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S86
Arc
Thoracolumbar Fascia
The thoracolumbar fascia acts as “nature’s back belt.” It
works as a retinacular strap of the muscles of the lumbar spine.
eprint requests to Venu Akuthota, MD, Univ of Colorado Health Science Center,
Box 6508, Mail Stop F493, Aurora, CO 80045, e-mail: venu.akuthota@uchsc.edu.
003-9993/04/8503-8950$30.00/0
oi:10.1053/j.apmr.2003.12.005
h Phys Med Rehabil Vol 85, Suppl 1, March 2004
ore Strengthening
nu Akuthota, MD, Scott F. Nadler, DO
STRACT. Akuthota V, Nadler SF. Core strengthening.
ch Phys Med Rehabil 2004;85(3 Suppl 1):S86-92.
Core strengthening has become a major trend in rehabilita-
n. The term has been used to connote lumbar stabilization,
tor control training, and other regimens. Core strengthening
in essence, a description of the muscular control required
und the lumbar spine to maintain functional stability. De-
te its widespread use, core strengthening has had meager
earch. Core strengthening has been promoted as a preven-
e regimen, as a form of rehabilitation, and as a performance-
ancing program for various lumbar spine and musculoskel-
l injuries. The intent of this review is to describe the
ilable literature on core strengthening using a theoretical
mework.
Overall Article Objective: To understand the concept of
e strengthening.
Key Words: Athletic injuries; Exercise; Low back pain;
habilitation.
© 2004 by the American Academy of Physical Medicine and
habilitation
ORE STRENGTHENING HAS BEEN rediscovered in
rehabilitation. The term has come to connote lumbar sta-
ization and other therapeutic exercise regimens (table 1). In
ence, all terms describe the muscular control required
und the lumbar spine to maintain functional stability. The
re” has been described as a box with the abdominals in the
nt, paraspinals and gluteals in the back, the diaphragm as the
f, and the pelvic floor and hip girdle musculature as the
ttom.1 Particular attention has been paid to the core because
erves as a muscular corset that works as a unit to stabilize
body and spine, with and without limb movement. In short,
core serves as the center of the functional kinetic chain. In
alternative medicine world, the core has been referred to as
“powerhouse,” the foundation or engine of all limb move-
nt. A comprehensive strengthening or facilitation of these
e muscles has been advocated as a way to prevent and
abilitate various lumbar spine and musculoskeletal disorders
as a way to enhance athletic performance. Despite its
despread use, research in core strengthening is meager. The
sent review was undertaken to describe the available liter-
re using a theoretical framework.
Stability of the lumbar spine requires both passive stiffness,
ough the osseous and ligamentous structures, and active
fness, through muscles. A bare spine, without muscles at-
hed, is unable to bear much of a compressive load.2,3 Spinal
tability occurs when either of these components is disturbed.
rom the Department of Rehabilitation Medicine, University of Colorado, Denver,
(Akuthota); and Department of Physical Medicine and Rehabilitation, University
edicine and Dentistry of New Jersey, Newark, NJ (Nadler).
o commercial party having a direct financial interest in the results of the research
oss instability is true displacement of vertebrae, such as with
umatic disruption of 2 of 3 vertebral columns. On the other
d, functional instability is defined as a relative increase in
range of the neutral zone (the range in which internal
istance from active muscular control is minimal).4 Active
fness or stability can be achieved through muscular cocon-
ction, akin to tightening the guy wires of a tent to unload
ight on the center pole (fig 1).5 Also described as the “serape
ect,”6 cocontraction further connects the stability of the
per and lower extremities via the abdominal fascial system.
e effect becomes particularly important in overhead athletes
ause that stability acts as a torque-countertorque of diago-
ly related muscles during throwing.6 The Queensland re-
rch group1 has suggested the differentiation of local and
bal muscle groups to outline the postural segmental control
ction and general multisegmental stabilization function for
se muscles groups, respectively (table 2).
ANATOMY
neral Overview
Stability and movement are critically dependent on the co-
ination of all the muscles surrounding the lumbar spine.
though recent research1,7,8 has advocated the importance of a
muscles (in particular, the transversus abdominis and mul-
di), all core muscles are needed for optimal stabilization and
formance. To acquire this cocontraction, precise neural in-
t and output (which has also been referred to as propriocep-
e neuromuscular facilitation) are needed.9 Pertinent anatomy
the lumbar spine is reviewed below; however, readers
uld refer to other texts for an extensive anatomic re-
w.1,5,10
seous and Ligamentous Structures
Passive stiffness is imparted to the lumbar spine by the
eoligamentous structures. Tissue injury to any of these
uctures may cause functional instability. The posterior ele-
nts of the spine include the zygapophyseal (facet) joints,
icle, lamina, and pars interarticularis. These structures are,
fact, flexible. However, repetitive loading of the inferior
icular facets with excessive lumbar flexion and extension
ses failure, typically at the pars. The zygapophyseal joints
ry little vertical load except in certain positions such as
essive lumbar lordosis.10 The intervertebral disk is com-
sed of the annulus fibrosis, nucleus pulposus, and the end-
tes. Compressive and shearing loads can cause injury ini-
lly to the endplates and ultimately to the annulus such that
sterior disk herniations result. Excessive external loads on
disk may be caused by weak muscular control, thus causing
icious cycle where the disk no longer provides optimal
sive stiffness or stability. The spinal ligaments provide little
bility in the neutral zone. Their more important role may be
provide afferent proprioception of the lumbar spine seg-
nts.11
Th
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Por
Table 1: Synonyms and Near-Synonyms for Core Strengthening
Lumbar stabilization
Table 2: Muscles of the Lumbar Spine
Global Muscles (dynamic, phasic, Local Muscles (postural, tonic,
S87CORE STRENGTHENING, Akuthota
e thoracolumbar fascia consists of 3 layers: the anterior,
ddle, and posterior layers. Of these layers, the posterior layer
the most important role in supporting the lumbar spine and
ominal musculature. The transversus abdominis has large
achments to the middle and posterior layers of the thoraco-
bar fascia.1 The posterior layer consists of 2 laminae: a
erficial lamina with fibers passing downward and medially
a deep lamina with fibers passing downward and laterally.
e aponeurosis of the latissimus dorsi muscle forms the
erficial layer. In essence, the thoracolumbar fascia provides
ink between the lower limb and the upper limb.12 With
traction of the muscular contents, the thoracolumbar fascia
s as an activated proprioceptor, like a back belt providing
dback in lifting activities (fig 1).
raspinals
There are 2 major groups of the lumbar extensors: the erector
nae and the so-called local muscles (rotators, intertransversi,
ltifidi). The erector spinae in the lumbar region are com-
sed of 2 major muscles: the longissimus and iliocostalis.
ese are actually primarily thoracic muscles that act on the
bar via a long tendon that attaches to the pelvis. This long
ment arm is ideal for lumbar spine extension and for creat-
posterior shear with lumbar flexion.3
Deep and medial to the erector spinae muscles lay the local
scles. The rotators and intertransversi muscles do not have
reat moment arm. Likely, they represent length transducers
position sensors of a spinal segment by way of their rich
position of muscle spindles. The multifidi pass along 2 or
spinal levels. They are theorized to work as segmental
bilizers. Because of their short moment arms, the multifidi
not involved much in gross movement. Multifidi have been
nd to atrophy in people with low back pain7 (LBP).
adratus Lumborum
The quadratus lumborum is large, thin, and quadrangular
ped muscle that has direct insertions to the lumbar spine.
ere are 3 major components or muscular fascicles to the
adratus lumborum: the inferior oblique, superior oblique,
longitudinal fascicles. Both the longitudinal and superior
lique fibers have no direct action on the lumbar spine. They
designed as secondary respiratory muscles to stabilize the
1. Muscular cocontraction via the thoracodor-
fascia produces active stability, similar to the
port that guy ropes provide to a tent secured
inst the wind. Adapted with permission from
terfield and DeRosa.5
Dynamic stabilization
Motor control (neuromuscular) training
Neutral spine control
Muscular fusion
Trunk stabilization
elfth rib during respiration. The inferior oblique fibers of the
adratus lumborum are generally thought to be a weak lateral
xor of the lumbar vertebrae. McGill13 states the quadratus
borum is a major stabilizer of the spine, typically working
metrically.
dominals
The abdominals serve as a vital component of the core. In
ticular, the transversus abdominis has received attention. Its
ers run horizontally around the abdomen, allowing for hoop-
e stresses with contraction. Isolated activation of the trans-
sus abdominis is achieved through “hollowing in” of the
omen. The transversus abdominis has been shown to acti-
e before limb movement in healthy people, theoretically to
bilize the lumbar spine, whereas patients with LBP have a
ayed activation of the transversus abdominis.8 The internal
lique has similar fiber orientation to the transversus abdomi-
, yet receives much less attention with regard to its creation
hoop stresses. Together, the internal oblique, external
lique, and transversus abdominis increase the intra-abdomi-
pressure from the hoop created via the thoracolumbar
cia, thus imparting functional stability of the lumbar spine.3
e external oblique, the largest and most superficial abdom-
l muscle, acts as a check of anterior pelvic tilt. As well, it
s eccentrically in lumbar extension and lumbar torsion.5
ally, the rectus abdominis is a paired, strap-like muscle of
anterior abdominal wall. Contraction of this muscle pre-
minantly causes flexion of the lumbar spine. In our opinion,
st fitness programs incorrectly overemphasize rectus abdo-
nis and internal oblique development, thus creating an im-
ance with the relatively weaker external oblique.14 The
ernal oblique can be stimulated by some of the exercises
cribed later, particularly those that emphasize isometric or
entric trunk twists (fig 2).15
p Girdle Musculature
The hip musculature plays a significant role within the
etic chain, particularly for all ambulatory activities, in sta-
torque producing) segmental stabilizers)
ectus abdominis Multifidi
xternal oblique Psoas major
ternal oblique (anterior fibers) Transversus abdominis
iocostalis (thoracic portion) Quadratus lumborum
Diaphragm
Internal oblique (posterior
fibers)
Iliocostalis and longissimus
(lumbar portions)
Arch Phys Med Rehabil Vol 85, Suppl 1, March 2004
R
E
In
Il
bil
the
and
abd
in people with lower-extremity instability or LBP.17,18 Nadler
et al19 showed a significant asymmetry in hip extensor strength
in female athletes with reported LBP. In a prospective study,
Na
str
the
fem
to
ext
kin
act
the
cha
bee
of
dis
do
exc
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com
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and
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spi
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the
abd
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ath
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spi
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spi
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mu
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Fig
obl
S88 CORE STRENGTHENING, Akuthota
Arc
ization of the trunk and pelvis, and in transferring force from
lower extremities to the pelvis and spine.16 Poor endurance
delayed firing of the hip extensor (gluteus maximus) and
uctor (gluteus medius) muscles have previously been noted
2. Example of a movement awareness exercise: here, external
ique muscles are activated with a controlled trunk twist.
h Phys Med Rehabil Vol 85, Suppl 1, March 2004
dler et al20 showed a significant association between hip
ength and imbalance of the hip extensors measured during
preparticipation physical and the occurrence of LBP in
ale athletes over the ensuing year. Overall, the hip appears
play a significant role in transferring forces from the lower
remities to the pelvis and spine, acting as 1 link within the
etic chain.
The psoas major is a long, thick muscle whose primary
ion is flexion of the hip. However, its attachment sites into
lumbar spine give it the potential to aid in spinal biome-
nics. During anatomic dissections, the psoas muscle has
n found to have 3 proximal attachment sites: the medial half
the transverse processes from T12 to L5, the intervertebral
k, and the vertebral body adjacent to the disk.10 The psoas
es not likely provide much stability to the lumbar spine
ept in increased lumbar flexion.3 Increased stability require-
nts or a tight psoas will concomitantly cause increased,
pressive, injurious loads to the lumbar disks.
aphragm and Pelvic Floor
The diaphragm serves as the roof of the core. Stability is
parted on the lumbar spine by contraction of the diaphragm
increasing intra-abdominal pressure. Recent studies21 have
icated that people with sacroiliac pain have impaired re-
itment of the diaphragm and pelvic floor. Likewise, venti-
ory challenges on the body may cause further diaphragm
sfunction and lead to more compressive loads on the lumbar
ne.22 Thus, diaphragmatic breathing techniques may be an
portant part of a core-strengthening program. Furthermore,
pelvic floor musculature is coactivated with transversus
ominis contraction.23
ercise of the Core Musculature
Exercise of the core musculature is more than trunk strength-
ng. In fact, motor relearning of inhibited muscles may be
re important than strengthening in patients with LBP. In
letic endeavors, muscle endurance appears to be more im-
rtant than pure muscle strength.24 The overload principle
ocated in sports medicine is a nemesis in the back. In other
rds, the progressive resistance strengthening of some core
scles, particularly the lumbar extensors, may be unsafe to
back. In fact, many traditional back strengthening exercises
y also be unsafe. For example, roman chair exercises or
k extensor strengthening machines require at least torso
ss as resistance, which is a load often injurious to the lumbar
ne.3 Traditional sit-ups are also unsafe because they cause
reased compression loads on the lumbar spine.15 Pelvic tilts
used less often than in the past because they may increase
nal loading. In addition, all these traditional exercises are
nfunctional.3 In individuals suspected to have instability,
etching exercises should be used with caution, particularly
es encouraging end range lumbar flexion. The risk of lumbar
ury is greatly increased (1) when the spine is fully flexed and
when it undergoes excessive repetitive torsion.25 Exercise
st progress from training isolated muscles to training as an
egrated unit to facilitate functional activity.
The neutral spine has been advocated by some as a safe place
begin exercise.26 The neutral spine position is a pain-free
sition that should not be confused with assuming a flat back
sture nor the biomechanic term “neutral zone” described by
njabi.4,27 It is touted as the position of power and balance.
wever, functional activities move through the neutral posi-
tio
tio
De
aw
dis
tra
pel
cis
pat
ma
app
wa
Gr
to
not adept at volitionally activating motor pathways require
facilitation in learning to recruit muscles in isolation or with
motor patterns. As well, some individuals with back injury will
do
kn
ph
ma
exe
Fu
cor
act
pro
and
lar
tot
Fig
sist
S89CORE STRENGTHENING, Akuthota
n, thus exercises should be progressed to nonneutral posi-
ns.
creasing Spinal and Pelvic Viscosity
Spinal exercises should not be done in the first hour after
akening because of the increased hydrostatic pressures in the
k during that time.28 The “cat and camel” and the pelvic
nslation exercises are ways to achieve spinal segment and
vic accessory motion before starting more aggressive exer-
es. As well, improving hip range of motion can help dissi-
e forces from the lumbar spine. A short aerobic program
y also be implemented to serve as a warmup. Fast walking
ears to cause less torque on the lower back than slow
lking.29
ooving Motor Patterns
The initial core-strengthening protocol should enable people
become aware of motor patterns. Some individuals who are
l to activate core muscles because of fear-avoidance behav-
.30 More time will need to be spent with these people at this
ge. Prone and supine exercises have been described to train
transversus abdominis and multifidi. Biofeedback devices
re used by the Queensland group and others to help facilitate
activation of the multifidi and transversus abdominis.1
rbal cues may also be useful to facilitate muscle activation.
r example, abdominal hollowing is performed by transversus
ominis activation; abdominal bracing is performed by co-
traction of many muscles including the transversus abdo-
nis, external obliques, and internal obliques. However, most
these isolation exercises of the transversus abdominis are in
nfunctional positions. When the trained muscle is “awak-
d,” exercise training should quickly shift to functional po-
ons and activities.
bilization Exercises
Stabilization exercises can be progressed from a beginner
el to more advanced levels. The most accepted program
ludes components from the Saal and Saal31 seminal dynamic
bar stabilization efficacy study (table 3). The beginner level
rcises incorporate the “big 3” (figs 3A–C) as described by
Gill.3 These include the curl-up, side bridge, and the “bird
g.” The bird dog exercise (fig 3C) can progress from 4-point
eeling to 3-point to 2-point kneeling. Advancement to a
ysioball (fig 4) can be done at this stage (table 4). Sahr-
nn14 also describes a series of lower abdominal muscle
rcise progression (table 5).
nctional Progression
Functional progression is the most important stage in the
e-strengthening program. A thorough history of functional
ivities should be taken to individualize this part of the
gram. Patients should be given exercises in sitting, standing,
walking. Sitting is often a problematic position, particu-
ly with lumbar disk injury. Sitting with lumbar lordosis
ally flattened shifts the center of gravity anteriorly, relative
3. The basic exercise triad for most stabilization programs con-
s of the (A) curl-up, (B) side bridge, and (C) bird dog exercises.
Arch Phys Med Rehabil Vol 85, Suppl 1, March 2004
fai
ior
sta
the
we
the
Ve
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abd
con
mi
of
no
ene
siti
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lev
inc
lum
exe
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cau
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wi
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for
tiv
sta
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mu
tiv
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pla
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(lu
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the
tes
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too
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of
req
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Table 5: Sahrmann’s Lower Abdominal Exercise Progression
Base position Supine with knees bent and feet on floor;
Da
S90 CORE STRENGTHENING, Akuthota
Arc
the standing position. This shift, in