A CORRELATION AMONG CORE STABILITY, CORE STRENGTH, CORE
POWER, AND KICKING VELOCITY IN DIVISION II COLLEGE SOCCER
ATHLETES

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
Atsuko Takatani

Research Advisor, Dr. Rebecca Hess
California, Pennsylvania
2012

ii

iii

ACKNOWLEDGEMENTS

First, I would like to thank you to my thesis
committee chairperson, Dr. Rebecca Hess. She has helped and
guided me on my path to completion of this thesis. I cannot
thank her enough for all of the time she spent reviewing my
work and encourage me of this difficult topic from the
beginning. She has helped me to think deeper and work
consistently, which helped shape this thesis. Thanks to my
thesis committee members, Dr. Hargraves and Mr. Daley, for
all of their knowledge, input and encouragement, which
helped strengthen my work. This would not have been
possible without all of their help.
Special thanks to Coach Dennis Laskey, Emedin Sabic,
and the California University of Pennsylvania men’s soccer
athletes for taking part in my study. I enjoyed working
with all of the coaches and athletes and had great memories
through the season. Sincere thanks to Sarah Beaulieu for
being a wonderful roommate and a peer researcher.
I also thank all my classmates, faculty, coaches, and
students at California University of Pennsylvania for their
support and a fun year.
Finally, I thank to my parents, Toshihiro and Kyoko,

iv

for always supporting me and understanding my desire to
complete my Master of Science Degree and my love of working
as an athletic trainer. I appreciate all the help. I also
thank to my twin sister, Yuko, and my grandma, Hisako for
their support and words of encouragement. I strived to make
them proud of the work I did; they were my motivation to
succeed.

v

TABLE OF CONTENTS
Page
SIGNATURE PAGE

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

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

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

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

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

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

Research Design
Subjects

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

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

Preliminary Research. . . . . . . . . . . . . 7
Instruments . . . . . . . . . . . . . . . . 8
Procedures

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

Hypothesis

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

Data Analysis
RESULTS

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

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

Demographic Data . . . . . . . . . . . . . . 21
Hypothesis Testing

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

Additional Findings . . . . . . . . . . . . . 24
DISCUSSION . . . . . . . . . . . . . . . . . 26
Discussion of Results . . . . . . . . . . . . 26
Conclusions . . . . . . . . . . . . . . . . 34
Recommendations. . . . . . . . . . . . . . . 35

vi

REFERENCES . . . . . . . . . . . . . . . . . 37
APPENDICES . . . . . . . . . . . . . . . . . 39
APPENDIX A: Review of Literature

. . . . . . . . 40

RE VIEW OF LITERATURE . . . . . . . . . . . . . 41
Review of the Core

. . . . . . . . . . . . . 41

Anatomy of the Core . . . . . . . . . . . 42
Core Stability

. . . . . . . . . . . . . 45

Core Strength . . . . . . . . . . . . . . 47
Core Endurance

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

Core Power . . . . . . . . . . . . . . . 49
Assessment of Core Function . . . . . . . . . . 50
Isokinetic Dynamometer for Strength and Work
Sahrmann’s Test for Core Stability

. . 51

. . . . . . 52

McGill Test for Strength and Endurance . . . . . 54
Double Leg Lowering Test for Core Strength . . . 56
60s Maximal Sit Up Test for Core Power . . . . . 57
The Role of the Core in Athletic Performance . . . 58
Core Stability Exercise and Athletic Performance . 59
Core Stability and Athletic Performance

. . . . 61

Core in Soccer Kicking . . . . . . . . . . . 66
Summary . . . . . . . . . . . . . . . . . 68
APPENDIX B: The Problem . . . . . . . . . . . . 70
Statement of the Problem . . . . . . . . . . . 71

vii

Definition of Terms . . . . . . . . . . . . . 72
Basic Assumptions . . . . . . . . . . . . . . 73
Limitations of the Study . . . . . . . . . . . 73
Significance of the Study

. . . . . . . . . . 74

APPENDIX C: Additional Methods . . . . . . . . . 75
Informed Consent Form (C1) . . . . . . . . . . 76
Subject Information/Individual Data
Collection Sheet (C2) . . . . . . . . . . . . 80
IRB: California University of Pennsylvania (C3) . . 82
Pictures: Equipment (C4) . . . . . . . . . . . 98
Pictures: Rotary Stability Test (RS) (C5)

. . . . 102

Pictures: Double Leg Lowering Test (C6) . . . . . 105
Pictures: 60s Maximal Sit Up Test (C7)
Testing Directions (C8)

. . . . . 108

. . . . . . . . . . . 111

REFERENCES . . . . . . . . . . . . . . . . . 115
RABSRTACT

. . . . . . . . . . . . . . . . . 120

viii

LIST OF TABLES

Table

Title

1

Demographic Data . . . . . . . . . . . . 22

2

Descriptive statistics for RS, DLLT,
60sMSUT and SK

Page

. . . . . . . . . . . . 23

3

Correlations among RS, DLLT, 60sMSUT and SK

4

Descriptive statistics for TSPU . . . . . . 25

5

Correlations among TSPU, RS, DLLT,
60sMSUT, and SK

. 24

. . . . . . . . . . . . 25

1

INTRODUCTION

The correlation between core stability and athletic
performance has not been determined in the available
literature. Although several researchers have attempted to
quantify the relationship between core stability/strength
and functional performance, recent findings suggest that
further research is needed to investigate important
components and measurement of core stability in relation to
athletic performance.1,2 Therefore, the primary purpose of
this study was to examine the relationship among core power,
core strength, core stability, and athletic performance in
college soccer athletes. It is important to examine the
correlation to assess core power and its effect on athletic
performance because core power is an integrated component
of core stability, strength and endurance during dynamic
movement.1
In addition to the lack of current scientific evidence
to support the correlation between core function and
athletic performance, a valid core assessment has not been
established yet. Therefore, the secondary purpose of this
study was to establish a valid assessment tool of core. It

2

would be beneficial to clarify the definition of core power,
as a component of core stability, and its effect on
performance in the field of sports science.
Recently, two research groups1,3 investigated the
relationship between core stability and athletic
performance in a sports specific manner. These researchers
assumed that selecting core tests that are specific to
performance capabilities is a key to investigate the
relationship between two variables successfully. By
estimating the tests of core stability that have similar
movement patterns of the specific athletic performance,
researchers were able to analyze the core muscular
contributions in dynamic movement. Wagner3 and Dendas1
successfully observed the relationship between the function
of the core and athletic performance; although their
conclusions conflicted within the context of core stability
and its effect on athletic performance.
Dendas1 investigated the relationship between athletic
performance and core stability in Division II football
players. Athletic performance included 3-repetition
maximums for the power clean, back squat, and bench press,
as well as vertical jump height, and 40m sprint time with a
20m split time.1 Findings showed a significant relationship

3

among athletic performance, 60s and 30s maximum sit-up
tests, and the McGill trunk flexion test. While it was
hypothesized that the Ball Explosive Sit-up Throw Test
(MBESTT) would show a significant relationship to the core
power, scores on the MBESTT were not related to scores on
any of the other measures of core stability.1 The researcher
stated that “a 30-second or 60-second sit-up test is the
best field test of core stability currently available”1(p79)
in measuring athletic performance in collegiate football
players.
Wagner3 identified the relationship between core
fitness and tests of soccer sport performance in female
soccer players. The researcher defined core fitness as “the
combination of isometric core stability and concentric core
strength to perform a task of sport performance.”3(p8)
According to the researcher, isometric core strength (ISC)
was used to evaluate the ability of the core to provide a
stable base of support using the trunk flexion and bilateral rotation core strength test, while concentric
functional core strength (CFCS) was used to evaluate the
ability of the core to produce and transfer forces to the
limbs using the front abdominal power test (FAPT) and side
abdominal power test (SAPT). The researcher compared these

4

two types of core tests with the soccer-style standing kick
and throw-in for maximum speed to examine the role of core
function on soccer athletic performance. Results indicated
that ICS correlated more strongly with tests of soccer
sport performance than CFCS. These findings conflicted with
other studies and rejected the research hypothesis.3 The
researcher assumed that ICS elicited a greater muscular
activation due to a larger load placed on the core, which
could have resulted in a greater correlation with tests of
soccer athletic performance.3
In comparing these studies, Dendas’ findings suggested
that core power has a greater contribution to athletic
performance in football player than ICS. On the other hand,
Wagner’s finding suggested that ICS has a greater
contribution to soccer performance (standing kick and
throw-in) than CFCS. Although both researchers have
established valid assessments of core and athletic
performance, their findings leave the question, which type
of core function has a greater contribution to athletic
performance? In other words, is it necessary to assess core
stability with a test involving limb movements
(specifically of the upper and/or lower extremity) in order

5

to identify the contribution of core to athletic
performance (involving upper and/or lower extremity)?
Theoretically, the core musculature is the kinetic
link between the lower and upper bodies and should have
direct influence on the kinetic chain on athletic
performance. Thus, the purpose of the present study was to
examine whether the core has a significant role in
providing a base of support for optimal lower extremity
function, and the ability to produce and transfer force to
the distal segments during a functional soccer task,
specifically maximal kicking velocity. Findings may help to
generate a valid means of assessing core stability on a
base of all core functions, and may be able to guide future
studies testing sport performance with the use of core
training.

6

METHODS

This section includes the following subsections: research
design, subjects, instruments, procedures, hypotheses, and
data analysis.

Research Design

A correlational design was used to determine whether
core stability (Rotatory Stability test), core strength
(the Double Leg Lowering test) and core power (60s Maximum
Sit-Up test) are related to soccer performance (kicking
speed). Subjects performed the Functional Movement Screen
(FMS) as their warm up, which was conducted by a peer
researcher who is a certified FMS specialist. A limitation
of the study is the inability to generalize the results
beyond DII male soccer players.

Subjects

The subjects were volunteer male student athletes from
California University of Pennsylvania’s (NCAA Division II)
soccer team (n~20). The subjects had some familiarity with

7

the testing protocols; core training and soccer style
kicking as the result of collegiate team participation and
training. Subjects needed to be actively participating
and/or competing with the varsity soccer team at the time
of testing. All subjects in the study read and signed an
Informed Consent Form (Appendix C1) prior to participation
in the study. Subject information and data collection were
contained and documented by the researcher (Appendix C2).
Each participant’s identity remained confidential and was
not included in the study.

Preliminary Research

Preliminary research was performed prior to beginning
the research study. The researcher conducted trials with
the core tests; the 60s Maximum Sit-Up test (60s MSUT), the
Double Leg Lowering test (DLLT), and the soccer kicking
test (SK) to become familiar with the equipment, determine
a time frame for testing sessions, and identify any
modifications that were made to the testing procedures. All
test directions were provided using the same text (Appendix
C8). The researcher was familiar with the equipment
including; sphygmomanometer; 360º universal goniometry and

8

JUGS™ radar gun. These preliminary trials were conducted on
two physically active students within the same age-range as
the desired subjects.

Instruments

The instruments used in this study were a Subject
Information Sheet/ Data Collection Sheet (Appendix C2), the
Rotary Stability Test (FMS 2x6in board), the 60s MSUT, the
DLLT (sphygmomanometer and 360º universal goniometer), and
the SK (JUGS™ radar gun)(Appendix C4).

Subject Information/Data Collection Sheet
Demographic information was collected on a Subject
Information/Data Collection Sheet (Appendix C2). The sheet
included questions regarding: (a) date of birth (age), (b)
type of kick used, (c) kicking leg, and(d) years of soccer
experience, (e) position.

Rotary Stability Test (RS)
The RS is one of seven tests used to test functional
movement by the Functional Movement Screen (FMS),4 and was
used to grade core stability. The FMS is an assessment tool

9

comprised of seven different movements to identify
asymmetry and dysfunctions of movement pattern within the
body. This RS test consists of multi-plane trunk stability
during a combination of asymmetric upper and lower
extremity movement, which requires proper neuromuscular
coordination and energy transfer through the trunk
(Appendix C5). Not only has the FMS been widely used, but
the reliability of the FMS has been reported to have an
intraclass correlation coefficient (ICC) value of 0.98.5 The
range of scores for each test on the FMS are from zero to
three; three being the best possible score.4 A score of
three is given if the subject performs the movement of RS
correctly without any compensation (Appendix C5-Figure 4).
A score of two is given if the person is able to complete
the movement with compensation (Appendix C5-Figure 5). If
the requirements for a score of two are not met, then a
score of a 1 is given (Appendix C5-Figure 6). If there is
pain with the movement, a final score of a zero will be
given for the RS test.

Double Leg Lowering Test (DLLT)
The modified double leg-lowering test was used to
grade core strength (Appendix C6). The test was adopted

10

from Zingaro’s study.6 The lower the subject can lower the
legs correlates to a stronger core.6-8 The degree from
starting point (hip flexed to 90º)to ending point was used
for data analysis. A blood pressure cuff was used to
measure the pressure under the back during the DLLT. A 12inch, 360º degree universal goniometer was used to measure
the angle of hip flexion during the core strength testing.
The angle of hip from 90º of hip flexion was measured with
a goniometer when the pressure of the sphygmomanometer
dropped below 20mmHg.6,9 This is unlike the double leglowering test, which takes a measurement at 40 mmHg. The
DLLT has been found to be reliable; the ICC for repeated
measures of the DLLT was 0.98.7 Core strength was
interpreted by the hip angle at the time of pressure change
where a greater angle indicated greater core strength. An
average score of three trials was used for data analysis.6
The verbal directions for the test are described in
Appendix C8.

60s Maximum Sit-Up test (60s MSUT)
Core power was measured by the maximum sit-ups in 60
seconds. The 60s MSUT was adopted from similar tests
described by Dendas.1 Reliability for the timed sit-up tests

11

have previously been established.1,10 Dendas reported that
test-retest reliability coefficients for 60s timed sit-up
test was statistically significant (r = 0.862 ).1 Augustsson
et al10 also reported an ICC of 0.93 with a 95% confidence
interval of 0.77.10 Each up-down cycle was counted as a
successful repetition of the sit-up. The subject had to
flex the trunk up until the elbows touched the thighs and
then lower the trunk back until the scapulae came into
contact with the floor for a successful sit-up. The test
was scored as maximal number of correct sit-ups within the
60-second time period.1,10 Higher numbers of repetitions
indicates better core power. Subjects only performed one
sit-up trial per testing session.1 The lengthy in depth
directions of the test are described in Appendix C8.

Soccer Kicking Test (SK)
Prior to kicking assessment, the subjects performed a
series of dynamic warm-up exercises adapted from Wagner’s
study.3 The warm-up consisted of two laps of jogging, 10
yards of hip external rotation, forward lunges, backward
lunges, lateral squat, high knees, butt kickers, side
shuffle, Carioca, A-skip, power skip, and straight leg kick
followed by the leg swing to front/back and side to side in

12

place. The subjects started with two laps of jogging from
the start point, and then were instructed dynamic warm up
at the station where the corns were set up for the dynamic
warm-up.3 After performing the leg swing by the fence, the
subjects had kicking/passing warm-up with the partner for
five minutes.11,12 Soccer performance was evaluated with a
dynamic soccer-style kick for maximal speed. The speed of a
dynamic instep, toe kick or shoelace kick (top of the foot)
while attempting to kick a dead ball as hard as possible
was used to seek the dynamic stability of the core in the
current study.3 The maximum kicking velocity (meters per
second, m/s) was assessed with use of the JUGS™ radar gun
(Jugs Sports, Tualatin, OR), which was placed behind the
soccer goal. The ball was placed 5m from where the ball was
struck.11,12 The radar gun is a good instrument to measure
soccer kicking velocity.11 According to Sedano et al,11 the
speed of soccer kicking measured by radar and the
measurement protocol was validated by a photogrammetry
system. A value of Rxy = 0.998 was obtained in this study.11
According to Sedano et al,12 there was a positive
correlation (rxy = 0.994, p < 0.05) between the maximal
kicking speeds registered by the radar gun and those
recorded by high speed video camera. The JUGS™ radar gun

13

has a reported accuracy of ±0.4 display unit and range of
speeds of 40-200kph.13 Using a radar gun to measure the
soccer kicking velocity has been reported reliable.12 The
radar gun was calibrated by manufacture instruction prior
to the study.13 A standard size five soccer ball was used
for the test. Higher speeds indicated better kicking
performance in this case. The subjects had two practice
trials. Average of three kicks after the practice trials
was recorded.

Procedures

Once approved by the Institutional Review Board at
California University of Pennsylvania (Appendix C3), the
study took place over a 3-day period which consisted of an
orientation meeting with a practice trial of each test on
Day 1 and two testing days, Day 2 and 3. Orientation and
testing were conducted at the Phillipsburg soccer complex
at California University of Pennsylvania.
On Day 1, the researcher had a meeting with all
potential subjects and explained the concept of the study
and offered the Informed Consent Form (Appendix C1) in
order for them to understand the requirements and risks of

14

involvement in the study. Qualifications for the subjects
(mentioned in the subject section), requirements, testing
date (approximately 7 days later), and approximate time
frame for entire study, 20 minutes on each of the two
testing days, were announced. Then the subjects, who met
the qualifications, had a practice session for all core
tests.
All subjects, who met the qualifications, were asked
to participate in the rest of the study. Day 2 consisted of
a warm up using the FMS and measurement of two core
assessments. Prior to the core testing session, the
subjects performed the FMS assessed by a peer researcher
who is a certified FMS specialist. The following testing
were performed in the following order; Core stability test
(RS as a part of the FMS); Core strength test (DLLT); Core
power test (60s MSUT).

Day 3 consisted of a series of

dynamic warm ups and soccer performance assessment (SK).

Warm Up 1: Functional Movement Screen (FMS)
The following seven tests for the FMS served as the
warm-up for the core testing and were conducted by a peer
researcher who possesses the FMS certification. The
assessment variables included: (1) Deep Squat; (2) Hurdle

15

Step; (3) In-line Lunge; (4) Shoulder mobility; (5) Active
Straight Leg Raise; (6) Trunk Stability Push Up; (7)
Rotatory Stability (RS).4 Scores of the RS were used as the
assessment of core stability in the current study.

Rotatory Stability Test (RS) for Core Stability
For the RS, the subject was in a quadruped position
with shoulders and hips at 90º relative to the torso with
the FMS kit, a 2x6 in board (Appendix C4-Figure 1),
parallel to the spine in between the hands and the knees.
The ankles were in a dorsiflexed position. The subjects
then flexed the shoulder while extending the same-side hip
and knee, and then slowly brought the elbow to the sameside knee while remaining in line over the board. For a
score of a 3 on the RS, the subject must perform the task
correctly using the same-side leg and arm while keeping the
torso parallel to the FMS kit board and keeping the elbow
and knee in line with the FMS kit board (Appendix C5-Figure
4). A score of a 2 was given, the subject performed a
diagonal pattern using the opposite shoulder and hip in the
same manner as for a score of a 3 (Appendix C5-Figure 5).
The knee and opposite elbow had to make contact over the
FMS kit. If the requirements for a score of a 2 were not

16

met, then a score of a 1 was given (Appendix C5-Figure 6).
If there was pain with the movement, a final score of a
zero was given for the RS test. The researcher viewed the
movement from the side of the subject. After completing the
FMS, the subjects moved to the core testing session. All
subjects performed the core tests in the following order;
DLLT; 60s MSUT.

Double Leg Lowering Test for Core Strength
The DLLT began with the athlete in a supine position.
A sphygmomanometer was placed beneath the umbilicus. Once
the sphygmomanometer was placed in a correct position, the
subject flexed his hips into 90º with full knee extension
and arms laid along the side of the body with hands palm
down on the field (Appendix C6-Figure 7). However, the
knees were flexed slightly to reduce tension on the
hamstrings, which allowed subjects to flex their hips to
90º. The goniometer was placed at the hip joint. The
stationary arm was placed parallel to the mid axillary line
of the torso (parallel to the floor) and the moveable arm
was parallel to the longitudinal axis of the femur.6 The
subject was instructed to relax the abdominal muscles to 20
mmHg and told to ‘flatten out the back,’ in a drawing-in

17

motion, to stabilize the lumbar spine and increase the
pressure of the sphygmomanometer to 40 mmHg.6 Then the legs
were slowly lowered, maintaining the posterior pelvic tilt
until the pressure of the sphygmomanometer drops below
20mmHg (Appendix C6-Figure 8). The subject’s legs were held
by the researcher once the pressure of the sphygmomanometer
got to below 20mmHg or when this pelvic position could no
longer be maintained. Then the goniometer measurement of
hip joint was taken while being held the legs so that the
athlete did not have to keep contraction of the abdominal
muscles and hold the leg position during the goniometer
measurement. The subject performed the test three times
with one minute rest in between each trial. Average score
from three trials were used for data analysis. If the
subject performed the technique incorrectly no score was
recorded.2 The subject performed the test on another day in
order to practice pelvic tilt and perform the DLLT
correctly. The subject had a rest for two minutes before
moving to the 60s MSUT.

60s Maximal Sit-up Test for Core Power
For the 60s MSUT, the subject lay supine with knees
flexed to 90°and hips flexed about 45°. Fingers were

18

interlocked behind the neck and the backs of the hands
touched the floor (Appendix C7-Figure 9). The feet were
together and another subject stepped on the subject’s feet
to stabilize the position. On the command “go”, the subject
began flexing the trunk to perform the sit up until the
elbows touched to the thighs (Appendix C7-Figure 10) and
then lowered the trunk back until the scapulae came into
contact with floor without touching their head or hands to
the floor for 60 seconds timed by a stopwatch.

At 60

seconds, the researcher recorded the number of successful
repetitions. Subjects performed one sit-up trial per
testing session.1

Warm-up 2: Dynamic Stretch
Prior to the kicking test, subjects performed a series
of dynamic warm-up exercises selected from their soccer
practice and those used in previous research.3 The warm-up
consisted of two laps of jogging, 10 yards of hip external
rotation, forward lunges, backward lunges, lateral squat,
high knees, butt kickers, side shuffle, Carioca, A-skip,
power skip, and straight leg kick followed by the leg swing
to front/back and side to side in place. The subjects
started with two laps of jogging from the start point, and

19

then were instructed dynamic warm up at the station where
the corns were set up for the dynamic warm-up.3 After
performing the leg swing by the fence, the subjects had
kicking/passing warm-up with the partner for five
minutes.11,12 Then the subjects were taken to the area where
the kicking test took place.

Soccer Kicking Test
Soccer performance was evaluated with a dynamic
soccer-style kick for maximal speed. Each subject was
allowed to choose the distance of the run-up to a
stationary ball as well as the type of kick (instep, toe
kick, or shoelace). The subjects approached to the ball
from the starting point, produced a counter movement swing
with the kicking leg, and kicked the ball as hard as
possible towards the radar gun. The researcher recorded the
maximal speed using the radar gun. The subjects had two
practice trials, and three test kicks An average of the
three test kicks was used for data analysis. The subject
had 90 second rest in between each trial.

20

Hypothesis

The following hypothesis was investigated in this
study: There will be a positive correlation among core
power, core strength, core stability, and kicking velocity.

Data Analysis

An alpha level of < 0.05 was used for all statistical
tests. SPSS version 18.0 for Windows was used for all
statistical analyses. The research hypothesis was analyzed
using a Pearson Product Moment correlation to determine any
relationship among core power, core strength, core
stability and soccer kicking velocity.

21

RESULTS

The purpose of the study was to examine the
relationship among core power, core strength, core
stability, and athletic performance in college soccer
athletes. Subjects were tested by using the RS, the 60s
MSUT, the DLLT, and the soccer kicking test (SK). The RS
was used to measure core stability, the DLLT was used to
measure core strength, the 60s MSUT was used to measure
core power, and the SK was used to measure maximal kicking
speed.

Demographic Information

A total of 19 male subjects volunteered to complete
this study. All subjects were physically active individuals
participating in NCAA Division II soccer at California
University of Pennsylvania. One subject’s data was excluded
from data analysis because he was unable to perform 60s
MSUT due to pre-existing conditions, although actively
participating in practice and games without problems. Table

22

1 presents demographic data for the 18 subjects that
completed the study. Years of soccer experience was
determined by active participation from age group to
collegiate soccer.

Table 1. Demographic Information
N
Minimum
Age (yrs)
18
Soccer experience
18
(yrs)
SD = Standard Deviation

Maximum

Mean

SD

23
20

20.39
14.94

1.614
2.920

18
8

Hypothesis Testing

Hypothesis testing was performed by using data from
the 18 subjects who completed all tests at an alpha level
of ≤ 0.05. Descriptive statistics for the RS, the DLLT, the
60s MSUT and the SK are shown in Table 2. The range of
scores for the RS was from zero to three; three being the
best possible score.4 The range of the DLLT was zero to 90;
the degree from starting point (hip flexed to 90º)to ending
point was used for data analysis. The 60s MSUT test was
scored as maximal number of correct sit-ups within the 60second time period.1,10 Higher numbers of repetitions

23

indicate better core power. For the SK, higher speeds
indicated better kicking performance in this case.

Table 2. Descriptive statistics for RS,DLLT,60s MSUT and SK
RS
60s MSUT
DLLT (Degrees)
SK (mph)

N
18
18
18
18

Minimum Maximum
2
3
31
60
26
63
58
75

Mean
2.39
47.28
37.39
67.69

SD
0.502
8.079
8.991
4.540

Hypothesis: There will be a positive correlation among
the RS, the DLLT, the 60s MSUT and the SK, for core
stability, core strength, core power and a maximum kicking
velocity respectively. A Pearson Product Moment Correlation
coefficient was calculated to examine the linear
relationship among all four variables using a one-tailed
test.
Conclusion: There were no significant correlations
among the RS, the DLLT, the 60s MSUT and the SK, for core
stability, core strength, core power and maximum kicking
velocity (Table 3).

24

Table 3. Correlations among RS, DLLT, 60sMSUT and SK
RS
RS
DLLT
MSUT
SK

Pearson Correlation
Sig. (1-tailed)
Pearson Correlation
Sig. (1-tailed)
Pearson Correlation
Sig. (1-tailed)
Pearson Correlation
Sig. (1-tailed)

-.241
.168
.001
.499
-.091
.360

DLLT

MSUT

SK

-.241
.168
1

.001
.499
.328
.092
1

-.091
.360
.348
.078
.020
.469
1

.328
.092
.348
.078

.020
.469

Additional Findings

An additional Pearson Product Moment correlation was
performed to examine the relationship among the RS, the
DLLT, the 60s MSUT, and the Trunk Stability Push-up
test(TSPU) completed as one of seven tests measured for the
Functional Movement Screen (FMS)with a peer researcher, and
is used to grade core stability. Unlike the RS, which
requires multi-plane trunk stability during a combined
upper and lower extremity motion, the TSPU assesses trunk
stability during a closed-chain upper body movement.4 The
subject was asked to perform a pushup with hands aligned
under the top of the forehead for men. A possible score of
three was given if the subject performed the push-up with
the hands aligned with the top of the forehead correctly

25

without any compensation such as excessive movement in the
lumbar spine or not lifting the body as a unit when
performing this push-up. A score of two is given if the
person is able to complete the push up with the hands
aligned with the chin. If the requirements for a score of
two are not met, then a score of a 1 is given. Descriptive
statistics for the TSPU test are shown in Table 4.
A significant moderate low correlation between the
TSPU and the SK was present (r = .435, P = .036) where the
average score of the TSPU was 2.61 with a range of 2-3
(Table 5). Also, no correlations were reported for years of
experience in the athletes (8-20 years) and any of the
performance variables.
Table 4. Descriptive statistics for TSPU
TSPU

N
18

Minimum
2

Maximum
3

Mean
2.61

SD
.502

Table 5. Correlations among TSPU, RS, DLLT, 60sMSUT, and SK
TSPU
TSPU

1

RS
.169
.252
1

DLLT
.073
.387
-.241
.168
1

MSUT

SK

-.059 .435*
.408
.036
RS
Pearson Correlation
.169
.001 -.091
Sig. (1-tailed)
.252
.499
.360
DLLT
Pearson Correlation
.073
-.241
.328
.348
Sig. (1-tailed)
.387
.168
.092
.078
MSUT
Pearson Correlation -.059
.001
.328
1
.020
Sig. (1-tailed)
.408
.499
.092
.469
SK
Pearson Correlation .435* -.091
.348
.020
1
Sig. (1-tailed)
.036
.360
.078
.469
*. Correlation is significant at the 0.05 level (1-tailed)

26

DISCUSSION

Discussion of Results

The main finding was that no significant correlations
among the RS, the DLLT, the 60s MSUT and the SK, for core
stability, core strength, core power and maximum kicking
velocity were observed in NCAA Division II soccer athletes.
While these findings are consistent with findings of
previous studies,

14,15

the recent research by Dendas1 and

Wagner3 has reported a relationship between core stability
and athletic performance in American football athletes1 and
female soccer athletes3).
Nesser et al14,15 investigated the relationship between
core stability and various strength and power variables in
Division I football athletes14 and NCAA Division I female
soccer athletes.15 The core stability was assessed using
McGill Protocol that consists of back extension, trunk
flexion, and left and right bridges in these studies.14,15
Performance variables in the study14 included three strength
variables; one-repetition maximum (1RM) bench press, 1RM
squat, and 1RM power clean, and four performance variables;

27

countermovement vertical jump, 20 and 40 yard sprints, and
a 10 yard shuttle run. Data revealed a number of
significant, but weak to moderate correlations between core
strength/stability and strength and performance.14 The
researchers14 concluded that increases in core strength does
not contribute significantly to strength and power, and
that training programs with emphasis on strength and power
should not focus on core stability and strength.14 Nesser et
al15 also investigated the relationships between core
stability and various strength and power variables in NCAA
Division I female soccer players. The researchers assessed
core stability using the McGill protocol, two strength
variables (1RM bench press and 1RM squat), and three
performance variables (Countermovement vertical jump, 40
yard sprint, and a 10 yard shuttle run) in this study.
According to their findings, no significant correlations
among core strength, strength, and power were confirmed.
Thus, the researchers15 concluded that core strengthening
programs should not be the focus of strength and
conditioning because increases in core strength will not
contribute significantly to strength and power. Dendas1 and
Wagner3 successfully observed the relationship between the
function of the core and athletic performance in a sports

28

specific manner. Dendas7 investigated the relationship
between athletic performance and core stability in Division
II football players where core power using Medicine Ball
Explosive Sit-up Throw Test (MBESTT) and a 60 second
maximum sit-up test with a built-in 30 second test, and
core endurance using McGill protocol were used. Performance
variables to investigate included 3RM for the power clean,
back squat, and bench press, as well as vertical jump
height, and 40m sprint time with a 20m split time.7 The
findings suggested that the 60s maximum sit-up test was
significantly correlated with the relative power clean
(1.09 ± 0.17; r = .836), relative squat (1.64 ± 0.28; r
= .608), relative bench press (1.24 ± 0.19; r = .590),
vertical jump height (29.11 ± 3.70 in; r = .721), 40-m
sprint time (5.26 ± 0.37 s; r = -.680), and 20-m sprint
time (3.23 ± 0.27 s; r = -.803). Thus, Dendas’ findings
suggested that core power has a greater contribution to
athletic performance in football players than isometric
core stability.
On the other hand, Wagner’s findings suggested that
isometric core stability (ICS) has a greater contribution
to soccer performance (standing kick and throw-in for
maximum speed) than concentric functional core strength

29

(CFCS).3 According to the researcher,3 ICS test was used to
evaluate the ability of the core to provide a stable base
of support with use of a isokinetic dynamometer during
movements of trunk flexion (TF) and bi-lateral rotation,
while CFCS test was used to evaluate the ability of the
core to produce and transfer forces to the limbs by
performing the front abdominal power test (FAPT) and side
abdominal power test (SAPT).15 This researcher found
significant and meaningful correlations between isometric
TF and throw-in (r = 0.526) and isometric left rotation
(LR) and right footed kick (r = 0.622). Also, there were
significant correlations between isometric right rotation
(RR) and right footed kick (r = 0.753) and isometric TF and
left footed (r = 0.615).15
Although the main finding in the current study did not
support their findings and the question,1,3 which type of
core function has a greater contribution to athletic
performance,

additional analysis supported Wagner’s

findings between trunk stability and athletic performance
measured by kicking speed. Specifically, core stability
measured by the TSPU was positively moderately correlated
to kicking velocity as measured by the SK. Wagner3
identified the relationship between core fitness and tests

30

of soccer sport performance in female soccer players, and
defined core fitness as “the combination of isometric core
stability and concentric core strength to perform a task of
sport performance.”3(p8) His finding suggested that isometric
core stability has a greater contribution to soccer
performance (standing kick and throw-in for maximum speed)
than concentric functional core strength in female soccer
athletes.3 The current additional finding supported that
isometric core stability has a greater contribution to
soccer performance when maximal effort is required.
Although the previous researchers1,3 assumed that
selecting core tests that are specific to performance
capabilities is a key to investigate the relationship
between two variables successfully, the finding between the
TSPU and the SK supported the idea that isometric core
strength elicited a greater muscular activation due to a
larger load placed on the core, which could have resulted
in a greater correlation with tests of soccer athletic
performance.3
Considering that the isometric core stability test
used by Wagner3 has same characteristics of core function
with the TSPU in the current study, the tests that measure
the isometric core stability without dynamic limb movements

31

may be valid and reliable to assess core stability. Unlike
the RS, which require multi-plane trunk stability during a
combined upper and lower extremity motion, the TSPU
assesses trunk stability during a closed-chain symmetrical
upper body movement.4
As Sharrock et al2 discussed in their literature, it
would be appropriate to measure core function during
dynamic movements in sports which require complex,
explosive, and multilane movements. However, there is no
gold standard used to measure core function, and no
reliable and valid measurements that have been established
in the previous literature.2 The tests of the core function
in the current study (RS, DLLT, and 60s MSUT) were selected
due to existing reliability and/or validity, these tests
did not have similar movement patterns of the specific
athletic performance. Not only have these core tests have
been widely used, but the reliability of the tests has been
reported.

The FMS has been reported to have an intraclass

correlation coefficient (ICC) value of 0.98.5 Reliability
for the timed sit-up tests have previously been
established.1,10 Dendas reported that test-retest reliability
coefficients for 60s timed sit-up test was statistically
significant (r = 0.862).1 Augustsson et al10 also reported

32

an ICC of 0.93 with a 95% confidence interval of 0.77.10
Sharrock et al reported that DLLT has been found to be
reliable; the ICC for repeated measures of the DLLT was
0.98.7 From author’s knowledge, the study7 is only one
literature that has reported ICC of the DLLT. Sharrock et
al suggested that “the DLL test is an appropriate way to
measure core stability as it pertains to athletic
function”16 based on evidence in previous literature, while
Krause et al7 reported the DLLT has excellent intra-tester
reliability as an assessment of core strength. The
researcher7 reported an ICC of 0.98 that for repeated
measures of the DLLT. Although the validity of the DLLT has
not been shown in the previous literature,2,6-8 this test has
been found to be reliable,7 and the DLLT has been used in
several studies.2,6-8 Thus, the DLLT is a typical method to
measure core strength.17,18 Prentice described DLLT as the
Straight Leg Lowering Test (SLLT), and suggested that core
strength can be assessed with using SLLT as well.17
However, we experienced difficulty assessing core
strength with the use of a BP cuff during the DLLT when
subjects had increased lumber lordosis. According to
procedures, the BP cuff is used to determine subject’s
ability of maintaining posterior pelvic tilt. A peer

33

researcher was needed to observe subject’s pelvic movement
to assess their core strength, while the researcher read
the change of BP cuff in that case. Although all athletes
were able to perform posterior pelvic tilt, some of them
were not able to increase BP cuff pressure as described in
the procedure (increase BP cuff to 40mmHg before lowering
the legs.) The score of the DLLT was then determined by the
point where the subjects keep posterior pelvic tilt.
While the selected core tests measured some aspect of
core function in the current study, it appears that the
test criteria were not sufficient to differentiate each
core function. To seek the relationship between core
function and athletic performance, future research is
needed to establish valid and reliable core measurements
first. It seems to be difficult to define core variables
based on each core function since all core muscles work
synergistically to provide stability. However, Wagner’s3 and
our additional finding suggested that tests used to measure
isometric core stability may be valid and reliable to
assess core stability. Further research is needed with
larger number of subjects, elite/professional athletes in
variety of sports, a greater variety of core tests, and
more demographically diverse subjects.

34

Conclusions

While no significant correlations among the selected
tests for core stability, core strength, core power and
maximum kicking velocity in healthy Division II college
male soccer athletes were reported, an additional test for
core stability yielded different results. The significant
moderate correlation between the push up test for core
stability and kicking velocity indicates that isometric
core stability/strength elicited a greater muscular
activation due to a larger load placed on the core during a
maximal kick.

These findings support the current

literature in that isometric core stability has a greater
contribution to soccer performance measured by standing
kick and dynamic style kick for maximum kicking velocity.3

35

Recommendations

Our findings suggested that it may be necessary to
assess core stability with a test involving no limb
movements (specifically of the upper and/or lower
extremity) in order to identify contribution of the core to
athletic performance. Only moderate relationships between
core stability sports performance have been reported here
and in previous research, further research is needed not
only to establish validity and reliability of core tests,
but also to quantify the relationship between core function
and athletic performance. Our findings support the theory
that the core musculature is the kinetic link between the
lower and upper body and should directly influence any
distal kinetic chain movement. Implications that the core
has a significant role in providing a base of support for
optimal lower extremity function, and the ability to
produce and transfer force to the distal segments during a
functional soccer task, specifically maximal kicking
velocity could be used in future testing for injury
prevention or performance enhancement.

36

Considering the complexity of the core musculature and
its synergic function, however, it may not be important to
quantify the relationship for the athletic trainers and
allied health care professionals. Whether the relationship
between core function and athletic performance is
determined or not, it would be more beneficial to have the
ability to assess athletes’ various aspects of core
function and performance, to train athletes with
appropriate exercise selections/applications, and to
prevent/rehabilitate athletic injury with the concept of
kinetic chain, particularly when assessing for return to
play. Application of a valid core stability test, such as
the trunk stability push-up test (TSPU from the FMS) and
other core stability tests involving no limb movements, may
help to assess soccer kicking performance after lower
extremity injuries.

37

REFERENCES

1.

Dendas A. The relationship between core stability and
athletic performance. [master’s thesis]. Arcata, CA:
Humboldt State University; 2010.

2.

Sharrock C, Cropper J, Mostad J, Johnson M, Malone T.
A pilot study of core stability and athletic
performance: is there a relationship? Int J Sports
Phys Ther. 2011;6(2):63-74.

3.

Wagner J. Convergent validity between field tests of
isometric core strength, functional core strength, and
sport performance variables in female soccer players.
[master’s thesis]. Boise, ID: Boise State University;
2010.

4.

Cook G, Burton L, Hoogenboom B. Pre-participation
screening: The use of fundamental movements as an
assessment of function - Part 2. North Am J Sports
Phys Ther. 2006;1(3):132-139.

5.

Anstee L, Docherty C, Gansneder B, Shultz S. Intertester and intra-tester reliability of the Functional
Movement Screen Paper presented at: National Athletic
Training Association National Convention, 2003; St.
Louis, MO.

6.

Zingaro R. Correlation between core strength and serve
velocity in collegiate tennis players. [master’s
thesis]. California, PA : California University of
Pennsylvania; 2008.

7.

Krause D, Youdas J, Hollman J, Smith J. Abdominal
muscle performance as measured by the double leg
lowering test. Arch Phys Med Rehabil. 2005;86:13451348.

8.

Butcher S, Craven B, Chilibeck P, Spink K, Grona S,
Sprigings E. The effect of trunk stability training on
vertical takeoff velocity. J Orthop Sports Phys Ther.
2007;37(5):223-231.

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9.

Ladeira C, Hess L, Galin B, Fradera S, Harkness M.
Validation of an abdominal muscle strength test with
dynamometry. J Strength Cond Res.2005;19(4):925-930.

10.

Augustsson S, Bersas E, Magnusson-Thomas E, Sahlberg M,
Augustsson J, Svantesson U. Gender differences and
reliability of selected physical performance tests in
young women and men. Adv. Physiother. 2009;11:64-70.

11.

Sedano S, Benito A, Izquierdo J, Redondo J, Cuadrado
G. Validation of a measuring system for kicking speed
in soccer. Apunts Educ Fís Deportes. 2009;96:42-46.

12.

Sedano S, Vaeyens R, Philippaerts R, Redondo J, De
Benito A, Cuadrado G. Effect of lower-limb plyometric
training on body composition, explosive strength, and
kicking speed in female soccer players. J Strength
Cond Res. 2009;23(6):1714-1722.

13.

Jugs [package insert]. Tualatin, OR: JUGS Sports Inc.

14.

Nesser T, Huxel K, Tincher J, and OkadoT. The
relationship between core stability and performance in
Division I football players. J Strength Cond Res.
2008;22(6):1750-1754.

15.

Nesser T, Lee W. (2009). The relationship between core
strength and performance in division I female soccer
players. J Exerc Physiol Online. 2009;12(2):21-28.

16.

Sharrock C, Cropper J, Mostad J, Johnson M, Malone T.
A pilot study of core stability and athletic
performance: is there a relationship? Int J Sports
Phys Ther. 2011;6(2):66.

17.

Prentice W. Rehabilitation Techniques for Sports
Medicine and Athletic Training. 4th ed. Boston, MA:
McGraw Hill;2004:200-223.

18.

Muscolino, JE, Cipriani S. 2004. Pilates and the
‘‘powerhouse’’. J Body Mov Ther. 2004;8(1):15–24.

39

APPENDICES

40

APPENDIX A
Review of literature

41

REVIEW OF LITERATURE

The purpose of this review of literature is to
overview previous studies examining core power and its
effect on athletic performance. This literature review
includes the following four sections: (1) Review of the
Core, (2) Assessment of Core function, (3) Role of the Core
in Athletic Performance, and (4) Summary of the research
performed to date.

Review of the Core

The core has been identified as a key component for
functional athletic performance in the field of sports
science.1-7 The core is referred as the region of the body
that provides an adequate support for upper and lower
extremity movements, during athletic performance.7 An
efficient core provides optimum force production, as well
as transfers and controls force and movement in the
integrated functional athletic performance.3,4,7,8 The basic
foundation of the core comes from more than 20 muscles that
attach to the lumbo-pelvic-hip complex.7,9(p290) Although some

42

researchers10,11 previously advocated the importance of a few
core stabilizers, especially the transversus abdominis and
multifidi, all core muscles work synergistically to provide
stability and mobility of the spine in order for optimum
athletic performance.7,9-11 Several researchers have
attempted to explain the musculature of lumbo-pelvic-hip
complex and its role in rehabilitation and athletic
performance in their previous literature.7,9(p295),12 However,
the complexity and integrated function of the lumbo-pelvichip complex causes confusion regarding the definition of
the core; differences among core stability, core strength,
and core power; valid assessment of the core stability; and
its application to functional athletic performance.1-7
Therefore, it is very important to have an understanding of
core anatomy and a clear definition of core strength,
stability and power in order to assess the functional
athletic performance.

Anatomy of the Core
The core is referred to as the “powerhouse,” its where
breathing and all the physical movements originate in
Pilates exercise. The concept of core strength and
stabilization was first addresses by Joseph Pilates who

43

created the Pilates exercise philosophy.13 Akuthota et al4
have also described the function of the core as being a
“powerhouse,” the center of the functional kinetic chain,
that provides optimum force and power and initiates limb
movement.4 The researcher4 also describe the core as a box
that consists of core stabilizers; abdominal muscles in the
front, paraspinals and gluteal muscles in the back, the
diaphragm on the top, and the pelvic floor and the hip
girdle muscles as the bottom. The core musculature works
together synergically in order to support the “powerhouse”
and provide optimum performance.
Bergmark originally introduced the concept of “global”
and “local” core musculature in his literature in 1989.12
According to Bergmark,12 the “local” system consists of all
the muscles that originate and insert at the vertebrae,
with the exception of the psoas muscles. Local muscles are
referred to as deep stabilizers and are responsible for the
lumbar and thoracic stabilization. Global muscles are more
superficial, are responsible for movement of the trunk, and
transfers forces from the torso and the pelvis out to the
extremities.4,7,12 Since Bergmark’s classification of local
and global system, several researchers have introduced the
concept and attempted to explain the function of the lumbo-

44

pelvic-hip complex with some modifications in their
studies.2,4,7 Dendas7 categorized the transverse abdominis
and multifidus as primary local core stabilizers, and
internal oblique, medial fibers of the external oblique,
quadratus lumborum, diaphragm, pelvic floor muscles,
iliocostalis and longissimus as secondary local core
stabilizer. The rectus abdominis, lateral fibers of the
external obliques, psoas major, and erector spinae were
defined as the global core system based on Norris’ study.14
Dendas also included all muscles that attach at the hip or
cross the lumbo-pelvic region, such as the gluteals,
hamstrings and quadriceps into the global system since the
core consists of the musculature of the lumbar, pelvic, and
hip regions contribute to spinal stability.9 Some
researchers4,7,15 described

the hip musculature as playing a

significant role in transferring forces from the lower
extremities to the pelvis and spine, and then out to the
upper extremity. The lumbo-pelvic-hip complex also
contributes to the piriformis and psoas major-iliacus
complex that work as synergists and stabilizers of the
core.4,6 These global core muscles are responsible for
spinal orientation and control of external forces on the
spine.1 The large moment arms and long levers of these

45

muscles allow these global muscles to produce powerful
movements and torque.5,7

Core Stability
Although the term of the “core stability” has been
very popular in the field of sports science, there is no
clear definition of the term “core stability.”7 It may be
because that any musculoskeletal structures of the lumbopelvic-hip complex have been used to describe core
stability, which include strength of hip and core
musculature; core muscle endurance; maintenance of a
particular pelvic inclination or of vertebral alignment;
and ligamentous laxity of the vertebral column.6 Because
core stability, core strengthening, and core power are
terms that appear to be used interchangeably throughout
literature,1,7,16 it is important to have a clear definition
of core stability and its components including core
strength, core endurance and core power.
Core stability can be defined as the ability of lumbopelvic-hip complex to stabilize the spine, which is
produced by the coordinated efforts of the core musculature
and its functions.5,7,12,17 Although the core stability is
mainly maintained by the “local” core musculature, the

46

muscles that originate and insert at the vertebrae, with
the exception of the psoas muscles , most core muscles,
both the local and global stabilizers, must work together
synergistically to achieve core stability.2,6 According to
Tse et al, “the core musculature includes muscles of the
trunk and pelvis that are responsible for maintaining the
stability of the spine and pelvis and are critical for the
transfer of energy from the larger torso to smaller
extremities during many sports activities.”18 Kibler et al
defines core stability as “the ability to control the
position and motion of the trunk over the pelvis to allow
optimum production, transfer, and control of force and
motion to the terminal segment in integrated athletic
activities.”19 According to Willson et al,6 core stability
functions to effectively recruit the core musculatures and
to provide a stable foundation for movements of the upper
and lower extremities during athletic performance. Borghuis
et al2 suggested the role of sensory-motor control of core
musculature is responsible for a precise balance between
the amount of stability and mobility, compared with the
role of strength or endurance of the core musculature.
Therefore, appropriate muscle recruitment and timing has a

47

significant role in creating core stability as a base for
all functions of core and extremities.
Finally, Dendas defined core stability as a foundation
of all core functions, which is comprised of components
including core strength, core power, balance, and
coordination.7 In short, core stability primarily
contributes to optimal neuromuscular efficiency in entire
kinetic chain, transfer of force, control of upper and
lower extremity in dynamic movement, and production of
power.

Core Strength
When discussing the core, it is important to
differentiate between core stability and core strength.
These two terms are often used interchangeably not only in
the literature but also in the practical field. Core
stability and core strength differ based on their functions
and involved musculature that are used.1 Cholewicki et al20
defined that core strength is more active control of spine
stability achieved through the regulation of force in the
surrounding muscles. According to Dendas,21 core strength
was best described as “a necessity for core stability,
meaning that there cannot be one without the other; the

48

core musculature has to possess both.” Since the core works
synergically to provide stability and mobility to the spine,
core stability and core strength may be confused for one
another in the literature and by practitioners.15

Core Endurance
Core endurance, a component of core stability, can be
defined as the ability of the lumbo-pelvic-hip musculature
to hold a core contraction for a prolonged time and/or
perform repeated contractions over a period of time.7,22
Although core strength aids in producing force by
maintaining intra-abdominal pressure,7 core endurance
contributes more to length of time that a muscle or muscle
group can hold a neutral stable position. Since core
endurance also plays an important role in core stability
and strength, it often causes the confusion regarding the
definition of core endurance. Lehman17 has suggested that
the core endurance influence to spinal stability is more
than muscular strength due to the ability of local core
musculature to stabilize the lumbar spine. Several
researchers have also suggested that good core endurance
reduces back pain.10-11

49

Core Power
Power is referred as “the product of muscular force
and the velocity of muscle shortening” in human
biomechanical science.22 Dendas defined power as “the amount
of mechanical work done over a certain amount of time” and
core power as “explosive concentric contractions of the
musculature over a certain amount of time against an object,
such as throwing a weighted medicine ball.”23 The core power
is commonly measured with use of medicine ball. The
assessment includes the medicine ball toss using the
overhead and reverse overhead throws. Dendas7 suggested that
core power is also a component of core stability, which was
measured by the medicine ball explosive sit-up throw test
and maximum sit-ups in 30 and 60 seconds in the study.7 the
researcher found a significant relationship between the
core power measured with 60s and 30s maximum sit-up tests
and athletic performance tested by the relative power
clean, relative squat, relative bench press, vertical jump
height, 40m sprint time, and 20m sprint time.7

50

Assessment of Core Function

Due to the complexity of the core musculature and its
synergic function, the core cannot be assessed with one
test or one aspect of core functions.7 Although several
researchers have attempted to measure core stability and
these components as they examined the relationships between
core stability and performance,7,15-16,24-25 or effects of core
training on performance,

26-30

there is currently no gold

standard recommended to assess core stability and it’s
components, which include core strength, core endurance,
and core power.1,7
Common methods of core assessment have included
isokinetic dynamometer for measures of strength and work,
isometric exercises for measures of strength and endurance,
and dynamic exercises for measures of strength and power.7,15
Isokinetic dynamometry, the Sahrmann test of core stability,
and McGill protocol have been mainly used to assess
function of the core in clinical or laboratory settings.
Other measures using dynamic exercises such as timed situps,7 front abdominal power,31 side abdominal power,31 and
double leg lowering,32 were preferred in practical settings,
especially in the field of strength and conditioning.

51

Reliability of core assessments has been established in
previous studies using non-athletic populations31,33-35 and
athletes.7,16,24,36-37 According to Baumgartner et al,38 the
reliability of most core stability tests was acceptable
based on magnitude of the test-retest correlation
coefficients. In order to assess the relationship between
core and athletic performance, however, further research on
validity and reliability of core assessments are needed
because previous core assessments have been limited in
regards to the sports and performance specificity,
including the type of muscular contractions and movement
speeds.7

Isokinetic Dynamometer for Strength and Work
The use of an isokinetic dynamometer is one of the
standard methods of assessing core strength and work.15 In
isokinetics, work is defined as torque multiplied by
angular displacement or the area under the torque
curve.10(p152-153) In other words, it is define as the amount
of rotational force being produced. It allows researchers
to measure three different strength variables (peak torque,
total work, and average power) within one testing
session.39-40 Wagner15 recently used isokinetic dynamometer

52

during movements of trunk flexion and bi-lateral rotation
to assess isometric core strength. Although isokinetic
machines have exhibited high reliability coefficients in
the previous literature,35,38 it is still unknown whether the
use of an isokinetic dynamometer is valid in assessing core
strength and power to accurately measure force of the
intended musculature.15

Sahrmann’s Test for Core Stability
According to Faries and Greenwood, the Sahrmann core
stability test is a measurement for the "ability of the
core musculature to stabilize the spine with or without
motion of the lumbo-pelvic-hip complex."41 The test consists
of five levels with each level increasing in difficulty,
progressing from a static position with activating
transverse abdominals to positions that incorporate with
lower extremity movement. The individual has to maintain
the lumber stabilization with a change of no more than 10
mmHg in pressure on a blood pressure cuff that is placed
directly under individual’s lumbar spine. Faries and
Greenwood5 illustrated the Sahrmann assessment protocol as
the following.

53

The level 1 begins in the supine with hip-flexed at
45º degrees and knee-flexed at 90º. The blood pressure cuff
then is inflated to 40 mmHg, while the individual flatten
out the back, in a drawing-in motion (hollowing), to
stabilize the lumbar spine. This abdominal hollowing is the
key component of the Sahrmann core stability test. If
performed correctly, the pressure blood pressure cuff does
not change or slightly decrease from the initial 40 mmHg.5
At level one, the individual slowly raises one leg to 100°
of hip flexion with comfortable knee flexion from supine,
hook-lying position with abdominal hollowing. The opposite
leg is brought up to same position. At level 2, the
individual slowly lowers one leg until the heel contacts
the ground from the hip flexed position, and then slides
out the leg to full knee extension. The leg returns to the
starting flexed position and then alternates the leg. At
level 3, the individual performs the same motion as level 2
except the heel contact on ground. The subject is not
allowed to contact both heels on ground as lowering the
legs at level 3. At level 4, the individual slowly lowers
both legs until both heels contact the ground from hip
flexed position, and then slides out both legs to full knee
extension. At level 5, the individual performs the same

54

motion as level 4 except heel contact. The subject is not
allowed to contact both heels on ground as lowering the
legs level 5. Although the Sahrmann core stability test has
widely used in the clinical setting with established
reliability,42 its validity is currently unknown in
available literature.7

McGill Test for Strength and Endurance
When measuring core stability and/or core strength in
athletes, some researchers16,24,36-37 have assessed core with
use of the McGill protocol.34 The McGill protocol was
originally established to assess core stability in patients
with low-back pain by determining muscle endurance of the
core stabilizer muscles.34 This protocol consists of four
isometric core endurance tests: trunk flexor test, trunk
extensor test, and left and right lateral musculature test.
The longer the person holds the position without movement
correlates to strong core endurance. The trunk flexor test
starts in a sit-up position at 60º from the floor with
knees and hips flexed to 90º. The test ends when any part
of the individual’s back touches the jig that is placed 10
cm away from the back.24 The trunk extensor test is
evaluated with the upper body off the supporting bench with

55

the lower legs secured. The test ends when the upper body
drops below the horizontal position from the supporting
bench.24 The lateral musculature test is evaluated in the
side plank position. The person maintains the full sidebridge position with straight Legs. The person supports the
torso on one elbow and on the feet while holding the hips
off the floor. The test ends when the person loses the
straight-back posture and/or the hip drops to the ground.
Dendas7 discussed that there has not been reliability
coefficients determined for the McGill protocol using
football athletes, however, this protocol seemed to be
valid as a widely used test to assess core endurance among
non-athletic population. Durall et al38 reported intraclass
correlation coefficient (ICC) with the range from 0.89 to
0.92 for the McGill protocol in college gymnasts. Dendas
reported that

only two out of the four individual tests

were considered to have "acceptable" reliability where
test-retest reliability correlation coefficients of the
trunk flexion (r = 0.828, p = 0.000) and Left flexion
0.742, p = 0.000)

(r =

were present.7 The researcher also found

that left and right lateral musculature tests were related
to one another (r = 0.830, p = 0.000).7

56

Double Leg Lowering Test for Core Strength
The DLLT has been commonly used to assess either core
stability or core strength in previous literature.25,32,43-44
Sharrock et al suggested that “the DLL test is an
appropriate way to measure core stability as it pertains to
athletic function”45 based on evidence in previous
literature, while Krause et al32 reported the DLLT has
excellent intra-tester reliability as an assessment of core
strength. The researcher32 reported an ICC of 0.98 that for
repeated measures of the DLLT. Although the validity of the
DLLT has not been shown in the previous literature,25,32,43-44
this test has been found to be reliable,32 and the DLLT has
been used in several studies.25,32,43-44 Thus, the DLLT is a
typical method to measure core strength.11,13, Prentice
described DLLT as the Straight Leg Lowering Test (SLLT),
and suggested that core strength can be assessed with using
SLLT as well.11
In the current study, the modified DLLT will be used
to measure core strength. The angle of the hip is measured
with a goniometer will be taken the pressure of the blood
pressure cuff drops below 20mmHg.43,46 This is unlike the
double leg-lowering test, which takes a measurement at 40
mmHg. The angle of the hip interprets strength of core. The

57

lower the subject can lower the legs correlates to a
stronger core.32,43-44 The modified DLLT test has shown to be
reliable.44

60s Maximal Sit Up Test for Core Power
The sit-up test is one of the most common tests used
in assessing the core musculature in the practical setting.7
It has been used into many training programs as a
traditional core exercise because this exercise effectively
activates the abdominal and hip flexor muscles at the same
time.7 According to Dendas,7 sit-ups activate mainly the
"global" core muscles such as rectus abdominis and internal
and external obliques, while minimally activate “local”
muscles such as transverse abdominis, to ensure sufficient
spinal stiffness.34
Reliability for the timed sit-up tests have previously
been established in both of young adults and athletes.7,35
Augustsson et al35 examined the reliability of the maximum
sit-ups and the 30-second sit-up test in their study. The
researchers used ICC for analyses of the test/retest
reliability calculated at 95% CI.35 The researchers reported
an ICC of 0.92 with a 95% CI of 0.77-0.98 for the maximal
number of sit-ups and an ICC of 0.93 with a 95% CI of 0.77-

58

0.98 for the 30-second maximum sit-up test, suggesting that
the tests are highly reliable for both muscular endurance
and power testing in young active male and female.35
Recently, Dendas used a test similar to the 60-second
maximum sit-up, with a built in 30-second test, in order to
assess core power in collegiate Division II football
players.7 This test starts in the supine position with
knees flexed to 90°and hips flexed about 45°. Subjects are
required to elbows touch thighs on up portion and then
lower the trunk back until the scapulae came in contact
with ground, without touching their head or hands. The
athlete moves quickly through the repetitive movement
pattern. The 60-second maximum sit-up test, with a built in
30-second test, was found to have a high reliability
coefficient (r = 0.862, p = 0.000).7

The test is scored as

maximal number of correct sit-ups within the 60-second time
period.7,47

The Role of the Core in Athletic Performance

Over the past several years, the amount of literature
regarding a correlation between core function and athletic
performance has significantly increased. Although several

59

researchers previously showed the effect of core exercise
participation on core stability,

27-30

relatively few studies

have attempted to quantify a correlation between the two
variables.7,15-16,24-25 Regarding previous studies on the
relationship between core and sport performance,
researchers have suggested that there was little to no
correlation between the two variables.16,24,48 According to
Wagner,15 a possible reason for these findings was the
failure to select appropriate testing methods. The
researcher suggested that previous studies did not take
into account the physiologic energy systems and movement
specificity patterns required by the sport in selecting
core assessment.15 Therefore, recent research7,15 has
attempted to adapt specific physiologic characteristics and
movement patterns of the core musculature into both the
core assessment protocols and the sport performance tests.

Core Stability Exercise and Athletic Performance
Sato et al26 investigated the effects of six weeks of
participation in a core strengthening program on running
kinetics, lower-extremity stability, and 5000 meter
performance in runners. Although the researchers provided
evidence of a significant effect on running time in the

60

experimental group after six weeks of training, the core
stability test did not significantly influence ground force
production and lower-leg stability functions. The
researchers concluded that core strength training may be an
effective training method for improving performance in
runners due to the effect of effect on running time.26
Stanton et al27 examined the effect of a short-term Swiss
ball training on core stability and running economy. The
researchers assessed core stability using Sahrmann’s core
test, and observed electromyographic (EMG) activity of
abdominal and back muscles, VO2max, and running economy.
Since there were no significant differences observed for
EMG activity of the abdominal and back muscles, treadmill
VO2max, running economy, or running posture, researchers
concluded that Swiss ball training may positively affect
core stability without concomitant improvements in physical
performance.27 Marshall and Desai28 determined muscle
activity of upper body, lower body, and abdominal muscles
during advanced Swiss ball exercises with use of EMG
analysis. The researchers concluded that performing more
complicated Swiss ball exercises may reduce potential
benefits due to the practical difficulty and risk. However,

61

this study provided evidence that advanced Swiss ball
exercise provides a significant whole body stimulus.28
Abt et al29 also suggested that improved core stability
and core endurance could promote greater alignment of the
lower extremity when riding bicycle for extended duration
due to the ability of the core to resist to fatigue. It was
suggested that core fatigue resulted in altered cycling
mechanics that might increase the risk of injury because
the knee joint is potentially exposed to greater stress.29

Core Stability and Athletic Performance
To the authors' knowledge, there were only five
studies which have investigated the relationship between
athletic performance and components of core stability core
functions, which include core strength, core endurance,
core power, and “core fitness.”7,15-16,24-25
The study by Nesser et al16 was the first study, to the
author’s knowledge, to examine the relationship between
core stability and athletic performance in Division I
football athletes. The core stability was assessed using
McGill Protocol that consists of back extension, trunk
flexion, and left and right bridges. Performance variables
included three strength variables; one-repetition maximum

62

(1RM) bench press, 1RM squat, and 1RM power clean, and four
performance variables; countermovement vertical jump, 20
and 40 yard sprints, and a 10 yard shuttle run. The
collected data revealed that core stability is moderately
related to strength and performance. The researchers16
concluded that increases in core strength do not contribute
significantly to strength and power, and that training
programs with emphasis on strength and power should not
focus on core stability and strength.16
Nesser et al24 also investigated the relationships
between core stability and various strength and power
variables in NCAA Division I female soccer players. The
researchers assessed core stability using the McGill
protocol (back extension, trunk flexion, and left and right
bridges), two strength variables (1RM bench press and 1RM
squat), and three performance variables (Countermovement
vertical jump, 40 yard sprint, and a 10 yard shuttle run).
According to their findings, no significant correlations
among core strength, strength, and power were confirmed.
The researchers concluded that core strengthening program
should not be the focus of strength and conditioning
because increases in core strength will not contribute
significantly to strength and power.24

63

Sharrock25 examined the relationship between a core
stability test and tests of performance using the doubleleg lowering test as a measure of core strength/stability
collegiate athletes in a variety of sports. Performance
tests included the forty yard dash, the T-test, vertical
jump, and a medicine ball throw. Although correlational
data results showed a fair to weak relationship between the
DLLT as a measure of core stability and the medicine ball
throw, no significant correlations between abdominal
strength and the T-test (r = 0.052), forty-yard dash (r =
0.138), and the vertical jump (r = –0.172)were reported.30
Recently, two research groups7,15 investigated the
relationship between core stability and athletic
performance in a sports specific manner. These researchers
assumed that selecting core tests specific to performance
capabilities is a key to investigating the relationship
between two variables successfully. By estimating the tests
of core stability that has similar movement patterns of the
specific athletic performance, researchers were able to
analyze the core muscular contributions in dynamic movement.
Wagner15 and Dendas7 successfully observed the relationship
between the function of the core and athletic performance;
although their conclusions were conflicted within the

64

context of core stability and its effect on athletic
performance.
Dendas7 investigated the relationship between athletic
performance and core stability in Division II football
players where core power using Medicine Ball Explosive Situp Throw Test (MBESTT) and a 60 second maximum sit-up test
with a built-in 30 second test, and core endurance using
McGill protocol were used. Performance variables to
investigate included 3RM for the power clean, back squat,
and bench press, as well as vertical jump height, and 40m
sprint time with a 20m split time.7
The findings showed that there was a significant
relationship between athletic performance and 60 second and
30second maximum sit-up tests, and the McGill trunk flexion
test. The 60s maximum sit-up test was significantly
correlated with the relative power clean (r = 0.836),
relative squat (r = 0.608), relative bench press (r =
0.590), vertical jump height (r = 0.721), 40-m sprint time
(r = -0.680), and 20-m sprint time (r = -0.803). The MBESTT
was only significantly correlated to the absolute bench
press (r = 0.496). Although Dendas7 hypothesized that MBESTT
represented the contribution of the core power, scores on
the MBESTT were not related to scores on any of the other

65

measures of core stability in the study, the researcher
concluded that most of the core stability measures had
acceptable field-based test reliability.
Wagner15 identified the relationship between core
fitness and tests of soccer sport performance in female
soccer players. The researcher defined core fitness as “the
combination of isometric core stability and concentric core
strength to perform a task of sport performance.”49
According to the researcher, isometric core strength was
used to evaluate the ability of the core to provide a
stable base of support with use of a isokinetic dynamometer
during movements of trunk flexion and bi-lateral rotation,
while concentric functional core strength was used to
evaluate the ability of the core to produce and transfer
forces to the limbs by performing the front abdominal power
test (FAPT) and side abdominal power test (SAPT).15 The
researcher compared these two core tests with the soccer
kick and throw-in to see which core function played a
greater role in soccer athletic performance. The
researchers assessed isometric core strength while they
assessed concentric functional core strength The
researchers concluded that the isometric core strength
correlated more strongly with tests of soccer sport

66

performance than concentric functional core strength, as
opposed to other previous studies and their own
hypothesis.15 The researcher explained the results that “the
isometric tests had a much larger load placed on them,
which elicited a greater muscular activation and could
explain why there was a greater correlation with tests of
soccer sport performance.”21(vi) Wagner’s finding suggested
that isometric core stability has a greater contribution to
soccer performance (kicking and throw-in) than concentric
functional core strength. Although both researchers7,15 have
established valid assessments of core and athletic
performance, their findings leaves the question, which type
of core function has a greater contribution to athletic
performance?

Core in Soccer Kicking
Theoretically, the core musculature links the lower
and upper body in the kinetic chain and directly influences
the control and force production of the kicking motion.15 In
approaching a soccer ball for a kick, the core musculature
helps to stabilize the spine and produce maximum force into
the ball by which the core musculature co-contract and
increase intra-abdominal pressure.

67

The soccer kick significantly depends on various
factors including the strength of musculature of lower
extremity, the distance of the kick from the goal, the type
of kick used, the air resistance, the rate of rapid
movement of knee flexion and extension, and any other
biomechanical factors.50 Kellis et al50 examined research
findings on the biomechanics of soccer kick performance and
identified weaknesses of present research. The researchers
also summarized previous studies of muscle activation
during the kick. According to Kellis et al,50 previous
researchers have examined muscle activation patterns of the
iliopsoas, rectus femoris, vastus lateralis, vastus
medialis, biceps femoris, gluteus maximus, semitendinosis,
and tibialis anterior during the kick with use of EMG.
Dorge et al51 examined the EMG activity of hip flexion,
knee extension and ankle plantarflexion moments (N·m)
during soccer kicking. The researchers observed a high
activation of iliopsoas during the backswing phase in the
soccer kicking. The findings suggested a high activation of
the iliopsoas during the beginning of the kicking which was
followed by a high activation of the rectus femoris during
backswing. In turn, high activation of vastus lateralis was
observed during forward swing phase.50-51 The researchers

68

also suggested that the EMG activity levels correspond to
the proximal-to-distal pattern of segmental angular
velocities for kick performance. Although there are a few
studies that examined muscle activation patterns during the
soccer kick,50 the muscles examined were mostly lower
extremity and hip flexors; no literature was found
regarding the activation of abdominal muscles and other
core musculature. According to the researcher’s knowledge,
only one previous study exists that examined the
relationship between kicking speed and core measures.15

Summary

In summary, various reasons exist as to why previous
research has not been able to firmly establish the role
that the core plays in sport performance. It can be mainly
because the complexity and integrated function of the
lumbo-pelvic-hip complex causes confusion regarding the
definition of the core, differences among core stability,
core strength, and core power, valid assessment of the core
stability, and/or its application to functional athletic
performance.1-7 Although several researchers previously
showed the effect of core exercise participation on core

69

stability,26-30 relatively few studies have attempted to
quantify a correlation between the core function and
athletic performance.7,15-16,24-25 As mentioned in Wagner’s
study,15 a possible reason for these findings was the
failure to select appropriate testing methods. Thus, the
literature suggests that further research should focus on
the specific physiologic characteristics and movement
patterns of the core musculature when choosing the core
assessment protocols and the sport performance tests.
Apparently, core function can be associated with upper or
lower extremity movement as long as those movements are
similar to the specific athletic performance.7,15

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APPENDIX B
The Problem

71

STATEMENT OF THE PROBLEM

The correlation between core stability and athletic
performance has not been determined in the available
literature. Although several researchers have attempted to
quantify the relationship between core stability/strength
and functional performance, recent researchers suggested
that further research is needed to investigate important
components of core stability and the measurement of core
stability in relation to athletic performance.7,25
Therefore, the primary purpose of this study was to
examine the relationship the primary purpose of this study
is to examine the relationship among core power, core
strength, core stability, and athletic performance in
college soccer athletes. It is important to examine the
correlation to assess core power and its effect on athletic
performance because core power is an integrated component
of core stability, strength and endurance among dynamic
movement.
In addition to the lack of current scientific evidence
to support the correlation between core and athletic
performance, a valid core assessment has not established
yet. Therefore, the secondary purpose of this study is to

72

establish a valid assessment of core. It would be
beneficial to clarify the definition of core power, as a
component of core stability, and its effect on performance
in the field of sports science.

Definition of Terms
The following definitions of terms were defined for
this study:
1)

Core power - the combination of isometric core
stability and concentric core strength to perform a
task of sport performance that needs to produce
maximum speed and/or strength.15

2)

Core stability – the ability to control the position
and motion of the lumbo-pelvic-hip complex to allow
optimum production, transfer, and control of force and
motion to the terminal segment in integrated athletic
activities.3,15

3)

Core strength – the ability of the musculature to
generate force through contractile forces and intraabdominal pressure.15

4)

Dynamic balance - the ability to maintain equilibrium
or the center of gravity with proper body alignment in
motion.52

73

5)

Functional balance – the ability to maintain dynamic
balance for optimal extremity function, producing and
transferring force to the distal segments during
dynamic movement.

6)

Work - torque multiplied by angular displacement.10(p152153)

In other words, it is the area under the torque

curve where the torque curve is torque against angular
displacement.10

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

The subjects will be honest when they complete their
demographic sheets.

2)

The subjects will perform to the best of their ability
during testing sessions and adhere to the pre-test
conditions

3)

All tests and procedures are valid and reliable as
previously determined in the literature.

Limitations of the Study
The following is a possible limitation of the study:
The results in this study may be only applicable to
Division II men’s soccer players.

74

Significance of the Study
The purpose of the study was to examine whether the
core has a significant role in providing a base of support
for optimal lower extremity function and the ability to
produce and transfer force to the distal segments during a
functional soccer task, specifically maximal kicking
velocity. This study may be able to provide not only a
better explanation of the relationship between the core and
sport performance, but also a better concept of core
stability that is a base of all core functions. It may be
able to provide better idea of preventing and
rehabilitating athletic injury with the concept of kinetic
chain. It will also guide future studies that improve
training and sport performance with use of core training.

75

APPENDIX C
Additional Methods

76

APPENDIX C1
Informed Consent Form

77

78

79

80

Appendix C2
Subject Information/Individual Data Collection Sheet

81

Subject Information/Data collection Sheet
Subject #___________

Date______________

Date of Birth (Age):_________(___)

Position:____________

Type of kick used: Toe kick / Top of the foot / In-step (Please circle one)
Kicking leg: Right / Left

Year of soccer experience: _______

RS* Score (Right) RS 2 Score (Left)

RS Final Score

60s sit-ups # 1

DLLT angle 1

DLLT angle 2

DLLT angle 3

kicking Velocity 1 kicking Velocity 2 kicking Velocity 3

AVG

AVG

82

APPENDIX C3
Institutional Review Board –
California University of Pennsylvania

83

84

85

86

87

88

89

90

91

92

93

94

95

96

Institutional Review Board
California University of Pennsylvania
Morgan Hall, Room 310
250 University Avenue
California, PA 15419
instreviewboard@calu.edu
Robert Skwarecki, Ph.D., CCC-SLP,Chair

Dear Atsuko Takatani:
Please consider this email as official notification that your proposal titled
"A Correlation Among Core Stability, Core Strength, Core Power, and
Kicking Velocity in Division II College Soccer Athletes” (Proposal #11-043)
has been approved by the California University of Pennsylvania
Institutional Review Board as submitted.
The effective date of the approval is 2-28-2012 and the expiration date is 227-2013. These dates must appear on the consent form .
Please note that Federal Policy requires that you notify the IRB promptly
regarding any of the following:
(1) Any additions or changes in procedures you might wish for your
study (additions or changes must be approved by the IRB before
they are implemented)
(2) Any events that affect the safety or well-being of subjects
(3) Any modifications of your study or other responses that are
necessitated by any events reported in (2).
(4) To continue your research beyond the approval expiration date
of 2-27-2013 you must file additional information to be considered
for continuing review. Please contact instreviewboard@calu.edu
Please notify the Board when data collection is complete.
Regards,
Robert Skwarecki, Ph.D., CCC-SLP
Chair, Institutional Review Board

97

98

Appendix C4
Pictures: Equipment

99

Figure 1. FMS 2x6in board

100

Figure 2. Blood Pressure Cuff and 360º universal goniometer
for the Double Leg Lowering Test

101

Figure 3. JUGS™ radar gun

102

Appendix C5
Pictures: Rotary Stability Test (RS)

103

Figure 4. Rotatory stability given score 3

Figure 5. Rotatory stability given score 2

104

Figure 6. Rotatory stability given score 1

105

Appendix C6
Pictures: Double Leg Lowering Test

106

Figure 7. Double Leg Lowering Test – Starting Position

107

Figure 8. Double Leg Lowering Test

108

Appendix C7
Pictures: 60s Maximal Sit Up Test

109

Figure 9. 60s Maximal Sit Up Test – Starting position

110

Figure 10. 60s Maximal Sit Up Test

111

Appendix C8
Testing Directions

112

Double Leg Lowering Test
1. The researcher finds the subject’s Posterior Superior
Iliac Spine (PSIS) and places the blood pressure (BP)
cuff on the back while the client sits straight on the
floor
2. “Lay spine on the floor.”
3. The BP cuff is placed beneath the umbilicus
4. “Maintain the legs in full extension, or slightly
bended, and then flex hips to 90°.”
5. “Relax the abdominal muscles”
(The BP cuff is at 20 mmHg.)
6. “On the ‘Flatten out his back’ command, try to keep
your belly button towards the table.”
7. “Flatten out your back”
“Slowly lower the legs towards the floor, with
squeezing the core and keeping knee extension.”
8. The subject’s legs will be held once the BP cuff drops
below 20mmHg.
9. The hip angle is then measured with a goniometer to
determine the angle.
(Adapted from Prentice, 2004 and Zingaro, 2008)
60-s Maximum Sit-up
1. “Lay spine on the floor with knee flexion to 90° and
hip flexion to 45°.”
2. To another subject: “Step on the subject toes.”
3. “Interlock fingers behind head, but do not pull on
neck.”
4. “On ‘Go’ command, quickly perform sit-ups.”
5. “Make sure elbows touch thighs on up portion.”
6. “Lower trunk down to floor, let upper back touch
floor.”
7. “Make sure hands and head DO NOT touch floor.”
8. “Quickly perform as many sit-ups (i.e., up-down
cycles) as possible.”
9. “Ready, Go.”
(Adopted from Dendas, 2010)

113

Dynamic Warm-up
1. Jogging
Take 2 laps around the field
2. Hip External Rotation
Open hips, externally rotate hips and step to 45° with
skipping motion
repeat with opposite leg
3. Forward lunges
Step backward into lunge with right foot and contract
right glute
Twist your trunk and take your left elbow towards the
outside of the right knee
Push off with left foot and step forward into lunge
4. Backward lunges
Step backward into lunge with right foot and contract
right glute
Twist over the front leg by taking right elbow to the
outside of the left knee
Reverse the twist back to neutral and return to
standing position by pulling through with left hip
flexor, and immediately step into lunge with other leg
Continue for prescribed number of repetitions
5. Lateral squat
Shift your weight to the right, bending your right
knee and keeping your left knee straight
Turn to the back, shift your weight to the left,
bending your left knee and keeping your right knee
straight
6. High knees
Run 10 yards by alternately lifting your knees towards
chest as high as possible
Move your legs as quickly as possible
7. Butt kickers
Pull one ankle up toward butt alternately in running
10 yards

114

8. Side shuffle
Begin in an athletic ready position with feet hip
width apart.
Shuffle sideways towards the other side of corn.
9. Carioca
Cross one leg over the other as you move sideways
The shuffle goes side to side without crossing the
legs
10. A-skip
Skip for 10 yards, jump up as high as you can on each
skip
Swing your arms in opposition to your legs
11. Power skip
Skip for 10 yards, jump up and forward as much as you
can on each skip
Swing your arms in opposition to your legs
12. Straight Leg kick
Stand tall, kick leg up in front and reach for the
toes
Alternate legs while walking forward
13. Leg Swing (front/back and side)
Hold onto fence for support
Swing one leg front and back for 15 sec and alternate
Swing one leg side to side for 15 sec and alternate
14. Passing/kicking ball to partner for 5 minutes

Kicking test
 2 practice trials
 3 trials for records
Free to choose the type of your kicking and distance
of the run-up to the dead ball
Kick the ball towards the radar gun as hard as you can
Repeat the trials after 90 seconds rest

115

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121

Abstract

Title:

A CORRELATION AMONG CORE STABILITY, CORE
STRENGTH, CORE POWER, AND KICKING VELOCITY
IN DIVISION II COLLEGE SOCCER ATHLETES

Researcher:

Atsuko Takatani

Advisor:

Dr. Rebecca Hess

Date:

May 2012

Research Type:

Master’s Thesis

Context:

Recent studies suggest that further research
is needed to investigate important
components and measurement of core stability
in relation to athletic performance. The
correlation between core stability and
athletic performance has not been determined
in the available literature.

Objective:

The purpose of this study was to examine
the relationship among core power, core
strength, core stability, and athletic
performance in college soccer athletes.

Design:

A descriptive correlational design was used
to determine a relationship among core
power, core strength, core stability, and
athletic performance in college soccer
athletes.

Setting:

The testing was performed in a controlled
soccer field setting by the researcher.

Participants:

Eighteen Division II college male soccer
athletes volunteered this study that were
actively participating practice without any
limitations.

Interventions:

Each subject was tested on two days. All
subjects were tested by using the Rotatory
Stability test (RS), the 60s Maximum Sit-Up

122

test (60s MSUT), the Double Leg Lowering
test (DLLT), and the soccer kicking test
(SK). The RS was used to measure core
stability, the DLLT was used to measure
core strength, the 60s MSUT was used to
measure core power, and a dynamic soccerstyle kick (SK) was used to measure maximal
kicking speed.
Main Outcome
Measures:

RS score, 60s MSUT score, DLLT score, and
SK score were computed from all test trials
and correlation was examined among all four
variables. Existing data on TSPU scores
were additionally used for trunk stability.

Results:

There were no significant correlations
among the RS, the DLLT, the 60s MSUT and
the SK, for core stability, core strength,
core power and maximum kicking velocity in
healthy Division II 18 college soccer
athletes. A significant moderate low
correlation between the TSPU and the SK was
present (r = .435, P = .036).

Conclusion:

Trunk stability and kicking velocity
appears to be moderately related in healthy
Division II collegiate athletes. The core
tests that measure the isometric core
stability without dynamic limb movements
may be valid and reliable to assess core
stability.

Word Count:

363