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Medicine
American Journal of Sports
DOI: 10.1177/0363546507303560
2007; 35; 1744 originally published online Jul 2, 2007; Am. J. Sports Med.
Cagnie and Erik E. Witvrouw
Ann M. Cools, Vincent Dewitte, Frederick Lanszweert, Dries Notebaert, Arne Roets, Barbara Soetens, Barbara
Rehabilitation of Scapular Muscle Balance: Which Exercises to Prescribe?
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1744
Shoulder pain and dysfunction are common complaints
among individuals seeking care from physical medicine and
rehabilitation specialists.
1,46
Recently, clinicians
25-27,36,42
and investigators
11,29,31,33
have focused increased attention
on the role of the scapula in the pathogenesis of shoulder
pain in general and impingement symptoms in particular.
Scapulothoracic dysfunction, defined as alterations in the
resting position or dynamic motion of the scapula, and
changes in scapular muscle recruitment can affect many
aspects of normal shoulder function.
24
An increasing num-
ber of studies have correlated abnormalities in scapular
position and motion (dyskinesis) with impingement symp-
toms, rotator cuff dysfunction, and instability.
18,29,31,34,48
Various authors have suggested that shoulder abnormali-
ties and abnormal scapular motions may be linked to global
weakness of the scapulothoracic muscles
8,9,15,16,38,43
; others
attribute scapular dyskinesis to scapular muscular imbal-
ance rather than absolute strength deficits.
8-10,29,40
In par-
ticular, excess activation of the upper trapezius (UT),
combined with decreased control of the lower trapezius (LT)
and the serratus anterior (SA), has been proposed as con-
tributing to abnormal scapular motion.
8-11,29,31,37,47
In view of the new insights and research findings on the
role of the scapula in shoulder pathologic abnormality,
Rehabilitation of Scapular Muscle Balance
Which Exercises to Prescribe?
Ann M. Cools,*
†
PT, PhD, Vincent Dewitte,
†
PT, Frederick Lanszweert,
†
PT,
Dries Notebaert,
†
PT, Arne Roets,
‡
MPSS, Barbara Soetens,
‡
PhD,
Barbara Cagnie,
†
PT, PhD, and Erik E. Witvrouw,
†
PT, PhD
From the
†
Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and
Health Sciences, University Hospital, Ghent, Belgium, and the
‡
Department of Developmental,
Personality and Social Psychology, Faculty of Psychology and Educational Sciences, Ghent
University, Ghent, Belgium
Background: Strengthening exercises for the scapular muscles are used in the treatment of scapulothoracic dysfunction related
to shoulder injury. In view of the intermuscular and intramuscular imbalances often established in these patients, exercises pro-
moting lower trapezius (LT), middle trapezius (MT), and serratus anterior (SA) activation with minimal activity in the upper trapez-
ius (UT) are recommended.
Hypothesis: Of 12 commonly used trapezius strengthening exercises, a selection can be performed for muscle balance reha-
bilitation, based on a low UT/LT, UT/MT, or UT/SA muscle ratio.
Study Design: Controlled laboratory study.
Methods: Electromyographic activity of the 3 trapezius parts and the SA was measured in 45 healthy subjects performing 12
commonly described scapular exercises, using surface electromyography.
Results: For each intramuscular trapezius ratio (UT/LT, UT/MT), 3 exercises were selected for restoration of muscle balance. The
exercises side-lying external rotation, side-lying forward flexion, prone horizontal abduction with external rotation, and prone
extension were found to be the most appropriate for intramuscular trapezius muscle balance rehabilitation. For the UT/SA ratio,
none of the exercises met the criteria for optimal intermuscular balance restoration.
Conclusion: In cases of trapezius muscle imbalance, some exercises are preferable over others because of their low UT/LT and
UT/MT ratios.
Clinical Relevance: In the selection of rehabilitation exercises, the clinician should have a preference for exercises with high acti-
vation of the LT and MT and low activity of the UT.
Keywords: shoulder rehabilitation; scapula; exercise; muscle balance; electromyography
*Address correspondence to Ann Cools, PT, PhD, University Hospital
Ghent, Department of Rehabilitation Sciences and Physiotherapy, De
Pintelaan 185, 6K3, B9000 Ghent, Belgium (e-mail: ann.cools@ugent.be).
No potential conflict of interest declared.
The American Journal of Sports Medicine, Vol. 35, No. 10
DOI: 10.1177/0363546507303560
© 2007 American Orthopaedic Society for Sports Medicine
© 2007 American Orthopaedic Society for Sports Medicine. All rights reserved. Not for commercial use or unauthorized distribution.
by MICHAEL L VOIGHT on October 2, 2007 http://ajs.sagepub.comDownloaded from
Vol. 35, No. 10, 2007 Rehabilitation of Scapular Muscle Balance 1745
current exercise protocols emphasize the importance of
scapular muscle training as an essential component of
shoulder rehabilitation.
3,5,12,20,22,28,35,42,49
Restoration of mus-
cle control and balanced coactivation in particular is a chal-
lenge to the clinician. For patients with an imbalance in the
scapular muscles, selective activation of the weaker muscle
parts with minimal activity in the hyperactive muscles is an
important component in the reduction of the imbalance.
Because a lack of activity in the LT, middle trapezius (MT),
and SA frequently is combined with excessive use of the UT,
the balance ratios UT/LT, UT/MT, and UT/SA are of particu-
lar importance.
10,11,29,47
In addition, integration of shoulder
girdle exercises into a global functional kinetic chain pat-
tern has become a treatment goal in shoulder rehabilitation,
specifically in overhead athletes.
5,14,25
The selection of appropriate exercises in the rehabilita-
tion of scapular muscle performance depends on the actual
strength of the muscles but also on the relative strength of
1 muscle in relation to another. In a study by Ludewig
et al,
30
a selection of exercises was introduced with a low
UT/SA ratio, meaning high activity in the SA with simulta-
neous minimal activation of the UT. However, no other
exercises have been described to optimize the muscle bal-
ance within the trapezius muscle by calculating UT/LT and
UT/MT muscle ratios. In addition, UT/SA ratios have not
been calculated for exercises other than push-up exercises.
Therefore, the purpose of this study was to determine the
UT/LT, UT/MT, and UT/SA muscle ratios for a number of
commonly used shoulder girdle strengthening exercises to
determine which exercises are appropriate to optimize scapu-
lar muscle balance.
MATERIALS AND METHODS
Subjects
Forty-five healthy volunteers (20 men, 25 women),
recruited from the student population, participated in the
study. Their mean age was 20.7 years (±1.7 years), mean
height was 1.73 m (±0.09 m), mean weight was 65.15 kg
(±10.89 kg), and mean body mass index was 21.75 (±2.39).
Exclusion criteria for participation in the study were a history
of cervical spine and shoulder injury or surgery, participation
in overhead sports at a competitive level, and upper limb
strength training for more than 5 hours per week. Inclusion
and exclusion criteria were assessed with a questionnaire.
Before participation, subjects read and signed the informed
consent form. The investigation was approved by the Ethical
Committee of Ghent University.
Instrumentation
Before electrode application, the skin was shaved if neces-
sary and prepared with alcohol to reduce skin impedance
(typically, <10 kΩ). Bipolar surface electrodes (Blue Sensor,
Medicotest, Ballerup, Denmark) were placed with a 2-cm
interelectrode distance over the upper, middle, and lower
portions of the trapezius muscle and the lower portions of
the SA muscle. Electrodes for the UT were placed midway
between the spinous process of the seventh cervical vertebra
and the posterior tip of the acromion process along the line
of the trapezius. The MT electrode was placed midway on a
horizontal line between the root of the spine of the scapula
and the third thoracic spine. The LT electrode was placed
obliquely upward and laterally along a line between the
intersection of the spine of the scapula with the vertebral
border of the scapula and the seventh thoracic spinous
process.
4,8,9,11
The last set of surface electrodes was applied
on the SA parallel to the muscle fibers, below the axilla,
anterior to the latissimus dorsi, and posterior to the pec-
toralis major.
12,28-30
A reference electrode was placed over the
clavicle. In all of the subjects, the dominant arm was tested.
Each set of bipolar recording electrodes from each of 4 mus-
cles was connected to a Noraxon Myosystem 2000 elec-
tromyographic (EMG) receiver (Noraxon USA, Scottsdale,
Ariz). The sampling rate was 1000 Hz. All raw myoelectric
signals were preamplified (overall gain = 1000, common rate
rejection ratio 115 dB, signal to noise ratio <1 µV RMS [root
mean square] baseline noise, filtered to produce a band-
width of 10-1000 Hz).
Testing Procedure
We began by recording the resting level of the electrical
activity of each muscle. Then, verification of EMG signal
quality was completed for each muscle by having the subject
perform maximal isometric contractions in manual muscle
test positions specific to each muscle of interest.
21,23
For the
UT muscle, resistance was applied to abduction of the arm
because Schludt and Harms-Ringdahl
41
found this position
superior to shoulder girdle elevation in activating the UT
muscle. The MT muscle was tested by applying resistance to
horizontal abduction in external glenohumeral rotation.
23
For LT testing, the arm was placed diagonally overhead in
line with the lower fibers of the trapezius. Resistance was
applied against further elevation.
23
Serratus anterior man-
ual muscle testing was performed by resisting humeral ele-
vation at an angle of 135° of forward flexion.
8,23
Subjects
performed three 5-second maximum voluntary isometric
muscle contractions against manual resistance by the princi-
pal investigator (A.C.). A 5-second pause occurred between
muscle contractions.
13,19
A metronome was used to control
duration of contraction. As a normalization reference,
EMG data were collected during maximal voluntary con-
traction (MVC) for each muscle. After signal filtering with
a low-pass filter (single pass, Butterworth, 6-Hz low-pass
filter of the sixth order) and visual inspection for artifacts,
the peak average EMG value over a window of 1 second
was calculated for each trial. Further calculations were
performed with the mean of the repeated trials as a nor-
malization value (100%).
Each subject performed a series of 12 exercises, which
were randomized to avoid systematic influences of fatigue
and learning effects. The exercises were selected based on a
literature review.
2,5-7,12,17,20,22,28,32,35,44,45,49
Numerous studies
have been conducted examining individual muscle activity
during commonly used rehabilitation exercises. In general,
exercises are considered to be relevant for a certain muscle
© 2007 American Orthopaedic Society for Sports Medicine. All rights reserved. Not for commercial use or unauthorized distribution.
by MICHAEL L VOIGHT on October 2, 2007 http://ajs.sagepub.comDownloaded from
1746 Cools et al The American Journal of Sports Medicine
or muscle group if high EMG amplitudes are provoked.
Table 1 summarizes the results of the literature review with
respect to muscle activity of the 3 trapezius parts. On the
basis of the results of these previous investigations, a group
of 12 exercises was selected as relevant for the 3 trapezius
parts. The 12 exercises are described in Table 2. All exer-
cises, with the exception of the exercises performed in
side-lying position, were completed bilaterally. Before data
collection, the exercises were performed without resistance
for familiarization purposes. Each exercise was performed in
3 phases—a concentric, isometric, and eccentric phase, each
during 3 seconds. A metronome was used to control the
duration of the phases. Subjects completed 5 trials of each
exercise. Between trials, a resting period of 3 seconds was
provided. Subjects were allowed to rest for 2 minutes
between exercises. During each exercise, verbal encourage-
ment and, if necessary, performance corrections were given
by the same examiner.
The amount of weight used by the subjects, or resistance
given by the pulley apparatus, was determined based on
gender and body weight (see Appendix A, Tables 1A and 2A,
in the online version of this article at http://ajsm.sagepub
.com/cgi/content/full/35/10/1744/DC1). Subjects were divided
into genders and into 3 subgroups based on their weight for
resistance determination.
Signal Processing and Data Analysis
All raw EMG signals were analog/digital converted (12-bit
resolution) at 1000 Hz. They were digitally fully wave-
rectified and low-pass filtered (single pass, Butterworth,
6-Hz low-pass filter of the sixth order). Results were nor-
malized to the maximum activity measured during the MVC
trials. The EMG data for each muscle and each subject were
averaged for each phase across the 3 intermediate repeti-
tions of the 5 repetitions completed. Periods were defined by
markers based on the 3-second phases of the exercises. One-
second markers were automatically placed on the EMG
signal, based on the metronome sound. The mean amplitude
EMG signal, expressed as a percentage of MVC, was used to
assess the activity of the 3 parts of the trapezius muscle and
the SA muscle in each of the 12 exercises.
Statistical Analysis
A priori power analysis for this study was set at 80%, based
on an α level of .05, resulting in a minimal sample size of 40.
Means and standard deviations were calculated across sub-
jects for the normalized UT, MT, LT, and SA EMG values of
each of the 3 phases of the 12 exercises. Because the specific
topic of interest of this study was to investigate muscle bal-
ance ratios among the scapular muscles during the selected
exercises, the relative activity of the UT with respect to the
MT and LT and to the SA was determined. Intermuscular
and intramuscular ratios were calculated by dividing nor-
malized EMG values of the UT by normalized EMG values
of the LT, MT, and SA, resulting in the ratios UT/LT, UT/MT,
and UT/SA. These values were multiplied by 100 to obtain
relative activity of UT (in %) compared with the other scapu-
lar muscles. Values <100% reflect muscle activity of the MT,
LT, or SA being superior compared with UT, with lower val-
ues suggesting lower relative UT activity. Values >100%
reflect muscle activity of UT exceeding muscle activity of the
other scapular muscles. Means and standard deviations
were calculated for the 3 ratios.
Because all data were normally distributed with equal
variances, parametric tests were used for statistical analy-
sis. The dependent variables of interest were the UT/LT,
UT/MT, and UT/SA ratios. Each of these ratios was ana-
lyzed using a general linear model analysis of variance
with 2 within-subject factors: phase (3 levels) and exercises
(12 levels). In case of significant Mauchly test results for
sphericity, Greenhouse-Geisser correction was performed.
The α level for the analysis of variance was set at .05.
Before further statistical analysis, exercises were catego-
rized in terms of accuracy by performing 1-sample t tests for
each ratio and each phase, with 100%, 80%, and 60% as ref-
erence values. Ratios not significantly lower than 100% sug-
gest that the UT is more active than the LT, MT, and SA
muscle and are considered inadequate for the purpose of our
study. Ratios significantly lower than 100% refer to exercises
relevant to our research question as we wanted to determine
exercises in which the LT, MT, and SA are activated with
minimal activation of the UT muscle. In this group, exercises
were additionally divided into 3 subgroups based on the
ratio: 100% to 80% (moderate), 80% to 60% (good), and <60%
(excellent). For each ratio, the 3 best exercises were used for
further analysis. Classification was based on the following
criteria: exercises in which in each phase, the ratio is smaller
than 60% (category 1); exercises in which in each phase,
the ratio is smaller than 80%, with at least 1 phase having a
ratio between 60% and 80% (category 2); exercises with a
ratio significantly smaller than 100%, with at least 1 phase
between the 60% to 80% limits (category 3); and exercises
with at least 1 of the 3 phases significantly higher than 100%
(category 4). Exercises from category 4 were excluded for fur-
ther analysis and discussion.
TABLE 1
Exercises Commonly Used for Trapezius Training
a
Exercise Movement UT MT LT Reference(s)
Abduction xxx 22,35
Forward flexion xx22,34,35,39
Dynamic hug x 7,12,39
External rotation x 2
Extension xx 7,22,35
Horizontal abduction
(neutral or
external rotation) xxx 7,22,35
Military press x 17,35
Rowing (low or high) xxx 17,20,35
Scaption (neutral or
external rotation) xxx2,12,22,35
Scapular retraction xx 7,22
Shoulder shrug x 12,22
a
UT, upper trapezius; MT, middle trapezius; LT, lower trapezius.
© 2007 American Orthopaedic Society for Sports Medicine. All rights reserved. Not for commercial use or unauthorized distribution.
by MICHAEL L VOIGHT on October 2, 2007 http://ajs.sagepub.comDownloaded from
Vol. 35, No. 10, 2007 Rehabilitation of Scapular Muscle Balance 1747
Across the 3 selected exercises from categories 1 to 3,
multiple pair-wise comparisons were performed for each
phase using paired-sample t tests with Bonferroni correc-
tion. All statistical analyses were performed with SPSS
version 12.0 for Windows (SPSS Science, Chicago, Ill).
RESULTS
The results of the descriptive analysis of the normalized
EMG data for the 12 exercises over the 3 phases are sum-
marized in the online version of this article (see Appendix
A, Table 3A, at http://ajsm.sagepub.com/cgi/content/full/
35/10/1744/DC1). As the major topic of interest of this
study was intermuscular and intramuscular ratios during
shoulder exercises, the mean normalized EMG activity of
each individual muscle across phases was not taken into
account for further statistical analysis and is only stated
for descriptive purposes.
Results of the calculations of the ratios UT/LT, UT/MT,
and UT/SA are summarized in the online version of this
article (see Appendix A, Table 4A, at http://ajsm.sagepub
.com/cgi/content/full/35/10/1744/DC1). The generalized lin-
ear model analysis of variance for repeated measures showed
significant main effects for exercise: F(2.32,102.15) = 28.42,
P < .001; F(1.52,67.07) = 30.86, P < .001; and F(2.79,
122.56) = 37.53, P < .001 for the UT/LT, UT/MT, and UT/SA
ratios, respectively. A significant main effect of phase was also
obtained for all ratios: F(1.59,69.87) = 6.86, P = .004; F(2.88,
138.25) = 16.18, P = .001; and F(1.44,63.24) = 24.54, P = .001
for the UT/LT, UT/MT, and UT/SA ratios, respectively.
Importantly, the data revealed an additional exercise × phase
interaction effect for each ratio: F(2.29,100.76) = 4.71, P = .008
for UT/LT; F(3.85,169.32) = 10.24, P = .001 for UT/MT; and
F(4.17,183.67) = 15.48, P = .001 for UT/SA.
Before post hoc statistical analysis, 1-sample t tests were
performed with 100%, 80%, and 60% as reference values
for all ratios across phases and exercises to classify the
exercises based on their relevance (see Appendix A, Table
5A, at http://ajsm.sagepub.com/cgi/content/full/35/10/1744/
DC1). Based on these criteria, the exercises side-lying for-
ward flexion (Figure 1A), side-lying external rotation
(Figure 1B), and horizontal abduction with external rota-
tion (Figure 1C) were selected as relevant exercises with
low UT/LT ratios. For the UT/MT ratio, side-lying forward
flexion and side-lying external rotation were again
selected as relevant for this ratio, in addition to the prone
extension exercise (Figure 1D). For the UT/SA ratio, no
exercise met the criteria of category 1. Only 1 exercise, high
TABLE 2
Description of the 12 Exercises Performed by the Study Subjects
Exercise Material Description
Prone shoulder Dumbbell Subject prone with the shoulder in neutral position; subject performs shoulder abduction
abduction to 90° with external rotation in a horizontal plane
Forward flexion Dumbbells Subject standing with shoulder in neutral position; subject performs maximal forward
flexion in a sagittal plane
Forward flexion in Dumbbell Subject in side-lying position, shoulder in neutral position; subject performs forward
side-lying position flexion in a horizontal plane to 135°
High row Vertical pulley Subject standing in front of vertical pulley apparatus with the shoulders in
apparatus 135° forward flexion; subject performs an extension with the shoulders until neutral
and V-bar position
Horizontal abduction Dumbbells Subject prone with the shoulders resting in 90° forward flexion; subject performs
horizontal abduction to horizontal position
Horizontal abduction Dumbbells Subject prone with the shoulders resting in 90° forward flexion; subject performs
with external rotation horizontal abduction to horizontal position, with an additional external rotation of the
shoulder at the end of the movement
Low row (1) Pulley apparatus Subject standing in front of pulley apparatus, shoulders in 45° forward flexion and
with 2 handles neutral rotation; subject performs extension with the elbows extended
Low row (2) Pulley apparatus Subject standing in front of pulley apparatus, shoulders in 45° forward flexion and
with 2 handles neutral rotation; subject performs extension with the elbows flexed
Prone extension Dumbbells Subject prone with the shoulders resting in 90° forward flexion; subject performs
extension to neutral position with the shoulder in neutral rotational position
Rowing in sitting Pulley apparatus Subject sitting in front of pulley apparatus with the shoulders in 90° forward flexion;
position with 2 handles subject performs an extension movement with the elbows flexed and in the horizontal
plane
Scaption with external Dumbbells Subject sitting with the arms at the side; subject performs maximal elevation of the arms
rotation in the plane of the scapula (30° anterior of the frontal plane)
Side-lying external Dumbbell Subject side-lying with the shoulder in neutral position and the elbow flexed 90°; subject
rotation performs external rotation of the shoulder (with towel between trunk and elbow to
avoid compensatory movements)
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by MICHAEL L VOIGHT on October 2, 2007 http://ajs.sagepub.comDownloaded from
1748 Cools et al The American Journal of Sports Medicine
row (Figure 2), reached the criterion of category 2. The exer-
cises forward flexion (Figure 3) and scaption with external
rotation (Figure 4) were further selected within the 3 best
exercises—however, with moderate accuracy (category 3).
For the 3 best exercises, post hoc t tests with Bonferroni
correction were performed across the phases to see
whether some phases were more accurate than others in
terms of adequate muscle ratios.
Figure 1. Exercises to restore intramuscular trapezius muscle balance. A, forward flexion in side-lying position; B, side-lying
external rotation; C, horizontal abduction with external rotation; and D, prone extension. The results of this study suggest that
the exercises A, B, and C are optimal for restoration of UT/LT muscle imbalances, and A, B, and D are optimal for restoration of
UT/MT muscle imbalances. UT, upper trapezius; LT, lower trapezius; MT, middle trapezius.
Figure 2. High row exercise.
Figure 3. Forward flexion in standing position.
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by MICHAEL L VOIGHT on October 2, 2007 http://ajs.sagepub.comDownloaded from
Vol. 35, No. 10, 2007 Rehabilitation of Scapular Muscle Balance 1749
DISCUSSION
The purpose of this investigation was to identify scapular
muscle strengthening exercises in which the LT, MT, and
SA muscles are optimally activated with minimal partici-
pation of the UT. Our results support the hypothesis that,
out of a number of commonly used rehabilitation exercises,
exercises with optimal muscle balance ratios may be
selected based on EMG analysis.
Three exercises were selected as exercises with a low
UT/LT ratio: side-lying external rotation, side-lying for-
ward flexion, and prone horizontal abduction with exter-
nal rotation. Previous investigations have shown that the
side-lying external rotation exercise enhances activity in
the supraspinatus, infraspinatus, teres minor, and poste-
rior deltoid.
44
Ballantyne et al
2
also demonstrated high
levels of EMG activity in the LT muscle when the shoul-
der was externally rotated with the patient in a prone
position. Performing the exercise in a side-lying position
possibly minimizes UT activity by eliminating gravity
and thus minimizing the postural role of that muscle.
Probably for the same reason, side-lying forward flexion
gives minimal UT activity. In both these exercises, the
isometric phase revealed the lowest UT/LT ratio. This
emphasizes the importance of controlled contraction
throughout the required range of motion, with a “hold”
phase at maximal external rotation or 135° of forward
flexion. Moreover, our results suggest that patients with
UT/LT imbalances should not perform forward flexion
movements in the standing position because of excessive
activity in the UT.
The horizontal abduction with external rotation exercise
frequently is promoted for optimal shoulder rehabilita-
tion.
35,44
Townsend et al
44
as well as Moseley et al
35
included
this exercise in their selection for glenohumeral and scapu-
lothoracic muscle strengthening programs. Our results
confirm the clinical relevance of this exercise and empha-
size the additional advantage of optimal muscle balance
restoration capacity. In addition, our results show that the
additional external rotation performed during the isomet-
ric phase is essential for selection into the top 3 of all exer-
cises. Overall across phases, the horizontal abduction with
external rotation exercise reveals lower UT/LT ratios than
the horizontal abduction exercise.
Surprisingly, no rowing exercise was selected based on
low UT/LT ratio. However, clinical papers often suggest this
exercise for LT strength training.
5,6,26,35,38,39
Our results
show not only that throughout these exercises, mean EMG
activity of the LT is rather low, but also that the ratios are
not in favor of the LT. Further investigation on different
exercise modalities, for example, prone versus standing
position and integration of other parts of the kinetic chain
into the exercise, are needed to evaluate the therapeutic
value of this exercise in the restoration of scapular muscle
balance.
Our analysis of exercises with optimal UT/MT ratios
resulted in 3 exercises, of which 2 were already selected
based on low UT/LT ratio. Indeed, it seems that both exer-
cises, side-lying external rotation and side-lying forward
flexion, optimally recruit the MT with minimal activity in
the UT. As a previous study showed that overhead athletes
with impingement symptoms show decreased activity in
the LT as well as in the MT with excessive activation of the
upper part,
10
these exercises may be used for restoration of
both muscle imbalances.
A third exercise, selected on the basis of low UT/MT ratio,
was prone extension. Moseley et al
35
found the MT to be
highly activated during the prone extension movement.
Our results confirm the accuracy of this movement for
training this muscle part, with minimal UT activation.
Notable is the finding that performing an extension move-
ment in standing position, such as during the high and low
row exercises, does not result in optimal UT/MT ratios. As
in the UT/LT exercises, body position apparently influences
individual muscle activity and hence intramuscular activ-
ity ratios.
No exercise met the criteria for selection in optimizing
UT/SA ratio. This means that of the exercises performed in
this investigation, none can be qualified for SA training with
inhibition of the UT. This finding is probably the result of
the criteria we used to select our exercises. Indeed, during
our literature research, the main topic of interest was find-
ing commonly prescribed exercises for trapezius training,
rather than SA. None of the exercises selected in our inves-
tigation were previously promoted specifically to enhance
SA strength. Intermuscular balance ratios between SA and
UT were already examined by Ludewig et al.
30
Our exercises
have overall higher ratios than the exercises selected in the
Ludewig
30
study. Indeed, the push-up exercise, examined in
that study with a variety of modalities, is considered to be
an optimal exercise in SA training. Ludewig et al
30
reported
generally low UT/SA ratios (<30%) for all phases throughout
all push-up modalities, with the exception of the eccentric
nonplus phase. Our UT/SA ratios vary from 50.51% in the
isometric phase of the high row exercise to 467.60% during
the isometric phase of the horizontal abduction with exter-
nal rotation exercise. Based on our results, optimal UT/SA
exercises cannot be identified.
In general, the EMG values of the active muscles are
lower in our investigation, compared with those in the
Moseley
35
study examining EMG activity during a variety
of commonly used shoulder rehabilitation exercises.
Figure 4. Scaption with external rotation.
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by MICHAEL L VOIGHT on October 2, 2007 http://ajs.sagepub.comDownloaded from
1750 Cools et al The American Journal of Sports Medicine
Differences in methods and determination of testing
weight may account for these differences. Therefore, as the
purpose of our study was to evaluate balance ratios rather
than individual normalized muscle activity, our EMG data
for each individual muscle were not taken into account for
further statistical analysis and should be compared with
other studies with caution.
Some limitations of our investigation should be noted. The
use of surface electromyography during dynamic movements
has been a topic of discussion in literature regarding skin
displacement, movement artifacts, influences of contraction
modalities on the EMG signals, and normalization meth-
ods.
13,19
In general, systematic control of all interfering fac-
tors during the test is recommended to obtain reliable EMG
data in a noninvasive manner. On the basis of these recom-
mendations, our investigation was executed with maximal
standardization and accuracy. In addition, we did not obtain
synchronized kinematic data during the exercises to stan-
dardize the procedure, like in some other studies.
2,20,28,30
Although numerous investigations have been performed
without simultaneous kinematic movement analysis,
12,35,44
we have to acknowledge this limitation. For further discus-
sion on the technical issues of the use of surface electromyo-
graphy during dynamic movements, see Appendix B in the
online version of this article at http://ajsm.sagepub.com/cgi/
content/full/35/10/1744/DC1).
From a clinical point of view, the major limitation of this
study can be found in the outcome itself. Indeed, all the exer-
cises selected for a low UT/LT or UT/MT ratio are performed
in a lying position, prone or side-lying. However, recent lit-
erature emphasizes the importance of functional exercises,
resembling daily or sport-specific arm function, and integra-
tion of the shoulder rehabilitation exercise into a functional
kinetic chain.
5,14,25
These treatment goals are very difficult
to accomplish with the patient lying prone or on his or her
side. Diagonal patterns, combined with trunk and lower
limb stabilization, as promoted by a number of authors,
14,25
are not possible in our exercise modalities. Therefore, we
propose our exercises to be performed in the early stages of
rehabilitation and before more functional kinetic chain exer-
cises, in which functional muscle recruitment patterns can
be trained with normalized intermuscular and intramuscu-
lar balance ratios.
Our data were obtained from a group of young, healthy
subjects with no history of shoulder impairment. It should
be noted that extrapolation of our results to patients with
shoulder injury or other age categories should be per-
formed with caution. On the basis of our results, we cannot
conclude that patients suffering from shoulder pain or
local muscle imbalances will show similar muscle balance
ratios performing the exercises we propose. Our study may
be considered as a first step in the investigation of reha-
bilitation exercises for the restoration of trapezius muscle
balance, where the use of noninjured subjects must be rec-
ognized as a clinical limitation.
On the basis of our research question and our results, we
believe further examinations should be performed.
Bilateral versus unilateral movements should be com-
pared, as well as the influence on unilateral versus bilat-
eral stance during the exercises in standing positions, and
the influence of lumbar and thoracic spine position. In
addition, it may be interesting to obtain data from other
muscles beyond the SA and the trapezius that can con-
tribute to scapular movement and control, which were not
considered in this study.
CONCLUSION
We investigated the activation of the 3 trapezius muscle
parts and the SA muscle during 12 commonly used shoulder
girdle rehabilitation exercises and calculated intermuscular
and intramuscular balance ratios. This is the first study cal-
culating balance ratios of trapezius activity during these
exercises. Based on our results, we suggest the use of side-
lying external rotation, side-lying forward flexion, prone hor-
izontal abduction with external rotation, and prone
extension exercises to promote LT and MT activity with min-
imal activation of the UT part. These results may help the
clinician in the treatment of scapular muscle imbalances.
REFERENCES
1. Andrews JR. Diagnosis and treatment of chronic painful shoulder:
review of nonsurgical interventions. Arthroscopy. 2005;21:333-347.
2. Ballantyne B, O’Hare S, Pschall J, et al. Electromyographic activity of
selected shoulder muscles in commonly used therapeutic exercises.
Phys Ther. 1993;73:668-677.
3. Bang MD, Deylen GD. Comparison of supervised exercises with and
without manual physical therapy for patients with shoulder impinge-
ment symptoms. J Orthop Sports Phys Ther. 2000;30:126-137.
4. Basmajian JV, De Luca CJ. Muscles Alive: Their Functions Revealed by
Electromyography. 5th ed. Baltimore, Md: Williams & Wilkins; 1985.
5. Burkhart S, Morgan C, Kibler W. The disabled shoulder: spectrum of
pathology part III: the SICK scapula, scapular dyskinesis, the kinetic
chain, and rehabilitation. Arthroscopy. 2003;19:641-661.
6. Burkhead WZ, Rockwood CA. Treatment of instability of the shoulder
with an exercise program. J Bone Joint Surg Am. 1992;74:890-896.
7. Cools A, Walravens M. Exercise Therapy for Shoulder Disorders.
Antwerpen, Belgium: Standaard Uitgeverij; 2005.
8. Cools A, Witvrouw E, Declercq G, Vanderstraeten G, Cambier D.
Evaluation of isokinetic force production and associated muscle
activity in the scapular rotators during a protraction-retraction move-
ment in overhead athletes with impingement symptoms. Br J Sports
Med. 2004;38:64-68.
9. Cools A, Witvrouw E, Mahieu N, Danneels L. Isokinetic scapular
muscle performance in overhead athletes with and without impinge-
ment symptoms. J Athl Train. 2005;40:104-110.
10. Cools AM, Declercq GA, Cambier DC, Mahieu NM, Witvrouw EE.
Trapezius activity and intramuscular balance during isokinetic exer-
cise in overhead athletes with impingement symptoms. Scand J Med
Sci Sports. 2007;17:25-33.
11. Cools AM, Witvrouw EE, Declercq GA, Danneels LA, Cambier DC.
Scapular muscle recruitment patterns: trapezius muscle latency with
and without impingement symptoms. Am J Sports Med. 2003;31:
542-549.
12. Decker M, Hintermeister R, Faber K, Hawkins R. Serratus anterior
muscle activity during selected rehabilitation exercises. Am J Sports
Med. 1999;27:784-791.
13. De Luca C. The use of surface electromyography in biomechanics. J
Appl Biomech. 1997;13:135-163.
14. Ellenbecker TS, Davies GJ. Closed Kinetic Chain Exercise: A Com-
prehensive Guide to Multiple-Joint Exercises. Leeds, UK: Human
Kinetics; 2001.
15. Glousman R. Electromyographic analysis and its role in the athletic
shoulder. Clin Orthop Relat Res. 1993;288:27-34.
© 2007 American Orthopaedic Society for Sports Medicine. All rights reserved. Not for commercial use or unauthorized distribution.
by MICHAEL L VOIGHT on October 2, 2007 http://ajs.sagepub.comDownloaded from
Vol. 35, No. 10, 2007 Rehabilitation of Scapular Muscle Balance 1751
16. Glousman RE, Jobe FW, Tibone J, Moynes D, Antonelli D, Perry J.
Dynamic electromyographic analysis of the throwing shoulder with
glenohumeral instability. J Bone Joint Surg Am. 1988;70:220-226.
17. Gokeler A, Lehmann M, Matthijs O, Kentsch A. Tennis: rehabilitation,
training and tips. Sports Med Arthrosc Rev. 2001;9:105-113.
18. Hallstrom E, Karrholm J. Shoulder kinematics in 25 patients with
impingement and 12 controls. Clin Orthop Relat Res. 2006;448:22-27.
19. Hancock R, Hawkins R. Applications of electromyography in the throw-
ing shoulder. Clin Orthop Relat Res. 1996;330:84-97.
20. Hintermeister R, Lange G, Schultheis J, Bey M, Hawkins R.
Electromyographic activity and applied load during shoulder rehabilita-
tion exercises using elastic resistance. Am J Sports Med. 1998;26:
210-220.
21. Hishop HJ, Montgomory J. Daniels and Worthingham’s Muscle Testing:
Techniques of Manual Examination. 6th ed. Philadelphia, Pa: WB
Saunders Co; 1995.
22. Kamkar A, Irrgang J, Whitney S. Non-operative management of sec-
ondary shoulder impingement syndrome. J Orthop Sports Phys Med.
1993;17:212-224.
23. Kendall FP, Kendall EK. Muscles, Testing and Function. Baltimore, Md:
Williams & Wilkins; 1993.
24. Kibler WB. Classification and treatment of scapular pathology. In:
Ellenbecker TS, ed, Shoulder Rehabilitation. Non-Operative Treatment.
New York, NY: Thieme; 2006:94-103.
25. Kibler WB. The role of the scapula in athletic shoulder function. Am
J Sports Med. 1998;26:325-337.
26. Kibler WB, McMullen J. Scapular dyskinesis and its relation to shoul-
der pain. J Am Acad Orthop Surg. 2003;11:142-151.
27. Kibler WB, Safran M. Tennis injuries. Med Sport Sci. 2005;48:120-137.
28. Lear L, Gross M. An electromyographical study of the scapular stabil-
ising synergists during a push-up progression. J Orthop Sports Phys
Ther. 1998;28:146-157.
29. Ludewig P, Cook T. Alterations in shoulder kinematics and associated
muscle activity in people with symptoms of shoulder impingement.
Phys Ther. 2000;80:276-291.
30. Ludewig P, Hoff M, Osowski E, Meschke S, Rundquist P. Relative bal-
ance of serratus anterior and upper trapezius muscle activity during
push-up exercises. Am J Sports Med. 2004;32:484-493.
31. Lukasiewicz A, McClure P, Michiner L, Pratt N, Sennet B. Comparison
of 3-dimensional scapular position and orientation between subjects
with and without shoulder impingement. J Orthop Sports Phys Ther.
1999;29:574-586.
32. Mc Cann PD, Wootten ME, Kabada MP, Bigliani LU. A kinematic and
electromyographic study of shoulder rehabilitation exercises. Clin
Orthop Relat Res. 1993;288:179-188.
33. McClure PW, Bialker J, Neff N, Williams G, Karduna A. Shoulder function
and 3-dimensional kinematics in people with shoulder impingement
syndrome before and after a 6-week exercise program. Phys Ther.
2004;84:832-848.
34. McClure PW, Michiner LA, Karduna AR. Shoulder function and
3-dimensional scapular kinematics in people with and without shoul-
der impingement syndrome. Phys Ther. 2006;86:1075-1090.
35. Moseley J, Jobe F, Pink M, Perry J, Tibone J. EMG analysis of the
scapular muscles during a shoulder rehabilitation program. Am J Sports
Med. 1992;20:128-134.
36. Mottram S. Dynamic stability of the scapula. Man Ther. 1997;2:123-131.
37. Peat M, Grahama R. Electromyographic analysis of soft tissue lesions
affecting shoulder function. Am J Phys Med. 1977;56:223-240.
38. Pink MM, Tibone JE. The painful shoulder in the swimming athlete.
Orthop Clin North Am. 2000;31:247-261.
39. Rubin BD, Kibler WB. Fundamental principles of shoulder rehabilita-
tion: conservative to postoperative management. Arthroscopy. 2002;
18:29-39.
40. Sahrman S. Diagnosis and Treatment of Movement Impairment
Syndromes. St Louis, Mo: Mosby; 2002.
41. Schludt K, Harms-Ringdahl K. Activity levels during isometric test con-
tractions of the neck and shoulder muscles. Scand J Rehabil Med.
1988;20:117-127.
42. Schmitt L, Snyder-Mackler L. Role of scapular stabilizers in etiology
and treatment of impingement syndrome. J Orthop Sports Phys Ther.
1999;29:31-38.
43. Scovazzo M, Browne A, Pink M, Jobe F, Kerrigan J. The painful shoul-
der during freestyle swimming: an electromyographic and cinemato-
graphic analysis of twelve muscles. Am J Sports Med. 1991;19:
577-582.
44. Townsend H, Jobe FW, Pink M, Perry J. Electromyographic analysis of
the glenohumeral muscles during a baseball rehabilitation program.
Am J Sports Med. 1991;19:264-272.
45. Uhl TL, Carver TJ, Mattacola CG, Mair SD, Nitz AJ. Shoulder muscu-
lature activation during upper extremity weight-bearing exercise.
J Orthop Sports Phys Ther. 2003;33:109-117.
46. Urwin M, Symmons D, Allison T, et al. Estimating the burden of mus-
culoskeletal disorders in the community: the comparative prevalence
of symptoms at different anatomical sites, and the relation to social
deprivation. Ann Rheum Dis. 1998;57:649-655.
47. Wadsworth DJS, Bullock-Saxton JE. Recruitment patterns of the
scapular rotator muscles in freestyle swimmers with subacromial
impingement. Int J Sports Med. 1997;18:618-624.
48. Warner J, Micheli L, Arslanian L, Kennedy J, Kennedy R. Scapulotho-
racic motion in normal shoulders and shoulders with glenohumeral
instability and impingement: a study using Moiré topographic analysis.
Clin Orthop Relat Res. 1992;285:191-199.
49. Wilk KE, Meister K, Andrews JR. Current concepts in the rehabilitation
of the overhead throwing athlete. Am J Sports Med. 2002;30:136-151.
© 2007 American Orthopaedic Society for Sports Medicine. All rights reserved. Not for commercial use or unauthorized distribution.
by MICHAEL L VOIGHT on October 2, 2007 http://ajs.sagepub.comDownloaded from
