Effect of prior instructions on preprogrammed reactions of trunk muscles in individuals with and without chronic low back pain
The late component of the stretch reflex occurring in humans within a 40 to 120 msec interval following a loading perturbation is qualified as a preprogrammed muscle reaction (PPR). The PPR size can be significantly modulated with prior instructions. These modifications are significantly influenc...
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irk-123456789-1482592019-02-18T01:25:25Z Effect of prior instructions on preprogrammed reactions of trunk muscles in individuals with and without chronic low back pain Shenoy, Sh. Balachander, H. Sandhu, J.S. The late component of the stretch reflex occurring in humans within a 40 to 120 msec interval following a loading perturbation is qualified as a preprogrammed muscle reaction (PPR). The PPR size can be significantly modulated with prior instructions. These modifications are significantly influenced by a number of factors, in particular by the presence of pain syndromes. The objective of our study was to compare the effect of prior instructions on the PPR amplitude in the trunk muscles in individuals with chronic low back pain (LBP) compared to healthy controls. LBP is a widespread syndrome, especially in athletes. Surface EMGs were recorded from superficial trunk muscles, rectus abdominis (RA) and erector spinae (ES), in athletes suffering from chronic LBP (n = 24) and asymptomatic (healthy) athletes (n = 25). Loading perturbations (induced by dropping a weight, application of 3 kg force, ≈ 30 N, to the outstretched hand from a 8 cm height) were introduced in standing at a known time with prior instructions to “let go” for the induced perturbation or to “resist” it. The root mean square (RMS) of the EMG amplitudes within the reaction duration were compared between the two groups. Statistically significant differences were obtained when the mean PPR EMG amplitudes were compared between the LBP and control groups for the above two task instructions; this was found for both examined muscles, RA and ES (P < 0.05). Therefore, individuals with chronic LBP exhibit poorly modulated PPR amplitudes according to prior task instructions. Changes in the networks controlling automatically regulated movements and excitability of the spinal pathways could be responsible for this specificity Пізній компонент стретч-рефлексу, що розвивається у людей в інтервалі 40–120 мс після пертурбації (навантаження), кваліфікується як м’язова препрограмована реакція (ППР). Величина ППР може істотно модулюватися під дією попередніх інструкцій. На ці модифікації істотно впливають численні фактори, зокрема наявність больових синдромів. Ціллю нашого дослідження було порівняння амплітуд ППР м’язів тулуба в осіб, що страждали на біль у попереку (БП), та здорових контрольних тестованих. БП є виключно широко розповсюдженим синдромом, особливо у спортсменів. Ми відводили ЕМГ від поверхневих м’язів тулуба – rectus abdominis (RA) та erectror spinae (ES) – у спортсменів із синдромом хронічного БП (n = 24) та спортсменів без такого розладу (здорових, n = 25). Силові пертурбації (прикладання ваги 3 кгс до витягнутої руки з висоти 8 см) вводились у певний момент до тестованого в положенні стоячи з попередніми інструкціями «не опиратися» введеному навантаженню або «опиратися» йому. Порівнювалися значення RMS для амплітуд ЕМГ у межах реакції, що спостерігалася в двох групах. Було виявлено, що середні амплітуди ППР-ЕМГ у групах БП та контролю при двох вказаних вище попередніх інструкціях вірогідно відрізнялися; це було властиве для обох обстежених м’язів – RA та ES (P < 0.05). Таким чином, особи, що страждають на хронічний БП, демонструють обмежену модуляцію амплітуди ППР відповідно до попередніх інструкцій. Зміни в нейронних мережах, що контролюють автоматично регульовані рухи та збудливість спінальних шляхів, вірогідно є відповідальними за таку специфіку. 2014 Article Effect of prior instructions on preprogrammed reactions of trunk muscles in individuals with and without chronic low back pain / Sh. Shenoy, H. Balachander, J.S. Sandhu // Нейрофизиология. — 2014. — Т. 46, № 1. — С. 70-76. — Бібліогр.: 42 назв. — англ. 0028-2561 http://dspace.nbuv.gov.ua/handle/123456789/148259 612.743+612.884 en Нейрофизиология Інститут фізіології ім. О.О. Богомольця НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| description |
The late component of the stretch reflex occurring in humans within a 40 to 120 msec interval
following a loading perturbation is qualified as a preprogrammed muscle reaction (PPR).
The PPR size can be significantly modulated with prior instructions. These modifications
are significantly influenced by a number of factors, in particular by the presence of pain
syndromes. The objective of our study was to compare the effect of prior instructions on
the PPR amplitude in the trunk muscles in individuals with chronic low back pain (LBP)
compared to healthy controls. LBP is a widespread syndrome, especially in athletes. Surface
EMGs were recorded from superficial trunk muscles, rectus abdominis (RA) and erector
spinae (ES), in athletes suffering from chronic LBP (n = 24) and asymptomatic (healthy)
athletes (n = 25). Loading perturbations (induced by dropping a weight, application of 3 kg
force, ≈ 30 N, to the outstretched hand from a 8 cm height) were introduced in standing at
a known time with prior instructions to “let go” for the induced perturbation or to “resist”
it. The root mean square (RMS) of the EMG amplitudes within the reaction duration were
compared between the two groups. Statistically significant differences were obtained when
the mean PPR EMG amplitudes were compared between the LBP and control groups for
the above two task instructions; this was found for both examined muscles, RA and ES
(P < 0.05). Therefore, individuals with chronic LBP exhibit poorly modulated PPR amplitudes
according to prior task instructions. Changes in the networks controlling automatically
regulated movements and excitability of the spinal pathways could be responsible for this
specificity |
| format |
Article |
| author |
Shenoy, Sh. Balachander, H. Sandhu, J.S. |
| spellingShingle |
Shenoy, Sh. Balachander, H. Sandhu, J.S. Effect of prior instructions on preprogrammed reactions of trunk muscles in individuals with and without chronic low back pain Нейрофизиология |
| author_facet |
Shenoy, Sh. Balachander, H. Sandhu, J.S. |
| author_sort |
Shenoy, Sh. |
| title |
Effect of prior instructions on preprogrammed reactions of trunk muscles in individuals with and without chronic low back pain |
| title_short |
Effect of prior instructions on preprogrammed reactions of trunk muscles in individuals with and without chronic low back pain |
| title_full |
Effect of prior instructions on preprogrammed reactions of trunk muscles in individuals with and without chronic low back pain |
| title_fullStr |
Effect of prior instructions on preprogrammed reactions of trunk muscles in individuals with and without chronic low back pain |
| title_full_unstemmed |
Effect of prior instructions on preprogrammed reactions of trunk muscles in individuals with and without chronic low back pain |
| title_sort |
effect of prior instructions on preprogrammed reactions of trunk muscles in individuals with and without chronic low back pain |
| publisher |
Інститут фізіології ім. О.О. Богомольця НАН України |
| publishDate |
2014 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/148259 |
| citation_txt |
Effect of prior instructions on preprogrammed reactions of trunk muscles in individuals with and without chronic low back pain / Sh. Shenoy, H. Balachander, J.S. Sandhu // Нейрофизиология. — 2014. — Т. 46, № 1. — С. 70-76. — Бібліогр.: 42 назв. — англ. |
| series |
Нейрофизиология |
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| first_indexed |
2025-07-12T18:59:26Z |
| last_indexed |
2025-07-12T18:59:26Z |
| _version_ |
1837468768440156160 |
| fulltext |
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 170
UDC 612.743+612.884
SH. SHENOY,1 H. BALACHANDER, 1 and J. S. SANDHU1
EFFECT OF PRIOR INSTRUCTIONS ON PREPROGRAMMED REACTIONS
OF TRUNK MUSCLES IN INDIVIDUALS WITH AND WITHOUT
CHRONIC LOW BACK PAIN
Received February 18, 2013.
The late component of the stretch reflex occurring in humans within a 40 to 120 msec interval
following a loading perturbation is qualified as a preprogrammed muscle reaction (PPR).
The PPR size can be significantly modulated with prior instructions. These modifications
are significantly influenced by a number of factors, in particular by the presence of pain
syndromes. The objective of our study was to compare the effect of prior instructions on
the PPR amplitude in the trunk muscles in individuals with chronic low back pain (LBP)
compared to healthy controls. LBP is a widespread syndrome, especially in athletes. Surface
EMGs were recorded from superficial trunk muscles, rectus abdominis (RA) and erector
spinae (ES), in athletes suffering from chronic LBP (n = 24) and asymptomatic (healthy)
athletes (n = 25). Loading perturbations (induced by dropping a weight, application of 3 kg
force, ≈ 30 N, to the outstretched hand from a 8 cm height) were introduced in standing at
a known time with prior instructions to “let go” for the induced perturbation or to “resist”
it. The root mean square (RMS) of the EMG amplitudes within the reaction duration were
compared between the two groups. Statistically significant differences were obtained when
the mean PPR EMG amplitudes were compared between the LBP and control groups for
the above two task instructions; this was found for both examined muscles, RA and ES
(P < 0.05). Therefore, individuals with chronic LBP exhibit poorly modulated PPR amplitudes
according to prior task instructions. Changes in the networks controlling automatically
regulated movements and excitability of the spinal pathways could be responsible for this
specificity.
Keywords: preprogrammed muscle reactions, chronic low back pain, prior instructions,
electromyography, trunk muscles.
1 Faculty of Sports Medicine and Physiotherapy, Guru Nanak Dev University,
Punjab, India
Correspondence should be addressed to:
Sh. Shenoy (e-mail: shwet1999@yahoo.com).
H. Balachander (e-mail: harini.bee@gmail.com).
J. S. Sandhu (e-mail: jssandhudr@gmail.com).
INTRODUCTION
The spinal stretch reflex in humans is well known to
include at least two components, a classic short-laten-
cy response (M1), occurring with an about 40 mseс de-
lay, and a more complex long-latency response (M2),
occurring with a delay of 40-50 to 120 msec [1], also
known as a preprogrammed muscle reaction (PPR).
Although the time characteristics of the latter vary
from muscle to muscle, it occurs in both the shortened
and stretched muscles in response to perturbation in
their length or loading [2].
It was proposed that the origin of the long-latency
M2 response involves transcortical projection
pathways [3, 4]. This makes the understanding of
the long-latency response more complex than that
of a simple stretch reflex. The M2 has been said to
be task-dependent [5-7] and affected by various
factors such as velocity, duration of perturbation [8],
and pain [9]. The long-latency reflex and voluntary
muscle responses exhibit a high functional similarity,
probably because of a shared neural substrate [10, 11].
This explains its coordination between feedback gain
and internal models during complex motor tasks [9].
Long-latency muscle responses function to counteract
perturbations, to correct the direction of movement,
and to regain stability [11, 12].
Modification in the size of M2 related to prior
instructions has been observed [1, 13, 14]. When a
command “let go” is given, so as not to “resist” the
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 1 71
EFFECT OF PRIOR INSTRUCTIONS ON PREPROGRAMMED MUSCLE REACTIONS
perturbation, the individual effectively suppresses
realization of the long-latency response and decreases
its amplitude [15]. However, this aspect is still under
debate. Rothwell [16] and Capaday [17] concluded
that the nature of the voluntary movement, and not of
the reflex response, is influenced by prior instructions.
Chronic low back pain (LBP) is a common
problem faced by vast human populations. Here, we
do not discuss in detail questions on the etiology
of this syndrome, as they are out of the topic of
our communication. About 30% of athletes suffer
from chronic LBP due to the repeated flexion and
hyperextension demands sports game [18, 19].
Abnormal functioning of the motorneuronal loop
causes reduced or absent firing of the trunk muscles
[20, 21] and a delayed muscle reflex response [5] to
trunk loading in individuals with chronic LBP.
Healthy individuals depend largely on neuromotor
responses to maintain stability in dynamic loading
situations, as no change in muscle recruitment is
observed with anticipation [22]. Altered postural and
neuromotor control in individuals with chronic LBP
could blunt their stability and predispose them to
recurrent injury.
Although the long-latency response of muscles
of the hand largely involves the transcortical loop,
postural muscles are often integrated with automated
motor programs and mostly mediated by other spinal
pathways [23]. To our knowledge, no study has been
done to examine the effect of prior instructions on the
long-latency response of trunk muscles. If the subject’s
intent could alter the long-latency response, it could
prove beneficial in the rehabilitation of individuals
with chronic LBP.
Hence, the purpose of our study was to examine the
effect of a prior instruction on the long-latency reflex
response of the trunk muscles (rectus abdominis, RA,
and erector spinae, ES) during sudden trunk loading
tasks in individuals with and without chronic LBP.
METHODS
Subjects. Athletes with nonspecific LBP (n = 24,
16 men and 8 women) were selected across various
sporting bodies in and around Amritsar, Punjab, India.
Athletes with chronic LBP having nonradiating pain
for at least three months were included in the study.
The presence of the mentioned syndrome was well
documented by medical examination. The athletes
were currently involved in the sport and had been
playing for at least five days a week for the last three
years. Cases with recent history of traumatic injury to
back and lower limbs, history of CNS impairments,
abdominal or back surgery, and recent history of
systemic illnesses were excluded.
The control group consisted of athletes at a similar
sporting level, with no history of LBP or injury
(n = 25, 17 men and 8 women).
EMG Recording. Surface EMG data were collected
using a Noraxon-MyoS 1200 set manufactured by
Noraxon (USA). A Logitech Webcam videocamera
was used in conjunction. Electromyograms were
recorded from the superficial trunk muscles, m.
rectus abdominis (RA) and m. erector spinae (ES),
using bipolar disposable surface electrodes. Prior to
the placement of the electrodes, the area was rubbed
clean using an alcohol swab. For the RA, recording
electrodes were placed parallel to the muscle, 3 cm
apart and about 2 cm lateral to the umbilicus. For the
ES, the electrodes were placed parallel to the spine,
at the level of L3 and L4, 2 cm apart, over the muscle
mass [24]. A reference electrode was placed on the
lateral aspect of the trunk.
The electromyograph machine was set at a continu-
ous recording mode, with sampling frequency 103 sec–1,
sensitivity 100 μV/div., filter setting 20 Hz–3 kHz, and
sweep rate 50 msec/div [21].
Testing Procedure. A detailed history of sporting
activity and assessment of LBP was taken before test-
ing. Subjects filled the Visual Analogue Scale and Ro-
land Morris Disability Questionnaire to assess the se-
verity of pain. Individuals who did not fit the criteria
were immediately excluded from the study.
The subjects were made to stand with the pelvis im-
mobilized by support posteriorly and strapping anteri-
orly, to restrain any unnecessary movement [25, 26].
A cushioned weight of 3 kg force (about 30 N) was
made to drop from predetermined height of 8 cm onto
the subject’s outstretched hand. The muscle reaction
to this sudden anterior movement at the spine was re-
corded.
The subjects were informed of the testing proce-
dure. The weight used for the trials for perturbation
was adopted from a previous study by Ramprasad [21].
A prior command of “let go” or “resist” for the trunk
muscles was explained and taught to the subject. The
subject was made to stand relaxed with his/her arms
outstretched. The exact time of drop was indicated
to the subject by a metronome, and the EMG was re-
corded. Three trials were taken for each task, and a
10-min-long time interval between trials was given to
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 172
SH. SHENOY, H. BALACHANDER, and J. S. SANDHU
recuperate.
EMG Data Processing. For both muscle groups, the
data computed were the mean window length of M2-
M3 and the mean RMS amplitude of the M2 response.
To determine the RMS amplitude and window
length, markers were introduced at the onset of M2,
where the response size was 60% higher than M1 [27],
and polyphasic M2-M3 waves were present within a
40 to 120 msec window. Raw EMGs were rectified and
smoothed before analyzing. The mean RMS values for
all three tasks and for RA and ES EMGs were calcu-
lated for both LBP and control groups.
Statistical Analysis. IBM SPSS Statistics (Version
20.0) was used for the analysis. The significance level
for intergroup comparisons was set at 0.05. A general
linear model and multivariate analysis were used to
compare the mean PPR amplitudes between the LBA
and control groups.
RESULTS
The mean RMSs of the EMG amplitudes for two
muscles, RA and ES, were calculated. For the “let go”
command, the mean RMS of the RA EMG amplitude
was 16.68 ± 3.4 for the LBA group and 31.77 ± 11.77
for the control group. For the command “resist,” the
mean values were 15.78 ± 3.6 and 35.38 ± 15.08 for
the LBP and control groups, respectively.
For the “let go” task, the mean RMS of the ES
amplitude was 59.40 ± 15.80 for the LBP group and
61.46 ± 14.42 for the control group. A mean value of
30.82 ± 13.26 was obtained for the “resist” command
in the LBP subjects, while it was 64.75 ± 10.16 for the
control group.
Statistical analysis was done using a general linear
model and multivariate analysis. Further multiple
comparison by the post-hoc Tukey test was done
to compare the mean difference between groups.
The results showed the existence of a statistically
significant difference between LBP and control groups
for both commands in the RA muscle group. A mean
difference of 15.76 (P = 0.05*) was found between
the “let go” amplitude in the LBP and control groups,
while a mean difference of 20.46 (P = 0.05*) was
found between the data related to the “resist” command
in the LBP and control groups for the RA muscle
group (Table 2). In the ES, no significant difference
was obtained for the command “let go,” while “resist”
showed a significant mean difference of 38.18
(P = 0.05*) between the LBA and control groups.
Intragroup comparisons for both commands
resulted in no significant difference except in the ES
case (graphs 1 and 2). In the LBA group, the mean
difference of EMG amplitudes between the commands
“let go” and “resist” was statistically significant with a
mean difference of 28.58 (P = 0.05*). All these values
were significant at P < 0.005.
0
1
1
1
1
2
2
2
2
0
LBP LBPContr. Contr.
10
20
20
40
30
60
40
F i g. 1. Mean values of the RMS of the PPR amplitude of the restus
abdominis muscles at instructions of “let go” (1) and “resist” (2) in
the LBP and control groups.
Р и с. 1. Середні значення RMS амплітуди препрограмованих
реакцій m. rectus abdominis при інструкціях «не опиратися» (1)
та «опиратися» (2) пертурбації в досліджених групах.
F i g. 2. Mean values of the RMS of the PPR amplitude of the
erector spinae muscles at instructions of “let go” (1) and “resist”
(2) in the LBP and control groups.
Р и с. 2. Середні значення RMS амплітуди препрограмованих
реакцій m. erector spinae при інструкціях «не опиратися» (1) та
«опиратися» (2) пертурбації в досліджених групах.
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 1 73
EFFECT OF PRIOR INSTRUCTIONS ON PREPROGRAMMED MUSCLE REACTIONS
DISCUSSION
The purpose of our study was to determine the effect
of prior instructions on the PPR amplitudes following
trunk loading perturbations in individuals with and
without chronic LBP. The mean PPR amplitudes of
RA and ES EMGs with prior instruction to “let go”
and “resist” were compared. For the RA, the mean
amplitude for “let go” was approximately 48% lower
in the LBP group compared to the control, and it
was 57% lower for the “resist” command. For the
ES muscle, no difference was found under “let go”
conditions, but “resist” showed the 53% lower PPR
EMG amplitude in LBP subjects when compared to
controls. A previous study [21] demonstrated a lower
PPR EMG amplitude in individuals with chronic LBP
compared to controls. However, the results of our
study show that individuals with chronic LBP poorly
modulate PPR EMG responses upon prior instructions.
Significantly lower EMG amplitudes, especially in the
ES, were obtained in individuals with chronic LBP
who intended to “resist” the induced perturbation
when compared to an intent to “let go.”
Prior-task instructions exert noticeable effects on
the PPR. Effective suppression of the M2 response
upon intent to “let go” has been observed in several
Table 1. Anthropometric data and health state of individuals of the LBA and control groups.
Таблиця 1. Антропометричні дані та стан здоров’я в осіб досліджених груп.
Characteristics
Groups
LBA (n = 24) Control (n = 25)
Age, years 24.26 ± 4.7 25.13 ± 5.05
Height, cm 174.42 ± 11.36 172.23 ± 9.63
Body mass, kg 69.76 ± 8.43 67.32 ± 7.84
VAS, cm 3.24 ± 1.62 0.0
Lifetime highest VAS 7.2 ± 2.19 0.0
RMDQ 4.20 ± 3.18 0.0
Activity reduction, % 8.96 ± 2.53 0.0
Footnotes: means ± s.d. are shown, VAS is Visual Analogue Scale, and RMDQ is Roland Morris Disability Questionnaire
Table 2. Results of post hoc Tukey testing of the variables in the LBA and control groups.
Таблиця 2. Результати post-hoc-тестування експериментальних даних, за Тьюкі, у двох досліджених групах.
Results mean difference s.d. significance (p)
EMGs recorded from the m. rectus abdominis
LBA ‘Let Go’ x LBA ‘Resist’ .9040 2.72 0.987
Control ‘Let Go’ x Control
‘Resist’ 3.76 2.72 0.516
LBA ‘Let Go’ x Control ‘Let Go’ 5.76 2.72 0.05*
LBA ‘Resist’ x Control ‘Resist’ 20.46 2.72 0.05*
EMGs recorded from the m. erector spinae
LBA ‘Let Go’ x LBA ‘Resist’ 28.58 5.11 0.05*
Control ‘Let Go’ x Control
‘Resist’ 4.88 5.11 0.775
LBA ‘Let Go’ x Control ‘Let Go’ 2.72 5.11 0.951
LBA ‘Resist’ x Control ‘Resist’ 36.18 5.11 0.05*
Footnote: * Significant at P<0.005
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 174
SH. SHENOY, H. BALACHANDER, and J. S. SANDHU
previous studies [1, 13, 28]. This makes the PPR relate
very closely to voluntary responses [9, 12], and the
primary motor cortex modulates the PPR just like
these responses [29, 30]. But this has been a topic of
debate ever since, as several studies have shown no
significant difference in the PPR amplitude following
prior instructions [16, 17], especially in small muscles
of the hand (such as m. flexor pollicis longus).
Postural muscles (in our case, the RA and ES) differ
from the distal limb muscles functionally, as they
rely more on automatically regulated movements.
Studies provide evidence that, unlike muscles of the
hand whose functions are effectively controlled by the
transcortical pathways, postural trunk muscles are to
a greater extent influenced by the spinal (segmental)
pathways [3, 4, 23, 31]. A higher PPR amplitude in the
RA and ES muscles in our study in normal individuals
with a prior instruction to resist the perturbation could
be due to an enhanced cortico-spinal excitability [32,
33] that is likely to arise from an overlap of multiple
neural responses [34].
In the case of individuals with chronic LBP, two
differences are evident: (i) The RA exhibits a lower
mean PPR amplitude for both commands, i.e., “let go”
and “resist,” (ii) In the ES, individuals presented better
modulation for the intent to “let go” than to “resist.”
The “resist”-related amplitude was significantly lower
for these individuals (Table 2).
Individuals with chronic LBP exhibit a few
noticeable neuromotor changes, in particular, in
proprioception, a reduced firing rate of motor units,
and poor muscle stabilization [20, 35, 36]. This
results in lower and even zero PPR amplitudes [21].
However, the reduced ES PPR amplitude on the intent
to “resist” can be determined by chronic pain. The
site of pain origin located rather close to the ES could
induce a lower cortico-spinal excitability [37]. As
was discussed previously, the intent and its effect on
the amplitude of the PPR can vary due to changes in
the supraspinal (cortico-spinal) excitability. Hence,
chronic pain reducing the excitability of this system
in individuals with chronic LBP can be responsible for
difficulties of intended modulation of PPR.
Fatigue can also be a reason for reduced cortico-
spinal excitability [38, 39]. Individuals suffering from
chronic LBP often experience abnormally intense
fatigue of postural muscles and poor postural control
provided by trunk muscles [40, 41]. Long-lasting
disturbances in the neuromotor system can induce
plastic (both structural and functional) changes in the
cortical networks [42]. A possibility for changes in the
representation of the trunk muscles in the motor cortex
under the above conditions has been hypothesized
[43].
Thus, mild modulation of the PPR amplitude upon
receiving prior instructions is obvious, especially
in the ES, in individuals with chronic LBP. These
changes could predispose LBP individuals to long-
term manifestation of this syndrome. At the same time,
the dynamic nature of the respective neural pathways
points to an effective neuromotor exercise program
that can help earlier recovery in these cases. The
cause of changes in the PPR amplitude upon intent
and perturbation should be qualified as multifactorial.
It is likely that training-related modulation of cortico-
spinal activation is one of the ways to improve the
state of health of the respective contingent. Only few
data are available in literature to help interpret the
above-described results, and further studies may be
required to support these findings.
The interpretation of our findings is limited by
the “cross-sectional” design of the study. As was
mentioned above, we did not elucidate precise
medical reasons for the LBP occurrence. The way of
stimulation (a weight dropped to induce perturbations)
was manual. Hence, some variations in the perturbation
force cannot be ruled out, although the weight and
the height of drop were standardized. The subjects
were well matched and, irrespective of their sport
specialization, showed similar EMG amplitudes to
the action of perturbation in the chronic LBP group,
despite the fact that they were chosen from various
sports (soccer, hockey, handball, or basketball).
Therefore, poor modulation of the PPR amplitude
related to the type of prior instructions is evident
in individuals with chronic LBP. Subjects with
this syndrome demonstrate significantly lower
perturbation-related EMG amplitudes on the intent
to “resist” than to “let go,” especially in the ES
muscle. The reason for this may be multifactorial,
but the effect of reduced cortico-spinal excitability
on prior task instructions with respect to the RA
and ES muscles in individuals with chronic LBP
can be an important reason, determining changes in
automatically regulated (patterned) movements and
reduced trunk muscle function.
All participants gave their informed consent before
participation, and the testing procedures were explained to
them. The study was approved by the Ethics Committee,
Faculty of Sports Medicine and Physiotherapy, Guru Nanak Dev
University, Amritsar, India.
NEUROPHYSIOLOGY / НЕЙРОФИЗИОЛОГИЯ.—2014.—T. 46, № 1 75
EFFECT OF PRIOR INSTRUCTIONS ON PREPROGRAMMED MUSCLE REACTIONS
The authors, Sh. Shenoy, H. Balachander, and J. S. Sandhu,
have no conflict of interests.
Ш. Шеной1, Х. Балачандер1, Дж. С. Сандху1
ВПЛИВ ПОПЕРЕДНІХ ІНСТРУКЦІЙ НА
ПРЕПРОГРАМОВАНІ РЕАКЦІЇ М’ЯЗІВ ТУЛУБА В ОСІБ
З ХРОНІЧНИМ БОЛЕМ У ПОПЕРЕКУ ТА БЕЗ ТАКОГО
СИНДРОМУ
1 Університет Гуру Нанак Дев, Амрітсар, Пенджаб (Індія)
Р е з ю м е
Пізній компонент стретч-рефлексу, що розвивається у лю-
дей в інтервалі 40–120 мс після пертурбації (навантажен-
ня), кваліфікується як м’язова препрограмована реакція
(ППР). Величина ППР може істотно модулюватися під дією
попередніх інструкцій. На ці модифікації істотно вплива-
ють численні фактори, зокрема наявність больових синдро-
мів. Ціллю нашого дослідження було порівняння амплітуд
ППР м’язів тулуба в осіб, що страждали на біль у попереку
(БП), та здорових контрольних тестованих. БП є виключ-
но широко розповсюдженим синдромом, особливо у спортс-
менів. Ми відводили ЕМГ від поверхневих м’язів тулуба –
rectus abdominis (RA) та erectror spinae (ES) – у спортс-
менів із синдромом хронічного БП (n = 24) та спортсме-
нів без такого розладу (здорових, n = 25). Силові пертур-
бації (прикладання ваги 3 кгс до витягнутої руки з висоти
8 см) вводились у певний момент до тестованого в поло-
женні стоячи з попередніми інструкціями «не опиратися»
введеному навантаженню або «опиратися» йому. Порівню-
валися значення RMS для амплітуд ЕМГ у межах реакції,
що спостерігалася в двох групах. Було виявлено, що серед-
ні амплітуди ППР-ЕМГ у групах БП та контролю при двох
вказаних вище попередніх інструкціях вірогідно відрізняли-
ся; це було властиве для обох обстежених м’язів – RA та ES
(P < 0.05). Таким чином, особи, що страждають на хроніч-
ний БП, демонструють обмежену модуляцію амплітуди ППР
відповідно до попередніх інструкцій. Зміни в нейронних ме-
режах, що контролюють автоматично регульовані рухи та
збудливість спінальних шляхів, вірогідно є відповідальни-
ми за таку специфіку.
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