Weon et al: Visual feedback for scapular winging
Real-time visual feedback can be used to activate scapular
upward rotators in people with scapular winging: an
experimental study
Jong-Hyuck Weon1,2, Oh-Yun Kwon2, Heon-Seock Cynn2, Won-Hwee Lee2, Tae-Ho Kim3 and
Chung-Hwi Yi2
1
Wonju Christian Hospital, 2Yonsei University, 3Daegu Health College
Republic of Korea
Question: Can real-time visual feedback facilitate the activity of serratus anterior in individuals with scapular winging during
shoulder flexion? Design: Comparative, repeated-measures experimental study. Participants: Nineteen subjects with
scapular winging. Intervention: Participants performed isometric shoulder flexion at 60° and 90° with and without real-time
visual feedback using a video camera to monitor scapular winging. Outcome measures: Activity in the upper trapezius, lower
trapezius, and serratus anterior muscles was measured using surface electromyography. A video motion analysis system
measured the displacement of a marker attached to the acromion in the frontal and sagittal planes. Results: Visual feedback
significantly increased activity in the upper trapezius at 60° of shoulder flexion by 2.3% of maximum voluntary isometric
contraction (95% CI 0.7 to 4.0). Visual feedback also significantly increased activity in the serratus anterior at 60° and 90°
of shoulder flexion, by 3.0% (95% CI 2.3 to 3.6) and 5.9% (95% CI 3.3 to 8.5) of maximum voluntary isometric contraction
respectively. These effects equated to effect sizes from 0.29 to 0.46. Visual feedback also significantly improved movement
of the acromion superiorly at 60° of shoulder flexion and anteriorly at 60° and 90° of shoulder flexion. Conclusion: Real-time
visual feedback can be used to activate the upper trapezius and serratus anterior muscles and to improve movement of the
scapula during shoulder flexion in people with scapular winging. [Weon J-H, Kwon O-Y, Cynn H-S, Lee W-H, Kim T-H, Yi C-H
(2011) Real-time visual feedback can be used to activate scapular upward rotators in people with scapular winging:
an experimental study. Journal of Physiotherapy 57: 101–107]
Key words: Electromyography, Scapular winging, Serratus anterior, Visual feedback
Introduction
Shoulder pain is a common problem. The incidence is
11.6 per 1000 person-years in Dutch general practice
(Bot et al 2005), with reports of the prevalence in various
populations ranging from 7% to 67% (Adebajo and
Hazleman 1992, Cunningham and Kelsey 1984, Meyers
et al 1982, Reyes Llerena et al 2000). Abnormal scapular
position and movement are associated with shoulder pain
and glenohumeral joint impingement syndrome (Cools et
al 2003, Kibler 1998). Scapular dysfunction may arise from
musculoskeletal factors – including sustained abnormal
posture (Rempel et al 2007), repetitive movements that
deviate from normal movement patterns (Madeleine et
al 2008), or glenohumeral and scapulothoracic muscle
imbalance (Cools et al 2004, Hallstrom and Karrholm
2006) – or from neurological abnormalities. Co-ordinated
activation of the scapular upward rotators is essential for
normal scapulohumeral rhythm.
Scapular winging is a specific type of scapular dysfunction
that has two common causes. One is the denervation of the
long thoracic nerve leading to difficulty flexing the shoulder
actively above 120º. The second cause is weakness of the
serratus anterior muscle. Serratus anterior is one of the
prime muscles used to rotate the scapula upward (Dvir and
Berme 1978), and weakness of serratus anterior is a major
cause of shoulder pain, glenohumeral joint impingement,
and winging of the scapula (Ludewig and Cook 2000,
Lukasiewicz et al 1999). In particular, over-activation of the
upper trapezius and reduced activity in the lower trapezius
and serratus anterior muscles during shoulder flexion may
contribute to abnormal scapulohumeral rhythm and scapular
winging (Cools et al 2004, Cools et al 2007, Ludewig and
Cook 2000). Kendall and colleagues (1993) and Sahrmann
(2002) also emphasise weakness of serratus anterior as an
etiological factor for aberrant scapular mechanics.
Several pushup and wall sliding exercises have been
developed for rehabilitation and in the sports field to
activate serratus anterior (Hardwick et al 2006, Ludewig
et al 2004). However, because the scapula is located behind
the rib cage, it is not possible for the patient to monitor
scapular movement visually during these exercises. Thus,
for effective training of serratus anterior, the exercise must
be supervised to ensure that the load applied to the upper
limb is appropriate and does not cause scapular winging.
To our knowledge, none of the studies that have investigated
exercises to strengthen serratus anterior in people with
scapular winging have used real-time visual feedback
with a video camera to monitor scapular movement during
shoulder flexion exercise. We hypothesised that real-time
visual feedback would enable neurologically intact people
with scapular winging to activate the scapular upward
rotators, particularly the serratus anterior muscle, during
Journal of Physiotherapy 2011 Vol. 57 – © Australian Physiotherapy Association 2011
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Research
shoulder flexion. Therefore the specific research question
for this study was:
Can real-time visual feedback using a video camera
facilitate activation of serratus anterior in people with
scapular winging during shoulder flexion?
Method
Design
A within-participant, repeated measures experimental
study of shoulder muscle activation and scapular alignment
was carried out in people with scapular winging as they
performed isometric shoulder flexion with and without
visual feedback. Electrodes for electromyography were
applied over serratus anterior and upper and lower trapezius.
Scapular winging was measured with a scapulometer.
Initially, scapular winging was measured in a neutral
shoulder position. Participants then flexed their shoulder
isometrically at 60º and 90º, during which muscle activity
and scapular winging were measured.
Participants
Participants were recruited from the Department of Physical
Therapy, Yonsei University, Korea. A physical examination
was carried out to determine subject eligibility. Adults were
eligible to participate in the study if they had weakness
of serratus anterior and scapular winging. Weakness of
serratus anterior was confirmed by a grade of ‘fair minus’
or lower on manual muscle testing (Hislop and Montgomery
1995). Scapular winging was confirmed by a distance of
at least 2 cm between the thoracic wall and the inferior
angle of the scapula, measured using a scapulometer –
described in detail below. The exclusion criteria were
past or present musculoskeletal conditions affecting the
cervical or thoracic spine, glenohumeral joint, rotator cuff
muscles, or acromioclavicular joints, as well as neurological
and cardiopulmonary disorders that could interfere with
shoulder flexion.
The scapulometer was modified from the Perry Tool,
developed by Plafcan and colleagues (1997). The Perry
Tool measures the angle between the transverse plane and
a line joining the spinous process and the inferior angle
of the scapula. This angle increases as scapular winging
increases. However, the angle is also influenced by the
amount of scapular abduction, so it does not provide a valid
measure of scapular winging. Therefore we developed the
scapulometer to measure the posterior displacement of the
inferior angle of the scapula from the posterior thoracic
wall directly.
Figure 1. Scapulometer used to measure scapular
winging. A, Stationary board. B, Guide board. C, Sliding
board. D, Pad. E, Body. F, Ruler. G, Grip handle.
the scapula, with the sliding board at the level of the inferior
angle of the scapula. Holding the scapulometer in place with
one hand, the examiner moves the sliding board anteriorly
until it touches the inferior angle of the scapula. A ruler on
the fixed board measures the posterior displacement of the
inferior angle of the scapula from the thoracic wall (Figure
2).
Several methods could be used to elicit scapular winging
for measurement, such as applying a load to the patient’s
flexed shoulder. Even if the amount of shoulder flexion
was fixed, however, the position of the inferior angle of the
scapula would vary according to the strength of the upward
rotators of the scapula and the scapulohumeral movement
pattern. A further problem with this method in the present
study would be the inability of the participants to maintain
a stable position of shoulder flexion, due to weakness of
serratus anterior. We therefore positioned participants in
standing with the shoulder in the neutral position, the elbow
flexed at 90º, and the forearm in neutral rotation. A cuff
weighing 5% of the patient’s body weight was placed on the
wrist (Figure 3). In this position, a wrist weight provides a
load in a direction that tends to induce scapular winging,
tilting, and depression. Participants were advised to keep
their hand relaxed in a loose fist because hand activity
increases shoulder girdle muscle activity (Sporrong et al
1998).
Before the study commenced, the test-retest reliability of
this method of measuring scapular winging was examined
The body of the scapulometer is a vertical board 20 cm high
with an upper width of 14 cm and a lower width of 11 cm,
and a thickness of 1.8 cm. Circular pads (2 cm in diameter
and 2 cm high) near each corner of the scapulometer allow it
to be applied comfortably to the posterior wall of the thorax.
A handle on the opposite surface of the scapulometer allows
it to be held in place easily. Extending posteriorly from the
superior edge of the scapulometer body is a fixed board,
mounted with two parallel guides, which allow a horizontal
sliding board to move anteroposteriorly between them
(Figure 1).
To measure scapular winging, the examiner stands behind
the patient and places the four pads of the scapulometer on
the posterior thoracic wall medial to the vertebral border of
102
Figure 2. Superior view of the measurement of scapular
winging.
Journal of Physiotherapy 2011 Vol. 57 – © Australian Physiotherapy Association 2011
Weon et al: Visual feedback for scapular winging
Figure 4. The marker measuring acromion displacement
is illustrated during the 90° shoulder flexion in the visual
feedback condition. This view illustrates assessment of
movement of the marker superiorly or inferiorly in the
frontal plane. A, Starting position. B, Shoulder flexion
position.
Measurement
Figure 3. Lateral view of the measurement of
scapular winging.
in 10 people over five days. The interclass correlation
coefficient (ICC 2,1) was 0.97 (95% CI 0.87 to 0.99). The
standard error of the measurement was 0.1 cm.
Intervention
Each participant was seated on a chair with the cervical
spine in a neutral position. Participants were asked to flex
the affected shoulder to two angles (60º and 90º), either with
or without real-time visual feedback. The order of the two
angles and the two feedback conditions were randomised by
drawing a sealed envelope from a box.
Participants were instructed to lift the upper limb being
tested slowly with the elbow extended, the forearm and
wrist in a neutral position, and a loose fist, and to hold
the position for 5 sec at the flexion angle of 60º or 90º. A
universal goniometer was used to determine the flexion
angle, and a horizontal target bar was positioned at each
angle in the sagittal plane. The shoulder level and scapular
movement in the lateral and posterior view were recorded
on two video cameras connected to a personal computer.
The computer screen was positioned at the participant’s eye
level and turned on when real-time visual feedback was
required.
Before the shoulder flexion, the principal investigator
placed the scapula in the normal position (vertebral border
parallel with spine spacing at approximately 7 cm, scapula
positioned between T2 and T7 and flat on the posterior rib
cage). The subject was asked to observe the scapular motion
through the computer monitor (Figure 4). If shoulder
depression, tilting, or winging were observed during
shoulder flexion, the investigator encouraged the subject
to protract and elevate the scapula. Participants practised
using the visual feedback to maintain the scapula in a
normal position for 15 min. The shoulder flexion task was
performed three times. A 3-min rest period was allowed
between trials to minimise fatigue.
The primary measure in the study was muscle activity in
the scapular upward rotators. Surface electromyographic
data were collected from the upper and lower trapezius
and serratus anterior, using a standard data acquisition
systema. Preparation of the electrode sites involved shaving
and cleaning the skin with rubbing alcohol (Cram et al
1998). Disposable silver/silver chloride surface electrodesb
were positioned at an inter-electrode distance of 2 cm. The
reference electrode was attached to the styloid process of
the ulna of the upper limb being tested. Electromyographic
data were collected for the upper trapezius muscle
(using electrodes placed 2 cm lateral to the midpoint
of a line drawn between the C7 spinous process and the
posterolateral acromion), lower trapezius muscle (placed on
an oblique vertical angle with one electrode superior and
one inferior to a point 5 cm inferomedial from the root of
the spine of the scapula), and the serratus anterior muscle
(placed vertically along the midaxillary line at rib levels
6–8) (Cram et al 1998, Nieminen et al 1993). Each pair of
electrodes was aligned parallel to the line of underlying
muscle fibres. Electromyographic data were sampled at
1000 Hz. The signals were amplified and digitisedc. A bandpass filter (20–450 Hz) was used. The root mean square was
calculated from the raw data using a moving window of 50
msec and was converted to ASCII files for analysis.
For normalisation, 5 sec of reference contraction data were
recorded while the participant performed three trials of
maximal voluntary isometric contraction in the manual
muscle testing position for each muscle (Kendall et al 1993).
To ensure maximal effort, verbal encouragement was given.
To minimise compensation during data collection, subjects
were encouraged to maintain the testing position (Boettcher
et al 2008). The middle 3 sec of the 5-sec contraction were
used for data analysis. The initial 1 sec was excluded to
ensure maximal amplitude had been reached, and the final
1 sec was discarded to avoid possible fatigue from sustained
maximal muscle contraction (Soderberg and Knutson 2000,
Dankaerts et al 2004, Tucker et al 2010). A 3-min rest
period was provided between trials. The mean root mean
square of the three trials was calculated for each muscle.
The electromyographic signals collected during each
angle of shoulder flexion were expressed as a percentage
of the calculated root mean square of maximal voluntary
isometric contraction.
Journal of Physiotherapy 2011 Vol. 57 – © Australian Physiotherapy Association 2011
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The secondary measure in the study was displacement of
the acromion in the frontal and sagittal planes. A reflective
marker 14 mm in diameter was placed on the skin at the
midpoint of the acromion to measure its displacement in the
frontal and sagittal planes during shoulder flexion (Figure
4). The reflective markerd was not used for visual feedback,
but was used for measuring the displacement of acromion.
Two video cameras were placed 1.5 m from the shoulder
joint; one was located behind the subject to capture the
superior and inferior displacement of the marker in the
frontal plane, and the other was placed to the side of the
subject to capture the anterior and posterior displacement
of the marker in the sagittal plane. Two 30-cm-long wooden
rods attached to the side and back of a wooden chair were
used as reference points to calibrate the motion analysis
systeme in the frontal and sagittal planes (Figure 5). Video
files captured during the shoulder flexion test were used to
calculate the displacement of the marker. The distance of
the acromion movement was measured from the starting
position to the end of the predetermined shoulder flexion
position in cm by the video motion analysis system software
(Figure 5).
Data analysis
For each combination of flexion angle and feedback
condition, the average of the three trials was calculated
for the data analysis. A two-factor repeated-measures
analysis of variance was used to determine differences in
muscle activity and acromion displacement during shoulder
flexion (60º and 90º) between the real-time visual-feedback
and no-visual-feedback conditions. A p value ≤ 0.05 was
deemed to be statistically significant. A paired t-test with
Bonferroni correction was used (with p = 0.05/6 = 0.0083)
for the pair-wise comparison in muscle activity and marker
displacement in the frontal and sagittal planes for the two
feedback conditions.
Table 1. Characteristics of the study participants
Characteristic
n = 19
Age (years), mean (SD)
24 (2)
Height (cm), mean (SD)
169 (6)
Weight (kg), mean (SD)
61 (7)
Gender, n male (%)
10 (53)
Side of winging, n right (%)
14 (74)
Results
Flow of participants through the study
Nineteen participants were recruited from the Department
of Physical Therapy, Yonsei University, Korea. The
characteristics of the participants are presented in Table
1. All participants completed all aspects of the testing
procedure according to the random allocation of testing
conditions.
Muscle activity
For the upper trapezius muscle, the main effects were
significant for shoulder flexion angle (p < 0.001) and
feedback (p = 0.017), as was the interaction effect (p =
0.003). Visual feedback increased activation of the upper
trapezius at both 60º and 90º of shoulder flexion (Table 2).
After Bonferroni correction, however, the effect of visual
feedback was significant only at the 60º shoulder flexion
angle (p = 0.008).
For the lower trapezius muscle, the main effect for shoulder
flexion angle was significant (p = 0.001), but neither the
main effect for the visual-feedback condition (p = 0.152)
nor the interaction effect (p = 0.150) was significant. The
data are presented in Table 2.
Figure 5. Real-time visual feedback using video camera input to the computer monitor.
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Journal of Physiotherapy 2011 Vol. 57 – © Australian Physiotherapy Association 2011
Weon et al: Visual feedback for scapular winging
Table 2. Mean (SD) muscle activation as a percentage of the maximum voluntary isometric contraction at 60° and 90°
shoulder flexion with and without visual feedback, and mean (95% CI) difference between feedback conditions (n = 19).
Muscle
Shoulder
flexion
angle
Upper trapezius
Lower trapezius
Serratus anterior
Muscle activation (%MVIC)
Feedback
p value
Effect
size
Difference
Visual
None
Visual minus None
60°
7.9 (5.4)
5.6 (2.3)
2.3 (0.7 to 4.0)
0.008
0.57
90°
8.8 (4.7)
7.5 (2.4)
1.3 (0.0 to 2.5)
0.049
0.34
60°
15.0 (11.4)
14.5 (8.4)
0.4 (–1.7 to 2.6)
0.679
0.04
90°
21.0 (18.8)
24.0 (14.8)
–3.0 (–6.8 to 0.7)
0.104
0.18
60°
18.0 (10.4)
15.1 (10.1)
3.0 (2.3 to 3.6)
0.000
0.29
90°
31.6 (12.6)
25.7 (13.6)
5.9 (3.3 to 8.5)
0.000
0.46
%MVIC = percentage of maximal voluntary isometric contraction
Table 3. Mean (SD) displacement (cm) of the acromion at 60° and 90° shoulder flexion with and without visual feedback, and
mean (95% CI) difference between feedback conditions (n = 19).
Direction
Shoulder
flexion
angle
Displacement (cm)
Feedback
Visual
Superior
Anterior
p value
Difference
None
Effect
size
Visual minus None
60°
3.6 (1.0)
1.5 (0.7)
2.1 (1.4 to 2.7)
0.000
2.45
90°
3.6 (0.5)
3.0 (0.9)
0.6 (0.1 to 1.2)
0.024
0.94
60°
2.5 (1.3)
–0.2 (0.7)
2.7 (1.9 to 3.5)
0.000
2.64
90°
2.4 (1.6)
–0.6 (0.9)
3.1 (2.1 to 4.0)
0.000
2.47
For the serratus anterior muscle, the main effects were
significant for shoulder flexion angle (p < 0.001) and
feedback (p < 0.001), as was the interaction effect (p =
0.045). Visual feedback significantly increased activation
of serratus anterior at both 60º and 90º of shoulder flexion
(Table 2). After Bonferroni correction, the effect of visual
feedback remained significant at both 60º and 90º of
shoulder flexion (p < 0.001).
Scapular movement
Measurement of displacement of the acromial marker in
the frontal plane showed that the average movement was
superior for all combinations of flexion angle and feedback.
The main effects were significant for shoulder flexion angle
(p < 0.001) and feedback (p < 0.001), as was the interaction
effect (p = 0.001). Visual feedback significantly increased
the superior displacement of the acromion (Table 3). After
Bonferroni correction, the effect of feedback remained
significant only at 60º of shoulder flexion (p < 0.001).
Measurement of displacement of the acromial marker in
the sagittal plane showed that the average movement was
anterior with feedback and posterior without feedback. The
main effect was significant for the visual feedback (p =
0.000), but neither the main effect for shoulder flexion angle
(p = 0.100) nor the interaction (p = 0.268) was significant.
After Bonferroni correction, the effect of visual feedback
on anterior movement of the acromion during shoulder
flexion remained significant at both 60º and 90º of shoulder
flexion (p < 0.001).
Discussion
This study found that muscle activity in all scapular upward
rotators increased significantly as the shoulder flexion angle
increased and that upper trapezius and serratus anterior
muscle activity increased significantly with real-time visual
feedback.
The increase in the activity of the upward rotators of the
scapula between 60º and 90º of shoulder flexion is similar
to the gradual increase in activity of the upper trapezius and
serratus anterior muscles during arm abduction (Bagg and
Forrest 1986). In that study, the lower trapezius remained
relatively inactive until the arm was abducted 90º. The
lower trapezius increased its activity – and therefore its
contribution to the upward rotation force couple – as the
arm was elevated beyond 90º. With increasing abduction,
the instantaneous centre of rotation of the scapula moved
toward the acromioclavicular joint from the root of the
spine of the scapula, lengthening the moment arm of
the lower trapezius muscle (Bagg and Forrest 1988).
Similarly, in the current study of flexion, the moment arm
of the lower trapezius lengthens as the amount of shoulder
flexion increases. This is likely to be responsible the
significant increase in activity of the lower trapezius at 90º
flexion (especially maintaining the isometric contraction)
Journal of Physiotherapy 2011 Vol. 57 – © Australian Physiotherapy Association 2011
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compared to at 60º flexion. This finding is consistent with
the results of other studies investigating muscle activity in
the scapular upward rotator muscles during arm elevation
(Antony and Keir 2010, Ebaugh et al 2005, Jarvholm et al
1991, Mathiassen and Winkel 1990).
Muscle activity in the upper trapezius increased significantly
when the participants maintained 60º of shoulder flexion
while simultaneously reducing scapular winging using
real-time visual feedback. Sahrmann (2002) stated that
an increase in upper trapezius activation is needed to
compensate for the weakened serratus anterior muscle.
Thus the upper trapezius may be supporting the increased
activity in the serratus anterior, which was significantly
greater at both the 60º and 90º angles when visual feedback
was provided. The marker displacement in the frontal plane
indicated that scapular elevation increased significantly at
the 60º shoulder flexion angle when visual feedback was
provided. This may also be the result of the activity of the
upper trapezius at the 60º angle. Anterior movement of the
acromion in the sagittal plane was significantly greater at
both shoulder flexion angles when visual feedback was
provided, which is consistent with the increased activity
of serratus anterior. These findings indicate that visual
feedback helped the participants activate appropriate
musculature during shoulder flexion to control scapular
winging.
A number of exercises to strengthen serratus anterior have
been described in the literature (Decker et al 1999, Ekstrom
et al 2003, Hardwick et al 2006, Ludewig et al 2004). These
exercises should be performed with scapular protraction
to activate the serratus anterior muscle while stabilising
the thoracic wall, and they should be carried out with no
scapular winging. Sahrmann (2002) suggested that the level
of resistance be modified for weakened scapular upward
rotators. However, no effective means of self-monitoring
and correcting scapular winging during shoulder flexion
exercise has been available. Real-time visual feedback using
a video provides an immediate and continuous feedback for
correcting scapular movement during independent shoulder
flexion exercise. Therefore this system of visual feedback
is a useful way to facilitate serratus anterior activity during
shoulder flexion in people with winging of the scapula.
The activity of the lower trapezius was not significantly
increased when visual feedback was provided. This finding
may be related to the verbal instructions given to the
participants. Participants were instructed to protract and
elevate the affected scapula. Thus the verbal instructions
may have reinforced the actions of both the serratus anterior
and the upper trapezius more than the action of the lower
trapezius.
The scapulometer showed high test-retest reliability for
the measurement of scapular winging in this study. The
scapulometer may be utilised in future research as a
screening tool for scapular winging. The threshold of 2 cm
was used to define scapular winging in this study because
this is the minimum amount of winging of the inferior angle
of the scapula we had observed in people with ‘fair minus’
or lower grade of muscle strength of the serratus anterior
on manual muscle testing. However, no previous studies
have provided normative data for winging or suggested a
relationship between the degree of winging and the strength
of the serratus anterior muscle. Thus, future studies are
106
warranted to confirm our findings on an objective and
reliable grading system and to further investigate the
correlation between scapular winging and serratus anterior
muscle strength.
The present study had several limitations. First, this was
a cross-sectional study, so it could only assess immediate
effects. A longitudinal study is warranted to determine the
long-term effect of training with visual feedback by people
with scapular winging. Also, kinematic data of scapular
upward rotation were not collected in this study. Finally, we
measured scapular upward rotator muscle activity during
isometric shoulder flexion, so the findings of this study
cannot necessarily be generalised to concentric or eccentric
control of shoulder flexion.
Our findings demonstrate that muscle activity increased in
the upper trapezius, lower trapezius, and serratus anterior
as the shoulder flexion angle increased under the visualfeedback condition and that the activity in the upper
trapezius and serratus anterior muscles was significantly
greater than that measured during the no-visual-feedback
condition. Thus, visual feedback during shoulder flexion
can be recommended to increase activation of the upper
trapezius and serratus anterior muscles. n
Footnotes: aBiopac MP100WSW System, Biopac Systems
Inc, Goleta, CA, USA. bDelsys Inc, Boston, MA, USA.
c
AcqKnowledge 3.7.2 software, Biopac Systems Inc,
Goleta, CA, USA. dOxford Metrics, Inc. Oxford, UK.
e
Twinner Pro, SIMI Motion 5.0 Reality Motion Systems,
Unterschleissheim, Germany.
Ethics: The Yonsei University institutional review board
approved this study. All participants gave written informed
consent before data collection began.
Competing interests: None declared.
Correspondence: Oh-Yun Kwon, Department of
Rehabilitation Therapy, Yonsei University, Republic of
Korea. Email: [email protected]
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