Sitting and low back disorders : an overview of the most commonly suggested harmful mechanisms

Abstract

Prolonged sitting is widely accepted as a risk factor for development and/or persistence of low back pain (LBP), with several etiological mechanisms being proposed so far. Cumulative intervertebral disc injuries were often mentioned in relation to LBP and sitting in older literature. Recent studies more frequently report on posterior lumbo-pelvic ligaments as the origin of pain, as those are under a tensile load when the spine is flexed. Such load can lead to (micro)trauma and changes in sensory-motor function, which increases the risk for overuse injuries of certain structures and even acute trauma. Overuse of facet joints or sacroiliac joint were not investigated to such extent. Another potential origin of LBP, noted also in several textbooks, are the myofascial trigger points. Prolonged sitting is associated with reduction in hip flexors flexibility, which induces unfavorable strain to lumbo-pelvic area and consequently increases the injury risk in lower back area.

Full text

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Received for publication February 1, 2018
Coll. Antropol. 42 (2018) 1: 1–XXX
Review
Introduction
Pain in lumbar and/or sacral spine and adjacent tis-
sues, often referred to as low back pain (LBP) is the most
common musculoskeletal symptom in general population
nowadays. Up to 84% people suffer from at least one case
of LPB in their lifetime 1. In half of those, the pain starts
to recur or becomes chronic 2. LBP is usually not a life-
threatening situation, however, it may have a significant
impact on individual’s life quality and represents a major
socioeconomic problem. The costs related to LBP are es-
timated to be between 0.8 and 2.1% of gross domestic
product in developed countries 3, with treatments repre-
senting only about one fifth of the total costs 4,5. The re-
maining is attributed to indirect costs, arising from de-
creased work efficiency, sick-leaves and early retirements
6. Even though only about 50% of the people suffering
from LPB actually seeks medical care 7, LPB is among the
most frequently treated conditions 8.
Up to date, several biomechanical, social and psycho-
logical risk factors for sustaining LBP have been recog-
nized. In individual cases, it is usually impossible to de-
termine the exact factors and mechanisms that led to the
occurrence of pain. Even with the modern imaging tech-
nology, an anatomical origin of pain is not found in 85%
of LPB cases 9,10. It is believed that muscles, ligaments
and fascia are the source of idiopathic/non-specific LPB11.
In general, the origin of pain may be in any type of tissue.
People are exposed to several different risk factors for
LBP throughout their lifetime. Prolonged sitting is among
the biomechanical risk factors that a big proportion of
population is exposed to. Sedentary time for average in-
dividual has been reported to be between 55 and 60% of
awake time 12-14, which equals to almost 10 hours per day.
For many, sitting is the most adopted posture throughout
the day. Recent technological advance is among the most
indisputable reasons behind that, as it led to more and
more workplaces which demand the employee to be seat-
ed. Another culprit for increased daily sitting time is pas-
sive motorized transport, while frequent usage of televi-
sion, computer and other digital information/
entertainment technology led to more sitting during lei-
sure time. It is common to sit at culture and sport events,
meetings and waiting rooms in different facilities as well.
It seems that modern society has created working and
living environment that encourages sitting on almost ev-
ery step.
Spinal structures are exposed to relatively low loads
during sitting, but these become highly unfavorable when
the exposure is prolonged – the resistance of the tissues to
Sitting and Low Back Disorders: An Overview of the
Most Commonly Suggested Harmful Mechanisms
Kaja Kastelic1, Žiga Kozinc2, Nejc Šarabon3
1Department of Health, Andrej Marusic Institute Research, University of Primorska, Koper, Slovenia
2Cycling Science Ltd., Kranj, Slovenia
3Univerza na Primorskem, Fakulteta za vede o zdravju, Izola, Slovenia
A B S T R A C T
Prolonged sitting is widely accepted as a risk factor for development and/or persistence of low back pain (LBP), with
several etiological mechanisms being proposed so far. Cumulative intervertebral disc injuries were often mentioned in rela-
tion to LBP and sitting in older literature. Recent studies more frequently report on posterior lumbo-pelvic ligaments as
the origin of pain, as those are under a tensile load when the spine is flexed. Such load can lead to (micro)trauma and
changes in sensory-motor function, which increases the risk for overuse injuries of certain structures and even acute trauma.
Overuse of facet joints or sacroiliac joint were not investigated to such extent. Another potential origin of LBP, noted also
in several textbooks, are the myofascial trigger points. Prolonged sitting is associated with reduction in hip flexors flexibil-
ity, which induces unfavorable strain to lumbo-pelvic area and consequently increases the injury risk in lower back area.
Key words: lower back pain, intervertebral discs, ligaments, back stability, ergonomics

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Kaja Kastelic et al.: Sitting and Low Back Disorders, Coll. Antropol. 42 (2018) 1: 1-xxx
imposed loads is reduced through time, if the exposure is
not interrupted 15. To maintain optimal health and func-
tion, tissues require a combination of different, mostly dy-
namic loads. However, static loads are present for the most
time during sitting, and are not optimally distributed be-
tween and within structures and tissues 16. The strain that
tissues are exposed to is highly dependent on the sitting
posture and morphological characteristics of individual's
structures 17.
It has been suggested that long-lasting mechanical
loads of otherwise healthy tissues can elicit different symp-
toms (pain among others), which appear only after pro-
longed uninterrupted static posture and are relived when
the position is changed 18. Most so called postural syn-
drome are in the lumbar spine and associated with pro-
longed sitting. Since the symptoms are transient in nature,
this syndrome has not been given much attention by the
healthcare professionals, although some authors stressed
out that it may be a precursor for more severe issues in the
future 19.
To form ergonomic recommendations for sedentary
people, it is crucial to know and understand the positions
of anatomical structures, muscle activity and passive tis-
sue loadings during different types of sitting. To our knowl-
edge, there is no prominent authoritative organization that
would publish detailed recommendations on ergonomics of
sitting. Recommendations between individual authors or
textbooks often differ substantially and are most com-
monly not equipped with scientific findings on which they
are based on. Additional confusion is caused by numerous
chairs and other sitting-related accessories available on
market, which are often designed based on false or out-of-
the-context conclusions, but are promoted to have ergo-
nomic characteristics.
Unfortunately, such false claims are more likely to
reach people than appropriate guidelines, supported by sci-
ence. This contributes to spreading of poor or even com-
pletely false knowledge and understanding on ergonomics
of sitting. Providing people with a high-quality recommen-
dations based on the latest scientific findings would con-
tribute to a more successful management of health issues
associated with prolonged sitting. Additionally, it is impor-
tant that healthcare professionals – who are responsible
for spreading the recommendations – are familiar with the
scientific background (i.e. knowledge and understating the
human body and the influences of sitting on it). Only then
will they be able to judge the both existing recommenda-
tions or products, and especially the innovations and nov-
elty on the field.
For this purpose, this narrative review article discuss-
es the most common sitting-related etiological mechanism
behind the development and/or persistence of LBP. We also
provide recommendations, following from the aforemen-
tioned findings. The influence of sitting on spinal struc-
tures and consequently on trunk neuromuscular function
is dependent upon the type and duration of sitting, and the
characteristic of the individual’s anatomical structures
(geometry, internal tissue properties, presence of other pa-
thologies, etc.). The mechanisms behind LBP development
can be divided into direct and indirect, acute and chronic,
reversible and irreversible, etc. For the clarity of the text,
we divided them based on the affected tissue type.
Effects of Sitting on Bony
and Cartilaginous Tissues
In older literature on injurious effects of sitting, inter-
vertebral discs were given the most attention. Because of
posterior pelvic tilt, the spine (particularly the lower seg-
ments) is in slightly flexed position even during upright
sitting posture (Fig. 1). During flexion, the load is un-
equally distributed between the anterior (increased com-
pressive load) and posterior (tensile load in case of full
flexion) part of the intervertebral disc 20. This combina-
tion forces the disc’s nucleus to move backwards (Fig. 2),
which contributes to the development of radial fissures in
posterior annulus fibrosus (outer fibrous ring) 21-23. The
injury starts with the lamellae of the annulus being dis-
torted. Radial fissures on inner lamellas are forming,
permitting the nucleus to enter the delaminated pockets.
The fissures are then spreading progressively radially
outwards. In time, the extrusion of the nucleus may occur,
resulting in an injury known as disc hernia, though this
process may take years to reach such severe state. Sev-
eral studies have reported an increased incidence of disc
hernia in sedentary population 24-26. The aforementioned
mechanism of disc behavior is supported by a landmark
study, during which the posterior shift of the nucleus was
observed in asymptomatic healthy subjects after only 10
minutes of unsupported relaxed upright sitting (the lum-
bar lordosis is somewhat reduced during such posture).
These changes were seen for L4/L5 and L5/S1 discs (5.7
mm and 6.9 mm on average, respectively), but not for
higher segments 27. These changes were even more pro-
nounced after slouched sitting, but were not significant
when a lumbar support was added during upright sitting.
Based on these findings, we recommend that neutral po-
sition of the spine is maintained during sitting, with prop-
erly designed lumbar support being among the accesso-
ries that can be of substantial help.
Fig. 1. Spinal curvatures and pelvic orientation are postural
dependent. Compared with relaxed standing (a), there is a
posterior pelvic tilt (e.g. diminished sacral slope (S.S.)) and a
decrease in lumbar lordosis in unsupported upright sitting (b).
The effect is even more pronounced in slouched sitting (c).

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Kaja Kastelic et al.: Sitting and Low Back Disorders, Coll. Antropol. 42 (2018) 1: 1-xxx
Another commonly discussed mechanism is a decrease
in disc hydration and/or nourishment as a consequence of
static compressive load during prolonged sitting. The nu-
tritional supply to the discs, mainly achieved by diffusion,
is hindered when disc is dehydrated 28. The metabolism of
the disc is additionally impaired due to the absence of
fluid transport within the disc during static loading 29. On
the contrary, water is intermittently forced in and out of
the disc during dynamic loads, which supports the efflux
of various macromolecules (waste products, growth fac-
tors, proteases, newly formed molecules of disc matrix,
etc.). Additionally, poorly nourished disc is more prone to
degeneration 30.
Reduced disc hydration shows as a decrease in disc
height and volume. When discs are in such state, the com-
pressive load is partially shifted to the annulus fibrosus
and facet joints, while the pressure within the disc is de-
creased 31. When the vertical component of compressive
force exerted on annulus fibrosus exceeds the horizontal
force, caused by inter-discal hydrostatic pressure, injuries
of interlaminar matrix could occur 20, which stimulates or
accelerates the degenerative processes. These injuries
could occur on the anterior aspect of the disc, where the
compression is the highest during spine flexion. One of the
ground-breaking studies reported that symmetrical disc
degeneration is more prevalent in those who spent most of
their worktime seated 32.
Fig. 2. Spinal exion is associated with higher compressive forces acting on the anterior part
of the intervertebral disc and tensile forces acting on the posterior ligaments of the spine.
Prolonged exposure to spinal exion has detrimental effects on spinal tissues. Several often
proposed harmful outcomes due to sustained spinal exion are shown.
ferences in disc height due to sitting exposures were with-
in the range of diurnal variations. It is not unusual for the
spine to be up to 26 mm shorter at evening compared to
morning time 38. During normal daily activities the spine
is exposed to spinal loading which causes a decrease in
discs height, mainly due to fluid outflow. Around 80% of
the spinal height difference is present as soon as three
hours after night sleep 39. We did not find any evidence
that sitting would lead to detrimental decrease in disc
height. It seems that disc dehydration during sitting is not
as significant as it is sometimes promoted to be and that
other postures may be just as harmful in this respect.
Relaxed sitting with reclined backrest causes lower loads
than relaxed standing 40. One study reported partial res-
toration of disc height with such type of sitting posture,
after it was reduced by standing work 37.
After prolonged sitting with flexed lumbar spine, it
takes a certain amount of time for discs to return to their
neutral shape. It has also been discussed that such revers-
ible deformation (flattened anterior part and posteriorly
shifted nucleus) changes the position of the mechanical
fulcrum 23, which temporarily decreases the resistance to
loading 15. The injury risk is increased particularly when
loads are applied on flexed spine. To restore the geometry
of the discs, most importantly the position of the nucleus,
few minutes of standing and/or walking is recommended.
Moreover, any substantial mechanical strain (e.g. lifting
The degree of dehydration and consequent drop in disc
height is dependent upon the magnitude, type and dura-
tion of the load. Higher and continuous loads lead to a
more substantial dehydration 33. Frequent subtle trunk
movements (like in sitting on a chair with movable seat
and/or backrest) are better for preserving disc hydration
compared to static posture 34,35, while vibrations exacer-
bate the dehydration 36. In line with the size of the load,
the decrease in disc height is most noticeable after
slouched sitting, followed by unsupported upright sitting
33 and lowest after sitting on a chair with reclined backrest
with good lumbar support 37. The reported degree of dif-
heavy loads), especially in spinal f lexion condition, should
be avoided immediately after prolonged sitting 15.
The potential influences of prolonged sitting on facet
joints, sacroiliac joint or pubic symphysis have not been
often discussed in the present literature. During slouched
sitting, the upper medial part of the superior facet joints
is believed to be under increased load 41,42. It was also re-
ported that cross-legged sitting slightly increases the
strain on the sacroiliac joint and pubic symphysis 43. How-
ever, short periods of such sitting posture are most likely
not harmful.

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Kaja Kastelic et al.: Sitting and Low Back Disorders, Coll. Antropol. 42 (2018) 1: 1-xxx
Effects of Sitting on Muscles
Low and relatively static muscle activity during sit-
ting can lead to discomfort and muscle pain 44. It was
shown that as soon as after 30 seconds of 2% of maximal
voluntary contraction (MVC), the oxygen transport in m.
erector spinae is significantly reduced 45. After 30 min-
utes of exposure, the signs of fatigue are already present
46. The level of muscle activity in healthy individuals dif-
fers between sitting types. Values seen during unsup-
ported upright sitting have been reported to be 4 to 12 %
of MVC for thoracic part of m. erector spinae, between 2
and 17% for m.multifidus, 10% for m. psoas major and
between 2 and 4% for abdominal muscles (m. trasnversus
abodminis, obliquus internus and obliquus externus) 47-49.
Prolonged sitting of such type is therefore to be avoided,
as it certainly leads to muscle discomfort. When sitting
on chairs without backrest or with a poorly designed
backrest, people will eventually adopt a slouched sitting
position, which require less muscle effort to maintain 48.
Namely, near full lumbar flexion, muscle silence occur.
The phenomenon is known as a flexion-relaxation phe-
nomenon 47 and it was proposed that muscle silence occur
when the major part of the counter torque to prevent
excessive flexion is generated by passive tissues – verte-
bral column and posterior spinal ligaments 50. The influ-
ence of sitting on those are discussed in previous and
further chapter, respectively.
A good lumbar support on the backrest enables the
user to sit upright, preserving the neutral lumbar lordo-
sis, while the muscle activity is relatively low. Muscle
activity does not exceed 2 % of MVC when sitting on an
office chair 51-53. However, even when such optimal pos-
ture is achieved, slight movements in all directions are
still advised. Another benefit of good back support is a
decrease of the load imposed to spinal structures (40 %
less compared to straight sitting without backrest) 54.
Further reductions can be achieved by tilting the back-
rest backward. It is important to stress that higher mus-
cle activity (and consequent higher force) leads to an
increase in compressive spinal load. Studies have shown
that office workers seldom exploit the benefits of using
the backrest – they adopt a slouched sitting posture even
on office chairs 53,55. People should be encouraged towards
using a backrest with good lumbar support.
Local painful spots, (sensitive to touch, contraction
and/or stretch) known as myofascial trigger points may
develop after prolonged static muscle activity, probably
because the alterations in local muscle metabolism 56.
They are often present in individuals suffering from
LBP, mainly in the muscles of lumbo-pelvic-hip complex.
Liu & Palmer 57 reported an increased prevalence of myo-
fascial trigger points in m. illiacus in students, sitting
>8h/day, compared to those sitting less. In office workers,
shoulder and upper back musculature is affected more
often 58. Preventive measures include using properly-
designed backrest and performing small movements of
the trunk during sitting. It was proposed that frequent
changes in sitting position (when loads are mitigating
from one tissue to another) have also overall important
role in avoiding specific spinal tissue overload 15.
Sufficient level of everyday physical activity is essen-
tial to preserve normal and/or healthy muscle status.
Sedentary lifestyle, combined with physical inactivity
leads to decline in muscle mass 59, alterations in muscle
fiber performance 60, muscle imbalances 61, deterioration
of trunk sensory-motor function 62 etc. Efficient muscle
system is important to maintain spinal health, as it pro-
vides stability and resistance to imposed loads, together
with passive (ligaments, discs, bones) and control (ner-
vous) systems 63. The incidence of LBP was shown to be
increased with poor strength and endurance of trunk
musculature 64, functional (agonist-antagonist) trunk
asymmetries 65 and limited hip flexion range of motion
66.
During sitting, hip, knee and usually the spine as
well, are in flexed position. Consequently, certain mus-
cles are in shortened position, while others are stretched,
making them prone to become shortened or over-
stretched, respectively. Muscle groups that may become
short with sitting include single-joint hip flexors (m.
psoas and illiacus) and sometimes two-joint hip exten-
sors (m. semitendinosus, semimembranosus and biceps
femoris), horizontal shoulder flexors (m. pectoralis ma-
jor) and neck extensors (m. trapezius, splenius, etc.).
Muscles that are significantly stretched during sitting
are single-joint hip extensors (m. gluteus maximus), cer-
tain external hip rotators (m. piriformis), trunk exten-
sors (m. erectors spinae) and scapular adductors (m. tra-
pezius, rhomboideus major and minor). In case of either
irregularities, dysfunction in movement patterns and
abnormalities in posture will begin to show. Features of
typical posture in sedentary people include accentuated
anterior pelvic tilt, pronounced lumbar lordosis, and pro-
tracted and sometimes even protruding scapulae. Lum-
bar lordosis may become less pronounced in individuals
who spent a majority of time in slouched sitting position,
due to the stretching of spinal passive tissues on poste-
rior site and shortening of two-joint hip extensors (i.e.
the hamstrings) 67.
Muscle asymmetries represent a significant risk fac-
tor for pain syndromes and injuries 61, as they lead to
unfavorable strain imposed to musculoskeletal system.
Non-optimal joint alignment and movement trajectory of
individual structures of the joint causes to uneven load
distribution within the joint surface 68-70. Active breaks,
including both resistance exercise and stretching, are
often recommended to perform during worktime. No
solid epidemiological evidence is present to support the
presumption that flexibility and/or posture are affected
by prolonged sitting. Individuals, spending a majority of
worktime in seated position should regularly engage in
physical activity to preserve their muscle function and
overall well-being.
Effects of Sitting on Ligaments and
Related Tissues
Sitting is usually accompanied with some degree of flex-
ion in lumbo-pelvic area. Consequently, tensile load is
place on posterior spinal ligaments 71, sacroiliac joint liga-

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Kaja Kastelic et al.: Sitting and Low Back Disorders, Coll. Antropol. 42 (2018) 1: 1-xxx
ments 72, as well as fascia 73 and facet joint capsules 74 in
this area. All of those tissues play an important role in
preserving spinal health. Ligaments in particular are es-
sential for ensuring spinal stability 75, not only mechani-
cally, but also as a source of numerous proprioceptors,
providing necessary sensory information to the nervous
system. Ligaments are also frequently the limiting factor
in maximal range of motion, and help to maintain the con-
tact between joint surfaces and proper arthrokinematics.
With prolonged tensile loads, both mechanical and sen-
sory properties of the ligaments are altered, due to the
(micro)trauma, which is often accompanied with inflam-
mation. Recovery is dependent upon the type, magnitude
and duration of the load, and does not proceed linearly
through time. It has been reported that only 40-60% of
mechanical stiffness is restored in the first hour after 20-
50 minutes of tensile strain, while up to 48 hours is need-
ed for full recovery. During this period, the neuromuscular
control is deteriorated, which shows as reduced kinesthet-
ic ability and alterations in reflex responses. While some
changes in the latter are believed to be compensatory –
protecting the joints from injuries which are more likely
to occur when the passive joint stiffness is reduced 76.
As with any other tissue, degradation is a common re-
sponse of the ligaments when no load is applied. However,
(micro)trauma may occur in case of overload, usually ac-
companied with pain and inflammation. When sufficient
unloading is not provided, the inflammation may become
chronic, leading to tissue degradation. As more than 24
hours is often needed for full recovery, microtrauma in-
curred in one day may not heal until the next, which would
lead to cumulative and more permanent ligament injury.
In conclusion, ligament vitality is determined by the vol-
ume and duration of the load and the duration of unload-
ing, with the optimal ratio between those still to be ex-
actly determined76.
Influences of various loadings on ligaments have most-
ly been explored with animal studies. Generalization to
humans is not possible – the underlying mechanisms are
probably very similar in nature, but the dose-response re-
lationship may be different. Viscoelastic creep, a reversible
mechanical deformation was shown on humans after the
exposure of lumbar flexion, resulting in increased range of
motion. In one study, flexion range of motion increased for
4.2° after only 10 minutes of sustaining maximal flexion
77, while 5,5° increase was observed after 20 minutes 78. A
hour-long exposure to 70% of maximal flexion was report-
ed to cause 2.3 ± 2.5° increase 79. Such increases of ligament
mechanical compliance results in decreased joint stiffness,
consequently impairing joint stability. About a half of the
stiffness is restored after a 2-minute rest 78. Another study
reported 1.6 ± 11.5 %, 7.7 ± 15.8 % and 24.5 ± 12.3 % de-
crease in passive stiffness after 2 minutes of exposure to
33, 66 and 100% of maximal lumbar flexion, respectively.
After 5-minute rest, all values were close to baseline 80. A
change in length-tension relationship after sustained lum-
bar flexion was also shown with the increase in angle at
which flexion-relaxation phenomenon occurs, however,
this angle was unchanged when accounted for the increase
in range of motion 81.
Additionally, alterations in neuromuscular control of
the trunk have been observed after relatively short expo-
sure to lumbar flexion. Latencies of reflexes responses of
certain back muscles were shown to be increased after one
hour of sustaining 70 % of maximal lumbar flexion 79.
Amplitudes of those responses also seem to increase after
prolonged flexion, in line with the percentage of range of
motion used 80,82. Longer latencies were attributed to re-
duction in sensibility of proprioceptors in viscoelastic tis-
sues and consequent decrease in afferent input. When
reflex responses are delayed, the spine is more exposed to
mechanical perturbations 83,84. Increased latencies were
also reported to be a risk factor for developing LBP 83.
Increase in the amplitude of the responses is probably a
compensatory mechanism to counteract the reduction in
passive stiffness. Deformation of viscoelastic tissues was
also shown to result in impaired kinesthetic ability. Five
minutes of slouched sitting was reported to cause a sig-
nificant increase (+3.92 ± 4.35°; p < 0.001) in trunk repo-
sition error 85. After short exposure to maximal lumbar
flexion, postural control during sitting on unstable seat is
also impaired, but is being normalized as soon as after 10
minutes of upright relaxed standing 86.
To sum up, even a short exposure to (partial) flexion
of lumbar part of the spine induces reversible viscoelastic
deformation of passive tissues, showing as increased lum-
bar flexion range of motion, decreased passive stiffness,
unfavorable alterations in reflex reactions of trunk mus-
culature, deteriorated kinesthetic ability and impaired
postural control in sitting position. These changes are
likely to increase LBP incidence. Even though the effects
of sitting on ligaments and trunk neuromuscular control
are poorly researched, we can be confident to recommend
avoiding slouched sitting positions and avoiding heavy
work immediately after sitting period. The resistance of
the spine and surrounding tissues is probably temporar-
ily reduced after sitting.
Fig. 3. Recommendations of sitting exceeds the frames of the
ofce chair-table context. Recommendations are listed as
follows: [a] maintaining the neutral spinal curves, [b] change
sitting positions frequently, [c] reduce the loads acting on the
body, [d] implement frequent bouts of standing/walking, [e]
incorporate short active breaks during prolonged sitting, [f]
follow the physical activity recommendations and [g] avoid
heavy labor immediately after prolonged sitting period.

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Kaja Kastelic et al.: Sitting and Low Back Disorders, Coll. Antropol. 42 (2018) 1: 1-xxx
Conclusion
Prolonged sitting is a widespread phenomenon of mod-
ern society. Unfortunately, it is associated with numerous
health risks, which also include pathologies and syn-
dromes of musculoskeletal system. Daily sitting time
should be cut to the minimum, and science-based recom-
mendations should be followed when sitting. The aim of
this article was to review currently available scientific
literature, which contribute to understanding of the influ-
ence of sitting on human body (particularly its locomotor
system) and are the basis for current recommendations on
sitting. We believe that professionals, as well as the inter-
ested general population, should know about the back-
ground of these recommendations. With increased aware-
ness and understanding on this field, the power of
‘’ergonomic’’ products, falsely promoted as healthy and/or
pain reliving, will also be reduced.
To conclude, the recommendations to improve sitting
ergonomics are briefly reviewed (Fig. 3). To avoid pain
syndromes and more serious injuries of musculoskeletal
system, it is recommended to: (1) maintain neutral spinal
curvature during sitting, (2) avoid prolonged static pos-
tures and (3) reduce the biomechanical loads. Addition-
ally, it is important to (4) implement frequent bouts of
standing or walking and to (5) incorporate short active
breaks into the worktime. Individuals spending a major-
ity of the day seated, should (6) follow the recommenda-
tions on physical activity engagement. After prolonged
sitting, (7) performing heavy labor should be avoided.
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SJEDENJE I BOL U DONJEM DIJELU LEĐA: PREGLED ETIOLOŠKIH MEHANIZAMA
SAŽETAK
Dugotrajno sjedenje se općenito smatra rizičnim faktorom za nastanak i/ili trajanje boli u donjem dijelu leđa (low
back pain, LBP) za koju je do sada utvrđeno više uzročnih mehanizama. U starijoj literature bol u donjem dijelu leđa i
sjedenje se obično povezuju s kumulativnim oštećenjima intervertebralnog diska. Novije studije sve češće uzrok boli
pripisuju posteriornim slabinsko-zdjeličnim ligamentima koji se nalaze pod vlačnim opterećenjem pri pognutoj kralježnici.
Ta kvo opter ećenj e može dove st i do (mik r o) traum a i promjena u osj et no-motor ičk oj fi n kc iji, št o povećava ri zik za prekom -
jerno tro šenje odr eđe nih struk tura i akutnu tr au mu . Pre komjer no trošenje fase tni h ili sa k roi lijak a lnih zglobova do sada
nije u većoj mjeri istraživano. Neki priručnici navode miofascijalne žarišne točke kao mogući uzrok boli. Dugotrajno
sjedenje je povezano sa smanjenom pokretljivošću pregibača kuka, što izaziva nepovoljan pritisak na slabinsko-zdjelično
podučje i povećava rizik oštećenja u slabinskom dijelu kralježnice.