MUSCLE ACTIVATION DURING A DECLINE PUSH UP ON AN UNSTABLE
SURFACE

A THESIS
Submitted to the Faculty of the School of Graduate Studies
and Research
of
California University of Pennsylvania in partial
fulfillment of the requirements for the degree of
Master of Science

by
Kelsey Todd

Research Advisor, Dr. Edwin Zuchelkowski
California, Pennsylvania
2011

ii

iii

ACKNOWLEDGEMENTS

I would like to take the opportunity to thank all the
people who have helped me complete this thesis.
First, I would like to thank Dr. Zuchelkowski for
putting up with me and being able to take time out of his
schedule to meet with me on a weekly basis.

The amount of

time and patience this took is greatly appreciated.
I would like to thank my research assistant Catherine
Laur for helping me set up and run all the testing
sessions.

Thank you for dealing with the crazy times and

last minute scheduling.

Also, thank you for putting up

with the rollercoaster ride of a softball season with me!
I would like to thank the other two members of my
committee.

Shelly, thank you for always having your door

open so I could vent about anything and everything.
Hess, thank you for your expertise with stats.

Dr.

Without

your class and your help the hypothesis testing section
would not be as good as it is.

Also, thank you both for

all the time you have put into helping me finish this
thesis.

iv
Lastly I would like to thank my parents for their
support and encouragement throughout the year.

And to my

best friend, Barbara, for all the late night phone calls
and all the support she has given me over the course of the
year.

v
TABLE OF CONTENTS

Page
SIGNATURE PAGE

. . . . . . . . . . . . . . . . ii

AKNOWLEDGEMENTS . . . . . . . . . . . . . . . . iii
TABLE OF CONTENTS
LIST OF TABLES

. . . . . . . . . . . . . . . v

. . . . . . . . . . . . . . . . viii

LIST OF FIGURES . . . . . . . . . . . . . . . . ix
INTRODUCTION
METHODS

. . . . . . . . . . . . . . . . . 1

. . . . . . . . . . . . . . . . . . . 5

Research Design
Subjects

. . . . . . . . . . . . . . . 5

. . . . . . . . . . . . . . . . . . 6

Preliminary Research

. . . . . . . . . . . . . 7

Instruments . . . . . . . . . . . . . . . . . 8
Procedures

. . . . . . . . . . . . . . . . . 9

Hypotheses

. . . . . . . . . . . . . . . . . 12

Data Analysis
RESULTS

. . . . . . . . . . . . . . . . 12

. . . . . . . . . . . . . . . . . . . 13

Demographic Data . . . . . . . . . . . . . . . 13
Hypothesis Testing

. . . . . . . . . . . . . . 14

Additional Findings . . . . . . . . . . . . . . 16
DISCUSSION . . . . . . . . . . . . . . . . . . 20
Discussion of Results . . . . . . . . . . . . . 20
Conclusions . . . . . . . . . . . . . . . . . 27

vi
Recommendations

. . . . . . . . . . . . . . . 28

REFERENCES . . . . . . . . . . . . . . . . . . 31
APPENDICES . . . . . . . . . . . . . . . . . . 33
APPENDIX A: Review of Literature

. . . . . . . . . 34

Introduction . . . . . . . . . . . . . . . . . 35
Shoulder Anatomy . . . . . . . . . . . . . . . 35
Muscle Function. . . . . . . . . . . . . . . . 38
Measuring Muscle Activation . . . . . . . . . . . 39
Electromyography . . . . . . . . . . . . . . 40
Techniques of the Push Up
Stability Balls

. . . . . . . . . . . 42

. . . . . . . . . . . . . . . 48

Push Ups on a Stability Ball

. . . . . . . . . . 50

Summary . . . . . . . . . . . . . . . . . . . 52
APPENDIX B: The Problem . . . . . . . . . . . . . 54
Statement of the Problem . . . . . . . . . . . . 55
Definition of Terms . . . . . . . . . . . . . . 55
Basic Assumptions

. . . . . . . . . . . . . . 56

Limitations of the Study . . . . . . . . . . . . 56
Delimitations of the Study . . . . . . . . . . . 57
Significance of the Study

. . . . . . . . . . . 57

APPENDIX C: Additional Methods . . . . . . . . . . 59
Informed Consent Form (C1) . . . . . . . . . . . 60
Demographic Information Sheet (C2) . . . . . . . . 64
IRB: California University of Pennsylvania (C3) . . . 66

vii
Sample Individual Data Collection Sheet (C4) . . . . 78
REFERENCES . . . . . . . . . . . . . . . . . . 80
ABSTRACT

. . . . . . . . . . . . . . . . . . 82

viii

LIST OF TABLES
Table

Title

Page

1

Descriptive Statistics for Maximal Peak
Muscle Activation (%MVIC)
. . . . . . . 16

2

Effect of Peak Muscle Activation during
Push Ups . . . . . . . . . . . . . . 16

3

Significant Differences between
Muscle Pairs . . . . . . . . . . . . . 17

4

Descriptive Statistics for Mean Muscle
Activation (%MVIC). . . . . . . . . . . 19

ix

LIST OF FIGURES
Figure

Title

Page

1

Distribution of Subjects’ Age . . . . . . 14

1

INTRODUCTION

A common and very basic exercise is the standard push
up.

The push up is an exercise that helps strengthen the

upper body and the core.

It is also used to test the

strength and endurance of the arms, shoulders and chest.1
The push up is traditionally performed with both the hands
and the feet placed on the floor.

The body is kept in a

straight line from the head to the heels and is lowered to
the ground where the chest just barely touches and then is
returned to the starting position.

Gravity is responsible

for the movement seen during the first phase.

The muscles

forcefully contract to return the body from the ground to
the top position.2

The primary muscles involved in this

exercise are the pectoralis major, pectoralis minor,
serratus anterior, triceps and the wrist extensors.
However, stabilizer muscles such as the rectus abdominus,
internal and external obliques, and the hip flexors are
also important muscles as they keep the body in a straight
alignment.
When performing a push up, one might have to practice
the proper form until he/she is competent with the

2
exercise.

To make the exercise easier, a variation of the

standard push up can be performed by placing the knees on
the ground and producing a straight line from the knees to
the head.2

This variation reduces the amount of resistance

placed on the body, making the exercise less difficult.

On

the contrary, the level of difficulty can be increased by
performing the push up using one hand or on a piece of
equipment.
These multiple variations may act to increase or
decrease the relative contribution of a given muscle.
Previous studies have shown that by varying the hand
placement from the standard positioning to a narrow
position where the hands form a diamond shape, muscle
activation of the triceps brachii and pectoralis major was
increased.3 Other variants of the push up have been tested
and the results showed that the more dynamic the push up,
the greater the muscle activation.4
Over the years, performing exercises while on an
unstable surface has grown in popularity.

Stability balls

have been found in physical therapy clinics, gyms, strength
and conditioning programs and even in the home.

The

thought behind the use of a stability ball is that its
inherent instability places a higher demand on the
proprioceptors which sense where different parts of the

3
body are located with respect to one another.

More

importantly for the present study, instability is thought
to place a higher demand on postural muscles, therefore
causing the stabilizing muscles to activate at a higher
rate.5
In order to help achieve a greater outcome during a
workout, people have been adding an instability factor to
common exercises.

One such exercise is the push up.

This

exercise can be performed by placing the hands on the ball
with the feet on the ground or vice versa.

Limited

research has been conducted on this instability factor to
determine if it indeed creates an environment where muscles
are more active than normal.

Marshall and Murphy6 concluded

that an increase in muscle activation is dependent on the
particular exercise. Other authors’ results showed that by
replacing a stable surface with an unstable surface, muscle
activation was unchanged for a majority of the muscles
tested.5,7,8
Studies completed by Lehman5,8,9 have extensively looked
at the relationship between the use of a physioball and
mean muscle activation.

His first study looked at the

muscle activity of the trunk muscles during upper extremity
strength exercises performed on and off a physioball.9
later went on to experiment with the effects of a

He

4
physioball on the shoulder and scapulothoracic musculature
during multiple push up variations.5,8

All of his results

concluded that there was not a significant change in muscle
activity between the stable and unstable (physioball)
surfaces.
The purpose of this study was to further investigate
whether performing a push up off a physioball will increase
the level of muscle activation of four particular muscles.
This study also looked at the difference in muscle
activation between a standard push up and a decline push
up.

The results of this study could be beneficial to the

active population as well as physical therapists and
athletic trainers in knowing if there is a significant
difference in muscle activation levels between a standard
push up, a decline push up and a decline push up performed
on an unstable surface.

With this knowledge, people can

determine if it is actually beneficial to perform these
different push up variations in regards to muscle
activation level rather than the level of difficulty.

5

METHODS

The primary purpose of this study was to examine the
difference in muscle activation when an unstable surface is
used during a decline push up when compared to a stable
surface.

EMG activity was measured to evaluate muscle

activation of several muscle groups.

This section includes

the Research Design, Subjects, Instruments, Procedures,
Hypotheses and Data Analysis.

Research Design

This research was a within-subjects, repeated measures
design.

The independent variable was stability condition

with three levels; ground, bench and physioball.

The

dependent variable was muscle activation in each of the
four muscles (pectoralis major, external oblique, serratus
anterior, and lower trapezius) as measured by peak activity
of surface EMG.

6
Subjects

The subjects used for this study were 20 volunteer (10
male and 10 female) undergraduate and graduate students
from California University of Pennsylvania.

All subjects

were at least 18 years of age and were screened for a
history of shoulder, elbow and/or wrist injury within the
previous six months.

The subjects were active individuals

who all knew the basic technique of a push up.

An active

individual is defined as someone who engages in 30 minutes
of moderate exercise five days a week or 20 minutes of
vigorous exercise three days a week.10 The basic technique
of a push week or vigor up is defined as hands and feet
placed on the ground with back and knees straight.

The

feet are in dorsiflexion while the toes are in extension.
The subjects were required to establish the plank position
before being able to participate in the study.
Subjects also understood and agreed that it was
required to perform this study shirtless due to electrode
placement and interference with the leads.

Females were

required to wear a sports bra and shorts, while the males
wore only shorts.
feet.

The push ups were also performed in bare

7
All subjects in the study signed an Informed Consent
Form (Appendix C1) and filled out a demographic information
sheet (Appendix C2) prior to participation in the study.
Each participant’s identity remained confidential and was
not included in the study. The study was approved by the
Institutional Review Board (Appendix C3) at California
University of Pennsylvania prior to subject recruitment
and/or testing.

Preliminary Research

Pilot testing was performed to assess the experimental
design of the study.

An individual, who was not a subject

in the study, was used to perform this test.

This test was

used to review the protocol and to make sure the
instruments were working properly.

The researcher also

checked for the subject’s ability to understand the
directions, the amount of time used to complete each task,
and the accuracy of the protocol.

During this time, the

subject was taught the correct method of performing the
decline push up, including proper hand and feet placement
on the ground and ball/bench respectively.

The researcher

and the assistant also determined the proper placement of
electrodes per muscle.

8

Instruments

The researcher used a demographic sheet (Appendix C2)
to screen potential subjects.

The demographic sheet

determined the gender, age, level of physical activity,
history performing a push up and a physioball and if the
subject had an upper extremity injury within the previous
six months.

This study used a bench, physioball, a three

and one half inch wooden block, a metronome to keep the
proper pace, and Biopac MP150.

The bench and the

physioball sat approximately 45cm off the ground.

The

height of the physioball was checked prior to each testing
session.
In collecting the EMG data, the researcher used four
channels from a Biopac MP150 electromyography machine.

The

four channels were connected to electrodes located on the
pectoralis major, external oblique, serratus anterior and
lower trapezius.

The Biopac MP150 amplifer with wired

telemetry unit was connected to a laptop running Biopac
Acknowledge 4.0 software to collect and analyze the data.
The peak muscle activation as well as the mean activation
scores were collected.

The raw EMG signal was band pass

9
filtered at 10 and 1000 Hertz (Hz).5,8

The researcher

utilized a sampling rate of 2000 Hz.

Procedures

The Institutional Review Board at California
University of Pennsylvania approved all testing protocols
prior to experimentation (Appendix C3).

Each potential

subject filled out a demographic information sheet and
signed an informed consent form.

Once this was completed

there was a brief explanation reviewing the testing
protocol.
Prior to the initial set of tests, individuals were
instructed to properly perform the push up as directed by
the researcher.

Once the proper form was established, the

subject then performed a standard push up with the hands
and feet on the ground and then the decline push up with
his/her toes on the bench and again on the physioball.
The testing protocol consisted of measuring each
subject’s maximum voluntary isometric contraction of the
pectoralis major, external oblique, serratus anterior and
lower trapezius.

These four particular muscles were chosen

due to their location and function.

The pectoralis major

is the agonist muscle of the shoulder joint during the

10
concentric phase of the push up.

The serratus anterior is

an anterior shoulder girdle muscle and is the agonist
muscle of the shoulder girdle during the concentric phase
as well.2

The external oblique is a stabilizer muscle of

the lumbo-pelvic-hip complex,11 while the lower trapezius is
a posterior shoulder girdle muscle that is a stabilizer
muscle during the eccentric phase of the push up.2 The
pectoralis major electrode was placed four finger widths
below the clavicle and medial to the anterior axillary
border.

The external oblique electrode was placed 15cm

lateral to the umbilicus along the direction of muscle
fibers.5 For the serratus anterior, the electrode was placed
on the mid-axillary line of the muscle belly located over
the fifth rib. The lower trapezius electrode was placed 1.5
cm lateral to the T6 spinous process with the electrodes at
an inferior angle along the muscle fibers.8
For the testing protocol, the subjects were randomly
assigned as to which push up condition (ground, bench,
physioball) was performed first.

The sites of the

electrode placement were then prepared by cleaning the area
with alcohol pads to remove any dead skin and/or oil.
The EMG machine was turned on and connected to the
laptop to begin the testing.

The subject positioned

his/her hands so that the third phalanx was lined up with

11
the acromioclavicular joint on bilateral sides.5,8

The feet

were placed on the ball/bench so that the foot was
dorsiflexed and the toes were extended.

The only part in

contact with the ball/bench was the toes.

An assistant

helped place the subject’s feet on the ball/bench to limit
any potential injury.

The subject was instructed to lower

the body until his/her nose touched a three and one half
inch block.

He/she was instructed to eccentrically lower

the body for three seconds, hold the bottom position for
three seconds, concentrically raise the body for three
seconds, and then hold for a final three seconds at the top
position while listening to the beat of the metronome and
being prompted by the researcher.

This three second count

was adapted from Sandhu et al.7 The subjects performed one
set of three push ups per test. There was a minimum of a
three-minute rest between tests. The testing protocol was
performed one time per subject. The data was then collected
from the Biopac Acknowledge software and recorded on a data
collection sheet (Appendix C4) per subject.

12
Hypotheses

The following hypotheses were based on previous
research and the researcher’s intuition based on a review
of the literature.
1. There will be a difference in muscle peak activation
between the bench and physioball push ups compared to
the ground push up.
2. There will not be a difference in muscle peak
activation during the push up off the bench (stable
condition) compared to the push up off the physioball
(unstable condition).

Data Analysis

The research hypotheses were analyzed using a repeated
measures MANOVA.

All data was analyzed by Statistical

Package for Social Sciences (SPSS) version 18.0 for Windows
at an alpha level of ≤ 0.05.

All EMG scores were reported

as a percentage of maximal voluntary contraction.

13

RESULTS

The purpose of this study was to investigate the
difference in muscle activation during a decline push up
performed on an unstable surface (physioball) compared to a
stable surface (bench).

The following section contains

data collected throughout the study and is divided into
three subsections: Demographic Information, Hypotheses
Testing, and Additional Findings.

Demographic Information

There were 20 physically active individuals that
participated in this study.

The age range was 19-25 years

and the mean age was 20.95 years (Figure 1).

Ten (50%) of

the subjects were males and the remaining ten (50%) were
females.

Fifty percent of the subjects reported engaging

in physical activity at least 3-4 times a week.

The

remaining fifty percent reported participating in physical
activity 5-7 times a week.

Eight (40%) of the subjects

participated in an organized sport.

When asked how often

the subjects perform push ups, three (15%) responded daily,

14
eight (40%) weekly, four (20%) monthly and five (25%)
responded occasionally throughout the year.

9

Number of Subjects

8
7
6
5
4
3
2
1
0
19

20

21

22

23

24

25

Age

Figure 1. Distribution of Subjects’ Age

Hypothesis Testing

The following hypotheses were tested during this
study.

Both hypotheses were tested with a level of

significance set at α ≤ 0.05.

A repeated measures ANOVA

was calculated to find the effect of a decline push up on
muscle activation when compared to a standard push up and

15
the effect of an unstable surface on muscle activation
during a decline push up.
Hypothesis 1: There will be a difference in muscle
peak activation between the bench and physioball push ups
compared to the ground push up.
Hypothesis 2: There will not be a difference in muscle
peak activation during the push up off the bench (stable
condition) compared to the push up off the physioball
(unstable condition).
Conclusion:

A repeated measures MANOVA was calculated

examining the effect of peak muscle activity of the
pectoralis major, external oblique, serratus anterior and
lower trapezius during push ups performed on the ground,
off a bench and off a ball (Table 1).

No significant

effect was found between the push ups and peak activation
levels (F (2,38) = .809, P > 0.05) (Table 2).
hypotheses were rejected.

The

16
Table 1. Descriptive Statistics for Maximal Peak Muscle
Activation (%MVIC)

Muscle

Push Up Condition
Ground
Bench
Mean (SD)
Mean (SD)

Ball
Mean (SD)

Pectoralis Major

190 (152.4)

221 (250.6)

202 (163.4)

External Oblique

280 (275.3)

302 (316.6)

288 (251.7)

Serratus Anterior

112

(58.7)

133

(80.6)

132

(81.6)

99

(41.0)

84

(37.0)

89

(31.0)

Lower Trapezius

Table 2. Effect of Peak Muscle Activation During Push Ups

Effect

df

F

Sig.

Condition

2

0.809

0.453

Muscle

3

5.312

0.003

Condition * Muscle

6

0.434

0.855

Additional Findings

Due to the circumstances of finding higher standard
deviations, additional tests were ran to determine if there
were any possible outliers in the data.

The researcher

took the mean of the scores and added two times the
standard deviation to the mean.

This resulted in

eliminating six of the twenty subjects.

A repeated

17
measures MANOVA was calculated with the new data.

There

was not a significant effect found when the outliers were
eliminated (F (2,26) = .762, P > 0.05).

The hypotheses

were still rejected.
Additional peak activation scores among the four
muscles were significant (P = 0.003).

A repeated measures

MANOVA was calculated comparing the peak activation level
between the four muscles: pectoralis major, external
oblique, serratus anterior and lower trapezius.

A

significant effect was found (F (3,57) = 5.312, P = 0.003).
A follow up post-hoc paired t-test showed that scores were
significant between external oblique and serratus anterior,
serratus anterior and lower trapezius, pectoralis major and
lower trapezius, and external oblique and lower trapezius
(Table 3).

Table 3. Significant Differences Between Muscle Pairs
Muscle Pairs

Sig.

Pectoralis Major/External Oblique

0.300

Pectoralis Major/Serratus Anterior

0.097

Pectoralis Major/Lower Trapezius

0.010

External Oblique/Serratus Anterior

0.016

External Oblique/Lower Trapezius

0.003

Serratus Anterior/Lower Trapezius

0.049

18
In addition to the hypothesis testing, the researcher
ran a between-subjects test along with the repeated
measures MANOVA.

Here gender was added as the between-

subjects factor.

There was no significant difference

(F(1,18) = .497, P > 0.05) between the males and females
when compared to the different push up conditions (ground,
bench and ball) as well as the muscles tested.
Another repeated measures MANOVA was run, this time
looking at the overall mean activation scores of the
muscles over the course of the three push ups (Table 4).
The results showed that there was not a significant effect
found
(F (2,38) = 1.910, P > .162) in the overall mean activation
scores during the three different push up conditions
(ground, bench, and ball).

However, the results showed a

significant effect (F (3,57) = 3.976, P = 0.012) between
the four individual muscles: pectoralis major, external
oblique, serratus anterior, and lower trapezius.

A follow

up post-hoc paired t-test showed that scores were
significant between the pectoralis major and lower
trapezius, external oblique and serratus anterior and the
external oblique and lower trapezius.

19

Table 4. Descriptive Statistics for Mean Muscle Activation
(%MVIC)

Muscle

Push Up Variation
Ground
Bench
Mean (SD)
Mean (SD)

Ball
Mean (SD)

Pectoralis Major

101

(78.7)

145 (191.0)

112 (100.8)

External Oblique

175

(201.6)

192 (239.7)

165 (174.9)

Serratus Anterior

68

(46.3)

89

(78.7)

80

(58.0)

Lower Trapezius

63

(30.8)

52

(31.9)

50

(29.4)

20

DISCUSSION

The purpose of this study was to investigate the
difference in muscle activation during a decline push
performed on an unstable surface (physioball) compared to a
stable surface (bench).

The following section is divided

into three subsections: Discussion of Results, Conclusions,
and Recommendations.

Discussion of Results

Upon completion of this study, it was found that there
was not a significant difference in the muscle activation
patterns found when a push up was performed on the ground,
off of a bench or physioball.

The main findings showed

that the type of surface, either stable or unstable, did
not affect the amount of peak muscle activation in the
pectoralis major, external oblique, serratus anterior and
lower trapezius.
These findings were consistent with findings of
previous studies performed by Lehman et al.5,8

Lehman

performed two different studies in which he examined muscle

21
activation during several variations of a push up.

In both

studies the push up was performed with the feet on a bench
and with the feet on a ball as well as other variations.
In the first study, Lehman et al5 looked at the mean muscle
activation of the triceps brachii, pectoralis major, rectus
abdominis and external oblique in healthy male volunteers.
Their results concluded that there was not a significant
difference in any of the previously listed muscles when the
push up was performed with the feet on a bench compared to
when the feet were on a ball.
Lehman’s second study was very similar to the first
study.

Here he looked at the difference in mean muscle

activation between the upper trapezius, lower trapezius,
serratus anterior, and biceps brachii.

Once again, his

results were consistent with the first study in which there
was not a significant difference between the muscle
activation of all the muscles when the push up was
performed with the feet on the bench compared to the feet
on a ball.8 Even though Lehman et al5,8 examined the mean
muscle activation of the muscles involved, his results were
consistent with the results we found with the peak muscle
activation as well as the mean activation.
For this study, we used four muscles previously tested
by Lehman.

The pectoralis major and external oblique were

22
used for Lehman’s first study and the serratus anterior and
lower trapezius were used from his second study.

Our

results supported Lehman’s findings that there is no
significant difference within these four particular muscles
when an unstable surface is used in conjunction with a
decline push up.
Some researchers have also compared the use of a
physioball and a stable surface.

Sandhu et al7 studied the

effects of stable and unstable surfaces placed under the
hands during variations of the push up and push up plus
exercises.

His results were in agreement with this study

in that there was not a significant increase in the
activity of the serratus anterior and upper trapezius.
However, he did find a significant increase in the
pectoralis major and triceps brachii but only during the
eccentric phase of the elbow push ups.

Lehman et al9 looked

at the effects of an unstable surface in trunk muscle
activity while performing six upper extremity strength
exercises.

These results were in agreement with his other

studies and our study in the conclusion that there was not
a significant difference in muscle activity.
Along with investigating the difference between
performing a push up off a bench and off a ball (a stable
compared to an unstable surface), we looked at the muscle

23
activation between a push up performed with the hands and
feet on the ground (standard) with the previously mentioned
push up variations.

There has been limited research done

that has compared the difference between a standard push up
and a decline push up.

Interestingly, one would believe

that if the feet were placed above the level of the head
and hands that there would be more weight placed on the
upper extremity and that the level of muscle activation
would increase due to that level of weight increase.

Due

to this belief, we hypothesized that there would be a
higher level of muscle activation during a decline push up
compared to a standard push up.

However, the results

showed that there was not a significant difference between
the standard push up and the decline push up.
The results showed that the push up performed on the
ground did indeed have the lowest peak and mean muscle
activation levels within the pectoralis major, external
oblique and the serratus anterior when compared to the
other two push up variants.

However, the numbers were not

large enough to be considered significant.

When looking at

the statistics, one can notice that there is a large
variation in muscle activity due to individual differences
between the subjects.

24
From observations made, a possibility as to why there
was a large variation in muscle activity could be due to
the actual form of the push up being performed according to
the particular subjects.

Even though the alignment of the

hands with the acromioclavicular joint was regulated with
each subject, the actual push up form was different.
Several of the subjects’ elbows were not held close to the
body, therefore recruiting other muscles to activate to
help perform the push up.

With a number of subjects, there

seemed to be abnormal tracking of the scapulae.

The

scapulae did not fluently move throughout the entire motion
of the push ups.

This abnormal tracking could have been

caused by the scapulae not being moved fully into the
abducted position, which indicates a weakness in the
serratus anterior.12

Another observation made was that many

of the subjects began to fatigue during the protocol and
began to arch/sag the lower back.

This was seen

particularly during the push up off the bench and off the
physioball.

This arching of the back signifies a weakness

in the core strength.2
Several studies have used the push up exercise in
their testing procedures, either comparing a stable versus
unstable condition or the difference in hand placement.1,5,79,13,14

However, many of these studies used only male

25
subjects.

Due to this gender bias, I was interested in

looking at both genders.

The results showed that there was

no difference between the genders in regards to muscle
activation levels.
When reflecting on the testing procedure, it was noted
that there might have been a reason why other researchers
did not include females in their tests.

The electrode

placement proved difficult due to the muscles being tested.
As it was unethical to test the females completely topless,
they were required to wear a sports bra.

The serratus

anterior electrode was placed directly underneath the
sports bra.

When placing the electrodes, it was difficult

to be precise due to the presence of the sports bra and the
close proximity of the breasts.

The pectoralis major and

lower trapezius sites also provided some difficulty with
the electrodes.

Depending on the cut of the sports bra,

the straps were found to rub against the electrodes and the
leads.

This could have caused interference with the leads

during the EMG readings.
I was also interested to see if the stereotypical
notion that males are better than females when performing
push ups (hence the term for the knee bent push up as girl
push ups) was valid.

After observing all twenty subjects,

there did not appear to be a difference in either gender’s

26
ability to perform the push ups.

Several members of both

genders showed difficulty with the push up protocol.
However, one should remember that during this testing
protocol, the EMG looked at the muscle activation not the
actual strength of the individual muscles.
Another observation noted was the level of difficulty
between the three push up variations.

The ground push up

appeared to be the least difficult, followed by the push up
off the bench, then the push up off the physioball.

A

possible reasoning behind the difference in difficulty is
seen with the biomechanics of the push up.

The push up

exercise can be considered a second-class lever.

This is

where the resistance (gravity) is located between the axis
(feet) and the effort (hands pushing up).2

When the feet

are placed above the level of the head, then a greater
resistance is added to the body.

This will cause the

exercise to become more difficult in nature.

Even though

there was not a significant difference in muscle activation
between the three push up variations, the level of
difficulty should be taken into consideration when deciding
to perform these exercises.
When looking at the results, it is interesting to see
that the level of muscle activation per muscle per
variation was not affected between the three push up

27
variations.

For example, the external oblique showed the

highest level of activation followed by the pectoralis
major, serratus anterior and lastly the lower trapezius.
This concludes that if one wants to activate the external
oblique, it does not matter which push up variation is
performed because they all will activate this particular
muscle.

In contrast, if one wants to activate the lower

trapezius or even the serratus anterior, it is recommended
not to perform these particular types of push ups.
When further investigating the results, one can see
that there is no pattern found proving that one type of
push up variation is superior to another in terms of
activating the individual four muscles.

On the contrary,

if the lower trapezius was eliminated and only the
pectoralis major, external oblique and serratus anterior
muscles were observed then there appears to be a trend
throughout the push up variations.

The push up on the

ground presented the lowest peak muscle activation levels,
followed by the push up off the ball, then the push up off
the bench.

28
Conclusions

This study resulted in no difference found in peak
muscle activation of the pectoralis major, external
oblique, serratus anterior and lower trapezius when
performing a push up on the ground, with feet on a bench or
with the feet on a physioball.

Further, no difference in

the mean muscle activation between the previously mentioned
muscles and push up variations was reported.

Additionally,

gender does not appear to have an effect on muscle
activation during the different push up variations.

Trends

were found showing that during these three particular push
up variations, the external oblique produced the highest
activation levels followed by the pectoralis major,
serratus anterior and lastly the lower trapezius.

Recommendations

To further advance the study just completed, I would
have the subjects perform the protocol several times.
would provide the researcher with more data.

This

Also, during

this time, the correct push up form would be strictly
enforced and be made uniform throughout the subjects.

If

one subject showed a hint of muscle weakness then he or she

29
would be disqualified from the study.

In addition, the

length of time each push up took would be decreased to help
minimize the possible chance of fatigue.

This way the

variability between push up forms would be decreased,
providing more valid results.

I would also recruit more

subjects, both males and females.
This study required the subjects to have previous
experience using a physioball.

It would be interesting to

recruit subjects who had never used a physioball and have
them perform the push up protocol.

Afterwards, they could

be taught the proper form in regards to bracing the core
musculature, practice the proper form and then repeat the
testing protocol.

This could help determine if there would

be a learning effect present that could affect the level of
muscle activation of the core muscles.
Due to the lack of research comparing the standard
(ground) push up to the decline push up, further research
should be done in this area.

I would suggest adding a

force platform in addition to the use of the EMG.

This way

the researcher could determine if there is a greater force
placed on the upper extremity during the decline push up.
While using the force platform, the researcher could
examine if there is a greater force placed upon on one hand
compared to the other while the subject is performing the

30
push up off the physioball (unstable surface).

To go into

further detail, the researcher could observe the activation
of the muscles bilaterally and see if there is a greater
level of muscle activation if/when the weight is shifted
from side to side due to the instability factor.
The results from this study should be taken into
consideration when selecting exercises for a rehabilitation
or workout program.

The use of an unstable surface

(physioball) shows no effect on the levels of peak or mean
muscle activation levels.

However, the level of difficulty

of the push up exercise is seen to increase when this
unstable surface is incorporated.

Therefore, the use of an

unstable surface is beneficial at least for proprioception
exercises to increase the ability to balance.

Athletic

trainers and physical therapists should also note that this
study only looked at four particular muscles; pectoralis
major, external oblique, serratus anterior and lower
trapezius.

It is possible that the use of an unstable

surface does affect muscle activation levels of muscles not
previously mentioned or tested in other studies.

31
REFERENCES

1. Gouvali MK, Boudolos K. Dynamic and electromyographical
analysis in variants of push-up exercise. J Strength Cond
Res. 2005;19:146-151.
2. Hamilton N, Weimar W, Luttgens K. Kinesiology: Scientific
Basis of Human Motion; eleventh edition. New York: McGrawHill Companies; 2008.
3. Cogley RM, Archambault TA, Fiberger JF, Koverman MM, Youdas
JW, Hollman JH. Comparison of muscle activation using
various hand positions during the push-up exercise. J
Strength Cond Res. 2005;19:628-633.
4. Freeman S, Karpowicz A, Gray J, McGill S. Quantifying
muscle patterns and spine load during various forms of the
push-up. Med Sci Sports Exerc. 2006;38:570–577.
5. Lehman GJ, MacMillan B, MacIntyre I, Chivers M, Fluter M.
Shoulder muscle EMG activity during push up variations on
and off a swiss ball. Dyn Med. 2006;7.
6. Marshall P, Murphy B. Changes in muscle activity and
perceived exertion during exercises performed on a swiss
ball. Appl Physiol Nutr Metab. 2006;31:376-383.
7. Sandhu JS, Mahajan S, Shenoy S. An electromyographic
analysis of shoulder muscle activation during push-up
variations on stable and labile surfaces. Int J Shoulder
Surg. 2008;2:30-35.
8. Lehman GJ, Gilas D, Patel U. An unstable support surface
does not increase scapulothoracic stabilizing muscle
activity during push up and push up plus exercises. Man
Ther. 2008;13:500-506.
9. Lehman GJ, Gordon T, Langley J, Pemrose P, Tregaskis S.
Replacing a swiss ball for an exercise bench causes
variable changes in trunk muscle activity during upper limb
strength exercises. Dyn Med. 2005;6.

32
10. Haskell WL, Lee I, Pate RR, et al. Physical activity and
public health: updated recommendation for adults from the
american college of sports medicine and the american heart
association. Med Sci Sport Exer. 2007;1423-1434.
11. Clark MA, Lucett SC. NASM’s Essentials of Sports
Performance Training. Philadelphia: Lippincott Williams &
Wilkins; 2010.
12. Kendall FP, McCreary EK, Provance PG, Rodgers MM, Romani
WA. Muscles Testing and Function with Posture and Pain.
Philadelphia: Lippincott Williams & Wilkins; 2005.
13. Martins J, Tucci HT, Andrade R, Araujo RC, Bevilaqua-Grossi
D, Oliveira AS. Electromyographic amplitude ratio of
serratus anterior and upper trapezius muscles during
modified push-ups and bench press exercises. J Strength
Cond Res. 2008;22:477-484.
14. Tucker WS, Gilbert ML, Gribble PA, Campbell BM. Effects of
hand placement on scapular muscle activation during the
push-up plus exercise. Athletic Training & Sports Health
Care. 2009;1:107-113.

33

APPENDICES

34

APPENDIX A
Review of Literature

35

REVIEW OF LITERATURE

A common exercise performed by many people is the
push-up.

There are many variations in which this simple

exercise can be performed depending on the desired
outcomes.

These can range from varying hand placements to

adding a piece of equipment under the feet and/or hands.
However, do these different push-up variations actually
change the amount of muscle activation to justify
performing the different push up variants?

The purpose of

this literature review will be to examine the anatomy of
the shoulder, muscle activation and how to measure
activity, the differences of various hand placements and
their respective effects on the musculature when performing
a decline push up, and the use of stable and unstable
surfaces.

Shoulder Anatomy

The shoulder is known for being one of the most
complex joints in the human body.

It is very mobile but

due to the shoulder’s increased level of mobility there is
a decrease in the level of stability.

The bony make up of

36
the shoulder is responsible for these two critical levels
of mobility and stability.
The shoulder is made up of two separate anatomical
structures which are the shoulder girdle and the actual
shoulder joint.

The shoulder girdle consists of the

scapula and clavicle, whereas the true shoulder joint is
the articulation between the scapula and the head of the
humerus.1

The head of the humerus fits into the glenoid

fossa of the scapula, hence the name the glenohumeral
joint.
The glenohumeral joint is one of several joints
associated with the shoulder.

In addition, there is the

acromioclavicular joint made up of the acromion process and
the lateral end of the clavicle.
the sternoclavicular joint.

A third joint would be

This is an articulation

between the clavicular notch of the sternum and the medial
end of the clavicle.

The sternoclavicular joint is the

only direct attachment between the upper extremity and the
trunk.

The last joint relating to the shoulder is the

scapulothoracic joint.
scapula and the thorax.

This is an articulation between the
However, this last joint is

considered a false joint because there is no bone to bone
contact.1

37
Nevertheless, the scapulothoracic joint plays an
important role along with the glenohumeral joint to provide
the large amount of mobility seen within the shoulder.
There are two main muscle groups that are responsible for
all the mobility; the scapulohumeral and scapulothoracic.
The scapulohumeral muscles include the coracobrachialis,
deltoid, teres major, supraspinatus, infraspinatus,
subscapularis and the teres minor.

These muscles all

originate on the scapula and attach on the humerus.2,3

This

group of muscles help dynamically stabilize the
glenohumeral joint by assisting in minimizing the
translation of the humeral head against the glenoid fossa.
The movements caused by this muscle group include flexion,
extension, internal rotation, external rotation, abduction,
adduction and circumduction.2
The scapulothoracic muscle group is responsible for
providing stability to the glenoid fossa while the humerus
is in motion.

The muscles included in this group are the

trapezius (upper, middle and lower), rhomboids (major and
minor), pectoralis minor and the serratus anterior.

Once

again these muscles are named due to their origin on the
thorax and their insertion on the scapula.

The movements

associated with these muscles are elevation, upward
rotation, downward rotation, and adduction of the

38
scapula.1,2 All of the previously mentioned muscles are very
important in the mobility and stability of the shoulder.
However, even if one muscle is not firing correctly, the
whole series of motion of the shoulder can be affected.

Muscle Function

Each muscle in the body is made up of muscle cells
that are often called muscle fibers.

A muscle fiber is

collectively made up of thousands of myofibrils.

The

myofibrils contain the actual structures that contract the
muscle cell, which are known as the myofilaments, actin and
myosin.

The actin and myosin are arranged parallel to the

muscle fiber.

The myofilaments overlap one another which,

due to their respective sizes, gives the muscle fiber the
striated appearance.
When a muscle fiber contracts, the myofilaments pull
towards what is called the Z-line of the myofibril.

A Z-

line is where the actin filaments attach to the sarcomere.
The actin filaments slide over the myosin filaments
therefore causing the contraction.

Due to the minute size

of the myofilaments, hundreds of thousands of these Z-lines
are found in one muscle fiber.4

39
Each muscle fiber is innervated by motor neurons that
carry a signal from the spinal cord to the muscle.

The

motor neuron and all of its muscle fibers are collectively
known as a motor unit.

Each muscle has a different number

of motor units, depending on the precision of the muscle’s
movement.

For example, muscles of the fingers will have a

larger number of motor units than the muscles of the
quadriceps.1
The motor neuron is also responsible for sending an
electrical current to the muscle fiber in order for
contractions to occur.

The motor neuron innervates the

muscle fibers by a chemical transmission.

A chemical

called acetylcholine is released, which causes excitation
of the sarcolemma.

Once this chemical is released, an

action potential is generated and a contraction occurs
within the fiber.4

The action potential is also very

important because this is how muscle activation is
measured.

Measuring Muscle Activation

There are two methods by which muscle activation can
be measured. The first method is called muscle
mechanomyography or MMG.

This method is a non-invasive

40
technique that records and quantifies contracting muscle
fibers.

MMG can be used to assess a variety of areas such

as muscle pain, muscle fatigue, firing patterns, delayedonset muscle soreness and neuromuscular disease.5
A second method of measuring muscle activation is
called electromyography or EMG.

This technique is

typically used to assess the initiation of muscle
activation and the level of fatigue occurring within a
muscle.

EMGs are also used as a way to differentiate

various forms of muscle contractions; isometric, eccentric
and concentric.5
These two methods can be used together in detecting
muscle activation.

MMG is used to measure the mechanical

aspect of muscle contractions whereas EMG is used to
measure the electrical component.

However, the use of EMG

is more common within the clinical setting because it has
been around longer and more clinicians are familiar with
using this method.

Electromyography
The main concept of the EMG is to measure the
electrical impulses given off by muscles when they are
contracting or at rest.

EMGs record the action potentials

as they are generated by chemical releases in the muscle

41
fibers.6

One great contribution that EMGs have given is

that they are able to record the impulses of both deep and
superficial muscles.
Surface electromyography (SEMG) is most commonly used
in biomechanical studies because it has a non-invasive
nature.

It uses surface electrodes to detect the

myoelectric signal given off from the muscles.

However,

the drawback of this type of SEMG is that it can only be
used for superficial muscles.7
EMGs play a large role in the world of biomechanics.
They can be used to measure and analyze the coordination
and function in almost any type of physical performance.
EMGs function varies from studying different types of
muscle contraction, evaluating functional muscle activity,
to fatigue studies and the influence of equipment on muscle
activity.
The most important aspect of electromyography is that
it reports if a muscle is active or not.

From there, one

can tell if a certain muscle is firing more or less than
other muscles, how active that muscle is and if that muscle
fatigues at one point in time.7

42
Techniques of the Push Up

The push up is an exercise that has a variety of uses.
Due to its easy execution, no equipment requirement, and
adaptability, the push up has become a very popular
exercise.8

It can be used as part of a strengthening

program, a tool to measure strength and endurance of the
upper extremity or even as part of a rehabilitation
protocol.8-11
The push up is considered a closed-kinetic chain
exercise where the hands are fixated on an object and the
body weight is placed directly on the hands.

As a result,

the pectoralis major and triceps brachii are the primary
action muscles.

Therefore, when performing a push up, one

can increase the level of strength of these two muscles.
As an assessment tool, the push up has been incorporated in
multiple fitness tests such as the Army Physical Fitness
Test and the FITNESSGRAM.9,10,11

In the clinical setting, the

push up is seen as an example of a closed kinetic chain
exercise and a plyometric exercise when rehabilitating the
shoulder.2

Some observations even show that when performing

a push up, pain is relieved in patients with chronic back
pain.12

Whether the push up is used as a strengthening or

43
an assessment tool, it is important to learn the different
forms in which a push up can be performed.
Researchers have looked at multiple variants of the
push up and recorded the results of the various positions.
The standard push up is described to be when the hand
placement is normalized to the distance between a person’s
acromion process or the middle phalanx is aligned with the
acromion process.13 The hands are placed flat on the ground
while the toes are also on the ground.

The arms are to be

perpendicular to the floor.
As for the action of the exercise itself, the body is
kept in a straight line and the arms are flexed at the
elbow joints and eccentrically lowered to the floor until
the chest nearly touches the floor.

The body is then

returned to the starting position by pushing the hands
forcefully against the ground.

The force of motion during

the eccentric phase is gravity where the muscles are the
force during the concentric phase.6
When looking at the anatomical analysis of a push up,
the exercise is broken down into two phases, the eccentric
or dip phase and the concentric or up phase.

During the

dip phase the main actions are horizontal abduction
(shoulder), adduction (shoulder girdle), flexion (elbows)
and reduction of hyperextension (wrists).

For the up phase

44
the actions are the opposite; horizontal adduction
(shoulder), abduction (shoulder girdle), extension
(elbows), and hyperextension (wrists).

The primary muscles

that are active during these movements are the pectoralis
major, anterior deltoid, pectoralis minor, serratus
anterior, triceps and extensor carpi radialis and ulnaris.
Also, when performing a push up one must maintain a
straight line from the head to the heels.

In order for

this to happen, the cervical extensors, rectus abdominus,
obliques and hip flexors must be statically contracted
throughout both phases.6
A common push up variant is the bent knee push up.
Instead of having the hands and toes on the ground, the
knees are bent and resting on the floor.

This variant is

usually performed when a person is not able to perform a
full body push up due to a lack of upper body strength.
The bent knee push up is commonly seen in fitness tests
such as the Presidents’ Challenge and FITNESSGRAM.10 A
second push up variant also seen in these fitness tests is
the ninety degree push up.

This is where the hands and

toes are on the ground and the subject lowers his or her
body until the elbows are bent to a ninety degree angle and
then returns to the starting position.10

45
Other push up variants have been studied in accordance
with muscle activation patterns.

Cogley et al9 examined the

difference in muscle activation of the triceps brachii and
pectoralis major while the hands were placed in three
different positions: shoulder width base, wide base and
narrow base.

For the shoulder width hand position, the

subjects’ middle finger was aligned with the edge of the
deltoid via plumb line.

The wide base position was

measured by twenty centimeters laterally from their
shoulder width position.

Lastly, the narrow based position

was characterized by placing the hands together, making a
diamond shape between the first and second digits.

The

results of this study showed a significant difference in
muscle activation of the triceps brachii and pectoralis
major during the narrow base hand position compared to the
shoulder width and wide base positions.
Gouvali and Boudolos8 performed a study that was
similar to Cogley et al9.

They looked at six different push

up variants: normal position, wide position (150 % of
shoulder width), narrow position (50% of shoulder width),
anterior position, posterior position and bent knee.

For

the anterior position, the subjects’ hands were placed 30%
of their arm length anteriorly compared to the normal
positioning.

The same was done for the posterior position,

46
the hands were placed 30% posteriorly so that the hands
were located under the subjects’ rib cage.

The muscles

studied were once again the triceps brachii and pectoralis
major.

The results showed that the bent knee push up was

the least demanding of overall muscle activation and that
only during the posterior position, the pectoralis major
was activated to a greater extent compared to the other
positions.
When looking at the push up variants, there is one
called the push up plus.

This is when the standard push up

is performed then followed by scapular protraction then
retraction returning the body to the starting position.
This variant is used when wanting to activate the scapular
stabilizers.13 Tucker et al13 performed a study looking at
the different hand placements on the muscle activation of
the serratus anterior, middle trapezius, and lower
trapezius during the push up plus exercise.

The hand

placements were normal (48 cm apart), wide (70.5 cm apart)
and narrow (25.5 cm apart).

The results concluded that the

muscle activation of serratus anterior was significantly
greater in the wide hand placement, the lower trapezius
muscle activity was greater in the narrow hand placement
and there was no difference regarding hand placement for
the middle trapezius.

47
Other variations seen are the: 1) single arm push up;
2) uneven hand placement, where one hand is placed three
inches in front and the other hand is three inches behind
the normal position; 3) push up with a clap, the subject
forcefully contracts during the concentric phase, allowing
the body to elevate off the ground and then the subject
claps before catching the body on the hands once again; 4)
one hand on a ball and the other hand on the ground; 5)
depth push up, where the subject’s hands are placed on an
object that elevates the hands allowing the body to perform
a deeper push up, and 6) the decline push up, where the
feet are placed on an object so that the feet are elevated
above the subject’s head, producing a declined angle.12
A final push up variant is that of incorporating an
unstable surface.

One of the most common is adding a

stability ball to the standard push up.

One can either

place the feet on the ball or the hands on the ball.

Other

unstable surfaces can include foam pads, BOSU balls, Dyna
discs, wobble boards and mini trampolines.

48
Stability Balls

The stability ball was developed in 1963 by Aquilino
Cosani.

They were first used during rehabilitation of

children suffering from neurological impairments.

The

rehabilitation techniques were then passed on to physical
therapists dealing with children with cerebral palsy and
eventually to treat patients with back pain.14

Now the use

of stability balls can be seen in physical therapy and
strength and conditioning.
The use of an unstable surface is thought to put a
higher demand on the neuromuscular system, therefore
causing the small stabilizing muscles to activate at a
greater rate.15 Other assumptions are that an unstable
surface increases the demands of the propriceptors during
balancing, which in turn leads to a reduction in
injuries.14,16

Cassady et al17 found the use of a stability

ball can increase oxygen consumption during exercise.
However, another study by Stanton, Reaburn, and Humphries18
shows there is no improvement in VO2 max or running economy
when subjects were to perform a six week exercise program
involving exercises on a stability ball.
The use of a stability ball can be seen as a variant
for many exercises.

The most popular exercises are ones

49
that relate to the core musculature.

Escamilla et al19

performed a study that investigated the level of muscle
activation during swiss ball exercises compared to
traditional core exercises.

Subjects were to perform eight

swiss ball exercises and two traditional abdominal
exercises.

EMG data was collected and used to compare the

level of muscle activation of five abdominal and back
muscles.

Results concluded that the use of a swiss ball

increases the muscle activation in some exercises but not
all compared to the traditional exercises.
Similarly, Marshall and Murphy20 conducted a study
looking at three different exercises, both with a stable
and unstable surface (a stability ball).

The three

exercises that were performed were a double leg hold, push
up and wall squat.

For the double leg hold, the subjects

were to lower their legs from 90 degrees of hip flexion to
just parallel with their trunk, and hold that position for
three seconds.

The subjects performed this exercise lying

supine on a bench and then repeated on a ball.

The

subjects performed standard push ups with their hands
placed on a stable surface and then on a ball.

For the

squat, the subjects performed a squat with their backs
against a wall and then repeated the test with a ball
between them and the wall. The results of this study showed

50
that there was no difference in the two squat exercises.
During the push up, greater muscle activation was seen in
the transverse abdominis/internal oblique, rectus
abdominis, and in the triceps brachii.

As for the double

leg hold, only the rectus abdominis showed a significant
difference in muscle activity.
Several authors took the growing popularity of the
stability ball and combined it with the already popular
push up exercise.

Here they tested the common belief that

adding an unstable component to an exercise will increase
the muscle activation of the muscles involved.

Push ups on a Stability Ball

The push up is known to be a very adaptable exercise.
By adding a common piece of equipment, the push up can be
altered slightly producing different results compared to
the standard push up.

Several studies have been conducted

to measure this muscle activation during push ups on and
off a stability ball.

Sandu, Mahajan and Shenoy21 had

subjects perform four push up variations on a stable
surface and a stability ball.

For each exercise, the hands

were placed on the ball while the feet or knees were on the
ground.

During these exercises, the pectoralis major,

51
upper trapezius, serratus anterior, and tricpes brachii
were connected to an EMG machine.

The results concluded

that only the pectoralis major showed a significant
difference in muscle activation.
Lehman, Gilas and Patel16 conducted a study looking at
an unstable surface and its effect on scapulothoracic
stabilizing muscles.

Subjects performed three different

variants of the push up once again replacing a stable
surface (bench) with an unstable surface (ball).

The three

exercises were: push up with hands on bench/ball with feet
on ground, push up with feet on bench/ball with hands on
ground, and push up plus with hands on bench/ball.

The

muscles involved in the study were the upper trapezius,
lower trapezius, biceps brachii and serratus anterior.
Results showed no significant difference in muscle activity
for all four muscles.
Lehman et al15 also performed a very similar study
where they observed the triceps brachii, pectoralis major,
rectus abdominis and external oblique during the three push
up variations mentioned in the previous study.

The triceps

brachii and the rectus abdominis showed a significant
difference when the stability ball was added to the hands
replacing the bench.

The pectoralis major and external

52
oblique were not influenced by the replacement of the ball
compared to the bench.
As these studies have shown, muscle activity can be
affected by varying the hand placement during the push up
exercise.

However, the literature found does not

specifically support that the use of an unstable surface
will increase muscle activity.

Summary

The literature depicts that the shoulder complex is
made up of a multitude of muscles that have a large amount
of responsibility regarding movement and stability.

In

order for the muscles to function the way that they do,
signals from the central nervous system must be sent out to
initiate the contractile tissues within the muscle fibers.
In order for one to determine if the muscles are firing,
electromyography machines are used to measure the signal
given off from the muscles.

The push up is a common

exercise in which to activate and strengthen the muscles of
the upper body.
popular exercise.

There are many ways to execute this

stability ball.

One way is to perform the push up off a
When an unstable factor is added to an

exercise, the assumption is that it puts a greater demand

53
on the neuromuscular system, in turn creating greater
muscle activation.

More evidence is needed to determine if

these claims are in fact true when instability is added to
a basic exercise.

54

APPENDIX B
The Problem

55
THE PROBLEM

Statement of the Problem
The push up is a common and widely used exercise to
strengthen the upper body. It can also be used to measure
strength and muscle endurance of the arms and shoulders.
The push up traditionally is performed with the feet and
hands on the floor but it can also be performed on an
unstable surface.

The common belief is that this will help

increase the level of muscle activation levels during the
exercise.
The purpose of this study is to test the claims that
the use of an unstable surface helps activate more motor
units while performing traditional exercises.

This study

will investigate if these claims are in fact true while
performing the push up combined with an unstable surface.
It would be beneficial for the physically active and
injured population to know if the use of an unstable
surface via a physioball actually increases the
effectiveness of general exercises.

Definition of Terms
The following terms were operationally defined for
this study:

56

1)

Physioball – Large inflatable ball made out of plastic
that come in varying sizes.

Also known as exercise

balls, stability balls, Swiss balls, or fit balls.
2)

EMG – Electromyography.

A technique used to measure

and record the electrical activity of muscles.
3)

Muscle Activation - The level of recruitment of muscle
as sent via the afferent nerve pathway from the brain
measured by EMG.

Basic Assumptions
The following were basic assumptions of this study:
1)

The equipment will work correctly and will be properly
calibrated.

2)

The subjects will perform to the best of their ability
during the experiment.

3)

The subjects will answer truthfully on the preparticipation questionnaire.

Limitations of the Study
The following were possible limitations of the study:
1)

The equipment may not have been sensitive enough to
accurately detect the muscle activation levels.

57
2)

The participants were limited to college students at
California University of Pennsylvania.

3)

Subjects had varying experience with proper push up
form.

Delimitations of the Study
The following were the delimitations of the study:
1)

Experience performing push ups.

2)

Physically active individuals enrolled at California
University of Pennsylvania.

3)

Experience using a physioball.

4)

The bench and physioball stood at the same height.
The physioball was measured before each testing
session.

Significance of the Study
The push up is a popular exercise to strengthen the
upper body as well as test muscle endurance of the shoulder
girdle.

The stability ball is used to add instability to a

basic exercise in hopes of recruiting more muscle units and
increasing muscle firing.

This study will investigate if

there is a difference in muscle activation levels when a
push up is performed at a declined angle (with feet on a
bench) compared to a standard push up.

It will also

58
investigate if the use of a physioball ball during a
decline push up will indeed increase the level of muscle
activation than the decline push up alone.

If it finds

that the presence of an unstable surface is beneficial in
activating the muscles then one can transform traditional
exercises easily by adding an unstable factor.

59

APPENDIX C
Additional Methods

60

APPENDIX C1
Informed Consent Form

61

Informed Consent Form
1. Kelsey Todd, who is a Graduate Athletic Training Student at California University of
Pennsylvania, has requested my participation in a research study at California University
of Pennsylvania. The title of the research is “Muscle Activation During a Decline Push
Up on an Unstable Surface”.
2. I have been informed that the purpose of this study is to test the claims that the use of
an unstable surface helps activate more motor units while performing traditional
exercises. I understand that I must be 18 years of age or older to participate. If I am under
18 years of age, I will be eliminated from the study. I understand that I have been asked
to participate along with 19 other individuals because I do not have a history of shoulder,
elbow and/or wrist injury within the previous six months. I also have previous
experience performing push ups. I also understand and agree that it is required that I
perform these tests without a shirt or in a sports bra, if I am a female, due to electrode
placement and interference with the leads.
3. I have been invited to participate in this research project. My participation is voluntary
and I can choose to discontinue my participation at any time without penalty or loss of
benefits. My participation will involve an informational meeting and a maximum
voluntary contraction testing session followed by the testing protocol. For the testing
protocol, I will be required to perform a set of three decline push ups off a bench, a
second set of three decline push ups off a stability ball and a third set of standard push
ups on the ground. There will be a minimum of three minutes between each set of push
ups.
4. I understand there are foreseeable risks or discomforts to me if I agree to participate in
the study. With participation in a research program such as this there is always the
potential for unforeseeable risks as well. The possible risk and/or discomforts could
include having my feet fall from the ball or bench due to instability or general weakness.
To minimize these risks, I will be instructed to stop if I feel I can no longer perform the
push ups. Also, the research assistant will assist me by placing my feet on the ball and/or
bench. I also understand that it is required to perform this study without a shirt, due to
electrode placement and the interference of the leads with clothing.
5. I understand that, in case of injury, I can expect to receive treatment or care in Hamer
Hall’s Athletic Training Facility. This treatment will be provided by the researcher,
Kelsey Todd, under the supervision of the CalU athletic training faculty, all of which can
administer emergency care. Additional services needed for prolonged care will be
referred to the attending staff at the Downey Garofola Health Services located on
campus.

62
6. There are no feasible alternative procedures available for this study.
7. I understand that the possible benefit of my participation in the research is to help
determine the effects of an unstable surface on muscle activation during a decline push
up. This study can help athletic trainers and other clinicians decide whether or not it is
beneficial to use an instability factor during exercise.
8. I understand that the results of the research study may be published but my name or
identity will not be revealed. Only aggregate data will be reported. In order to maintain
confidentially of my records, Kelsey Todd will maintain all documents in a secure
location on campus and password protect all electronic files so that only the student
researcher and research advisor can access the data. Each subject will be given a specific
subject number to represent his or her name so as to protect the anonymity of each
subject.
9. I have been informed that I will not be compensated for my participation.
10. I have been informed that any questions I have concerning the research study or my
participation in it, before or after my consent, will be answered by:
Kelsey Todd, ATC
Student/Primary Researcher
Tod8725@calu.edu
(330) 692-2854
Edwin Zuchelkowski, PhD
RESEARCH ADVISOR
Zuchelkowski@calu.edu
(724) 938-4202
11. I understand that written responses may be used in quotations for publication but my
identity will remain anonymous.
12. I have read the above information and am electing to participate in this study. The
nature, demands, risks, and benefits of the project have been explained to me. I
knowingly assume the risks involved, and understand that I may withdraw my consent
and discontinue participation at any time without penalty or loss of benefit to myself. In
signing this consent form, I am not waiving any legal claims, rights, or remedies. A copy
of this consent form will be given to me upon request.
13. This study has been approved by the California University of Pennsylvania
Institutional Review Board.
14. The IRB approval dates for this project are from: 03/14/11 to 03/13/12.

63
Subject's signature:___________________________________
Date:____________________
Witness signature:___________________________________
Date:____________________

64

APPENDIX C2
Demographic Information Sheet

65
Demographic Information
Subjects Number __________
Gender:
____
Age:

Male

____ Female

_____

Do you currently take part in physical activity? If so, how
often?

Are you part of an organized sport?

Have you ever performed a push up?

If you answered yes to the previous question, how often do
you perform push ups?
_____ Daily
_____ Several times a week
_____ Several times a month
_____ Occasionally throughout the year
Have you ever performed an exercise on a stability ball?

Have you had an injury to the upper extremity (shoulder,
elbow or wrist) that has prevented you to from working out
within the previous six months? If yes, please explain.

66

Appendix C3
Institutional Review Board –
California University of Pennsylvania

67

68

69

70

71

72

73

74

75

76

77

Ms. Todd
Please consider this email as official notification that your proposal titled
“Muscle Activation During a Decline Push Up on an Unstable Surface”
(Proposal #10-028) has been approved by the California University of
Pennsylvania Institutional Review Board as amended.
The effective date of the approval is 03-14-2011 and the expiration date is
03-13-2012. These dates must appear on the consent form.
Please note that Federal Policy requires that you notify the IRB promptly
regarding any of the following:
(1) Any additions or changes in procedures you might wish for your
study (additions or changes must be approved by the IRB before
they are implemented)
(2) Any events that affect the safety or well-being of subjects
(3) Any modifications of your study or other responses that are
necessitated by any events reported in (2).
(4) To continue your research beyond the approval expiration date of
03-13-2012 you must file additional information to be considered
for continuing review. Please contact instreviewboard@calu.edu
Please notify the Board when data collection is complete.
Regards,
Robert Skwarecki, Ph.D., CCC-SLP
Chair, Institutional Review Board

78

Appendix C4
Sample Individual Data Collection Sheet

79

Sample Individual Data Collection Sheet
Subject # ______
Gender ______
MVC
Pec major

______

______

______

Ex Oblique

______

______

______

Serratus Ant

______

______

______

Low Trap

______

______

______

Push Up – Standard

Push Up – Bench

Push Up – Ball

Max

Mean

PM

______

______

EO

______

______

SA

______

______

LT

______

______

PM

______

______

EO

______

______

SA

______

______

LT

______

______

PM

______

______

EO

______

______

SA

______

______

LT

______

______

80
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Behnke RS. Kinetic
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Prentice
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Manske RC. Electromyographically assessed exercises for
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4.

Baechle TR, Earle RW. Essentials of Strength Training and
Conditioning; 2nd ed. Champaign: Human Kinetics; 2000.

5.

Kawczynski A, Nie H, Jaskolska A, Jaskoski A, ArendtNielsen L, Madeleine P. Mechanomyography and
electromyography during and after fatiguing shoulder
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6.

Hamilton N, Weimar W, Luttgens K. Kinesiology: Scientific
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7.

Gratiela-Flavia D, Flavia R, Emilia G. Surface
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8.

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9.

Cogley RM, Archambault TA, Fiberger JF, Koverman MM,
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Wood HM, Baumgartner TA. Objectivity, reliability, and
validity of the bent-knee push-up for college-age women.
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Mozumdar A, Liguori G, Baumgartner TA. Additional revised
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Exerc Sci. 2010;14:61–66.

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the push-up. Med Sci Sports Exerc. 2006;38:570–577.

13.

Tucker WS, Gilbert ML, Gribble PA, Campbell BM. Effects
of hand placement on scapular muscle activation during
the push-up plus exercise. Athletic Training & Sports
Health Care. 2009;1:107-113.

14.

Jakubek MD. Stability balls: reviewing the literature
regarding their use and effectiveness. J Strength Cond
Res. 2007;29:58-63.

15.

Lehman GJ, MacMillan B, MacIntyre I, Chivers M, Fluter M.
Shoulder muscle EMG activity during push up variations on
and off a swiss ball. Dyn Med. 2006;7.

16.

Lehman GJ, Gilas D, Patel U. An unstable support surface
does not increase scapulothoracic stabilizing muscle
activity during push up and push up plus exercises. Man
Ther. 2008;13:500-506.

17.

Cassady SL, Leven M, DeBrower A, Esters J, Kruse B,
Miller A. Cardiorespiratory responses to abdominal
stabilization exercises performed on a therapeutic
exercise ball. Cardiopulm Phys Ther J. 2001;12:83-87

18.

Stanton R, Reaburn PR, Humphries B. The effect of shortterm swiss ball training on core stability and running
economy. J Strength Cond Res. 2004;18:522-528.

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Escamillia RF, Lewis C, Bell D, Brambelt G, Daffron J,
Lambert S, Pecson A, Imamura R, Paulos L, Andrews JR.
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82

ABSTRACT
Title:

MUSCLE ACTIVATION DURING A DECLINE PUSH UPON
AN UNSTABLE SURFACE

Researcher:

Kelsey Todd

Advisor:

Dr. Edwin Zuchelkowski

Date:

May 2011

Research Type: Master’s Thesis
Purpose:

To investigate the peak muscle activation
levels of the pectoralis major, external
oblique, serratus anterior, and lower
trapezius during a standard push up, a
decline push up on a stable surface and a
decline push up on an unstable surface.

Problem:

The push up is a common and widely used
exercise to strengthen the upper body. It
can also be used to measure the strength and
muscle endurance of the arms and shoulders.
The push up is traditionally performed with
the hands and feet on the floor but it can
also be performed on an unstable surface.
The common belief is that this will help
increase the level of muscle activation
levels during the exercise.

Method:

This study looked at twenty physically
active individuals recruited from the
general population. Testing took one day to
complete for each subject. During the
testing session, surface electromyography
was taken of the pectoralis major, external
oblique, serratus anterior and lower
trapezius. The subjects were randomly
assigned to perform three sets of three push
ups. One set was performed on the ground,
another set was performed with the feet
placed on a bench and the third set was
performed with the feet placed on a
physioball. There was a minimum of a three
minute break between sets. Peak muscle

83
activation measurements were collected and
analyzed.
Findings:

The data was analyzed by using a repeated
measures MANOVA. There was no significant
difference found with the peak muscle
activity between the three push up
variations. There was also no significant
difference found between mean muscle
activity and gender. There were trends
found showing that the external oblique’s
activation levels were the highest followed
by the pectoralis major, serratus anterior
and lower trapezius.

Conclusion:

When trying to establish a higher level of
muscle activation of the pectoralis major,
external oblique, serratus anterior or
lower trapezius, there is no difference in
performing a push up off the ground, with
the feet on a bench or with the feet on a
physioball.