ELECTROMYOGRAPIC ACTIVITY IN CORE MUSCLES DURING STATIC
YOGA POSES PERFORMED ON STABLE AND UNSTABLE SURFACES

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
Elizabeth Banks

Research Advisor, Dr. Thomas F. West
California, Pennsylvania
2011

ii

iii

ACKNOWLEDGEMENTS
I would like to acknowledge the Lord God for producing
the strength to keep my head up and keep moving forward. He
was the source of strength and motivation that keep me
going when I wanted to give.
I would also like to extend a special thanks to Dr.
Thomas West, who was the Chairperson responsible for
assisting me in the writing of my thesis. His mentoring was
instrumental in completion of this overwhelming project. In
addition, I would like to acknowledge Dr. Ayanna Lyles and
Assistant Professor Popovich for their time and dedication
to the completion of my thesis.
I would also like to thank Ms. Carolyn, the Health
Science Department Secretary, who was always there to lend
a helping hand and provide support during difficult times.
As for my parents, they have always been by my side to
encourage me every step of the way. It is with much
gratitude that I have made them proud with my educational
accomplishments.

iv
TABLE OF CONTENTS

Page
SIGNATURE PAGE

. . . . . . . . . . . . . . . . i

AKNOWLEDGEMENTS . . . . . . . . . . . . . . . . ii
TABLE OF CONTENTS
INTRODUCTION
METHODS

. . . . . . . . . . . . . . . iii

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

. . . . . . . . . . . . . . . . . . . 8

Research Design
Subjects

. . . . . . . . . . . . . . . 8

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

Preliminary Research

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

Instruments . . . . . . . . . . . . . . . . . 14
Procedures

. . . . . . . . . . . . . . . . . 15

Hypotheses

. . . . . . . . . . . . . . . . . 19

Data Analysis
RESULTS

. . . . . . . . . . . . . . . . 20

. . . . . . . . . . . . . . . . . . . 21

Demographic Data . . . . . . . . . . . . . . . 21
Hypotheses Testing

. . . . . . . . . . . . . . 22

DISCUSSION . . . . . . . . . . . . . . . . . . 26
Discussions of Results . . . . . . . . . . . . . 26
Conclusions . . . . . . . . . . . . . . . . . 32
Recommendations

. . . . . . . . . . . . . . . 33

REFERENCES . . . . . . . . . . . . . . . . . . 36
APPENDICES . . . . . . . . . . . . . . . . . . 39

v
APPENDIX A: Review of Literature
Electromyography

. . . . . . . . . 40

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

Yoga . . . . . . . . . . . . . . . . . . . . 44
Stabilization Research and Progress
Muscles included in the Core

. .

. . . . . 46

. . . . . . . . . . 52

Core Stabilization Techniques and Exercises . . 53
Results/Findings
Summary

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

. . . . . . . . . . . . . . . . . . 58

APPENDIX B: The Problem . . . . . . . . . . . . . 64
Statement of the Problem . . . . . . . . . . . 65
Definition of Terms . . . . . . . . . . . . . . 66
Basic Assumptions

. . . . . . . . . . . . . . 67

Limitations of the Study . . . . . . . . . . . . 67
Delimitations of the Study

. . . . . . . . . . . 68

Significance of the Study

. . . . . . . . . . . 68

APPENDIX C: Additional Methods . . . . . . . . . . 71
IRB: California University of Pennsylvania (C1).

. . 72

Informed Consent Form (C2) . . . . . . . . . . . 86
Demographic Sheet (C3)
Yoga Poses (C4)

. . . . . . . . . . . . 90

. . . . . . . . . . . . . . . 92

References . . . . . . . . . . . . . . . . . . 95
ABSTRACT

. . . . . . . . . . . . . . . . . . 99

vi
LIST OF TABLES
Table

Title

Page

1

Mean Normalized Peak EMG Activation for Rectus
Abdominus during Yoga Poses and Different
Surfaces . . . . . . . . . . . . . . 23

2

Mean Normalized Peak EMG Activation for External
Oblique during Yoga Poses and Different
Surfaces . . . . . . . . . . . . . . 24

3

Mean Normalized Peak EMG Activation for Erector
Spinae during Yoga Poses and Different
Surfaces . . . . . . . . . . . . . . 25

vii
LIST OF FIGURES
Figure

Title

Page

1

Yoga Poses, Tree Pose, Boat Pose, Side Plank
Pose, on stable and unstable conditions . . 93

1
INTRODUCTION

Yoga has become a popular exercise among those deemed
physically active, simply because it lacks the age
restrictions that accompany other exercise types, offers
exercise versatility, and has the potential to target
multiple systems without additional exercise equipment.
Since research has indicated the benefits of core muscle
recruitment, Yoga appears to encompass constant core
contracture during controlled deep breaths; if this
activity is maintained throughout the entire pose.

This

component is important, because the core helps maintain
posture during walking, assists in spine stabilization and
is instrumental in various sport actions.1-5
In addition to the benefits of core stabilization,
Yoga also incorporates balance and stabilization during
Yoga poses. This occurs because the muscles must contract
to maintain balance, which leads to strengthening via
increased motor neuron recruitment.3 Since Yoga contains
dynamic versatility, the individual is able to perform the
activity to their level of capability and build strength
based on the pose performed.

This type of exercise is also

cost effective, low impact, supplies versatility, targets

2
multiple systems, and functions as a stress reliever via
endorphin release during deep controlled breathing.6,7
However, there may be several conditions necessary to
perform Yoga safely; to achieve the desired benefit of
muscular strength and endurance. For example, a participant
must have adequate balance and be able to stand.

This is

necessary because Yoga requires participants to maintain
constant muscle contractions throughout the duration of the
pose. In addition, a participant who progresses from
beginner to advanced may possess the potential of creating
a dynamic workout. This workout may be achieved through
continuous repetition of various poses’ without rest. This
format of Yoga training is comparable to circuit exercises,
which are designed to target the participant’s heart rate.
When Yoga is utilized to its full potential, it is possible
for the participant to receive a relatively low impact
exercise designed to meet the individual’s goal for their
desired level of fitness. This is a component that may
offer the participant, athletic trainer, or other health
care professional; the opportunity to introduce Yoga into
their fitness or rehabilitation regimen.
Athletic trainers can take advantage of other
techniques in their exercise selection. Several studies
have indicated instability during exercise encourages

3
increased electrical activity in muscles. This activity
occurs because the enhanced volatility and movement
requires an increase in motor unit recruitment to maintain
stability and balance.3 Therefore, it may be concluded that
a combination of Yoga and surface instability may lead to
potential changes in participants of this exercise.
Research has also provided scientific evidence to support
the theory of instability through use of perturbations,
which may be described as the disturbance of motion.
Therefore, it appears the state of equilibrium on unstable
surfaces has the potential to increase the amount of
muscular activity for the participant.

8-12

The majority of the research examined concerning
increased muscular activity through unstable surfaces
focused on the core muscles, such as the rectus abdominus,
external oblique and erector spinae. In some cases, which
relied on the placement of electrodes; the internal oblique
and the transversus abdominus were also recruited. In
comparison to total muscle recruitment, the rectus
abdominus appeared to have a higher increase in activity in
comparison to the other muscles. However, the increase in
muscle activity relied on the type of exercise performed by
the participant. Additionally, while most results studied
indicated an increase in muscular contractions, several

4
other studies failed to produce a significant increase in
muscular contraction or none at all.

This inconsistency

may have been due to poor participant selection, lack of
balance, poor muscle tone, unfamiliarity with the pose,
poor electrode conduction, or other unknown factors.

13,14

While other researchers focused on specific muscles in
single poses, Norwood et al investigated instability
training and the muscle recruitment of the core during
dynamic multi-joint movement. He examined six muscles and
four exercises were used to test the latissimus dorsi,
rectus abdominus, internal oblique, erector spinae, biceps
femoris and soleus. EMG recorded activity levels for five
seconds, indicated significant increases in EMG activity
with the introduction of instability.

These results may

indicate use of dynamic multi-joint movement as the means
to enable the most muscle recruitment on unstable surfaces.8
While Norwood et al focused on major core muscles
during four varied exercises with multi-joint movement as
the best means of muscle recruitment, Petrofsky et al used
a slightly different protocol. Petrofsky et al examined
muscle use during core body exercise with a mini-stability
ball compared with abdominal crunches.

He compared data

between these two variables utilizing three levels of core
exercises. The results of this study concluded the mini-

5
stabilization ball required 50 percent more muscle activity
in comparison to standard crunches.12
Moreside et al, also found similar results as Norwood
through introduction of stabilization and perturbations.
Moreside et al incorporated trunk muscle activation
patterns, spine kinematics, and lumber compressive forces
that produce perturbations via the Bodyblade®. The addition
of this equipment produced the greatest muscle activation
in the internal and external oblique muscles and not the
rectus abdominus.

This variation in results may have been

due to the use of upper extremities to create the movement
and produce the instability.15
Marshall and Murphy utilized another approach to their
research. Their study examined the differences in
electromyographic activities in prime movers, specifically
the anterior deltoid, biceps brachii, triceps brachii,
pectoralis major, rectus abdominus, transversus abdominus,
and internal oblique, while performing certain exercises.
The results of this study indicated there was no
significant difference between muscle activity and surface
while a participant performed squats on stable surfaces.
However, the muscular activity in the triceps and
abdominals indicated a significant increase in muscle
recruitment on unstable surfaces during push-ups on the

6
Swiss ball.

This data may conclude the muscles used for

recruitment is affected by the type of instability that
occurs.10
In addition, a study conducted by Willardson et al,
researched surface stability and its correlation to muscle
activation and found similar results as in previous
studies. His findings indicated muscle activity increases
during unstable conditions. His study focused on examining
core muscle activity on stable ground and on an unstable
surface (BOSU Balance Trainer®). Four exercises were used to
examine the muscle activity, incorporating the rectus
abdominus, internal and external obliques, erector spinae,
and the transversus abdominus.

The participants were given

a specific exercise and were instructed to perform the
exercises at 50 percent intensity on stable and unstable
surfaces, and repeat the same exercises at 75 percent
intensity on stable surfaces. The results of his study
concluded there was no significant difference in muscle
activation in the core muscles he targeted regardless of
the surface.13
In conclusion, of the literature examined for this
study, most researchers focused on the core stabilizing
muscles of the abdominal area.

Although several studies

concentrated on prime movers of the upper extremities, it

7
appears most research supports the theory of increased
muscular contraction and electrical activity in muscles
that are recruited to perform exercise on unstable
surfaces.8-14 Additional research is certainly warranted,
given the results reviewed by the researcher.

Even though

Yoga appears to be an alternative option to physically
active participants in all ages with minimal risk, I plan
to investigate if optimal results may be achieved through
this method on stable versus unstable surfaces. Since
variation in data already exists, I plan to place controls
on selection of participants and criteria for the type of
pose, length of pose and surface for the data collection.
Therefore, the purpose of this study will be focused on
analyzing the EMG activity in the core muscles during
specific poses on stable and unstable surfaces.

8

METHODS

The primary purpose of this study was to examine EMG
activity of the rectus abdominus, external oblique and
erector spinae during static Yoga poses on stable and
unstable surfaces. This section includes the following
subsections: research design, subjects, preliminary
research, instruments, procedures, hypotheses, and data
analysis.

Research Design

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

The independent

variables were Yoga poses with three levels, each pose
varying in level of difficulty, and surface stability
condition with two levels, stable and unstable.

The Yoga

poses including 3 static Yoga poses consisting of one
beginner pose, an intermediate pose, and an expert pose.
The surface stability condition consisted of the stable and
unstable surface. The stable surface was solid ground on a
concrete floor. The unstable surfaces were on a foam
surface and BOSU (Both Sides Up) ball. The dependent

9
variable was the peak EMG activity measured in the rectus
abdominus, external oblique, erector spinae and reported as
a percentage of the maximal voluntary contraction (%MVC).

Subjects

The examiner received approval to conduct the study
from the California University of Pennsylvania
Institutional Review Board (Appendix C1). The examiner
proceeded to recruit volunteer subjects via announcements
made by the researcher in the California University of
Pennsylvania Health Science classes. All subjects signed
and dated an Informed Consent Form (Appendix C2) prior to
participation in the study. Each participant’s identity
remained confidential and was not included in the study.
There were 17 subjects that volunteered for this study. The
subjects were physically active male and female, college
aged, students.
The examiner explained the purpose of the study to the
students in two classes: Athletic Training Clinical
Education II and Orthopedic Evaluation in Sports Medicine.
The subjects were notified of the procedures and protocols
necessary to complete the study. The subjects were also

10
informed of all possible dangers and benefits of the
experiment.
The researcher explained the inclusionary and
exclusionary criteria which included, having no balance
problems, vertigo, taking any medications that could cause
any of the above mentioned problems, and being physically
active. Physically active was defined as participating in
some form of exercise for a minimum of thirty minutes at
least three times per week.
Once the announcements and introductions to the study
were made, the examiner distributed the demographic sheet
(Appendix C3) to all students in the classroom class to
fill out. The demographic sheet contained questions about
any medical problems causing balance problems and it
questioned the subjects’ physical activity.
Once the demographic sheet was completed, the examiner
reviewed the potential subject’s information to look for
any red flags. The red flags for the study were subjects
who had balance problems created by previous injury,
medication, and medical problems. Another red flag was
whether or not the potential subjects met the minimum
thirty minute, three times per week exercise requirement.
If any of the potential subjects had red flags, the

11
examiner notified the subjects of their exclusion from the
study.
Once participants were identified, a sheet of paper
was handed out to the class. The (participants) subjects
were asked to write down their names, email addresses, days
and times available to participate in the study. The
subjects that signed the sheet were informed they would
receive an email within the next day consistent of names,
dates and times of when the study would be conducted. Prior
to exiting the classroom, the researcher notified the
subjects that they had the option of resigning from the
study without any repercussions prior to beginning the
study.
Each subject participated in a 5 minute warm-up
session consistent of 1 minute of biking and then for the
additional 4 minutes, the subjects completed 3 step by step
Yoga Sun Salutations. The warm-up was performed before the
study to warm the muscles and reduce the chance of injury.
Then the subjects proceeded to participated in the 30
minute exercise program.
The exercise program consisted of completing a maximal
voluntary contraction 3 times for each individual muscle.
The subjects were shown the way to perform each individual
MVC test by the examiner. The purpose of the MVC (maximal

12
voluntary contraction) was to obtain the muscles’ maximum
muscle activity. The MVC allowed for a basis of comparison
for the muscle activity during the Yoga poses. The
comparison dictated whether or not the Yoga poses targeted
the muscles’ maximum contraction.
The subjects were instructed on how to properly
perform each Yoga pose; then the subjects completed the 3
designated Yoga poses, the Tree pose, Boat pose, and Side
Plank pose on the stable and unstable surfaces. The
subjects completed two trials of the Yoga poses during the
30 minute exercise protocol. The subjects were instructed
to perform a cool-down consisting of stretching at the end
of the exercise program.

Preliminary Research

A pilot study was conducted with this research
project. The students with the aforementioned requirements
entered the California University of Pennsylvania athletic
training lab and reviewed the steps needed in order to
perform the experiment. The procedure began with the
subjects performing a warm-up program and concluded with
the designed experimental exercise. The warm up program
consisted of 1 minute of biking. The subjects proceeded to

13
complete three sets of Yoga poses called Sun Salutations
for the remaining 4 minutes of the warm up. Then the
subjects proceeded to select the order of Yoga poses to be
performed via counterbalanced random assignment.
The researcher instructed the subjects to perform
maximal voluntary contraction tests for the rectus
abdominus, external oblique and erector spinae consisting
of a standard crunch for the rectus muscle, a crunch with
external rotation, and a back extension referred to as the
superman, prior to beginning the exercise protocol. The
subjects were required to hold the abdominal crunch,
abdominal crunch with external rotation, and the back
extension positions for five seconds. As the subject held
the positions, the examiner applied resistance trying to
push the subject in the opposite direction.
Next, the subjects were allowed a five second rest
period before the subject completed two additional five
second MVCs. Each individual subject had 30 seconds to
complete three MVCs(maximal voluntary contractions), for
each of the three muscles, each contraction lasting five
seconds. The average of their maximal voluntary contraction
was used in comparison to the electrical activity recorded
during the Yoga poses which were held for fifteen seconds.
During the process, the researcher determined the subjects’

14
ability to understand the assigned protocol, whether the
subjects had the capability to complete the warm-up
protocol, and the peak electrical activity of the rectus
abdominus, external oblique, and erector spinae contracture
during the experiment. The data was saved on the laptop
under the Acqknowledge software. In order to separate the
data, each subject’s data was recorded in correspondence to
the subject’s number, pose number, surface condition, and
trial number.

Instruments

The data collection instrumentation used for this
study consisted of EMG equipment, including a MP150
amplifier with wired telemetry unit connected to a PC
running Biopac Acknowledge 4.0 software.

Additionally a

BOSU ball and foam pad was utilized along with a standard
stop watch, ace wrap to secure the electrodes and prevent
the EMG equipment from moving during the completion of the
Yoga poses, and alcohol prep pads to remove any residue on
the subjects preventing the electrodes from adhering to the
skin.

15

Procedure

There was a test trial conducted before the actual
experiment occurred. The test trial consisted of the
subjects completing each pose on each surface. The trial
allowed for the subjects to familiarize themselves with
Yoga before starting the actual testing. The subjects who
volunteered for the experiment were given a sheet of
instructions that described the experiment and the
procedures needed to complete the exercises. After the
subjects read the instructions, they were given a chance to
ask questions or if the subjects chose not to participate,
they had the opportunity to resign from testing.
There was a 5 minute warm-up consistent of biking for
1 minute to warm the muscles. Following the 1 minute
biking, the subjects performed three various Yoga steps
called Sun Salutations for the additional 4 minutes. The
examiner performed each step with each individual subject
and instructed the individual subjects to follow the
examiner’s step by step directions and movements. In order
to ensure all subjects did not spend more or less time in
one pose than the other, a stop watch was used to time 5
seconds between each Sun Salutation pose. In addition, a

16
voice recording indicating, to the subjects when to move,
was utilized.
Once the warm-up was completed, the subjects proceeded
to select which poses to complete on stable and unstable
surfaces. The stable surface consisted of concrete and the
unstable surfaces were a combination of a foam pad to stand
on for the Tree pose and the BOSU ball for the subjects to
sit on for the Boat and Side Plank poses. The order in
which the subject completed the poses were chosen by doing
a counterbalanced random assignment where the examiner
separated the order of poses starting from beginner,
intermediate, and expert until there were six possible
choices.
Prior to selecting the order of yoga pose, the
examiner cleaned the subject’s corresponding muscle belly
with an alcohol prep pad to remove excess dirt. This
provided a better surface for the electrodes to adhere.
Then the examiner placed the surface EMG electrodes over
the muscle belly of the rectus abdominus, the external
oblique, and the erector spinae on the subject’s dominant
side. The dominant side was indicated by the examiner
asking the subject what was his or her dominant side. An
additional ground electrode was placed below the
ASIS(Anterior Inferior Iliac Spine) to reduce the

17
interference of electrical activity from other muscles. The
examiner proceeded to wrap an elastic wrap around the
subjects’ torso to hold the Biopac and electrodes in place.
Before completing the Yoga poses, the subjects were
required to perform a Manual Voluntary Contraction. The
subject was instructed to perform a standard abdominal
crunch for the rectus abdominus with legs extended. The
subject held the end position as the examiner tried to push
the subject into extension. For the external oblique, the
subject performed an abdominal crunch using the subject’s
elbow and crossing over to the subject’s dominant side for
the external oblique. The subject held the end pose while
the examiner tried to pull the subject in the opposite
direction. For the erector spinae, the subject was on the
stomach. The subject performed a back extension while the
examiner tried to push the subject into flexion.
After retrieving the MVCs, the subjects began to
perform the selected Yoga poses and perform the Yoga pose
in the order chosen via counterbalanced random assignment.
The subjects were instructed to start in the corresponding
beginning phase then progress to the proper end phase of
the exercise and hold the pose for 15 seconds. As
previously done for the warm-up, a stop watch was utilized
to ensure all subjects spend equal five second rest time

18
between poses. As the subject maintained the Yoga pose, the
examiner documented the peak activity of each muscle on
both surfaces for two trials.
The data was saved on the laptop the EMG software was
located. The subjects’ data was documented based on subject
number, pose number, surface, and trial number. Each
beginning phase varied based on the different Yoga pose.
First, the subjects performed each pose on the surface
selected during the counterbalanced random assignment. The
poses were performed on the concrete ground for the stable
surface and the BOSU ball and foam pad for the unstable
surfaces depending on pose difficulty. The Tree pose was
performed on the foam pad and the Boat pose and Side plank
pose were both performed on the BOSU ball for the unstable
surface.
Each subject completed 2 trials. Each trial consisted
of the completion of the three Yoga poses on both stable
and unstable surfaces. The subjects were given a five
second rest period between each pose. The subjects
completed the second assigned pose, followed by the third
assigned pose on both stable and unstable surfaces. Once
the subjects completed the first trial run, there was one
additional trial run conducted. During, the second trial,
the exact same procedures were followed. The two trials

19
were averaged and compared to the subject’s percentage
maximal voluntary contraction.
Once the two trials were completed and documented, the
subjects were encouraged to do a 5 minute cool down. This
activity consisted stretching the quadriceps, hamstrings
and shoulders to minimize the chance of muscle soreness.
After the experiment, the subjects were free to leave.

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 an increase in EMG activity for all 3
muscles groups for all 3 Yoga poses under the unstable
condition when compared to the stable condition.

The following sub-hypotheses will be tested to examine
effects of Yoga pose and stability condition on each target
muscle:

1. There will be an increase in EMG activity for the
rectus abdominus for all 3 Yoga poses under the

20
unstable condition when compared to the stable
condition.
2. There will be an increase in EMG activity for the
external oblique for all 3 Yoga poses under the
unstable condition when compared to the stable
condition.
3. There will be an increase in EMG activity for the
erector spinae for all 3 Yoga poses under the unstable
condition when compared to the stable condition.

Data Analysis

All data will be analyzed by SPSS version 18.0 for
windows at an alpha level of 0.05.

The research hypothesis

will be analyzed using a factorial repeated measures
analysis of variance.

21

RESULTS

The purpose of this study was to examine EMG activity
of the rectus abdominus, external oblique, and erector
spinae during static Yoga poses on stable and unstable
surfaces. The EMG activity was measured using a MP150
amplifier connected to a laptop with the Biopac
Acqknowledge 3.0 software. The following section contains
data collected throughout the study and is divided into the
following subsections: Demographic Information, Hypothesis
Testing, and Additional Findings.

Demographic Information

A total number of 17 physically active, college aged
subjects volunteered to participate in the study.
Physically active subjects were chosen to reduce the
chances of injury compared to a sedentary subject suddenly
completing exertional Yoga poses. These subjects were
identified as such via the demographic information sheet
being handed to the subjects, completed, and given back to
the examiner. The subjects consisted of 5 males and 12
females, all of whom were 18 years or older, and college

22
undergraduates enrolled in California University of
Pennsylvania. All subjects were physically active with the
definition of physically active described as completing
some form of exercise or exertional activity with the
potential of raising the heart rate to the target heart
zone and maintaining the condition for a minimal of 30
minutes and completing the activity at least three out of
the seven days in a week. Subjects with inner ear problems,
vertigo, major stability issues, weak joints, or subjects
taking any form of medication causing balance or stability
problems were not included in the study.

Hypothesis Testing

The initial test performed was a 2x3x3 factorial ANOVA
(surface x pose x muscle) to examine if muscle had an
interactive effect on peak EMG activity.

The interaction

between surface condition, pose and muscle was not
significant (F(4,64)=.626, p=.646). For this reason, three
2x3 factorial ANOVAs were computed, one for each muscle.
Hypothesis 1 examined the effects on the rectus abdominus,
hypothesis 2 on the external oblique and hypothesis 3 on
the erector spinae.

23
Hypothesis 1: There will be an increase in EMG
activity for the rectus abdominus for all 3 Yoga poses
under the unstable condition when compared to the stable
condition.

Table 1. Mean Normalized Peak EMG Activation for Rectus
Abdominus during Yoga Poses and Different Surfaces
Mean Peak EMG (SD)
Stable

Unstable

Tree

111%(82.3)

119%(99.3)

Boat

115%(73.6)

133%(101.0)

Side Plank

142%(125.2)

129%(107.5)

Conclusion 1: A 2x3 within-subjects factorial ANOVA
was calculated comparing the percentage of activity in the
rectus abdominus during 3 Yoga poses on two different
surfaces. The main effect of surface was not significant
(F(1,16)=1.149, p=.300). The main effect of pose was not
significant (F(2,32)=1.879, p=.169). The interaction
between surface and pose was also not significant
(F(2,32)=2.018, p=.150).

Hypothesis 2: There will be an increase in EMG
activity of the external oblique for all 3 Yoga poses under

24
the unstable condition when compared to the stable
condition.

Table 2. Mean Normalized Peak EMG Activation for External
Oblique during Yoga Poses and Different Surfaces
Mean Peak EMG (SD)
Stable

Unstable

Tree

123%(104.2)

124%(125.5)

Boat

133%(180.9)

153%(169.6)

Side Plank

164%(189.1)

143%(139.5)

Conclusion 2: A 2x3 within-subjects factorial ANOVA
was calculated comparing the percentage of activity in the
rectus abdominus during 3 Yoga poses on two different
surfaces. The main effect for surface for the external
oblique was not significant (F(1,16)-.001, p=.977). The
main effect for pose for the external oblique was not
significant (F(2,32)=1.787, p=.184). The interaction
between surface and pose for the external oblique was also
not significant (F(2,32)=2.008, p=.151).

Hypothesis 3: There will be an increase in EMG
activity of the erector spinae for all 3 Yoga poses under

25
the unstable condition when compared to the stable
condition.

Table 3. Mean Normalized Peak EMG Activation for Erector
Spinae during Yoga Poses and Different Surfaces
Mean Peak EMG (SD)
Stable

Unstable

Tree

135%(138.8)

123%(115.0)

Boat

150%(192.1)

172%(255.6)

Side Plank

152%(171.3)

156%(189.6)

Conclusion 3: The main effect for surface for the
erector spinae was not significant (F(1,16)=.923, p=.351).
The main effect for pose for the erector spinae was not
significant (F(2,32)=.823, p=.448). The interaction for the
erector spinae was also not significant (F(2,32)=1.409,
p=.259).

26

DISCUSSION

The best clinicians match exercises to the abilities
and goals of their patients.

Yoga is a type of exercise

not often chosen by athletic trainers but previous research
shows that it may be a viable choice for the practicing
athletic trainer.

This section will examine Yoga as an

exercise modality for athletic trainers in light of the
results found in this study.

The following section is

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

Discussion of Results

The goal of this study was to examine the peak EMG
activity of the rectus abdominus, external oblique, and
erector spinae during static Yoga poses on stable and
unstable surfaces. Yoga has the benefit of reducing stress
and potentially recruiting more muscle fibers because of
the balance required to maintain each pose.3-7 This has the
potential to increase muscular strength in the targeted
muscle.

Previous research has determined that when the

body is subjected to unstable conditions, such as a foam

27
surface, compared to stable surfaces, the central nervous
system will recruit more muscle fibers in order to help the
body maintain balance.3 No studies have examined the
combined effect on Yoga and surface condition on muscle
activation.
Yoga can potentially stimulate muscle activity in the
equivalence of a standard abdominal crunch exercise.16 Yoga
also tends to be less stressful on the joints and capable
of being completed by any age group as opposed to other
exercises which can cause a higher amount of stress to the
joints such as running. This makes it a valuable tool for
the athletic trainer, especially when working with patients
that cannot perform high impact or high intensity
exercises.

An analysis of the completed study assisted in

revealing why the results of this study may have occurred.
Previous studies examining muscle activity during
exercises on stable and unstable surfaces found muscle
activity to significantly increase on the unstable in
comparison to the stable surface.8-12 Other studies found no
significant difference in muscle activity during exercise
on either stable or unstable surface.13,14

Due to these

conflicting results, the present study was performed.
The present study determined that all three Yoga poses
(Tree, Boat and Sid Plank) were effective in activating the

28
target muscles at a high level.

The study did not find any

effect of stability condition on muscle activation.

This

was different compared to previous studies for several
reasons. Potential contributing factors in this difference
include, the type of subjects, the utilization of Yoga
poses as opposed to traditional exercises, and the EMG
equipment used to measure electrical activity
During this study, there were no significant findings
in muscle activity increasing in the individual core
muscles during surface instability. During subject
recruitment, the examiner only focused on subjects who were
physically active. Previous studies recruited subjects
familiar with the designated exercise.8-10,12,13 For the
present study, there was no consideration concerning the
type of exercise the subjects completed, therefore all but
one of the subjects was a novice to Yoga. Subjects
completing weight training compared to subjects running for
thirty minutes strengthens different muscles and provides a
difference in skill level making even the easiest of the
Yoga poses a challenge to hold. With these potential
differences, the examined muscles in the core may or may
not contract more or less because of the difference in
exercise protocol. These differences can lead to a
variation of electrical activity and skewed data.

In a

29
more trained subject population, the stability condition
would have been more likely to show an effect measurable by
EMG.
The Yoga poses selected by the examiner were based on
perception of difficulty ranging from least difficult to
more difficult and consisted of the Tree pose, Boat pose,
and Side Plank pose. Each Yoga pose was selected based on
the pose’s capability of targeting at least one of the
three examined core muscles. The Tree pose was selected on
the assumption it would target the erector spinae. The Boat
pose and Side Plank pose were presumed to target the rectus
abdominus and external oblique respectively. Most of the
subjects, because of their unfamiliarity with Yoga, had to
be shown the pose and given proper instruction on how to
achieve the poses. Depending on the order chosen by the
subject via counterbalanced random assignment, the subjects
would then progress to complete the assigned pose on the
stable or unstable surface. In most cases, performing any
type of exercise on an unstable surface will increase the
amount of muscular activity because of the unstable
conditions but sometimes that is not always the case.8-12
Depending on the exercises and surface changes, there may
be no increases in activity.13,14

30
The examiner did not have the resources to obtain the
same EMG equipment used in previous studies. The examiner
used an MP150 Biopac with wired telemetry and surface
electrodes for the study. The electrode placement was
directly over the muscle belly with a ground wire placed
below the Anterior Inferior Iliac Spine (ASIS). The ground
wire was placed in order to reduce the amount of
unnecessary electrical activity interfering with results.
Despite these precautions, electrical activity from muscles
not targeted by the examiner, such as the internal oblique
and potentially the transversus abdominus, had the
potential to interfere with the electrical activity of the
examined core muscles during the study. The interference
possibly caused a large increase in muscle activity in the
external oblique, erector spinae and rectus abdominus. The
potential interference allowed for the peak EMG of each
muscle on both surfaces to exceed each muscle’s maximal
volitional contraction. This increased activation of
surrounding muscles could mask increased activation in the
targeted muscles brought about by the unstable condition.
The electrical activity in the rectus abdominus,
external oblique, and erector spinae on BOSU ball and foam
surface in this study was not significantly different.
There also was no difference in muscular activity during

31
each selected pose. However, this study did not find Yoga
to be a completely useless tool. A study performed by
Petrofsky found Yoga has the ability to activate muscle
activity in the same sense as standard core exercises.16 In
the present study the same conclusion can be made for all
three Yoga poses.

The results showed Yoga does possess the

ability to target the muscles’ maximal volitional
contraction when performing any of the selected Yoga poses
on either stable or unstable surface. The results show
despite surface and pose selection, Yoga has the potential
of being effective when striving to strengthen the core
muscles. Regardless of the selection of poses or what type
of surface Yoga is performed on, the core muscles will not
increase in electrical activity more than if the poses were
performed on an unstable surface.
Yoga uses the subject’s own weight as a means to
strengthen the athlete. This makes Yoga very cost
effective, user friendly, and challenging for patients at a
variety of fitness levels. Athletic trainers interested in
attempting to strengthen athletes’ core via Yoga poses do
not have to focus primarily on pose selection. However,
Athletic Trainers should be aware of the type of physical
activity completed by athletes. This is important because
Yoga potentially affects the core muscles differently based

32
on previous strengthening exercises. There is a variety of
poses to select from with Yoga and any athletic trainer
does not have to be restricted to certain poses because
Yoga poses targeted towards the core muscles tend to
activate the maximum muscle activity. Yoga can also be used
in the clinical setting not only as because it cost
effective and a stress reliever but also because it has the
capability of strengthening the intended muscles.

Conclusions

This study showed Yoga can be an effective tool to use
by any person seeking a less stressful way to strengthen
the rectus abdominus, the external oblique, and the erector
spinae in the body. These findings did not show any
difference due to pose selection, surface change, and
muscle activation of the core but it did show an overall
increase in activity in all muscles tested. Therefore, it
can be concluded that Yoga is an effective exercise tool
that can be used by anyone. It would beneficial for
subjects looking to practice Yoga, to have some knowledge
of pose and proper technique in order to adequately
strengthen the core muscles.

33
Despite the lack of any significant data in regards to
surface, muscle activity, and pose, Yoga has shown it has
the capabilities of activating the core muscles. This
allows for athletic trainers and any other health care
professionals to use Yoga as a strengthening tool. Yoga is
a simple and cost effective way to provide diversity to
strengthening protocols without excluding the young, the
adolescent, the adult or the elderly.

Recommendations

While the majority of the subjects understood the
tasks assigned to them, they were unfamiliar with the
concept of Yoga. Many of the subjects were unaware of the
technique and proper form required when performing Yoga.
During the exercises, subjects had a tendency to break the
static Yoga position by lowering the legs or arms or
shifting places trying to maintain balance. This resulted
in fluctuations of the electrical activity in the muscles
being measured which lead to the data results being less
consistent then when subjects accurately performed the
exercises. It is recommended that future studies recruit
subjects experienced in the practice of Yoga.

34
Two unstable surfaces were chosen by the examiner in
order in order to ensure the completion of the poses.
However, the examiner also did not want to choose a
unstable surface that would be too difficult to complete by
the subjects. The subjects had to be able to perform and
hold the poses for fifteen seconds. However, the surfaces
could not be too simple in fear of little to no increase in
muscle activity. For future studies, it is recommended
having each subject perform a pre-trial to examine his or
her balance capabilities in an effort to have a more
appropriate level of challenge.
The three Yoga poses chosen for the study were assumed
to target the core from prior experience. Further research
on Yoga poses and the actual muscle targets of those poses
should be initiated in order to accurately target the
proper muscles. In addition, before the actual data
collection, the subjects were required to perform three
manual muscle tests in order to compare the data results
with the subject’s maximal volitional contraction. Some
subjects performed a standard abdominal crunch with arms
crossed over their chest or arms crossed behind their head.
Some subjects would have their knees flexed and others
would have their legs extended. There was an inconsistent
performance of the manual muscle testing. For future

35
studies, it is recommended the examiner establish a
specific protocol for manual muscle testing for all the
subjects.

36
REFERENCES
1.

Stevens V, Bouche K, Mahieu N, Coorevits P,
Vanderstraeten G, Danneels L. Trunk Muscle Activity in
Healthy Subjects during Bridging Stabilization
Exercises. BMC Musculoskeletal Disorders. 2006;7:75.

2.

Huang Q, Hodges P, Thorstensson. Postural Control of
the Trunk in Response to Lateral Support Surface
Translations during Trunk Movement and Loading.
Experimental Brain Research. Experimentelle
Hirnforschung. Expérimentation Cérébrale.
2001;141(4):552-559.

3.

Clark MA, Lurett SC. NASM’s Essentials of Sports
Performance Training. Baltimore, MD. Lippincott
Williams &Wilkens; 2010: 171-190.

4.

Carpenter M, Tokuno C, Thorstensson A, Cresswell A.
Differential Control of Abdominal Muscles during
Multi-Directional Support Surface Translation in Man.
Experimental Brain Research. Experimentelle
Hirnforschung. Expérimentation Cérébrale.
2008;188(3):445-455.

5.

Stevens V, Vleeming A, Bouche K, Mahieu N,
Vanderstraeten G, Danneels L. Electromyographic
Activity of Trunk and Hip Muscles during Stabilization
Exercises in Four-Point Kneeling in Healthy
Volunteers. European Spine Journal: Official
Publication Of The European Spine Society, The
European Spinal Deformity Society, And The European
Section Of The Cervical Spine Research Society.
2007;16(5):711-718.

6.

Alejandro Chaoul M, Cohen L. Rethinking Yoga and the
Application of Yoga in Modern Medicine. Cross Currents
[serial online]. June 2010;60(2):144-167. Available
from: Academic Search Complete, Ipswich, MA. Accessed
September 9, 2010

7.

Prentice W. Arheim’s Principles of Athletic Training:
A Competency-Based Approach. New York, NY. McGrawHill; 2006: 101.

37

8.

Norwood J, GS Anderson, M Gaetz, and P Twist.
Electromyographic Activity of the Trunk Stabilizers
during Stable and Unstable bench Press. J. Strength
Cond. Res. 2007; 21(2): 497-502.

9.

Monfort-Pañego M, Vera-García F, Sánchez-Zuriaga D,
Sarti-Martínez M. Electromyographic Studies in
Abdominal Exercises: A Literature Review, Journal Of
Manipulative And Physiological Therapeutics.
2009;32(3):232-244.

10.

Marshall P, Murphy B. Increased Deltoid and Abdominal
Muscle Activity During Swiss Ball Bench Press. Journal
Of Strength And Conditioning Research / National
Strength & Conditioning Association. 2006;20(4):745750.

11.

Slijper H, Latash M. The Effects of Instability and
Additional Hand Support on Anticipatory Postural
Adjustments in Leg, Trunk, and Arm Muscles during
Standing. Experimental Brain Research. Experimentelle
Hirnforschung. Expérimentation Cérébrale.
2000;135(1):81-93.

12.

Petrofsky JS, Batt J, Davis N. Core Muscle Activity
during Exercise on a Mini Stability Ball Compared with
Abdominal Crunches on the Floor and on a Swiss Ball.
The Journal of Applied Research. 2007;7(3) 255-272.

13.

Willardson J, Fontana F, Bressel E. Effect of Surface
Stability on Core Muscle Activity for Dynamic
Resistance Exercises. Intl J Sports Phys Performance.
2009;4(1):97-109.

14.

Illyés A, Kiss R. Electromyographic Analysis in
Patients with Multidirectional Shoulder Instability
During Pull, Forward Punch, Elevation and Overhead
Throw. Knee Surgery, Sports Traumatology, Arthroscopy:
Official Journal Of The ESSKA. 2007;15(5):624-631.

15.

Moreside J, Vera-Garcia F, McGill S. Trunk Muscle
Activation Patterns, Lumbar Compressive Forces, and
Spine Stability When Using the Bodyblade. Physical
Therapy. 2007;87(2):153-163.

38
16.

Petrofsky JS, Cuneo M, Dial R, Morris A. Muscle
Activity during Yoga Breathing Exercise Compared to
Abdominal Crunches. J Applied Res. 2005;5(3):501-507.

39

APPENDICES

40

APPENDIX A
Review of Literature

41

REVIEW OF LITERATURE

Electromyography is a technique that is used to
measure the electrical activity in muscles during
concentric, eccentric, and isometric activity. It can be
used by applying adhesive pads to the very center of the
muscle to predict maximum contraction.
EMG techniques allow researchers to determine the
muscles that are contracting during certain exercises and
the relative strength of these contractions.1 Yoga is an
exercise that requires minimum movement, depending on the
level of experience and whether or not it is static or
dynamic. Regardless, in Yoga, the subject to maintain
certain poses, some more difficult than others, allowing
for the subject to strengthen his or her muscles. In most
of all the Yoga poses, it is required to contract the core
muscles to maintain proper balance and breathing. In
sports, the core can be a main contributor in every
movement an athlete performs. EMG can be utilized to
evaluate the muscle activation during various exercises.2
Many researchers have looked at EMG activity during bench
press or typical abdominal crunches but none have analyzed
static yoga poses.3,4

42
The purpose of this Review of Literature is to
enlighten the reader on previous work examining
electromyography and variation in surfaces and their
ability to affect EMG.

The review of literature includes

the following sections: Electromyography, Yoga,
Stabilization and Research Progress, Core Stabilization
Techniques and Exercises.

The literature review will end

with a summary of the research performed to date.

Electromyography
Electromyography is a commonly used device for
detecting and measuring muscular activity. This tool can be
of great help in evaluating the effectiveness of various
exercises in activating target muscles.

It can also be

used as a learning tool for athletes exhibiting a
deficiency in muscular strength. In turn, the athlete can
monitor his or her progression through the rehabilitation
process by comparing before and after scores. This section
will examine some examples of how EMG can best be utilized
to evaluate muscle function.

Best practices will take

variables like skin moisture, surface contours and skin
type into account when using surface electrodes.
Roy et al examined the performance of surface EMG
sensors, different conditions and the affect of detecting

43
stability between sensor and the skin. Twenty-four subjects
were used, twelve males and twelve females. The researcher
used different detection surface contours and also
adhesives when examining electrical contact with the skin.
The skin for both studies examined dry and wet skin.
Double-sided tape and increased surface contour increased
the disruption in electrical activity. The application of
hydrophilic gel provided greater movement especially on the
subjects with moist skin. In general, when applying
electrodes to the skin, precise cleaning and sufficient
adhesive measures are necessary for a more accurate
electrical reading.1
Jaggi et al also assessed surface and the effects on
EMG reading. Jaggi et al also examined fine wire
electromyography. Eleven female participants were used for
this study. Self adhesive surface electrodes were placed
over certain muscles and asked to participate in certain
movements. The dual needle technique was performed after a
twenty minute rest period. This study showed that surface
EMG can assist in the classification of shoulder
instability based on abnormal muscle patterns.2
There are different Electromyography devices and
sensors that can be used but knowing how to use them
properly is the key to receiving the best results in an

44
experiment. One experiment examined the subjects’ skin type
and found that different surfaces have to be taken into
consideration because it may lead to a better or inaccurate
reading.1 Another study also researched surface contour and
the effects on electrical detection. The researchers also
tested whether or not EMG could be used for the detection
of shoulder instability and the results showed that it was
possible.
Electromyography is a useful tool to use but knowing
how to accurate use EMG will allow for the researcher to
obtain the best possible results. It has been shown that
EMG has the possibility to analyze shoulder instability in
addition to muscle activity. Measuring the electrical
activity of muscles during Yoga poses should also be a
possibility.

Yoga
Yoga has been a practice that has been utilized for
many years in multiple countries. The United States is
finding Yoga to be a popular and successful way to exercise
without stressing the body’s joints. Yoga can be an
alternative for those whose are not as young and physically
active. Yoga poses can also be modified to make Yoga more
complex. For example, changing static poses and adding

45
dynamic movement to the Yoga positions. Many researchers
theorize that Yoga assist in maintaining certain diseases
such as cancer.3 However, from previous experience, mostly
every Yoga pose requires the practitioner to activate his
or her core muscles.
Yoga can be categorized as either a mind-body
technique (meditation) or actual movement and active
participation (Yoga).3 Yoga requires the body to maintain
core contracture throughout the entire pose in most
positions which makes Yoga a very useful exercise in
sports. Petrofsky et al performed a study that analyzed
muscle contracture of the right and left rectus abdominis
as well as the right and left external oblique. Twenty-nine
subjects 14 male and 15 females were used for the study.
Muscle activity was monitored during deep breathing
exercised in a seated position. The muscle activity for
deep breathing equaled the muscle activity in abdominal
crunches. Yoga can be assumed to be just as effective at
strengthening the muscles as standard abdominal crunches.4
The proper technique of Yoga consist of maintain
proper form, while taking deep, steady breathes.5 When done
correctly, Yoga releases endorphins that help sooth away
stress.5 Yoga is also a practice in which stabilization and
balance are important components.

46

Stabilization Research and Progress
Stabilization is a technique that may assist the
athletes in strengthening their muscles based the level of
muscle fibers recruited.6 When introducing an unstable
perturbation or surface to the end of an athlete’s joint,
more muscle fibers are recruited because it takes more
strength from the athlete to provide balance and stability.
The core is a main component that participates in most
physical activity. For example, when walking the core
muscles contract to maintain a proper center of gravity. If
the core muscles can be strengthened through stabilization
exercises then the athletes can gain more strength for
future exercises.
Current research has shown most exercises, when
introduced to some issue of stability, allow for
electromyography of the muscles to increase. Norwood et al
investigated instability training and the muscle
recruitment of the core during dynamic multijoint movement.
Subjects included 10 male and 5 female elite conditioning
coaches and/or personal trainers with an average of 8.4
years of experience. A repeated-measures analysis of
variance and a paired t-test. Six muscles were examined and
four exercises were used to test the six muscles. The

47
muscles examined for this study were the latissimus dorsi,
rectus abdominus, internal oblique, erector spinae, biceps
femoris and soleus. The four exercises consisted of the
bench press but on four different surfaces: stable bench
press, upper-body instability on a stability ball, lower
body on BOSU ball, and dual instability consistent of the
stability ball for upper-body and BOSU ball for lower body.
EMG recorded activity levels for five seconds. The study
showed significant increases in EMG activity with
increasing instability.7 There was an additional study that
researched muscles in the core and their activity during
unstable conditions.
Marshall et all also did a similar study involving the
deltoid and abdominal muscles and a swiss ball for
instability. The study was conducted to investigate muscle
activity of the upper body and abdominal muscles during
concentric and eccentric contraction on and off a swiss
ball. Deltoid and abdominal muscle activity increased with
repetitions on the swiss ball. Deltoid activity increases
when introduced to instability. Increased abdominal
activity was not hypothesized but is presumed to be true
with anecdotal reasoning.8 Another researcher examined the
core muscles but examined muscle activity during standing.

48
Slijper et al performed a study to examine the trunk
muscle activation during standing. The study included
muscles involved in total body stabilization: soleus,
tibialis anterior, rectus abdominus, rectus femoris, biceps
femoris, erector spinae, biceps brachii, triceps brachii,
flexor carpi radialis and the extensor carpi ulnaris.
Subjects performed ante-flexion movements in one shoulder
while standing on a stable platform or on unstable board.
Eight healthy subjects, six males and two females, were
used for this experiment. Changes in background activity
and displacements of center of pressure were quantified in
time intervals. Leg and trunk muscles showed a significant
drop but the arm muscles showed no significant change. The
change was visible in both surface types.9 Another study
analyzed previous studies all targeting the abdominal
muscle activity during stabilization conditions and found
similar results.
Monfort-Pañego et al focused on many previous
electromyography experiments and compiled the research
articles on the EMG activity of the abdominal muscles
together for a large literature review. Since this was a
literature review, there were multiple male and female
subjects within different age ranges. The researchers used
the MEDLINE and Sport discus databases to locate the

49
articles. Eighty-seven studies were included in the
literature review. There were studies that found
significance in the increase of the abdominal muscle
activity during the stabilization exercises. Other studies
found no significant difference in muscle activity based on
surface.10 The results varied in both directions so another
study was conducted which had better results.
Stevens et al studied abdominal muscle activity levels
during bridging stabilization exercises. Thirty healthy
university students and the subjects were fifteen male and
fifteen females. The surface EMG activity was evaluated on
both sides of the rectus abdominis. The muscle activity
altered depending on the task or exercise administered. All
back muscles assist in spinal positioning and movement.11
Stevens et al also performed another study examining the
trunk and hip muscles and their importance in spinal
stabilization.
Stevens et al also studied EMG activity of trunk and
hip muscles during three four-point kneeling stabilization
exercises. Thirty healthy volunteers, fifteen men and
fifteen females, were used. The highest muscle activity was
found in the ipsilateral lumbar multifidus and gluteus
maximus. The lowest muscle activity was found in the rectus
abdominis and ipsilateral internal oblique. All muscles

50
function together to stabilize the spine.12 Another
researcher focused on surface stability instead of muscle
stabilization.
Willardson et al researched surface stability and its
correlation to muscle activation and found different
results. Willardson et al focused on examining core muscle
activity on stable ground and on an unstable surface (BOSU
Balance Trainer). Twelve trained men volunteered for this
study. Four exercises were used to examine the muscle
activity. Five muscles were examined (the main core
muscles). The subjects were given the specific exercise and
were instructed to do the exercises at 50 % intensity on
stable and unstable surfaces. Then, the subject had to
perform the exercises at 75% intensity also on a stable
surface. There seemed to be no difference in muscle
activation in core muscles regardless of surface.13
While Willardson et al studied the five main core
muscles of the abdomen, Carpenter et al focused on four
abdominal muscles. Carpenter et al focused on how abdominal
muscles were coordinated with the activation of muscles
when introduced to unpredictable support surface. Twelve
male subjects with a range of the same general age was
utilized for the study. EMG data was recorded from the
right rectus abdominis, obliquus externus, obliquus

51
internus, and transversus abdominis. The participants were
to maintain their standing balance during forty support
surface translations. The rectus abdominis and obliquus
externus has earlier EMG onsets. The results provide
evidence on how the abdominal muscles contribute to
postural reactions.14
There was another study that was conducted on the
shoulder that received similar results. Illyés and Kiss
assessed muscle activity in multidirectional shoulder
instability. Fifteen subjects with multidirectional
shoulder instability were tested and the subjects were
instructed to perform four different tasks. Eight different
muscles were monitored. The time difference between the
peaks of normalized voluntary electrical activity is
greater than in the shoulders without instability.15
Hanada et al trunk muscle activation in older adults
with trunk stabilization was conducted. Twelve asymptomatic
adults with age ranges of 65 to 75 years were used for this
study. The subjects were instructed to perform maximal
voluntary isometric contractions for the EMG normalization
purposes. Abdominal Muscle activation was seen and was more
potent than the typical muscle contracture seen in the
younger population.16

52
Muscles Included in the Core
There are multiple muscles located in the body. Out of
those muscles, there are certain muscles that work
synergistically together to meet a certain muscle action.
The muscles also work together as stabilizers. They
function together to stabilize the spine and even assist in
maintaining posture during walking.11-12,17 If these muscles
do not work together then there is a possibility of the
athlete losing some strength when trying to complete a
specific action or it may be done improperly. The abdomen
consist of about five key muscles that work together to
help with trunk movement and for added stability in the
trunk.
There are about five main muscles that researchers
analyze when looking at core strength or core stability.
Four muscles can be located in the anterior view of the
body and those muscles are the Rectus Abdominis,
Transversus oblique, internal and external obliques.
These muscles mainly contribute to active flexion, Rectus
Abdominus, and rotational movement, the obliques. The last
muscle included in the core is the Erector Spinae. The
muscle is located posterior and elongates the entire spine.
This muscle’s main function is to provide back extension

53
and also to provide stability to the core as it works
synergistically with the rest of the abdominal muscles.

Core Stabilization Techniques and Exercises
There are multiple exercises that target the core
muscles that athletic trainers use in rehabilitation
programs. Knowing what exercises target what specific
muscles and knowing what instability changes could be made
to those exercises could allow for a more optimal
strengthening of the core muscles in athletes. Some
exercises focus on crunches which only work the muscles in
one plane of motion while other exercises require more
neuromuscular control and focuses on being multi-plane.
Strengthening the core muscles will not only allow the
athlete to get stronger but it also has the possibility of
providing better posture support, preventing low back pain,
and generally providing better athletic performance.
Parfrey et al examined abdominal muscle activation
with variation in trunk flexion positions. EMG data was
collected from the abdominal muscles, external oblique,
lower abdominal stabilizers, rectus femoris and biceps
femoris. Fourteen males were used for this study. The
variation contained three different variables. There was no
difference between the bent knee and extended leg sit up

54
positions. The bent knee sit up position produced higher
muscle activity in the lower abdominal stabilizers and the
rectus femoris.17 Bird et al focused away from stabilization
and more so on better ways to strengthen the abdominal
muscles.
Bird et al examined the difference in the abdominal
muscle activity in the AB-slide and the abdominal crunch.
Forty five subjects, thirty females and fifteen males,
volunteered for this study. The subjects performed five
exercise trials with the EMG attached to the upper rectus
abdominis, external oblique, and lower rectus abdominis.
During concentric movement, the external oblique and lower
rectus abdominus had high muscle activation. During
eccentric contractions, the rectus abdominis and external
oblique had higher muscle activity in the AB-slide.18
Escamillia et al also researched alternatives to help
strengthen the abdominal muscles rather than the
traditional abdominal crunch. Escamillia et al studied the
muscle activity between nontraditional sit-up and
traditional crunches with electromyography. Twenty-one
healthy men and women whose ages ranged between 23 and 43 years
recruited for this study. There were nine men and five females

with at least six months of resistance training. Anterior
and Posterior EMG muscle activity were the highest with the

55
nontraditional abdominal exercises. Lumbar paraspinal
muscle EMG activity was low for both exercises. Nontraditional abdominal exercises were more successful in
muscle activation and extraneous abdominal exercises.19
Petroksky et al also researched more efficient ways to
strengthen the abdominal muscles instead of standard
crunches.
Petrofsky et al examined the muscle use during core
body exercise using a mini stability ball compared with
abdominal crunches. Three male and seven female subjects
were used with an age range of eighteen and thirty-five. The
EMG recorded above the abdominals and the low back muscles.
Three levels of core exercises were tested. It showed that
the mini ball required 50 % more muscle activity in
comparison to standard crunches.20
Moreside et al also found similar results when
introducing the athlete to an exercise that focuses on
stabilization and perturbations. Moreside et al analyzed
trunk muscle activation patterns, spin kinematics, and
lumber compressive forces that occur when using the
Bodyblade . Fourteen healthy male subjects volunteered for
the study. The electromyography was placed on the trunk and
shoulder. With the utilization of the Bodyblade , the
greatest muscle activation was located in the internal and

56
external oblique muscles. The Bodyblade

can enhance or

compromise the spine stability.21
Huang et al found similar results pertaining to a
possible compromise in spine stability when introduced to
perturbations. Huang et al examined possible performance
changes in posture due to translations. Eight normally
active males were used for this experiment. The researches
added perturbations to test that hypothesis. The patients
were translated left and right randomly and also given
certain task. When the perturbation was applied, decreased
efficiency in posture was identified.22

Results/Findings
There has been a large amount of research that
examines the electrical activity of the core muscles. Even
more so, most researchers compare and analyze the scores by
using different surfaces. This is important because if the
subject can receive a more active participation of muscles
simply by inducing unstable surface change then that should
be included in every muscle training program. It is also an
easy alternative to increase muscle activity.
Marshall and Murphy examined the differences in
electromyographic activity in prime movers and the
abdominal muscle, while performing certain exercises, were

57
studied. Eight healthy subjects, eight male and four
females were used for this study. There was no difference
between muscle activity and surface for squats. However,
activity level of the triceps and abdominal was the highest
when performing push-ups on the Swiss Ball increases muscle
activity during exercises where the surface is unstable.23
Frannson et al analyzed vision and its capability to
have an effect on balance on foam surface. Eight healthy
subjects were used, eight males and four females. EMG
activity was monitored in the tibialis anterior and
gastrocnemius. The subjects repeated the trials with open
and closed eyes allowing the examiner to verify the effect
of vision on movement. Linear knee and hip movement
increased while on the foam. Vision stabilized shoulder and
head movement more than knee and hip on the foam surface.
Vision decreased tibialis anterior muscle activity on foam
surface.24
Imai et al focused on trying to determine whether
trunk activity changes with a change in surface. Nine
healthy males were used for this study and they have to
have a generally same body mass. The EMG measured the
muscle activity of the core and back muscles. Five
exercises were performed on stable and unstable surfaces.
With the elbow-toe exercises all muscles increased activity

58
on an unstable surface. The hand-knee and side bridge
exercises had an increase in activity of the more global
muscles on an unstable surface. The Curl-up exercise
increased the activity of the external obliques but
decreased the activity of the tranversus abdominis on the
unstable surface.25
Gatti et al analyzed the activation muscles used to
keep one leg raised from a supine position in healthy and
Multiple Sclerosis subjects. Fourteen healthy subjects,
with ages ranging from twenty eight to fifty six years were
utilized for this study. Greater activation of the biceps
femoris than abdominal muscles was located in the healthy
subjects for the A condition. The B condition had a
decrease between the two muscles. In the Multiple Sclerosis
patients, there was no difference with either condition. In
Multiple Sclerosis patients, there is an alteration in
stabilization muscles.26

Summary

The literature review detailed previous studies’
research of muscle activity during exercise. It is
important to find alternative methods to help strengthen
the core muscles. The core serves as a stabilizer,

59
assistance in gait, and also a key contributor to
strength.2,11,12,17 Research varied in terms of findings
regarding muscle activity when having the subjects balance
on a stable surface then compare the numbers to the
unstable surface. Others found there to be a significant
difference in the EMG activity occurring in certain muscles
on the unstable surface in comparison to the stable
surface. While some researchers focused on the surface
stability and its correlation to EMG activity, others
focused more on the surface conductivity of the electrodes
and the effects of different surfaces may have on EMG
reading. When doing the EMG reading, most of the examiners
monitored the five major muscles included in the core. Out
of the five muscles of the core, the rectus abdominus was
included in every study while other studies did not examine
all core muscles. When examining the muscles there were
multiple exercises utilized for the experiments to test the
different muscles. Every study had some EMG experiment that
distinguishes which muscles react the most to certain
increases in stress. However, none of the studies focused
on Yoga and its potential for supplying an alternative way
in strengthening muscles. The exercises most studies
focused on were primarily abdominal crunches, bench press,
sit-ups and bridging exercises.7-8,10-12,17-20,23

60

References
1.

Roy S, De Luca G, Cheng M, Johansson A, Gilmore L, De
Luca C. Electro-mechanical Stability of Surface EMG
Sensors. Med Biol Eng Compt. 2007;45(5):447-457.

2.

Jaggi A, Malone A, Cowan J, Lambert S, Bayley I,
Cairns M. Prospective Blinded Comparison of Surface
versus Wire Electromyographic Analysis of Muscle
Recruitment in Shoulder Instability. Physiotherapy Res
Intl: J Res Clinicians Phys Ther.2009;14(1):17-29.

3.

Alejandro Chaoul M, Cohen L. Rethinking Yoga and the
Application of Yoga in Modern Medicine. Cross Currents
[serial online]. June 2010;60(2):144-167. Available
from: Academic Search Complete, Ipswich, MA. Accessed
September 9, 2010

4.

Petrofsky JS, Cuneo M, Dial R, Morris A. Muscle
Activity during Yoga Breathing Exercise Compared to
Abdominal Crunches. J Applied Res. 2005;5(3):501-507.

5.

Prentice W. Arheim’s Principles of Athletic Training:
A Competency-Based Approach. New York, NY. McGrawHill; 2006: 101.

6.

Clark MA, Lurett SC. NASM’s Essentials of Sports
Performance Training. Baltimore, MD. Lippincott
Williams &Wilkens; 2010: 171-190.

7.

Norwood, J., G.S. Anderson, M. Gaetz, and P. Twist.
Electromyographic Activity of the Trunk Stabilizers
during Stable and Unstable bench Press. J Strength
Cond Res. 2007; 21(2)

8.

Marshall P, Murphy B. Increased Deltoid and Abdominal
Muscle Activity during Swiss Ball Bench Press. J
Strength Cond Res / Natl Strength Cond Assoc.
2006;20(4):745-750.

9.

Slijper H, Latash M. The Effects of Instability and
Additional Hand Support on Anticipatory Postural
Adjustments in Leg, Trunk, and Arm Muscles during
Standing. Exp Brain Res. Experimentelle Hirnforschung.
Expérimentation Cérébrale. 2000;135(1):81-93.

61
10.

Monfort-Pañego M, Vera-García F, Sánchez-Zuriaga D,
Sarti-Martínez M. Electromyographic Studies in
Abdominal Exercises: A Literature Review, J Manip
Physiol Ther. 2009;32(3):232-244.

11.

Stevens V, Bouche K, Mahieu N, Coorevits P,
Vanderstraeten G, Danneels L. Trunk Muscle Activity in
Healthy Subjects during Bridging Stabilization
Exercises. BMC Musculoskeletal Disorders. 2006;7:75.

12.

Stevens V, Vleeming A, Bouche K, Mahieu N,
Vanderstraeten G, Danneels L.Electromyographic
Activity of Trunk and Hip Muscles during Stabilization
Exercises in Four-Point Kneeling in Healthy
Volunteers. European Spine Journal: Official
Publication Of The European Spine Society, The
European Spinal Deformity Society, And The European
Section Of The Cervical Spine Research Society.
2007;16(5):711-718.

13.

Willardson J, Fontana F, Bressel E. Effect of Surface
Stability on Core Muscle Activity for Dynamic
Resistance Exercises. Intl J Sports Phys Performance.
2009;4(1):97-109.

14.

Carpenter M, Tokuno C, Thorstensson A, Cresswell A.
Differential Control of Abdominal Muscles during
Multi-Directional Support Surface Translation in Man.
Exp Brain Res. Experimentelle Hirnforschung.
Expérimentation Cérébrale. 2008;188(3):445-455.

15.

Illyés A, Kiss R. Electromyographic analysis in
Patients with Multidirectional Shoulder Instability
during pull, forward punch, elevation and overhead
throw. Knee Surgery, Sports Traumatology, Arthroscopy:
Official Journal Of The ESSKA. 2007;15(5):624-631.

16.

Hanada E, Hubley-Kozey C, McKeon M, Gordon S. The
Feasibility of Measuring the Activation of the Trunk
Muscles in Healthy Older Adults during Trunk Stability
Exercises. BMC Geriatrics.2008;8:33.

17.

Parfrey K, Docherty D, Workman R, Behm D. The Effects
of Different Sit- and Curl-up Postures on Activation
of Abdominal and Hip Flexor Musculature. Applied
Physiology, Nutrition, And Metabolism = Physiologie

62
Appliquée, Nutrition Et Métabolisme. 2008;33(5):888895.
18.

Bird M, Fletcher K, Koch A . Electromyographic
Comparison of the AB-Slide and Crunch Exercises. J
Strength Cond Res / Natl Strength Cond Assoc.
2006;20(2):436-440.

19.

Escamilla R, Babb E, DeWitt R, et al.
Electromyographic Analysis of Traditional and
Nontraditional Abdominal Exercises: Implications for
Rehabilitation and Training. Phys Ther.
2006;86(5):656-671.

20.

Petrofsky JS, Batt J, Davis N Core Muscle Activity
during Exercise on a Mini Stability Ball Compared with
Abdominal Crunches on the Floor and on a Swiss Ball. J
Appl Res. 2007;7(3) 255-272.

21.

Moreside J, Vera-Garcia F, McGill S. Trunk Muscle
Activation Patterns, Lumbar Compressive Forces, and
Spine Stability When Using the Bodyblade. Phys Ther.
2007;87(2):153-163

22.

Huang Q, Hodges P, Thorstensson. Postural Control of
the Trunk in Response to Lateral Support Surface
Translations during Trunk Movement and Loading. Exp
Brain Res. Experimentelle Hirnforschung.
Expérimentation Cérébrale. 2001;141(4):552-559.

23.

Marshall P, Murphy B. Changes in Muscle Activity and
Perceived Exertions during Exercises Performed on a
Swiss Ball. Applied Physiology, Nutrition, And
Metabolism = Physiologie Appliquée, Nutrition Et
Métabolisme. 2006;31(4):376-383.

24.

Fransson P, Gomez S, Patel M, Johansson L. Changes in
the Multi-Segmented Body Movements and EMG Activity
While Standing on Firm and Foam Support Surfaces.
European Journal Of Applied Physiology.
2007;101(1):81-89

25.

Imai A, Kaneoka K, Okubo Y, et al. Trunk Muscles
Activity during Lumbar Stabilization Exercises on Both
a Stable and Unstable Surface. J Orthop Sports Phys.
2010;40(6):369-375.

63
26.

Gatti R, Corti M, Govetto S, Bonzani K, Boccardi S.
Electromyographic Activity to Keep a Lower Limb in a
Raised Position in Healthy Subjects and Subjects with
Multiple Sclerosis. Multiple Sclerosis (Houndmills,
Basingstoke, England). 2008;14(5):691-693.

64

APPENDIX B
The Problem

65

THE PROBLEM

Statement of the Problem
There has been a generous amount of research conducted
that utilizes electromyography to evaluate muscle function
and also research has been found focusing on the
correlation of unstable surfaces and their affect on
certain muscles. During these experiments, the researchers
have been testing common exercises such as the chest press
or the push up.
In addition, there has been basic research on the
benefits of Yoga. Research in Yoga has previously been
performed and has found that Yoga is a healthy alternative
of exercise for not only the elderly but also individuals
who do not want to perform high impact exercises (i.e.
running).3 Yoga is becoming a popular exercise among the
young and the elderly. A minimal amount of research has
been initiated evaluating any EMG activity during Yoga
poses.
Yoga can be changed and altered based on an athlete’s
needs. Yoga also consists of multiple levels starting from
beginners and ending with expert. Yoga can be altered to
make the poses more dynamic in comparison to having static

66
poses. Yoga could be targeted toward a physical therapy
clinic and it could be applied in the athletic setting for
most ages. It has also been implied that Yoga has the
potential of decreasing psychological stress via endorphin
release during deep, controlled breathing.3,5
Therefore, the purpose of the study is to examine EMG
activity in the core muscle during static yoga poses on
stable and unstable surfaces. The inclusion of the core
muscles is important because Yoga has a tendency to include
poses that require multi-joint activity targeting the core
along with various other muscles. Using unstable and stable
surfaces allow the researcher to verify if the muscles
increase in activity during surface changes.

Definition of Terms
The following terms will be defined for this study:
1)

Balance – the ability to maintain an equal
distribution of weight

2)

Vrksasana – a yoga pose called the “tree pose”

3)

Paripurna Navasana – a yoga pose called the “boat
pose”

4)

Vasisthasa – a yoga pose called the “side plank”

5)

Physically active – an individual who has been doing
some form of cardiorespiratory exercise that raises

67
their heart rate to their target heart rate zone and
maintains that condition for a minimum of 30 minutes
at least 3 out of the 7 days of the week.
6)

Perturbations - the causation of disturbance of the
state of equilibrium.

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

The subjects will utilize their maximum effort to
maintain the poses.

2)

The subjects will maintain the proper form after
examiner shows subjects proper Yoga technique.

3)

The EMG equipment will be properly calibrated,
accurate and reliable during testing.

4)

The subjects accurately assess their physical activity
levels.

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

Only physically active subjects were utilized.

2)

The EMG machine can only measure superficial muscles
such as the rectus abdominus, external oblique and
erector spinae

68
3)

EMG signals have the potential to include signal from
unwanted muscles in the area of the target muscle.

4)

Subjects will have varying levels of knowledge about
Yoga.

5)

There was only a small sample sized used.

Delimitations of the Study
The following are possible delimitations of the study:
1)

The examiner chose three Yoga poses that had the
possibility of lacking in difficulty so that subjects
were capable of performing regardless of their fitness
levels.

2)

EMG activity will only be measured in four muscles.

Significance of the Study
The study showed what muscles in the core, if any,
increase in activity when being subjected to instability.
The study had the potential of allowing three new
exercises, targeting the core, to be utilized in the
clinical setting. The three Yoga exercises chosen for the
study were only a minuscule amount compared to the various
range of exercises. There were also Yoga poses that
targeted different muscle groups based on anecdotal
reasoning.

69
Yoga potentially allowed for the athletic trainers and
any other health care professional looking to utilize Yoga
as a strengthening tool, to have a variety of strengthening
exercises. The exercises showed no significant increase in
muscle activity when introduced to instability compared to
a stable surface. Although there the study showed no
significant increase, there was evidence that Yoga provided
an alternative way of strengthening the core. The muscle
activity during the three Yoga poses reached 100% of the
muscles’ maximal voluntary contraction.
Yoga is also a cost effective way to strengthen
muscles compared to exercise equipment. Therefore, if an
athletic trainer works in a setting that contains little to
no equipment, he or she can have the athletes strengthen
their muscles through Yoga. In addition, Yoga potentially
targets the cardiovascular system by adding dynamic
movement. Athletic Trainers and health care professionals
can strengthen muscles while improving an athlete’s
cardiovascular fitness. The time spent working with an
athlete when targeting those categories separately can be
reduced by doing Yoga exercises. Yoga also requires the
athlete to have fine balance skills which is critical in
most sports. Yoga not only can strengthen the core, it has
the potential of being more cost effective than machinery,

70
targets the cardiovascular system and helps athletes
improve balance and coordination.
Yoga can possibly be utilized by ATCs and other health
care professionals as an additional “tool” in their
“toolbox” to strengthen the core. However, ATCs and health
care professionals need to be aware of the potential
differences in muscle activity based on previous physical
activity. The muscle activity could potentially increase
significantly in a subject that runs for exercise. Subjects
who practice weight lifting may potentially have little to
no increase in muscle activity during Yoga. In addition,
muscle activity can appear sporadic based on subject
experience and knowledge of Yoga.
Athletic trainers have an abundance of exercise
equipment and exercises to choose from when creating
exercise programs. The three Yoga poses could potentially
be included in these wide ranges of choices. With the
possible addition of the three Yoga poses, athletic
trainers could provide a variety in an exercise program. In
turn, the athlete could be further challenged with Yoga.
Despite the lack of significance in the study, Yoga has the
potential of opening a new door in providing new ways to
strengthen the core in the physically active population.

71

APPENDIX C
Additional Methods

72

APPENDIX C1
Institutional Review Board –
California University of Pennsylvania

73

74

75

76

77

78

79

80

81

82

83

84

85

86

APPENDIX C2
Informed Consent Form

87

Informed Consent Form
1. Elizabeth Banks, 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 EMG OF THE CORE MUSCLES
DURING STATIC YOGA POSES ON STABLE AND UNSTABLE SURFACES.
2. I have been informed that the purpose of this study is to examine EMG activity of
various muscles during static Yoga poses on stable and unstable surfaces. I understand
that I must be 18 years of age or older to participate. I understand that I have been asked
to participate since I perform steady exercises at least three times a week for at least thirty
minutes. In addition, I understand subjects cannot have an inner ear infection, vertigo,
stability issues, weak joints that pose instability problems or any balance problems.
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 a 5 minute warm-up session and then
participating in the 10 minute exercise program. I have been informed of the possible
risks and benefits of my participation. Subjects have the option of resigning from the
study without any repercussions.
The 5 minute warm-up session will require me to warm-up on an elliptical trainer for one
minute to warm the muscles. Following the 1 minute warm-up, I will then perform three
various Yoga steps called Sun Salutations. Then I will proceed to the 10 minute exercise
protocol. Prior to beginning the protocol, the researcher will place adhesive electrodes on
my skin, over the rectus abdominus, external abdominal oblique and erector spinae to
measure the electrical activity during the yoga poses.
With the electrodes in place, I will be instructed to start performing yoga poses, holding
the each of the 3 poses for 15 seconds. As I maintain each Yoga pose, the examiner will
document the peak activity of each muscle as measured by the electrodes. I will perform
each pose on a stable surface first then proceed to perform the same pose on an foam pad
and or BOSU ball to create a less stable surface. I will be given a 30 second rest period
between each pose. I will then do the second assigned pose, then the third assigned pose
on both stable and unstable surfaces. This process with be repeated for 2 additional trials
for a total of 9 poses being held. During the second and third trial run, the exact same
procedures will be followed. Once all three trials are completed and documented, I will
be recommended to do a 5 minute cool down that consist of stretching the lower and

88
upper extremity on my own time to minimize the chance of muscle soreness. After the
experiment, I am free to leave.
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.
Potential risks are loss of balance and the possibility of strains and sprains. In order to
minimize these risks, the examiner trusts my word that I have no balance issues, vertigo,
ankle instability, or that I do not take any medications that have the potential of
decreasing balance, increasing dizziness or impairing vision. The researcher will be in
close proximity during all performed exercises on both surfaces to limit the chances of a
fall and to provide care should I become injured. If I become pregnant during the study, I
understand that I have the choice to continue or discontinue my participation in the study
at me and my child’s discretion.
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,
Elizabeth Banks, 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.
6. There are no feasible alternative procedures available for this study.
7. I understand that the possible benefits of my participation in the research is to help
determine EMG activity in the core muscles during Yoga poses on stable and unstable
surfaces. This study will provide athletic trainers and other health care professionals with
other means to strengthen the core muscles and general physical fitness for the physically
active and athletic population.
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, Elizabeth Banks 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:
Elizabeth Banks
STUDENT/PRIMARY RESEARCHER

89
Ban4961@calu.edu
804-896-0262
Thomas F. West,
RESEARCH ADVISOR
West_t.calu.edu
724-938-5933
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: 03/18/11 to 03/17/12.

Subject's
signature:___________________________________Date:____________________
Witness
signature:___________________________________Date:____________________

90

Appendix C3
Demographic Information

91
Demographic Information
Age: __________________________
Year/school: __________________
Gender:

male or female

Are you taking any medication: Yes or No
If yes, what are the side effects: _______________________
Do you have unstable or weak ankles? Yes or No
Do you have an inner ear problem? Yes or No
Do you experience vertigo? Yes or No
How many times do you exercise a week? How Long?
_______________________________
Do you have any knowledge about Yoga? Yes or No

92

Appendix C4
Yoga Poses

93

Figure 1. Yoga Poses, Tree Pose, Boat Pose, Side
Plank Pose, on stable and unstable conditions

94

95

REFERENCES
1.

Roy S, De Luca G, Cheng M, Johansson A, Gilmore L, De
Luca C. Electromechanical Stability of Surface EMG
Sensors. Medical & Biological Engineering & Computing.
2007;45(5):447-457.

2.

Jaggi A, Malone A, Cowan J, Lambert S, Bayley I,
Cairns M. Prospective Blinded Comparison of Surface
versus Wire Electromyographic Analysis of Muscle
Recruitment in Shoulder Instability. Physiotherapy
Research International: The Journal For Researchers
And Clinicians In Physical Therapy. 2009;14(1):17-29.

3.

Alejandro Chaoul M, Cohen L. Rethinking Yoga and the
Application of Yoga in Modern Medicine. Cross Currents
[serial online]. June 2010;60(2):144-167. Available
from: Academic Search Complete, Ipswich, MA. Accessed
September 9, 2010

4.

Prentice W. Arheim’s Principles of Athletic Training:
A Competency-Based Approach. New York, NY. McGrawHill; 2006: 101.

5.

Clark MA, Lurett SC. NASM’s Essentials of Sports
Performance Training. Baltimore, MD. Lippincott
Williams & Wilkens; 2010: 171-190.

6.

Norwood, J, GS Anderson, M Gaetz, and P Twist.
Electromyographic Activity of the Trunk Stabilizers
during Stable and Unstable bench Press. J. Strength
Cond. Res. 2007; 21(2)

7.

Marshall P, Murphy B. Increased Deltoid and Abdominal
Muscle Activity during Swiss Ball Bench Press. Journal
Of Strength And Conditioning Research / National
Strength & Conditioning Association. 2006;20(4):745750.

8.

Slijper H, Latash M. The Effects of Instability and
Additional Hand Support on Anticipatory Postural

96
Adjustments in Leg, Trunk, and Arm Muscles during
Standing. Experimental Brain Research. Experimentelle
Hirnforschung. Expérimentation Cérébrale.
2000;135(1):81-93.
9.

Monfort-Pañego M, Vera-García F, Sánchez-Zuriaga D,
Sarti-Martínez M. Electromyographic Studies in
Abdominal Exercises: A Literature Review, Journal Of
Manipulative And Physiological Therapeutics.
2009;32(3):232-244.

10.

Stevens V, Bouche K, Mahieu N, Coorevits P,
Vanderstraeten G, Danneels L. Trunk Muscle Activity in
Healthy Subjects during Bridging Stabilization
Exercises. BMC Musculoskeletal Disorders. 2006;7:75.

11.

Stevens V, Vleeming A, Bouche K, Mahieu N,
Vanderstraeten G, Danneels L. Electromyographic
Activity of Trunk and Hip Muscles during Stabilization
Exercises in Four-Point Kneeling in Healthy
Volunteers. European Spine Journal: Official
Publication Of The European Spine Society, The
European Spinal Deformity Society, And The European
Section Of The Cervical Spine Research Society.
2007;16(5):711-718.

12.

Willardson J, Fontana F, Bressel E. Effect of Surface
Stability on Core Muscle Activity for Dynamic
Resistance Exercises. Intl J Sports Phys Performance.
2009;4(1):97-109.

13.

Carpenter M, Tokuno C, Thorstensson A, Cresswell A.
Differential Control of Abdominal Muscles during
Multi-Directional Support Surface Translation in Man.
Experimental Brain Research. Experimentelle
Hirnforschung. Expérimentation Cérébrale.
2008;188(3):445-455.

14.

Illyés A, Kiss R. Electromyographic analysis in
Patients with Multidirectional Shoulder Instability
during pull, forward punch, elevation and overhead
throw. Knee Surgery, Sports Traumatology, Arthroscopy:
Official Journal Of The ESSKA. 2007;15(5):624-631.

15.

Hanada E, Hubley-Kozey C, McKeon M, Gordon S. The
Feasibility of Measuring the Activation of the Trunk

97
Muscles in Healthy Older Adults during Trunk Stability
Exercises. BMC Geriatrics.2008;8:33.
16.

Parfrey K, Docherty D, Workman R, Behm D. The Effects
of Different Sit- and Curl-up Postures on Activation
of Abdominal and Hip Flexor Musculature. Applied
Physiology, Nutrition, And Metabolism = Physiologie
Appliquée, Nutrition Et Métabolisme. 2008;33(5):888895.

17.

Bird M, Fletcher K, Koch A . Electromyographic
Comparison of the AB-Slide and Crunch Exercises.
Journal Of Strength And Conditioning Research /
National Strength & Conditioning Association.
2006;20(2):436-440.

18.

Escamilla R, Babb E, DeWitt R, et al.
Electromyographic Analysis of Traditional and
Nontraditional Abdominal Exercises: Implications for
Rehabilitation and Training. Phys Ther.
2006;86(5):656-671.

19.

Petrofsky JS, Batt J, Davis N Core Muscle Activity
during Exercise on a Mini Stability Ball Compared with
Abdominal Crunches on the Floor and on a Swiss Ball.
The Journal of Applied Research. 2007;7(3) 255-272.

20.

Moreside J, Vera-Garcia F, McGill S. Trunk Muscle
Activation Patterns, Lumbar Compressive Forces, and
Spine Stability When Using the Bodyblade. Physical
Therapy. 2007;87(2):153-163

21.

Huang Q, Hodges P, Thorstensson. Postural Control of
the Trunk in Response to Lateral Support Surface
Translations during Trunk Movement and Loading.
Experimental Brain Research. Experimentelle
Hirnforschung. Expérimentation Cérébrale.
2001;141(4):552-559.

22.

Marshall P, Murphy B. Changes in Muscle Activity and
Perceived Exertions during Exercises Performed on a
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ABSTRACT
Title:

Electromyographic Activity in Core Muscles
During Static Yoga Poses Performed on Stable
And Unstable Surfaces

Researcher:

Elizabeth M. Banks, BS, PES

Advisor:

Thomas F. West, PhD, ATC

Type:

Thesis

Context:

Yoga has become a popular form of exercise
in the young and elderly. Yoga encompasses
core strength which is beneficial for most
sports and everyday activity. Yoga requires
balance and stabilization which requires
motor unit recruitment which increases
strength. Despite these benefits, there has
been minimum research on Yoga.

Objective:

To determine if electromyographic activity
in three core muscles increases during
static Yoga poses on unstable surfaces than
stable surfaces with p≤0.05.

Design:

Quasi-experimental, within subjects,
repeated measures design.

Setting:

Controlled, laboratory setting.

Patients or Other Participants:
Seventeen (5 males, 12 females) physically
active, college aged participants with no
history of an inner ear infection, vertigo,
stability issues, and weak joints.
Intervention:

Three Yoga poses by the examiner based on
perceived difficulty (beginner,
intermediate, expert). The pose and surface
order were selected via counterbalanced
random assignment. Poses were performed on
solid ground, a BOSU ball, and a foam disk
on the dominant side. Muscle activity was
recorded via a MP150 amplifier with wired
telemetry unit connected to a PC running
Biopac Acknowledge 4.0 software. Muscle

100
activity was compared to the percentage of
the maximal voluntary contraction (%MVC).
The average of 2 trials for each completed
pose and surface were used for analysis.
SPSS version 18.0 for windows using a
factorial repeated measures analysis of
variance determined the significance of the
muscle activity.
Main Outcome Measures:
Core muscle activity was compared to the
respective MVC percentage.
Results:

The interaction between surface condition,
pose and muscle was not significant
(F(4,64)=.626, p=.646). The main effect for
surface for the rectus abdominus, external
oblique, and erector spinae were not
significant respectively (F(1,16)=1.149,
p=.300), (F(1,16)-.001, p=.977),
(F(1,16)=.923, p=.351).The main effect for
pose for the rectus abdominus, external
oblique and erector spinae were not
significant respectively (F(2,32)=1.879,
p=.169), F(2,32)=1.787, p=.184),
(F(2,32)=.823, p=.448). The interaction
between surface and pose was not significant
for the rectus abdominus, external oblique,
and erector spinae respectively
(F(2,32)=2.018, p=.150), (F(2,32)=2.008,
p=.151), (F(2,32)=1.409, p=.259). This
indicated that pose, surface, and pose and
surface had no effect on the muscle activity
in any of the three muscles.

Conclusions:

Yoga has stress relieving benefits, is cost
effective, low impact and can be practiced
by any age group. Even without significant
findings, Yoga is still an effective tool
that can be used by Athletic Trainers and
other health care professionals to help
strengthen muscles. Yoga has the capability
of activating one hundred percent of the
core muscles maximal volitional contraction
regardless of surface or pose difficulty.