ArticlePDF Available

The Role of Core Stability in Athletic Function

Authors:

Abstract and Figures

The importance of function of the central core of the body for stabilisation and force generation in all sports activities is being increasingly recognised. ‘Core stability’ is seen as being pivotal for efficient biomechanical function to maximise force generation and minimise joint loads in all types of activities ranging from running to throwing. However, there is less clarity about what exactly constitutes ‘the core’, either anatomically or physiologically, and physical evaluation of core function is also variable. ‘Core stability’ is defined 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. Core muscle activity is best understood as the pre-programmed integration of local, single-joint muscles and multi-joint muscles to provide stability and produce motion. This results in proximal stability for distal mobility, a proximal to distal patterning of generation of force, and the creation of interactive moments that move and protect distal joints. Evaluation of the core should be dynamic, and include evaluation of the specific functions (trunk control over the planted leg) and directions of motions (three-planar activity). Rehabilitation should include the restoring of the core itself, but also include the core as the base for extremity function.
Content may be subject to copyright.
Sports Med 2006; 36 (3): 189-198
C
URRENT
O
PINION
0112-1642/06/0003-0189/$39.95/0
2006 Adis Data Information BV. All rights reserved.
The Role of Core Stability in
Athletic Function
W. Ben Kibler,
1
Joel Press
2
and Aaron Sciascia
1
1 Lexington Clinic Sports Medicine Center, Lexington, Kentucky, USA
2 Rehabilitation Institute of Chicago, Chicago, Illinois, USA
The importance of function of the central core of the body for stabilisation and
Abstract
force generation in all sports activities is being increasingly recognised. ‘Core
stability’ is seen as being pivotal for efficient biomechanical function to maximise
force generation and minimise joint loads in all types of activities ranging from
running to throwing. However, there is less clarity about what exactly constitutes
‘the core’, either anatomically or physiologically, and physical evaluation of core
function is also variable.
‘Core stability’ is defined 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. Core
muscle activity is best understood as the pre-programmed integration of local,
single-joint muscles and multi-joint muscles to provide stability and produce
motion. This results in proximal stability for distal mobility, a proximal to distal
patterning of generation of force, and the creation of interactive moments that
move and protect distal joints. Evaluation of the core should be dynamic, and
include evaluation of the specific functions (trunk control over the planted leg)
and directions of motions (three-planar activity). Rehabilitation should include the
restoring of the core itself, but also include the core as the base for extremity
function.
1. What is the Core? to its local functions of stability and force genera-
tion, core activity is involved with almost all ex-
The musculoskeletal core of the body includes
tremity activities such as running, kicking and
the spine, hips and pelvis, proximal lower limb and
throwing. Therefore, the position, motion and con-
abdominal structures. The core musculature in-
tributions of the core must be evaluated and treated
cludes the muscles of the trunk and pelvis that are
as part of the evaluation and treatment of extremity
responsible for the maintenance of stability of the
spine and pelvis and help in the generation and
injuries.
transfer of energy from large to small body parts
This article provides a general functional defini-
during many sports activities.
[1,2]
The muscles and
tion of core stability, describes the anatomy and
joints of the hip, pelvis and spine are centrally
physiology of core muscles, discusses core stability
located to be able to perform many of the stabilising
in function and dysfunction, provides principles of
functions that the body will require in order for the
clinical evaluation of core stability, and describes
distal segments (e.g. the limbs) to do their specific
rehabilitation and conditioning programmes to max-
function, providing the proximal stability for the
imise the effect of core stability on athletic function.
distal mobility and function of the limbs. In addition
190 Kibler et al.
2. Definition of Core Stability single-joint segmental stabilisation that allow the
longer, multi-joint muscles to work more efficiently
Core stability is an important component max-
to control spine motions.
[5]
This combination of
imising efficient athletic function. Function is most
muscle activations helps create the ‘neutral zone’
often produced by the kinetic chain, the coordinated,
control of the spinal segments. In this ‘neutral zone’
sequenced activation of body segments that places
the ligaments see minimal tension.
[5-8]
the distal segment in the optimum position at the
The abdominal muscles consist of the transverse
optimum velocity with the optimum timing to pro-
abdominus, the internal and external obliques, and
duce the desired athletic task.
[2]
The core is impor-
rectus abdominus. Contracting the transverse ab-
tant to provide local strength and balance and to
dominus increases intra-abdominal pressure and
decrease back injury. In addition, since the core is
tensions the thoracolumbar fascia. The transverse
central to almost all kinetic chains of sports activi-
abdominals have been shown to be critical in
ties, control of core strength, balance and motion
stabilisation of the lumbar spine.
[9,10]
Abdominal
will maximise all kinetic chains of upper and lower
muscle contractions help create a rigid cylinder,
extremity function.
enhancing stiffness of the lumbar spine.
[11]
It is
There is no single universally accepted definition
important to note that the rectus abdominus and
of core stability. A general definition of core stabili-
oblique abdominals are activated in direction-spe-
ty that will be used in this article is the ability to
cific patterns with respect to limb movements, thus
control the position and motion of the trunk over the
providing postural support before limb move-
pelvis and leg to allow optimum production, transfer
ments.
[3,12-14]
Contractions that increase intra-ab-
and control of force and motion to the terminal
dominal pressure occur before initiation of large
segment in integrated kinetic chain activities.
segment movement of the upper limbs.
[15,16]
In this
manner, the spine (and core of the body) is stabilised
3. Anatomy, Physiology
before limb movements occur to allow the limbs to
and Biomechanics
have a stable base for motion and muscle activa-
tion.
[17]
Clinically, it has been shown that only a very
3.1 Anatomy
small increase in activation of the multifidi and
abdominal muscles is required to stiffen the spinal
The core acts as an anatomical base for motion of
segments (5% of maximal voluntary contraction for
the distal segments. This can be considered ‘proxi-
activities of daily living and 10% of maximal volun-
mal stability for distal mobility’ for throwing, kick-
tary contraction for rigorous activity).
[18]
ing or running activities.
[2,3]
Most of the prime mov-
Core stability requires control of trunk motion in
er muscles for the distal segments (latissimus dorsi,
all three planes. In order to provide stability in all
pectoralis major, hamstrings, quadriceps and iliop-
planes of motions, muscles may be activated in
soas) attach to the core of the pelvis and spine. Most
patterns that are different from their primary func-
of the major stabilising muscles for the extremities
tions. For example, the quadratus lumborum (QL)
(upper and lower trapezius, hip rotators and glutei)
muscle functions mainly as a stabiliser of frontal
also attach to the core.
plane flexion and extension activities. However, the
Numerous muscles make up the complex known
QL is attached from the transverse processes of the
as core muscles. Some are small, short muscles with
spine and the 12th rib to the iliac crests. This orien-
small lever arms to span single joints. These are
tation allows QL muscle activation that occurs in
activated in ‘length dependent’ muscle activation
association with flexion, extension and lateral bend-
patterns.
[4]
Others span numerous spinal segments
ing activities to buttress shearing of the spine in the
and function as prime mover muscles to integrate
plane of movement, making it more than just a
several joints and produce force. They are activated
frontal plane stabilising muscle.
[19]
in ‘force dependent’ activation patterns.
[4]
Coordina-
tion of both activation patterns is required in the The roof of the core muscle structures is the
multi-segmented structure like the spine. The mul- diaphragm. Simultaneous contraction of the dia-
tifidi are an example of short muscles that provide phragm, the pelvic floor muscles, and the abdominal
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
The Role of Core Stability in Athletic Function 191
muscles, is required to increase intra-abdominal 3.2 Physiology
pressure, providing a more rigid cylinder for trunk
support, decreasing the load on the spine muscles
Muscle activation in kinetic chain function is
based on pre-programmed patterns of muscle activa-
and allowing increased trunk stability.
[16,18,20]
The
tion that are task oriented, specific for the athletic
diaphragm contributes to intra-abdominal pressure
activity, and are improved by repetition. These pat-
before the initiation of limb movements, thereby
terns are grouped into the following two classes:
assisting spine/trunk stability. This activation occurs
length-dependent patterns, which confer stability
independently of the respiratory actions.
[21]
around one joint, are mediated by gamma affer-
At the opposite end of the trunk component of the
ent input and involve reciprocal inhibition of
core muscles are the pelvic floor muscles. Because
muscle to provide stiffness around a joint;
of the difficulty in directly assessing these muscles,
force-dependent patterns integrate activation of
they are also often neglected or ignored with respect
multiple muscles to move several joints and de-
to musculoskeletal rehabilitation. Synergistic acti-
velop force, and are mediated by Golgi tendon
receptors.
[4]
vation patterns exist involving the transverse
Force-dependent patterns of activation are
abdominus, abdominals, multifidi and pelvic floor
demonstrated in many aspects of core-related activi-
muscles that provide a base of support for all the
ties. Evaluation of muscle activation patterns in
trunk and spinal muscles.
[16]
association with rapid arm movement shows that the
The hips and pelvis and their associated struc-
first muscles to be activated are the contralateral
tures are the base of support for the core structures.
gastrocnemius/soleus,
[3]
and that patterns of activa-
Critical to functioning of the hip and pelvis are the
tion proceed up to the arm through the trunk.
[14,26]
many major muscle groups in this area. These mus-
Maximum foot velocity in kicking is more highly
cles have large cross-sectional areas and, in addition
related to hip flexor muscle activation than knee
extension.
[3]
A study of baseball throwing demon-
to their stabilising role, can generate a great deal of
strated that in all levels of pitching there is a pattern
force and power for athletic activities. The glutei are
of muscle activation that starts from the contralateral
stabilisers of the trunk over the planted leg and
external oblique and proceeds to the arm.
[26]
provide power for forward leg movements.
[2,22]
The
These muscle activation patterns also result in
hip/trunk area also contributes around 50% of the
increased levels of muscle activation in the extremi-
kinetic energy and force to the entire throwing mo-
ties, improving their capability to support or move
tion.
[23]
the extremity. Maximum gastrocnemius plantarflex-
The thoracolumbar fascia is an important struc-
or power is generated by use of the hip muscles.
ture that connects the lower limbs (via the gluteus
Twenty-six percent more activation can occur in the
maximus) to the upper limbs (via the latissimus
ankle as a result of proximal muscle activation.
[22]
Similarly, a 23–24% increase in maximal rotator
dorsi). This allows the core to be included in inte-
cuff activation occurs when the scapula is stabilised
grated kinetic chain activities such as throwing.
[24]
It
by the trapezius and rhomboid muscles, either in
covers the deep muscles of the back and trunk
asymptomatic or symptomatic individuals.
[27,28]
In
including the multifidi. The thoracolumbar fascia
addition, the distal muscle activity can be more
also has attachments to the internal obliques and
directed towards precision and control, rather than
transverse abdominus muscles, thus providing
power generation, when proximal muscle activation
three-dimensional support to the lumbar spine and
is maximum. This can be seen in the function of the
aiding core stability.
[24]
It helps to form a ‘hoop’
elbow muscles in throwing.
[26]
around the abdomen, consisting of the fascia poste-
Core muscle activation is used to generate rota-
riorly, the abdominal fascia anteriorly, and the ob-
tional torques around the spine. Most studies of
lique muscles laterally, which creates a stabilising
muscle activation demonstrate a differential pattern
corset effect.
[25]
of intensity and timing of muscle activation, starting
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
192 Kibler et al.
that minimise internal loads at the joint. There are
many examples of proximal core activation provid-
ing interactive moments that allow efficient distal
segment function. They either provide maximal
force at the distal end, similar to the cracking of a
whip, or they provide precision and stability to the
distal end. Maximum force at the foot segment in
kicking is developed by the interactive moment re-
sulting from hip flexion.
[2]
Maximum shoulder inter-
nal rotation force to rotate the arm is developed by
the interactive moment developed by trunk rota-
tion.
[2]
Maximum elbow varus torque to protect
against elbow valgus strain is produced by the inter-
active moment resulting from shoulder internal rota-
tion.
[2]
Maximal fast ball speed is correlated with the
interactive moment from the shoulder that stabilises
elbow and shoulder distraction
[29]
and produces el-
bow angular velocity.
[30]
Accuracy of ball throwing
is related to the interactive moment at the wrist
produced by shoulder movement.
[30]
As a result of the activations and interactive
moments, there is a proximal to distal development
Fig. 1. One-leg stance. No verbal cues are given. Attention should
be paid to alterations in posture or arm position.
of force and motion, according to the ‘summation of
speed’ principle
[2]
that includes core activation. This
on the contralateral side, that creates rotation as well
is not always a purely linear development strictly
as force generation.
[16,24,26]
from one segment to the next. In the tennis serve,
Finally, core muscle activation provides stiffness
to the entire central mass, making a rigid cylinder
that confers a long lever arm around which rotation
can occur and against which muscles can be
stabilised as they contract.
[16,24,25]
3.3 Biomechanics
Physiological muscle activation results in several
biomechanical effects that allow efficient local and
distal function. The pre-programmed muscle activa-
tions result in anticipatory postural adjustments
(APAs), which position the body to withstand the
perturbations to balance created by the forces of
kicking, throwing, or running.
[3,14]
The APAs create
the proximal stability for distal mobility.
The muscle activations also create the interactive
moments that develop and control forces and loads
at joints. Interactive moments are moments at joints
that are created by motion and position of adjacent
segments.
[2]
They are developed in the central body
segments and are key to developing proper force at
distal joints and for creating relative bony positions
Fi
g
. 2. Trendelenbur
g
position, with the contralateral hip dropped.
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
The Role of Core Stability in Athletic Function 193
the moment of inertia in these distal areas is less,
allowing the summation of higher velocities. Final-
ly, by allowing joint force control to be largely
influenced and controlled by pre-programmed mus-
cle activation patterns and interactive moments de-
veloped through core activation, instead of being
based on local ligament size or feedback-based local
muscle activation, the ligaments can be smaller in
size, and the smaller local muscles can be activated
for precision and control of performance variables.
5. Examples of Failure of Core Stability
Associated with Dysfunction
Weak hip muscles and resulting alteration of hip/
trunk position are a common finding associated with
knee injury. Weak hip abductors and tight hip flex-
ors are seen in association with anterior knee pain
and chondromalacia.
[33,34]
Alterations in hip muscle
Fig. 3. ‘Corkscrewing’ – using hip rotators to stabilise the trunk over
the planted le
g
in the presence of hip abductor weakness.
activity are associated with increased hip varus and
hip flexion positioning and increased knee valgus
elbow maximal velocity is developed before maxi-
positioning in squatting or landing manoeuvres, all
mal shoulder velocity. However, this general pattern
of which increase load on the anterior cruciate liga-
of force development from the ground through the
ment. A recent longitudinal study looked at core
core to the distal segment has been demonstrated in
stability parameters and found that weakness in hip
the tennis serve,
[23,31]
baseball throw
[26]
and kick.
[2]
external rotation was correlated with incidence of
Force control is also maximised through the core.
knee injury.
[35]
Based on these associations, most
The trunk is essential in re-acquiring the forward
rehabilitation and conditioning programmes for the
momentum in throwing,
[24]
and approximately 85%
knee now emphasise core stabilisation and hip
of the muscle activation to slow the forward-moving
strengthening.
[33,34,36]
arm is generated in the periscapular and trunk mus-
cles, rather than the rotator cuff.
[32]
4. Advantages of Core Stability
in Function
Core stability creates several advantages for inte-
gration of proximal and distal segments in generat-
ing and controlling forces to maximise athletic func-
tion. The larger, bulkier muscles in the central core
create a rigid cylinder and a large moment of inertia
against body perturbation while still allowing a sta-
ble base for distal mobility. In addition, it places
most of the ‘engine’ of force development in the
central core, allowing small changes in rotation
around the central core to effect large changes in
rotation in the distal segments, similar to the crack-
ing of the end of a whip. Because of the need for
relatively smaller mass in the peripheral segments,
Fig. 4. Sagittal plane evaluation. The shoulders should barely touch
the wall.
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
194 Kibler et al.
muscles to be tested should be tested in functional
positions when possible. If the muscle is mainly
used in a closed chain manner, it should be tested in
a closed chain manner. If the muscle is activated in
different planes of motion, it should be tested in
various planes of motion. If muscles are used prima-
rily in an eccentric manner, they need to be tested in
an eccentric manner. Often, to assess all of the
different muscles that function together to provide
core strength, evaluation of specific motion patterns
and quality of movement may be done.
[39,40]
This
method of analysis is harder to quantify, but is more
similar to actual three-planar core function. There is
no consensus regarding the most reliable or repro-
ducible evaluation system.
One option to assess core strength that incorpo-
Fi
g
. 5. Frontal plane evaluation.
rates many of these variables is to look at one-leg
standing balance ability, a one-leg squat, and a
Alteration of knee flexion has also been associat-
standing, three-plane core strength test. In a standing
ed with increased stresses in the arm. Tennis players
balance test, the patient is asked to stand on one leg
who did not have adequate bend in the knees, break-
with no other verbal cue (figure 1). Deviations such
ing the kinetic chain and decreasing the contribution
as a Trendelenburg posture or internally or external-
by the hip and trunk, had 23–27% increased loads in
ly rotating the weightbearing limb indicates inability
horizontal adduction and rotation at the shoulder and
to control the posture and suggests proximal core
valgus load at the elbow.
[37]
A mathematical analy-
weakness (figure 2).
sis of the tennis serve showed that a decrease in 20%
of the kinetic energy developed by the trunk resulted
A one-leg squat would be the next progressive
in a requirement of 34% more arm velocity or 80%
evaluation if the standing balance test is done well.
more shoulder mass to deliver the same energy to
Assuming the same starting point as the standing
the ball.
[23]
balance test, the patient is asked to do repetitive
Weakness or tightness at the hip can also affect
the arm. Decreased hip flexibility in rotation or
strength in abduction (positive Trendelenburg) was
seen in 49% of athletes with arthroscopically proven
posterior-superior labral tears.
[38]
6. How is Core Strength Evaluated?
There is no standard way that has been described
to measure core strength. Different investigators
have used different techniques to try to gauge the
relative strengths of specific core muscles via elec-
tromyogram data
[39]
and isometric dynamometer
values.
[40,41]
These data can give an approximate
estimate of core strength. Firing of numerous mus-
cles in task-specific patterns to provide core strength
makes evaluation of any specific single muscle as a
reference point questionable. Any evaluation tech-
nique will need to take into consideration that the
Fi
g
. 6. Transverse plane evaluation.
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
The Role of Core Stability in Athletic Function 195
patient stand 8cm away from the wall, and progress
like the sagittal plane test from bilateral weightbear-
ing to single-leg stance and alternately touch one
shoulder then the other just barely against the wall
(figure 6). Quality of motion and speed can be
assessed. With lesser degrees of core strength, there
is a greater breakdown in the ability to maintain
single-leg stance and the ability to just barely touch
Fi
g
. 7. Horizontal side support exercises.
the wall. This test will assess transverse plane mo-
tions that incorporate abdominal muscles, hip rota-
partial quarter to half squats with no other verbal
tors and spine extensors. Therapy can then be insti-
cues. Similar deviations in the quality of the move-
tuted based on the muscles and planes of motion that
ment are assessed as in the standing balance test. A
are found to be deficient.
Trendelenburg posture, which may not be noted on
standing balance, may be brought out with a single-
7. Principles of Core Rehabilitation
leg squat. The patient may use their arms for balance
Rehabilitation of the core should concentrate on
or may go into an exaggerated flexed or rotated
both the intrinsic needs of the core for flexibility,
posture (‘corkscrewing’) in order to put the gluteal
strength, balance and endurance, and on the function
or short rotator muscles on greater tension to com-
of the core in relation to its role in extremity func-
pensate for other muscular weakness (figure 3).
tion and dysfunction. A thorough pre-rehabilitation
Three-plane core testing is an attempt to quantify
examination including the core and the extremity is
core control in the different planes of spine and core
required prior to rehabilitation.
motion. Reliability and validity studies have not
The early focus is on the deficiencies discovered
been done on specific tests. Clinical experience has
during the pre-rehabilitation examination. These
demonstrated that this battery of tests does give
usually include both altered patterns of motion of
useful information that allows specific rehabilitation
the hip, trunk and shoulder, and actual weakness or
protocols to be instituted for increased core func-
inflexibilities of muscles, and may be seen locally or
tion. Testing is done with the patient standing a
distantly. Specific inflexibilities and weaknesses
given distance (usually 8cm) away from a wall. In
may be addressed locally by specific exercises, but
sagittal plane testing, they will be facing away from
motion patterns should be addressed on a global
the wall. They are asked to slowly move their body
level involving the entire kinetic chain motion. Re-
backwards, keeping their feet flat on the floor, to just
barely touch their head against the wall (figure 4).
Initially, this can be done with both legs on the
ground, then progressed to partial weightbearing on
each side and ultimately to single-leg standing. Sag-
ittal plane core strength testing creates eccentric
activation in the abdominals, the quadriceps and hip
flexor muscles, and concentric activation in the hip
and spine extensors. Frontal plane testing is done by
having the patient standing with one side then the
other 8cm away from the wall (figure 5). While
standing on the inside leg, they are asked to barely
touch their inside shoulder to the wall. This test
evaluates eccentric strength of the quadratus
lumborum, hip abductors, and some long spinal
muscles that are working in a frontal plane. Finally,
transverse plane motion is tested by having the
Fi
g
. 8. Isometric trunk rotation.
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
196 Kibler et al.
of rehabilitation is not only to restore core function
by itself, but also is the first stage of extremity
rehabilitation.
Progressions for lower extremity rehabilitation
include forward and side lunges, integrated trunk
rotation/hip rotations, and knee flexion/extensions
with trunk rotations.
[34,36]
The frequency and intensi-
ty of each of the exercises will depend on the indi-
vidual response to the exercises.
Shoulder and upper extremity rehabilitation may
begin with a posture of bilateral leg stance, hip
extension and trunk extension.
[36]
Activation pat-
terns may start with ipsilateral muscles and proceed
to contralateral activations. Diagonal patterns in-
Fig. 9. Diagonal trunk rotation around a stable base: starting posi-
tion.
volving trunk rotation around a stable base imitate
the throwing motion (figure 9, figure 10, figure 11).
habilitation for extremity injury should start with
The lower extremity activation drives the scapular
core emphasis.
and shoulder activation. All upper extremity exer-
In order to create a stable base, the rehabilitation
cises should end in the same position of trunk/hip
protocols start with the primary stabilising muscula-
extension. One method to assure this posture is to
ture such as the transverse abdominus, multifidus,
ask the patients to end with ‘the elbows in the back
and the quadratus lumborum. Due to their direct
pockets’. Progression for upper extremity rehabilita-
tion include integrated scapular retraction/arm ab-
attachment to the spine and pelvis, they are responsi-
duction/external rotation and ‘low rows’, integrated
ble for the most central portion of the core stability.
trunk extension/scapular retraction/arm extension
Exercises include the horizontal side support (figure
(figure 12) and hip/trunk rotation with scapular re-
7) and isometric trunk rotation (figure 8). This stage
traction (figure 13).
Core stabilisation should avoid emphasising the
use of single planar exercises that isolate specific
muscles or specific joints. They may be used at
times during the rehabilitation protocol, but empha-
sis should be on early progression to functional
Fi
g
. 10. Dia
g
onal trunk rotation: maximal external rotation. Fi
g
. 11. Dia
g
onal trunk rotation: cross bod
y
motion
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
The Role of Core Stability in Athletic Function 197
positions, motions and muscle activation sequences.
In this manner, normal physiological activations are
restored, which lead to restoration of normal biome-
chanical motions. Exercises may be started with the
extremity close to the body, decreasing the moment
arm, then progressing to more abducted positions,
increasing the forces and loads. The goal is to
achieve coordination of activation of the segments
throughout the entire kinetic chain.
Rehabilitation should be viewed as a ‘flow’ of
exercises that build a base of stability and force
generation, and then proceed distally to establish
control of the forces while allowing maximal mobil-
ity of the distal segment.
[42]
The core is the central
part of this flow. It acts as the base of stability and
the ‘engine’ of force generation, and also acts as the
controller to regulate the forces. Since it is involved
in many aspects of all athletic activities, it should be
evaluated as part of the workup of any extremity
injury, and should be rehabilitated prior to rehabili-
tation of the injured extremity.
Fig. 13. Hip/trunk rotation with scapular retraction. These may be
done in various planes of arm elevation.
8. Conclusion
be approximated by evaluations that reproduce the
three-planar motions that are used by the core to
Core stability is a pivotal component in normal
accomplish its functions. Better understanding of
athletic activities. It is best understood as a highly
the complex biomechanics and muscle activations
integrated activation of multiple segments that pro-
will allow more detailed evaluations and more spe-
vides force generation, proximal stability for distal
cific rehabilitation protocols.
mobility, and generates interactive moments. It is
difficult to accurately quantify by isolating individu-
Acknowledgements
al components, but its function or dysfunction can
No sources of funding were used to assist in the prepara-
tion of this review. The authors have no conflicts of interest
that are directly relevant to the content of this review.
References
1. Baechle TR, Earle RW, Wathen D. Resistance training. In:
Baechle TR, Earle RW, editors. Essentials of strength training
and conditioning. 2nd ed. Champaign (IL): Human Kinetics,
2000: 395-425
2. Putnam CA. Sequential motions of body segments in striking
and throwing skills. J Biomech 1993; 26: 125-35
3. Zattara M, Bouisset S. Posturo-kinetic organization during the
early phase of voluntary limb movement. J Neurol Neurosurg
Psychiatry 1988; 51: 956-65
4. Nichols TR. A biomechanical perspective on spinal mechanisms
of coordinated muscle activation. Acta Anat (Basel) 1994; 15:
1-13
5. Bergmark A. Stability of the lumbar spine: a study in mechani-
cal engineering. Acta Orthop Scand Suppl 1989; 230: 1-54
6. Panjabi M. The stabilizing system of the spine – part II: neutral
zone and stability hypothesis. J Spinal Disord 1992; 5: 390-7
Fig. 12. The low row exercise-integrated trunk extension/scapular
retraction/arm extension. It may be started isometrically and then
pro
g
ressed to isotonic motion.
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
198 Kibler et al.
7. Steffen R, Nolte LP, Pingel TH. Importance of back muscles in 27. Kebatse M, McClure P, Pratt N. Thoracic position effect on
rehabilitation of postoperative lumbar instability: a biome-
shoulder range of motion, strength, and 3-D scapular kinemat-
chanical analysis. Rehabilitation (Stuttg) 1994; 33: 164-70
ics. Arch Phys Med Rehabil 1999; 80: 945-50
8. Wilke HJ, Wolf S, Claes LE, et al. Stability increase of the
28. Kibler WB, Sciascia A, Dome DC. Evaluation of apparent and
lumbar spine with different muscle groups: a biomechanical in
absolute supraspinatus strength in patients with shoulder injury
vitro study. Spine 1995; 20: 192-8
using the scapular retraction test. Am J Sports Med. In press
9. Cresswell AG, Oddsson L, Thorstensson A. The influence of
29. Stodden DF, Fleisig GS, McLean SP, et al. Relationship of
sudden perturbations on trunk muscle activity and intra-ab-
dominal pressure while standing. Exp Brain Res 1994; 98 (2):
biomechanical factors to baseball pitching velocity: within
336-41
pitcher variation. J Appl Biomech 2005; 21: 44-56
10. Oddsson LI. Control of voluntary trunk movements in man:
30. Hirashima M, Kudo K, Ohtsuki T. Utilization and compensation
mechanisms for postural equilibrium during standing. Acta
of interaction torques during ball throwing movements. J
Physiol Scand Suppl 1990; 595: 1-60
Neurophysiol 2003; 89: 1784-96
11. McGill SM, Norman RW. Reassessment of the role of intra-
31. Marshall RN, Elliott BC. Long axis rotation: the missing link in
abdominal pressure in spinal compression. Ergonomics 1987;
proximal to distal segmental sequencing. J Sports Sci 2000;
30 (11): 1565-88
18: 247-54
12. Aruin AS, Latash ML. Directional specificity of postural mus-
cles in feed-forward postural reactions during fast voluntary
32. Happee R, van der Helm FC. Control of shoulder muscles
arm movements. Exp Brain Res 1995; 103 (2): 323-32
during goal-directed movements. J Biomech 1995; 28: 1170-
13. Hodges PW, Richardson CA. Feedforward contraction of trans-
91
versus abdominus is not influenced by the direction of the arm
33. McConnell J. The physical therapist’s approach to patel-
movement. Exp Brain Res 1997; 114: 362-70
lofemoral disorders. Clin Sports Med 2002; 21: 363-88
14. Cordo PJ, Nashner LM. Properties of postural adjustments
34. Malone T, Davies G, Walsh WM. Muscular control of the
associated with rapid arm movements. J Neurophysiol 1982;
patella. Clin Sports Med 2002; 21: 349-62
47: 287-302
35. Leetun DT, Ireland ML, Wilson JD, et al. Core stability mea-
15. Hodges PW, Butler JE, McKenzie DK, et al. Contraction of the
human diaphragm during rapid postural adjustments. J Physiol
sures as risk factors for lower extremity injury in athletes. Med
1997; 505 (Pt 2): 539-48
Sci Sports Exerc 2004; 36 (6): 926-34
16. Hodges PW. Core stability exercise in chronic low back pain.
36. Kibler WB, Livingston BP. Closed chain rehabilitation for
Orthop Clin N Am 2003; 34: 245-54
upper and lower extremities. J Am Acad Orthop Surg 2001; 9:
17. Jensen BR, Laursen B, Sjogaard G. Aspects of shoulder func-
412-21
tion in relation to exposure demands and fatigue. Clin Bi-
37. Elliott BC, Fleisig G, Nicholls R, et al. Technique effects on
omech (Bristol, Avon) 2000; 15 Suppl. 1: S17-20
upper limb loading in the tennis serve. J Sci Med Sport 2003;
18. Cholewicki J, Juluru K, McGill SM, et al. Intra-abdominal
6: 76-87
pressure mechanism for stabilizing the lumbar spine. J Bi-
omech 1999; 32 (1): 13-7
38. Burkhart SS, Morgan CD, Kibler WB. Throwing injuries in the
shoulder: the dead arm revisited. Clin Sports Med 2000; 19:
19. McGill SM. Low back stability: from formal description to
issues for performance and rehabilitation. Exerc Sports Sci
125-58
Rev 2001; 29: 26-31
39. McGill S. Low back disorders: evidence-based prevention and
20. Daggfeldt K, Thorstensson A. The role of intra-abdominal pres-
rehabilitation. Champaign (IL): Human Kinetics, 2002: 239-57
sure in spinal unloading. J Biomech 1997; 30 (11-12): 1149-55
40. Nadler SF, Malanga GA, Feinberg JH, et al. Functional per-
21. Ebenbichler GR, Oddsson LI, Kollmiter J, et al. Sensory motor
formance deficits in athletes with previous lower extremity
control of the lower back: implications for rehabilitation. Med
injury. Clin J Sport Med 2002; 12 (2): 73-8
Sci Sports Exerc 2001; 33: 1889-98
41. Nadler SF, Malanga GA, DePrince M, et al. The relationship
22. Van Ingen Schenau GJ, Bobbert MF, Rozendahl RH. The
between lower extremity injury, low back pain, and hip muscle
unique action of bi-articulate muscles in complex movements.
J Anat 1987; 155: 1-5
strength in male and female collegiate athletes. Clin J Sport
Med 2000; 10 (2): 89-97
23. Kibler WB. Biomechanical analysis of the shoulder during
tennis activities. Clin Sports Med 1996; 14: 79-85
42. Kibler WB, McMullen J. Rehabilitation of scapular dyskinesis.
In: Brotzman SB, Wilk KE, editors. Clinical orthopedic reha-
24. Young JL, Herring SA, Press JM, et al. The influence of the
spine on the shoulder in the throwing athlete. J Back Musculo-
bilitation. 2nd ed. St Louis (MO): Mosby, 2003: 244-50
skeletal Rehabil 1996; 7: 5-17
25. McGill SM. The lumbodorsal fascia, in low back disorders:
evidence based prevention and rehabilitation. Champaign (IL):
Correspondence and offprints: Aaron Sciascia, Lexington
Human Kinetics, 2002: 79-80
Clinic Sports Medicine Center, 1221 South Broadway, Lex-
26. Hirashima M, Kadota H, Sakurai S, et al. Sequential muscle
ington, KY 40504, USA.
activity and its functional role in the upper extremity and trunk
during overarm throwing. J Sports Sci 2002; 20: 301-10
E-mail: ascia@lexclin.com
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
... Furthermore, the spine is supported and the dynamic equilibrium is maintained by multifidus and transverse abdominal muscles. Internal abdominal pressure and thoraco-lumbar fascia tension will rise as the transverse abdominal muscles contract; this will stabilize the region (Kibler et al., 2006). ...
Article
The aim of this research was to examine the impact of pelvic girdle stability training in children with hypotonic cerebral palsy on functional sitting control. Thirty children with hypotonic cerebral palsy in both sexes, with their ages ranging from two to four years were used in the study. There were fifteen children in the experimental group and fifteen children in the control group. The study group received pelvic girdle stability training program in addition to a selected program for upper limbs and trunk muscles strengthening exercises, while the control group received only the selected program for upper limbs and trunk muscles strengthening exercises. Results revealed significant difference of GMFM88 (sitting domain) (P < 0.01), stationary raw scores and stationary standard scores of PDMS-2 (P < 0.05) but no significant difference of age equivalent of PDMS-2 (P > 0.05). GMFM88, on the other hand, had a significant difference (sitting domain) (P < 0.05) but no significant difference of stationary raw scores, stationary standard scores and age equivalent of PDMS-2 (P > 0.05) in the control group. Paired t-test were conducted for comparison between pre and post treatment mean values of sitting domain and stationary scores in each group. From the obtained results of the present study, we conclude that pelvic girdle stability training program was more effective in generating core muscle activity for functional sitting control compared to traditional physical therapy of upper limbs and trunk muscles strengthening exercises in children with hypotonic cerebral palsy. Keywords: Pelvic girdle stability, functional sitting control, hypotonic cerebral palsy.
... Merkez kuvvet sayesinde "core" kuvveti, denge ve hareket kontrolünü üst ve alt ekstremite fonksiyonlarını, tüm kinetik zincirin en üst düzeyine çıkarabilmektedir. 9 Vücudun stabilizasyonunun gelişmesinde katkı sağlayan başka bir egzersiz eğitimi ise Pilates'tir. Pilates yöntemi, Joseph H Pilates tarafından 1900'lü yılların başında kurulan beden ve zihin egzersiz kavramıdır. ...
... The core can be thought of as the kinetic link that facilitates the transfer of torques and angular momentum between the lower and upper extremities that is of vital importance for sport-specific and everyday activities in different age groups (Granacher, et al., 2014). The core region is considered the centre of the kinetic chain (Sever, 2016), a model that describes the body as an inter-segmental interconnected system that operates sequentially from proximal to distal to produce the desired activity in the distal segment (Kibler, Press & Sciascia, 2006). An effective core "transfers and controls strength and movement in functional athletic performance" in addition to providing optimum power generation (Akuthota & Nadler, 2004;Bıyıklı, 2018). ...
Article
Full-text available
The aim of this study is to investigate the effect of static and dynamic core exercises on motor performance and football-specific skills in 10-12 year old football players. 60 football players included in the study were randomly divided into three different groups: dynamic, static and control group. Dynamic and static core group athletes were applied core training program in addition to football training, 3 days a week for 10 weeks. Athletes in the control group only continued football training. Pre and post-test measurements of motor performance and football-specific skills have been taken from athletes. Paired-Samples T test was used in the intra-group pre and post-test comparisons regarding the effect of training, and the MANOVA test was used in the intergroup analysis. It was determined that some parameters of the football-specific skill and motor performance values of the athletes a significant differences subjected to static core exercises and the athletes in the control group. A significant difference was found between the pre and post-test values of all parameters of the athletes in dynamic core group. In addition, comparisons between groups at the end of week 10 revealed statistically significant differences in favor of the dynamic core group. As a result, it can be said that additional core training has an effect on football skills and motor performance in children, especially dynamic core exercises contribute significantly to the versatile development of 12 years-old football players.
... The core can be thought of as the kinetic link that facilitates the transfer of torques and angular momentum between the lower and upper extremities that is of vital importance for sport-specific and everyday activities in different age groups (Granacher, et al., 2014). The core region is considered the centre of the kinetic chain (Sever, 2016), a model that describes the body as an inter-segmental interconnected system that operates sequentially from proximal to distal to produce the desired activity in the distal segment (Kibler, Press & Sciascia, 2006). An effective core "transfers and controls strength and movement in functional athletic performance" in addition to providing optimum power generation (Akuthota & Nadler, 2004;Bıyıklı, 2018). ...
Article
Full-text available
The aim of this study is to investigate the effect of static and dynamic core exercises on motor performance and football-specific skills in 10-12 year old football players. 60 football players included in the study were randomly divided into three different groups: dynamic, static and control group. Dynamic and static core group athletes were applied core training program in addition to football training, 3 days a week for 10 weeks. Athletes in the control group only continued football training. Pre and post-test measurements of motor performance and football-specific skills have been taken from athletes. Paired-Samples T test was used in the intra-group pre and post-test comparisons regarding the effect of training, and the MANOVA test was used in the intergroup analysis. It was determined that some parameters of the football-specific skill and motor performance values of the athletes a significant differences subjected to static core exercises and the athletes in the control group. A significant difference was found between the pre and post-test values of all parameters of the athletes in dynamic core group. In addition, comparisons between groups at the end of week 10 revealed statistically significant differences in favor of the dynamic core group. As a result, it can be said that additional core training has an effect on football skills and motor performance in children, especially dynamic core exercises contribute significantly to the versatile development of 12 years-old football players.
... No contexto dos arremessos, os níveis de força, potência e resistência musculares do tronco, membros superiores e inferiores são considerados fatores importantes para o sucesso no judô 6 . Bons níveis de força e resistência da musculatura do tronco parecem contribuir para facilitar a transmissão de força, facilitar a transmissão das forças geradas nos membros inferiores e superiores, bem como auxiliar na manutenção do equilíbrio quando exposto a situações de arremessos pelo adversário 7 , o que pode ser observado em judocas, que apresentam escores nos testes de abdominais acima do percentil 80 das tabelas normativas 8 . Além disso, judocas mais graduados apresentam maior estabilidade de tronco em relação aos menos graduados, o que sugere que o desenvolvimento dessa musculatura é importante para o sucesso na modalidade 9 . ...
Article
Full-text available
Resumo O objetivo deste estudo foi analisar a relação dos parâmetros isocinéticos de tronco em atletas de judô de alta performance com parâmetros antropométricos e preferência de golpes específicos. Análise transversal em único centro. Parâmetros coletados: dados antropométricos; golpes de preferência; avaliação isocinética da coluna (tronco) em flexão e extensão com parâmetros de pico de torque, trabalho total e potência. Os testes isocinéticos foram realizados por um único observador com metodologia padronizada. Os parâmetros foram analisados para determinação da correlação dos dados da avaliação isocinética com os parâmetros antropométricos e os golpes de preferência. Foram incluídos 45 atletas (20 mulheres), idade média 22,7 anos, massa média 81,3 kg e média de tempo de prática do esporte de 14,5 anos. Tempo de prática e idade não tiveram correlação com os parâmetros isocinéticos. Foi observada correlação positiva da força do tronco com o peso(p<0,001). Em análise multivariada, foi possível observar que a adição do gênero masculino ao maior peso mostrou correlação forte ou muito forte(R entre 0,797 e 0,921; p<0,001) com maiores valores em flexão e extensão. Dentro os golpes de preferência, De-ashi-harai correlacionou com menos toque em extensão do tronco(p=0,034), Ko-uchi-gari com mais torque em extensão(p=0,033, respectivamente), Sasae com menor toque em extensão(p=0,024), e Kata-otoshi com maior toque e trabalho em flexão, respectivamente(p=0,024 e 0,034 respectivamente). No grupo de judocas de elite estudados neste trabalho foi possível observar que o peso esteve diretamente relacionado com a força do tronco, com efeitos aditivos do gênero masculino. Foram achadas correlações isoladas e fracas entre dados isocinéticos e alguns golpes específicos, assim podendo não ser uma relação direta entre força do tronco e preferência do gesto esportivo.
... The best core work is done in a sport-specific stance (standing), while maintaining the spine in an upright and erect position and allowing movement from the extremities in practical ways that place stress on the core (squat). (19), (20), (28) Posture will be much more challenged during two lifts positions (clean-snatch). The weight or resistance is placed above the head at arm's length, causing a shift in the body's center of gravity. ...
Article
Çalışmanın amacı somatotip karakter ile kor kaslarının stabilite ve enduransı arasındaki ilişkinin incelenmesidir. Düzenli fiziksel aktivite veya spora katılım kor kaslarının stabilite ve enduransını etkileyebileceğinden çalışma sağlıklı sedanter bireyler üzerinde yapılmıştır.Çalışma metodolojik türde kesitsel bir araştırma olup, örneklemini 18-45 yaş arası sedanter erkek gönüllüler oluşturmuştur. Katılımcıların somatotip karakter analizi Heath-Carter yöntemi ile, kor stabilitesi gövde fleksiyon, eksansiyon testi, sağ-sol yan köprü kurma testi ile, kor enduansı ise Mc Gill kor endurans testi ile değerlendirilmiştir. Çalışmaya katılan sağlıklı 48 erkek gönüllünün 10’nun ektomorfi somatotipinde, 30’unun endomorfi somatotipinde, 8’inin mezomorfi somatotipinde olduğu belirlendi. Farklı somatotipe sahip bireylerin antropometrik ölçümleri açısından anlamlı fark olduğu (p0.05). Yaş değişkenine göre ise endomorf somatotipinde yaş ile gövde fleksiyonu arasında negatif yönlü, ektomorfi somatotipinde ise yaş ile sol lateral köprü kurma testi arasında pozitif yönlü orta kuvvetli anlamlı ilişki bulundu (p
Article
Full-text available
The purpose of this study was to compare the shoulder and elbow joint loads during the tennis serve. Two synchronised 200 Hz video cameras were used to record the service action of 20 male and female players at the Sydney 2000 Olympics. The displacement histories of 20 selected landmarks, were calculated using the direct linear transformation approach. Ball speed was recorded from the stadium radar gun. The Peak Motus system was used to smooth displacements, while a customised inverse-dynamics program was used to calculate 3D shoulder and elbow joint kinematics and kinetics. Male players, who recorded significantly higher service speeds (male = 183 km hr(-1): female = 149 km hr(-1)) recorded significantly higher normalised and absolute internal rotation shoulder torque at the position when the arm was maximally externally rotated (MER) (male = 4.6% and 64.9 Nm: female = 3.5% and 37.5 Nm). A higher absolute elbow varus torque (67.6 Nm) was also recorded at MER, when compared with the female players (41.3 Nm). Peak normalised horizontal adduction torque (male = 7.6%: female = 6.5%), normalised shoulder compressive force (male = 79.6%: female = 59.1%) and absolute compressive force (male = 608.3 N: female = 363.7 N), were higher for the male players. Players who flexed at the front knee by 7.6 degrees, in the backswing phase of the serve, recorded a similar speed (162 km hr(-1)), and an increased normalised internal rotation torque at MER (5.0%), when compared with those who flexed by 14.7 degrees. They also recorded a larger normalised varus torque at MER (5.3% v 3.9%) and peak value (6.3% v 5.2%). Players who recorded a larger knee flexion also recorded less normalised and absolute (4.3%, 55.6 Nm) peak internal rotation torque compared with those with less flexion (5.6%, 63.9 Nm). Those players who used an abbreviated backswing were able to serve with a similar speed and recorded similar kinetic values. Loading on the shoulder and elbow joints is higher for the male than female players, which is a reason for the significantly higher service speed by the males. The higher kinetic measures for the group with the lower knee flexion means that all players should be encouraged to flex their knees during the backswing phase of the service action. The type of backswing was shown to have minimal influence on service velocity or loading of the shoulder and elbow joints.
Article
Full-text available
The neutral zone is a region of intervertebral motion around the neutral posture where little resistance is offered by the passive spinal column. Several studies--in vitro cadaveric, in vivo animal, and mathematical simulations--have shown that the neutral zone is a parameter that correlates well with other parameters indicative of instability of the spinal system. It has been found to increase with injury, and possibly with degeneration, to decrease with muscle force increase across the spanned level, and also to decrease with instrumented spinal fixation. In most of these studies, the change in the neutral zone was found to be more sensitive than the change in the corresponding range of motion. The neutral zone appears to be a clinically important measure of spinal stability function. It may increase with injury to the spinal column or with weakness of the muscles, which in turn may result in spinal instability or a low-back problem. It may decrease, and may be brought within the physiological limits, by osteophyte formation, surgical fixation/fusion, and muscle strengthening. The spinal stabilizing system adjusts so that the neutral zone remains within certain physiological thresholds to avoid clinical instability.
Article
Full-text available
The relatively large mass of the upper body and its elevated position in relation to the area of support during standing accentuate the importance of an accurate control of trunk movements for the maintenance of equilibrium. This fact has often been emphasized but never studied in detail. In this thesis the kinematics and motor patterns of simple voluntary trunk movements are investigated during standing. The analysis integrates neurophysiology and biomechanics using electromyographic (EMG) and optoelectronic techniques. Both the voluntary (primary movement) and the involuntary (associated postural adjustment) components of the movement are considered. The results demonstrate how the central nervous system (CNS) in its control of equilibrium utilizes biomechanical principles such as mechanical leverage of the different muscles and the interaction of active (muscle force) and passive forces (e.g. gravity and forces in stretched ligaments and/or muscles). Both primary and associated movements were found to be controlled by task specific and flexible muscle synergies which adapt to the mechanical demands of the situation. These task specific synergies were related to the amplitude, velocity and direction of the movement. Slow movements were often initiated through the action of gravity after a decrease or cessation of activity in postural muscles. Fast movements, however, were always initiated by a marked burst of activity in the agonist muscles. Significant relationships were observed between kinematical parameters (amplitude, duration and velocity) of fast trunk movements and temporal aspects of the EMG pattern. Multiple regression analysis indicated that the time to onset of muscle activity braking the ongoing trunk movement contained more information regarding the amplitude of the movement than did the duration of the initiating burst of activity in the prime mover. This supports the view that the initiating agonist burst is preprogrammed, whereas the braking antagonist burst may be influenced by peripheral feedback such as from muscle stretch receptors. In the early phase of a fast trunk flexion an unexpected flexion of the knees was observed. It is suggested that this knee flexion is a fast postural adjustment passively initiated as a mechanical consequence of the activation of muscles controlling the primary movement. This mechanism, which for anatomical reasons cannot act during an extension of the trunk, simplifies the feed-forward control of equilibrium during voluntary trunk flexion movements. For fast trunk extension movements a preactivation of ankle muscles occurred which resulted in a delay in the onset of the prime mover muscles when measured during a simple reaction time task.(ABSTRACT TRUNCATED AT 400 WORDS)
Article
Study design: This study investigated the influence of five different muscle groups on the monosegmental motion (L4-L5) during pure flexion/extension, lateral bending, and axial rotation moments. Objectives. The results showed and compared the effect of different muscle groups acting in different directions on the stability of a single motion segment to find loading conditions of in vitro experiments that simulate more physiologically reasonable loads. Summary of Background Data. In spine biomechanics research, most in vitro experiments have been carried out without applying muscle forces, even though these forces stabilize the spinal column in vivo. Methods. Seven human lumbosacral spines were tested in a spine tester that allows simulation of up to five symmetrical muscle forces. Changing pure flexion/extention, lateral binding, and axial rotation moments up to +/-3.75 Nm were applied without muscle forces, with different muscle groups and combinations. The three-dimensional monosegmental motion was determined using an instrumented spatial linkage system. Results. Simulated muscle forces were found to strongly influence load-deformation characteristics. Muscle action generally increased the range of motion and the natural zone of the motion segments. This was most evident for flexion and extension. After five pairs of symmetrical, constant muscle forces were applied (80 N per pair) the range of motion decreased about 93% in flexion and 85% in extension. The total natural zone for flexion and extension was decreased by 83% muscle action. The multifluids muscle group had the strongest influence. Conclusion. This experiment showed the important of including at least some of the most important muscle groups in invitro experiments in lumbar spine specimens.
Article
Analysis of shoulder dysfunction in throwing and overhead athletes can no longer be restricted to evaluation of the glenohumeral joint alone. The isolated shoulder is incapable of generating the force necessary to hurl a baseball at velocities of 90-100 miles per hour or serve a tennis ball in excess of 120 miles per hour. The purpose of this paper is to provide a literature based theoretical framework for the role of the spine during these activities. The spine is a pivotal component of the kinematic chain which functions as a transfer link between the lower and upper limbs, a force generator capable of accelerating the arm, and a force attenuator which dampens shear forces at the glenohumeral joint during the deceleration phase of the pitching motion. Side bending and rotation of the cervical spine facilitates visual acquisition of the intended target. Inflexibility of the hip musculature and weakness of the muscles which attach to the thoracolumbar fascia have profound effects upon spine function which secondarily places greater stress upon the glenohumeral joint and rotator cuff. Shoulder rehabilitation and injury prevention programs should include evaluation of and exercise regimens for the lumbar, thoracic and cervical spine.
From the mechanical point of view the spinal system is highly complex, containing a multitude of components, passive and active. In fact, even if the active components (the muscles) were exchanged by passive springs, the total number of elements considerably exceeds the minimum needed to maintain static equilibrium. In other words, the system is statically highly indeterminate. The particular role of the active components at static equilibrium is to enable a virtually arbitrary choice of posture, independent of the distribution and magnitude of the outer load albeit within physiological limits. Simultaneously this implies that ordinary procedures known from the analysis of mechanical systems with passive components cannot be applied. Hence the distribution of the forces over the different elements is not uniquely determined. Consequently nervous control of the force distribution over the muscles is needed, but little is known about how this achieved. This lack of knowledge implies great difficulties at numerical simulation of equilibrium states of the spinal system. These difficulties remain even if considerable reductions are made, such as the assumption that the thoracic cage behaves like a rigid body. A particularly useful point of view about the main principles of the force distributions appears to be the distinction between a local and a global system of muscles engaged in the equilibrium of the lumbar spine. The local system consists of muscles with insertion or origin (or both) at lumbar vertebrae, whereas the global system consists of muscles with origin on the pelvis and insertions on the thoracic cage. Given the posture of the lumbar spine, the force distribution over the local system appears to be essentially independent of the outer load of the body (though the force magnitudes are, of course, dependent on the magnitude of this load). Instead different distributions of the outer load on the body are met by different distributions of the forces in the global system. Thus, roughly speaking, the global system appears to take care of different distributions of outer forces on the body, whereas the local system performs an action, which is essentially locally determined (i.e. by the posture of the lumbar spine). The present work focuses on the upright standing posture with different degree of lumbar lordosis. The outer load is assumed to consist of weights carried on the shoulders. By reduction of the number of unknown forces, which is done by using a few different principles, a unique determination of the total force distributions at static equilibrium is obtained.(ABSTRACT TRUNCATED AT 400 WORDS)