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ULTRASTRUCTURAL REVELATION of the NATURE of PENNATION in the
ABDOMINAL MUSCLES of CHILDREN with SPASTIC TYPE CEREBRAL PALSY
(STCP): IMPLICATIONS for FORCE GENERATION
Article  in  Journal of Musculoskeletal Research · December 2018
DOI: 10.1142/S0218957718500082
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Journal of Musculoskeletal Research, Vol. 21, No. 2 (2018) 1850008 (12 pages)
© World Scientific Publishing Company
DOI: 10.1142/S0218957718500082
ULTRASTRUCTURAL REVELATION OF THE NATURE OF
PENNATION IN THE ABDOMINAL MUSCLES OF CHILDREN
WITH SPASTIC TYPE CEREBRAL PALSY (STCP):
IMPLICATIONS FOR FORCE GENERATION
Saviour Adjenti
,¶, Graham Louw†, Jennifer Jelsma‡
and Marianne Unger§

Department of Anatomy, School of Biomedical & Allied Health Sciences
College of Health Sciences, University of Ghana
Korle-bu Campus, P. O. Box, KB 143, Korle-bu, Ghana
†Department of Human Biology, Faculty of Health Sciences
University of Cape Town, South Africa
‡Division of Physiotherapy, Faculty of Health Sciences
University of Cape Town, South Africa
§Department of Physiotherapy, Faculty of Health Sciences
Stellenbosch University, South Africa
¶saviour.adjenti@yahoo.com; ksdadjenti@ug.edu.gh
Received 26 July 2018
Accepted 13 November 2018
Published 10 December 2018
ABSTRACT
Purpose: To investigate whether the pennation angle (PA) in the abdominal muscles of individuals
with spastic type cerebral palsy (STCP) has undergone any change when compared with those of
typically developing (TD) individuals. To determine whether PA of abdominal muscles in individuals
with STCP impacts differently on the force generating capacity, from those of TD peers. Materials &
methods: Ultrasound images of the four abdominal muscles namely; rectus abdominis (RA), internal
oblique (IO), external oblique (EO) and transversus abdominis (TrA), were obtained during the resting
and active stages. ImageJ software package (version 2012) was used to measure the PA of the
Correspondence to: Saviour Adjenti, Department of Anatomy, School of Biomedical & Allied Health Sciences, College of
Health Sciences, University of Ghana, Korle-bu Campus, P. O. Box, KB 143, Korle-bu, Ghana.
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S. Adjenti et al.
sonographic images. Sixty-three individuals with STCP and eighty-two typically developing (TD)
individuals took part in the study. The participants were between the ages of 7 and 16 years.
Results: The PA for three out of the four abdominal muscles was less than 3 while the RA muscle
in both groups showed a pennation angle of zero degrees during the resting and active stages.
Conclusion: Excluding the rectus abdominis muscle, PA appeared to be altered in individuals with
STCP when compared to their TD counterparts. The characterization of PA in abdominal muscles in
both groups is, however, unclear. The PA as a muscle parameter may not be an important variable for
differentiating the force generating capacity between individuals with STCP and their TD peers.
Further investigation is required on MAP and the overall implication of each component on abdominal
muscle function, especially in the maintenance of balance and posture.
Keywords: Pennation angle; Spastic type cerebral palsy; Abdominal muscles; Ultrasonography;
Muscle architectural parameter.
INTRODUCTION the motivation for this collaborative empirical
Muscle architecture primarily refers to the ar- assessment of one of the components of MAP, the
rangement of muscle fibers in a muscle tissue. pennation angle.
From the morphological and quantitative per- The correlation between MT and function/
spectives, the functional components that consti- strength has been widely documented in the limb
tute the parenchyma of a skeletal muscle are muscles of healthy individuals and in those with
1
collectively referred to as the muscle architectural skeletal muscle disorders. Similarly, FL is also
parameter (MAP).24 These include: the physio- variously implicated in muscle function, espe-
,
logical cross-sectional area (PCSA) which is also cially in the production of range of motion.1 5 The
estimated to represent the muscle thickness (MT), exact role of PA with respect to muscle function,
at the greatest perpendicular distance of the especially in thin and flat muscles such as found
fibers, pennation angle (PA) and muscle fiber in the anterior abdominal wall is unclear. A study
length (FL).21,24 Each of these components of on the thigh muscles of healthy adults, however,
MAP has been linked to muscle function and the has shown that PA allows for more contractile
overall strength of a muscle.22,23 However, the materials per unit area than for non-pennated
most frequently inferred and implicated of this muscles.28 This evidence notwithstanding, little is
MAP regarding muscle function is PCSA or known regarding PA in trunk muscles of either
MT. There is evidence that muscle fibers in gen- healthy individuals or those with STCP.
eral, produce their greatest force at lengths Generally, considering the arrangement of
slightly greater than their resting length (80– muscle fibers in a muscle tissue, skeletal muscles
120%).28 Such reports are considered vital espe- may be grouped into two basic types: pennate
cially in the field of rehabilitation, for skeletal and non-pennate muscles.22 A non-pennate
muscles which are known to possess remarkable muscle is described as one in which the muscle
plasticity.23 The ability of a skeletal muscle to fibers run parallel to the line of pull of the muscle,
quickly gain or lose contractile material according such that the fiber is in the direction of the overall
to changes in loading regimens (plasticity) cou- muscle vector.2,22 On the other hand, a muscle
pled with the high capacitance for permanent with pennate arrangements is regarded as having
disabilities in cases of individuals with spastic muscle fibers which run diagonally with respect
type cerebral palsy (STCP)2 partly accounts for to the line of pull of the muscle.1,22 The angle
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Pennation Angle and the Anterior Abdominal Wall Muscles
formed between the line of pull and the align- properties of skeletal muscles in individuals with
ment of the muscle fibers is referred to as the STCP.9 From the anatomical and physiological
PA.1,5,22 It has been reported that the advantage point of view, these management options are
of the pennate arrangement is the high force aimed at enhancing those properties of a muscle
output due to the increased amount of contractile needed for efficient generation of force.9,14
material per unit volume.5,28 Available evidence No evidence however, exists on the extent of
shows that although more force is produced by a alterations, if any that a neuro-pathophysiologi-
pennate muscle, not all of this force is transmitted cal condition such as STCP is capable of having
to the tendon.13,16,28 Similarly, the amount of on the MAP of abdominal muscles at the ultra-
force transmitted to the tendon for distribution, is structural level. Therefore, relating the success or
shown to decrease with an increasing PA.3 The failure of any management option to a specific
exact function of PA therefore, is unclear with component of MAP is anecdotal. Thus, in theory,
respect to the overall function of a muscle. To a functional relationship may exist among the
quantify PA in a muscle or muscle group, espe- three components of MAP, yet the overall corre-
cially in individuals with STCP may increase our lation of this relationship on the gross function of
understanding of the various components of a muscle is unclear. In practice it is only MT and
MAP and in general muscle function. or the overall physiological cross-sectional area
Cerebral palsy (CP) is a condition that negatively (PCSA) that has often been related to muscle
impacts on motor function and postural muscle strength and activity.5,28 Therefore, by inference
tone.25 It is acquired at an early age, with the STCP the muscles of the anterior abdominal wall by
subtype being the most common.26 Children with their nature of being relatively thin have been
STCP show mal-rotation of the trunk with an categorized into a non-functional state. Further-
associated poor recruitment of the abdominal more, such a theoretical consideration fails to
muscles.15,25 The general assumption among recognize the various types of muscles (pennate,
researchers in thefield ofmusculoskeletal disorders non-pennate, thick and thin) that exist in the
is that, the ability to maintain upright posture may body.9,14,15 The gross appearance of the abdomi-
be lost in children with STCP.3 Therefore, a lack of nal muscles, although may be regarded as thin
torque formovement andoptimumposture is often compared to the limb musculature,9 no ultra-
attributable to weak abdominal muscles, especially structural study is available on the MAP of
in individuals with STCP.27 these muscles, especially in individuals with
In relating theory to practice, a reduction in the STCP. Consequently, the individual action of each
mechanical properties, (extensibility and elastici- of the abdominal muscles, with regard to trunk
ty), of the gastrocnemius muscles of individual stability is a subject of debate and an important
with STCP was reported.21,26 Such findings have area of research in the field of biokinetics.21
practical implications for the management and With regard to biomechanics and human
rehabilitation options available for individuals movement, adequate knowledge on the MAP, is
with STCP. There is therefore, the need for fur- important in the setting up of neuro-musculo-
ther investigation of skeletal muscles at the ul- skeletal models for the investigation of motion.21
trastructural level. Any rehabilitation regimen, According to Hodges and co-workers,14 as a re-
either by means of physical therapy or chemo- sult of the bipedal nature of human beings, any
therapy, is meant to directly or indirectly attempt to stabilize the spine (vertebral column)
improve on the contractile, extensible and elastic must be balanced by an optimal control from all
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S. Adjenti et al.
the components of the musculoskeletal system. 490/2011). A SIEMENS® ACUSONIC X150 ultra-
Therefore, in order to provide a better theoretical sound imaging machine (Munich, Germany) was
basis for the planning of any rehabilitation in- used to capture the thickness of the four ab-
tervention involving the optimal functioning of dominal muscles, Rectus Abdominis (RA), Inter-
the abdominal muscles with regards to indivi- nal Oblique (IO), External Oblique (EO) and
duals with STCP, this study aims to: Transversus Abdominis (TrA), both in the resting
. verify whether abdominal muscles in children and contracted stages.
with STCP undergo any pathophysiological
transformation at the ultrastructural level, and
. determine whether these ultrastructural chan- Participants
ges could impact any difference on one of the Sixty-three children (43.4%) with STCP and 82
components of MAP, (PA) in terms of gross (56.6%) typically developing (TD) individuals
muscle function in comparison to those of TD took part in the study. Participants from the
individuals. STCP group were recruited from children at-
The ultimate aim of this study is to relate theo- tending special schools in Cape Town (conve-
retical knowledge on musculoskeletal anatomy to nient sampling method used). Children included
clinical practice with respect to rehabilitation and in the TD group were learners from mainstream
the maintenance of pelvic stability in individuals schools in the locality of the special-need schools.
with STCP. The mean age of all the participants was eleven-
An in vivo assessment, especially of the changes years and three-months (Standard deviation
in muscle structure due to STCP has been the (SD) ¼ 3.0, range 7–16 years). Of the total sample,
preferred technique with this type of ultrastruc- 53.8% were male and 46.2% were female.
tural investigation.11,12 In adherence to the guide-
lines for in vivo investigation on disorders of the
human musculoskeletal system,14,25 our study in- Exclusion Criteria
volved the use of ultrasonography to measure one Typically developing (TD group): A child who has
of the components of MAP, MT of the abdominal undergone any surgical operation involving the
muscles. The other two parameters namely PA anterior abdominal wall in the last six months
and FL were estimated with the aid of computer prior to the commencement of the study.
software packages (ImageJ). Ultrasonography was The spastic type cerebral palsy (STCP) group: The
the preferred choice of this in vivo assessment be- Gross Motor Function Classification Scale
cause it is less expensive than other similar tech- (GMFCS)26 was utilized by a paediatric physio-
niques, fast, reliable as well as devoid of any harm therapist to determine the level of disability of the
to both the participants and investigators. participants. Children at level V of the GMFCS
scale (non-ambulatory) form part of the exclusion
criteria because they were unable to perform the
METHODS test maneuver. The second exclusion criterion is
A descriptive, analytical and cross-sectional medical treatments that would have impacted
study design was used. Ethical approval was on muscle function. For example, the use of bot-
obtained from the Human Research Ethics Com- ulinum toxin injection, casting, and surgical in-
mittee of theUniversity of Cape Town (HRECREF: tervention such as dorsal rhizotomy and baclofen
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Pennation Angle and the Anterior Abdominal Wall Muscles
pump placement in less than six months prior to along the mid-sagittal axis of each of the rest of
the study. the three anterolateral abdominal muscle (EO, IO
and TrA) in a somewhat oblique fashion. The
pressure of the transducer was kept to a mini-
Procedure mum by using a generous amount of the contact
A SIEMENS® ACUSONIC X150 ultrasound im- gel in order to obtain optimum values for muscle
aging machine (Munich, Germany) was used to thickness. All sites along a muscle from which
capture the thickness of the four abdominal images were taken at rest were then repeated
muscles, rectus abdominis (RA), internal oblique during each child’s head and shoulder/leg lift
(IO), external oblique (EO) and transverse abdo- movement (active stage). Images were stored on
minis (TrA), in both the resting and active stages. a personal computer and then analyzed with
To test the muscles in the resting stage, children ImageJ Microsoft version 1.46, 2011 edition
were asked to lie supine on the plinth with no (Richmond, Virginia, USA).
activity. For the active stage, children were asked Muscle thickness (MT) was determined using an
to lie supine on the plinth and then asked to electronic calliper on a frozen image. The length
perform the following activities: (i) To fully ab- of a perpendicular line drawn between the echoes
duct the shoulder joint, (ii) to tuck in the chin and parallel to the fascicles from the deep up to the
lift head and neck slightly towards the chest; and superficial aponeurosis (inter-fascial planes) was
(iii) to flex the hip as far as possible. The perfor- measured (Fig. 1). Since thickness varies along
mance of these activities was aimed at initiating a the length of a muscle, measurements were taken
simultaneous contraction of the abdominal mus- at three different points for a particular muscle
cles, which was then measured. The average of according to the clarity of the image and the av-
these three maneuvers was recorded as the active erage was recorded for that individual.
stage thickness. The side of active upper or lower Pennation angle (PA): The angle between the
limb motion and of abdominal muscle thickness superficial and deep aponeuroses echoes were
measurement was the affected side in hemiplegic
children, the right side in diplegic, quadriplegic
and TD children. The principal investigator han-
dled the transducer head (ultra-sound probe)
while one of the research assistants, a neurode-
velopmental therapist, issued the instructions to
the participants.
Using the umbilicus as a landmark the ultra-
sound probe was placed two to three centimeters
from the midline and then was panned around in
a semi-circular fashion until the bulk of the image
from the deepest lying abdominal muscle, TrA,
was observed on the image screen. This position
was marked on the skin with a marker pen in
order to ensure that the probe was kept in this
Fig. 1 Sonogram of the three anterolateral muscles. SF ¼
position for subsequent measurements. The skin and superficial fascia, AC ¼ abnormal cavity. The RA is
scanning head of the probe was then oriented out of view.
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relatively large sample size, normality was as-
sumed and parametric tests were used for all
analyses. Independent t-test was used to statisti-
cally compare the means of the two groups in
both resting and active stages. A two-way
ANOVA with repeated measures was used to
determine if there was a significant group-stage
Fig. 2 Lines MN and PQ represent superficial and deep interaction that affected pennation angle. The
aponeuroses, respectively, MP or NQ represents muscle
thickness (T), lines x and y represent orientations of muscle changes in PA from rest to the active stage in each
fibers while a and b represent pennation angles for muscle group were compared using paired t-test. A 95%
fibers x and y, respectively. Angles a and b are generated by confidence interval was used to determine the
the software based on inputs from the scores of MP and precision of the estimates of the differences in PA
MN/PQ.
between the resting and active stages for both
defined as the pennation angle of each muscle groups. Association between PA and age of all
(Figs. 1 and 2). Measurements of pennation angle participants was assessed using the Pearson’s
and fascicle length and thickness were derived correlation coefficient. The level of significance
from computer stored images using ImageJ pro- for all statistical tests was set at 0.05.
cessor in Microsoft version 1.46. The major geo-
metrical assumptions made in using such
planimetric models of representing these sono- RESULTS
graphs of the muscles (thickness) as a two- The mean PA for the two groups during the
dimensional figure (Fig. 2), especially in the resting and active stages using a paired t-test are
determination of pennation angle were that: shown in Table 1. Results indicate that apart from
the TrA, (p ¼ 0:058) statistically significant dif-
. aponeuroses behaved as rigid bodies and run ferences of the PA of the oblique muscles exist
parallel to each other12 and between the resting and active stages for indivi-
. the fascicles ran straight between aponeuroses.12 duals with STCP. Whereas for the TD group, the
The validity of the ultrasound equipment has been PA for the oblique and transverse abdominal
documented in the literature and found to be ap- muscles show statistically significant (p < 0:001)
propriate for use in research and diagnostic ana- differences between the resting and active stages
lyzes.6–8 For the purpose of this study inter- and using a paired t-test.
intra-tester analyses were carried out between the Figures 3 and 4 show the relative levels of PA
principal investigator and the research assistants among the EO, IO and TrA muscles during the
on the same day and on different days on a cohort resting stage between the two groups. The Pear-
of the participants. The test-retest results all son’s correlation graphs of the resting stage PA of
showed good to excellent correlations (ICC ratios the oblique and transverse abdominal muscles
> 0:70). Refer to Tables A.1–A.4 of Appendix A. show statistically significant positive association
(p < 0:001) between the resting stage PA and age
for both the STCP and TD groups.
Statistical Analysis Table 2 shows the result of the differences in
STATISTICA software package, version 11 (2012) the levels of PA between the two groups during
was used to analyze the data. Due to the the resting stage using unpaired t-test. Excluding
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Pennation Angle and the Anterior Abdominal Wall Muscles
Table 1 Comparison of Means of Muscle Pennation Angle at Rest (R) Between STCP and TD Groups Using Unpaired
t-test.
Muscle Pennation Angle/Degrees () Mean Difference p-Value 95% CI of Difference/Degrees ()
STCP (N= 63) SD TD (N= 82) SD
EO (t ¼ 6:70) 1.88 0.26 1.62 0.20 0.26 <0.001 0.18–0.33
IO (t ¼ 4:91) 2.10 0.22 1.93 0.20 0.17 <0.001 0.10–0.24
TrA (t ¼ 8:83) 1.58 0.24 1.17 0.30 0.41 <0.001 0.31–0.50
RA 0.00 0.00 0.00 0.00 0.00
Note: All differences were significant at a p < 0:001 level.
Fig. 3 Correlations between resting stage pennation angles
and age in STCP group. Fig. 4 Correlations between resting stage pennation angles
and age in TD group.
the PA of the rectus abdominis (RA) which could DISCUSSION
not be used in the analysis, (PA ¼ 0:00 for RA in In the light of some of these results, it could be
both groups during rest and activity) results inferred that PA may not be a significant indica-
show that statistically significant differences tor of muscle strength in the abdominal muscles.
(p < 0:001) exist between the two groups with This inference is based on the relatively small
regard to PA during the resting stage. degrees of PA as shown in our findings, coupled
Table 3 compares the means of PA during the with the observation that the RA muscle in both
active stages between the STCP and TD groups groups showed PA of zero make it difficult to
using unpaired t-test. The PA of the IO and TrA relate PA of the abdominal muscles to function or
muscles show statistically significant differences muscle strength. Regardless of the reasons behind
between individuals with STCP and for those these small measurements of PA, the main im-
from the TD group. The PA of the EO muscles plication may be that the prediction used by
however, shows no statistically significant differ- Burtner et al.8 to estimate muscle mass, from
ence between the two groups (p ¼ 0:083; t ¼ 1:75). which the PA is derived, may not be applicable to
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Table 2 Comparison of Means of Muscle Pennation Angle at Active Stage (Ac) Between STCP and TD Groups Using
Unpaired t-test.
Muscle Pennation Angle/mm Mean Difference p-Value 95% CI of Difference/mm
STCP (N= 63) SD TD (N= 82) SD
EO (t ¼ 1:75) 1.83 0.23 1.90 0.25 0.07 0.083 0.01–0.15
IO (t ¼ 2:95) 2.01 0.22 2.11 0.18 0.10 0.004 0.03–0.16
TrA (t ¼ 3:70) 1.53 0.25 1.35 0.32 0.18 < 0.001 0.08–0.27
RA 0.00 0.00 0.00 0.00 0.00
Note: All differences were significant at a p < 0:001 level.
the abdominal muscles. Results from our study strength during adulthood similar to muscle
showed that the RA muscle may comprise par- thickness, in a manner just as reported in the limb
allel muscle fibers with no evidence of any an- musculature.4,19
gulation of its fibers to the force of pull of the In the limb muscles, PA scores were reported
tendon/aponeurosis. This observation appears to to range from a minimum of 18 in the triceps
have weakened any argument for the existence of brachii, to more than 20 in the vasti muscles and
a direct correlation between PA of the abdominal between 20 and 40 in the gastrocnemius.10,18,20
muscles, and the production of muscle force, es- Based on these relatively large PA results in these
pecially in younger individuals, in contrast to studies, it is prudent to relate PA to muscle
that found in lower limb muscles.4,19 Although strength on account of these comparatively large
the present study was restricted to children and PA in the limb musculature. From the current
adolescents there were indications from our study PA of zero was recorded for the RA mus-
results to show that PA of the oblique and cles in both the STCP and TD groups while in the
transverse abdominal muscles correlated posi- oblique muscles as well as the transverse ab-
tively with age of participants. This suggests that dominal muscle PA of less than 3 was observed.
for the PA in the EO, IO and TrA muscles in both It is tempting to hastily infer that the RA muscle
groups could be related to muscle function and in both groups is a weak muscle or incapable of
Table 3 Comparison of Means of Muscle Pennation Angle at Rest (R) and at Active Stage (Ac) in Both STCP
and TD Groups Using Paired t-test.
Muscle Pennation Angle (PA)/Degrees () T-Statistic p-Value 95% CI of Difference/()
Group Resting Active Mean Difference
EO STCP 1.88 1.83 0.05 2.20 0.032 0.004 to 0.10
TD 1.62 1.90 0.28 10.56 <0.001 0.32 to 0.22
IO STCP 2.10 2.01 0.09 5.64 <0.001 0.06 to 0.12
TD 1.93 2.11 0.18 14.99 <0.001 0.20 to 0.15
TrA STCP 1.58 1.53 0.05 1.93 0.058 0.001 to 0.10
TD 1.17 1.35 0.18 9.29 <0.001 0.21 to 0.14
RA STCP 0.00 0.00 0.00 0.00 0.00 0.00
TD 0.00 0.00 0.00 0.00 | |
Note: All differences were significant at p < 0:001.
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Pennation Angle and the Anterior Abdominal Wall Muscles
generating muscle force on account of the results relationship between muscle thickness and PA of
above. However, what the PA results for the RA the abdominal muscles implies that discussions
muscle in both groups (Table 1) tend to highlight on this muscle parameter (PA) is based on the
is probably that this parameter may not influence assumptions that what pertains in the lower limb
abdominal muscle function as the pennation muscles may generally be the case in the ab-
angles remained unchanged during the resting dominal muscles as well.
and active states in both groups. The implication The results in the present study (Table 1)
of such an inference would mean that physio- showed that physiologically there are differences
logically, PA as a muscle parameter essentially between the STCP and TD groups of the changes
may not differentiate abdominal muscle activity in PA from the resting to active stages. This
in individuals with STCP from those of their TD change in PA indicates that a positive change
counterparts. could be seen in the TD group in which the
A study by Shortland and colleagues28 showed functioning of abdominal muscles is regarded as
that the pennate arrangement in the lower limb being intact in contrast to the STCP group which
musculature is directly proportional to muscle showed negative or no changes in the case of the
thickness. Consequently, muscle thickness and RA muscles. Based on the results above, our
pennation angle as MAPs have been linked to study surmized on account of the significant
high force output in these muscles.28 The amount differences between the two groups of the chan-
of force generated by the muscle fibers in the ges in PA from the resting to active states, that
lower limb was therefore, ascribed to the in- PA may be an active parameter in determining
creased amount of contractile material per unit muscle activity. However, given its characteriza-
volume resulting from the large PA.5,28 This is the tion (present, absent, decreasing and increasing
expectation, should the correlation that exists from resting to active stages), in the two groups
between muscle thickness and function, as makes this variable an unimportant variable for
reported in the lower limb muscles18,20 also be differentiating the force generating capacity in
reflected in the abdominal muscles. In addition to individuals with STCP from those of their TD
muscle thickness, Kawakami et al.18 also showed peers. On the observation that this parameter
that there is a positive association between mus- responds differently in the two groups is sug-
cle thickness and PA across individuals. Reports gestive of the fact that PA may have undergone
such as these formed the basis for the generali- some degree of transformations in individuals
zation that PA follows muscle thickness in pre- with STCP.
dicting strength of skeletal muscles. There were Morphologically, the EO, IO and TrA although
no similar reports on thin or flat muscles such as appear to be pennated as seen our results, the
occur on the anterior and anterolateral abdominal extent of pennation of these muscle could not be
wall. All the reported positive correlation cases compared to the levels as reported for the limb
between muscle thickness and PA would need to muscles with a large PA ranging from 18 to
be established first in the abdominal muscles and 40.17,29 Therefore, to imply that the PA in the
other flat/thin muscles, as observed in the limb abdominal muscles is significant and could be
muscles,17,29 before any consideration of regimen equated to generating muscle force much the
changes in rehabilitation of muscle disorders same way as the limb muscles would be without
based on these facts and figures regarding any of adequate scientific and statistically supporting
the MAP. The lack of empirical evidence of a evidence. Additionally, the characterization of
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S. Adjenti et al.
this MAP (change from rest to activity), seems pennation of the muscle fibers with respect to
suggestive that PA may not distinguish indivi- the lines of pull of these muscles. Further in-
duals with STCP from those of TD with regard to vestigation is required on this muscle param-
force generating capacity and maintenance of eter in order to fully understand its role in the
stability at the bony pelvis. abdominal muscle function with respect to
trunk stability.
CONCLUSION
Our study summarizes that apart from the
rectus abdominis muscle, the PA of the oblique ACKNOWLEDGMENTS
and transverse abdominal muscles in indivi- Special thanks to the staff and learners of all the
duals with STCP differs from those from TD schools from which participants were recruited
individuals. The changes in PA between the for this study. The authors are also grateful to
active and resting stages in both groups seem the technical staff of the Division of Anatomy of
suggestive that PA as a muscle parameter the Department of Human Biology, Faculty of
might have undergone some structural and Health Sciences, University of Cape Town, for
functional transformations in individuals with transporting the equipment to and from the data
STCP. Our study recorded PA of zero degrees sampling sites. Finally, we appreciate the fi-
for the rectus abdominis muscle in both groups nancial inputs of both faculty and management
of participants, suggesting that this muscle is of the postgraduate units of the Faculty of
non-pennated. The oblique and transverse Health Sciences of the University of Cape
abdominis muscles on the other hand showed Town and University of Ghana Medical School
that PA scores were relatively small (less toward the doctoral training of the principal
than 3 at their peak), indicative of a weak investigator.
APPENDIX A.
Table A.1 Inter-rater Test for Measurement of Pennation Angle (PA)
During Resting Stage (R) Between PI and AR (STCP; N= 15).
PI AR Diff SD Diff ICC (95% CI) SEM
EO R () 2.0  0.2 2.2  0.3 0.2 0.13 0.93 (0.76–0.97) 0.97
IO R () 2.3  0.2 2.2  0.2 0.1 0.28 0.89 (0.66–0.96) 0.81
TrA R () 1.5  0.5 1.6  0.4 0.1 0.22 0.85 (0.53–0.94) 0.57
RA R () 0.0 0.0 0.0 0.00 0.00 0.00
Notes: PI ¼ Measurements of Principal Investigator; AR ¼ Measurements of
Assistant Researcher; Diff ¼ difference between PI & AI; SD Diff ¼ standard
deviation of the differences; ICC ¼ intra-class confident co-efficient; CI ¼
confident interval; and SEM ¼ standard error of means.
1850008-10
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Pennation Angle and the Anterior Abdominal Wall Muscles
Table A.2 Inter-rater Test for Measurement of Pennation Angle (PA) During
Active Stage (Ac) Between PI and AR (STCP; N= 15).
PI AR Diff SD Diff ICC (95% CI) SEM
EO Ac () 1.8  0.5 2.2  0.2 0.4 0.18 0.90 (0.78–0.96) 1.10
IO Ac () 2.0  0.3 2.2  0.2 0.2 0.32 0.91 (0.79–0.96) 0.79
TrA Ac () 1.5  0.5 1.5  0.5 0.0 0.25 0.94 (0.87–0.98) 0.60
RA R () 0.0 0.0 0.0 0.00 0.00 0.00
Notes: PI ¼ Measurements of Principal Investigator; AR ¼ Measurements of
Assistant Researcher; Diff ¼ difference between PI & AI; SD Diff ¼ standard
deviation of the differences; ICC ¼ intra-class confident co-efficient; CI ¼ con-
fident interval; and SEM ¼ standard error of means.
Table A.3 Inter-rater Test for Measurement of Pennation Angle (PA)
During Resting Stage (R) Between PI and AR (TD; N= 15).
PI AR Diff SD Diff ICC (95% CI) SEM
EO R () 1.6  0.2 1.6  0.2 0.0 0.39 0.95 (0.65–0.99) 0.58
IO R () 2.0  0.2 2.1  0.4 0.1 0.32 0.93 (0.60–0.97) 0.62
TrA R () 1.4  0.2 1.5  0.2 0.1 0.43 0.92 (0.80–0.94) 0.61
RA R () 0.0 0.0 0.0 0.00 0.00 0.00
Notes: PI ¼ Measurements of Principal Investigator; AR ¼ Measurements of
Assistant Researcher; Diff ¼ difference between PI & AI; SD Diff ¼ standard
deviation of the differences; ICC ¼ intra-class confident co-efficient; CI ¼
confident interval; and SEM ¼ standard error of means.
Table A.4 Inter-rater Test for Measurement Pennation Angle (PA) During
Active Stage (Ac) Between PI and AR (TD; N= 15).
PI AR Diff SD Diff ICC (95% CI) SEM
EO Ac () 1.8  0.2 1.8  0.2 0.0 0.35 0.94 (0.58–0.98) 0.53
IO Ac () 2.2  0.2 2.3  0.3 0.1 0.44 0.96 (0.52–0.96) 0.60
TrA Ac () 1.5  0.3 1.6  0.2 0.1 0.38 0.95 (0.65–0.99) 0.65
RA Ac () 0.0 0.00 0.0 0.00 0.00 0.00
Notes: PI ¼ Measurements of Principal Investigator; AR ¼ Measurements of
Assistant Researcher; Diff ¼ difference between PI & AI; SD Diff ¼ standard
deviation of the differences; ICC ¼ intra-class confident co-efficient; CI ¼ con-
fident interval; and SEM ¼ standard error of means.
References 3. Andersson C, Mattsson E. Adults with cerebral palsy:
A survey describing problems, needs and resources
1. AbeT, BrechueWF, Fujita S, Brown JB.Gender differences with emphasis on locomotion. Dev Med Child Neurol
in FFM accumulation and architectural characteristics of
43:76–82, 2001.
muscles. Med Sci Sports Exercise 30:1066–1070, 1998. 4. Benard MR, Becher JG, Harlaar J, Huijing PA, Jaspers
2. Aggeloussis N, Giannakou E, Albracht K, Arampatzis RT. Anatomical information is needed in ultrasound
A. Reproducibility of fascicle length and pennation imaging of muscle to avoid potentially substantial
angle of gastrocnemius medialis in human gait in vivo. errors in measurement of muscle geometry. Muscle
Gait & Posture 31:73–77, 2010.
Nerve 39:652–665, 2009.
1850008-11
J. Musculoskelet. Res. 2018.21. Downloaded from www.worldscientific.com
by Marianne Unger on 01/25/19. Re-use and distribution is strictly not permitted, except for Open Access articles.
S. Adjenti et al.
5. Binzoni T, Bianchi S, Hanquinet S, Kaelin A, Sayegh Y, 18. Kawakami Y, Abe T, Kanehisa H, Fukunaga T.
Dumont M, Jequier S. Human gastrocnemius medialis Human skeletal muscle size and architecture: Variabil-
pennation angle as a function of age: From newborn to ity and interdependence. Am J Hum Biol 18:845–858,
elderly. J Physiol Anthropol Appl Human Sci 20:293–298, 2006.
2001. 19. Klimstra M, Dowling J, Durkin JL, MacDonald M.
6. Brener ND, McManus T, Galuska DA, Lowry R, The effect of ultrasound probe on muscle architecture
Wechsler H. Reliability and validity of self-reported measurement. J Electromyogr Kinesiology 17:504–514,
height and weight among High school students. J Ad- 2007.
olescent Health 32:281–287, 2003. 20. Legerlotz K, Smith HK, Hing WA. Variation and reli-
7. Bunce SM, Moore AP, Hough AD. M-mode ultrasound, ability of ultrasonographic quantification of the archi-
a reliable measure of transversus abdominis thickness? tecture of medial gastrocnemius muscle in young
Clin Biomech (Bristol Avon) 17:315–317, 2002. children. Clin Physiol Funct Imaging 30:198–205, 2010.
8. Burtner PA, Qualls C, Woollacott MH. Muscle activa- 21. Lichtwark GA, Wilson AM. Is Achilles tendon compli-
tion characteristics of stance balance control in children ance optimised for maximum muscle efficiency during
with spastic cerebral palsy. Gait & Posture 8:163–174, locomotion? J Biomech 40:1768–1775, 2007.
1998. 22. Lieber RL, Friden J. Functional and clinical significance
9. Damiano DL, Martellota TL, Sullivan DJ, Granata KP, of skeletal muscle architecture. Muscle Nerve 23:1647–
Abel MF. Muscle force production and functional per- 1666, 2000.
formance in spastic cerebral palsy: Relationship of 23. Muramatsu T, Muraoka T, Kawakami Y, Shibayama A,
cocontraction. Arch Phys Med Rehabil 81:895–900, 2000. Fukunaga T. In vivo determination of fascicle curva-
10. Ferreira PH, Ferreira ML, Hodges PW. Changes in re- ture in contracting human skeletal muscles. J Appl
cruitment of abdominal muscles in people with low Physiol 92:129–134, 2002.
back pain: Ultrasound measurement of muscle activity. 24. Narici MV, Binzoni T, Hiltbrand E, Fasel J, Terrier F,
Spine 29:2560–2566, 2004. Ceretelli P. In vivo human gastrocnemius architecture
11. Hodges PW. Pain and motor control: From the labora- with changing joint angle at rest and during guarded
tory to rehabilitation. J Electromyogr Kinesiol 21:220 228, isometric contraction. J Physiol 496(1):287–297, 1996.–
2011. 25. Ohata K, Haruta T, Kato T, Nakamura T. Relation be-
12. Hodges PW, Richardson CA. Inef cient muscular sta- tween muscle thickness, spasticity, and muscle limita-fi
bilisation of lumbar spine associated with low back tion in children and adolescents with cerebral palsy.
pain. A motor control evaluation of transversus abdo- Dev Med Child Neurol 50:152–156, 2008.
minis. Spine 21:2640–2650, 1996. 26. Palisano RJ, Hanna SE, Rosenbaum PL, Russell DJ,
13. Hodges P, Richardson CA. Altered trunk muscle re- Walter SD, Wood EP, Raina PS, Galuppi BE. Validation
cruitment in people with low back pain with upper of a model of gross motor function for children with
limb movement at different speed. Arch Phys Med cerebral palsy. Physical Therapy 80:974–985, 2000.
Rehabil 80:1005 1012, 1999. 27. Richardson CA, Snijders CJ, Hides JA, Damen L, Pas–
14. Hodges PW, Eriksson AE, Shierley D, Gandevia SC. MS, Storm J. The relation between the transversus
Intra-abdominal pressure increases stiffness of the abdominis muscles, sacroiliac joint mechanics, and low
lumbar spine. J Biomech 38(9):1873–1880, 2005. back pain. Spine 27:399–405, 2002.
15. Hodges PW, Pengel LHM, Herbert RD, Gandevia SC. 28. Shortland AP, Harris CA, Gough M, Robinson RO.
Measurement of muscle contraction with ultrasound Architecture of the medial gastrocnemius in children
imaging. Muscle Nerve 27:682 692, 2003. with spastic diplegia. Dev Med Child Neurol 44:158–163,–
16. Infantolino BW, Challis JH. Architectural properties of 2002.
the rst dorsal interosseus muscle. J Anat 216:463 469, 29. Wakahara T, Miyamoto N, Sgissaki N, Murata K,fi –
2010. Kanehisa H, Kawakami Y, Fukunaga T, Yanai T. As-
17. Iwanuma S, Akagi R, Kurihara T, Ikegawa S, Kanehisa sociation between regional differences in muscle acti-
H, Fukunaga T, Kawakami Y. Longitudinal and trans- vation in one session of resistance exercise and muscle
verse deformation of human Achilles tendon induced hypertrophy after resistance training. Eur J Appl Physiol
by isometric plantar flexion at different intensities. J 112:1569–1576, 2012.
Appl Physiol 110:1615–1621, 2011.
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