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BioMed Central
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Sports Medicine, Arthroscopy,
Rehabilitation, Therapy & Technology
Open Access
Research
Impact of movement training on upper limb motor strategies in
persons with shoulder impingement syndrome
Jean-Sébastien Roy*1, Hélène Moffet1,2, Bradford J McFadyen1,2 and
Richard Lirette3
Address: 1Centre for Interdisciplinary Research in Rehabilitation and Social Integration, Quebec City, Canada, 2Department of Rehabilitation,
Faculty of Medicine, Laval University, Quebec City, Canada and 3Club Entrain Medical Centre, Quebec City, Canada
Email: Jean-Sébastien Roy* - jean-sebastien.roy.1@ulaval.ca; Hélène Moffet - helene.moffet@rea.ulaval.ca;
Bradford J McFadyen - brad.mcfadyen@rea.ulaval.ca; Richard Lirette - rlirette@mediom.qc.ca
* Corresponding author
Abstract
Background: Movement deficits, such as changes in the magnitude of scapulohumeral and scapulathoracic
muscle activations or perturbations in the kinematics of the glenohumeral, sternoclavicular and
scapulothoracic joints, have been observed in people with shoulder impingement syndrome. Movement
training has been suggested as a mean to contribute to the improvement of the motor performance in
persons with musculoskeletal impairments. However, the impact of movement training on the movement
deficits of persons with shoulder impingement syndrome is still unknown. The aim of this study was to
evaluate the short-term effects of supervised movement training with feedback on the motor strategies of
persons with shoulder impingement syndrome.
Methods: Thirty-three subjects with shoulder impingement were recruited. They were involved in two
visits, one day apart. During the first visit, supervised movement training with feedback was performed.
The upper limb motor strategies were evaluated before, during, immediately after and 24 hours after
movement training. They were characterized during reaching movements in the frontal plane by EMG
activity of seven shoulder muscles and total excursion and final position of the wrist, elbow, shoulder,
clavicle and trunk. Movement training consisted of reaching movements performed under the supervision
of a physiotherapist who gave feedback aimed at restoring shoulder movements. One-way repeated
measures ANOVAs were run to analyze the effect of movement training.
Results: During, immediately after and 24 hours after movement training with feedback, the EMG activity
was significantly decreased compared to the baseline level. For the kinematics, total joint excursion of the
trunk and final joint position of the trunk, shoulder and clavicle were significantly improved during and
immediately after training compared to baseline. Twenty-four hours after supervised movement training,
the kinematics of trunk, shoulder and clavicle were back to the baseline level.
Conclusion: Movement training with feedback brought changes in motor strategies and improved
temporarily some aspects of the kinematics. However, one training session was not enough to bring
permanent improvement in the kinematic patterns. These results demonstrate the potential of movement
training in the rehabilitation of movement deficits associated with shoulder impingement syndrome.
Published: 17 May 2009
Sports Medicine, Arthroscopy, Rehabilitation, Therapy & Technology 2009, 1:8 doi:10.1186/1758-2555-1-8
Received: 15 April 2009
Accepted: 17 May 2009
This article is available from: http://www.smarttjournal.com/content/1/1/8
© 2009 Roy et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Sports Medicine, Arthroscopy, Rehabilitation, Therapy & Technology 2009, 1:8 http://www.smarttjournal.com/content/1/1/8
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Background
Movement deficits have been observed in persons with
musculoskeletal disorders [1-3]. A cortical reorganization
consecutive to peripheral impairments may explain such
deficits [4-6]. Interestingly, it has been demonstrated that
movement training can induce change in the cortical
organization of healthy subjects [7] and contribute to the
improvement of the motor performance in persons with
peripheral impairments [2,8]. In order to efficiently reha-
bilitate the deficits, movement training should, however,
be based on the best strategies available to favour motor
learning. Factors such as the use of instruction, demon-
stration and extrinsic feedback during movement training
have been proved to promote motor learning [9-11].
Among them, extrinsic feedback is one of the most potent
factors [10]. Extrinsic feedback is given by an external
source and provides error information that can be used in
addition to the person's own intrinsic error signals [9].
According to Fitts & Posner [12], the first phase of learning
is the cognitive stage where one has to solve the problem
and decide what to do. It is during this stage that the use
of extrinsic feedback is thought to be the most effective
since it brings awareness to movement deficits [11].
Shoulder impingement syndrome (SIS) has been
described as a repeated mechanical compression of the
subacromial structures under the coracoacromial arch
during arm elevation [13]. Studies suggest that persons
with SIS may benefit from movement training with extrin-
sic feedback. Indeed, it was shown that they present move-
ment deficits during arm elevation. These deficits range
from changes in the magnitude of scapulohumeral and
scapulathoracic muscle activations [14-16], to perturba-
tions in the kinematics of the scapula (increased or
decreased scapular posterior tilting and lateral rotation)
[14,17,18], clavicle (increased elevation and retraction)
[18,19] and humeral head (superior displacement with
respect of the glenoid) [20] during arm movement. These
deficits most likely contribute to impingement of the sub-
acromial structures and subsequent pain during arm
movement.
The nature and importance of these deficits differ among
persons with SIS [18,19,21]. It has been shown that half
of the persons with SIS used a different motor strategy
compared to a control group during reaching tasks in the
frontal plane [19]. Specifically, these persons used more
trunk rotation and clavicular elevation, and finished
reaching with the trunk more rotated, clavicle more ele-
vated and shoulder in a more anterior plane of elevation.
The explanation for these results is that such movement
strategies may be used to protect the impaired shoulder
following superior displacement of the humeral head dur-
ing arm elevation [19,20]. By using more trunk rotation,
persons with SIS elevate their arm in a manner that pre-
vents them from going into the frontal plane where the
subacromial space is minimal [22]. Furthermore, by ele-
vating their clavicle, they can reach the target even though
the humeral head is superiorly migrated. It suggests that at
least a portion of the persons with SIS present deficits that
could be rehabilitated by movement training. Reduction
of these impairments could be an important factor in
reaching a normal level of shoulder function.
It is still unknown how the motor strategies of persons
with SIS are influenced by movement training. In fact, the
effects of movement training have never been evaluated
for persons with SIS on variables related to motor control,
such as muscular activation or kinematic patterns. The
aim of this study was to evaluate the immediate and short-
term effects of movement training with extrinsic feedback
on the motor strategies of persons with SIS using such var-
iables (muscular activation and kinematic patterns). A
second aim was to determine how subgroups of persons
with SIS who present significant or slight motor deficits
respond to the training. We think that movement training
will help reduce the movement deficits of persons with
shoulder impingement syndrome.
Methods
Participants
Thirty-three subjects with SIS, diagnosed by an orthopae-
dic surgeon, were recruited (Table 1). They were included
if they had at least one positive finding in each of the fol-
lowing categories [19]: 1) painful arc of movement during
flexion or abduction; 2) positive Neer or Kennedy-
Hawkins impingement signs; and 3) pain on resisted lat-
eral rotation, abduction or Jobe test. The exclusion criteria
were: type III acromion; calcification; shoulder instability;
previous shoulder surgery; and shoulder pain reproduced
during neck movement. A control group composed of 20
subjects with no shoulder pathology was also recruited.
All subjects provided informed consent. This study was
approved by the Ethics Committee of the Quebec Rehabil-
itation Institute.
Study design
Subjects with SIS were involved in two visits, one day
apart. The motor strategies of the upper limb were meas-
ured at each of the four evaluation phases of the study: E1)
before (baseline), E2) during, E3) immediately after, and,
E4) 24 hours after movement training with feedback. At
the first visit, prior to the measurement of the motor strat-
egies, an established self-reported questionnaire, the Dis-
abilities of the Arm, Shoulder and Hand (DASH)
questionnaire, was completed to assess upper limb pain
and functional level [23]. Thereafter, baseline motor strat-
egies were evaluated during reaching movements. This
baseline evaluation (E1) was followed by an education
period on shoulder anatomy and on specific deficits
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related to impingement using an anatomical model of the
shoulder. Then, motor strategies during reaching were re-
evaluated during (E2) and immediately after (E3) move-
ment training with feedback. The day after, subjects came
back for the second visit where motor strategies during
reaching were re-evaluated (E4). Subjects in the control
group only performed the reaching tasks once during a
visit in order to assess normal motor strategies.
Measurement of motor strategies during reaching
Reaching tasks
The tasks consisted of reaching out and pointing (with
contact) to targets located in two planes of elevation. Sub-
jects were asked to execute reaching at a natural speed, as
if they were performing activities of daily living. In each
plane, 10 trials of reaching movement were performed.
Using the Present Pain Index, pain level was evaluated
after each trial. The symptomatic arm was evaluated for
the SIS group. For the control group, the side was chosen
to have the same proportion of dominant/non-dominant
sides as evaluated in the SIS group. For the trials before,
immediately after and 24 hours after movement training,
a random sequence of trials was established. During
movement training, all trials in a plane of movement were
first carried out before performing the other movement
plane and the first plane of movement executed was bal-
anced between subjects in order to have half the subjects
starting in each plane. In a seated position, reaching tasks
started with the upper limb in a neutral position at the
side of the body and the tip of the second finger in contact
with a pressure switch. One target was located in the fron-
tal plane and positioned at a distance equivalent to the
subject's arm length and at a height equivalent to the posi-
tion of the second finger when the shoulder was at 90° of
abduction. The other target was positioned at the same
length and height as the target in the frontal plane, but
located in front of the contralateral foot, in a sagittal/
oblique plane between flexion and horizontal adduction.
Pressure switches were placed under each target to signal
the end of reaching. Motor strategies were defined by
reaching speed, upper limb kinematic patterns of relative
joint angles and electromyographic (EMG) activity of
seven muscles. Based on previous findings that have
shown only slight deficits for subjects with SIS during
reaching in the sagittal/oblique plane [19], only the fron-
tal plane data are presented here.
Kinematic
Kinematic data were recorded using the Optotrak system
(Northern Digital Inc, 103 Randall Drive, Waterloo,
Ontario, Canada N2V 1C5). Triads of infrared light-emit-
ting diodes were positioned on the hand (dorsal face),
forearm (proximal to the styloid process of the radius),
upper-arm (near the insertion of the deltoid), clavicle (lat-
eral part of the clavicle) and trunk (top of the sternum).
Data were sampled at 100 Hz and digitally low-pass fil-
tered at 8 Hz. Fourteen bony landmarks were digitized
before the acquisition of data in order to recreate the local
coordinate systems which, along with joint rotations,
were defined according to the International Society of Bio-
mechanics recommendations [24]. To compare the four
evaluation phases, two periods (auditory cue to beginning
of the movement; beginning of the movement to end of
the movement) of 100 points each were defined. Each
point represented 1% of each period. Movement ampli-
tudes were plotted for the wrist (hand relative to forearm:
flex/extension; radial/ulnar deviation), elbow (forearm
relative to arm: flex/extension), shoulder (humerus rela-
tive to trunk: plane of elevation; elevation; rotation), S/C
joints (clavicle relative to trunk: retraction/protraction;
elevation/depression) and trunk (trunk relative to global
system: flex/extension; rotation; lateral flexion). Thereaf-
ter, joint position at the end of reaching, as well as total
joint excursion (absolute value of the difference between
maximum and minimum amplitude that occurred during
reaching) were calculated. Maximal hand speed was also
calculated.
Electromyography
Bipolar surface EMG electrodes were used to record the
muscular activity of the upper, middle and lower trape-
zius, serratus anterior, infraspinatus, and anterior and
Table 1: Subjects' characteristics (Mean ± 1 standard deviation or n (%))
SIS subjects
Variables Control group (n = 20) SIS group (n = 33) SISele subgroup
(n = 17)
SISdep subgroup
(n = 10)
Age (y) 46.6 ± 9.9 47.9 ± 8.7 48.4 ± 9.6 45.2 ± 9.2
Gender: Women 13 (65.0%) 22 (66.7%) 12 (70.6%) 6 (60%)
Right hand dominance 17 (85.0%) 28 (84.8%) 15 (88.2%) 8 (80.0%)
Dominant side evaluated 12 (60.0%) 21 (63.6%) 13 (76.5%) 6 (60.0%)
Disease duration
(months)
10.8 ± 9.0 11.7 ± 10.8 9.9 ± 6.7
DASH score
(0–100)
33.3 ± 12.1 35.9 ± 12.5 27.9 ± 8.9
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middle deltoid. Following skin preparation, Ag/AgCl elec-
trodes (Kendall Medi-Trace 100, Tyco Healthcare Group,
Mansfield, MA 02048) were placed over the muscle belly,
parallel to the direction of the muscle fibres [25]. A refer-
ence electrode was placed over the contralateral
acromion. Verification of the electrode placement and
EMG signal quality was completed by visual monitoring
of EMG signals while subject performed a voluntary con-
traction [25]. Raw EMG signals were amplified for a total
gain of 4000 and transmitted by optical fibre to a mul-
tichannel Neogenix main receiver (NEO 210A, Neogenix
Technologies, 100–3175 Quatre-Bourgeois, Quebec City,
Quebec, Canada G1W 2K7). The EMG signal was band
pass-filtered at 10–500 Hz, converted from analog to dig-
ital (1000 Hz) and stored. Using specially developed soft-
ware, EMG signals were filtered with a digital high-pass
Butterworth filter at a frequency of 10 Hz to minimize the
effect of movement artefacts and full-wave rectified. EMG
activity was normalized to a reference condition and nor-
malized results were expressed as a percent of the refer-
ence condition. The reference condition, recorded before
the experiment, consisted in the mean EMG activity while
the subject maintained his arm at the target position with
a load of 1 kg in his hand for five seconds. Mean normal-
ized EMG activity was calculated for three phases: pre-
movement (beginning of muscle activation to beginning
of movement), acceleration (beginning of movement to
the end of the hand acceleration) and deceleration (begin-
ning of hand deceleration to the end of the movement).
Movement training with extrinsic feedback
Movement training was performed under the supervision
of a physiotherapist who gave feedback aimed at correct-
ing shoulder girdle movement [26]. The results of the tri-
als performed before supervised training were used to
determine the feedback given during supervised training.
Therefore, the type of feedback was established according
to individualized impairments. Three types of feedback
were given: visual, using a mirror; manual, by restricting
shoulder girdle movements or guiding scapular move-
ments; and verbal, with comments related to the motor
performance. Manual and verbal feedbacks were stand-
ardized for each type of altered shoulder kinematics [26].
In each elevation plane, a trial with feedback was followed
by a trial without feedback for a total of 10 trials in each
plane. During the trials with feedback, subjects first exe-
cuted the reaching movement with the unimpaired side in
front of a mirror. Then, still in front of a mirror, they exe-
cuted the same movement with the impaired side. During
movement, subjects received manual feedback if the kine-
matic of the shoulder was altered. Following the move-
ment with feedback, they had to evaluate their own
performance, and finally, they received verbal feedback
related to the motor aspect of the movement that had to
be improved for the next trial (example: elevation of your
shoulder girdle was too important). If the movement was
adequate, the verbal feedback confirmed that the move-
ment was properly executed. No other exercises or train-
ing were performed during this visit.
Statistical analysis
Mean value of the 10 trials during reaching in the frontal
plane was used for the statistical analysis. First, the base-
line motor strategies (total joint excursion, final joint
position and normalized EMG activity) of the SIS group
were compared the ones of the control group using inde-
pendent t-tests. Then, for the SIS group, the effect of
movement training was analysed using one-way (shoul-
der pain, reaching speed and kinematic patterns [total
joint excursion and final joint position]) and two-way
(normalized EMG activity) repeated measures ANOVA.
The factors in the model were the evaluation phase
(before [E1], during [E2], immediately after [E3] and the
day after training with feedback [E4]) and, for the normal-
ized EMG activity, the reaching phases (pre-movement,
acceleration and deceleration). Paired t-tests, with Bonfer-
roni adjustment, were used for multiple pairwise compar-
isons. Multiple pairwise comparisons were only
performed compared to the baseline trials (E1 vs. E2; E1
vs. E3; E1 vs. E4). Data of the control group were not used
for the evaluation of the effects of movement training. All
analyses were conducted with the SPSS software (Version
12; SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, Illinois
60606, USA). The alpha level was set at 0.05.
Two SIS subgroups were also defined at baseline accord-
ing to the magnitude of clavicular elevation. A previous
study has shown that this measurement can be used to
subdivide the SIS group in two subgroups with specific
reaching kinematics [19]. Subjects that increased their cla-
vicular elevation during reaching present significant
movement impairments at the trunk, clavicle, and shoul-
der, while the other subjects present slight movement
impairments. The two SIS subgroups were: SIS subjects
having clavicular elevation excursion above (SISele; n =
17) and below (SISdep; n = 10) the 95% confidence inter-
val (CI) of the clavicular elevation excursion of the control
group. Separate analyses were performed for each SIS sub-
group. There were no statistical comparisons between the
subgroups.
Results
The SIS and control groups were similar for age, weight,
height, sex and dominance. No significant differences
were noted between the two SIS subgroups for age, sex,
DASH score and duration of symptoms (Table 1).
Comparison between control and SIS groups and
subgroups at baseline
Analyses of a previous study [19] have shown that the
control group performed reaching using trunk contralat-
eral lateral flexion and ipsilateral rotation, clavicular ele-
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vation and retraction, with shoulder elevation and lateral
rotation, elbow flexion and wrist extension for the first
50% of movement followed by elbow extension and wrist
flexion. The SIS group used the same pattern; however,
they used significantly larger trunk rotation (mean differ-
ence: 2.6°) and shoulder lateral rotation (9.0°); and fin-
ished reaching with the trunk more rotated (4.7°) and
with the shoulder in a more anterior plane of elevation
(4.1°) (Figures 1 and 2). Compared to the control group,
subjects in SISele subgroup performed reaching with
greater trunk rotation (3.4°), clavicular elevation (6.3°)
and shoulder lateral rotation (11.3°) (Figure 1), as well as
less elbow flexion (13.4°). They also finished reaching
with more trunk rotation (4.5°) and clavicular elevation
(7.1°) and with the shoulder in a more anterior plane of
elevation (6.2°) (Figure 2). For their part, the SISdep
group used less clavicular elevation (3.5°) (Figure 1). Fur-
ther detail of these previous analyses can be found in Roy
et al. (2008) [19].
Effect of movement training on pain, reaching speed and
EMG activity
Compared to their own baseline level, shoulder pain dur-
ing reaching was significantly reduced in the SIS group
and SISele subgroup during (mean difference: 0.3, P =
0.02), immediately after (respectively: 0.6 & 0.5, P <
0.004) and the day after training (respectively: 0.6 & 0.5,
P < 0.004), while it remained unchanged in the SISdep
subgroup. Maximal reaching speeds were significantly
reduced during and following training in the SIS group
and in the two SIS subgroups (Figure 3). For the SIS group
and subgroups, the EMG activity of all the muscles evalu-
ated, except lower trapezius, was significantly decreased in
the pre-movement and acceleration phases during and
following training compared to baseline (5.5 to 100.6%)
(Figure 4). There were no significant differences during
the deceleration phase.
Effect of movement training on the upper limb kinematic
Compared to baseline, subjects with SIS used the same
pattern of movement during training with feedback. How-
ever, excursions of the trunk in lateral flexion (1.2°) and
rotation (1.8°), of the clavicle in protraction/retraction
(2.7°) and of the elbow (8.7°) and wrist (4.5°) in flexion/
extension were significantly decreased, while excursions
of the trunk in flexion/extension (0.6°) and of the shoul-
der in rotation (6.9°) were increased (Figures 1 and 5). In
the SISele subgroup, excursion of the trunk in lateral flex-
ion (1.7°) and rotation (1.7°) and of the clavicle in eleva-
tion/depression (2.8°) and protraction/retraction (3.3°)
were significantly decreased during training compared to
baseline, while excursion of the shoulder in rotation was
increased (6.5°) (Figures 1 and 5). In the SISdep group,
only clavicular protraction/retraction excursion (2.6°)
was significantly decreased during training (Figure 1).
During training, subjects in the SIS group and in the SISele
subgroup also had significantly less trunk rotation (5.6°
and 5.3°) and clavicle elevation (3.4° and 3.2°), with the
shoulder in a more frontal plane of elevation at the end of
reaching (3.5° and 4.3°) (Figure 2).
Immediately following training, excursions of the trunk in
lateral flexion (1.3°) and rotation (1.4°), of the clavicle in
protraction/retraction (2.3°) and of the elbow (5.3°) and
wrist (4.8°) in flexion/extension were still decreased dur-
ing reaching in the SIS group compared to baseline (Fig-
ures 1 and 5). For the subjects in the SISele subgroup,
excursion of the trunk in lateral flexion (1.7°) and rota-
tion (1.3°) and of the clavicle in elevation/depression
(2.4°) and protraction/retraction (2.5°) were also still sig-
nificantly decreased (Figure 1). Again, only clavicular pro-
traction/retraction excursion was significantly decreased
for the SISdep subgroup (2.6°) (Figure 1). The subjects in
the SIS group and in the SISele subgroup also still had sig-
nificantly less trunk rotation (2.8° and 2.7°) and clavicle
elevation (2.5° for both) at the end of reaching immedi-
ately following training (Figure 2).
The day after movement training, clavicular elevation/
depression excursion (4.0°) and clavicular elevation posi-
tion at the end of reaching (2.5°) were significantly
decreased in the SISele subgroup compared to baseline
(Figure 1 and 2). Otherwise, excursion of the trunk in lat-
eral flexion (0.9°), of the clavicle in protraction/retraction
(2.3°) and of the elbow (5.8°) and wrist (5.1°) in flexion/
extension in the SIS group (Figures 1 and 5), and excur-
sion of the clavicle in protraction/retraction (2.3°) (Figure
1) in the SISdep subgroup were still significantly
decreased compared to baseline.
Discussion
This study is the first to look at the effect of movement
training on motor strategies of persons with SIS. Super-
vised training, aimed at improving individualized move-
ment deficits, was shown to have short-term effects on the
upper limb kinematic patterns. For most subjects, these
changes were associated with a decrease of shoulder pain
during reaching.
Changes observed in the upper limb kinematics during
and following training led to some improvements. As
observed during the baseline trials, the SIS group used
more trunk rotation and finished reaching with the trunk
more rotated and the shoulder in a more anterior plane of
elevation when compared to healthy subjects. During and
immediately following training, all these impairments
observed in persons with SIS were reduced. However,
these kinematic improvements returned to the baseline
level the day after training. According to Doyon and
Benali [27], the first steps of learning are characterized by
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Mean total joint excursionFigure 1
Mean total joint excursion. Total joint excursion (mean and standard deviation) before (E1; baseline), during (E2), immedi-
ately after (E3) and the day after (E4) movement training with feedback are shown for the SIS group and subgroups (SISele; SIS-
dep). The grey band represents the 95% confidence interval (95%CI) of the control group. * Significant difference at baseline
between the group/subgroups with SIS and the control group ‡ Significant difference in the group/subgroups with SIS compared
to their baseline trials (E1).
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Mean joint position at the end of reachingFigure 2
Mean joint position at the end of reaching. Joint position at the end of reaching (mean and standard deviation) before (E1;
baseline), during (E2), immediately after (E3) and the day after (E4) movement training with feedback are shown for the SIS
group and subgroups (SISele; SISdep). The grey band represents the 95% confidence interval (95%CI) of the control group. *
Significant difference at baseline between the group/subgroups with SIS and the control group ‡ Significant difference in the
group/subgroups with SIS compared to their baseline trials (E1).
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improvement in performance occurring within a single
session. Still, the skills are not consolidated and multiple
training sessions are needed before their consolidation.
Present results support this view with short-term positive
changes, but minimal retention 24 hours after. One ses-
sion, therefore, was not enough to bring permanent
changes in motor strategies.
For some joints, movement training led to decreased
excursions which increased baseline differences with the
control group. These changes could be seen as unfavoura-
ble. However, it has been shown that early in motor learn-
ing, when persons have to choose how to efficiently
manage the various degrees of freedom, control is simpli-
fied through the freezing of some degrees of freedom [28].
Such a strategy could be temporarily adopted to facilitate
performance by allowing the opportunity to control a few
necessary degrees of freedom [28]. As seen in the results
(see Figure 5), persons with SIS mostly restricted the
movements of the more distal joints with training. By
restricting the excursion of the elbow and wrist joints, they
could put more emphasis on providing the proper strategy
at the shoulder joint to avoid impingement. This adapta-
tion could be seen as an early step in motor learning [28].
EMG activity was decreased during and following train-
ing. The baseline differences with the control group were
increased for most of the muscles and the standard devia-
tions were larger than the ones of the control group. Pre-
viously, it has been shown that the standard deviation is
similar between persons with and without SIS [19].
Present findings show that the variability in the muscular
performance of the persons with SIS was more important
during and following training. According to the learning
phases of Fitts & Posner [12], the subjects were involved
in the first phase of learning, the cognitive stage. They had
to solve the problem first and find out what had to be
done to improve shoulder control. This phase required
considerable cognitive activity in order to determine the
appropriate strategies. Therefore, performances were
inconsistent, leading to large within and between subject
variability. Such cognitive activities most likely also led to
the reduction of reaching speed observed during and fol-
lowing training. This reduction of speed makes it difficult
to compare the EMG activity with baseline since lower
speed is associated with lower EMG activity [19].
The training session was designed to optimize motor
learning. Studies have looked at different ways to enhance
training by looking at the best motor learning strategies
[9-11,29]. One conclusion of these studies is that subjects
have to be actively involved in solving the motor problem
during training [9]. The training session was planned
around that principle. As a result, to improve the intrinsic
error-detection capabilities of the subjects [9]: a) pre-
training education with an anatomical model of the
shoulder was given [11], and, b) a mirror was used to
observe the kinematics of the unimpaired and impaired
shoulders in order to give a visual comparison to the sub-
ject of the movements that had to be improved. Moreover,
to allow active engagement in information processing
activities [9,11,29]: a) external feedbacks was given in
only half of the trials, and b) subjects had to judge their
own performance before the verbal feedback from the
physiotherapist. Furthermore, it has been shown that the
learning effects are greater when feedback is not given on
each trial and when the subjects have to evaluate their per-
formance first [30].
The separate analyses of the two SIS subgroups proved
that not all persons with SIS respond the same way to
training. Subjects in the SISele subgroup were the ones
who seem to have benefited the most from training. With
training, they significantly changed their trunk, clavicle
and shoulder kinematics leading to a reduction of the
baseline differences with the control group. Furthermore,
shoulder pain during reaching was significantly reduced.
This suggests that, for persons with significant kinematic
deficits, rehabilitation of their motor control deficits is an
important step for improving their shoulder pain. Indeed,
the reduced clavicular elevation could be a sign that they
are able to reach without superiorly migrating their
humeral head. Thus, these persons most likely reduced
the impingement of the subacromial structures leading to
the observed decrease of pain. Moreover, by reducing their
trunk movement and by moving more into the frontal
plane, they demonstrated that they do not prevent their
Maximal hand speed (in m/s) during reachingFigure 3
Maximal hand speed (in m/s) during reaching. The
maximal hand reaching speed (mean and standard deviation)
observed before (baseline), during, immediately after and the
day after training with feedback is shown. The grey band rep-
resents the 95% confidence interval (95%CI) of the control
group. * Significant difference in the group/subgroups with
SIS compared to their baseline trials (E1).
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Mean difference with baseline EMG activityFigure 4
Mean difference with baseline EMG activity. The differences (mean and standard deviation) between the EMG activity at
baseline and during, immediately after and the day after movement training are shown (0 = no difference with the baseline
value) for the SIS group. The differences (mean and standard deviation) at baseline between the EMG activity of the control
group and of the SIS group are also plotted (grey band). * Significant difference in the group with SIS compared to their baseline
trials.
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shoulder from moving in a plane where the subacromial
space is minimal [22].
In the SISdep subgroup, only clavicular pro/retraction was
changed with training, increasing baseline differences
with the control group. Furthermore, pain level remained
unchanged. It could be argued that training was more rel-
evant for the SISele group. Training was design to correct
the specific movement deficits observed in patients with
SIS and persons with SIS who use greater clavicular eleva-
tion during reaching present the most altered kinematic
patterns. Thus, persons presenting mild kinematic deficits
may benefit better of other types of rehabilitation, such as
strengthening or stretching exercises. However, the small
number of subjects in the SISdep subgroup could have
contributed to the lack of differences.
Some limitations of this investigation are worthy of note.
Only the short-term effect of movement training with
feedback was evaluated in this study. Further researches
will have to look at its long-term effects. Scapular move-
ment was not evaluated. However, no valid and reliable
method was available in our laboratory to characterize
scapular dynamic changes. Training with feedback is only
one aspect of the rehabilitation program. Evaluation of
physical factors, such as muscle strength, endurance and
range of motion that could interfere with the ability of
persons with SIS to perform arm movement also need to
be addressed. Furthermore, it is still unknown, as in other
musculoskeletal conditions [31], if the motor control def-
icits precede or follow the onset of pain and through
which cortical or subcortical mechanisms these deficits
take place. Only future neurophysiologically based stud-
ies will help to better understand the neural mechanisms
underlying motor control deficits observed in persons
with SIS.
Conclusion
Movement training with feedback led to short-term
changes during arm movements with respect to shoulder
pain and upper limb kinematic patterns. Persons with SIS
who presented the greater kinematic deficits at baseline
were the ones who demonstrated the most significant
changes in pain and kinematics following movement
training. Thus, rehabilitation strategies should be based
on initial kinematic deficits. Our results support the need
to evaluate this approach during a long-term training pro-
gram.
Abbreviations
ANOVA: Analysis of variance; DASH: Disabilities of the
arm, shoulder, and hand; E1: Baseline evaluation; E2:
Evaluation during movement training; E3: Evaluation
immediately after movement training; E4: Evaluation 24
hours after movement training; SIS: Shoulder impinge-
ment syndrome; EMG: Electromyographic
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
JSR: participated in the design of the study, carried out the
acquisition, the analysis and the interpretation of data
and drafted the manuscript.
HM: participated in the design of the study, the analysis
and the interpretation of data and drafted the manuscript.
BJM: participated in the design of the study, carried out
the acquisition, the interpretation of data and drafted the
manuscript.
RL: participated in the development of the study question,
enrolled subjects, and participated in the revision of the
manuscript.
All authors read and approved the final manuscript.
Acknowledgements
The authors wish to thank Guy St. Vincent for his help in the development
of the experimental procedure and in the acquisition of data. This study was
supported by a grant from the Ordre de la physiothérapie du Québec. The
funding source was not involved in the study's design, conduct and report-
ing. JSR was supported by scholarships from the Institut de recherche en
Interjoint coordination between elbow and wrist flexion/extensionFigure 5
Interjoint coordination between elbow and wrist flex-
ion/extension. The interjoint coordination between elbow
and wrist flexion/extension observed before (baseline), dur-
ing, immediately after and the day after movement training
are shown for the SIS group. * Significant difference in the
group with SIS compared to elbow and wrist excursions at
baseline.
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