three
~ . ~ -of
~ these
. ~ ~ studies report internal rotator muscle strength to be significantly stronger in
the pitching arm with no significant weakness or
equal the strength of the external rotator muscle in
the pitching arm, when compared with the nonpitching arm.4.5.H
Wilk et al" and Magnusson et alZ2reported significant deficits of the external rotator
muscles on the dominant arm, as compared to the
nondominant arm.
In our study, we found a significant deficit of the
glenohumeral external rotator muscles, significantly
stronger internal rotator muscles at 90" of abduction,
and no significant difference in the strength of the
supraspinatus muscle group in the pitching arms of
professional baseball pitchers, when compared with
their nonpitching arms.
The absence of strength deficits of the supraspinatus muscle group may be a result of significantly
stronger middle and lower trapezius muscle groups
on the pitching side. The strength of the scapular rotators assists in stabilizing the scapula during the
overhead throwing motion, and helps prevent impingement. Andrews and Angel$ believe tears of the
supraspinatus are a consequence of tensile failure as
the rotator cuff muscles attempt to control distraction, horizontal adduction, and internal rotation at
the shoulder during arm deceleration. Horizontal adduction of the glenohumeral joint is accompanied by
protraction of the scapula. Therefore, the strength of
the scapular retractors (the middle and lower trapezius muscles) could play a crucial role in stabilizing
the scapula and preventing injury to the supraspinatus muscle group.
Muscle strength ratios of the external to internal
In our
rotator muscles vary from 63 to 70%.4.5.R
study, the mean strength of the external rotators in
the dominant arm was 68% of the strength of the internal rotators when tested in the POS, and 83% of
the internal rotators when tested at 90 of abduction.
These manually assessed muscle strength ratios, between the internal and external rotators, are within
the ranges reported in the literature for uninjured
professional baseball pitchers.
Scapular Muscle Strength
A unique aspect of this study was the muscle testing of the middle and lower trapezius muscles in
professional baseball pitchers. When comparing the
pitching with the nonpitching arm, our study demonstrated significantly stronger pitching arm middle
and lower trapezius strength. During the late cocking
phase of pitching, the rhomboids and the trapezius
muscles are responsible for full retraction of the
scapula, thus, preventing impingement of the glenohumeral muscles on the acromion during maximum
external r ~ t a t i o nThe
. ~ serratus anterior muscle protracts the scapula and maintains congruency of the
glenohumeral joint, allowing an optimal length-tension relationship of the glenohumeral muscles.
CONCLUSION
This study provides the clinician with a comprehensive profile of range of motion and muscle
strength measurements in the pitching and nonpitching arms of professional baseball pitchers. Significantly less passive internal rotation range of motion
of the glenohumeral joint in the pitching arm of
pitchers and greater pitching arm external rotation
was measured. Statistically significant strength deficits
of the glenohumeral external rotators in the pitching
arm were recorded, while significantly greater
strength of the internal rotators at 90" of abduction
was measured compared to the nonpitching arm.
Significantly greater strength was also measured in
the middle and lower trapezius muscles on the pitching arm. However, n o statistically significant difference existed between extremities in supraspinatus
strength. Our results provide an important base line
for assessing deficits in strength and motion for athletes who use one arm for overhead throwing.
ACKNOWLEDGMENTS
Special thanks to Roger Caplinger, ATC; Doug Baker, ATC; and Mike Rich, ATC, for their assistance in
the data collection. Thanks to Professional Baseball
Athletic Trainers Society (PBATS) for their assistance
550
in developing a research committee, and for their
support of this study. We also thank Angelo Mattalino, MD, for his support of this study and Carol
Binns, MA, for her assistance in editing the manuscript.
REFERENCES
Abrams IS. Special shoulder problems in the throwing
athlete: pathology, diagnosis, and nonoperative management. Clin Sports Med. 1991;10:839-845.
Alderink GJ, Kuck DJ. lsokinetic shoulder strength of high
school and college-aged pitchers. I Orthop Sports Phys
Ther. 1986;7:163-172.
Andrews JR, Angelo RL. Shoulder arthroscopy for the
throwing athlete. Tech Orthop. 1988;3:75-82.
Bartlett LR, Storey MD, Simons BD. Measurement of upper extremity torque production and its relationship to
throwing speed in competitive athletes. A m ] Sports Med.
1989;17:89-91.
Brown LP, Niehues SL, Harrah A, Yavorsky P, Hirshman
HP. Upper extremity range of motion and isokinetic
strength of the internal and external shoulder rotators in
major league baseball players. Am 1 Sports Med. 1988;
16:577-585.
Cook EE, Gray VL, Savinar-Nogue E, Medeiros J. Shoulder
antagonistic strength ratios: a comparison between college level baseball pitchers and nonpitchers. ] Orthop
Sports Phys Ther. l987;8:451-461.
Ellenbecker TS, Mattalino AJ. Concentric isokinetic shoulder internal and external rotation strength in professional
baseball pitchers. ] Orthop Sports Phys mer. 1997;25:
323-328.
Ellenbecker TS, Roetert EP, Piorkowski PA, Schulz DA.
Glenohumeral joint internal and external rotation range
of motion in elite junior tennis players. ] Orthop Sports
Phys Ther. 1996;24:336-342
Fleisig GS, Andrews JR, Dillman CJ,Escamilla RF. Kinetics
of baseball pitching with implications about injury mechanisms. Am ] Sports Med. 1985;23:233-239.
Glousman R. Electromyographic analysis and its role in
the athletic shoulder. Clin Orthop. 1993;288:27-34.
Glousman RE, Jobe FW, Tibone JE, et al. An EMG analysis
of the shoulder in pitching. Am J Sports Med. 1983;ll:
3-8.
Gowan ID, Jobe FW, Tibone JE, Perry J, Moynes DR. A
comparative electromyographic analysis of the shoulder
during pitching: professional versus amateur pitchers. Am
] Sports Med. 1987;15:586-590.
Greenfield BH, Donatelli R, Wooden MJ, Wilkes J. Isokinetic evaluation of shoulder rotational strength between
plane of the scapula and frontal plane. Am 1 Sports Med.
1990;18:124-127.
Harryman DT, Sidles JA, Clark JM, McQuade KJ, GibbTD,
Matsen FA. Translation of the humeral head on the glenoid with passive glenohumeral joint motion. 1 Boneloint
Surg. 1990;72:1334-1343.
Hinton RY. lsokinetic evaluation of shoulder rotational
strength in high school baseball pitchers. Am J Sports
Med. 1988;16:274-279.
Jobe FW, Kvitne RS. Shoulder pain in the overhead or
throwing athlete. The relationship of anterior instability
and rotator cuff impingement. Orthop Rev. 1989;28:963975.
Jobe FW, Moynes DR, Tibone JE, Perry J.An EMG analysis
of the shoulder in pitching: a second report. Am ] Sports
Med. 1984;12:218-220.
Jobe FW, Tibone JE, Perry J, Moynes D. An EMG analysis
J Orthop Sports Phys Ther .Volume 30 Number 9 September 2000
19.
20.
21.
22.
23.
24.
25.
26.
of the shoulder in throwing and pitching. Am / Sports
Med. l993;ll:3-5.
Kendal FP, Kendal FM. Muscle Testing and Function. 3rd
ed. Baltimore, Md: Williams and Wilkins; 1983.
Kvitne RS, Jobe FW. The diagnosis and treatment of anterior instability in the throwing athlete. Clin Orthop.
1993;291:107-123.
Lintner SA, Levy A, Kenter K, Speer KP. Glenohumeral
translation in the asymptomatic athlete's shoulder and its
relationship to other clinically measurable anthropometric variables. Am / Sports Med. 1996;24:716-720.
Magnusson SP, Gleim GW, Nicholas JA. Shoulder weakness in professional baseball pitchers. Med Sci Sports Exerc. 1994;26:5-9.
Magnusson SP, Gleim GW, Nicholas JA. Subject variability of shoulder abduction strength testing. Am / Sports
Med. 1990;18:349-353.
Nies BYL, Richards NS, Asturias J. lntrarater and interrater
reliability of strength measurements of the biceps and deltoid using a hand held dynamometer. / Orthop Sports
Phys Ther. 1988;9:339.
Otis JC, Warren RF, Backus SI, Snatner TJ, Mabrey JD.
Torque production in the shoulder of the normal young
adult male. Am / Sports Med. l99O;l8:ll9-l23.
Pappas A, Zawacki RM, Sullivan TJ. Biomechanics of
J Orthop Sports Phys Ther .Volume SO. Number 9. September 2000
27.
28.
29.
30.
31.
32.
33.
baseball pitching: a preliminary report. Am J Sports Med.
1985;14:216-222.
Shrout E, Fleiss J. Interclass correlations: uses in assessing
rater reliability. Phsiological Bulletin. 1979;66:420-428.
Sullivan JS, Chesley A Herbert G, McFaull S, Scullion D.
The validity and reliability of hand-held dynamometer in
assessing isometric external rotator performance. / Orthop
Sports Phys The[ 1988;10:213-217.
Townsend H, Jobe FW,Pink M, Perry J. Electromyographic analysis of the glenohumeral muscles during a baseball
rehabilitation program. Am / Sports Med. 1991;19:264272.
Warner JJP, Micheli LJ, Arslanian LE, Kennedy J, Kennedy
R. Patterns of flexibility, laxity, and strength in normal
shoulders and shoulders with instability and impingement. Am / Sports Med. 1990;18:366-375.
Wilk KE, Andrews JR, Arrigo CA, Keirns MA, Erber DJ.
The strength characteristics of internal and external rotator muscles in professional baseball pitchers. Am / Sports
Med. 1993;2 1:61-66.
Wuelker N, Plitz W, Roetman B. Biomechanical data concerning the shoulder impingement syndrome. Clin Orthop. 1994;303:242-249.
Wuelker N, Schmotzer H, Thren K, Korell M. Translation
of the glenohumeral joint with simulated active elevation.
Clin Orthop. 1994;309: 193-200.