Journal of Athletic Training
2019;54(11):1156–1164
doi: 10.4085/1062-6050-237-18
Ó by the National Athletic Trainers’ Association, Inc
www.natajournals.org
Shoulder
Serratus Anterior and Upper Trapezius
Electromyographic Analysis of the Push-Up Plus
Exercise: A Systematic Review and Meta-Analysis
Fu-Jie Kang, MS*; Hsiang-Ling Ou, MS†; Kun-Ying Lin, PT, BS‡;
Jiu-Jenq Lin, PhD*§
*School & Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei; †Taipei Medical
University Hospital, Taiwan; ‡Department of Rehabilitation, Kaohsiung Veterans General Hospital, Kaohsiung City, Ziguan
District, Taiwan; §Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei
Context: Whereas the serratus anterior (SA) and the upper
trapezius (UT) work as a force couple for scapular motion,
weakness of the SA and overactivation of the UT are often
present in overhead athletes with shoulder dysfunction. Therefore, researchers addressing an intramuscular imbalance
between the SA and UT have focused on finding exercises that
target the weak SA and minimally activate the UT.
Objective: To compare the effectiveness of push-up plus
(PUP) exercise variants based on the electromyographic (EMG)
activity of the SA and UT.
Data Sources: A systematic search of PubMed and Scopus
between January 1, 2000, and March 31, 2008.
Study Selection: Studies of PUP exercises that involved
EMG analysis.
Data Extraction: We assessed study quality using the
Critical Appraisal Skills Program. For the systematic analysis,
the following data were extracted: (1) author, year, and study
design; (2) participant characteristics; (3) type of PUP intervention; (4) EMG outcome measures; and (5) main results. For the
meta-analysis, the EMG data of the SA and UT were calculated
using the mean difference of EMG activity with a 95%
confidence interval.
Data Synthesis: Based on 19 studies with 356 participants,
different hand positions (the distance between the hands,
shoulder-flexion angle, and elbow-flexion angle) and different
lower extremity positions variably affected the activation of the
SA and UT during the PUP exercise. Also, when participants
performed the PUP on an unstable surface compared with a
stable surface, UT activity increased 2.74% (95% confidence
interval ¼ 0.07%, 5.41%).
Conclusions: The standard PUP exercise elicited high
EMG activity of the SA. Participants generated higher SA and
lower UT EMG activity when they performed the PUP exercise
on a stable surface in full elbow extension, with the hands
placed shoulder-width apart, shoulder-flexion angles of 1108 or
1208, and the ipsilateral lower extremity lifted.
Key Words: healthy participants, stable and unstable
surfaces, scapular motion
Key Points
The serratus anterior (SA) and upper trapezius (UT) work as a force couple for scapular motion. Weakness of the SA
and overactivation of the UT are frequently present in overhead athletes with shoulder dysfunction.
The push-up plus (PUP) exercise is often prescribed to strengthen the SA.
Participants generated higher SA and lower UT electromyographic activity when performing the PUP exercise on a
stable surface in full elbow extension, with the hands shoulder-width apart, in 1108 to 1208 of shoulder flexion, and
with the ipsilateral lower extremity lifted.
Compared with a stable surface, performing the PUP exercise on an unstable surface induced higher levels of UT
activation but not SA activation.
During the PUP exercise, serratus anterior activity did not differ between the stable and unstable surfaces.
T
he transfer of kinetic energy through the shoulder at
rapid speeds with large ranges of motion and high
precision is evident in the increased prevalence of
shoulder injuries among overhead athletes.1,2 Scapular
dyskinesis, defined as altered position and motion of the
scapula, has been associated with shoulder impingement
syndrome, rotator cuff tendinopathy, and multidirectional
impairments.1,3,4 Reviewing 5 studies of 419 athletes,
Hickey et al4 indicated that scapular dyskinesis increased
the risk of future shoulder pain by 43% in asymptomatic
1156
Volume 54 Number 11 November 2019
athletes. Therefore, to regain a stable base for the optimal
throwing motion, scapular-muscle training is an important
part of injury prevention in and rehabilitation of overhead
athletes.5–7
The serratus anterior (SA) and trapezius play important
roles in moving and stabilizing the scapula during upper
extremity motion.8,9 Whereas the SA protracts and
upwardly rotates the scapula as the mover, it also stabilizes
the middle border and inferior angle of the scapula to
prevent winging and anterior tilt during upper extremity
movements.10 Serratus anterior weakness is often present in
overhead athletes and can result in shoulder dysfunction
due to altered scapular kinematics, such as winging and
tipping.8,11 Researchers11 who addressed an intramuscular
imbalance between the SA and upper trapezius (UT)
focused on finding exercises to target the weak SA and
minimally activate the UT. The lower activation level of
the SA with compensation via hyperactivity of the UT
during upper extremity motion could result in a shouldershrugging motion with excessive superior translation, less
efficient upward rotation, and posterior tipping of the
scapula, which can lead to shoulder impingement.8,11
Practically, the push-up plus (PUP) exercise is often
prescribed for strengthening the SA.8,12–14 During the PUP
exercise, full scapular protraction (the plus) is added after
full elbow extension at the end of the usual exercise.8 The
plus phase during the PUP exercise elicits the highest
average SA electromyographic (EMG) activity compared
with other SA-activating and closed kinetic chain
exercises.12–14 After finding that the standard PUP (SPP)
and knee PUP exercises induced the highest SA and
lowest UT : SA EMG measures, Ludewig et al8 recommended these exercises for selective SA strengthening.
Researchers5,9,15–26 have investigated whether the PUP
exercise performed on different unstable bases stimulated
mechanoreceptors and increased SA EMG activity,
thereby enhancing shoulder-joint stabilization. The use
of unstable or stable surfaces during the PUP exercise is
under debate. Some authors9,19 have suggested that
performing the PUP exercise on an unstable base can
lead to greater recruitment of related muscles, whereas
others14,18 have indicated that performing the exercise on
an unstable surface did not increase SA activity.
Moreover, the PUP exercise performed on an unstable
surface could generate higher UT activity.27 However, no
difference in UT activation has been reported.28 To our
knowledge, no investigators have published systematic
reviews with meta-analyses in which they examined how
PUP exercises performed on stable and unstable surfaces
affected SA and UT EMG activity.
Other PUP modifications have been examined. One
modification that may increase SA activity is performing
the exercise on 1 hand.29,30 The influence of lower
extremity extension on scapular-muscle activity during
the PUP exercise has also been studied.29 Maenhout et al29
proposed that tightening the thoracolumbar fascia using a
gluteus maximus muscle contraction during extension of
the lower extremity in the PUP exercise may alter
scapular-muscle activity. The functional length of the
SA can change the contraction distance of the muscle,
which affects muscle activity. Researchers16,31–34 have
examined muscle activity using different hand orientations
and at shoulder-flexion angles of 1108, 908, and 708 during
the PUP exercise. Lee et al16 reported larger SA EMG
activity during the PUP exercise with the shoulder
externally rotated than with it in neutral or internally
rotated. Kim et al17 found that SA activity during the PUP
exercise was higher when the ipsilateral lower extremity
was raised than when the base of support (stable or
unstable surface) was changed. Furthermore, performing
the PUP exercise on an unstable surface would only
challenge the external oblique and internal oblique
muscles, which could facilitate lumbar stabilization.
Lehman et al18 suggested that push-ups with the feet on
an exercise bench and the hands on the floor had a greater
influence on SA muscle activity. However, despite these
influential factors, no standard exists for how the PUP
exercise should be performed.
Considering the closed kinetic chain of the whole body
during PUP exercise performance, we analyzed the effects
of different factors acting concurrently on SA and UT
muscle activity in this review. Therefore, the purpose of our
study was to (1) analyze the effectiveness of varied PUP
exercises on SA and UT muscle activity and (2) conduct a
meta-analysis to verify the effects on SA and UT muscle
activity of performing the PUP exercise on different
surfaces (eg, a Swiss ball, wobble ball, or suspension sling).
METHODS
Search Strategy
This review followed the Preferred Reporting Items for
Systematic Reviews and Meta-Analyses (PRISMA) guidelines.35 Using PROSPERO, we confirmed that our research
did not duplicate a review being conducted by another team
and had not been registered. A systematic search was
conducted on 2 databases, PubMed and Scopus, using 2
search strategies, with 1 related to each purpose. For the
first purpose, published articles related to PUP variation
exercises were included. Key words were push-up plus and
electromyography. For the second purpose, studies comparing SA and UT activity during the PUP exercise
performed on stable and unstable surfaces were selected.
Key words were healthy subject, push-up plus, electromyography, and stable/unstable surface. Full search syntaxes
can be found in the Supplemental Table (available online at
http://dx.doi.org/10.4085/1062-6050-237-18.S1). Secondary searches were performed by (1) scanning the reference
list of each full text that was evaluated and (2) performing
citation tracking of the included studies. This search was
limited to articles published between January 1, 2000, and
March 31, 2018.
Inclusion Criteria and Outcome Measurement
To be included in our study, articles had to be written in
English. Studies were included in the systematic review if
the authors examined different PUP exercises by analyzing
SA and UT EMG activity. For the meta-analysis, we
included studies that were conducted of SA and UT EMG
activity during the PUP exercise on stable and unstable
surfaces and excluded those that did not provide means and
standard deviations.
To reduce selection bias, 2 authors (F.J.K., H.L.O.)
independently conducted the search processes. Studies were
excluded based on the title, abstract, or full text.
Disagreements were resolved by discussion and consensus
with a third author (J.J.L.).
Data Extraction and Assessment of Risk of Bias
Two investigators (F.J.K., H.L.O.) separately extracted
data from each trial. The data extracted from the selected
studies were participant characteristics, information on
exercise protocols, and details of the outcome measurements. When conflicts occurred in study qualifications
Journal of Athletic Training
1157
Figure 1. Flow chart showing article selection.
between the data extractions, they were resolved by a third
author (J.J.L.).
All included studies were assessed by 2 reviewers using
the Critical Appraisal Skills Program, an evaluation tool for
observational studies.36 The 6 criteria for evaluation were
matching of participants and controls, a power calculation
justifying the sample size, reproducibility of the electrode
positions, reliability of the EMG equipment, the tester
being blinded to group allocation, and sufficient results in
the text or supplied by the authors. If information about any
of the 6 criteria was not found in the article, a score of 0
was given. A third author (J.J.L.) settled any conflicts in
study assessments.
Statistical Analysis
For the systematic analysis, the following data were
extracted from the included articles: (1) author, year, and
study design; (2) participant characteristics; (3) type of PUP
intervention; (4) EMG outcome measures; and (5) main
results. If data were missing, 2 researchers (F.J.K., H.L.O.)
attempted to contact the authors to request the required
information. A meta-analysis was deemed unfeasible for
this part because of the small number of studies.
For the meta-analysis, the EMG data of the SA and UT
were calculated using the mean difference (MD) with a
95% confidence interval (CI). During the PUP exercise, a
positive effect size implied favorable outcomes on an
unstable surface. All data were pooled using a random
model of meta-analysis. Statistical heterogeneity across
studies was quantified using I2 statistics: likely not
important (0%–30%), moderate heterogeneity (31%–
50%), substantial heterogeneity (51%–75%), and consid1158
Volume 54 Number 11 November 2019
erable heterogeneity (76%–100%), as recommended by
Higgins and Green.37 Publication bias was examined using
funnel plots. The a level was set at .05. We used Review
Manager (version 5.3; The Cochrane Collaboration,
Copenhagen, Denmark) to analyze the statistics.
RESULTS
Study Selection
The full search strategy and selection process are outlined
in Figure 1. The initial database search was completed on
March 31, 2018. We identified 30 study titles that
potentially met the inclusion criteria. Of the 11 excluded
studies, 3 examined different exercise types,12,38 and 8 used
outcome measures other than EMG activity.39–46 Nineteen
articles were included in the final analysis. Seven articles
examined the effects of PUP variations (eg, performing the
exercise in a standing or lying position8 or using different
upper or lower extremity positions29,31,47–50) on SA and UT
muscle activity. Twelve articles focused on the effects of
the base of support during PUP exercises.9,15–23,51,52 After
further checking for the meta-analysis, 1 article was
excluded due to insufficient data for the means and
standard deviations.51 Therefore, 11 articles were included
in this meta-analysis for analyzing the differences in SA
and UT muscle activity during the PUP performed on stable
and unstable surfaces.9,15–23,52
Quality Assessment
The assessment of study quality is presented in Table 1.
We did not include studies in which the testers were
blinded to group allocation. Also, only data from healthy
Table 1. Study Design and Methodologic Evaluation
Criteriona
Study
Ludewig et al8 (2004)
Lehman et al18 (2008)
Maenhout et al29 (2010)
Park and Yoo9 (2011)
Kim et al17 (2011)
Lee et al16 (2013)
Yoon and Lee23 (2013)
Seo et al22 (2013)
De Mey et al21 (2014)
Kim et al20 (2014)
Pirauá et al19 (2014)
Lee et al31 (2014)
San Juan et al47 (2015)
Batbayar et al48 (2015)
Gioftsos et al15 (2016)
Kim et al49 (2017)
Hwang et al50 (2017)
Torres et al52 (2017)
a
Participant
Selection?
Control
Match?
Justify
Sample Size?
Electrode
Position?
Reliability
Test?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Yes
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Not stated
Yes
Not stated
Not stated
Not stated
Tester
Blinded?
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
stated
stated
stated
stated
stated
stated
stated
stated
stated
stated
stated
stated
stated
stated
stated
stated
stated
stated
Sufficient
Results?
Score
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
5
3
3
3
3
3
3
3
3
4
3
3
3
3
4
3
3
3
Each item was scored as 1 (yes) or 0 (no or not stated) based on whether the study included information about the criterion.
participants were included. All studies provided data from
the electrode positions.
Synthesis of Results and Meta-Analysis
For the systematic review, we included the 7 articles in
which the authors examined the effects of PUP variations
on SA and UT muscle activity. The characteristics of the
participants, interventions, outcome measures, and main
results of the included studies are presented in Table 2. The
sample sizes of the included studies ranged from 9 to 47
participants.
For the meta-analysis, 11 articles were included.9,15–23,52
These articles involved a total of 213 participants, and all
addressed PUP exercise programs on stable and unstable
surfaces (Table 3). For the EMG outcome measures, we
extracted data for the SA and UT (Table 2). The forest plot
of the mean difference in SA EMG activity revealed no
difference (0.01% maximal voluntary isometric contraction; 95% CI ¼ 4.90, 4.92) between stable and unstable
surfaces (Figure 2A). However, the forest plot of the mean
difference in UT EMG activity (2.85% maximal voluntary
isometric contraction; 95% CI ¼ 5.51, 0.19) revealed a
difference between stable and unstable surfaces, with more
UT activity elicited by unstable than stable surfaces (Figure
2B).
Despite using different methods to evaluate SA and UT
EMG activity, we observed no heterogeneity among the
analyzed studies (SA: P ¼ .10, I2 ¼ 37%; UT: P ¼ .80, I2 ¼
0%). As determined by the Begg test, all P values were
more than .05 without obvious funnel-plot asymmetry,
revealing no publication bias for the effect sizes of SA and
UT EMG activity (Figure 3).
DISCUSSION
Based on the database search, we included 18 articles in
this review. Seven articles discussed the effects of PUP
variations (eg, different upper extremity,31,47,48,50 lower
extremity,29,49 and PUP8 positions) on training the SA and
UT. Eleven articles9,15–23,52 focused on the effects of the
base of support for PUP exercises. From our systematic
review, we determined a suitable exercise prescription for
training the SA and UT using PUP variations. During the
PUP exercise, participants generated higher SA EMG
activity and lower UT EMG activity with full elbow
extension at normal shoulder width (hand placement
equal to the participant’s shoulder width) and shoulderflexion angles of 1108 or 1208 while lifting the ipsilateral
lower extremity. Moreover, according to the 11 articles,
no difference in SA activity between stable and unstable
surfaces was found during the PUP exercises. Yet more
UT activity was generated on an unstable than a stable
surface while performing. Activation of the UT likely
increased during the PUP exercise when participants used
an unstable surface because the hands were off the
ground; if the feet maintained the same normalized
position, raising the hands off the ground moved the
glenohumeral joint into increased flexion, causing scapular elevation.
Whereas the SPP is an optimal exercise prescription for
scapular-muscle training, the hand position, elbow flexion,
shoulder flexion, and lower extremity extension all affect
SA activation. Researchers8,47 have found that the SPP
elicited higher SA EMG activity and a lower UT : SA ratio
than the knee or elbow PUP. Batbayar et al48 reported that
different hand positions induced differences in SA EMG
activity. During the SPP, hand placement at normal
shoulder width resulted in better SA EMG activity and a
better UT : lower trapezius ratio than hand placement at a
narrower or wider shoulder width.48 Lee et al31 noted that
during the PUP exercise, the greatest SA muscle activity
occurred at 1108 of shoulder flexion. Hwang et al50 also
observed that 1208 of shoulder flexion should be used
during the PUP exercise because it produces greater SA
activation than 608 or 908 of shoulder flexion. Investigators29,49 have also demonstrated that lower extremity
Journal of Athletic Training
1159
Table 2. Study Characteristics of Selected Articles Continued on Next Page
Study
Outcome Measure:
Electromyographic Activity
Participants
Intervention(s)
Ludewig et al
(2004)
19 Healthy, 11 with
shoulder pain or
dysfunction
UT and SA
Lehman et al18
(2008)
Maenhout et al29
(2010)
10 Healthy
Park and Yoo9
(2011)
Kim et al17 (2011)
14 Healthy
14 Healthy
Lee et al16 (2013)
20 Healthy
Standard PUP exercise, knee
PUP exercise, elbow PUP
exercise, and wall PUP
exercise
SPP exercise on stable and
unstable surfaces
Knee PUP exercise in 7
positions: standard knee PUP
exercise, knee PUP exercise
with heterolateral lower
extremity extension, knee PUP
exercise with homolateral lower
extremity extension, knee PUP
exercise with a wobble board,
knee PUP exercise with
heterolateral lower extremity
SPP exercise on stable and
unstable surfaces
Knee PUP exercise on stable
and unstable surfaces
Knee PUP exercise on stable
and unstable surfaces
Yoon and Lee23
(2013)
Seo et al22 (2013)
20 Healthy
SPP exercise on stable and
unstable surfaces
SPP exercise on stable and
unstable surfaces
Knee PUP exercise on stable
and unstable surfaces
UT, SA, latissimus dorsi,
and infraspinatus
UT, SA, LT, MT, and
latissimus dorsi
UT, SA, LT, MT, anterior
deltoid, posterior deltoid,
pectoralis major, and
latissimus dorsi
SA
8
32 Healthy
10 Healthy
De Mey et al21
(2014)
47 Healthy
Kim et al20 (2014)
15 Healthy
Pirauá et al19
(2014)
30 With scapular
dyskinesis (types
1 and 2 scapular
winging)
15 Healthy
Lee et al31 (2014)
Knee PUP exercise on stable
and unstable surfaces
SPP exercise on stable and
unstable surfaces
Knee PUP exercise on an
unstable surface during 3
different shoulder-flexion
angles: 708, 908, and 1108
SPP exercise and knee PUP
exercise at different elbow
positions: 58 increments from
1008 of flexion to full extension
UT, SA, LT, and biceps
brachii
UT, SA, LT, and MT
UT and SA
UT, SA, external oblique,
and internal oblique
UT, SA, LT, and pectoralis
major
UT, SA, and LT
SA muscle activity: unstable .
stable surface
No differences between stable and
unstable surfaces
No differences between stable and
unstable surfaces
SA muscle activity: hands
positioned at 908 of external
rotation . hands positioned at
neutral or 908 of internal rotation
SA muscle activity: unstable .
stable surface
No differences between stable and
unstable surfaces
SA muscle activity: stable .
unstable surface
SA muscle activity: unstable .
stable surface
UT : SA ratio: unstable . stable
surface
SA muscle activity: shoulder flexion
of 1108 . 908 . 708
UT, SA, LT, and
infraspinatus
SA muscle activity: SPP exercise
. knee PUP exercise
Increasing elbow flexion during the
PUP exercise elicited higher UT
activity, lower SA activity, and a
higher UT : SA ratio
SA muscle activity decreased in
narrower and wider shoulder
widths
30% narrower shoulder width:
higher pectoralis major and
triceps activity
30% wider shoulder width: higher
UT : LT ratio
SA muscle activity: stable .
unstable surface
SA muscle activity was affected by
the exercise phase and hand
position but not by the support
surface
22 Healthy
Batbayar et al48
(2015)
9 Healthy
SPP exercise at different
shoulder widths: shoulder
width, narrower shoulder width,
wider shoulder width
UT, SA, LT,MT, anterior
deltoid, pectoralis major,
latissimus dorsi, and
triceps brachii
Gioftsos et al15
(2016)
13 Healthy
SPP exercise on stable and
unstable surfaces
UT, SA, and LT
Volume 54 Number 11 November 2019
The UT : SA ratio for both groups:
SPP exercise , knee PUP
exercise , elbow PUP exercise
, wall PUP exercise
No differences between stable and
unstable surfaces
Higher SA muscle activity and
lower UT : SA ratio: knee PUP
exercise with ipsilateral lower
extremity extension
Higher LT muscle activity: knee
PUP exercise with contralateral
lower extremity extension
UT, SA, and pectoralis
major
San Juan et al47
(2015)
1160
Results or Comment
Table 2. Study Characteristics of Selected Articles Continued From Previous Page
Study
49
Kim et al
(2017)
Outcome Measure:
Electromyographic Activity
Participants
Intervention(s)
20 Healthy
Knee PUP exercise with
dominant lower extremity
extended: apply to resistance
in abduction, adduction,
extension, and flexion
SPP exercise on a stable surface
during 3 different shoulderflexion angles: 608, 908, and
1208
SPP exercise on stable and
unstable surfaces
Hwang et al50
(2017)
29 Healthy
Torres et al52
(2017)
20 Healthy
Results or Comment
UT, SA, external oblique,
and internal oblique
Higher SA muscle activity: knee
PUP exercise with the lower
extremity lifted was maintained
against extension
UT, SA, and pectoralis
major
SA muscle activity: shoulder flexion
of 1208 . 908 . 608
UT, SA, MT, LT, anterior
deltoid, posterior deltoid,
biceps brachii, triceps
brachii, and pectoralis
major
SA muscle activity: unstable .
stable surface
Abbreviations: LT, lower trapezius; MT, middle trapezius; PUP, push-up plus; SA, serratus anterior; SPP, standard push-up plus; UT, upper
trapezius.
extension also influences SA EMG activity during the PUP
exercise. When the ipsilateral lower extremity is extended,
the contralateral extremity bears more weight, resulting in
greater hip stabilization. This activates the contralateral
internal oblique muscle, which in turn stimulates the
ipsilateral external oblique muscle, possibly resulting in
greater SA muscle recruitment.
Interestingly, we found no difference in SA EMG
activity when the PUP exercise was performed on stable
and unstable surfaces. As a closed kinetic chain exercise,
the PUP would presumably stimulate the mechanoreceptors and enhance shoulder-joint and scapular stabilization.
This stimulus is suggested to increase on an unstable
base, possibly challenging neuromuscular control. 53
However, from our review, it appears that using different
kinds of base support was not the major factor affecting
SA EMG activity during the PUP exercise. Other factors,
such as hand position,15,16 neuromuscular control,53 or
upper extremity weight-bearing status,18,30 may overcome
the effects of the base of support. Gioftsos et al15
determined that the SA and UT activations during the
PUP exercise were not affected by the support surface but
were affected by the phase of the exercise and the hand
position. Lee et al16 also reported that positioning the
hands at 908 of external rotation during the PUP exercise
elicited more SA EMG activity than positioning the hands
at neutral or 908 of internal rotation. Moreover, a high
correlation (r ¼ 0.97, P , .01) existed between increasing
weight-bearing posture and muscular activity during the
PUP.30
The various parts of the SA muscle are activated
differently during the PUP exercise. Park and Yoo9 studied
the upper and lower portions of the SA using surface EMG.
In healthy participants, the lower fibers of the SA showed
increased activation on an unstable surface, which required
more joint stability than a stable base; however, the upper
fibers showed no difference between the stable and unstable
surfaces. Inman et al54 indicated that the lower portions of
the SA and trapezius were crucially important in stabilizing
the inferior angle of the scapula during upper extremity
Table 3. Differences in Upper Trapezius and Serratus Anterior Electromyographic Muscle Activity During Push-Up Plus Exercise on
Stable and Unstable Surfaces, Mean 6 SD
Electromyographic Muscle Activity
Upper Trapezius
Study (Year), Measure
Lehman et al18 (2008), % MVIC
Park and Yoo9 (2011), % reference voluntary
isometric contraction
Kim et al17 (2011), % MVIC
Lee et al16 (2013), % MVIC
Yoon and Lee23 (2013), % MVIC
Seo et al22 (2013), % MVIC
De Mey et al21 (2014), % MVIC
Kim et al20 (2014), % MVIC
Pirauá et al19 (2014), % MVIC
Gioftsos et al15 (2016), % MVIC
Torres et al52 (2017), % reference voluntary
isometric contraction
Serratus Anterior
Stable Surface
Unstable Surface
Stable Surface
Unstable Surface
5.2 6 6.4
10.5 6 6.9
24.2 6 14.5
19.7 6 11.5
14.48
18.6
15.8
25
4.61
12.80
6 17.91
6 16.7
6 10.2
6 11.55
6 3.33
6 11.91
NA
36.4 6 22.01
23.8 6 8.0
15.49
20.1
19.5
21.75
6.91
17.91
6 17.84
6 17.3
6 28.6
6 10.5
6 7.10
6 45.57
NA
47.9 6 26.57
27.0 6 7.36
73.05 6 58.78
67.58 6 48.73
102.65
78.6
39.5
24.8
29.84
57
37.79
76.34
66.7
6
6
6
6
6
6
6
6
6
45.15
11.9
12.2
10.3
10.36
27.24
14.41
33.82
17.5
74 6 37.52
119.04
83.5
43.2
28.7
39.37
46.27
34.17
61.71
60.6
6
6
6
6
6
6
6
6
6
51.08
12.0
12.1
12.25
24.92
22.79
15.86
29.38
13.7
103.02 6 53.55
Abbreviations: MVIC, maximal voluntary isometric contraction; NA, not available.
Journal of Athletic Training
1161
Figure 2. Forest plots demonstrating the individual point estimates and overall effect sizes for the questions, A, ‘‘Does the push-up plus
exercise on an unstable surface elicit higher serratus anterior electromyographic muscle activity?’’ and, B, ‘‘Does the push-up plus
exercise on an unstable surface elicit higher upper trapezius electromyographic muscle activity?’’ Abbreviation: CI, confidence interval.
movement. Taking this point of view, the lower part of the
SA would seem to demonstrate greater activity in
stabilizing the scapula on an unstable surface; however,
many researchers who used surface EMG to detect muscle
activity focused only on the lower part of the SA.
Therefore, in the future, investigators should focus on
other parts of the SA during the PUP exercise.
To our knowledge, this review is the first to systematically summarize the activity of the SA and UT during the
PUP variation exercise and our meta-analysis is the first to
summarize the activity of the SA and UT during the PUP on
a stable or unstable surface. However, our study had some
methodologic limitations. Few authors of the included
studies justified their sample sizes or performed reliability
tests.
Motor control during the different PUP exercises is
unclear. More research is needed to address motor control
of variables such as muscle timing or recruitment patterns
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during the PUP exercise and to investigate other shoulder
and scapular muscles, such as the lower trapezius, middle
trapezius, and rotator cuff. Moreover, it would be
worthwhile to study kinematic motion during the PUP to
understand the relationships between muscle activity and
the movements of humeral internal and external rotation
and scapular upward and downward rotation.
CONCLUSIONS
Participants can generate higher SA and lower UT EMG
activity if they perform the PUP exercise in full elbow
extension, at normal shoulder width, at shoulder-flexion
angles of 1108 or 1208, and while lifting the ipsilateral
lower extremity. Performing the PUP exercise on an
unstable surface may induce higher levels of UT activation
but will not increase SA activation. If the goal of the
exercise program is to strengthen the SA muscle with less
Figure 3. Funnel plots demonstrating that publication bias was
unlikely for electromyographic muscle activity during the push-up
plus exercise on stable and unstable surfaces for the, A, serratus
anterior and, B, upper trapezius.
UT activity, the PUP exercise should be performed on a
stable surface.
ACKNOWLEDGMENTS
This review was supported by award 104-2314-B-002-026MY13 from the Ministry of Science and Technology, Taiwan.
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SUPPLEMENTAL MATERIAL
Supplemental Table. Searching strategy using Scopus
and PubMed.
Found at DOI: http://dx.doi.org/10.4085/1062-6050-23718.S1
Address correspondence to Jiu-Jenq Lin, PhD, Department of Physical Medicine and Rehabilitation, National Taiwan University
Hospital, No. 1 Changde Street, Zhongzheng District, Taipei, Taiwan, 100. Address e-mail to jiujlin@ntu.edu.tw.
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