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Lumbar spine stability can be augmented with an abdominal belt and/or increased intra-abdominal pressure

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The increased intra-abdominal pressure (IAP) commonly observed when the spine is loaded during physical activities is hypothesized to increase lumbar spine stability. The mechanical stability of the lumbar spine is an important consideration in low back injury prevention and rehabilitation strategies. This study examined the effects of raised IAP and an abdominal belt on lumbar spine stability. Two hypotheses were tested: (1) An increase in IAP leads to increased lumbar spine stability, (2) Wearing an abdominal belt increases spine stability. Ten volunteers were placed in a semi-seated position in a jig that restricted hip motion leaving the upper torso free to move in any direction. The determination of lumbar spine stability was accomplished by measuring the instantaneous trunk stiffness in response to a sudden load release. The quick release method was applied in isometric trunk flexion, extension, and lateral bending. Activity of 12 major trunk muscles was monitored with electromyography and the IAP was measured with an intra-gastric pressure transducer. A two-factor repeated measures design was used (P < 0.05), in which the spine stability was evaluated under combinations of the following two factors: belt or no belt and three levels of IAP (0, 40, and 80% of maximum). The belt and raised IAP increased trunk stiffness in all directions, but the results in extension lacked statistical significance. In flexion, trunk stiffness increased by 21% and 42% due to 40% and 80% IAP levels respectively; in lateral bending, trunk stiffness increased by 16% and 30%. The belt added between 9% and 57% to the trunk stiffness depending on the IAP level and the direction of exertion. In all three directions, the EMG activity of all 12 trunk muscles increased significantly due to the elevated IAP. The belt had no effect on the activity of any of the muscles with the exception of the thoracic erector spinae in extension and the lumbar erector spinae in flexion, whose activities decreased. The results indicate that both wearing an abdominal belt and raised IAP can each independently, or in combination, increase lumbar spine stability. However, the benefits of the belt must be interpreted with caution in the context of the decreased activation of a few trunk extensor muscles.
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Abstract The increased intra-abdo-
minal pressure (IAP) commonly ob-
served when the spine is loaded dur-
ing physical activities is hypothsized
to increase lumbar spine stability.The
mechanical stability of the lumbar
spine is an important consideration
in low back injury prevention and re-
habilitation strategies. This study ex-
amined the effects of raised IAP and
an abdominal belt on lumbar spine
stability. Two hypotheses were tes-
ted: (1) An increase in IAP leads to
increased lumbar spine stability, (2)
Wearing an abdominal belt increases
spine stability. Ten volunteers were
placed in a semi-seated position in a
jig that restricted hip motion leaving
the upper torso free to move in any
direction. The determination of lum-
bar spine stability was accomplished
by measuring the instantaneous trunk
stiffness in response to a sudden load
release. The quick release method
was applied in isometric trunk flex-
ion, extension, and lateral bending.
Activity of 12 major trunk muscles
was monitored with electromyogra-
phy and the IAP was measured with
an intra-gastric pressure transducer.
A two-factor repeated measures de-
sign was used (P < 0.05), in which
the spine stability was evaluated un-
der combinations of the following
two factors: belt or no belt and three
levels of IAP (0, 40, and 80% of
maximum). The belt and raised IAP
increased trunk stiffness in all direc-
tions, but the results in extension
lacked statistical significance. In fle-
xion, trunk stiffness increased by
21% and 42% due to 40% and 80%
IAP levels respectively; in lateral
bending, trunk stiffness increased by
16% and 30%. The belt added be-
tween 9% and 57% to the trunk stiff-
ness depending on the IAP level and
the direction of exertion. In all three
directions, the EMG activity of all
12 trunk muscles increased signifi-
cantly due to the elevated IAP. The
belt had no effect on the activity of
any of the muscles with the excep-
tion of the thoracic erector spinae in
extension and the lumbar erector
spinae in flexion, whose activities
decreased. The results indicate that
both wearing an abdominal belt and
raised IAP can each independently,
or in combination, increase lumbar
spine stability. However, the benefits
of the belt must be interpreted with
caution in the context of the de-
creased activation of a few trunk ex-
tensor muscles.
Key words Lumbar spine, stability ·
Lumbar spine, intra-abdominal
pressure · Lumbar spine, abdominal
belts · Lumbar spine,
electromyography
ORIGINAL ARTICLE
Eur Spine J (1999) 8:388–395
© Springer-Verlag 1999
Jacek Cholewicki
Krishna Juluru
Andrea Radebold
Manohar M. Panjabi
Stuart M. McGill
Lumbar spine stability can be augmented
with an abdominal belt
and/or increased intra-abdominal pressure
Received: 17 August 1998
Revised: 1 March 1999
Accepted: 18 March 1999
This study was supported by a grant from
Gaylord Rehabilitation Research Institute
J. Cholewicki () · K. Juluru ·
A. Radebold · M. M. Panjabi
Biomechanics Laboratory,
Department of Orthopaedics
and Rehabilitation,
Yale University School of Medicine,
P.O. Box 208071, New Haven,
CT 06520-8071, USA
e-mail: cholewicki@biomed.med.yale.edu,
Tel.: +1-203-737 2887,
Fax: +1-203-785 7069
S. M. McGill
Occupational Biomechanics Laboratories,
Department of Kinesiology,
Faculty of Applied Health Sciences,
University of Waterloo, Waterloo,
Ontario, Canada
Introduction
Chronic low back pain (LBP) creates a profound socio-
economic problem in today’s society [17, 18, 28, 51, 70].
Recent studies support the hypothesis that patients suffer-
ing from LBP of mechanical origin try to compensate for
their injuries with additional or different muscle recruit-
ment patterns, presumably to increase spine stability [4, 9,
14, 56, 61]. In healthy individuals, mechanical stability is
provided to the spine by trunk muscles and ligaments [5,
6, 11, 19, 20]. Injuries and chronic mechanical defects in
the osteoligamentous structures reduce spine stability
[53]. To maintain a normal level of stability, trunk mus-
cles must compensate by altering their normal activation
pattern [54, 55]. The question of whether wearing the ab-
dominal belt or the rise in the intra-abdominal pressure
(IAP) can increase the lumbar spine stability to protect it
from acute low back injury, still remains unanswered.
The early hypotheses that the IAP relieves part of the
compressive loads borne by the lumbar spine [1, 27, 49]
have been accepted by some [12, 22, 34, 35, 65, 66] and
refuted by others [2, 29–31, 42, 50, 52]. The current con-
sensus seems to be that the compressive forces, arising
from the contraction of abdominal wall musculature to
generate the IAP, offset the beneficial action of the hydro-
static forces thought to alleviate spinal compression via
IAP. The increased IAP commonly observed when the
spine is loaded during physical activities is hypothesized
to increase lumbar spine stability [41–44, 63]. For ex-
ample, patients with nonspecific low back pain exhibit
higher IAP during lifting than normal controls [16, 23].
The IAP also increases in response to a sudden trunk load-
ing in healthy individuals [10]. The above cited studies in-
directly point towards the association of IAP with the me-
chanical stability of the lumbar spine. However, direct ex-
periments are needed to test this hypothesis.
Abdominal belts have been shown to help individuals
in generating higher IAP levels during load-handling ac-
tivities [22, 34, 35, 43]. There exists anecdotal evidence
that people “feel safer” wearing abdominal belts when ex-
erting large forces [38]. This is especially true for weight
lifters and power lifters, who use belts apparently for no
obvious benefit other than to increase their IAP during
lifting [22, 34, 35]. While a few studies reported marginal
improvement in lifting capacity with the use of abdominal
belts [59, 62], the overwhelming evidence suggests that
belts have no effect on muscle strength [37, 39, 58], fa-
tigue [8, 39], or low back injury incidence [48, 57, 69].
Although one of the epidemiological studies claimed that
belt wearing reduced the number of low back injuries
[32], several methodological flaws make such interpreta-
tion of the results questionable. The most serious concern
was that the belt wearing policy was not the sole er-
gonomic intervention implemented at the time of this
study. At the present time, it appears that abdominal belts
are widely prescribed in industry and rehabilitation with-
out a convincing scientific justification of their benefits
[3, 13, 24, 45, 47, 68]. Often reported subjective feelings
of increased support may stem from abdominal belts pas-
sively increasing trunk stiffness and/or reducing its range
of motion [21, 36, 46, 60, 64]. However, the direct evi-
dence that belts modulate spine stability is still lacking.
The purpose of the present study was to examine the
effect of IAP and wearing an abdominal belt on lumbar
spine stability by measuring trunk stiffness with a quick
release method in trunk flexion, extension, and lateral
bending. Two hypotheses were tested:
1. An increase in IAP leads to increased lumbar spine sta-
bility, and
2. Wearing an abdominal belt helps to increase spine sta-
bility. Activity of major trunk muscles was monitored
with electromyography to add to the interpretation of
results.
Materials and methods
This was a two-factor experimental design in which spine stability,
a dependent variable, was evaluated under a combination of two
independent variables: wearing or not wearing the abdominal belt
and the level of intra-abdominal pressure (IAP). The determination
of lumbar spine stability was accomplished by measuring the in-
stantaneous trunk stiffness in response to a sudden load release that
subjects were resisting (quick release method). Electromyographic
signals (EMG) from major trunk muscles were recorded before
and after the release to add to the interpretation of results.
Ten subjects with no previous history of low back pain (aver-
age age 28, SD 4 years; height 177, SD 7 cm; weight 78, SD 14 kg)
were placed in a semi-seated position in a jig that restricted hip
motion leaving the upper torso free to move in any direction (Fig.
1). In the quick release method, the subjects exerted isometric
trunk extension, flexion, and lateral bending to the left, at 35% of
their maximum, resisting a cable attached to a chest harness at ap-
proximately the T9 level. The cable was held with an electromag-
net, which was suddenly released by the researcher (without warn-
ing the subject) when the required force level was achieved. The
resulting trunk motion was measured at 100 Hz with an inductive
sensor (Flock of Birds, Ascension Technologies, VT) placed on
the back at the T9 level.
The EMG signals were recorded from 12 muscles (left and right
rectus abdominis, external and internal oblique, latissimus dorsi,
thoracic and lumbar erector spinae) according to a previously es-
tablished protocol [5, 6]. The signals were band-pass preamplified
between 20 and 500 Hz, amplified, and converted to digital data at
1600 Hz. It was assumed that a muscle activation pattern estab-
lished prior to a sudden trunk perturbation determines the spine
stability and, in turn, the kinematics of the trunk response to that
perturbation. Accordingly, 200 ms of EMG data, recorded imme-
diately before the magnet release, were digitally rectified and aver-
aged. The baseline EMG values, recorded when the subjects were ly-
ing completely relaxed, were subtracted from the quick release EMG.
These baseline signals contained mostly electrode and amplifier noise.
Finally, the data were normalized to the EMG activity recorded dur-
ing the maximum voluntary contractions (MVC). With the exception
of lateral bending trials, left and right EMG values were averaged.
The IAP was measured with a transducer (Micro-tip MPC500,
Millar Instruments, TX) inserted into the stomach via the naso-
esophageal pathway. The subjects were instructed to increase their
IAP with the Valsalva maneuver and to hold it at the indicated
389
390
level while slowly increasing the trunk isometric force. The IAP
and the desired IAP target level lines were displayed on an oscillo-
scope for visual feedback to the subjects. Once the trunk isometric
force had reached its target, without warning, the researcher initi-
ated the data collection by releasing the electromagnet. All data
were collected in the about trigger mode for 1 s before and 2 s af-
ter the release.
Values for trunk stiffness were obtained from the trunk motion
data in accordance with a standard quick release protocol [25, 26,
33, 67, 72]. The trunk was modeled as a second-order system with
viscoelastic properties oscillating freely after the release of a mo-
ment that subjects were resisting. Amplitude and frequency of
such oscillations measured immediately after the release, but be-
fore voluntary muscle intervention took place, were determined by
trunk inertia (I), damping coefficient (B) and stiffness coefficient
(K) established prior to the release:
(1)
where θ is the trunk angle, mg is trunk weight, and L is the height
measured from the L5-S1 joint to the center of trunk mass, as-
sumed to be at T9 level. Trunk mass and moment of inertia were
calculated from the subject’s weight and height [71]. Coefficients
B, K and one additional integration constant C were obtained with
a curve fitting algorithm where the objective was to gain the best
match between the modeled and measured trunk rotation trajecto-
ries. This procedure was applied to the double integrated Equation 1
[67], because integration is numerically a more robust operation
than differentiation:
(2)
A preliminary study indicated that the minimum length of a data
record needed to identify parameters in the Equation 2 accurately
was equivalent to at least one-quarter of the wavelength. There-
fore, angular trunk motion data, taken from the time of magnet re-
lease to the point of maximum trunk deflection, was used for a
curve fit (Fig.2).
In each quick release direction, three trials were performed at
each of the three IAP levels (0, 40, and 80% of individual’s maxi-
mum). To reduce the testing time, only the 0% and 80% IAP trials
were repeated while wearing a standard 10-cm-wide nylon belt
(model SANB4, Altus Athletic, Altus, OK). A force of 180 N,
measured with a spring scale, was used to tighten the belt while the
subjects were actively attempting to minimize their waist circum-
ference. This force was used to standardize the belt tightness to a
moderate, comfortable level. All trials were performed in a ran-
domized order.
Trunk stiffness coefficients were averaged between three trials
and normalized for each subject to the stiffness value obtained
with no belt and no IAP. The effect of belt and IAP level, (inde-
pendent variables), on trunk stiffness, (a dependent variable), was
tested with two-factor, repeated measures ANOVA (2 × 3 unbal-
anced design, P < 0.05).
Results
On average, Equation 2 fitted the trunk angular deflection
data with Root mean square (RMS) error of 0.47° (SD =
0.56°) (Fig.2). Although the subjects were instructed to
maintain their IAP level at a given target, some variation
was present. In addition, it was not possible to have no
IAP when generating isometric trunk exertions. There-
fore, the average (SD) IAP values measured at the time of
magnet release were 14.1 (5.8), 42.8 (8.0), and 71.3 (9.3)
% of maximum for the trials labeled as 0, 40, and 80% re-
spectively.
I B dt K dt Ct mgL dtθθ θ θ + + + = sin
∫∫∫∫
22 2
I B K mgL
˙˙ ˙
θθθ θ + + = sin
Fig.1 A subject positioned in a hip motion restraining apparatus.
The intra-abdominal pressure (IAP) was built up with Valsalva
maneuver up to the target level, while subjects resisted the cable
load of 35% of their maximum. Stability was assessed upon the
electromagnet release of the cable load
Fig.2 An example of the trunk rotation responses to sudden un-
loading. The three curves represent trials under the following con-
ditions: (0% IAP) a subject was instructed not to increase his intra-
abdominal pressure, (80% IAP) a subject was instructed to reach a
target set at 80% IAP, (Belt) a subject was wearing an abdominal
belt and was instructed not to increase his intra-abdominal pres-
sure. Markers indicate the raw data and the lines indicate a curve
fit according to the Equation 2. K = Normalized trunk stiffness
Both the belt and IAP increased trunk stiffness in all
directions, but the results in extension lacked statistical
significance and will not be emphasized further (Fig.3A).
There were no interactions between the belt and IAP ef-
fects in any of the three directions. In flexion, trunk stiff-
ness increased by 21% and 42% due to 40% and 80% IAP
levels respectively (Fig.3B); in lateral bending, trunk
stiffness increased by 16% and 30% (Fig.3C). With no
IAP, the belt increased trunk stiffness by 29% and 9% in
flexion and lateral bending respectively. At 80% of maxi-
mum IAP, the belt added 41% to the trunk stiffness in
flexion and 57% in lateral bending. The effects of both fac-
tors on trunk stiffness were additive. Thus, the combined
effects of wearing an abdominal belt and the increased IAP
level to 80% of maximum provided 83% and 86% more
trunk stiffness in flexion and lateral bending respectively.
In all three directions, the EMG activity of all 12 trunk
muscles increased significantly due to the increased IAP
(Figs.4–6). The belt had no effect on the activity of any of
the muscles, with the exception of the thoracic erector
spinae in extension and the lumbar erector spinae in flex-
ion. Activity of those muscles decreased significantly
only at 80% IAP level due to wearing the belt (Figs.4, 5).
Discussion
Effects of the increased intra-abdominal pressure (IAP)
and the wearing of an abdominal belt on lumbar spine sta-
391
Fig.3A–C Normalized trunk stiffness obtained from a quick re-
lease method for various combinations of intra-abdominal pressure
and belt conditions. A Quick release in trunk extension, B flexion,
and C lateral bending to the left
Fig.4 Intra-abdominal pressure (% maximum) and belt effects on
muscle activity (% maximum voluntary contraction, MVC) aver-
aged 200 ms prior to the load release in trunk extension trials (RA
rectus abdominis, EO external oblique, IO internal oblique, LD
latissimus dorsi, TE thoracic erector spinae, LE lumbar erector
spinae)
Fig.5 Intra-abdominal pressure (% maximum) and belt effects on
muscle activity (% MVC) averaged 200 ms prior to the load re-
lease in trunk flexion trials
A B C
bility were studied by measuring the kinematics of trunk
response to a sudden load release, according to the so-
called quick release protocol. The more stable the struc-
ture prior to a perturbation (load release in this case), the
smaller is its deflection amplitude and the higher is its
oscillation frequency in response to that perturbation
(Fig.2). To quantify these trunk displacements, Equation
2 was used. Although Equation 2 represents a simplified
model, it fit the experimental data very well (average
RMS error < 0.5°).
In a quick release method, the stability of a multi de-
gree-of-freedom system is characterized by the aggregate
mechanical impedance parameters: inertia, damping, and
stiffness coefficients. The latter (stiffness) determines the
stability of the static equilibrium. It was this stiffness that
was used in the present study to quantify spine stability at
the time of load release. All three coefficients computed
from the trunk kinematics were dependent on the formu-
lation of the model and the assumed height, mass, and in-
ertia parameters (Equation 2). However, because the same
model was used in all conditions tested for each individ-
ual, and because only relative values of stiffness were an-
alyzed, the reliability of the results was assured.
The results indicated that both wearing an abdominal
belt and increased IAP can each independently, or in com-
bination, increase trunk stiffness, and therefore, increase
lumbar spine stability under sudden loading/unloading
conditions. However, the activation patterns of trunk mus-
cles suggest that the mechanisms of the spine stabilization
are different for those two factors. It is likely that the in-
crease in spine stability due to IAP was gained from the
concomitant increase in muscle coactivation needed to
generate a high IAP. This observation is consistent with
the IAP mechanism described by Cholewicki et al. [7].
These authors demonstrated with a physical and biome-
chanical model that the contraction of abdominal muscles
necessary to create IAP would stiffen the lumbar spine area.
Stabilizing the lumbar spine with the belt alone is most
likely a passive mechanism stemming from the interaction
of the wide and stiff belt placed between the ribcage and
pelvis. In contrast to the increased IAP effect, there was
virtually no change in muscle activity whether the belt
was worn or not. The exception of the thoracic and lum-
bar erector spine muscles, whose activation was signifi-
cantly smaller when the belt was worn in trunk extension
and flexion respectively, indicates further that a passive,
and not an active, mechanism was responsible for the in-
creased spine stability. These results are consistent with
McGill et al. [46], who reported an increase in passive
trunk stiffness in lateral bending and axial rotation due to
wearing an abdominal belt.
While it is clear that a belt itself contributes to lumbar
spine stability, as does the voluntary increase in IAP, its
benefits must be interpreted with caution. The fact that the
activity of some muscles decreased when the belt was
worn may indicate the reduction in overall muscle coacti-
vation causing reduction in active spine stabilization by
the muscles. Perhaps subjects perceived added stiffness
derived from the belt, and they therefore decreased mus-
cle coactivation. If this is the case, long-term abdominal
belt usage may lead to regression of the active spine sta-
bilizing system. This hypothesis would be consistent with
the outcome of a large study dealing with the incidence of
low back injury and long-term belt usage among airline
workers [57]. They found that abdominal belt use did not
reduce overall incidence of back injuries. However, when
the belts were removed after several months, frequency of
low back injuries increased. If our subjects had had time
to get used to wearing the belt, we might not have seen
any increase in the spine stability. The belt effect might
have been negated completely by decreased muscle coac-
tivation. Future studies should address the effects of long-
term belt usage on spine stability and on the stabilizing
function of trunk musculature.
Although the effects of IAP and a belt on spine stabil-
ity were studied here only in an upright posture, the re-
392
Fig.6A, B Intra-abdominal pressure (% maximum) and belt ef-
fects on muscle activity (% MVC) averaged 200 ms prior to the
load release in trunk lateral bending to the left trials. A Right side
muscles, B left side muscles (Subscripts R and L indicate the side)
A
B
393
sults could be extrapolated to other tasks and kinds of
lumbar supports. If the increase in IAP is possible in a
given posture, then the increase in spine stability will fol-
low by the virtue of abdominal muscle coactivation. If the
belt passively stiffens the trunk in an upright posture, it is
likely that this effect will be even more pronounced when
the spine moves away from the neutral posture, or when a
wider and stiffer belt is used. However, the spine is most
vulnerable to loss of stability when it is in a neutral pos-
ture [5, 6]. While only the trunk-unloading mode was stud-
ied,
it was used to estimate the instantaneous trunk stiff-
ness and consequently the stability of the lumbar spine in
the state in which it was at the time of load release. If the
spine becomes more stable, it will exhibit greater resis-
tance to perturbation, irrespective of whether this pertur-
bation occurs in a spine loading or unloading mode. Fur-
thermore, the quick release tasks, used in this study to
es
timate spine stability, may simulate spine unloading
events
occurring during sudden slips and trips that often
result in an accidental low back injury while handling
loads [40].
The findings of the present study are relevant to the
design of low back injury prevention and rehabilitation
strategies. Increased spine stability may provide greater
protection against injury following unexpected or sudden
loading. Therefore, the increased IAP and/or muscle coac-
tivation observed in low back pain patients and prescrip-
tion of abdominal belts may serve to compensate the ini-
tial injury to the spine and to restore or increase its stabil-
ity [54, 55]. Lumbar supports and orthotics are among the
commonly prescribed modalities for prevention and treat-
ment of low back pain. There exists a concern, however,
that a long-term usage of lumbar supports may lead to
trunk muscle weakness [15] and increased risk of injury
when the wearing of lumbar supports is discontinued [57].
In some specific cases, abdominal belts may be beneficial
in helping injured workers return earlier to work [69]. Im-
proved understanding of the mechanism by which IAP
and abdominal belts increase lumbar spine stability will
help to define better both the target population and the
length of time for the treatment with lumbar supports to
be the most effective.
The variability among the individual trunk stiffness
values along with variability in muscle activation patterns
suggests some interaction among active spine stabilizing
strategies. Cholewicki et al. [7] identified two possible
mechanisms by which trunk muscles can stabilize the
lumbar spine. One was antagonistic muscle coactivation
and the second was activation of only the abdominal mus-
culature and generation of IAP. Using a physical model,
they demonstrated that both of these mechanisms might
function separately or in combination, leading to different
critical load (stability) values. To verify this hypothesis,
calculations of spine stability should be performed with a
detailed mathematical model [5] using the EMG values
obtained in this study as input. If the muscle activation
patterns alone can predict the spine stability, then the IAP
and abdominal belt mechanisms for stabilizing the lumbar
spine hypothesized here and by Cholewicki et al. [7] will
be supported. Future studies may also provide an explana-
tion for the lack of a more pronounced increase in spine
stability due to the IAP and belt in trunk extension.
Conclusions
1. Both wearing an abdominal belt and raising IAP can
each independently, or in combination, increase lum-
bar spine stability.
2. Increase in spine stability due to high IAP is likely
gained from the concomitant increase in muscle coac-
tivation needed to generate this IAP. In contrast, the
stabilizing effect of the belt alone appears to be a pas-
sive mechanism.
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... The passive use of LSO is argued to increase lumbar stiffness without increasing lumbar compressing forces. 18 In addition, it has been widely used in clinical practice to relieve pain, reduce functional limitations, and limit medicament consumption. 19 Notwithstanding, results on the benefits provided by the LSO for individuals with CLBP are controversial, 20 and the potential effect of the LSO for treating a CLBP remains unclear. ...
... Therefore, this study aimed to examine the immediate effects of the LSO and ADIM on trunk postural control of adults with CLBP compared with asymptomatic controls during OLS and ST tasks. Due to their known effects on lumbar stiffness, 12,18 we hypothesized that individuals with CLBP would improve their postural control-related outcomes by immediately changing linear variables derived from the COP excursions after using LSO and ADIM interventions while standing on a force platform. Recording COP excursions while standing is one of the most used methods to assess postural control in response to balance perturbation caused by surface or sensory manipulation. ...
... Our data do not support our hypothesis that both interventions would significantly change linear variables derived from COP parameters and postural control, more so in individuals with CLBP than in asymptomatic controls (group £ condition interaction). Effectively, considering that the central nervous system monitors the spine against factors that threaten balance control, such as pain intensity and poor lumbar proprioception, our initial expectation was that both treatment approaches (LSO, ADIM) could adjust trunk muscle activation to enhance spine stiffness 12,18 and balance control. These adjustments were expected to improve the postural control responses while facing the high challenge imposed by the 2 balance tasks tested. ...
Article
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Objective The purpose of this study was to examine the immediate effects of lumbosacral orthosis and the abdominal drawing-in maneuver on the trunk postural control of adults with chronic low back pain compared with asymptomatic controls during 1-legged and semi-tandem stances. Methods An experimental and comparative study (cross-sectional design) was conducted in a laboratory setting. Twenty adults with chronic low back pain and 20 asymptomatic controls randomly performed 2 postural balance tasks over a force platform, considering 3 experimental conditions: (1) natural posture (baseline-control), (2) lumbosacral orthosis, and (3) abdominal drawing-in maneuver. Linear variables (mean amplitude, ellipse area, and sway velocity) derived from the center of pressure were computed, and 2-way analysis of variance (group × condition) for repeated measures were conducted. Results No group × condition interactions (.139 ≤ P ≤.938) were detected in any center of pressure parameters. No condition effect was detected, but a group effect (P = .042) was observed for 1 center of pressure parameter. The chronic low back pain group presented with a lower mean anteroposterior center of pressure amplitude than asymptomatic controls (∆ = 0.31 ± 0.66 cm [95% confidence interval, 0.05-0.56], P = .019) during the semi-tandem stance balance task. Conclusion Neither lumbosacral orthosis nor the abdominal drawing-in maneuver showed immediate improvement in trunk postural control in any group. Thus, clinicians should not expect immediate benefits or improvements yielded by lumbosacral orthosis or the abdominal drawing-in maneuver when patients with chronic low back pain undergo these interventions.
... • Use of postural girdle: This recommendation is aimed at ensuring that the load and risk of back injuries by the operator are significantly lower since, by making such loads continuously, the operator is being exposed to possible back injuries that could easily be mitigated with the use of a postural girdle, the latest based on Cholewicki et al. (1999) that states tan a raised Intra-abdominal pressure (IAP) and wearing a postural girdle can each independently, or combined, increase lumber spine stability, but the use of the postural girdle should be with caution in the context of the decreased activation of a few trunk extensor muscles. ...
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Humanity has evolved at an accelerated pace as a result of the great advances in automation and computerization, which demands high mental work. In recent decades, the emergence of a set of new forms of work, which despite the fact that various advantages are attributed to them over traditional forms, do not cease to have innumerable risk factors for the health of the worker that are unknown due to the novelty of the subject. The objective of the present proposal is to provide a physiological basis for the appearance of mental fatigue and its consequences, the international standards related to the subject of mental fatigue, the main models and indicators used for the assessment of mental fatigue and possible measures to reduce mental fatigue in the workplace. It is part of one of the work guidelines established by the International Ergonomics Association (IEA): Cognitive Ergonomics. The research constitutes a theoretical study of mental fatigue in the work context, a descriptive compilation through a bibliographic review of the subject. For this, a systematic search is carried out through the Google Scholar search engine, the repositories of undergraduate thesis of Industrial Engineering of the University of Matanzas and repositories of doctoral theses in Technical Sciences in Cuba. The VOS viewer software is used as tools for a bibliometric analysis and graphic representation of the information collected, as well as the EndNote bibliographic manager. The theoretical elements linked to the appearance of mental fatigue are shown as results, biomolecular, physiological, psychophysiological and psychological indicators are identified for the assessment of mental fatigue at work, as well as models supported by the investigative experience of researchers on the subject. Organizational measures are also identified at the company and individual level that allow preventing episodes of mental fatigue that harm the health of the worker. The adequacy of mental work to the capacities of man is very complex given the large number of variables involved, so it is vitally important to identify the possible risks that may affect the health of the worker in jobs with high cognitive demands and prevent the same to achieve a quality of life in the workplace.
... For example, while every subject was asked to place their non-active hand on their stomach and only employ it in the case they sensed an impending fall, the non-active arm was sometimes used to press the hand on the abdomen. This may have aided in stiffening the trunk by increasing intra-abdominal pressure which has been associated with increases in spinal stability [39,40], much like wearing an abdominal belt has been shown to increase lumbar stiffness [41]. It is possible pressing on their abdomen achieved a similar result. ...
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Background Restoring or improving seated stability after spinal cord injury (SCI) can improve the ability to perform activities of daily living by providing a dynamic, yet stable, base for upper extremity motion. Seated stability can be obtained with activation of the otherwise paralyzed trunk and hip musculature with neural stimulation, which has been shown to extend upper limb reach and improve seated posture. Methods We implemented a proportional, integral, derivative (PID) controller to maintain upright seated posture by simultaneously modulating both forward flexion and lateral bending with functional neuromuscular stimulation. The controller was tested with a functional reaching task meant to require trunk movements and impart internal perturbations through rapid changes in inertia due to acquiring, moving, and replacing objects with one upper extremity. Five subjects with SCI at various injury levels who had received implanted stimulators targeting their trunk and hip muscles participated in the study. Each subject was asked to move a weighted jar radially from a center home station to one of three target stations. The task was performed with the controller active, inactive, or with a constant low level of neural stimulation. Trunk pitch (flexion) and roll (lateral bending) angles were measured with motion capture and plotted against each other to generate elliptical movement profiles for each task and condition. Postural sway was quantified by calculating the ellipse area. Additionally, the mean effective reach (distance between the shoulder and wrist) and the time required to return to an upright posture was determined during reaching movements. Results Postural sway was reduced by the controller in two of the subjects, and mean effective reach was increased in three subjects and decreased for one. Analysis of the major direction of motion showed return to upright movements were quickened by 0.17 to 0.32 s. A 15 to 25% improvement over low/no stimulation was observed for four subjects. Conclusion These results suggest that feedback control of neural stimulation is a viable way to maintain upright seated posture by facilitating trunk movements necessary to complete reaching tasks in individuals with SCI. Replication of these findings on a larger number of subjects would be necessary for generalization to the various segments of the SCI population.
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Background: Low back pain (LBP) is a prevalent disabling ailment that affects people all over the world. A wide variety of orthotic designs, ranging from lumbosacral corsets to rigid thermoplastic thoraco-lumbosacral orthosis are used for managing LBP. Objective: Explore and summarize quality literature on the efficacy of orthotic devices in the management of LBP. Methods: A systematic review and meta-analysis of the literature on the efficacy of orthosis in low back pain management conducted using electronic databases. Studies utilizing orthotic management alone or combined with other therapies for 2 weeks or above were included. A meta-analysis was performed on primary and secondary variables using Mean difference (MD), Inverse variance (IV), and fixed effect model with 95% CI, Physiotherapy Evidence Database (PEDro) scale, Cochrane Risk of Bias 2 (RoB2) tool were used to assess the quality of evidence and the risk bias. Results: Out of 14671 studies, only 13 Randomized Controlled Trials (RCT) were deemed eligible for inclusion in this study, all level 1 evidence. We found that orthotics could significantly mitigate LBP (P-value < 0.00001). Similarly, a significant reeducation in LBP-associated disability was observed after orthotic intervention (P-value 0.004). Conclusion: Lumber orthosis plays a significant role in LBP and associated disability mitigations in sufferers of LBP.
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BACKGROUND: Diaphragm is not used correctly to its fullest potential which can lead to injury provoking compensations. If recruited properly, the diaphragm aids in the production of intra-abdominal pressure, which is necessary for core and spinal stabilization. Intra-abdominal pressure is a key component of our dynamic stability system. OBJECTIVE: The purpose of this study was to determine the interrater and intrarater reliability of the intra-abdominal pressure test in young adults. METHODOLOGY: It is a non-experimental design of test-retest type. 80 subjects (50 women and 30 men) aged 18-28 years with the BMI of < 23.05-24.9 kg/m2 were conveniently included. Subjects with the history of low back pain for past 3 months, any hip or knee surgery for last 1 year, thoracic or thoracoabdominal surgery, postural deformities, cardiorespiratory diseases, pregnancy and pelvic floor dysfunction was excluded. The intra- abdominal pressure test had been carried to the subjects on the same day for the interrater reliability and 1 week later for the intrarater reliability. The signs of proper stabilization with the correct and incorrect activation of the chest and abdominal movements of the subjects were documented independently between the raters and scoring had been done. RESULTS: The results of the study showed an overall excellent interrater reliability of ICC=0.957 and intrarater reliability of ICC= 0.903 of the test. CONCLUSION: The study concludes that there is an overall excellent interrater and intrarater reliability of the intra-abdominal pressure test in normal young adults and hence it can be used in clinical practice. Keywords: Diaphragm, Intra-abdominal pressure, Intra-abdominal pressure test, Core stability, Spinal stability.
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This research focuses on developing a safe, lightweight, power assist device that can be worn by people during lifting or static holding tasks to prevent them from experiencing Low Back Pain (LBP). In consideration of their flexibility, light weight, and large force to weight ratio, two types of pneumatic actuators are employed in assisting low back movement for their safety and comfort. Actuator A is an elongation-type pneumatic rubber artificial muscle that is installed in the outer layer of the garment. Its two ends are fixed on the shoulders and thighs. It can output contractile force, assisting the erector spinae muscles in the same direction. Compared to McKibben-type pneumatic rubber artificial muscle, the elongation type has a larger contraction rate. Actuator B is a layer-type of pneumatic actuator; it is composed of two balloons, and it is installed in the inner layer of the garment. By taking into account the biomechanic structure of the human spine, this device can provide support in two ways. Actuator A acts as an external muscle power generators to reduce the force requirement for the erector spinae muscles. As actuator B acts as a moment arm of the contractile force generated by actuator A, it will increase the effective amount of torque. The device can be worn directly on the body like normal clothing. Because there is no rigid exoskeleton frame structure, it is lightweight and user friendly. The system’s Inertial Measurement Unit (IMU), composed of accelerometer sensors and gyro sensors to measure the human motion signals, can monitor the angles of the human body in real-time mode. By measuring the EMG signal of the human erector spinae muscles, the assistance effectiveness of the proposed device has been proven through experiments.
Article
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Background A neutral spinal alignment is considered important during the execution of the deadlift exercise to decrease the risk of injury. Since male and female powerlifters experience pain in different parts of their backs, it is important to examine whether men and women differ in spinal alignment during the deadlift. Objectives The purpose of this study was to quantify the spinal alignment in the upper (thoracolumbar, T11-L2) and lower (lumbopelvic, L2-S2) lumbar spine during the deadlift exercise in male and female lifters. Secondary aims were to compare lumbar spine alignment during the deadlift to standing habitual posture, and determine whether male and female lifters differ in these aspects. Study Design Observational, Cross-sectional. Methods Twenty-four (14 men, 10 women) lifters performed three repetitions of the deadlift exercise using 70% of their respective one-repetition maximum. Spinal alignment and spinal range of motion were measured using three inertial measurement units placed on the thoracic, lumbar and sacral spine. Data from three different positions were analyzed; habitual posture in standing, and start and stop positions of the deadlift, i.e. bottom and finish position respectively. Results During the deadlift, spinal adjustments were evident in all three planes of movement. From standing habitual posture to the start position the lumbar lordosis decreased 13° in the upper and 20° in the lower lumbar spine. From start position to stop position the total range of motion in the sagittal plane was 11° in the upper and 22° in the lower lumbar spine. The decreased lumbar lordosis from standing habitual posture to the start position was significantly greater among men. Conclusions Men and women adjust their spinal alignment in all three planes of movement when performing a deadlift and men seem to make greater adjustments from their standing habitual posture to start position in the sagittal plane. Level of Evidence 3
Article
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The paper reviews research on the use of abdominal belts for industrial back injury prevention programmes. The evidence for biomechanical, physiological and psychophysical effects of belt use is presented, following a brief theoretical discussion. Although there is some laboratory evidence that abdominal belts protect the spine when lifting, the findings of field studies are equivocal. Previously injured workers seem to benefit the most both from 'back school' training combined with wearing abdominal belts at work. However, far form being the solution to industrial manual handling problems, abdominal belts have only a small part to play in comprehensive risk management programmes aimed at reducing back problems in the workplace.
Article
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The neutral zone is a region of intervertebral motion around the neutral posture where little resistance is offered by the passive spinal column. Several studies--in vitro cadaveric, in vivo animal, and mathematical simulations--have shown that the neutral zone is a parameter that correlates well with other parameters indicative of instability of the spinal system. It has been found to increase with injury, and possibly with degeneration, to decrease with muscle force increase across the spanned level, and also to decrease with instrumented spinal fixation. In most of these studies, the change in the neutral zone was found to be more sensitive than the change in the corresponding range of motion. The neutral zone appears to be a clinically important measure of spinal stability function. It may increase with injury to the spinal column or with weakness of the muscles, which in turn may result in spinal instability or a low-back problem. It may decrease, and may be brought within the physiological limits, by osteophyte formation, surgical fixation/fusion, and muscle strengthening. The spinal stabilizing system adjusts so that the neutral zone remains within certain physiological thresholds to avoid clinical instability.
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The use of back support belts by industrial workers has become common in recent years. The rationale for the use of these belts is based on the theory that they increase intra-abdominal pressure. Raised intra-abdominal pressure is believed to reduce compression forces on the spinal column and to assist the back extensor muscles in producing extension torque. The assistance of the belt is believed to protect the spine from injury. Thirty males and thirty females participated in this study which assessed the effect of two different back support belts (one synthetic and one leather) on isometric muscle-force production of individuals performing a static leg lift (SLL). A Latin Square double cross-over design was employed. Analysis of variance tests revealed that in males the use of the synthetic belt allowed for greater force production than a control trial, but no difference could be detected between the leather belt and either the synthetic belt or the control. In the female group, no difference in force production occurred across the three conditions. Implications and suggestions for further study are discussed.
Article
Intra-abdominal pressure (IAP) has been proposed as an important mechanism in manual lifting and breathing mechanics. Direct (invasive) measures of IAP have required the swallowing of a radio transducer or insertion of a pressure sensor into the rectum or down the oesophagus to the stomach. The purpose of this study was to investigate the relationship between a non-invasive method (EMG) and IAP. Several tasks involving abdominal muscle activation were performed to assess whether or not IAP played a common role in these tasks. IAP and EMG from rectus abdominis, the abdominal obliques, intercostals and erector spinae were measured. Peak IAP reached 340 mmHg (valsalva) for one subject but most values were less than 100 mmHg for tasks other than valsalva. The IAP and EMG data provide some insight into the role of IAP during the performance of specific tasks. Peak IAP within 60 ms of the onset of vigorous abdominal activation indicated the importance of a very rapid pressure response to abdominal muscle activation. The correlations between various muscle EMG time histories and IAP exceeded 0·80 for only two activities (i.e. r(2) = 0·82 between the intercostals and IAP during valsalva manoeuvres). These data suggest that no unifying hypothesis exists to explain the role of IAP for a wide variety of movement tasks; rather, the role of IAP is task specific.
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This study of 52 patients (27 men) with recent (< 18 months) or chronic (> 18 months) low back and unilateral radicular pain symptoms was undertaken to investigate whether wasting of the paraspinal muscle components is generalised or selective. During the patients' routine computed tomographic lumbar spinal scans a standardised transaxial view was obtained along the upper end-plate of the L4 vertebra, and the cross-sectional areas of the paraspinal muscles and their components, multifidus and erector spinae, estimated. Irrespective of whether the symptoms were recent or chronic, multifidus dimensions were significantly greater on the side ipsilateral to the radicular pain symptoms. The results indicate selective changes of multifidus in these patients and possibly reflect an adaptive response by this muscle, such as to an increased role in stabilising the lumbar spine in the face of overall paraspinal muscle atrophy.
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The classic book on human movement in biomechanics, newly updated. Widely used and referenced, David Winter's Biomechanics and Motor Control of Human Movement is a classic examination of techniques used to measure and analyze all body movements as mechanical systems, including such everyday movements as walking. It fills the gap in human movement science area where modern science and technology are integrated with anatomy, muscle physiology, and electromyography to assess and understand human movement. In light of the explosive growth of the field, this new edition updates and enhances the text with: Expanded coverage of 3D kinematics and kinetics. New materials on biomechanical movement synergies and signal processing, including auto and cross correlation, frequency analysis, analog and digital filtering, and ensemble averaging techniques. Presentation of a wide spectrum of measurement and analysis techniques. Updates to all existing chapters. Basic physical and physiological principles in capsule form for quick reference. An essential resource for researchers and student in kinesiology, bioengineering (rehabilitation engineering), physical education, ergonomics, and physical and occupational therapy, this text will also provide valuable to professionals in orthopedics, muscle physiology, and rehabilitation medicine. In response to many requests, the extensive numerical tables contained in Appendix A: "Kinematic, Kinetic, and Energy Data" can also be found at the following Web site: www.wiley.com/go/biomechanics.
Article
There are a variety of handling situations in industry for which it feels easier, given adequate training, to give the body movement and then transfer the resulting kinetic energy from the body to the load to be moved; and likewise to give the load horizontal movement and use that energy to raise it vertically. This is significant, bearing in mind the association between subjective estimates of stress and episodes of back pain. To the extent that these methods reduce the sense of effort they may also be less harmful, but this depends on the rates of increase in spinal stress, the magnitude of peak stress, and its duration. When these lifts are done quickly, the stress induced may not reach the threshold for sensation of discomfort, let alone injury. Knowledge of the mass of a load and the location of its center in relation to that of the body is not enough. These experiments have demonstrated major differences in the temporal pattern of stress while lifting weights well within some recommended maxima. They have also shown that measurements of the force at the hands and of the reaction between feet and floor constitute a method with a practical industrial application and one that in the laboratory is capable of providing the data essential to studies of the dynamic characteristics of the tissues of the trunk and vertebral column.
Article
Spinal injuries are a great cost to society and the afflicted individuals. It is well known that most spinal injuries are not bony fractures but rather soft tissue lesions falling in the 'subfailure' region. For the clinical diagnosis of spinal injuries, abnormal motion patterns under physiological loads are considered an important factor. The purpose of the present study was to determine the onset and progression of spinal injury, and compare the sensitivity of three motion parameters: neutral zone (NZ), elastic zone (EZ), and range of motion (ROM). Spinal injury was defined as a significant increase in any of the three motion parameters. A repeatable high-speed flexion-compression load vector was applied individually to six porcine cervical spine specimens. Several impacts of increasing severity were applied to each specimen. After each impact, flexion-extension motion was measured. Neutral zone was the residual deformation from the neutral position to the position under zero load at the start of the final load cycle. Elastic zone was the displacement from zero load to the maximum load on the final load cycle. Range of motion was the sum of the neutral and elastic zones. The first significant increase in motion was determined by the neutral zone parameter with few observable anatomic lesions on the specimens. This was the onset of spinal injury. The next significant motion increase was also determined by the neutral zone parameter. After this motion increase, termed the progression of injury, ligament ruptures were observed in some specimens. It was concluded that the neutral zone was the most sensitive motion parameter in defining the onset and progression of spinal injury.(ABSTRACT TRUNCATED AT 250 WORDS)