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Eects of push-up exercise on shoulder stabilizer
muscle activation according to the grip thickness of
the push-up bar
Jaemin Jung, PhD1), Woonik Cho, PhD2)*
1) Department of Physical Therapy, College of Science, Kyungsung University, Republic of Korea
2) Division of English Interpretation and Translation Studies, Busan University of Foreign Studies:
Namsan-dong, Geumjeong-gu, Busan 609-815, Republic of Korea
Abstract. [Pur pose] This study investigated the effects of bar thickness on shoulder stabilizer muscle activation
during push-up exercise. [Subjects] Twenty-six healthy male adults in their twenties. [Methods] The study had four
experimental conditions (gr ip thicknesses of 0%, 50%, 75%, and 100% of the subjects’ hand size). Measurements
were conducted from the start to the end of push-up for deltoid anterior ber, deltoid posterior ber, infraspinatus,
serratus anterior, and pectoralis major muscle activation. [Results] The deltoid anterior ber muscle activity was
4,852.6 ± 975.2 in the 0%, 5,787.3 ± 1,514.1 in the 50%, 5,635.3 ± 1,220.1 in the 75%, and 5,032.9 ± 841.0 in the 100%
condition. The infraspinatus muscle activity was 1,877.2 ± 451.3 in the 0%, 2,310.9 ± 765.4 in the 50%, 2,353.6 ±
761.9 in the 75%, and 2,016.8 ± 347.7 in the 100% condition. The pectoralis major muscle activity was 1,675.8 ±
355.1 in the 0%, 2,365.5 ± 1,287.3 in the 50%, 2,125.3 ± 382.5 in the 75%, and 1,878.8 ± 419.7 in the 100% condi-
tion, showing signicant differences respectively. [Conclusion] The use of push-up bars with different thicknesses
customized to personal characteristics, rather than the conventional standard, could be more effective for training
and rehabilitation.
Key words: Electromyogram, Push-up bar, Shoulder stabilizer muscle
(This article was submitted Jun. 3, 2015, and was accepted Jun. 24, 2015)
INTRODUCTION
Pain and dysfunction of the shoulder joint is one of the
most common musculoskeletal disorders1). The balance
among stabilizer muscles is considered important in thera-
peutic exercise programs for the prevention and rehabilita-
tion of a dysfunctional shoulder joint. Moreover, several
types of rehabilitation programs are available for patients.
From the aspect of motor mechanics, a closed kinetic chain
exercise is often used2).
The push-up exercise is a representative closed kinetic
chain exercise of the upper extremity. It is an easy exercise
for strengthening the muscles around the shoulder and is
hence widely used as a general therapeutic exercise for im-
proving the shoulder function of individuals with shoulder
problems3). Many studies have examined the enhancement
of shoulder joint muscle activation during the push-up
exercise. Compared with a push-up exercise on a stable
surface, a push-up exercise on an unstable surface increases
the activity of the shoulder stabilizer muscles and effectively
improves balance through the stimulation of muscle proprio-
ceptors during rehabilitation exercise4).
Lee et al. reported strong activation of the shoulder stabi-
lizer muscles, even when a small weight load is used, during
abduction-adduction via distal exor muscle activation.
They also observed that movement with nger exor muscle
activation had a substantial effect on the activation of the
shoulder stabilizer muscles5). Another study indicated that a
push-up plus exercise using a push-up bar was more effec-
tive than that performed on at ground. The push-up bar ex-
ercise increased the muscle activation of the forearm exor
bundle for gripping, which further led to increased activation
of the shoulder stabilizer muscles6). These ndings suggest
that along with the use of various support surfaces during
the push-up exercise for the rehabilitation of the shoulder
joint, the use of a push-up bar is another effective method
for both stimulating the proprioceptors and increasing the
muscle activation of the shoulder stabilizer muscles.
However, previous studies have investigated the effects
of the push-up exercise using the push-up bar on shoulder
stabilizer muscle activation, solely based on grip direction
and use. Hence, the effects of the grip thickness of the push-
up bar on shoulder stabilizer muscle activation are unclear.
This present study aimed to examine the effects of the grip
thickness of the push-up bar on shoulder stabilizer muscle
activation during push-up exercise.
J. Phys. Ther. Sci.
27: 2995–2997, 2015
*Corresponding author. Woonik Cho (E-mail: cloud@bufs.
ac. kr)
©2015 The Society of Physical Therapy Science. Published by IPEC Inc.
This is an open-access article dist ributed under the terms of the Cre-
ative Commons Att ribution Non-Commercial No Derivatives (by-nc-
nd) License <ht tp://creativecommons.org/licenses/ by-nc-nd/3.0/>.
Original Article
J. Phys. Ther. Sci. Vol. 27, No. 9, 20152996
SUBJECTS AND METHODS
The subjects were 26 male adults in their twenties who had
no low back pain or musculoskeletal disease of the shoulder
complex and upper limbs, had a normal range of motion,
and could perform push-ups. This research complied with
the ethical principles of the Declaration of Helsinki. All of
the participants who voluntarily participated in the research
experiment fully understood the experimental procedure and
method before participation. In particular, all of the subjects
read, understood, and signed the written consent form dis-
tributed. In addition, none of the processes in this research
was harmful to the human body. The age, weight, and height
(mean ± SD), and hand length (mean) of the subjects were
22.16 ± 2.23 year, 68.02 ± 10.86 kg, and 171.22 ± 3.58 cm,
and 19.2 cm, respectively.
In each condition, the push-up was started at a crawling
position, with both hands on the oor or holding a push-up
bar grip at shoulder width and the third nger below the
acromioclavicular joint. When holding the grip, each subject
was guided to seize the grip as strongly as possible by us-
ing the forearm muscles. After the subject’s shoulder was
accurately positioned, both feet were placed close together,
with the knees in a comfortable position and the pelvis in a
neutral position7).
The experiments were conducted under four conditions.
The rst condition was 0%, and the subjects performed the
push-up exercise on the 10-cm high box in order to make the
same height as that of the push-up bar. The second condition
was 50%. The subjects performed the push-up exercise with
a grip thickness of 50% of their hand size. The third condition
was 75%. The subjects performed the push-up exercise with
a grip thickness of 75% of their hand size. The fourth condi-
tion was 100%. The subjects performed the push-up exercise
with a grip thickness of 100% of their hand size. Their hand
size was determined as the length from the proximal point of
the lunate to the end of the distal phalanx of the third nger
and set as 100%. The push-up bar was manufactured by Nike
Inc. (EFO114-085, USA). The grip thickness was adjusted in
line with each condition (50%, 75%, or 100%) by winding
a taping tape around the push-up bar grip according to the
hand size measured.
To measure muscle activation in the shoulder stabilizer
muscles, electrodes were attached to the deltoid anterior
ber, deltoid posterior ber, infraspinatus, serratus anterior,
and pectoralis major. Muscle activation was measured by the
researcher from the start to the end of one push-up. Muscle
activation was measured from the start to the end of a push-up
exercise. The exercise was repeated three times under each
condition, and the average of the three measurements was
determined. The effects of muscle fatigue were prevented
by randomly arranging the conditions (0%, 50%, 75%, or
100%) and allowing a 5-min rest between each condition.
Electromyography (EMG) was performed after depilating
with a razor the parts for electrode attachment, removing
the horny layer with sand paper, and cleansing the area with
an alcohol swab to collect accurate data. ProComp Inniti
(Thought Technology Ltd., Canada) was used for measure-
ment of muscle activation. A surface electrode (Triode,
Thought Technology Ltd.) consisting of a tripolar electrode
(positive-ground-negative) was used. The frequency range
of the electromyographic signals was set to 20 to 500 Hz,
and the sampling frequency was set to 1,024 Hz.
The root mean square values of each muscle were mea-
sured for 5 seconds in the anatomical position. The relative
muscle contraction was calculated with respect to the mean
EMG signal for 3 seconds in the middle portion of the
muscle, excluding the measurements for the rst and last
seconds. The muscle activation resulting from one push-up
was expressed as the relative muscle contraction in %RVC.
PASW (Ver. 19) for Windows was used for data analysis.
In order to compare shoulder stabilizer muscle activation
between the push-up grip thicknesses, one-way analysis of
variance was performed. Meanwhile, the Tukey test was
used as a post hoc test to verify the differences between each
condition. The level of signicance was set at p = 0.05.
RESU LTS
The deltoid anterior ber muscle activity was 4,852.6 ±
975.2 in the 0%, 5,787.3 ± 1,514.1 in the 50%, 5,635.3 ±
1,220.1 in the 75%, and 5,032.9 ± 841.0 in the 100% condi-
tion, showing differences respectively. The post hoc test re-
vealed signicant differences between the 0%, 75%, 100%,
and 50% conditions (p < 0.05). Infraspinatus muscle activity
was 1,877.2 ± 451.3 in the 0%, 2,310.9 ± 765.4 in the 50%,
2,353.6 ± 761.9 in the 75%, and 2,016.8 ± 347.7 in the 100%
condition. The post hoc test showed signicant differences
between the 0%, 50%, 100%, and 75% conditions (p < 0.05).
The pectoralis major muscle activity was 1,675.8 ± 355.1 in
the 0%, 2,365.5 ± 1,287.3 in the 50%, 2,125.3 ± 382.5 in the
75%, and 1,878.8 ± 419.7 in the 100% condition, showing
signicant differences as well. The post hoc test showed sig-
nicant differences between the 0%, 75%, 100%, and 50%
conditions (p < 0.01; Table 1).
DISCUSSION
Lee et al. reported that the stimulation of the distal part
due to the weight load on the forearm during shoulder joint
movement caused strong activation of the shoulder stabilizer
muscles. This nding indicated that the activation of the
nger exor had a major effect on shoulder muscle activa-
tion5). They also reported that for shoulder stabilizer muscle
activation, a push-up exercise with a push-up bar was more
effective than a push-up exercise on a at oor owing to
the involvement of the forearm nger exor6). This present
study aimed to identify the effects of push-up bar thickness
on shoulder stabilizer muscle activation during push-up
exercise.
Lee et al. observed forearm muscle activation at grip
thicknesses of 0%, 25%, 50%, 75%, and 100%. They
reported that maximum muscular activity occurred at grip
thickness of 50% and 75% for the wrist extensor bundle, and
at grip thickness of 75% for the exor digitorum super-
cialis. These results indicated the close relationship of the
length-tension curve7).
The conditions in the present study were similar to those
used by Lee et al.7), namely grip thicknesses of 0%, 50%,
75%, and 100%. However, a thickness of 25% was not used
2997
in the present study, as the thickness of the push-up bar was
approximately 45% of the subjects’ hand size. In the present
study, a signicantly high muscular activity was noted at the
deltoid anterior ber and pectoralis major at a push-up bar
grip thickness of 50%, and at the infraspinatus at a push-up
bar grip thickness of 75%. In addition, high muscular activ-
ity was observed at the deltoid posterior ber and serratus
anterior at a push-up bar grip thickness of 50% and 75%,
although this increase was not signicant. These results in-
dicate that a push-up bar grip thickness of 50% and 75% was
effective for the activation of the forearm muscles during
push-up exercise, which may have consequently inuenced
the activation of the shoulder stabilizer muscles during the
push-up exercise.
The present study ndings indicate that the effects of the
exercise could be improved simply by changing the grip
thickness of the distal part in order to induce strong activa-
tion of the muscles of the proximal part. Thus, the use of
push-up bars with a thickness customized according to indi-
viduals’ characteristics could be more effective for training
and rehabilitation than the use of a conventional standard
push-up bar.
Further studies are required to verify the effect of grip
thickness of standard elastic bands, dumbbells, or barbells in
open kinetic chain exercises.
ACKNOWLEDGEMENT
This research was supported by the research grant of the
Busan University of Foreign Studies in 2015.
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Tab le 1. Muscle activation (%RVC) under the push-up conditions
Muscle 0% 50% 75% 100 %
Deltoid anterior ber* 4,852.6 ± 975.2a5,787.3 ± 1, 514.1b5,635.3 ± 1,220.1a5,032.9 ± 841.0a
Deltoid posterior ber 2,023.2 ± 1,097.2 2,642.6 ± 1,121.6 2,597.0 ± 1,112.2 2,172.0 ± 1,155.9
Infraspinatus* 1,877.2 ± 451.3a2,310.9 ± 765.4a2,353.6 ± 761.9b2,016.8 ± 347.7a
Pectoralis major* 1,675.8 ± 355.1a2,365.5 ± 1,287.3 b2,125.3 ± 382.5 a1,878.8 ± 419.7 a
Serratus anterior 1,673.1 ± 725.9 a2,192.1 ± 1,147.6 a1,984.8 ± 899.9 a1,800.0 ± 941.34 a
The data represent mean ± SD values. The values with different superscripts in the same column were signicantly
different (p < 0.05) in the Tukey analysis. a : Signicant difference between 0% and 50%, b : Signicant difference
between 0% and 75%
