Biomedical Human Kinetics, 13, 121–127, 2021
Pressure distribution in tilting and reclining wheelchairs
with an air cushion: A pilot study
Hyunwoo Choi, Heymin Lee, Jeongwon Choi, Jisu Moon, Juhyang Jeong, Dohee Joo, Ingyu Yoo
Department of Occupational Therapy, College of Medical Science, Jeonju University, Republic of Korea
Study aim: The aim of this study was to determine the optimal angle for maximizing pressure distribution in two types of
wheelchairs (tilting and reclining) while using a ROHO cushion, which offers relatively effective pressure distribution.
Material and methods: This study enrolled 28 male and female college students who understood the purpose of the study and
agreed to participate. This study aimed to determine the optimal angle for tilting and reclining wheelchairs when using a ROHO
cushion at angles of 10°, 20°, and 30° with tilted wheelchairs and 90°, 110°, and 130° with reclining wheelchairs.
Results: The analysis showed that an improved pressure distribution when a tilting wheelchair was used versus a reclining one.
Conclusion: The results of this study will help wheelchair users or their guardians to select the optimal wheelchair angle when
changing their posture to prevent bedsores. Although no slippage was observed in our study, it is important to remember the
proper back position to prevent unnecessary slippage.
Keywords: Cushion – Pressure sore – Wheelchair
Wheelchairs facilitate access by users in the community.
However, according to the 2011 Wheelchair Safety Acci-
dent Survey Report, 65.2% of users reported that they expe-
rienced pressure sores due to sitting for a long time .
Pressure sores are a condition in which constant pres-
sure on certain areas of the body disrupts the circulation
of oxygen and nutrients to these areas. If severe, this can
cause necrosis. The risk of pressure sores is increased
if proper pressure distribution over the buttocks is not
achieved when the individual is seated in the wheelchair
[15, 20]. The main cause of pressure sores is increased
pressure through prolonged sitting in the wheelchair. In
particular, when nerve tissues or sensory functions are
impaired, buttock bedsores due to long-term use of the
wheelchair may not be recognized in time, leading to
necrosis. The development of pressure ulcers has negative
impacts on the patient’s prognosis .
The basic principle for preventing pressure sores is to
reduce the constant pressure while seated in the wheelchair
. The most common mode of adjustment based on this
sure by distributing the pressure over the contact surface.
This is especially true for patients with major limitations
who have difculty changing their posture independent-
ly . Pressure on the sores is reduced by dispersing the
overall pressure over the contact surface. Cushions de-
signed to prevent pressure sores have been developed in
blends, and gels, among others. Among them, the type
with the highest level of user satisfaction is the air cushion
. This was supported by a study on the guidelines for
the prevention of bed sores  and a comparative study
on sitting pressure distribution according to the type of
cushion for preventing bedsores . Other studies, such
as an analysis of body pressure distribution according to
the design elements of the cushioning air cell, have shown
that the pneumatic cushion is more effective compared to
the other types [2, 5, 14, 21].
Second, wheelchair tilt can be adjusted to reduce the
pressure. There are two types of wheelchairs: the tilting
type, in which the seat and back are rotated backward to-
gether, and the reclining type, in which only the back sup-
port can be laid back. Past studies have shown that both
tilting and reclining adjustments can reduce excessive
pressure on the buttocks during wheelchair use. This has
been suggested as a particularly useful intervention for pa-
tients with quadriplegia .
Author’s address Ingyu Yoo, Department of Occupational Therapy, College of Medical Science, Jeonju University, #303 Cheonjam-
ro, Wansan-gu, Jeonju-si, Jeollabuk-do, 560-759, Republic of Korea firstname.lastname@example.org
Choi H. et al.
However, despite various studies on wheelchairs and
the development of bedsore-prevention cushions, many
users with spinal cord and other injuries still suffer from
bedsores . A good posture is one from which the indi-
vidual can function optimally, which means a posture from
which one can respond appropriately to various situations
with minimal energy consumption . Appropriate seat-
ing for wheelchair users facilitates user stability and nor-
malsensoryinput to enable efcientinteractionwiththe
surrounding environment, suppresses discomfort caused
by abnormal sensations, and reduces the risk of bedsores
due to pressure overload .
In this regard, two important studies were identied.
First, regarding the adjustment of the wheelchair backrest
angle, previous studies have suggested a tilt angle of 20° or
more for the relief of hip joint pressure  and a reclining
angle of 120° or more. Another study compared the aver-
age pressure index according to the type of cushion and the
angle of the wheelchair and showed effective reduction in
to the individuals studied, and each reported limited success
in reaching an integrated conclusion [11, 25].
Using a cushion is the easiest way to prevent bedsores.
The cushion is employed to prevent bedsores from occurring
before they develop and serves here as a representative inter-
vention method to reduce sitting contact pressure [1, 2]. This
study was based on the hypothesis that pressure distribution
would be more effective if, in addition to using a cushion,
the angle of the wheelchair were properly adjusted.
This study was carried out to determine the optimal
angle for maximizing the pressure distribution with two
types of wheelchairs, tilting and reclining, while using
a ROHO cushion, which offers relatively effective pres-
Material and methods
This study was conducted with 28 college students
(14 males and 14 females; mean age 23.7 years, mean
height 167.57 cm, mean weight 61.12 kg, hip width 32.0
cm, mean femoral length 45.5 cm) who understood the
purpose of the study and agreed to participate. All subjects
were provided with enough information to understand the
experiment, after which they agreed to participate in the
study. The inclusion criteria were as follows.
First, we recruited healthy men and women in their
24-year-oldsinthe 2015 Korea Body Size Survey Index
(height: male 174.2 cm, female 160.9 cm; weight: male
71.5 kg, female 55.1 kg; hip width: male 32.8 cm, female
32.5 cm; thigh length: male 30.3 cm, female 28.6 cm) .
Second, they had no experience with pressure measure-
ment. Third, they could maintain their posture for repeated
measurements. Fourth, they had no musculoskeletal disor-
ders (upper or lower limbs). The experiment was approved
Weused aROHOaircushion (MK-ASC-5B,Mickey
Korea), which is mainly used to prevent bedsores. The
cushion is designed in the form of a closed air grid, with
airowpossiblebetweenthe cells. Pressure iscontrolled
by maximizing the body contact area, which effects cell
volume change. In this study, the height of the cushion
was adjusted by the participants beforehand following the
1. Tilting wheelchair
gether, and the angle can be adjusted from 0° to 30°. In this
study, three angles (10°, 20°, 30°) were used for all partici-
each experiment, the heights of the arm rest, foot rest, and
head restraint were adjusted so that pressure measurement
for all participants could be performed under the same
a) Tilting wheelchair b) Reclining wheelchair c) ROHO cushion d) Pressure mapping
Figure 1. Apparatus for study
Comparison of pressure distribution wheelchairs
2. Reclining wheelchair
The reclining wheelchair used in this study is one in
which only the backrest tilts (P7003, DAESE). The back-
rest angle can be adjusted from 90° to 180°. In this study,
the same backrest angles were used for all subjects (90°,
110°, and 130°). The heights of the arm rest, foot rest, and
head restraint were adjusted in advance so that pressure
measurement for all participants could be performed un-
der the same conditions. The wheelchair is 40 cm wide
3. Pressure mapping system
pressure distribution when seated in the wheelchair with
lyzes the interface pressure between two surfaces through
a thin, sensitive sensor. Data can be analyzed and stored
in CONFORMat Research 7.60 as pressure values (such
as the average pressure, standard deviation, and maximum
pressure) as well as visualized using colored contour lines.
At this time, pressure was recorded in mmHg units, and
the maximum pressure that could be measured was 200
mmHg. The sensors can also be used as force sensors with
Participants wore comfortable clothing without back
Also, if necessary, the footrest height was adjusted so that
the feet reached the footrest.
This study was conducted to determine the optimal
angle for tilting and reclining wheelchairs when using
ROHO cushions at angles of 10°, 20°, and 30° for tilting
wheelchairs and 90°, 110°, and 130° for reclining wheel-
chairs. A pressure mapping system was used to measure
the pressure, and the average pressure for each frame was
measured by specifying an area with an initial value of
60mmHg orhigherfromthemid-point ofboththighsto
the back of the buttocks. The pressure distribution was
measuredfor3minutes at each angle, with a 5-min rest
period after each measurement.
The average pressure index (mmHg) of each frame
(50, 100, 150, 200 frames) was used to compare the pres-
sure distribution according to the wheelchair (tilting and
reclining) angle . Because the pressure value can be
adjusted according to the physical characteristics of the
individual during the initial sitting, the weight and height
of each subject were entered into the software to analyze
changes in the pressure on and area of the cushion. In this
study, the average pressure of each frame was measured,
and a zone with an initial value of 60 mmHg or more was
The SPSS statistical package (SPSS 25.0, Armonk,
NY, USA) was used to analyze the average pressure in-
wheelchair used to prevent pressure sores. For general
participant characteristics, descriptive statistics were used,
and repeated-measures one-way ANOVA was used to
compare the pressure distribution over the hip according
Pressure readings for the reclining-type wheelchair
were 93.55 mmHg at 90°, 89.80 mmHg at 110°, and
chair were 91.91 mmHg at 10°, 88.53 mmHg at 20°, and
86.86 mmHg at 30°. The average pressure for the reclin-
ing wheelchair was lowest at 130°, and that for the tilt-
ing wheelchair was lowest at 30°. A comparison of overall
pressure revealed a distribution of lower pressure using
a tilting wheelchair compared to using a reclining wheel-
The repeated-measures ANOVA comparing pressure
differences according to the angle of the backrest for each
Conditions AI (mmHg) SD F p
90° 93.55 7.53
110° 89.80 6.38
130° 88.29 5.39
10° 91.92 7.81
20° 88.53 6.42
30° 86.86 5.48
P < 0.05*
Table. 1. Pressure distribution in recline angles (N = 28)
Choi H. et al.
vealed the following. The comparison of the average pres-
hadanF-valueof16.353,indicating a signicant differ-
ence in the sitting pressure index according to wheelchair
type (p = 0.000) (Table 1). The multiple comparisons test
showed that the pressure under the 90° reclining condition
wassignicantlyhigherthan thatat110°or 130°aswell
as that at 20° or 30° when a tilting wheelchair was used
except at 90° (p < 0.01). At 30°, the pressure from using
the reclining-type wheelchair was signicantly different
from that at 90° (p < 0.01) or from using the tilting wheel-
ferences were observed when the tilting wheelchair was
used at 10° compared to 20° or 30° or using the reclining
wheelchair at 130°(p < 0.01). There was no statistically
The purpose of this study was to determine the optimal
angle of each wheelchair type by checking the effects of
wheelchair type (tilting versus reclining) and backrest an-
gle on sitting contact pressure using a ROHO pneumatic
bedsore-prevention cushion to prevent pressure sores.
The results showed that the average sitting pressure in the
tilting-typewheelchairwas lowestat30°, andthatinthe
son of total pressure showed that the pressure was lower
for the tilting wheelchair than for the reclining wheel-
chair. Furthermore, angles of 110° or more for the reclin-
ing wheelchair and 20° or more for the tilting wheelchair
had a signicant pressure-reducing effect. However, no
signicant difference was found between using a reclin-
ing wheelchair at 110° or 130° or between using a tilting
wheelchair at 20° or 30°.
An optimal wheelchair angle adjustment may help to
prevent pressure sores, and adjusting the angle accord-
ing to the characteristics of the wheelchair may further
reduce the risk. However, additional cushions applied
to the seat can have a variety of effects depending on
the user’s posture. In addition, the proper use of the two
means of adjustment presented in this study can be more
effective than the use of a single method and an effec-
tive means of ensuring user satisfaction and health sta-
tus [4, 12].
To determine the optimal angles for reducing pressure
when using two types of wheelchairs, this study referred
to past research evaluating angles of 10°, 20°, and 30° for
tilting wheelchairs and 90°, 110°, and 130° for reclining
wheelchairs. In a previous study, a reclining wheelchair
pare postural changes and pressure distributions between
two angles (90° and 110°) . The mean pressure index
leagues explained the necessity of adjusting the backrest
angle to prevent bedsores, suggesting that the angle of the
In this study, two types of wheelchairs were examined
while varying the angle of use, and the contact pressure on
the buttocks was measured. The pressure average index
(AI) was used to measure the sitting pressure distribution.
Figure 2. Pressure in the reclining and tilting wheelchair conditions (N = 28, Mean ± SD)
dition,T-10:10 degree tiltingwheelchaircondition, T-20:20degreetilting wheelchaircondition,T-30:30 degree tiltingwheelchaircondition;
Comparison of pressure distribution wheelchairs
The pressure AI of the seating surface serves as an index
of the uniform dispersion of contact pressure .
Analysis of the average sitting pressure associated
with the use of each wheelchair with an air cushion ac-
cording to the pressure AI of the seating surface revealed
a distribution of lower pressure for the reclining wheel-
chair at 110° and 130° compared to 90°. This result was
partially consistent with a previous study, with some
differences. As the reclining wheelchair angle changed,
Jan and colleagues compared the pressure distribution
over the gluteal area in patients with a spinal cord injury.
100° and 120° . In addition, Kwon and colleagues
compared the average pressure change according to the
from a neutral posture of 90°. There were no differences
at 100° and 110°, but a large difference was observed
at 120° [4, 19]. Previous studies have demonstrated that
pressure can be reduced by maintaining an angle of 120°
reducing effect even at 110°. In this study, to minimize
the differences in the subjects’ physical condition, their
physical condition was determined based on standard
values for men in their 20 s. This study design eased the
process of drawing distinctions according to wheelchair
type and angle [24, 25].
For the tilting wheelchair, a signicant pressure dif-
ference was observed when the pressure distribution was
maintained by a tilt angle of >20°. Fujita and Mori 
compared the pressure distribution in healthy adult men
to that in individuals in wheelchairs at angles of 5°, 10°,
20°, and at full tilt. Their results showed that the contact
area increased and the pressure decreased as the angle de-
ences at 15°, 25°, and 35° when using a tilted wheelchair
with a basic foam cushion in patients with a spinal cord in-
cient for effective pressure reduction compared with 100°
. Our ndings are partially consistent with previous
changes. In the present study,a tilt angle of 20° signi-
cantly decreased the pressure, although angle adjustments
tilt angle was limited to 30°. The reason may be that the
present study was conducted mainly in the range where
effectiveness had been demonstrated in previous studies.
Improper use of the cushion, which may result in the user
slipping down in the chair, may create the highest average
maximum pressure in a sitting position. No slippage due
to the cushion was observed in our study, but it is impor-
tant to remember the correct backrest position to prevent
unnecessary slippage when working to prevent pressure
The ROHO cushion used in this study is relatively
effective at preventing bedsores. However, few studies
have considered both the angle of the cushion and that of
the wheelchair back, as we did in this study. Many stud-
ieshave comparedcushion typeswiththebackrestxed
backrest without using a cushion [1, 4, 11]. Incorrect pos-
ture adjustment can be accompanied by higher pressure.
The placement of pillows or special positioning cushions
designed to prevent pressure sores can be helpful. The
cushion used in this study is the most frequently used
cushion to prevent bedsores. Our study also demonstrated
superior pressure reduction, and unnecessary slipping did
Our study was conducted using two recommended
methods, i.e., pressure sore-preventing cushions and an
adjusted backrest angle, which can improve the pressure
distribution in wheelchairs. The results of this study will
help wheelchair users or their guardians with selecting an
optimal wheelchair angle to prevent bedsores when chang-
ing the patients’ posture. Patients with bedsores often can-
not manage this process themselves, so they need help
from others. This situation can limit their daily lives. Fur-
thermore, based on the results of this study, it is necessary
users in daily and social life considering the physiological
The limitations of this study are as follows. First,
the participants were not actual wheelchair users. This
study selected subjects without disabilities to ensure
participant homogeneity because it was necessary to
analyze the cushion and wheelchair angle, rather than
the characteristics of the participants, as the main vari-
ables. However, further studies that examine these vari-
ables will need to be planned. Second, the wheelchair
posture employed in this study was a static one. As the
proportion of situations in which users maintain a dy-
namic posture rather than a static one is high, it will
long-termsitting in future studies. Third, only buttock
pressure was considered when the pressure distribution
was measured according to the angle of the wheelchair.
Thus, we did not examine how the pressure distribution
affected other body parts.
The basic principle of preventing pressure sores is to
reduce constant pressure during sitting in the wheelchair.
Our study examined the optimization of two methods,
ments to the backrest angle. We showed that a position
of ≥110° for the reclining wheelchair and ≥20° for the
Choi H. et al.
tilting chair had signicant pressure-reducing effects.
Future studies will be needed to conrm the pressure
change at various angles by applying equipment that can
dition to the pressure.
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© University of Physical Education, Warsaw, Poland
I would like to thank the co-authors who took the time to
provide information for the study. We would like to thank
the professors at the Department of Occupational Therapy
in Jeonju University who provided insight and expertise
that greatly assisted this study.