Influence of Various Types of Office Desk Chair for Dynamizing the Operation Assessed by Raster Stereography

Abstract

Featured Application
This article describes the use of Raster Stereography in the monitoring of the changes in spinal biomechanics. The measurement results show the effect of sitting on different types of office chair, on changes in the curvature of the spine.

Abstract
The current development trend of the operational activities indicates an increase in occupations which last for a few generations and whose primary position is the activity in the sitting position. This trend is directly connected with the technological progress and development of the society within Industry 4.0. However, the workplaces intended for sitting occupations that are designed according to the current standards are unsuitable from several perspectives. The long-term sitting activities at most actual workplaces cause an accumulation of the static load. For this reason, the article deals with dynamizing the activities in the sitting position. The presented research is based on utilizing the knowledge of the sitting posture dynamics and on the information acquired through diagnostics based on the Raster Stereography as an innovative method based on modelling a natural human spin. The article brings the first research results, which points out the fact that probably not all types of dynamic sitting that are nowadays preferred are suitable for long-term working.

Full text

applied
sciences
Article
Influence of Various Types of Office Desk Chair for
Dynamizing the Operation Assessed by Raster Stereography
L’uboslav Dulina 1, Arkadiusz Gola 2, * , Martin Gašo 1, Blanka Horváthová1, Eleonóra Bigošová1,
Miroslava Barbušová1, Dariusz Plinta 3and JiˇríKyncl 4


Citation: Dulina, L’.; Gola, A.; Gašo,
M.; Horváthová, B.; Bigošová, E.;
Barbušová, M.; Plinta, D.; Kyncl, J.
Influence of Various Types of Office
Desk Chair for Dynamizing the
Operation Assessed by Raster
Stereography. Appl. Sci. 2021,11, 4910.
https://doi.org/10.3390/
app11114910
Academic Editor: Alessandro Naddeo
Received: 8 May 2021
Accepted: 24 May 2021
Published: 26 May 2021
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1
Department of Industrial Engineering, Faculty of Mechanical Engineering, University of Žilina, Univerzitná
8215/1, 010 26 Žilina, Slovakia; luboslav.dulina@fstroj.uniza.sk (L’.D.); martin.gaso@fstroj.uniza.sk (M.G.);
blanka.horvathova@fstroj.uniza.sk (B.H.); eleonora.bigosova@fstroj.uniza.sk (E.B.);
miroslava.barbusova@fstroj.uniza.sk (M.B.)
2Department of Production Computerization and Robotization, Faculty of Mechanical Engineering, Lublin
University of Technology, ul. Nadbystrzycka 36, 20-618 Lublin, Poland
3Department of Production Engineering, Faculty of Mechanical Engineering and Computer Science,
University of Bielsko-Biala, ul. Willowa 2, 43-309 Bielsko-Biała, Poland; dplinta@ath.bielsko.pl
4Department of Machining, Process Planning and Metrology, Faculty of Mechanical Engineering, Czech
Technical University in Prague, Jugoslávských partyzán˚u 1580/3, 160 00 Prague, Czech Republic;
jiri.kyncl@fs.cvut.cz
*Correspondence: a.gola@pollub.pl; Tel.: +48-81-538-45-35
Featured Application: This article describes the use of Raster Stereography in the monitoring
of the changes in spinal biomechanics. The measurement results show the effect of sitting on
different types of office chair, on changes in the curvature of the spine.
Abstract:
The current development trend of the operational activities indicates an increase in occu-
pations which last for a few generations and whose primary position is the activity in the sitting
position. This trend is directly connected with the technological progress and development of the
society within Industry 4.0. However, the workplaces intended for sitting occupations that are
designed according to the current standards are unsuitable from several perspectives. The long-term
sitting activities at most actual workplaces cause an accumulation of the static load. For this reason,
the article deals with dynamizing the activities in the sitting position. The presented research is based
on utilizing the knowledge of the sitting posture dynamics and on the information acquired through
diagnostics based on the Raster Stereography as an innovative method based on modelling a natural
human spin. The article brings the first research results, which points out the fact that probably not
all types of dynamic sitting that are nowadays preferred are suitable for long-term working.
Keywords:
office ergonomics; new technology; Raster Stereography; dynamizing of sitting position
1. Introduction
Moretti et al. recently published the study, which concentrated on observing the
influence of the home office on productivity, work stress, and musculoskeletal problems
in the case of employees working from home. Moreover, the acceleration of production,
development of technologies or optimization of the workplace, and manufacturing pro-
cesses force employees to carry out activities with minimal movement (see Figure 1). In the
case of manufacturing activities, it is the strictly defined optimal working spaces and non-
manufacturing activities which require the sitting working position. The modern human
population ceases moving during working but also non-working times. The consequences
of such a lifestyle have been well-known for several decades—obesity, cardiovascular
illnesses or body posture disorders that indirectly or principally affect the population
health [
1
–
4
]. Due to the above negative impact on a professional and personal level, it is
required to study the dynamization of the work.
Appl. Sci. 2021,11, 4910. https://doi.org/10.3390/app11114910 https://www.mdpi.com/journal/applsci

Appl. Sci. 2021,11, 4910 2 of 12
Appl. Sci. 2021, 11, 4910 2 of 12
vascular illnesses or body posture disorders that indirectly or principally affect the popu-
lation health [1–4]. Due to the above negative impact on a professional and personal level,
it is required to study the dynamization of the work.
Figure 1. Transformation of working activities—consequences [4].
Much motion and physical loads during operation (e.g., handling with loads) are
limited by national legislation, EU standards, ergonomic principles, and the principles of
designing workplaces in the framework of Industrial Engineering. However, currently,
things that affect manufacturing system performance efficiency are being changed [5,6].
If people carry out a minimal number of movements and all working devices are
within their reach, they are maximally productive from the point of view of the movement
economy and thus for a continuous production flow. The number of movements is pro-
portional to the consumed time, and the consumed time is the entrance to work produc-
tivity. The productivity of work is one of the production effectiveness indicators that every
industrial engineer wants to improve. On the one hand, reducing the amount and extent
of the movements increases the productivity of work, but on the other hand, it reduces
the employees’ movements. In the framework of the working activity, the same muscle
groups are involved, leading to a long-term unidirectional load. At the same time, several
muscle groups remain in a static position. The long-term work in the sitting position is a
characteristic example [5–7].
Dynamisation of Working Postures
The number of occupations requiring a sitting position is growing in all lines of busi-
ness due to technological progress (for example, programmers, dispatchers, designers).
Therefore, it is necessary to pay increased attention to dynamizing working postures in
office workplaces. This dynamization can minimize the health problems caused by accu-
mulating the static load. In this way, we eliminate the development of fatigue and health
problems [8,9].
There are three ways to operate dynamically during work in the sitting position:
1. A regular change in the main working position—changing the sitting position to the
standing one. To ensure the continuity of the working activity, it is necessary to adapt
the workplace in such a way that the employee will be able to carry out the operation
also in the standing position. Such a change requires height-adjustable desks, and it
is also necessary to enlarge the workplace’s floor area.
Figure 1. Transformation of working activities—consequences [4].
Much motion and physical loads during operation (e.g., handling with loads) are
limited by national legislation, EU standards, ergonomic principles, and the principles of
designing workplaces in the framework of Industrial Engineering. However, currently,
things that affect manufacturing system performance efficiency are being changed [5,6].
If people carry out a minimal number of movements and all working devices are
within their reach, they are maximally productive from the point of view of the move-
ment economy and thus for a continuous production flow. The number of movements
is proportional to the consumed time, and the consumed time is the entrance to work
productivity. The productivity of work is one of the production effectiveness indicators
that every industrial engineer wants to improve. On the one hand, reducing the amount
and extent of the movements increases the productivity of work, but on the other hand, it
reduces the employees’ movements. In the framework of the working activity, the same
muscle groups are involved, leading to a long-term unidirectional load. At the same time,
several muscle groups remain in a static position. The long-term work in the sitting position
is a characteristic example [5–7].
Dynamisation of Working Postures
The number of occupations requiring a sitting position is growing in all lines of
business due to technological progress (for example, programmers, dispatchers, designers).
Therefore, it is necessary to pay increased attention to dynamizing working postures
in office workplaces. This dynamization can minimize the health problems caused by
accumulating the static load. In this way, we eliminate the development of fatigue and
health problems [8,9].
There are three ways to operate dynamically during work in the sitting position:
1.
A regular change in the main working position—changing the sitting position to the
standing one. To ensure the continuity of the working activity, it is necessary to adapt
the workplace in such a way that the employee will be able to carry out the operation
also in the standing position. Such a change requires height-adjustable desks, and it
is also necessary to enlarge the workplace’s floor area.
2.
The regular positioning through dynamic sitting—dynamic sitting ensures the elimi-
nation of the static load acting on a person during long-term sitting.
3.
The non-stationary workplace—the employee has no fixed workplace. Non-stationary
workplaces are the trend of this millennium. They are typical of the so-called shared
workplaces—the employee chooses the workplace that is free at that time. This means

Appl. Sci. 2021,11, 4910 3 of 12
that after coming to the office, they take the seat which is most suitable for their
activity. At the same time, these workplaces include sofas, armchairs and dayrooms
where it is possible to work and rest. This type of workplace ensures dynamics just
by the variety of the workplace.
However, it is necessary to say that this type of workplace need not guarantee the suffi-
cient elimination of the static load’s impact. The ratio of the static and dynamic component
of work for a subjective selection of the workplace is not checked and controlled objectively.
However, the work dynamization in the framework of the sitting occupations cannot
be ensured to the necessary extent by the office equipment currently available. Therefore,
it is necessary to create a workplace that will respond to the human body variability to
ensure the necessary dynamics of the working positions, and at the same time, it will be
sufficiently autonomous for reducing bad working habits.
Currently, there are investigations in the area of measuring the curvature of the spine
in the sitting position. These investigations used the generally known medical methods
for diagnostics—X-ray or MRI [
10
–
13
]. For our research, we used the equipment DIERS
based on the principle of the Raster Stereography. One of the reasons why we utilized this
tool is that the repeated scanning process does not create undesirable effects for human
health [14–16].
2. Materials and Methods
Currently, scientists enforce the idea of the dynamic sitting position on a dynamic chair
or active changing of the working positions. We have been dealing with dynamizing the
work from various points of view for a long time—from the studies realized by prediction
and simulation up to utilizing the extended and virtual reality. In the framework of the
progressive approaches, we are working with the DIERS equipment, whose technology
combines computer modelling and Raster Stereography [17–20].
In the framework of investigating the sitting position, we have realized measurements
that monitor the impact of the sitting position on various types of chairs on the curvature
of the lower back. The measurements were carried out by the system DIERS formetric 4D
used for the non-invasive scanning of the spine and subsequent diagnostics.
2.1. System DIERS
The system DIERS works on the basis of the video Raster Stereography (see
Figure 2)
.
It consists of a projector that projects a light grid consisting of horizontal lines on the
person’s back. This grid is recorded by a scanning unit, and the software analyzes the
curvature of the individual grid’s lines. Based on this curvature, the system creates a 3D
image of the body surface [21–25].
The DIERS formetric 4D equipment is the basic module of the whole DIERS system.
The system also consists of additional modules DIERS Leg Axis that realizes a fast and
highly effective geometric analysis of the lower limbs and DIERS Pedogait that measures
the distribution of the pressure on the foot during walking [26–30].
The DIERS system provides complex information about the static of the whole body by
a single measuring process without any negative impact on the human organism. Therefore,
we decided to utilize this method. One measurement brings the necessary information in
the following areas [30]:
•The spine curvature (both lateral and frontal);
•The vertebral rotation;
•The position of the pelvis;
•The muscle imbalance.
Thanks to the automatic detection of the anatomic points in cooperation with the
correlation model that describes the dependence between the surface curvatures of the
body and the orientation of the vertebrae (from Turner-Smith and Drerup), the system is
able to show the real spine curvature and the position of the pelvis. The lower back holes
and the ridge of the seventh cervical vertebra are the basic anatomic points.

Appl. Sci. 2021,11, 4910 4 of 12
Appl. Sci. 2021, 11, 4910 4 of 12
• The position of the pelvis;
• The muscle imbalance.
Thanks to the automatic detection of the anatomic points in cooperation with the cor-
relation model that describes the dependence between the surface curvatures of the body
and the orientation of the vertebrae (from Turner-Smith and Drerup), the system is able
to show the real spine curvature and the position of the pelvis. The lower back holes and
the ridge of the seventh cervical vertebra are the basic anatomic points.
Figure 2. System DIERS (own study based on: [24]).
2.2. System DIERS—Advantages and Disadvantages
The DIERS system is a non-radiative device. Only the light beams are projected on
the human body. This is why people can be scanned repeatedly by this equipment, with-
out any negative impact on their health. Both the pregnant women and children can be
scanned too. This system is a diagnostic device; however, it can also serve for determining
the therapy effects selected based on the developed or developing spine disorder.
The limited possibilities of scanning belong to the disadvantages of this system. Until
now, the system has not been able to scan the cervical spine. Another disadvantage is that
this equipment cannot scan obese people, tattooed people or those with an extensively
haired back. A disadvantage of this equipment is also its size and the values of the mini-
mal distance between the device and individual sensors that must be strictly held [31].
2.3. Measurement Procedure
The laboratory measurements to detect the lower back spine curvature changes for
various types of chairs were realized in the Lab of Ergonomics and Movements at the
Department of Industrial Engineering of the University of Žilina in Žilina. Research re-
spondents were introduced to the use of measurements for research purposes. No inva-
sive methods were used during the study, and no substances were administered to the
respondents in relation to the measurements. The measurements were realized as follows:
• Three types of chairs were used—the static (fixed) chair, dynamic chair and physio-
therapeutic ball;
• The scanned volunteers (employees working in the predominantly sitting position,
students);
• Fifty measurements for each type of chair, the reference measurement in the standing
position.
Two types of posture were scanned for each chair—erect and relaxed sitting (see Fig-
ure 3). The erect sitting is characterized by the 90° angle that should be formed by the
Figure 2. System DIERS (own study based on: [24]).
2.2. System DIERS—Advantages and Disadvantages
The DIERS system is a non-radiative device. Only the light beams are projected on the
human body. This is why people can be scanned repeatedly by this equipment, without any
negative impact on their health. Both the pregnant women and children can be scanned too.
This system is a diagnostic device; however, it can also serve for determining the therapy
effects selected based on the developed or developing spine disorder.
The limited possibilities of scanning belong to the disadvantages of this system. Until
now, the system has not been able to scan the cervical spine. Another disadvantage is that
this equipment cannot scan obese people, tattooed people or those with an extensively
haired back. A disadvantage of this equipment is also its size and the values of the minimal
distance between the device and individual sensors that must be strictly held [31].
2.3. Measurement Procedure
The laboratory measurements to detect the lower back spine curvature changes for
various types of chairs were realized in the Lab of Ergonomics and Movements at the
Department of Industrial Engineering of the University of Žilina in Žilina. Research
respondents were introduced to the use of measurements for research purposes. No
invasive methods were used during the study, and no substances were administered to the
respondents in relation to the measurements. The measurements were realized as follows:
•
Three types of chairs were used—the static (fixed) chair, dynamic chair and physio-
therapeutic ball;
•
The scanned volunteers (employees working in the predominantly sitting position,
students);
•
Fifty measurements for each type of chair, the reference measurement in the standing
position.
Two types of posture were scanned for each chair—erect and relaxed sitting (see
Figure 3). The erect sitting is characterized by the 90
◦
angle that should be formed by the
thighs with the trunk, the arms and forearms, the thighs and shanks and the lower leg with
the foot. If the angles between these body parts do not form a 90
◦
angle, it is a so-called
relaxed sitting position [32–36].

Appl. Sci. 2021,11, 4910 5 of 12
Appl. Sci. 2021, 11, 4910 5 of 12
thighs with the trunk, the arms and forearms, the thighs and shanks and the lower leg
with the foot. If the angles between these body parts do not form a 90° angle, it is a so-
called relaxed sitting position [32–36].
Figure 3. Erect and relaxed sitting position.
During the testing procedure in the standing position, some of the participants
showed deformations of the spine. For measurement were selected participants whose
spine curvature and body posture could be considered adequate, from the point of view
of their age, anatomy, and physiology. In this way, we tried to minimize the negative
influence of acquiring the measurement data.
The bottom height of the chair seat was adjusted to 46 cm for the static chair and 48
cm for the dynamic chair. The difference in the participants’ chair adjustment was adapted
by the different thickness of the upholstery used. The height adjustment of the physio-
therapeutic ball was not possible; a ball with a standard diameter of 85 cm was used for
the experiment. This diameter complies with usage for persons with a height of up to 185–
195 cm. Due to the principle of scanning and acquiring data, the measurements were re-
alized without using the spine support.
The scanning procedure was realized in a one-month period to eliminate the influ-
ence of fatigue on the body posture of the participants. Fifty scans of the spine for the erect
standing position and fifty scans of the spine for the erect sitting position on a static chair
and physiotherapeutic ball were carried out. Each measurement recorded the values of
the kyphosis angle and the angle and depth of the lower back lordosis, as shown in Figure
4.
Figure 4. The angles of the kyphosis and lower back lordosis [30].
Figure 3. Erect and relaxed sitting position.
During the testing procedure in the standing position, some of the participants showed
deformations of the spine. For measurement were selected participants whose spine
curvature and body posture could be considered adequate, from the point of view of their
age, anatomy, and physiology. In this way, we tried to minimize the negative influence of
acquiring the measurement data.
The bottom height of the chair seat was adjusted to 46 cm for the static chair and
48 cm for the dynamic chair. The difference in the participants’ chair adjustment was
adapted by the different thickness of the upholstery used. The height adjustment of the
physiotherapeutic ball was not possible; a ball with a standard diameter of 85 cm was used
for the experiment. This diameter complies with usage for persons with a height of up to
185–195 cm. Due to the principle of scanning and acquiring data, the measurements were
realized without using the spine support.
The scanning procedure was realized in a one-month period to eliminate the influence
of fatigue on the body posture of the participants. Fifty scans of the spine for the erect
standing position and fifty scans of the spine for the erect sitting position on a static chair
and physiotherapeutic ball were carried out. Each measurement recorded the values of the
kyphosis angle and the angle and depth of the lower back lordosis, as shown in Figure 4.
Appl. Sci. 2021, 11, 4910 5 of 12
thighs with the trunk, the arms and forearms, the thighs and shanks and the lower leg
with the foot. If the angles between these body parts do not form a 90° angle, it is a so-
called relaxed sitting position [32–36].
Figure 3. Erect and relaxed sitting position.
During the testing procedure in the standing position, some of the participants
showed deformations of the spine. For measurement were selected participants whose
spine curvature and body posture could be considered adequate, from the point of view
of their age, anatomy, and physiology. In this way, we tried to minimize the negative
influence of acquiring the measurement data.
The bottom height of the chair seat was adjusted to 46 cm for the static chair and 48
cm for the dynamic chair. The difference in the participants’ chair adjustment was adapted
by the different thickness of the upholstery used. The height adjustment of the physio-
therapeutic ball was not possible; a ball with a standard diameter of 85 cm was used for
the experiment. This diameter complies with usage for persons with a height of up to 185–
195 cm. Due to the principle of scanning and acquiring data, the measurements were re-
alized without using the spine support.
The scanning procedure was realized in a one-month period to eliminate the influ-
ence of fatigue on the body posture of the participants. Fifty scans of the spine for the erect
standing position and fifty scans of the spine for the erect sitting position on a static chair
and physiotherapeutic ball were carried out. Each measurement recorded the values of
the kyphosis angle and the angle and depth of the lower back lordosis, as shown in Figure
4.
Figure 4. The angles of the kyphosis and lower back lordosis [30].
Figure 4. The angles of the kyphosis and lower back lordosis [30].
Figures 5–8show the measurements on individual types of chairs during the erect
sitting position and the reference scanning in the standing position (male, 39 years old,
height 182 cm and working in the office).

Appl. Sci. 2021,11, 4910 6 of 12
Appl. Sci. 2021, 11, 4910 6 of 12
Figures 5–8 show the measurements on individual types of chairs during the erect
sitting position and the reference scanning in the standing position (male, 39 years old,
height 182 cm and working in the office).
Figure 5. Reference measurement in standing position.
Figure 6. Sitting position on a static chair.
Figure 7. Sitting position on a dynamic chair.
Figure 8. Sitting position on a physiotherapeutic ball.
Figure 5. Reference measurement in standing position.
Appl. Sci. 2021, 11, 4910 6 of 12
Figures 5–8 show the measurements on individual types of chairs during the erect
sitting position and the reference scanning in the standing position (male, 39 years old,
height 182 cm and working in the office).
Figure 5. Reference measurement in standing position.
Figure 6. Sitting position on a static chair.
Figure 7. Sitting position on a dynamic chair.
Figure 8. Sitting position on a physiotherapeutic ball.
Figure 6. Sitting position on a static chair.
Appl. Sci. 2021, 11, 4910 6 of 12
Figures 5–8 show the measurements on individual types of chairs during the erect
sitting position and the reference scanning in the standing position (male, 39 years old,
height 182 cm and working in the office).
Figure 5. Reference measurement in standing position.
Figure 6. Sitting position on a static chair.
Figure 7. Sitting position on a dynamic chair.
Figure 8. Sitting position on a physiotherapeutic ball.
Figure 7. Sitting position on a dynamic chair.
Appl. Sci. 2021, 11, 4910 6 of 12
Figures 5–8 show the measurements on individual types of chairs during the erect
sitting position and the reference scanning in the standing position (male, 39 years old,
height 182 cm and working in the office).
Figure 5. Reference measurement in standing position.
Figure 6. Sitting position on a static chair.
Figure 7. Sitting position on a dynamic chair.
Figure 8. Sitting position on a physiotherapeutic ball.
Figure 8. Sitting position on a physiotherapeutic ball.
3. Results
Because the Slovak legislation determines erect sitting as the only acceptable working
position, we analyzed only the measurement results for this type of sitting. The value range

Appl. Sci. 2021,11, 4910 7 of 12
that the observed parameters achieved during 50 measurements of the reference scanning
are depicted in Figures 9–11.
Appl. Sci. 2021, 11, 4910 7 of 12
3. Results
Because the Slovak legislation determines erect sitting as the only acceptable working
position, we analyzed only the measurement results for this type of sitting. The value
range that the observed parameters achieved during 50 measurements of the reference
scanning are depicted in Figures 9–11.
Figure 9. Range of values of the observed body parameters.
The diagram in Figure 9 depicts the range of the measured values of the lower back
lordosis angle. Compared with the lower back lordosis angle in the standing position, this
angle is significantly lower in the sitting position. However, it is permissible due to the
biomechanics of the sitting position. The value range of the individual types of the sitting
positions are mutually comparable, but the lowest values of the lower back lordosis were
measured for sitting on a dynamic chair.
The diagram in Figure 10 depicts the range of the measured values of the lowest val-
ues of the kyphosis angle. Similarly, as in the case of the lower back lordosis, the kyphosis
angle is also significantly lower in the sitting position than in the standing position. The
lowest values of the kyphosis angle were measured again for sitting on a dynamic chair.
Figure 10. Range of values of the followed body parameters.
Figure 9. Range of values of the observed body parameters.
The diagram in Figure 9depicts the range of the measured values of the lower back
lordosis angle. Compared with the lower back lordosis angle in the standing position, this
angle is significantly lower in the sitting position. However, it is permissible due to the
biomechanics of the sitting position. The value range of the individual types of the sitting
positions are mutually comparable, but the lowest values of the lower back lordosis were
measured for sitting on a dynamic chair.
The diagram in Figure 10 depicts the range of the measured values of the lowest values
of the kyphosis angle. Similarly, as in the case of the lower back lordosis, the kyphosis
angle is also significantly lower in the sitting position than in the standing position. The
lowest values of the kyphosis angle were measured again for sitting on a dynamic chair.
Appl. Sci. 2021, 11, 4910 7 of 12
3. Results
Because the Slovak legislation determines erect sitting as the only acceptable working
position, we analyzed only the measurement results for this type of sitting. The value
range that the observed parameters achieved during 50 measurements of the reference
scanning are depicted in Figures 9–11.
Figure 9. Range of values of the observed body parameters.
The diagram in Figure 9 depicts the range of the measured values of the lower back
lordosis angle. Compared with the lower back lordosis angle in the standing position, this
angle is significantly lower in the sitting position. However, it is permissible due to the
biomechanics of the sitting position. The value range of the individual types of the sitting
positions are mutually comparable, but the lowest values of the lower back lordosis were
measured for sitting on a dynamic chair.
The diagram in Figure 10 depicts the range of the measured values of the lowest val-
ues of the kyphosis angle. Similarly, as in the case of the lower back lordosis, the kyphosis
angle is also significantly lower in the sitting position than in the standing position. The
lowest values of the kyphosis angle were measured again for sitting on a dynamic chair.
Figure 10. Range of values of the followed body parameters.
Figure 10. Range of values of the followed body parameters.
The diagram in Figure 11 depicts the value range of the lower back lordosis depth.
The lowest values of the lower back lordosis were measured during sitting on a physiother-
apeutic ball.

Appl. Sci. 2021,11, 4910 8 of 12
Appl. Sci. 2021, 11, 4910 8 of 12
The diagram in Figure 11 depicts the value range of the lower back lordosis depth.
The lowest values of the lower back lordosis were measured during sitting on a physio-
therapeutic ball.
Figure 11. Range of values of the followed body parameters.
As the diagram shows, the ranges of the measured values in the sitting position are
significantly different between individual types of chair. The average values of the indi-
vidual parameters during measurements are summarized in Table 1.
Table 1. Average values of the observed body parameters during measurements on various types
of chair.
Observed Parame-
ter
Standing Position
Static Chair
Dynamic Chair
Physiotherapeutic Ball
Average Value
Average Value
Average Value
Average Value
Kyphosis angle (°)
44.7
41.5
38.4
39.3
Lower back lordo-
sis angle (°)
29.6
19.7
17.6
17.8
Depth of lower
back lordosis (mm)
44.0
22.2
27.2
16.3
Table 2 presents the reference interval of kyphosis angle values and the values of
lower back lordosis in the standing position that should be kept due to the appropriate
spine biomechanics.
Table 2. Reference values of the angles of the kyphosis and lower back lordosis [37].
Parameter
Minimal Value
Maximal Value
Males
Females
Males
Females
Kyphosis angle (°)
39
57
Lower back lordo-
sis angle (°)
29
35
43
51
Based on the measured data in Table 1 and the reference values in Table 2 of the
angles of kyphosis and lower back lordosis, we can see considerable differences in the
spine curvature. Figure 12 compares the spine curvature in the lateral projection in the
sitting position on a static chair (green curves), dynamic chair (orange curves) and the
physiotherapeutic ball (blue curves) with the spine curvature of a volunteer in the stand-
ing position (red curve). The interrupted line represents the spine, and the continuous line
copies the volunteer’s body surface.
Figure 11. Range of values of the followed body parameters.
As the diagram shows, the ranges of the measured values in the sitting position
are significantly different between individual types of chair. The average values of the
individual parameters during measurements are summarized in Table 1.
Table 1.
Average values of the observed body parameters during measurements on various types
of chair.
Observed
Parameter
Standing Position Static Chair Dynamic Chair Physiotherapeutic
Ball
Average Value Average Value Average Value Average Value
Kyphosis angle (◦) 44.7 41.5 38.4 39.3
Lower back
lordosis angle (◦)29.6 19.7 17.6 17.8
Depth of lower
back lordosis (mm)
44.0 22.2 27.2 16.3
Table 2presents the reference interval of kyphosis angle values and the values of
lower back lordosis in the standing position that should be kept due to the appropriate
spine biomechanics.
Table 2. Reference values of the angles of the kyphosis and lower back lordosis [37].
Parameter Minimal Value Maximal Value
Males Females Males Females
Kyphosis angle (◦) 39 57
Lower back
lordosis angle (◦)29 35 43 51
Based on the measured data in Table 1and the reference values in Table 2of the
angles of kyphosis and lower back lordosis, we can see considerable differences in the
spine curvature. Figure 12 compares the spine curvature in the lateral projection in the
sitting position on a static chair (green curves), dynamic chair (orange curves) and the
physiotherapeutic ball (blue curves) with the spine curvature of a volunteer in the standing
position (red curve). The interrupted line represents the spine, and the continuous line
copies the volunteer’s body surface.

Appl. Sci. 2021,11, 4910 9 of 12
Appl. Sci. 2021, 11, 4910 9 of 12
Figure 12. Comparison of the spine curvature during sitting on various types of chairs and in the
standing position.
4. Discussion
Compared with the standing position, the measurement results show that a considerable
flattening process of the lower back lordosis develops in the sitting position (Figure 13). How-
ever, this flattening is biomechanically natural. A more significant finding of the measure-
ments is the more significant flattening of the lower back spine during sitting on a dynamic
chair compared with a static chair. The angle of the lower back lordosis of 19.7° was measured
during sitting on a static chair and 17.6° on a dynamic chair—it is a reduction of curvature by
40.5% compared with the natural curvature in the standing position. Based on these measure-
ments, we can present the following assumptions:
• The dynamic chair provides specific dynamics of sitting.
• The suitability of the dynamic chair for long-term utilization is to be verified by further
research and measurements. In order to find out which border position the employee can
achieve on a particular type of dynamic chair, the volunteer was asked to sit on the chair
with the least possible involvement of the back muscles. The result of such a sitting posi-
tion are shown in Figure 10. It is necessary to say that the depicted position represents an
extreme situation, and from the biomechanical point of view, the employee would not be
able to maintain this position for a long time. However, this position illustrates the free-
dom of the ball joint and which positions can develop.
• The dynamic chair enables different sitting positions in relation to the body posture. As
the measurement results show, the curvature of the lower back spine was lower during
sitting on a dynamic chair compared with the static chair. However, it is necessary to say
the spine curvature shows a high variability regarding the used chair and therefore, it is
probable that when testing another type of dynamic chair, the result could be different.
However, the dynamic chair cannot be assessed only based on the spine curvature; the
involvement of the postural muscles for keeping the correct body posture is an important
aspect. It is connected mainly with the moveable seat and the physiotherapeutic ball. Un-
til now, the authors have not included this fact in their research.
• Up to a certain degree, the dynamic chair reduces the static load. A larger group of mus-
cles is activated during sitting on a dynamic chair than during sitting on a static chair.
However, there is an assumption that in long-term sitting on this type of chair, the phasic
and postural muscles can be overloaded. This idea is to be verified by further research.
Figure 12.
Comparison of the spine curvature during sitting on various types of chairs and in the
standing position.
4. Discussion
Compared with the standing position, the measurement results show that a con-
siderable flattening process of the lower back lordosis develops in the sitting position
(Figure 13)
. However, this flattening is biomechanically natural. A more significant finding
of the measurements is the more significant flattening of the lower back spine during sitting
on a dynamic chair compared with a static chair. The angle of the lower back lordosis of
19.7
◦
was measured during sitting on a static chair and 17.6
◦
on a dynamic chair—it is
a reduction of curvature by 40.5% compared with the natural curvature in the standing
position. Based on these measurements, we can present the following assumptions:
•The dynamic chair provides specific dynamics of sitting.
•
The suitability of the dynamic chair for long-term utilization is to be verified by further
research and measurements. In order to find out which border position the employee
can achieve on a particular type of dynamic chair, the volunteer was asked to sit
on the chair with the least possible involvement of the back muscles. The result of
such a sitting position are shown in Figure 10. It is necessary to say that the depicted
position represents an extreme situation, and from the biomechanical point of view,
the employee would not be able to maintain this position for a long time. However,
this position illustrates the freedom of the ball joint and which positions can develop.
•
The dynamic chair enables different sitting positions in relation to the body posture.
As the measurement results show, the curvature of the lower back spine was lower
during sitting on a dynamic chair compared with the static chair. However, it is
necessary to say the spine curvature shows a high variability regarding the used chair
and therefore, it is probable that when testing another type of dynamic chair, the result
could be different. However, the dynamic chair cannot be assessed only based on the
spine curvature; the involvement of the postural muscles for keeping the correct body
posture is an important aspect. It is connected mainly with the moveable seat and
the physiotherapeutic ball. Until now, the authors have not included this fact in their
research.
•
Up to a certain degree, the dynamic chair reduces the static load. A larger group of
muscles is activated during sitting on a dynamic chair than during sitting on a static
chair. However, there is an assumption that in long-term sitting on this type of chair,
the phasic and postural muscles can be overloaded. This idea is to be verified by
further research.

Appl. Sci. 2021,11, 4910 10 of 12
Appl. Sci. 2021, 11, 4910 10 of 12
Figure 13. Sitting position on a dynamic chair without involvement of the back muscles.
5. Conclusions
The current human population ceases to move at work but also outside their work-
places. The results of such a lifestyle has been known for decades; for example, obesity,
cardiovascular disease, and body posture disorders. The number of occupations requiring
the sitting position as the main posture is growing due to the implementation of technol-
ogies simplifying and accelerating the working process. From the point of view of sitting-
position jobs, the working chair is the most crucial element. The long-term sitting position
increases the static load of the organism. A reduction in the static load can be achieved by
utilizing a dynamic chair. The research results in this article cannot be considered definite,
but they underline the fact that just a dynamic chair brings several risks and is no compact
solution for dynamizing the sedentary jobs. The subsequent research in the area of seden-
tary jobs and simultaneously a new task for ergonomics could be the development of a
dynamic workplace that would be autonomously adjusted to its users without their inter-
vention and based on pre-defined time intervals. This would ensure an active change of
the working position. This controlled dynamization of the sitting position could reduce
the disorders and health problems caused by sedentary jobs.
Author Contributions: All authors contributed equally to the research presented in this paper and
to the preparation of the final manuscript. All authors have read and agreed to the published version
of the manuscript.
Funding: Slovak Research and Development Agency under Grant APVV-19-0305.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Informed consent was obtained from all subjects involved in the
study.
Acknowledgments: This work was supported by the Slovak Research and Development Agency
under Grant APVV-19-0305.
Conflicts of Interest: The authors declare no conflict of interest.
References
1. Moretti, A.; Menna, F.; Aulicino, M.; Paoletta, M.; Liguori, S.; Iolascon, G. Characterisation of home working population during
COVID-19 emergency: A cross-sectional analysis. Int. J. Environ. Res. Public Health 2020, 17, 6284, doi:10.3390/ijerph17176284.
2. Ganesan, A.N.; Louise, J.; Horsfall, M.; Bilsborough, S.A.; Hendriks, J.; McGavigan, A.D.; Selvanayagam, J.B.; Chew, D.P. Inter-
national mobile-health intervention on physical activity, sitting, and weight: The stepathlon cardiovascular health study. J. Am.
Coll. Cardiol. 2016, 67, 2453–2463, doi:10.1016/j.jacc.2016.03.472, ISSN 0735-1097.
3. Vahdani, M.; Gholami, A.; Vahdani, H.; Mazaherinezhad, A.; Shaw, I. Rheumatic and musculoskeletal diseases among office
workers: A narrative review. J. Pain Manag. 2020, 13, 9–13, doi:10.1136/bmjopen-2020-038854, ISSN 1939-5914.
4. Horvathova, B.; Dulina, L.; Bigosova, E.; Barbusova, M. Analysis of Ergonomic Work Equipment Lowering the Static Load Based on
Trend of Development of Work Activities, Multidisciplinary Aspects of Production Engineering; Wydawnictwo Panova: Zabrze, Po-
land, 2019.
Figure 13. Sitting position on a dynamic chair without involvement of the back muscles.
5. Conclusions
The current human population ceases to move at work but also outside their work-
places. The results of such a lifestyle has been known for decades; for example, obesity,
cardiovascular disease, and body posture disorders. The number of occupations requiring
the sitting position as the main posture is growing due to the implementation of tech-
nologies simplifying and accelerating the working process. From the point of view of
sitting-position jobs, the working chair is the most crucial element. The long-term sitting
position increases the static load of the organism. A reduction in the static load can be
achieved by utilizing a dynamic chair. The research results in this article cannot be con-
sidered definite, but they underline the fact that just a dynamic chair brings several risks
and is no compact solution for dynamizing the sedentary jobs. The subsequent research
in the area of sedentary jobs and simultaneously a new task for ergonomics could be the
development of a dynamic workplace that would be autonomously adjusted to its users
without their intervention and based on pre-defined time intervals. This would ensure an
active change of the working position. This controlled dynamization of the sitting position
could reduce the disorders and health problems caused by sedentary jobs.
Author Contributions:
All authors contributed equally to the research presented in this paper and
to the preparation of the final manuscript. All authors have read and agreed to the published version
of the manuscript.
Funding: Slovak Research and Development Agency under Grant APVV-19-0305.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement:
Informed consent was obtained from all subjects involved in the study.
Acknowledgments:
This work was supported by the Slovak Research and Development Agency
under Grant APVV-19-0305.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
Moretti, A.; Menna, F.; Aulicino, M.; Paoletta, M.; Liguori, S.; Iolascon, G. Characterisation of home working population during
COVID-19 emergency: A cross-sectional analysis. Int. J. Environ. Res. Public Health 2020,17, 6284. [CrossRef] [PubMed]
2.
Ganesan, A.N.; Louise, J.; Horsfall, M.; Bilsborough, S.A.; Hendriks, J.; McGavigan, A.D.; Selvanayagam, J.B.; Chew, D.P.
International mobile-health intervention on physical activity, sitting, and weight: The stepathlon cardiovascular health study. J.
Am. Coll. Cardiol. 2016,67, 2453–2463. [CrossRef] [PubMed]
3.
Vahdani, M.; Gholami, A.; Vahdani, H.; Mazaherinezhad, A.; Shaw, I. Rheumatic and musculoskeletal diseases among office
workers: A narrative review. J. Pain Manag. 2020,13, 9–13. [CrossRef]
4.
Horvathova, B.; Dulina, L.; Bigosova, E.; Barbusova, M. Analysis of Ergonomic Work Equipment Lowering the Static Load Based
on Trend of Development of Work Activities, Multidisciplinary Aspects of Production Engineering; Wydawnictwo Panova: Zabrze,
Poland, 2019.
5.
Bertrand, S.; Skalli, W.; Delacherie, L.; Bonneau, D.; Kalifa, G.; Mitton, D. External and internal geometry of European adults.
Ergonomics 2006,49, 1547–1564. [CrossRef] [PubMed]

Appl. Sci. 2021,11, 4910 11 of 12
6.
Brusaca, L.A.; Barbieri, D.F.; Beltrame, T.; Milan-Mattos, J.C.; Catai, A.M.; Oliveira, A.B. Cardiac autonomic responses to different
tasks in office workers with access to a sit-stand table—A study in real work setting. Ergonomics 2021,64, 354–365. [CrossRef]
7. Gola, A. Design and management of manufacturing systems. Appl. Sci. 2021,11, 2216. [CrossRef]
8.
Danilczuk, W.; Gola, A. Computer aided material demand planning using ERP systems and Business Intelligence Technology.
Appl. Comput. Sci. 2020,16, 42–55. [CrossRef]
9.
Haughie, L.J.; Fiebert, I.M.; Roach, K.E. Relationship of forward head posture and cervical backward bending to neck pain. J.
Man. Manip. Ther. 2013,3, 91–97. [CrossRef]
10.
Park, J.H.; Srinivasan, D. The effects of prolonged sitting, standing, and an alternating sit-stand pattern on trunk mechanical
stiffness, trunk muscle activation and low back discomfort. Ergonomics 2021. [CrossRef] [PubMed]
11.
Meijer, E.M.; Frings-Dresen, M.H.W.; Sluiter, J.K. Effects of office innovation on office workers’ health and performance. Ergonomics
2011,52, 1027–1038. [CrossRef] [PubMed]
12.
Schellewald, V.; Kleinert, J.; Ellegast, R. Effects of two types of dynamic office workstations (DOWs) used at two intensities on
cognitive performance and office work in tasks with various complexity. Ergonomics 2020. [CrossRef]
13.
Grooten, W.J.; Äng, B.O.; Hagströmer, M.; Conradsson, D.; Nero, H.; Franzén, E. Does a dynamic chair increase office workers’
movement?—Results from a combined laboratory and field study. Appl. Ergon. 2017,60, 1–11. [CrossRef]
14.
Chowa´nska, J.; Kotwicki, T.; Rosadzi´nski, K. Comparison of standing and sitting position used in surface topography trunk
assessment. Post˛epy Nauk Medycznych 2012,XXV, 476–483.
15.
Baumgartner, D.; Zemp, R.; List, R.; Stoop, M.; Naxera, J.; Elsig, J.P.; Lorenzetti, S. The spinal curvature of three different sitting
positions analysed in an open MRI scanner. Sci. World J. 2012,2012, 184016. [CrossRef] [PubMed]
16.
Truszczynska, A.; Drzal-Grabiec, J.; Cichosz, P.; Trzaskoma, Z. Measurement of spinal curvatures during sitting on a rehabilitation
ball versus stool. Turk. Soc. Phys. Med. Rehabil. 2015,62, 148–155. [CrossRef]
17.
Lengsfeld, M.; Frank, A.; van Deursen, D.L.; Griss, P. Lumbar spine curvature during office chair sitting. Med. Eng. Phys.
2000
,22,
665–669. [CrossRef]
18.
Nishida, N.; Izumiyama, T.; Asahi, R.; Iwanaga, H.; Yamagata, H.; Mihara, A.; Nakashima, D.; Imajo, Y.; Suzuki, H.; Funaba, M.;
et al. Changes in the global spine alignment in the sitting position in an automobile. Spine J. 2020,20, 614–620. [CrossRef]
19.
Masharawi, Y.; Haj, A.; Weisman, A. Lumbar axial rotation kinematics in an upright sitting and with forward bending positions
in men with nonspecific chronic low back pain. Spine 2020,45, E244–E251. [CrossRef]
20.
Ahn, S.; Kim, S.; Kang, S.; Jeon, H.; Kim, Y. Asymmetrical change in the pelvis and the spine during cross-legged sitting postures.
J. Mech. Sci. Technol. 2013,27, 3427–3432. [CrossRef]
21.
Gabajova, G.; Furmannova, B.; Medvecka, I.; Grznar, P.; Krajcovic, M.; Furmann, R. Virtual training application by use of
augmented and virtual reality under university technology enhanced learning in Slovakia. Sustainability
2019
,11, 6677. [CrossRef]
22.
Grznar, P.; Gregor, M.; Krajcovic, M.; Mozol, S.; Schickerle, M.; Vavrik, V.; Durica, L.; Marschall, M.; Bielik, T. Modeling and
simulation of processes in a factory of the future. Appl. Sci. 2020,10, 4503. [CrossRef]
23.
Dulina, L.; Kramárová, M.; Czechova, I.; Wi˛ecek, D. Using modern ergonomics tools to measure changes in the levels of stress
placed on the psychophysiological functions of a human during load manipulations. Adv. Intell. Syst. Comput.
2019
,835, 499–508.
[CrossRef]
24.
Stefanik, A.; Grznar, P.; Micieta, B. Tools for continual process improvement—Simulation and benchmarking. In
Proceedings of the 14th International Symposium of the Danube-Adria-Association-for-Automation-and-Manufacturing: Intel-
ligent Manufacturing & Automation: Focus on Reconstruction and Development. 2003, pp. 443–444. Available online:
https://bsm.fsre.sum.ba/Downloads/Pdfs/proceedings/proceedings_2004/052-BSM2004-Stefanik-Tools_for_Continual_
Process_Improvement_-_Simulation_and_Benchmarking.pdf (accessed on 25 May 2021).
25.
Dijk, H.; Hööppener, P.F.; Siebenga, J.; Kragten, H.A. Medical photography: A reliable and objective method for documenting the
results of reconstructive surgery of pectus excavatum. J. Vis. Commun. Med. 2011,34, 14–21. [CrossRef] [PubMed]
26. Wasim, M.; Saeed, F.; Aziz, A.; Siddiqui, A.A. Dotted raster-stereography. In Advanced Methodologies and Technologies in Artificial
Intelligence, Computer Simulation, and Human-Computer Interaction; Khosrow-Pour, D.B.A.M., Ed.; IGI Global: Hershey, PA, USA,
2019; pp. 93–109.
27.
Roman, I.; Luyten, M.; Croonenborghs, H.; Lason, G.; Peeters, L.; Byttebier, G.; Comhaire, F. Relating the Diers formetric
measurements with the subjective severity of acute and chronic low back pain. Med Hypotheses
2019
,133, 109390. [CrossRef]
[PubMed]
28.
Rosemedical, Diers Leg Axis. Available online: https://www.rosamedical.ru/catalog/ortopedichescoe-oborudovanie-diers-
263/diers-leg-axis-diers-international-gmbh-germaniya.html?fbclid=IwAR0xnckqv3soR_87p8lmhrfqyNuyP2Crubb6fxkpoI-
LysNapN_uRnFmpe8 (accessed on 6 May 2021).
29.
Liu, X.; Yang, X.S.; Wang, L.; Yu, M.; Liu, X.G.; Liu, Z.J. Usefulness of a combined approach of DIERS Formetric 4D
®
and
QUINTIC gait analysis system to evaluate the clinical effects of different spinal diseases on spinal-pelvic-lower limb motor
function. J. Orthop. Sci. 2020,25, 576–581. [CrossRef] [PubMed]
30.
DIERS Biomedical Solutions. Available online: https://diers.eu/en/products/spine-posture-analysis/diers-formetric-4d/
(accessed on 9 February 2021).
31.
DIERS Statico 3D. Available online: https://diers.eu/en/products/spine-posture-analysis/diers-statico-3d/ (accessed on 2
February 2021).

Appl. Sci. 2021,11, 4910 12 of 12
32.
Decree of the Ministry of Health of the Slovak Republic No. 542/2007 of 16th August 2007 on Details of Health Protection against Physical
Stress at Work, Mental Workload and Sensory Stress at Work. 2007. Available online: https://www.ilo.org/dyn/natlex/natlex4
.detail?p_lang=en&p_isn=84281&p_country=SVK&p_count=346&p_classification=14&p_classcount=54 (accessed on 25 May
2021).
33.
Synnott, A.; Dankaerts, W.; Seghers, J.; Purtill, H.; O’Sullivan, K. The effect of a dynamic chair on seated energy expenditure.
Ergonomics 2017,60, 1384–1392. [CrossRef]
34.
Roossien, C.C.; Stegeng, J.; Hodselmans, A.P.; Spook, S.M.; Koolhaas, W.; Brouwer, S.; Verkerkea, G.J.; Reneman, M.F. Can a smart
chair improve the sitting behavior of office workers. Appl. Ergon. 2017,65, 355–361. [CrossRef]
35.
Triglav, J.; Howe, E.; Cheema, J.; Dube, B.; Fenske, M.J.; Strzalkowski, N.; Bent, L. Physiological and cognitive measures during
prolonged sitting: Comparisons between a standard and multi-axial office chair. Appl. Ergon.
2019
,78, 178–183. [CrossRef]
[PubMed]
36.
Buˇcková, M.; Gašo, M.; Pekarˇcíková, M. Reverse logistic. In InvEnt 2020: Industrial Engineering-Invention for Enterprise [Electronic].
Bielsko-Biała: Wydawnictwo Akademii Techniczno-Humanistycznej; Wydawnictwo Akademii Techniczno-Humanistycznej: Bielsko-
Biała, Poland, 2020; pp. 36–39, ISBN 978-83-66249-48-6. Available online: https://www.priemyselneinzinierstvo.sk/wpcontent/
uploads/2020/10/InvEnt-2020-Proceedings-web.pdf (accessed on 2 February 2021).
37.
Schröder, J.; Stiller, T.; Mattes, K. Referenzdaten in der Wirbelsäulenformanalyse. Manuelle Medizin
2011
,49, 161–166. [CrossRef]