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Anatomical and functional relationships between the external abdominal oblique muscle and the posterior layer of the thoracolumbar fascia

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The abdominal muscles are important for the stability of the lumbar region through the thoracolumbar fascia (TLF). However, there is not full agreement regarding the posterior continuity of the external abdominal oblique muscle (EO) with the TLF. To clarify this point, computed tomography (CT) images from 10 cadavers and 27 subjects were used to evaluate the continuity of the TLF with the abdominal muscles. The width of the fascial continuity of the EO with the posterior layer of TLF along the posterior border of the EO was also measured (40.70±3.92 mm). The epimysial fascia of the EO was in direct continuity with the posterior layer of the TLF in eight cadavers and 23 CT images, whereas in two cadavers and four CT images the epimysial fascia of the EO first fused with the fascia covering the latissimus dorsi, and then both fasciae were in continuity with the posterior layer of the TLF. Therefore, the fascial continuity of the EO could explain the transmission of tension from the EO to the posterior layer of the TLF and its importance in maintaining the stability of the lumbar spine through a hydraulic effect. Regarding fascial continuity in the trunk, and taking the EO into consideration, the TLF is formed by the fascia of all the abdominal muscles as the rectus sheath. In this manner, myofascial continuity between the TLF and the abdominal muscles is achieved through the aponeurosis and fascia, which ensures synchronization between the erector spinae and the rectus abdominis. This article is protected by copyright. All rights reserved.
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Original Communication
Anatomical and Functional Relationships
Between External Abdominal Oblique Muscle
and Posterior Layer of Thoracolumbar Fascia
CHENGLEI FAN,
1
CATERINA FEDE,
1
NATHALY GAUDREAULT,
2
ANDREA PORZIONATO,
1
VERONICA MACCHI,
1
RAFFAELE DE CARO ,
1
AND CARLA STECCO
1
*
1
Institute of Human Anatomy, Department of Neurosciences, University of Padova, Via Gabelli 65,
35127, Padova, Italy
2
School of Rehabilitation, Faculty of Medicine and Health Sciences, University of Sherbrooke, 3001, 12e
Avenue Nord, Sherbrooke, J1H 5N4, Canada
The abdominal muscles are important for the stability of the lumbar region
through the thoracolumbar fascia (TLF). However, there is not full agreement
regarding the posterior transversal continuity of the external abdominal oblique
muscle (EO) with the TLF. To clarify this point, 10 cadavers and computed
tomography (CT) images from 27 subjects were used to evaluate the transver-
sal continuity of the TLF with the abdominal muscles. The width of the fascial
continuity of the EO with the posterior layer of TLF along the posterior border of
the EO was also measured (40.70 3.92 mm). The epimysial fascia of the EO
was in direct continuity with the posterior layer of TLF in eight cadavers and
23 CT images, whereas in two cadavers and four CT images, the epimysial fas-
cia of the EO rst fused with the fascia covering the latissimus dorsi, and then,
both fasciae were in continuity with the posterior layer of TLF. Therefore, the
transversal fascial continuity of the EO could explain the transmission of tension
from the EO to the posterior layer of TLF and its importance in maintaining the
stability of the lumbar spine through a hydraulic effect. Regarding fascial conti-
nuity in the trunk, and taking the EO into consideration, the TLF is formed by the
fascia of all the abdominal muscles as the rectus sheath. In this manner, myo-
fascial continuity between the TLF and the abdominal muscles is achieved
through the aponeurosis and fascia, which ensures synchronization between the
erector spinae and the rectus abdominis. Clin. Anat. 9999:17, 2018. © 2018 Wiley
Periodicals, Inc.
Key words: external abdominal oblique muscle; fascia; lumbar; computed
tomography
INTRODUCTION
The abdominal muscles [external abdominal oblique
(EO), internal abdominal oblique (IO), transversus
abdominis (TrA) and rectus abdominis (RA)] are all
important in the stability of the lumbar region of the
vertebral column (Tesh et al., 1987). They create the
torque necessary to ex, rotate, and bend the spine
laterally (McGill, 1991; Arjmand et al., 2008), and
stiffen the abdominal cavity and lumbar spine (Prats-
Galino et al., 2015; Creze et al., 2018) during simple
*Correspondence to:Carla Stecco, Institute of Human Anatomy,
Department of Neurosciences, University of Padova, Via Gabelli
65, 35127 Padova, Italy. E-mail: carla.stecco@unipd.it
Received 27 June 2018; Revised 16 July 2018; Accepted 31
July 2018
Published online 00 Month in Wiley Online Library (wileyonlineli-
brary.com). DOI: 10.1002/ca.23248
© 2018 Wiley Periodicals, Inc.
Clinical Anatomy (2018)
tasks such as standing, sitting, and walking (Callaghan
et al., 1999; Masani et al., 2009) and dynamic loading
and heavy lifting (Cholewicki and McGill, 1996; El
Ouaaid et al., 2009). They also assist in the expiration
of air in challenged breathing (Campbell and Green,
1953). Nevertheless, relatively little is known about
the specic physiology and mechanics of these mus-
cles, which act individually and together as a compos-
ite, multifunctional structure in stabilizing the lumbar
region (Brown et al., 2010). In particular, there is not
full agreement regarding the anatomical connection of
the EO and the TLF.
The TLF is an essential structure in biomechanics
and there is much evidence that it works to connect the
latissimus dorsi (LD) and gluteus maximus (Gmax),
thus functionally linking the arm to the leg (Vleeming
et al., 1995; Mekonen et al., 2016; Wilke et al., 2016).
Actually, the connection between the TLF and the EO is
still a topic of debate. Indeed, Bogduk and Macintosh
(1984) and Grays Anatomy report that the superior
layer of the TLF is not in continuity with the EO or the
trapezius (Bogduk and Macintosh, 1984; Strandring,
2016), and Schuenke et al. (2012) stated that the
loose attachment of the EO to the underlying aponeu-
rosis does not support a major role of the EO in load
transfer to the lumbar spine, because there is no direct
contribution of the EO aponeurosis to the lateral border
of the TLF. This contrasts with the results of Barker
et al. (2004), who demonstrated the connection of the
EO to the lateral margin of theTLF at the level of L2. In
addition, electrophysiological (EMG) studies of animal
and human abdominal muscles have revealed conict-
ing results under different experimental conditions,
especially activation of the EO. Massé-Alarie
et al. (2016) reported that IO/TrA activation measured
by EMG was modulated across the kinesiophobic
phases of trunk exion/extension in chronic low back
pain and pain-free subjects, but not the EO. However,
Escamilla et al. (2010) found that roll-out and pike
were the most effective exercises for activating the RA,
EO, IO, and LD muscles, while minimizing the activities
of lumbar paraspinal and rectus femoris EMG
(Escamilla et al., 2010). Schuenke et al. and Vleeming
et al. also clearly described the anatomical connection
of the abdominal muscles (the TrA and IO) and TLF
through the lateral raphe(LR). The aponeurosis of
the TrA and IO bifurcates into anterior and posterior
laminae. The anterior lamina contributes to the middle
layer of the TLF. The posterior lamina contributes to the
deep lamina of the posterior layer of the TLF (three-
layer model). The junction of the TrA aponeurosis with
the paraspinal retinacular sheath (PRS) creates the
fat-lled lumbar interfascial triangle (LIFT), which is at
the core of the LR (Schuenke et al., 2012; Vleeming
et al., 2014). Willard et al. (2012) demonstrated that
the LIFT can function in the distribution of laterally
mediated tension to balance various viscoelastic pro-
prieties along the TFL. However, the results of anatomi-
cal and EMG studies of the connection of the EO and
the TLF are not in agreement. The transversal continu-
ity of the EO with the TLF and its contribution to spinal
stability has yet to be fully understood.
The purpose of this study was therefore to analyze
the posterior transversal continuity of the EO with the
TLF for better understanding of the transmission of
EO tension, and to elucidate how abdominal muscles
cooperate in inuencing lumbar stability.
MATERIALS AND METHODS
Anatomical study
An anatomical study (approved by the local ethical
committee) was carried out on 10 non-embalmed
cadavers (ve male and ve female, mean age at
death 68.4 years) managed by the Body Donation
Programof the Institute of Anatomy, University of
Padova following the framework of the Anatomical
Quality Assurance Checklist (Tomaszewski et al.,
2017; Henry et al., 2018). All cadavers displayed nor-
mal skin appearance without evidence of thoracolum-
bar region pathologies or surgery. A longitudinal
cutaneous incision was made in the midline in the thor-
acolumbar region. The skin, subcutaneous tissue, and
supercial fascia were removed in order to reach the
surface of the TLF, which was then exposed to allow its
characteristics and its relationships to the abdominal
muscles to be examined. The connection with the EO
was studied and, where there was such a connection,
the longitudinal width was measured unilaterally with a
measuring tape (1 mm). The posterior layer of the
TLF was then sectioned 2 cm laterally to the midline
and all the erector spinae (ES) were removed to facili-
tate analysis of the anterior layer of TLF and its con-
nections with the IO and TrA. The posterior portions of
the EO, IO and TrA belly were manually tractioned to
determine the effect in the TLF layers and to ascertain
whether specic lines of tension in the TLF could be
identied.
Computed tomography (CT) study
Twenty-seven subjects (n = 27) with no low back
pain or musculoskeletal pain were selected (12 male
and 15 female, mean age 59.5 years) from the
archives of a radiology center. Computed tomography
(CT) (Philips Medical Systems; Best, The Netherlands)
was used to assess the anatomical relationships
between the TLF and the abdominal muscles at various
vertebral levels. ImageJ was used for all morphometric
analyses of images. The following measurements were
recorded bilaterally: length of the common aponeuro-
sis (L
CA
) between the abdominal muscle and the lateral
border of the ES and the lumbar interfascial triangle
area (LIFT) (Fig. 4A).
Statistical analysis
Results are expressed as mean and standard devia-
tion (SD) and ranges; Studentst-test was used to com-
pare the right and left sides. Graph Pad Prism
6 (GraphPad Software Inc., San Diego, CA) was used to
test for statistically signicant differences (P < 0.05).
2 Fan et al.
RESULTS
Anatomical study
In the lower lumbar region (L4/L5), the EO was
covered by a thin epimysial fascia in continuity with
the posterior layer of the TLF laterally and directly in
eight subjects (Fig. 1A). In these eight specimens,
the aponeurosis of the LD had a more medial attach-
ment. In the other two subjects, it had a more lateral
attachment to the iliac crest. Consequently, in the lat-
ter cases the epimysial fascia of the EO and the LD
fused rst, and then, both were in continuity with the
posterior layer of the TLF (Fig. 1B). In these two
arrangements, the fascia of the EO, the LD and the
aponeurosis of the LD lay over the LR posteriorly. In
the upper lumbar region (L1/L2/L3), the epimysial
fascia of the EO was still fused with the epimysial fas-
cia of the LD; then the muscular bers of the EO
passed down the LD and were inserted in ribs V-XII.
However, continuity was conserved between the EO
fascia and the fascia of the inferior part of the serratus
posterior inferior muscle (SPI), both of which were in
continuity with the superior part of the posterior layer
of the TLF in all specimens (Fig. 2A). The fascial conti-
nuity width of the EO with the posterior layer of the
TLF along the posterior border of the EO was
40.70 3.92 mm (mean SD). There was no signi-
cant difference in the fascial continuity width between
males and females (P = 0.83) (Table 1). The multilay-
ered organization of the posterior layer of the TLF was
also evident macroscopically (Fig. 3A).
In the present study, we used the terminology of
the two-layer model of the TLF. It is very similar to the
three-layer model: the anterior layer of the two-layer
model becomes the middle layer of the three-layer
model, and the fascia of the two-layer model becomes
the anterior layer of the three layer. The common
aponeurosis and fascia of the IO and the TrA, espe-
cially the aponeurosis and fascia of the IO, bifurcated
into anterior and posterior laminae in all specimens.
The anterior lamina formed the anterior layer of the
TLF, attached medially to the tips of the transverse
processes of the lumbar vertebrae and the intertrans-
verse ligaments, and the posterior lamina contributed
to the posterior layer of the TLF. The aponeurosis and
fascia of the IO and TrA could be separated by blunt
dissection as far as the lateral border of the LR
(Fig. 2A, B). The LR was clearly evident in all speci-
mens, from the iliac crest to the 12th rib. The poste-
rior roof of the LR was composed not only of the
aponeurosis of the LD, IO, but also of the fascia of the
EO and LD, especially in the lower lumbar region
(L4) (Fig. 2A). After all the ES had been removed, it
was possible to appreciate the different orientation of
the brous bundles forming the anterior layer of the
TLF (Fig. 3B). On the transverse plane, the common
aponeurosis and fascia of the IO and TrA bifurcated
into anterior and posterior laminae, whereas the LR
was a fat-lled LIFT, mainly composed of the junction
of the common aponeurosis and the fascia of the IO
and TrA with the paraspinal retinacular sheath
(Fig. 2C).
CT study
In the lower lumbar region (L4/L5), CT imaging
conrmed the direct transversal continuity of the epi-
mysial fascia of the EO with the posterior layer of TLF
at L4 in 23 subjects (Fig. 4A); in four subjects, the
epimysial fascia of the EO fused rst with the fascia of
the LD. The muscular bers of the LD began to appear
at level L3 and the epimysial fascia of the EO was still
fused with that of the LD. The common aponeurosis of
the IO and TrA (L
CA
) passed over the QL and then sub-
divided into the anterior and posterior laminae at the
lateral border of the ES in the lower region. However,
the muscular bers of the TrA had a more posterior
attachment in the aponeurosis, and that of the IO
bifurcated into anterior and posterior laminae in
seven subjects; in the other 20 subjects, the
Fig. 1. A: Asterisk (*):direct transversal fascial conti-
nuity of EO and posterior layer of TLF;: direct fascial
continuity of EO and LD in superior region. B: Asterisk
(*): rst fascial continuity of EO and LD, and then both in
continuity with posterior layer of TLF. Gmax: gluteus
maximus; Gmed: gluteus medius; EO: external oblique:
LD: latissimus dorsi: PTLF: posterior layer of TLF. [Color
gure can be viewed at wileyonlinelibrary.com]
Anatomical and Functional Relationships Between the External Abdominal Oblique Muscle 3
muscular bers of the TrA had a more anterior attach-
ment to the aponeurosis and those of the IO and TrA
merged, so that the layers of the aponeurosis and fas-
ciae of the IO and TrA could not be distinguished in
those subjects. The anterior lamina contributed to the
anterior layer of the TLF, and the posterior lamina
contributed to its posterior layer (Figs. 4B,C,E,F). At
the level of L4, the L
CA
(mean SD) between the
abdominal muscles and the lateral border of the ES
was 50.00 24.61 mm on the left side and
45.03 18.45 mm on the right. The LIFT area
(mean SD) was 44.57 8.94 mm
2
on the left side
and 44.82 9.08 mm
2
on the right. There was no sig-
nicant difference between left or right sides (L
CA
P = 0.54, area P = 0.94) (Fig. 4A, Table 2). In the
upper lumbar region (L1/L2), the muscular bers of
the OE passed down the LD, and the epimysial fascia
of the EO could not be separated from the fascia of
the IO, TrA, LD or SPI, since they merged in all speci-
mens (Fig. 4D).
DISCUSSION
This study demonstrates the transversal fascial
continuity of the EO with the posterior layer of the
TLF, both in dissected cadavers and in CT images of
the lower lumbar region (L4/L5). This connection is
only possible via the epimysial fascia of the EO; in any
case, no direct insertion of the muscular bers of the
EO into the TLF was observed.
Our results show that, when the aponeurosis of the
LD is inserted into the medial border of the iliac crest
(80% of cases), the epimysial fascia of the EO is in
direct transversal continuity with the posterior layer
of the TLF. In other subjects, the aponeurosis of the
LD is inserted more laterally into the iliac crest, and
Fig. 2. A: After removal of LD, asterisk (*): fascial
continuity of EO with inferior part of serratus posterior
inferior muscle. B: After removal of LD and EO, note fas-
cia and aponeurosis continuity of IO with TLF (A); fused
fascia and aponeurosis of IO and TrA (B and C). C: Lum-
bar interfascial triangle (LIFT) at level of L4. Note fatty
composition of LIFT (*). EO: external oblique; IO: inter-
nal oblique; LD: latissimus dorsi; SPI: serratus posterior
inferior muscle; Gmax: gluteus maximus; Gmed: gluteus
medius; LR: lateral raphe; ES: erector spinae; CA: com-
mon aponeurosis and fascia of abdominal muscle; PTLF:
posterior layer of TLF; ATLF: anterior layer of TLF. [Color
gure can be viewed at wileyonlinelibrary.com]
Fig. 3. A: Macroscopic aspect of posterior layer of
TLF. B: Macroscopic aspect of anterior layer of TLF. A:
anterior lamina and fascia of IO and/or TrA; B: aponeuro-
sis and fascia of TrA. Dotted lines: different orientation of
multilayered brous bundles; arrow: main direction of
muscular traction. EO: external oblique; IO: internal obli-
que; TrA: transversus abdominis; LD: latissimus dorsi;
Gmax: gluteus maximus. [Color gure can be viewed at
wileyonlinelibrary.com]
4 Fan et al.
consequently the epimysial fascia of the EO and LD
fused rst, and then, both were in continuity with the
posterior layer of the TLF. In the upper lumbar region,
transversal fascia continuity still remains between the
EO and the lower part of the serratus posterior inferior
muscle rst, then both are in continuity with the upper
part the posterior layer of the TLF in all specimens.
Indeed, there are three myofascial laminae in the
trunk (supercial, middle, and deep), The supercial
lamina envelops the LD and the EO of the trunk
through the fascial continuity that permits these mus-
cles work synergistically in spiral/rotational move-
ments. Therefore, our results conrm the work of
Schuenke et al. (2012) in that the EO shows no muscle
insertion into the TLF. However, we also demonstrate
Fig. 4. CT imagings,A: showing fascia continuity of EO and posterior layer of TLF
(red arrow ") at L4. Lumbar interfascial triangle (LIFT, red triangle) was located
between both layers of TLF. B: showing aponeurosis and fascia of IO which bifurcates
into anterior and posterior lamina (red arrow") at L3. Aponeurosis and fascia of TrA
(yellow arrow "). C: merged aponeurosis and fascia of IO and TrA, bifurcating into
anterior and posterior lamina (red arrow") at L3. D: merged fascia of EO, IO, LD and
SPI (red arrow") at L1/2. Scheme of myofascial continuity between TLF and abdomi-
nal muscle (E and F). E: aponeurosis of IO, bifurcating into anterior and posterior lam-
ina, F: aponeurosis of IO and TrA, merging and then bifurcating into anterior and
posterior lamina. EO: external oblique; IO: internal oblique: TrA: transversus abdomi-
nis; ES: erector spinae; QL: quadratus lumborum muscle; Psoas: psoas muscle; LD:
latissimus dorsi; CA: common aponeurosis length between abdominal muscles and
lateral border of ES; RA: rectus abdoninis; LR: lateral raphe. [Color gure can be
viewed at wileyonlinelibrary.com]
TABLE 1. Cadaver parameters and the fascial
continuity width (n = 10)
Attachment Gender Age Width(mm)
Directly M 70 45.00
M 62 39.00
M 79 39.00
M 64 38.00
F 83 47.00
F 59 40.00
F 73 42.00
F 63 41.00
Indirectly M 56 43.00
F 75 33.00
Anatomical and Functional Relationships Between the External Abdominal Oblique Muscle 5
that its fascia contributes to forming the posterior layer
of the TLF, indicating that the EO can also contribute to
the tension of the TLF.
Schuenke et al. (2012) reported that the aponeu-
rosis of the transversus abdominis (TrA) and internal
abdominal oblique (IO) is subdivided into anterior and
posterior laminae, which join the paraspinal retinacu-
lar sheath separately. However, on T1 MRI tracing,
the authors only stated that the aponeurosis of the
TrA subdivides into anterior and posterior laminae
(Schuenke et al., 2012). Our studies showed that the
aponeurosis and fascia of the IO (seven subjects) and
the merged aponeurosis and fascia of the IO and TrA
(20 subjects) bifurcate into anterior and posterior
laminae. The anterior lamina contributes to the ante-
rior layer of the TLF, whereas the posterior lamina
contributes to its posterior layer in CT images
(Fig. 4A, B, C, E, F). Anatomical study shows that the
common aponeurosis and fascia of the IO and TrA,
especially the aponeurosis and fascia of the IO, bifur-
cate into anterior and posterior laminae in all speci-
mens, whereas the aponeurosis and fascia of the IO
and TrA can be separated by blunt dissection as far as
the lateral border of the LR. Theobald et al. (2007)
and Schuenke et al. (2012) reported that the LR could
reduce friction between adjacent fascia under the
high tension generated by the abdominal myofascial
girdle. Our previous studies showed that the epimy-
sial fasciae of the EO, IO and TrA were separated by a
thin layer of loose connective tissue (Stecco et al.,
2011; Stecco et al., 2018). In addition, Brown and
McGill (2009) demonstrated that force generated by
abdominal muscles can be passed one to another
through connective tissue links. Therefore, the
abdominal muscles interact through connective tissue
during trunk movements. In this way, the EO medi-
ates tension in the posterior layer of the TLF, either
directly by the continuity of the epimysial fascia, or
indirectly by the interactions with the other abdominal
muscles through connective tissue. Our ndings
extend these results of the relationship between the
abdominal region and the lumbar segment. Thanks to
the transversal fascial continuity of the EO with the
posterior layer of the TLF, the former is also important
in the mechanical coordination of the lumbar region.
Regarding fascial continuity in the trunk, also tak-
ing the EO into consideration, the similar organization
of the lumbar region on both sides of the body is clear.
Indeed, the TLF is formed by the fascia of all the
abdominal muscles as the rectus sheath. Above all,
when we examine the rectus sheath above the line of
Douglas, we see that the aponeurosis of the IO is
subdivided into two laminae: the upper one fuses with
the aponeurosis of the EO to form the anterior layer
of the rectus sheath, and the deep one fuses with the
aponeurosis of the TrA to form the posterior layer of
the rectus sheath (Strandring, 2016). In a similar
manner, in the lumbar region, the aponeurosis of the
IO subdivides into two laminae: the upper one fuses
with the epimysial fascia of the EO and the aponeuro-
sis of the LD to form the posterior layer of the TLF,
whereas the anterior lamina fuses with the aponeuro-
sis of the TrA to form its anterior layer. Thus, the
abdominal muscles functionally connect the RA with
the ES, permitting their activation to be synchronized.
The LR can be considered as corresponding to the Spi-
gelian line in the front part of the trunk. Lastly, since
muscle contraction inside a rigid compartment is
more efcient (the hydraulic effect described by Gra-
covetsky et al., 1981; Gracovetsky et al., 1985), con-
traction of the abdominal muscles can simultaneously
stretch both the rectus sheath and the TLF. This
mechanism can probably better explain the role of the
abdominal muscles in protecting the back.
As regards the factors that inuence the degree of
continuity, our study revealed no signicant difference
in fascial continuity width between males and
females. Further studies should reveal how age and
physical activity inuence the degree of continuity
quantitatively and how the EO functionally cooperates
with other abdominal muscles (RA, IO, TrA) at a deep
level, especially during trunk movements.
ACKNOWLEDGMENTS
The authors express their gratitude to the donation
of cadavers to the Human Anatomy Section of the
Department of Neuroscience of the University of
Padova within the context of the Body Donation Pro-
gram. The authors declare that they have no conict
of interests.
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CA
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Anatomical and Functional Relationships Between the External Abdominal Oblique Muscle 7
... The musculature of the LAW and of the PF [10] maintains a close relationship with the lumbar and pubic regions. This musculature, together with the diaphragm [11], has a determining role in mechanical coordination [12] to ensure the stability of the tidal volume and the abdomino-lumbo-pelvic segment. For the action of this musculature of the cavity to be executed in a physiological and adequate manner, it is essential that there is harmony in the totality of the curves of the spine. ...
... The musculature of the LAW and of the PF [10] maintains a close relationship with the lumbar, and pubic regions. This musculature, together with the diaphragm [11], has a determining role of mechanical coordination [12] to ensure the stability of the tidal volume and the abdomino-lumbo-pelvic segment. For the action of this musculature of the cavity to be executed in a physiological and adequate manner, it is essential that there is harmony in the totality of the curves of the spine. ...
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Low back pain represents the leading cause of disability since 1990. In 90% of cases, it is classified as non-specific low back pain, being chronic in 10% of subjects. Ultrasound has proven to be an effective measurement tool to observe changes in the activity and morphology of the abdominal muscles. This article reviews which core synergies are studied with ultrasound in healthy subjects and with chronic non-specific low back pain. A systematic review was conducted on studies analyzing synergies between two or more core muscles. Publications from 2005 until July 2021 were identified by performing structured searched in Pubmed/MEDLINE, PEDro and WOS. Fifteen studies were eligible for the final systematic review. A total of 56% of the studies established synergies between the core muscles and 44% between the homo and contralateral sides of the core muscles. The most studied core synergies were transversus abdominis, internal oblique and external oblique followed by the rectus abdominis and the lumbar multifidus. No studies establishing synergies with diaphragm and pelvic floor were found. Eight studies were conducted in healthy subjects, five studies in subjects with chronic non-specific low back pain compared to healthy subjects and two studies in subjects with chronic non-specific low back pain.
... In oblique musculature, the EO would be less affected by AH than the IO; the EO is a more global torque-producing muscle that exhibits less involved in segmental spinal stability [40]. However, the medial fibers of the EO are anatomically associated with the thoracolumbar fascia; they are presumed to provide some biomechanical stability [41,42]. Thus, the IO and TrA are expected to function in a synergistic manner to flatten the abdomen during AH [43]. ...
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Pilates methods use mats for trunk muscles stabilization exercises, and leg pull front (LPF) is one of the traditional Pilates mat exercises. Abdominal hollowing (AH) and Abdominal bracing (AB) maneuvers are recommended to stabilize the trunk muscles and prevent unwanted pelvic movement during motion. This study aimed to explore the effects of AH and AB on electromyography (EMG) activity of the trunk muscles and angle of pelvic rotation during LPF. A total of 20 healthy volunteers participated in the study. AH, AB, and without any condition (WC) were randomly performed during LPF exercise. Each was repeated three times for 5 s. The trunk muscle activities were measured using EMG and rotation of pelvis was measured using a Smart KEMA device. The activities of the transversus abdominis/obliquus internus abdominis (TrA/IO) and right obliquus externus abdominis (EO) muscles were highest in LPF-AH compared to the other conditions. Multifidus (MF) activity was significantly greater in LPF-AH and LPF-AB compared to that of without any condition. The pelvic rotation angle was significantly smaller in LPF-AB. Therefore, AH maneuver during LPF for trunk muscle stabilization exercises is suitable for selective activation of the TrA/IO, and AB maneuver during LPF is recommended for the prevention of unwanted pelvic rotation.
... The musculature of the abdominal wall and of the pelvic floor (PF) [7] maintains a close relationship with the lumbar, and pubic regions. This musculature, together with the diaphragm [5], has a determining role of mechanical coordination [8] to ensure the stability of the TV and the abdomino-lumbo-pelvic segment. For the action of this musculature of the cavity to be executed in a physiological and adequate manner, it is essential that there be harmony in the totality of the curves of the spine. ...
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One of the advances in physiotherapy in recent years is the exploration and treatment by ultrasound imaging. This technique makes it possible to study the relationship between the musculature of the anterolateral wall of the abdomino-pelvic cavity, the pelvic floor muscles and the diaphragm muscle, among others, and thus understand their implication in non-specific low back pain (LBP) in pathological subjects regarding healthy subjects. Objective: To evaluate by RUSI (rehabilitative ultrasound imaging) the muscular thickness at rest of the abdominal wall, the excursion of the pelvic floor and the respiratory diaphragm, as well as to study their activity. Methodology: Two groups of 46 subjects each were established. The variables studied were: non-specific low back pain, thickness and excursion after tidal and forced breathing, pelvic floor (PF) excursion in a contraction and thickness of the external oblique (EO), internal oblique (IO) and transverse (TA) at rest. Design: Cross-sectional observational study. Results: Good-to-excellent reliability for measurements of diaphragm thickness at both tidal volume (TV) (inspiration: 0.763, expiration: 0.788) and expiration at forced volume (FV) (0.763), and good reliability for inspiration at FV (0.631). A correlation was found between the EO muscle and PF musculature with respect to diaphragmatic thickness at TV, inspiration and expiration, and inspiration at FV, in addition to finding significant differences in all these variables in subjects with LBP. Conclusion: Subjects with LBP have less thickness at rest in the OE muscle, less excursion of the pelvic diaphragm, less diaphragmatic thickness at TV, in inspiration and expiration, and in inspiration to FV.
... Iatrogenic muscle damage [3] can impact the spinal balance [4], the loading conditions on adjacent segments [5] and the passive stability of the spine in general [6]. Similarly, the thoracolumbar fascia is believed to be an important stabilizer of the spine [7,8]. By surrounding the erector spinae, it is hypothesized to provide an additional hydrostatic stabilizing effect [9−11]. ...
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Background context The effect of the posterior midline approach to the lumbar spine, relevance of inter- and supraspinous ligament (ISL&SSL) sparing, and potential of different wound closure techniques are largely unknown despite their common use. Purpose The aim of this study was to quantify the effect of the posterior approach, ISL&SSL resection, and different suture techniques. Study Design Biomechanical cadaveric study. Methods Five fresh frozen human torsi were stabilized at the pelvis in the erect position. The torsi were passively loaded into the forward bending position and the sagittal angulation of the sacrum, L4 and T12 were measured after a level-wise posterior surgical approach from L5/S1 to T12/L1 and after a level-wise ISL&SSL dissection of the same sequence. The measurements were repeated after the surgical closure of the thoracolumbar fascia with and without suturing the fascia to the spinous processes. Results Passive spinal flexion was increased by 0.8 ± 0.3° with every spinal level accessed by the posterior approach. With each additional ISL&SSL resection, a total increase of 1.6 ± 0.4° was recorded. Suturing of the thoracolumbar fascia reduced this loss of resistance against lumbar flexion by 70%. If the ISL&SSL were resected, fascial closure reduced the lumbar flexion by 40% only. In both settings, suturing the fascia to the spinous processes did not result in a significantly different result (p = .523 and p = .730 respectively). Conclusion Each level accessed by a posterior midline approach is directly related to a loss of resistance against passive spinal flexion. Additional resection of ISL&SSL multiplies it by a factor of two. Clinical Significance The surgical closure of the thoracolumbar fascia can reduce this effect only partially and suturing the fascia back to the spinal processes does not result in improved passive stability.
... Following a slow muscle contraction there is an increase in the tension of the muscle (content) which causes a direct increase in the tension of the fascia (container). This happens thanks to the muscular insertions on the fascia (Fan et al., 2018;A. Stecco, Gilliar, Hill, Brad, & Stecco, 2013;C Stecco et al., 2007). ...
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Despite more than hundred years of research since Sir Sherrington’s studies on reflexes, his questions are still somehow unanswered. On what anatomical stage do the play of spinal reflex interaction take place? What are the physiological properties of this anatomical substrate? In this paper, we address these questions in light of the most advanced theory of motor control and the anatomical discoveries on the fascia that are changing how we think about control of action and perception. There are two sides of the problem: the neurological (reflex) connections that are at the base of movement, and the anatomical substrate that regulates and coordinates the movement. We recently advanced a hypothesis on how these two elements are connected and how they interplay. Here we further explain the concept of the somatic equilibrium point – SEP – and its central role in movement control and coordination. It is our belief that the concept of SEP explains how the neuro-mechanical control of movement is organized at peripheral level. At this level, intrafusal and extrafusal muscle fibres are combined in myofascial units, organized in anatomical directions. Myofascial units are closed systems whose behaviour can be affected by neural (voluntary) control or changes in external forces. SEPs represent the intrinsic equilibrium of the myofascial units, and are connected through the continuum of the fascia so that mechanical transfer of tension from segment to segment pre-adjust muscle fibers length and hence their excitation level. This is how coordination between segments is achieved. Finally, we suggest SEPs create the neurological representation of the referent configuration for action, and configurations are linked to the architecture of the fascial system.
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(1) Background: Decreased trunk stability is accompanied by delay in motor development in children with central hypotonia. We investigated the effect of Vojta therapy on trunk control in the sitting position in children with central hypotonia. (2) Methods: In 20 children with central hypotonia, Vojta therapy was applied to the experimental group (n = 10) and general physical therapy to the control group (n = 10). The intervention was applied for 30 min per session, three times a week, for a total of six weeks. We assessed abdominal muscle thickness, trunk control (segmental assessment of trunk control), trunk angle and trunk sway in a sitting position, and gross motor function measure-88. (3) Results: In the experimental group, the thicknesses of internal oblique and transversus abdominis were significantly increased (p < 0.05). The segmental assessment of trunk control score was significantly increased (p < 0.05), and the trunk sway significantly decreased (p < 0.05). Gross motor function measure-88 was significantly increased (p < 0.05). (4) Conclusions: Vojta therapy can be suggested as an effective intervention method for improving trunk control and gross motor function in children with central hypotonia.
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Objective: To investigate the effectiveness of groin flap with external oblique aponeurosis in repair of tendon and skin defects of dorsal foot. Methods: Between October 2016 and January 2020, 12 patients with compound tissue defects of the dorsal foot caused by trauma were treated. There were 9 males and 3 females, with a median age of 42 years (range, 32-65 years). The size of the skin defects ranged from 8 cm×5 cm to 12 cm×8 cm. All wounds were accompanied by extensor tendon injury, including 6 cases of extensor hallucis longus tendon defect, 5 cases of extensor digitalis longus tendon defect, and 3 cases of extensor digitalis longus tendon and extensor digitorum brevis defects. The interval between injury and admission was 1-6 hours (mean, 3 hours). After admission, the wounds were thoroughly debrided, and the groin flap with external oblique aponeurosis was used to repair the skin and tendon defects in the second stage. The size of skin flap ranged from 10 cm×6 cm to 13 cm×9 cm, and the size of the external oblique aponeurosis ranged from 5.5 cm×3.0 cm to 8.0 cm×5.0 cm. The wounds at donor sties were sutured directly. Results: All flaps survived completely without significant complications. All incisions of the recipient and donor sites healed by first intention. All patients were followed up 16-24 months (mean, 18 months). The flaps were satisfactory in appearance and soft in texture. At last follow-up, 9 cases were excellent and 3 cases were good according to the American Orthopaedic Foot and Ankle Society (AOFAS) metatarsophalangeal-interphalangeal joint scale criteria. The toe function was satisfactory. The line scar was left without hernia or other morbidity on the donor site. Conclusion: The groin flap with the external oblique aponeurosis can repair the tendon and skin defects of the dorsal foot, with concealed donor site, easy dissection and adjustable thinness, as well as the enough tough aponeurosis.
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Background: Chronic low back pain (CLBP) is one of the most common musculoskeletal disorders. Physical activity (PA) is often recommended as part of the management of CLBP, but to date, no one particular exercise has been shown to be superior. Vibrating exercise equipment (VEE) is widely available and used despite little scientific evidence to support its effectiveness in the prevention and treatment of musculoskeletal problems. The aim of this study was to evaluate the efficiency of using VEE compared with sham-VEE in women with CLBP. Methods: A randomized (1:1 randomization scheme) single-blinded sham-controlled intervention study was conducted. Through simple randomization, 92 women aged 49–80 years were assigned to one of two groups: VEE (the experimental group) and sham-VEE (the control group). The VEE and sham-VEE intervention consisted of aerobic exercises with specific handheld equipment. Both groups performed physical activity twice weekly for 10 weeks. The erector spinae muscles’ bioelectrical activity (using an eight-channel electromyograph MyoSystem 1400L), lumbar range of motion (Schober’s test) and pain intensity (visual analog scale) were measured in all participants at baseline and after 10 weeks. Results: There was a significant decrease in the bioelectrical activity of the erector spinae muscles during flexion movement (left: Me = 18.2 before; Me = 14.1 after; p = 0.045; right: Me = 15.4 before; Me = 12.6 after; p = 0.010), rest at maximum flexion (left: Me = 18.1 before; Me = 12.5 after; p = 0.038), extension movement (right: Me = 21.8 before; Me = 20.2 after; p = 0.031) and rest in a prone position (right: Me = 3.5 before; Me = 3.2 after; 0.049); an increase in lumbar range of motion (Me = 17.0 before; Me = 18.0 after; p = 0.0017) and a decrease in pain intensity (Me = 4.0 before; Me = 1.0 after; p = 0.001) following a program of PA in the VEE group. Conclusions: No significant changes were found in intergroup comparisons. The beneficial changes regarding decreased subjective pain sensation in the VEE and sham-VEE groups may be due to participation in systematic physical activity. However, PA with vibrating exercise equipment could be a prospective strategy for increasing lumbar range of motion and for decreasing pain and erector spinae muscle activity in people with CLBP.
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There is a high prevalence of myofascial pain in people with hypermobile Ehlers‐Danlos Syndrome (hEDS). The fascial origin of pain may correspond to changes in the extracellular matrix. The objective of this study was to investigate structural changes in fascia in hEDS. A series of 65 patients were examined prospectively—26 with hEDS, and 39 subjects with chronic neck, knee, or back pain without hEDS. The deep fascia of the sternocleidomastoid, iliotibial tract, and iliac fascia were examined with B‐mode ultrasound and strain elastography, and the thicknesses were measured. Stiffness (strain index) was measured semi‐quantitatively using elastography comparing fascia to muscle. Differences between groups were compared using one‐way analysis of variance. hEDS subjects had a higher mean thickness in the deep fascia of the sternocleidomastoid compared with non‐hEDS subjects. There was no significant difference in thickness of the iliac fascia and iliotibial tract between groups. Non‐hEDS subjects with pain had a higher strain index (more softening of the fascia with relative stiffening of the muscle) compared with hEDS subjects and non‐hEDS subjects without back or knee pain. In myofascial pain, softening of the fascia may occur from increase in extracellular matrix content and relative increase in stiffness of the muscle; this change is not as pronounced in hEDS.
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Introduction: Hyaluronan occurs between deep fascia and muscle, facilitating gliding between these two structures, and also within the loose connective tissue of the fascia, guaranteeing the smooth sliding of adjacent fibrous fascial layers. It also promotes the functions of the deep fascia. In this study a new class of cells in fasciae is identified, which we have termed fasciacytes, devoted to producing the hyaluronan‐rich extracellular matrix. Materials and methods: Synthesis of the hyaluronan‐rich matrix by these new cells was demonstrated by Alcian Blue staining, anti‐HABP (hyaluronic acid binding protein) immunohistochemistry, and transmission electron microscopy. Strong expression of HAS2 (hyaluronan synthase 2) mRNA by these cells was detected and quantified using real time RT‐PCR. Results: This new cell type has some features similar to fibroblasts: they are positive for the fibroblast marker vimentin and negative for CD68, a marker for the monocyte‐macrophage lineage. However, they have morphological features distinct from classical fibroblasts and they express the marker for chondroid metaplasia, S‐100A4. Conclusions: The authors suggest that these cells represent a new cell type devoted to the production of hyaluronan. Since hyaluronan is essential for fascial gliding, regulation of these cells could affect the functions of fasciae so they could be implicated in myofascial pain. This article is protected by copyright. All rights reserved.
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Background: The rise of evidence-based anatomy (EBA) has emphasized the need for original anatomical studies with high clarity, transparency, and comprehensiveness in reporting. Currently, inconsistencies in the quality and reporting of such studies have placed limits on accurate reliability and impact assessment. Our aim was to develop a checklist of reporting items that should be addressed by authors of original anatomical studies. Materials and Methods: The study steering committee formulated a preliminary conceptual design and began to generate items on the basis of a literature review and expert opinion. This led to the development of a preliminary checklist. The validity of this checklist was assessed by a Delphi procedure, and feedback from the Delphi panelists, who were experts in the area of anatomical research, was used to improve it. Results: The Delphi procedure involved 12 experts in anatomical research. It comprised two rounds, after which unanimous consensus was reached regarding the items to be included in the checklist. The steering committee agreed to name the checklist AQUA. The preliminary AQUA Checklist consisted of 26 items divided into eight sections. Following round 1, some of the items underwent major revision and three new ones were introduced. The checklist was revised only for minor language inaccuracies after round 2. The final version of the AQUA Checklist consisted of the initial eight sections with a total of 29 items. Conclusion: The steering committee hopes the AQUA Checklist will improve the quality and reporting of anatomical studies.
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A 3D model of lumbar structures of anesthetic interest was reconstructed from human magnetic resonance (MR) images and embedded in a Portable Document Format (PDF) file, which can be opened by freely available software and used offline. The MR images were analyzed using a specific 3D software platform for biomedical data. Models generated from manually delimited volumes of interest and selected MR images were exported to Virtual Reality Modeling Language format and were presented in a PDF document containing JavaScript-based functions. The 3D file and the corresponding instructions and license files can be downloaded freely at http://diposit.ub.edu/dspace/handle/2445/44844?locale=en. The 3D PDF interactive file includes reconstructions of the L3–L5 vertebrae, intervertebral disks, ligaments, epidural and foraminal fat, dural sac and nerve root cuffs, sensory and motor nerve roots of the cauda equina, and anesthetic approaches (epidural medial, spinal paramedial, and selective nerve root paths); it also includes a predefined sequential educational presentation. Zoom, 360° rotation, selective visualization, and transparency graduation of each structure and clipping functions are available. Familiarization requires no specialized informatics knowledge. The ease with which the document can be used could make it valuable for anatomical and anesthetic teaching and demonstration of patient information. Clin. Anat., 2014. © 2014 Wiley Periodicals, Inc.
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The thoracolumbar fascia (TLF) consists of aponeurotic and fascial layers that interweave the paraspinal and abdominal muscles into a complex matrix stabilizing the lumbosacral spine. To better understand low back pain, it is essential to appreciate how these muscles cooperate to influence lumbopelvic stability. This study tested the following hypotheses: (i) pressure within the TLF's paraspinal muscular compartment (PMC) alters load transfer between the TLF's posterior and middle layers (PLF and MLF); and (ii) with increased tension of the common tendon of the transversus abdominis (CTrA) and internal oblique muscles and incremental PMC pressure, fascial tension is primarily transferred to the PLF. In cadaveric axial sections, paraspinal muscles were replaced with inflatable tubes to simulate paraspinal muscle contraction. At each inflation increment, tension was created in the CTrA to simulate contraction of the deep abdominal muscles. Fluoroscopic images and load cells captured changes in the size, shape and tension of the PMC due to inflation, with and without tension to the CTrA. In the absence of PMC pressure, increasing tension on the CTrA resulted in anterior and lateral movement of the PMC. PMC inflation in the absence of tension to the CTrA resulted in a small increase in the PMC perimeter and a larger posterior displacement. Combining PMC inflation and tension to the CTrA resulted in an incremental increase in PLF tension without significantly altering tension in the MLF. Paraspinal muscle contraction leads to posterior displacement of the PLF. When expansion is combined with abdominal muscle contraction, the CTrA and internal oblique transfers tension almost exclusively to the PLF, thereby girdling the paraspinal muscles. The lateral border of the PMC is restrained from displacement to maintain integrity. Posterior movement of the PMC represents an increase of the PLF extension moment arm. Dysfunctional paraspinal muscles would reduce the posterior displacement of the PLF and increase the compliance of the lateral border. The resulting change in PMC geometry could diminish any effects of increased tension of the CTrA. This study reveals a co-dependent mechanism involving balanced tension between deep abdominal and lumbar spinal muscles, which are linked through the aponeurotic components of the TLF. This implies the existence of a point of equal tension between the paraspinal muscles and the transversus abdominis and internal oblique muscles, acting through the CTrA.
Article
Unambiguous reporting of a study's compliance with ethical guidelines in anatomical research is imperative. As such, clear, universal, and uniform reporting guidelines for study ethics are essential. In 2016, the International Evidence-Based Anatomy Working group in collaboration with international partners established reporting guidelines for anatomical studies, the Anatomical Quality Assurance (AQUA) Checklist. In this elaboration of the AQUA Checklist, consensus guidelines for reporting study ethics in anatomical studies are provided with in the framework of the AQUA Checklist. The new guidelines are aimed to be applicable to research across the spectrum of the anatomical sciences, including studies on both living and deceased donors. The authors hope the established guidelines will improve ethical compliance and reporting in anatomical research. This article is protected by copyright. All rights reserved.
Article
Introduction: Back pain is associated with increased lumbar paraspinal muscle (LPM) stiffness identified by manual palpation and strain elastography. Recently, magnetic resonance elastography (MRE) has allowed the stiffness of muscle to be characterized noninvasively in vivo, providing quantitative 3D stiffness maps (elastograms). The aim of this study was to characterize the stiffness (shear modulus, SM) of the LPM (multifidus and erector spinae) using MRE. Materials and methods: MRE of the lumbar region was performed on seven adults in supine position. MRE was acquired in three muscular states: relaxed with outstretched legs, stretched with passive pelvis flexion, and contracted with outstretched legs and tightened trunk muscles. The mean SM was measured within a region of interest manually defined in the multifidus, erector spinae and the entire paraspinal compartment. The intermuscular difference and the effects of stretching and contraction were assessed by ANOVA and t-tests. Results: At rest, the mean SM of the paraspinal compartment was 1.6±0.2kPa. It increased significantly with stretching to 1.65±0.3kPa, and with contraction to 2.0±0.7kPa. Irrespective of muscular state, the erector spinae was significantly stiffer than the multifidus. The multifidus underwent proportionally higher stiffness changes from rest to contraction and stretching. Conclusions: MRE can be used to measure the stiffness of the LPM in different muscular states. We hypothesize that, irrespective of posture, the erector spinae behaves as semi-rigid beam and ensures permanent stiffness of the spine. The multifidus behaves as an adaptable muscle that provides segmental flexibility to the spine and tunes the spine stiffness. This article is protected by copyright. All rights reserved.
Article
Although the intrinsic muscles of the back are defined by their embryological origin and innervation pattern, no detailed study on their development is available. Human embryos (5-10 weeks development) were studied, using Amira3D® reconstruction and Cinema4D® remodelling software for visualization. At Carnegie Stage (CS)15, the epaxial portions of the myotomes became identifiable laterally to the developing vertebrae. At CS16, these portions fused starting cranially to form a longitudinal muscle column, which became innervated by the dorsal branches of the spinal nerves. At CS17, the longitudinal muscle mass segregated into medial and lateral columns (completed at CS18). At CS18, the medial column segregated again into intermediate and medial columns (completed at CS20). The lateral and intermediate columns did not separate in the lower lumbar and sacral regions. Between CS20 and CS23, the cervical portions of the three columns segregated again from lateral to medial resulting ventrolaterally in rod-like continuations of the caudal portions of the columns and dorsomedially in spade-like portions. The observed topography identifies the iliocostalis and splenius as belonging to the lateral column, the longissimus to the intermediate column, and the (semi-)spinalis to the medial column. The medial (multifidus) group acquired its transversospinal course during closure of the vertebral arches in the early foetal period. Hence, the anatomical ontology of the epaxial muscles is determined by craniocaudal and lateromedial gradients in development. Three longitudinal muscle columns, commonly referred to as the erector spinae, form the basic architectural design of the intrinsic muscles of the back. This article is protected by copyright. All rights reserved.
Article
Introduction: Chronic low back pain (CLBP) and fear of movement (kinesiophobia) are associated with an overactivation of paravertebral muscles during forward bending. This impairs spine motor control and contributes to pain perpetuation. However, the abdominal muscles activation is engaged too in spine stabilization but its modulation with kinesiophobia remains unknown. Our study tested whether CLBP and kinesiophobia affected the activation pattern of abdominal muscles during trunk flexion/extension. Methods: Surface electromyographical recordings of the internal oblique/transversus abdominis (IO/TrA) and external oblique (EO) muscles were analyzed in 12 people with CLBP and 13 pain-free subjects during low-velocity forward bending back and forth from erected posture. Tampa Scale of Kinesiophobia was also administrated. Results: IO/TrA activation, but not EO, was modulated across the phases of movement in both groups, i.e. maximal at onset of flexion and end of extension, and minimal at full flexion. In CLBP group only, IO/TrA activation was increased near to full trunk flexion and in correlation with kinesiophobia. Conclusions: The phase-dependence of IO/TrA activation during trunk flexion/extension in standing may have a role in spine motor control. The influence of kinesiophobia in CLBP should be further investigated as an important target in CLBP management.
Article
To provide evidence for the existence of six myofascial meridians proposed by Myers (1997) based on anatomical dissection studies. Relevant articles published between 1900 and December 2014 were searched in MEDLINE (Pubmed), ScienceDirect and Google Scholar. Peer-reviewed human anatomical dissection studies reporting morphological continuity between the muscular constituents of the examined meridians were included. If no study demonstrating a structural connection between two muscles was found, papers on general anatomy of the corresponding body region were targeted. A continuity between two muscles was only documented if two independent investigators agreed that it was reported clearly. Also, two independent investigators rated methodological quality of included studies by means of a validated assessment tool (QUACS). The literature search identified 6589 articles. Of these, 62 papers met the inclusion criteria. The studies reviewed suggest strong evidence for the existence of three myofascial meridians: the superficial back line (all three transitions verified, based on 14 studies), the back functional line (all three transitions verified, 8 studies) and the front functional line (both transitions verified, 6 studies). Moderate to strong evidence is available for parts of the spiral line (five of nine verified transitions, 21 studies) and the lateral line (two of five verified transitions, 10 studies). No evidence exists for the superficial front line (no verified transition, 7 studies). The present systematic review suggests that most skeletal muscles of the human body are directly linked by connective tissue. Examining the functional relevance of these myofascial chains is the most urgent task of future research. Strain transmission along meridians would both open a new frontier for the understanding of referred pain and provide a rationale for the development of more holistic treatment approaches. Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.