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Mismatch between classroom furniture and anthropometric measures of university students
International Journal of Industrial Ergonomics 74 (2019) 102864
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Mismatch between classroom furniture and anthropometric measures of university students Emin Kahya Eskisehir Osmangazi University, Engineering and Architecture Faculty, Department of Industrial Engineering, Eskisehir, Turkey
A R T I C L E I N F O
A B S T R A C T
Keywords: Anthropometric measure Classroom furniture University student Mismatch
The appropriate design of tools, equipment and accessories for human body sizes, while meeting the social, cultural, economic and psychological needs of people, provides maximum benefit. This is crucial for students who spend most of their time using school furniture. The aim of the study is to investigate the mismatch between school furniture dimensions and students’ anthropometric measures. Nine anthropometric measures were taken of 225 students (68 female and 157 male) from nine departments of an engineering faculty using a specially designed measurement tool. The mismatch percentages between the existing classroom furniture dimensions and the anthropometric measures were determined using some well-known criterion equations. The results indicated a considerable mismatch: 44.45% for seat height, 100% for seat depth, and 21.28% for desk height. Two types of proposed classroom furniture achieved much higher percentage matches. The match percentages were above 70% for four dimensions for type A and above 95%, except for seat height and width of backrest, for all of the dimensions for both types. Relevance to industry: This study helps in establishing and motivating necessary further studies in classroom ergonomics in university settings.
1. Introduction University students spend a considerable part of their daily life (5–8 h per day) at school. While staying at school, they conduct most of their activities (e.g., reading and writing) sitting on school furniture. Considering the amount of time they spend in sedentary activities, stu dents are at particular risk of suffering from negative effects from poorly designed furniture. The use of ill-fitted furniture may increase the risk of developing musculoskeletal disorders. Furniture well designed to accommodate the anthropometric measures of students promotes cor rect sitting posture and reduces the incidence of musculoskeletal disorders. Mismatches between students’ anthropometric dimensions and furniture dimensions can affect classroom activities such as writing, reading and typing, causing pain in the back, shoulders, neck, legs and eyes (Fidelis et al., 2018). A number of studies (e.g. Murphy et al., 2004) have reported that the improper design of school furniture can have a significant effect on the posture of students. They have concluded that the use of poorly designed classroom furniture often results in discom fort as well as pain, especially in the neck, shoulders and upper and lower back. Mismatches between human anthropometric measures and
equipment dimensions are known to be a contributing factor in decreased productivity, discomfort, accidents, biomechanical stresses, fatigue, injuries, and cumulative traumas (Mandahawi et al., 2008). During the past few decades, there has been increasing concern about the design of school furniture and their match or mismatch to students’ anthropometric measures. Such mismatches have been re ported in several countries, including Greece (Gouvali and Boudolos, 2006), Iran (Dianat et al., 2013), Portugal (Assuncao et al., 2013), the United States (Parcells et al., 1999), India (Savanur et al., 2007) and Chile (Castellucci et al., 2010). A few studies (e.g. Castellucci et al., 2014; Castellucci et al., 2015) reviewed the literature describing the criterion equations for defining the mismatch between students and school furniture. The sample used for testing the different equations consisted of volunteer subjects from schools. Parcells et al. (1999) examined the mismatch between school furniture and students by measuring the anthropometric characteristics of American children. They reported that fewer than 20% of students could find acceptable chair/desk combinations. Gouvali and Boudolos (2006) study focused on the suitability of school furniture to the anthropometric measures of Greek children using combinational equa tions modified in accordance with principles proposed by the literature.
E-mail address: [email protected]. https://doi.org/10.1016/j.ergon.2019.102864 Received 30 January 2018; Received in revised form 17 August 2019; Accepted 4 October 2019 Available online 17 October 2019 0169-8141/© 2019 Elsevier B.V. All rights reserved.
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International Journal of Industrial Ergonomics 74 (2019) 102864
They determined that desk and seat heights were taller than the accepted limits for most children (81.8%), while seat depth was appropriate for only 38.7% of children. Castellucci et al. (2010) compared furniture dimensions in three different schools with the anthropometric characteristics of Chilean students in order to evaluate the potential mismatch between them. A study conducted by Dianat et al. (2013) evaluated the potential mismatch between classroom furniture dimensions and anthropometric measures of 978 Iranian high school students. Nine anthropometric measurements and five di mensions of the existing classroom furniture were measured and then compared (using match criterion equations) to identify any mismatch between them. The results indicated a considerable mismatch between the body measures of the students and the existing classroom furniture, with seat height (60.9%), seat width (54.7%) and desktop height (51.7%) being the dimensions with the highest level of mismatch. More studies have applied principles for the design of workplace furniture than for university furniture for students, although the situa tion in universities seems to be more serious (Hoque et al., 2014). It is necessary to draw attention to university furniture design. Several re searchers (e.g. Parcells et al., 1999) have incorporated measurements obtained from the elbow height in their designs to improve classroom furniture. In several countries, essential efforts have been made to introduce uniform classroom furniture design guidelines and standards. Recently, Thariq et al. (2010), Hossain and Ahmed (2010), Musa and Ismaila (2014), Hoque et al. (2014), Bhuiyan and Hossain (2015), and Fidelis et al. (2018) have presented some studies to design ergonomi cally correct furniture for university students. In a study conducted by Musa and Ismaila (2014), anthropometric measures were collected from 720 students of three randomly selected tertiary institutions in Nigeria, covering the age group between 17 and 27 years. The results indicated a substantial degree of mismatch between the students’ anthropometric measures and the furniture dimensions. The chairs were either too tall or too deep for the students. The data also revealed that the desks were too tall for most of the students. Hoque et al. (2014) evaluated the potential mismatch between university classroom furniture dimensions and anthropometric measures of 500 Bangladeshi university students. Fifteen anthropometric measures and nine dimensions from the existing classroom furniture were measured and then compared to identify po tential mismatch between them. The results indicated that the seat height was too tall. Bhuiyan and Hossain (2015) developed a method ology in designing ergonomic furniture used by the university students based on anthropometric measures and using an artificial neural network. Fidelis et al. (2018) determined the ergonomic suitability of classroom furniture at the Federal University of Technology, Akure, Nigeria. 261 randomly selected students (133 males and 128 females) participated in the study. The study revealed that 90% of the partici pants used desks that were too tall, 2% used desks that were too short and only 7% used desks with heights that fit their anthropometric measures. Several studies have been conducted on the design of ergonomically correct furniture for university students in Turkey. In a study conducted by Tunay et al. (2005), anthropometric measurements were obtained from 187 university students (45 female and 138 male) at Zonguldak Karaelmas University. The anthropometric measures were gathered to suggest the dimensions of the school furniture. Dizdar and Okçu (2007) aimed to evaluate the existing design of the classroom furniture used at Bozok University. The anthropometric measures of 143 students and the furniture dimensions were compared in order to identify any in compatibility between them. Tunay and Melemez (2008) carried out the necessary anthropometric measurements of classroom furniture used in Turkish higher education. Thirteen anthropometric measures from 1049 students were obtained while they are standing and sitting. Some studies have acknowledged the importance of appropriate classroom furniture used in university education in Turkey but, in recent years, there were a few studies establishing a relationship between school furniture and student anthropometric measures. This study is the
first attempt to evaluate the possible mismatch (using match criterion equations) between school furniture dimensions and anthropometric measures of university students and to propose the dimensions of two types of classroom furniture maximizing the match percentages. 2. Mismatch between classroom furniture and anthropometric measures 2.1. Measures School furniture and also potential mismatch equations are grouped according to the specific type of school furniture under consideration: ➢ Seat (including backrest) ➢ Desk ➢ Interactions between desk and seat. Table 1 shows a summary of relationships between school furniture dimensions and anthropometric measures. Anthropometric measures required for school furniture dimensions are displayed in Fig. 1. The measures are taken from students using an anthropometric de vice, in standing and sitting positions while they are without shoes, wearing casual dress. Definitions for nine measures (Pheasant, 1998; Tunay et al., 2005; Dizdar and Okçu, 2007; Oyewole et al., 2010; Cas tellucci et al., 2014, 2015; Hoque et al., 2014) are given in Appendix A. 2.2. Criterion equations for mismatch Applied anthropometric and ergonomic principles should be used to design and evaluate school furniture and to define the range in which each furniture dimension is considered appropriate. To identify a match or mismatch, anthropometric dimensions of each individual student are compared to the relative furniture dimensions (Dianat et al., 2013). Mismatch is defined as incompatibility between the dimensions of classroom furniture and the dimensions of a student’s body. All mismatch equations, one- and two-way, are considered (Castellucci et al., 2014). For the evaluation and design of classroom furniture, it is necessary to consider applied anthropometry and ergonomics principles and define an equation or equations enabling to determine the values of each furniture dimension; when it has a minimum and maximum limit, a two-way equation is considered appropriate and when it only has a maximum or a minimum limit, a one-way equation (e.g. Equation (5.1)) is the required option (Castellucci et al., 2010). Table 1 Relationship dimensions.
between
anthropometric
measures
school
furniture
Section
School furniture dimension
Anthropometric measures
Seat
Seat Height (SH) Seat Width (SW) Seat Depth (SD) Upper Edge of Backrest (UEBR)
Popliteal Height (PH) Hip Breadth (HB) Buttock Popliteal Length (BPL) Shoulder Height (SH), Subscapular Height(SSH) Lumber Height (LH), LEBR ¼ UEBR – HBR Lumber height Shoulder Breadth (SB) Functional criteria (~5� ) Popliteal Height (PH), Elbow Height (EH), Shoulder Height (SH) Functional criteria Functional criteria, Seat With (SW) Knee Height (KH) Thigh Thickness (TT), Knee Height (KH) Elbow Height (EH)
Backrest
Lower Edge of Backrest (LEBR)
Desk
Height of Backrest (HBR) Width of Backrest (WBR) Slope Desk Height (DH) Desk Depth (DD) Desk Width (DW)
Interaction
Underneath Desk Height (UDH) Seat to Desk Clearance (SDC) Seat to Desk Height (SDH)
2
and
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International Journal of Industrial Ergonomics 74 (2019) 102864
Fig. 1. Anthropometric measures.
In the literature, there is a considerable variability in the equations that can be used to test the mismatch between anthropometric measures and furniture dimensions (Castellucci et al., 2016). In this study, seven furniture dimensions were evaluated, applying the most commonly used and recommended equations (e.g. Dianat et al., 2013; Castellucci et al., 2015).
2.2.1. Seat height (SH) Most researchers have concluded that popliteal height (PH) should be higher than seat height (SH) (Parcells et al., 1999; Mokdad and Al-Ansari, 2009; Dianat et al., 2013); otherwise most students will be unable to rest their feet on the floor properly, thus generating increased tissue pressure on the posterior surface of the knee (Castellucci et al.,
Fig. 2. Correlation between anthropometry and school furniture dimensions (Yanto et al., 2017). 3
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International Journal of Industrial Ergonomics 74 (2019) 102864
2015). Seat height allows the knee to be flexed so that the lower leg forms a maximum angle of 30� relative to the vertical axis (Molenbroek et al., 2003). As shown in Equation (1), seat height needs to be lower than popliteal height so that the lower leg forms a 5–30� angle relative to the vertical and the shin-thigh angle is between 95� and 120� (Gouvali and Boudolos, 2006). In all studies, the anthropometric measures have been made without shoes. Shoe correction (SC) is a height between 2 cm (Gouvali and Boudolos, 2006) and 3 cm (Castellucci et al., 2010). It is also necessary to consider that SC may naturally vary according to culture, fashion and country (Castellucci et al., 2015). A 2 cm SC can be added to the popliteal height. Regarding Fig. 2.a, it shows that the seat height has to be larger than [(PHþ2)*Cos(30� )] to ensure the lower leg forms an angle less than 30� relative to the vertical, so that the student could sit comfortably while the thighs have sufficient support. For the maximum limit, the seat height has to be less than [(PHþ2)*Cos(5� )] to ensure the student’s feet have proper contact with the floor and avoid an increase in tissue pressure on the underside area of the thighs (Yanto et al., 2017). Therefore, the match criterion was defined according to Equation (1):
abduction angles. Chaffin and Anderson (1991) suggested that the minimum and maximum acceptable angles of the shoulder during writing are 0–25� for shoulder flexion and 0–20� for shoulder abduction (Fig. 2d). The match criterion would be determined by:
(1)
UDH should be at least 2 cm higher than knee height (but not higher than desk height plus its thickness) (Gouvali and Boudolos, 2006). The table thickness is assumed to be 2 cm.
�
�
(PH þ SC) Cos 30 � SH � (PH þ SC) Cos 5
SH þ EH � DH � SH þ 0.8517 EH þ 0.1483 SH or (PH þ SC)Cos30� þ EH � DH � (PH þ SC)Cos5� þ 0.8517 EH þ 0.1483 SH
2.2.5. Underneath desk height (UDH) Underneath desk height (UDH) should ensure that there is space between the knees and the underneath surface of the desk (Fig. 2f). UDH is considered appropriate when it is larger than SH þ TT (thigh thick ness) in order to permit leg movement. Parcells et al. (1999) proposed that UDH should be 2 cm higher than knee height (KH). (KH þ SC) þ2 � UDH
After applying Equation (1), a minimum (low) and maximum (high) limit will be defined.
(KH þ SC) þ2 � UDH � (PH þ SC)Cos5� þ 0.8517 EH þ 0.1483 SH - 2
2.2.2. Seat width (SW) To be able to relieve the pressure on the buttocks and to avoid discomfort and mobility restrictions, seat width (SW) should be larger than hip breadth (HB) (Castellucci et al., 2015). Gouvali and Boudolos (2006) recommended that SW should be at least 10% (to accommodate hip breadth) and at the most 30% (for space economy) larger than HB (Fig. 2b), which is determined by Equation (2): 1.10 HB � SW � 1.30 HB
(2)
0.60 SH � UEBR � 0.80 SH
(5.2)
(6)
2.2.7. Other criteria Height of Backrest (HBR): It is more appropriate to use the differ ence between subscapular and lumber height measures. Due to mea surement difficulties, this dimension was assumed to be 20 cm. Width of Backrest (WBR): Should(KH þ SC) þ2 � UDH � (PH þ SC)Cos5� þ 0.8517 EH þ 0.1483 SH - 2er breadth (SB) is the criterion for WBR. It is recommended that WBR be at least 10% larger than HB and at most 10% (for space) larger than SB.
(3)
1.1 HB � WBR �1.1 SB
(7)
Backrest Slope: ~5� slope is recommended. Desk Width (DW): Because of the same dimensions of the desk, seat and backrest width, the biggest one of these dimensions can be considered. Desk Depth (DD): It is important to mention that there are two di mensions, desk width (DW) and desk depth (DD), for which relation ships were not found in the literature. Castellucci et al. (2010) defined these dimensions according to functional criteria such as the need for available desk surface to perform school activities, for instance reading and writing. The dimension was 40 cm consisted of a sheet of A4 paper and two 5 cm free space.
2.2.4. Desk height (DH) If desk height (DH) is too low, students are forced to bend their torso forward, with their body weight supported by their arms. This will result in a kyphotic spinal posture with round shoulders (Castellucci et al., 2015). Elbow height (EH) (sitting) is the major criterion for DH. It is also accepted that EH can be considered as the minimum height of DH. The load on the spine is reduced significantly when the arms are supported on the desk. Several researchers (e.g. Castellucci et al., 2010) recommended that the desk should be 5 cm higher than EH. EH � DH � EH þ 5
(5.1)
2.2.6. Upper edge of backrest (UEBR) To facilitate mobility of the trunk and arms, the upper edge of the backrest (UEBR) needs to be adjusted below the scapula. Therefore, it has been recommended to keep the backrest lower than or at most on the upper edge of the scapula, which is 60%–80% shoulder height (SH) (Fig. 2e) (Gouvali and Boudolos, 2006; Dianat et al., 2013), as shown in Equation (6):
2.2.3. Seat depth (SD) Buttock popliteal length (BPL) is the anthropometric measure used to designate the size of the seat depth (SD) (Castellucci et al., 2015). Gouvali and Boudolos (2006) stated that SD should be at least 5 cm shorter than BPL. Other researchers explained that the seat depth should be designed for the fifth percentile of the BPL distribution so that the backrest of the seat can support the lumbar spine without compression of the popliteal surface. Parcells et al. (1999) defined the mismatch when SD is either > 95% or < 80% of BPL as illustrated in Fig. 2.c. Thus, the match criterion is established by Equation (3): 0.80 PBL �SD � 0.95 PBL
(4.2)
(4.1)
Parcells et al. (1999) considered that acceptable desk height depends not only on elbow-to-floor height, but also on shoulder flexion and 4
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International Journal of Industrial Ergonomics 74 (2019) 102864
3. Method
Table 2 Classroom furniture dimensions (cm).
3.1. Participants The participants of this study were 225 randomly selected under graduate students (68 female, 157 male) from nine departments of the Faculty of Engineering and Architecture. All students volunteered for the study. The objective and procedure to be followed were disclosed to each student prior to measurement. Permission to conduct the research was obtained from the faculty management. 3.2. Furniture measurement
Component
School furniture dimension
Existing Furniture
TSE Standard (2003)
Seat
Seat Height (SH) Seat Width (SW) Seat Depth (SD)
43.5 120 30
45 110 45
Backrest
Upper Edge of Backrest (UEBR) Lower Edge of Backrest (LEBR) Height of Backrest (HBR) Width of Backrest (WBR) Slope
35 15 20 120 3�
32 10 22 110 6�
Desk
Desk Height (DH) Desk Depth (DD) Desk Width (DW) Slope Underneath Desk Height (UDH)
75.5 39.5 120 4� 57.5
77 40 110 – 57.5
Four types of classroom furniture are used in the faculty. Double desk and chair (Fig. 3) is one type of commonly used classroom furniture. School furniture is produced by local furniture companies in accordance with the Standard of TSE (TSE, 2003) or a contract including the spec ifications and drawings of the furniture. However, this standard was published more than 15 years ago. Changes in student demographics and anthropometrics measures may mean the standard is out of date and no longer relevant. Thus, the existing furniture dimensions were measured with a standard measuring tape and given in Table 2.
breadth measures, two plaques were added to the backrest of the tool, one on the left to measure shoulder breadth and one on the right to measure hip breadth. While students were sitting in an erect position on the tool, measurements were taken on the left side for shoulder breadth and the right side for hip breadth.
3.3. Anthropometric measurement table
3.4. Procedure
In the related literature, there are different methods used for measuring body dimensions for the purpose of equipment design (Mokdad and Al-Ansari, 2009). The traditional anthropometric tools are simple and inexpensive. In this study, in order to provide reliable and quick measurement, especially in the sitting position, a measurement tool was designed (Fig. 4) and constructed to take seven anthropometric measures (Shoulder Height, Elbow Height, Buttock-Popliteal Length, Knee Height, Popliteal Height, Shoulder breadth, Hip Breadth) and two additional measures (Stature, Buttock-Knee Length). The dimension design of the measurement tool was based on studies in the literature. For the purpose of taking shoulder breadth and hip
The measurement process was carried out by a team of three project students: a measurer, a recorder, and an organizer to manage the pro cess. Before starting the process, they underwent a two-week training session, including a theoretical approach to the standard procedure for collecting the anthropometric measures accurately and precisely. They spent considerable time practicing measuring to achieve a high level of consistency. In this training, issues such as which point in the human body would be referred to for each measure, in which order the mea surements would be made, which clothing of the student (participant) would be allowed during measurements, how to register these in the form and who would do what (distribution of tasks) during
Fig. 3. Double desk and chair. 5
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International Journal of Industrial Ergonomics 74 (2019) 102864
match criterion equation, the established limits and anthropometric measures of the students were compared and three categories were defined in the case of the two-way equations (Castellucci et al., 2010). These three categories are: a) ‘‘Match’’ level, when the furniture dimensions are between the minimum and maximum limits; b) ‘‘High mismatch’’ level, when the maximum limit of the equation is lower than the furniture dimension, indicating that the furniture dimension is higher than needed; c) ‘‘Low mismatch’’ level, when the minimum limit of the equation is higher than the furniture dimension – in this case, the furniture dimension is lower than the recommended level (Castellucci et al., 2016). The existing classroom furniture includes the measures of two stu dents sitting with 20 cm space between them. Thus, the width of each seat, desk and backrest for a student was 50 cm. Match percentages between classroom furniture and anthropometric characteristics of undergraduate students are shown in Table 3. Seat height was appropriate for popliteal height in only 55.56% (66.18% for female and 50.95% for male) of the students. 30.88% of the female students and 0.64% of the male students had a higher seat (high mismatch), while only 2.94% of the female students had a seat that was too low (low mismatch). The mismatch percentage for seat width was 51.47% for female and 31.85% for male students. It is apparent that for only 8.92% of male students, seat width was narrower (low mismatch) than the limit mentioned criterion equation. The desk height was appropriate for the majority of the students (78.22%) (92.36% male and 45.59% female). It was too low (low mismatch) for 3.56%, while it was too high (high mismatch) for 18.22%. Underneath desk height was not appropriate for the majority of the students (62.22%). The percentage of mismatch increased constantly with higher year (grade) level for both female and male students, due to increasing knee height. 94.27% of male and 57.35% of female students were not suited to the upper edge of the backrest due to the fact that the backrest was lower than their scapula (low mismatch). The highest percentages of mismatch were found in the fourth/final year (85.54%). The width of the backrest was too large (high mismatch) for 45.78% (97.06% female, 23.57% male) of the students.
Fig. 4. Anthropometric measurement tool.
measurement were focused on. The measurement tool was placed in the Ergonomics Laboratory in the Department of Industrial Engineering. The participants were asked to come to the laboratory. In this study, seven required and three arbi trary measures were gathered from the participants. Stature (S) was measured with digital scale and the other nine measures were collected using the tool. The measurements were taken in accordance with the method described by Pheasant (1998). During the measurement process, the subjects were shoeless and wearing light clothing. While the participants were sitting erect on the measurement table with knees bent at 90� , Buttock popliteal length (BPL), Popliteal height (PH), Hip breadth (HB), Shoulder breadth (SB) were measured directly. Shoulder height (SH), Elbow height (EH), Buttock-knee length (BKL) and Knee height (KH) were taken with the anthropometry set and a measuring tape. The measures and demographic information, such as age, gender, year and department of each participant, were recorded on the measurement form.
Table 3 Match and mismatch percentages for students.
4. Results Descriptive statistics (mean, std. dev., maximum, minimum and percentile values) for female, male and all students are presented in Appendix B. The table shows that the mean stature is 178.00 cm (std. dev. 6.98) for male students and 163.22 cm (std. dev. 5.64) for female students. It is clear that the male students are, on average, 14.78 cm taller than female students. The mean popliteal height is 46.62 cm for male and 43.22 cm for female students. On the other hand, the buttockpopliteal length of male students is, on average, 3.88 cm longer than that of female students. It is concluded that all the anthropometric measures of male students are greater compared to female students. The differ ences vary from 0.96 cm (elbow height) to 14.78 cm (stature). 4.1. Mismatch for existing classroom furniture After replacing the existing classroom furniture dimension in each 6
Furniture Dimension
Matching
Female
Male
All
Seat Height
Match Low Mismatch High Mismatch
66.18 2.94 30.88
50.95 48.41 0.64
55.56 34.67 9.78
Seat Width
Match Low Mismatch High Mismatch
48.53 0 51.47
68.15 8.92 22.93
62.22 6.22 31.56
Seat Depth
Match Low Mismatch High Mismatch
0 100 0
0 100 0
0 100 0
Desk Height
Match Low Mismatch High Mismatch
45.59 1.47 52.94
92.36 4.46 3.18
78.22 3.56 18.22
Underneath Desk Height
Match Low Mismatch High Mismatch
91.18 8.82 0
14.65 85.35 0
37.78 62.22 0
Upper Edge of Backrest
Match Low Mismatch High Mismatch
42.65 57.35 0
5.73 94.27 0
16.89 83.11 0
Width of Backrest
Match Low Mismatch High Mismatch
2.94 0 97.06
68.15 8.28 23.57
48.44 5.78 45.78
International Journal of Industrial Ergonomics 74 (2019) 102864
E. Kahya
4.2. Optimum dimensions for classroom furniture
SHA ¼ (SHmin þ SHmax)/2 ¼ 42.68 cm
To overcome mismatch problems between anthropometric measures of students and school furniture dimensions, Van Niekerk et al. (2013) showed that there is an urgent need for chairs that are of different sizes or that are adjustable to provide a better student-chair fit. Castellucci et al. (2016) proposed that scalability, i.e. having the furniture available in many sizes, became a more real and cheaper solution. However, the aim should be focused on finding the optimum dimension that maxi mizes the match percentage. Regarding mismatch findings in this study, we suggest two alternative methods to find the optimum dimensions of classroom furniture.
SHA ~42.50 cm Type B: SHmin ¼ (PH%50þSC) Cos 30� , PH%50 ¼ 46.62 cm, SHmin ¼ 48.44 cm SHmax ¼ (PH%95þSC) Cos 5� , PH%95 ¼ 52.62 cm, SHmax ¼ 54.41 cm SHB ¼ (SHmin þ SHmax)/2 ¼ 51.43 cm SHB ~51.50 cm The match percentages were calculated for the dimensions of two proposed designs of classroom furniture, and displayed in Table 5. It can be seen from Table 5 that, compared to existing designs, the new proposed dimensions better match the students’ anthropometry, with about 30% for only two dimensions and lower than 3% for the others. It is important to highlight that Type A was appropriate for most students, with 84% for female and 36% for male students in terms of the seat height.
4.2.1. The best classroom furniture The match percentages were calculated for each possible dimension from minimum to maximum dimension to find the optimum dimension that maximizes the match percentage. The minimum/maximum possible dimension was produced from the minimum/maximum value of the related anthropometric measure. To illustrate the seat height; The criterion equation:
5. Discussion
(PH þ SC) Cos 30� � SH � (PH þ SC) Cos 5�
Nine anthropometric measures were taken from 68 female and 157 male students from nine departments of the Faculty of Engineering and Architecture to assess the mismatch between existing classroom furni ture dimensions and the anthropometric measures of the students. To our knowledge, this is the first study explaining mismatches between the dimensions of currently used classroom furniture and the anthropo metrics of university students in Turkey. Several studies have been conducted on the design of ergonomically correct furniture for university students in recent years in Turkey (e.g. Tunay et al., 2005; Dizdar and Okçu, 2007; Tunay and Melemez, 2008) and in other countries (Thariq et al., 2010; Hossain and Ahmed, 2010; Musa and Ismaila, 2014; Hoque et al., 2014; Bhuiyan and Hossain, 2015). First, the results of this study should be compared with the results from Turkey and other countries for several essential measures (stature and popliteal height). The stature measure was 161.3 cm for female and 175.13 cm for male students in the study conducted by Tunay et al. (2005), 161.50 cm for female and 172.77 for male students in the study conducted by Dizdar and Okçu (2007) and 161.8 cm for female and 174.9 for male students in the study conducted by Tunay and Melemez (2008). However, in this study the measure was found to be 163.22 cm for female and 178.00 cm for male students. Compared to the other studies conducted in the country, our results were 2–3 cm higher due to body development in the last ten years. The measure was 160.15 cm for female and 169.58 cm for male students in Nigeria (Musa and Ismaila, 2014) and 154.41 cm for female and 166.97 cm for male students in Bangladesh (Hoque et al., 2014). Popliteal height was 43.22 cm for fe male and 48.10 cm for male students, while the measure ranged from 42 to 45 cm in the studies conducted in Turkey. It was 38.51 cm for female and 42.87 cm for male students in Nigeria (Musa and Ismaila, 2014), and 40.34 cm for female and 44.38 cm for male students in Bangladesh (Hoque et al., 2014). Based on the results, it is clear that the measures of students in developing and developed countries are longer than those in other countries. Seat height is the starting point for the design of classroom furniture. Popliteal height is the criterion for seat height. The measure is 38.83 cm for 5% female and 52.93 cm for 95% male students. The difference is 14.10 cm, which could lead to health problems for the students using those desks. The results showed that the measure increases with higher year (grade) among both female and male students, with the lowest and highest measure were, on average, 45.75 cm in the first year (min 38 cm, max 55 cm) and 47.05 cm in the fourth year (min 40 cm, max 66 cm)
PHmin ¼ 38 cm (see Appendix B), SHmin ¼ (PHmin þ SC) Cos 30� , SHmin ¼ 34,64 cm PHmax ¼ 66 cm, SHmax ¼ (PHmax þ SC) Cos 5� , SHmax ¼ 67.74 cm The match percentage was determined for each seat height value from SHmin ~34,50 cm to SHmax ~ 68 cm, in increments of 0.5 cm. The optimum dimension that results in the biggest match percentage was found at 44.5 cm, with a percentage of 67.11%. Furniture dimensions maximizing match percentages are presented in Table 4. It can be seen from the table that the new proposed di mensions were better able to match the students’ anthropometry, with the percentages ranging from 55.56% to 100%. 4.2.2. Two types of classroom furniture Two types of classroom furniture (Type A and Type B) were inves tigated with the goal of maximizing the match percentage for each furniture dimension. We suggest an approach to find the optimum di mensions of the two types. The dimension for type A was the average of the limit (minimum and maximum) dimensions produced from 5% to 50% measures of the related anthropometric measure in the criterion equation. The limit dimensions for type B were obtained from 50% to 95% measures of the related anthropometric measure. For the seat height: Type A: SHmin ¼ (PH%5þSC) Cos 30� , PH%5 ¼ 40.64 cm, SHmin ¼ 36.93 cm SHmax ¼ (PH%50þSC) Cos 5� , PH%50 ¼ 46.62 cm, SHmax ¼ 48.43 cm Table 4 Furniture dimensions maximizing match percentages. Section
School furniture
Dimension (cm)
Match Percentage (%)
Seat
Seat Height (SH) Seat Width (SW) Seat Depth (SD)
44.5 48 45
67.11 81.33 78.22
Backrest
Upper Edge of Backrest (UEBR) Width of Backrest (WBR)
42
100
48
55.56
Desk
Desk Height (DH) Underneath Desk Height (UDH)
74 67
79.11 93.33
7
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International Journal of Industrial Ergonomics 74 (2019) 102864
Table 5 Proposed dimensions and percentages for two types of furniture. Component
School furniturae
Type A
Type B
Dimension (cm)
Match Percentage (%)
Dimension (cm)
Match Percentage (%)
Mismatch Percentage (%)
Seat
Seat Height (SH) Seat Width (SW) Seat Depth (SD)
42.50 45.50 43.00
50.67 71.11 67.11
51.50 51.00 48.50
16.88 22.67 30.67
32.44 3.11 2.22
Backrest
Upper Edge of Backrest (UEBR) Width of Backrest (WBR)
41.50 44.50
99.56 46.67
45.00 51.00
0.04 22.67
– 29.78
Desk
Desk Height (DH) Underneath Desk Height (UDH)
69.00 65.50
56.44 96.89
79.50 75.00
42.22 3.11
1.33 –
students. Hoque et al. (2014) stated that too low seat height increases the weight on the ischial tuberosities, whereas too high seat height leads to increased pressure at the popliteal fold (underside of knees), decreasing blood circulation and increasing pressure on the nerve. The seat height was appropriate for only 55.56% (66.18% for female and 50.95% for male students) of the students. The results indicated that the mismatch percentages increased with higher year among both fe male and male students, with the lowest and highest mismatch per centages being in the first year (33.33%) and final year (51.81%) students, respectively. The seat height for the furniture that maximized the match per centage was 43.5 cm, which resulting in a match percentage of 67.11%. However, the match percentage for both types of furniture was 67.55% (50.67% for Type A and 16.88% for Type B). The seat height measures were researched to provide the highest match percentage for all stu dents. It was found that three different furniture dimensions, SH1 ¼ 39.50 cm (24.45%), SH2 ¼ 45.50 cm (66.22%) and SH3 ¼ 52.50 cm (9.33%), maximized the match percentage (100%), but it is not desirable to have three types of furniture in a classroom. It has been reported that a seat height which is too low may lead to increased angles of lumbar flexion during sitting and predispose the seated person to increased risk of low back pain (Milanese and Grimmer, 2004; Pheasant, 1998). The match percentage for seat width dimension (50 cm) was 62.22% for all students. It is apparent that for 31.56% (51.47% for female and 22.93% for male) of students, the seat width dimension was higher. The results indicated that the mismatch percentage increased with year level (from 41.67% in the first year to 74.70% in the final year students). The existing classroom furniture setup is to seat two students at each desk. The dimension includes the measures of two students sitting with a 20 cm space between them. The seat width per student, 60 cm, was sufficient for all students, delivering 100% match and high mismatch percentages. The seat depth of the existing classroom furniture is 30 cm, which indicates that the chairs were too shallow (low mismatch) for all the students. If their seat is too shallow, the student will have the sensation of falling off the front of the chair as well as a lack of support for the lower thighs (Parcells et al., 1999). If the seat depth is significantly less than the buttock popliteal length, the student’s thighs would not be supported in the sitting posture (Pheasant, 1998). If the seat depth is greater than the buttock popliteal length, the student will not be able to use the backrest to support the lumbar spine without compression of the popliteal surface (Milanese and Grimmer, 2004). To avoid this, it is likely that the student will generally move their buttocks forward to ward the edge of the seat, as suggested by Panagiotopoulou et al. (2004). This position causes a slumped and khypotic posture (Panagiotopoulou et al., 2004). The current desk height, 75.50 cm, was appropriate for 78.22% of the students (92.36% for males and 45.59% for females), too low (low mismatch) for 3.56% and too high (high mismatch) for 18.22%. If the desk height is not right for the students, it is expected that too low desk height has a significant association with the occurrence of neck and
upper and lower back pain. If the desk is too low, the student will bend forward by spinal flexion while writing and reading. This situation will lead to a kyphotic spinal posture (Parcells et al., 1999). If the desk is too high, most of the students will have to flex their shoulders more than 25� and abduct them more than 20� in order to support their elbows on the desk. Considering the amount of time spent by a student in the sitting posture, this situation will lead to the excessive muscle strain on the student’s back and shoulders (Yanto et al., 2017). Currently, the backrest height (upper edge of back rest) (35 cm) was suited only to 16.89% of the students. It was too low (low mismatch) for 83.11%. The highest percentages of mismatch were found in the final year students (85.54%). A too low backrest has been significantly associated with higher back pain. A 42 cm backrest height was ideal for all students. Underneath desk height was appropriate for a few of the students (37.78%). The percentage of mismatch, 62.22%, included low mismatch. Inappropriate underneath desk height can cause discomfort, restrict leg movement and reduce mobility. Moreover, not enough un derneath desk height can cause knee injury due to frequent contact between the knees and the underside part on the desk. The percentages for the TSE (2003) standard classroom dimensions (see Table 2) showed that the majority of the students’ body measures matched with standard dimensions. The results indicated that some furniture dimensions (e.g. seat height, seat depth) proposed by TSE (2003) were much more appropriate than those of existing furniture. The measures had higher match percentages for seat height and depth. Nevertheless, the desk height was not appropriate for 39% of the stu dents, and the upper edge of the backrest and underneath desk height were too low for the majority of the students. Both types of furniture were proposed to maximize the match per centage for each school furniture dimension. The dimensions for the best classroom furniture (Table 3) based on the anthropometric data, as compared to existing designs, were better able to match the student’s anthropometry, with higher percentages. Larger backrest width (high mismatch) is not a problem for students, and the mismatch percentage for 48 cm is 91.11%, which is much more appropriate for the students. The match percentages for all the dimensions except for seat height were above 80%. Two types of classroom furniture (Type A and Type B) were investigated to maximize the match percentage for all the dimensions (Table 5). The match percentages were above 70% for four dimensions in the Type A and all the dimensions in two types above 90%, except for seat height. In general, Type A furniture was much more appropriate for the majority of the students in the first and second years. 6. Conclusions The finding of this study is that there is a considerable mismatch between anthropometric measures of university students and classroom furniture dimensions. The seat was too high for female students and too low for male students. Also, the seat depth was too narrow for both genders. These conditions may lead to increased pain and discomfort and tend to increase the risk for developing musculoskeletal problems amongst university students. According to the obtained data, it can be 8
International Journal of Industrial Ergonomics 74 (2019) 102864
E. Kahya
concluded that classroom furniture was not adequate for the student population. The findings of the research also clearly suggest that the design and allocation of classroom furniture for university students should be made by taking into consideration anthropometric assess ments to avoid unnecessary demands upon them. The dimensions for the proposed classroom furniture were more appropriate for all students, with the percentages of match ranging from 67.11% to 100% except for seat height. However, both Type A and Type B furniture in a classroom were much more appropriate for the students. The mismatch percentages of five dimensions were lower than 3%, while two (SH and WBR) were about 30%. To ensure more comfortable seating, researchers have recommended various approaches, one of which is the provision of desks and chairs of different dimensions in the same class. It is known that school furniture is designed using a “onesize-fits-all” approach, as adjustable furniture would increase the cost of production. However, placing two types of furniture in each classroom is an acceptable solution. The use of well-fitting classroom furniture is beneficial to the back muscles and also increases classroom comfort and makes learning easier. Four types of classroom furniture are used in the faculty. Double furniture under this study is one of commonly used types of classroom
furniture. All the seat, backrest and desk widths of this furniture are 120 cm. When 20 cm space between students is assumed, the width per student is 50 cm. All the analyses for the other three types of furniture were conducted by using 50 cm width of furniture. The results indicated that the existing amphitheatre furniture had higher seat height, nar rower seat width, shorter underneath desk height and higher seat-desk breadth. Mounted-desktop furniture had a narrow seat width and shorter upper and lower edges of backrest. Today’s anthropometric measures of students might change due to better quality of life, education, healthcare and nutritional status. Changes in means and variability of anthropometric dimensions not only need updates in current school furniture dimensions, but also a design policy to accommodate users with high variability (Yanto et al., 2017). The findings of this study highlight that further studies in classroom ergonomics would continue to revise the standards. Acknowledgement The author is grateful to the measurement team and all students who contributed to the study.
Appendix C. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.ergon.2019.102864. Appendix A. Description of Anthropometric Measures Measures
Descriptions
Stature (S) Shoulder Height (SH)
The vertical distance between the floor and the top of the head while the subject stands erect and looks straight forward. The vertical distance from the top of the shoulder at the acromion process to the surface on which the subject sits. The data is used in the design of workplaces, for the placement of equipment and for interior arrangements. The vertical distance from the bottom of the tip of the right elbow to the surface on which the subject sits. The data is used in interior arrangements, to determine armrest height with respect to workbenches, desks, tables and special equipment. The distance from the posterior surface of the buttock to the posterior surface of the knee or popliteal surface. The distance from the posterior surface of the buttock to the posterior surface of the knee or popliteal surface. The data is used in interior layout arrangements and in the design of sitting places. The vertical distance from the surface on which the foot rests to the top of the knee cap. The data is used in interior arrangements, determining underneath heights of desks, tables and benches. The vertical distance from the popliteal space (the posterior surface of the knee) to the surface on which the foot rests The horizontal distance between the maximum lateral protrusions of the right and left deltoid muscles. When the clothed subject is standing, the breadth of the shoulders is measured with a large anthropometric device The maximum breadth of the lower torso while the subject stands erect and looks straight forward. The data is used in interior arrangements, to size clothing, to design equipment, to determine the width of accommodation areas (seat, chair, stool, bar and office chairs, etc.).
Elbow Height (EH) Buttock-Knee Length (BKL) Buttock- Popliteal Length (BPL) Knee Height (KH) Popliteal Height (PH) Shoulder Breadth (SB) Hip Breadth (HB)
Appendix B. Anthropometric Measures of Students (cm) Measure
Gender
Min
%5
Mean
Std.Dev.
%95
Max
Stature (S)
Female Male All Female Male All Female Male All Female Male All Female Male All Female Male All Female
153.00 155.00 153.00 52.50 54.50 52.50 21.50 20.50 20.50 46.00 57.00 46.00 43.00 46.00 43.00 47.00 49.00 47.00 38.00
153.92 166.48 157.91 54.08 57.83 55.84 21.94 20.95 21.13 53.40 59.13 55.67 43.65 47.83 45.83 47.73 51.82 48.81 38.83
163.22 178.00 173.53 58.58 62.46 61.29 25.61 26.57 26.28 58.65 64.88 63.00 49.29 53.17 52.00 51.00 56.61 54.91 43.22
5.64 6.98 9.47 2.73 2.81 3.30 2.23 3.40 3.12 3.18 3.49 4.44 3.41 3.24 3.74 1.98 2.90 3.70 2.66
172.52 189.51 189.16 63.08 67.10 66.74 29.29 32.18 31.43 63.90 70.64 70.33 54.92 58.51 58.16 54.28 61.40 61.02 47.61
176.50 199.50 199.50 64.50 70.00 70.00 31.50 55.00 55.00 66.00 77.00 77.00 67.00 61.50 67.00 55.00 67.50 67.50 54.50
Shoulder Height (SH) Elbow Height (EH) Buttock-Knee Length (BKL) Buttock- Popliteal Length (BPL) Knee Height (KH) Popliteal Height (PH)
(continued on next page)
9
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International Journal of Industrial Ergonomics 74 (2019) 102864
(continued ) Measure
Shoulder Breadth (SB) Hip Breadth (HB)
Gender
Min
%5
Mean
Std.Dev.
%95
Max
Male All Female Male All Female Male All
40.50 38.00 37.00 38.00 37.00 35.00 34.50 34.50
43.26 40.64 36.74 42.34 38.14 35.00 35.84 35.25
48.10 46.62 40.32 47.41 45.26 38.42 40.60 39.94
2.93 3.63 2.17 3.07 4.32 2.07 2.89 2.85
52.93 52.61 43.89 52.48 52.39 41.84 45.36 44.63
66.00 66.00 45.50 58.00 58.00 43.50 49.00 49.00
References
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International Journal of Industrial Ergonomics journal homepage: http://www.elsevier.com/locate/ergon
Mismatch between classroom furniture and anthropometric measures of university students Emin Kahya Eskisehir Osmangazi University, Engineering and Architecture Faculty, Department of Industrial Engineering, Eskisehir, Turkey
A R T I C L E I N F O
A B S T R A C T
Keywords: Anthropometric measure Classroom furniture University student Mismatch
The appropriate design of tools, equipment and accessories for human body sizes, while meeting the social, cultural, economic and psychological needs of people, provides maximum benefit. This is crucial for students who spend most of their time using school furniture. The aim of the study is to investigate the mismatch between school furniture dimensions and students’ anthropometric measures. Nine anthropometric measures were taken of 225 students (68 female and 157 male) from nine departments of an engineering faculty using a specially designed measurement tool. The mismatch percentages between the existing classroom furniture dimensions and the anthropometric measures were determined using some well-known criterion equations. The results indicated a considerable mismatch: 44.45% for seat height, 100% for seat depth, and 21.28% for desk height. Two types of proposed classroom furniture achieved much higher percentage matches. The match percentages were above 70% for four dimensions for type A and above 95%, except for seat height and width of backrest, for all of the dimensions for both types. Relevance to industry: This study helps in establishing and motivating necessary further studies in classroom ergonomics in university settings.
1. Introduction University students spend a considerable part of their daily life (5–8 h per day) at school. While staying at school, they conduct most of their activities (e.g., reading and writing) sitting on school furniture. Considering the amount of time they spend in sedentary activities, stu dents are at particular risk of suffering from negative effects from poorly designed furniture. The use of ill-fitted furniture may increase the risk of developing musculoskeletal disorders. Furniture well designed to accommodate the anthropometric measures of students promotes cor rect sitting posture and reduces the incidence of musculoskeletal disorders. Mismatches between students’ anthropometric dimensions and furniture dimensions can affect classroom activities such as writing, reading and typing, causing pain in the back, shoulders, neck, legs and eyes (Fidelis et al., 2018). A number of studies (e.g. Murphy et al., 2004) have reported that the improper design of school furniture can have a significant effect on the posture of students. They have concluded that the use of poorly designed classroom furniture often results in discom fort as well as pain, especially in the neck, shoulders and upper and lower back. Mismatches between human anthropometric measures and
equipment dimensions are known to be a contributing factor in decreased productivity, discomfort, accidents, biomechanical stresses, fatigue, injuries, and cumulative traumas (Mandahawi et al., 2008). During the past few decades, there has been increasing concern about the design of school furniture and their match or mismatch to students’ anthropometric measures. Such mismatches have been re ported in several countries, including Greece (Gouvali and Boudolos, 2006), Iran (Dianat et al., 2013), Portugal (Assuncao et al., 2013), the United States (Parcells et al., 1999), India (Savanur et al., 2007) and Chile (Castellucci et al., 2010). A few studies (e.g. Castellucci et al., 2014; Castellucci et al., 2015) reviewed the literature describing the criterion equations for defining the mismatch between students and school furniture. The sample used for testing the different equations consisted of volunteer subjects from schools. Parcells et al. (1999) examined the mismatch between school furniture and students by measuring the anthropometric characteristics of American children. They reported that fewer than 20% of students could find acceptable chair/desk combinations. Gouvali and Boudolos (2006) study focused on the suitability of school furniture to the anthropometric measures of Greek children using combinational equa tions modified in accordance with principles proposed by the literature.
E-mail address: [email protected]. https://doi.org/10.1016/j.ergon.2019.102864 Received 30 January 2018; Received in revised form 17 August 2019; Accepted 4 October 2019 Available online 17 October 2019 0169-8141/© 2019 Elsevier B.V. All rights reserved.
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International Journal of Industrial Ergonomics 74 (2019) 102864
They determined that desk and seat heights were taller than the accepted limits for most children (81.8%), while seat depth was appropriate for only 38.7% of children. Castellucci et al. (2010) compared furniture dimensions in three different schools with the anthropometric characteristics of Chilean students in order to evaluate the potential mismatch between them. A study conducted by Dianat et al. (2013) evaluated the potential mismatch between classroom furniture dimensions and anthropometric measures of 978 Iranian high school students. Nine anthropometric measurements and five di mensions of the existing classroom furniture were measured and then compared (using match criterion equations) to identify any mismatch between them. The results indicated a considerable mismatch between the body measures of the students and the existing classroom furniture, with seat height (60.9%), seat width (54.7%) and desktop height (51.7%) being the dimensions with the highest level of mismatch. More studies have applied principles for the design of workplace furniture than for university furniture for students, although the situa tion in universities seems to be more serious (Hoque et al., 2014). It is necessary to draw attention to university furniture design. Several re searchers (e.g. Parcells et al., 1999) have incorporated measurements obtained from the elbow height in their designs to improve classroom furniture. In several countries, essential efforts have been made to introduce uniform classroom furniture design guidelines and standards. Recently, Thariq et al. (2010), Hossain and Ahmed (2010), Musa and Ismaila (2014), Hoque et al. (2014), Bhuiyan and Hossain (2015), and Fidelis et al. (2018) have presented some studies to design ergonomi cally correct furniture for university students. In a study conducted by Musa and Ismaila (2014), anthropometric measures were collected from 720 students of three randomly selected tertiary institutions in Nigeria, covering the age group between 17 and 27 years. The results indicated a substantial degree of mismatch between the students’ anthropometric measures and the furniture dimensions. The chairs were either too tall or too deep for the students. The data also revealed that the desks were too tall for most of the students. Hoque et al. (2014) evaluated the potential mismatch between university classroom furniture dimensions and anthropometric measures of 500 Bangladeshi university students. Fifteen anthropometric measures and nine dimensions from the existing classroom furniture were measured and then compared to identify po tential mismatch between them. The results indicated that the seat height was too tall. Bhuiyan and Hossain (2015) developed a method ology in designing ergonomic furniture used by the university students based on anthropometric measures and using an artificial neural network. Fidelis et al. (2018) determined the ergonomic suitability of classroom furniture at the Federal University of Technology, Akure, Nigeria. 261 randomly selected students (133 males and 128 females) participated in the study. The study revealed that 90% of the partici pants used desks that were too tall, 2% used desks that were too short and only 7% used desks with heights that fit their anthropometric measures. Several studies have been conducted on the design of ergonomically correct furniture for university students in Turkey. In a study conducted by Tunay et al. (2005), anthropometric measurements were obtained from 187 university students (45 female and 138 male) at Zonguldak Karaelmas University. The anthropometric measures were gathered to suggest the dimensions of the school furniture. Dizdar and Okçu (2007) aimed to evaluate the existing design of the classroom furniture used at Bozok University. The anthropometric measures of 143 students and the furniture dimensions were compared in order to identify any in compatibility between them. Tunay and Melemez (2008) carried out the necessary anthropometric measurements of classroom furniture used in Turkish higher education. Thirteen anthropometric measures from 1049 students were obtained while they are standing and sitting. Some studies have acknowledged the importance of appropriate classroom furniture used in university education in Turkey but, in recent years, there were a few studies establishing a relationship between school furniture and student anthropometric measures. This study is the
first attempt to evaluate the possible mismatch (using match criterion equations) between school furniture dimensions and anthropometric measures of university students and to propose the dimensions of two types of classroom furniture maximizing the match percentages. 2. Mismatch between classroom furniture and anthropometric measures 2.1. Measures School furniture and also potential mismatch equations are grouped according to the specific type of school furniture under consideration: ➢ Seat (including backrest) ➢ Desk ➢ Interactions between desk and seat. Table 1 shows a summary of relationships between school furniture dimensions and anthropometric measures. Anthropometric measures required for school furniture dimensions are displayed in Fig. 1. The measures are taken from students using an anthropometric de vice, in standing and sitting positions while they are without shoes, wearing casual dress. Definitions for nine measures (Pheasant, 1998; Tunay et al., 2005; Dizdar and Okçu, 2007; Oyewole et al., 2010; Cas tellucci et al., 2014, 2015; Hoque et al., 2014) are given in Appendix A. 2.2. Criterion equations for mismatch Applied anthropometric and ergonomic principles should be used to design and evaluate school furniture and to define the range in which each furniture dimension is considered appropriate. To identify a match or mismatch, anthropometric dimensions of each individual student are compared to the relative furniture dimensions (Dianat et al., 2013). Mismatch is defined as incompatibility between the dimensions of classroom furniture and the dimensions of a student’s body. All mismatch equations, one- and two-way, are considered (Castellucci et al., 2014). For the evaluation and design of classroom furniture, it is necessary to consider applied anthropometry and ergonomics principles and define an equation or equations enabling to determine the values of each furniture dimension; when it has a minimum and maximum limit, a two-way equation is considered appropriate and when it only has a maximum or a minimum limit, a one-way equation (e.g. Equation (5.1)) is the required option (Castellucci et al., 2010). Table 1 Relationship dimensions.
between
anthropometric
measures
school
furniture
Section
School furniture dimension
Anthropometric measures
Seat
Seat Height (SH) Seat Width (SW) Seat Depth (SD) Upper Edge of Backrest (UEBR)
Popliteal Height (PH) Hip Breadth (HB) Buttock Popliteal Length (BPL) Shoulder Height (SH), Subscapular Height(SSH) Lumber Height (LH), LEBR ¼ UEBR – HBR Lumber height Shoulder Breadth (SB) Functional criteria (~5� ) Popliteal Height (PH), Elbow Height (EH), Shoulder Height (SH) Functional criteria Functional criteria, Seat With (SW) Knee Height (KH) Thigh Thickness (TT), Knee Height (KH) Elbow Height (EH)
Backrest
Lower Edge of Backrest (LEBR)
Desk
Height of Backrest (HBR) Width of Backrest (WBR) Slope Desk Height (DH) Desk Depth (DD) Desk Width (DW)
Interaction
Underneath Desk Height (UDH) Seat to Desk Clearance (SDC) Seat to Desk Height (SDH)
2
and
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International Journal of Industrial Ergonomics 74 (2019) 102864
Fig. 1. Anthropometric measures.
In the literature, there is a considerable variability in the equations that can be used to test the mismatch between anthropometric measures and furniture dimensions (Castellucci et al., 2016). In this study, seven furniture dimensions were evaluated, applying the most commonly used and recommended equations (e.g. Dianat et al., 2013; Castellucci et al., 2015).
2.2.1. Seat height (SH) Most researchers have concluded that popliteal height (PH) should be higher than seat height (SH) (Parcells et al., 1999; Mokdad and Al-Ansari, 2009; Dianat et al., 2013); otherwise most students will be unable to rest their feet on the floor properly, thus generating increased tissue pressure on the posterior surface of the knee (Castellucci et al.,
Fig. 2. Correlation between anthropometry and school furniture dimensions (Yanto et al., 2017). 3
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International Journal of Industrial Ergonomics 74 (2019) 102864
2015). Seat height allows the knee to be flexed so that the lower leg forms a maximum angle of 30� relative to the vertical axis (Molenbroek et al., 2003). As shown in Equation (1), seat height needs to be lower than popliteal height so that the lower leg forms a 5–30� angle relative to the vertical and the shin-thigh angle is between 95� and 120� (Gouvali and Boudolos, 2006). In all studies, the anthropometric measures have been made without shoes. Shoe correction (SC) is a height between 2 cm (Gouvali and Boudolos, 2006) and 3 cm (Castellucci et al., 2010). It is also necessary to consider that SC may naturally vary according to culture, fashion and country (Castellucci et al., 2015). A 2 cm SC can be added to the popliteal height. Regarding Fig. 2.a, it shows that the seat height has to be larger than [(PHþ2)*Cos(30� )] to ensure the lower leg forms an angle less than 30� relative to the vertical, so that the student could sit comfortably while the thighs have sufficient support. For the maximum limit, the seat height has to be less than [(PHþ2)*Cos(5� )] to ensure the student’s feet have proper contact with the floor and avoid an increase in tissue pressure on the underside area of the thighs (Yanto et al., 2017). Therefore, the match criterion was defined according to Equation (1):
abduction angles. Chaffin and Anderson (1991) suggested that the minimum and maximum acceptable angles of the shoulder during writing are 0–25� for shoulder flexion and 0–20� for shoulder abduction (Fig. 2d). The match criterion would be determined by:
(1)
UDH should be at least 2 cm higher than knee height (but not higher than desk height plus its thickness) (Gouvali and Boudolos, 2006). The table thickness is assumed to be 2 cm.
�
�
(PH þ SC) Cos 30 � SH � (PH þ SC) Cos 5
SH þ EH � DH � SH þ 0.8517 EH þ 0.1483 SH or (PH þ SC)Cos30� þ EH � DH � (PH þ SC)Cos5� þ 0.8517 EH þ 0.1483 SH
2.2.5. Underneath desk height (UDH) Underneath desk height (UDH) should ensure that there is space between the knees and the underneath surface of the desk (Fig. 2f). UDH is considered appropriate when it is larger than SH þ TT (thigh thick ness) in order to permit leg movement. Parcells et al. (1999) proposed that UDH should be 2 cm higher than knee height (KH). (KH þ SC) þ2 � UDH
After applying Equation (1), a minimum (low) and maximum (high) limit will be defined.
(KH þ SC) þ2 � UDH � (PH þ SC)Cos5� þ 0.8517 EH þ 0.1483 SH - 2
2.2.2. Seat width (SW) To be able to relieve the pressure on the buttocks and to avoid discomfort and mobility restrictions, seat width (SW) should be larger than hip breadth (HB) (Castellucci et al., 2015). Gouvali and Boudolos (2006) recommended that SW should be at least 10% (to accommodate hip breadth) and at the most 30% (for space economy) larger than HB (Fig. 2b), which is determined by Equation (2): 1.10 HB � SW � 1.30 HB
(2)
0.60 SH � UEBR � 0.80 SH
(5.2)
(6)
2.2.7. Other criteria Height of Backrest (HBR): It is more appropriate to use the differ ence between subscapular and lumber height measures. Due to mea surement difficulties, this dimension was assumed to be 20 cm. Width of Backrest (WBR): Should(KH þ SC) þ2 � UDH � (PH þ SC)Cos5� þ 0.8517 EH þ 0.1483 SH - 2er breadth (SB) is the criterion for WBR. It is recommended that WBR be at least 10% larger than HB and at most 10% (for space) larger than SB.
(3)
1.1 HB � WBR �1.1 SB
(7)
Backrest Slope: ~5� slope is recommended. Desk Width (DW): Because of the same dimensions of the desk, seat and backrest width, the biggest one of these dimensions can be considered. Desk Depth (DD): It is important to mention that there are two di mensions, desk width (DW) and desk depth (DD), for which relation ships were not found in the literature. Castellucci et al. (2010) defined these dimensions according to functional criteria such as the need for available desk surface to perform school activities, for instance reading and writing. The dimension was 40 cm consisted of a sheet of A4 paper and two 5 cm free space.
2.2.4. Desk height (DH) If desk height (DH) is too low, students are forced to bend their torso forward, with their body weight supported by their arms. This will result in a kyphotic spinal posture with round shoulders (Castellucci et al., 2015). Elbow height (EH) (sitting) is the major criterion for DH. It is also accepted that EH can be considered as the minimum height of DH. The load on the spine is reduced significantly when the arms are supported on the desk. Several researchers (e.g. Castellucci et al., 2010) recommended that the desk should be 5 cm higher than EH. EH � DH � EH þ 5
(5.1)
2.2.6. Upper edge of backrest (UEBR) To facilitate mobility of the trunk and arms, the upper edge of the backrest (UEBR) needs to be adjusted below the scapula. Therefore, it has been recommended to keep the backrest lower than or at most on the upper edge of the scapula, which is 60%–80% shoulder height (SH) (Fig. 2e) (Gouvali and Boudolos, 2006; Dianat et al., 2013), as shown in Equation (6):
2.2.3. Seat depth (SD) Buttock popliteal length (BPL) is the anthropometric measure used to designate the size of the seat depth (SD) (Castellucci et al., 2015). Gouvali and Boudolos (2006) stated that SD should be at least 5 cm shorter than BPL. Other researchers explained that the seat depth should be designed for the fifth percentile of the BPL distribution so that the backrest of the seat can support the lumbar spine without compression of the popliteal surface. Parcells et al. (1999) defined the mismatch when SD is either > 95% or < 80% of BPL as illustrated in Fig. 2.c. Thus, the match criterion is established by Equation (3): 0.80 PBL �SD � 0.95 PBL
(4.2)
(4.1)
Parcells et al. (1999) considered that acceptable desk height depends not only on elbow-to-floor height, but also on shoulder flexion and 4
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International Journal of Industrial Ergonomics 74 (2019) 102864
3. Method
Table 2 Classroom furniture dimensions (cm).
3.1. Participants The participants of this study were 225 randomly selected under graduate students (68 female, 157 male) from nine departments of the Faculty of Engineering and Architecture. All students volunteered for the study. The objective and procedure to be followed were disclosed to each student prior to measurement. Permission to conduct the research was obtained from the faculty management. 3.2. Furniture measurement
Component
School furniture dimension
Existing Furniture
TSE Standard (2003)
Seat
Seat Height (SH) Seat Width (SW) Seat Depth (SD)
43.5 120 30
45 110 45
Backrest
Upper Edge of Backrest (UEBR) Lower Edge of Backrest (LEBR) Height of Backrest (HBR) Width of Backrest (WBR) Slope
35 15 20 120 3�
32 10 22 110 6�
Desk
Desk Height (DH) Desk Depth (DD) Desk Width (DW) Slope Underneath Desk Height (UDH)
75.5 39.5 120 4� 57.5
77 40 110 – 57.5
Four types of classroom furniture are used in the faculty. Double desk and chair (Fig. 3) is one type of commonly used classroom furniture. School furniture is produced by local furniture companies in accordance with the Standard of TSE (TSE, 2003) or a contract including the spec ifications and drawings of the furniture. However, this standard was published more than 15 years ago. Changes in student demographics and anthropometrics measures may mean the standard is out of date and no longer relevant. Thus, the existing furniture dimensions were measured with a standard measuring tape and given in Table 2.
breadth measures, two plaques were added to the backrest of the tool, one on the left to measure shoulder breadth and one on the right to measure hip breadth. While students were sitting in an erect position on the tool, measurements were taken on the left side for shoulder breadth and the right side for hip breadth.
3.3. Anthropometric measurement table
3.4. Procedure
In the related literature, there are different methods used for measuring body dimensions for the purpose of equipment design (Mokdad and Al-Ansari, 2009). The traditional anthropometric tools are simple and inexpensive. In this study, in order to provide reliable and quick measurement, especially in the sitting position, a measurement tool was designed (Fig. 4) and constructed to take seven anthropometric measures (Shoulder Height, Elbow Height, Buttock-Popliteal Length, Knee Height, Popliteal Height, Shoulder breadth, Hip Breadth) and two additional measures (Stature, Buttock-Knee Length). The dimension design of the measurement tool was based on studies in the literature. For the purpose of taking shoulder breadth and hip
The measurement process was carried out by a team of three project students: a measurer, a recorder, and an organizer to manage the pro cess. Before starting the process, they underwent a two-week training session, including a theoretical approach to the standard procedure for collecting the anthropometric measures accurately and precisely. They spent considerable time practicing measuring to achieve a high level of consistency. In this training, issues such as which point in the human body would be referred to for each measure, in which order the mea surements would be made, which clothing of the student (participant) would be allowed during measurements, how to register these in the form and who would do what (distribution of tasks) during
Fig. 3. Double desk and chair. 5
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International Journal of Industrial Ergonomics 74 (2019) 102864
match criterion equation, the established limits and anthropometric measures of the students were compared and three categories were defined in the case of the two-way equations (Castellucci et al., 2010). These three categories are: a) ‘‘Match’’ level, when the furniture dimensions are between the minimum and maximum limits; b) ‘‘High mismatch’’ level, when the maximum limit of the equation is lower than the furniture dimension, indicating that the furniture dimension is higher than needed; c) ‘‘Low mismatch’’ level, when the minimum limit of the equation is higher than the furniture dimension – in this case, the furniture dimension is lower than the recommended level (Castellucci et al., 2016). The existing classroom furniture includes the measures of two stu dents sitting with 20 cm space between them. Thus, the width of each seat, desk and backrest for a student was 50 cm. Match percentages between classroom furniture and anthropometric characteristics of undergraduate students are shown in Table 3. Seat height was appropriate for popliteal height in only 55.56% (66.18% for female and 50.95% for male) of the students. 30.88% of the female students and 0.64% of the male students had a higher seat (high mismatch), while only 2.94% of the female students had a seat that was too low (low mismatch). The mismatch percentage for seat width was 51.47% for female and 31.85% for male students. It is apparent that for only 8.92% of male students, seat width was narrower (low mismatch) than the limit mentioned criterion equation. The desk height was appropriate for the majority of the students (78.22%) (92.36% male and 45.59% female). It was too low (low mismatch) for 3.56%, while it was too high (high mismatch) for 18.22%. Underneath desk height was not appropriate for the majority of the students (62.22%). The percentage of mismatch increased constantly with higher year (grade) level for both female and male students, due to increasing knee height. 94.27% of male and 57.35% of female students were not suited to the upper edge of the backrest due to the fact that the backrest was lower than their scapula (low mismatch). The highest percentages of mismatch were found in the fourth/final year (85.54%). The width of the backrest was too large (high mismatch) for 45.78% (97.06% female, 23.57% male) of the students.
Fig. 4. Anthropometric measurement tool.
measurement were focused on. The measurement tool was placed in the Ergonomics Laboratory in the Department of Industrial Engineering. The participants were asked to come to the laboratory. In this study, seven required and three arbi trary measures were gathered from the participants. Stature (S) was measured with digital scale and the other nine measures were collected using the tool. The measurements were taken in accordance with the method described by Pheasant (1998). During the measurement process, the subjects were shoeless and wearing light clothing. While the participants were sitting erect on the measurement table with knees bent at 90� , Buttock popliteal length (BPL), Popliteal height (PH), Hip breadth (HB), Shoulder breadth (SB) were measured directly. Shoulder height (SH), Elbow height (EH), Buttock-knee length (BKL) and Knee height (KH) were taken with the anthropometry set and a measuring tape. The measures and demographic information, such as age, gender, year and department of each participant, were recorded on the measurement form.
Table 3 Match and mismatch percentages for students.
4. Results Descriptive statistics (mean, std. dev., maximum, minimum and percentile values) for female, male and all students are presented in Appendix B. The table shows that the mean stature is 178.00 cm (std. dev. 6.98) for male students and 163.22 cm (std. dev. 5.64) for female students. It is clear that the male students are, on average, 14.78 cm taller than female students. The mean popliteal height is 46.62 cm for male and 43.22 cm for female students. On the other hand, the buttockpopliteal length of male students is, on average, 3.88 cm longer than that of female students. It is concluded that all the anthropometric measures of male students are greater compared to female students. The differ ences vary from 0.96 cm (elbow height) to 14.78 cm (stature). 4.1. Mismatch for existing classroom furniture After replacing the existing classroom furniture dimension in each 6
Furniture Dimension
Matching
Female
Male
All
Seat Height
Match Low Mismatch High Mismatch
66.18 2.94 30.88
50.95 48.41 0.64
55.56 34.67 9.78
Seat Width
Match Low Mismatch High Mismatch
48.53 0 51.47
68.15 8.92 22.93
62.22 6.22 31.56
Seat Depth
Match Low Mismatch High Mismatch
0 100 0
0 100 0
0 100 0
Desk Height
Match Low Mismatch High Mismatch
45.59 1.47 52.94
92.36 4.46 3.18
78.22 3.56 18.22
Underneath Desk Height
Match Low Mismatch High Mismatch
91.18 8.82 0
14.65 85.35 0
37.78 62.22 0
Upper Edge of Backrest
Match Low Mismatch High Mismatch
42.65 57.35 0
5.73 94.27 0
16.89 83.11 0
Width of Backrest
Match Low Mismatch High Mismatch
2.94 0 97.06
68.15 8.28 23.57
48.44 5.78 45.78
International Journal of Industrial Ergonomics 74 (2019) 102864
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4.2. Optimum dimensions for classroom furniture
SHA ¼ (SHmin þ SHmax)/2 ¼ 42.68 cm
To overcome mismatch problems between anthropometric measures of students and school furniture dimensions, Van Niekerk et al. (2013) showed that there is an urgent need for chairs that are of different sizes or that are adjustable to provide a better student-chair fit. Castellucci et al. (2016) proposed that scalability, i.e. having the furniture available in many sizes, became a more real and cheaper solution. However, the aim should be focused on finding the optimum dimension that maxi mizes the match percentage. Regarding mismatch findings in this study, we suggest two alternative methods to find the optimum dimensions of classroom furniture.
SHA ~42.50 cm Type B: SHmin ¼ (PH%50þSC) Cos 30� , PH%50 ¼ 46.62 cm, SHmin ¼ 48.44 cm SHmax ¼ (PH%95þSC) Cos 5� , PH%95 ¼ 52.62 cm, SHmax ¼ 54.41 cm SHB ¼ (SHmin þ SHmax)/2 ¼ 51.43 cm SHB ~51.50 cm The match percentages were calculated for the dimensions of two proposed designs of classroom furniture, and displayed in Table 5. It can be seen from Table 5 that, compared to existing designs, the new proposed dimensions better match the students’ anthropometry, with about 30% for only two dimensions and lower than 3% for the others. It is important to highlight that Type A was appropriate for most students, with 84% for female and 36% for male students in terms of the seat height.
4.2.1. The best classroom furniture The match percentages were calculated for each possible dimension from minimum to maximum dimension to find the optimum dimension that maximizes the match percentage. The minimum/maximum possible dimension was produced from the minimum/maximum value of the related anthropometric measure. To illustrate the seat height; The criterion equation:
5. Discussion
(PH þ SC) Cos 30� � SH � (PH þ SC) Cos 5�
Nine anthropometric measures were taken from 68 female and 157 male students from nine departments of the Faculty of Engineering and Architecture to assess the mismatch between existing classroom furni ture dimensions and the anthropometric measures of the students. To our knowledge, this is the first study explaining mismatches between the dimensions of currently used classroom furniture and the anthropo metrics of university students in Turkey. Several studies have been conducted on the design of ergonomically correct furniture for university students in recent years in Turkey (e.g. Tunay et al., 2005; Dizdar and Okçu, 2007; Tunay and Melemez, 2008) and in other countries (Thariq et al., 2010; Hossain and Ahmed, 2010; Musa and Ismaila, 2014; Hoque et al., 2014; Bhuiyan and Hossain, 2015). First, the results of this study should be compared with the results from Turkey and other countries for several essential measures (stature and popliteal height). The stature measure was 161.3 cm for female and 175.13 cm for male students in the study conducted by Tunay et al. (2005), 161.50 cm for female and 172.77 for male students in the study conducted by Dizdar and Okçu (2007) and 161.8 cm for female and 174.9 for male students in the study conducted by Tunay and Melemez (2008). However, in this study the measure was found to be 163.22 cm for female and 178.00 cm for male students. Compared to the other studies conducted in the country, our results were 2–3 cm higher due to body development in the last ten years. The measure was 160.15 cm for female and 169.58 cm for male students in Nigeria (Musa and Ismaila, 2014) and 154.41 cm for female and 166.97 cm for male students in Bangladesh (Hoque et al., 2014). Popliteal height was 43.22 cm for fe male and 48.10 cm for male students, while the measure ranged from 42 to 45 cm in the studies conducted in Turkey. It was 38.51 cm for female and 42.87 cm for male students in Nigeria (Musa and Ismaila, 2014), and 40.34 cm for female and 44.38 cm for male students in Bangladesh (Hoque et al., 2014). Based on the results, it is clear that the measures of students in developing and developed countries are longer than those in other countries. Seat height is the starting point for the design of classroom furniture. Popliteal height is the criterion for seat height. The measure is 38.83 cm for 5% female and 52.93 cm for 95% male students. The difference is 14.10 cm, which could lead to health problems for the students using those desks. The results showed that the measure increases with higher year (grade) among both female and male students, with the lowest and highest measure were, on average, 45.75 cm in the first year (min 38 cm, max 55 cm) and 47.05 cm in the fourth year (min 40 cm, max 66 cm)
PHmin ¼ 38 cm (see Appendix B), SHmin ¼ (PHmin þ SC) Cos 30� , SHmin ¼ 34,64 cm PHmax ¼ 66 cm, SHmax ¼ (PHmax þ SC) Cos 5� , SHmax ¼ 67.74 cm The match percentage was determined for each seat height value from SHmin ~34,50 cm to SHmax ~ 68 cm, in increments of 0.5 cm. The optimum dimension that results in the biggest match percentage was found at 44.5 cm, with a percentage of 67.11%. Furniture dimensions maximizing match percentages are presented in Table 4. It can be seen from the table that the new proposed di mensions were better able to match the students’ anthropometry, with the percentages ranging from 55.56% to 100%. 4.2.2. Two types of classroom furniture Two types of classroom furniture (Type A and Type B) were inves tigated with the goal of maximizing the match percentage for each furniture dimension. We suggest an approach to find the optimum di mensions of the two types. The dimension for type A was the average of the limit (minimum and maximum) dimensions produced from 5% to 50% measures of the related anthropometric measure in the criterion equation. The limit dimensions for type B were obtained from 50% to 95% measures of the related anthropometric measure. For the seat height: Type A: SHmin ¼ (PH%5þSC) Cos 30� , PH%5 ¼ 40.64 cm, SHmin ¼ 36.93 cm SHmax ¼ (PH%50þSC) Cos 5� , PH%50 ¼ 46.62 cm, SHmax ¼ 48.43 cm Table 4 Furniture dimensions maximizing match percentages. Section
School furniture
Dimension (cm)
Match Percentage (%)
Seat
Seat Height (SH) Seat Width (SW) Seat Depth (SD)
44.5 48 45
67.11 81.33 78.22
Backrest
Upper Edge of Backrest (UEBR) Width of Backrest (WBR)
42
100
48
55.56
Desk
Desk Height (DH) Underneath Desk Height (UDH)
74 67
79.11 93.33
7
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International Journal of Industrial Ergonomics 74 (2019) 102864
Table 5 Proposed dimensions and percentages for two types of furniture. Component
School furniturae
Type A
Type B
Dimension (cm)
Match Percentage (%)
Dimension (cm)
Match Percentage (%)
Mismatch Percentage (%)
Seat
Seat Height (SH) Seat Width (SW) Seat Depth (SD)
42.50 45.50 43.00
50.67 71.11 67.11
51.50 51.00 48.50
16.88 22.67 30.67
32.44 3.11 2.22
Backrest
Upper Edge of Backrest (UEBR) Width of Backrest (WBR)
41.50 44.50
99.56 46.67
45.00 51.00
0.04 22.67
– 29.78
Desk
Desk Height (DH) Underneath Desk Height (UDH)
69.00 65.50
56.44 96.89
79.50 75.00
42.22 3.11
1.33 –
students. Hoque et al. (2014) stated that too low seat height increases the weight on the ischial tuberosities, whereas too high seat height leads to increased pressure at the popliteal fold (underside of knees), decreasing blood circulation and increasing pressure on the nerve. The seat height was appropriate for only 55.56% (66.18% for female and 50.95% for male students) of the students. The results indicated that the mismatch percentages increased with higher year among both fe male and male students, with the lowest and highest mismatch per centages being in the first year (33.33%) and final year (51.81%) students, respectively. The seat height for the furniture that maximized the match per centage was 43.5 cm, which resulting in a match percentage of 67.11%. However, the match percentage for both types of furniture was 67.55% (50.67% for Type A and 16.88% for Type B). The seat height measures were researched to provide the highest match percentage for all stu dents. It was found that three different furniture dimensions, SH1 ¼ 39.50 cm (24.45%), SH2 ¼ 45.50 cm (66.22%) and SH3 ¼ 52.50 cm (9.33%), maximized the match percentage (100%), but it is not desirable to have three types of furniture in a classroom. It has been reported that a seat height which is too low may lead to increased angles of lumbar flexion during sitting and predispose the seated person to increased risk of low back pain (Milanese and Grimmer, 2004; Pheasant, 1998). The match percentage for seat width dimension (50 cm) was 62.22% for all students. It is apparent that for 31.56% (51.47% for female and 22.93% for male) of students, the seat width dimension was higher. The results indicated that the mismatch percentage increased with year level (from 41.67% in the first year to 74.70% in the final year students). The existing classroom furniture setup is to seat two students at each desk. The dimension includes the measures of two students sitting with a 20 cm space between them. The seat width per student, 60 cm, was sufficient for all students, delivering 100% match and high mismatch percentages. The seat depth of the existing classroom furniture is 30 cm, which indicates that the chairs were too shallow (low mismatch) for all the students. If their seat is too shallow, the student will have the sensation of falling off the front of the chair as well as a lack of support for the lower thighs (Parcells et al., 1999). If the seat depth is significantly less than the buttock popliteal length, the student’s thighs would not be supported in the sitting posture (Pheasant, 1998). If the seat depth is greater than the buttock popliteal length, the student will not be able to use the backrest to support the lumbar spine without compression of the popliteal surface (Milanese and Grimmer, 2004). To avoid this, it is likely that the student will generally move their buttocks forward to ward the edge of the seat, as suggested by Panagiotopoulou et al. (2004). This position causes a slumped and khypotic posture (Panagiotopoulou et al., 2004). The current desk height, 75.50 cm, was appropriate for 78.22% of the students (92.36% for males and 45.59% for females), too low (low mismatch) for 3.56% and too high (high mismatch) for 18.22%. If the desk height is not right for the students, it is expected that too low desk height has a significant association with the occurrence of neck and
upper and lower back pain. If the desk is too low, the student will bend forward by spinal flexion while writing and reading. This situation will lead to a kyphotic spinal posture (Parcells et al., 1999). If the desk is too high, most of the students will have to flex their shoulders more than 25� and abduct them more than 20� in order to support their elbows on the desk. Considering the amount of time spent by a student in the sitting posture, this situation will lead to the excessive muscle strain on the student’s back and shoulders (Yanto et al., 2017). Currently, the backrest height (upper edge of back rest) (35 cm) was suited only to 16.89% of the students. It was too low (low mismatch) for 83.11%. The highest percentages of mismatch were found in the final year students (85.54%). A too low backrest has been significantly associated with higher back pain. A 42 cm backrest height was ideal for all students. Underneath desk height was appropriate for a few of the students (37.78%). The percentage of mismatch, 62.22%, included low mismatch. Inappropriate underneath desk height can cause discomfort, restrict leg movement and reduce mobility. Moreover, not enough un derneath desk height can cause knee injury due to frequent contact between the knees and the underside part on the desk. The percentages for the TSE (2003) standard classroom dimensions (see Table 2) showed that the majority of the students’ body measures matched with standard dimensions. The results indicated that some furniture dimensions (e.g. seat height, seat depth) proposed by TSE (2003) were much more appropriate than those of existing furniture. The measures had higher match percentages for seat height and depth. Nevertheless, the desk height was not appropriate for 39% of the stu dents, and the upper edge of the backrest and underneath desk height were too low for the majority of the students. Both types of furniture were proposed to maximize the match per centage for each school furniture dimension. The dimensions for the best classroom furniture (Table 3) based on the anthropometric data, as compared to existing designs, were better able to match the student’s anthropometry, with higher percentages. Larger backrest width (high mismatch) is not a problem for students, and the mismatch percentage for 48 cm is 91.11%, which is much more appropriate for the students. The match percentages for all the dimensions except for seat height were above 80%. Two types of classroom furniture (Type A and Type B) were investigated to maximize the match percentage for all the dimensions (Table 5). The match percentages were above 70% for four dimensions in the Type A and all the dimensions in two types above 90%, except for seat height. In general, Type A furniture was much more appropriate for the majority of the students in the first and second years. 6. Conclusions The finding of this study is that there is a considerable mismatch between anthropometric measures of university students and classroom furniture dimensions. The seat was too high for female students and too low for male students. Also, the seat depth was too narrow for both genders. These conditions may lead to increased pain and discomfort and tend to increase the risk for developing musculoskeletal problems amongst university students. According to the obtained data, it can be 8
International Journal of Industrial Ergonomics 74 (2019) 102864
E. Kahya
concluded that classroom furniture was not adequate for the student population. The findings of the research also clearly suggest that the design and allocation of classroom furniture for university students should be made by taking into consideration anthropometric assess ments to avoid unnecessary demands upon them. The dimensions for the proposed classroom furniture were more appropriate for all students, with the percentages of match ranging from 67.11% to 100% except for seat height. However, both Type A and Type B furniture in a classroom were much more appropriate for the students. The mismatch percentages of five dimensions were lower than 3%, while two (SH and WBR) were about 30%. To ensure more comfortable seating, researchers have recommended various approaches, one of which is the provision of desks and chairs of different dimensions in the same class. It is known that school furniture is designed using a “onesize-fits-all” approach, as adjustable furniture would increase the cost of production. However, placing two types of furniture in each classroom is an acceptable solution. The use of well-fitting classroom furniture is beneficial to the back muscles and also increases classroom comfort and makes learning easier. Four types of classroom furniture are used in the faculty. Double furniture under this study is one of commonly used types of classroom
furniture. All the seat, backrest and desk widths of this furniture are 120 cm. When 20 cm space between students is assumed, the width per student is 50 cm. All the analyses for the other three types of furniture were conducted by using 50 cm width of furniture. The results indicated that the existing amphitheatre furniture had higher seat height, nar rower seat width, shorter underneath desk height and higher seat-desk breadth. Mounted-desktop furniture had a narrow seat width and shorter upper and lower edges of backrest. Today’s anthropometric measures of students might change due to better quality of life, education, healthcare and nutritional status. Changes in means and variability of anthropometric dimensions not only need updates in current school furniture dimensions, but also a design policy to accommodate users with high variability (Yanto et al., 2017). The findings of this study highlight that further studies in classroom ergonomics would continue to revise the standards. Acknowledgement The author is grateful to the measurement team and all students who contributed to the study.
Appendix C. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.ergon.2019.102864. Appendix A. Description of Anthropometric Measures Measures
Descriptions
Stature (S) Shoulder Height (SH)
The vertical distance between the floor and the top of the head while the subject stands erect and looks straight forward. The vertical distance from the top of the shoulder at the acromion process to the surface on which the subject sits. The data is used in the design of workplaces, for the placement of equipment and for interior arrangements. The vertical distance from the bottom of the tip of the right elbow to the surface on which the subject sits. The data is used in interior arrangements, to determine armrest height with respect to workbenches, desks, tables and special equipment. The distance from the posterior surface of the buttock to the posterior surface of the knee or popliteal surface. The distance from the posterior surface of the buttock to the posterior surface of the knee or popliteal surface. The data is used in interior layout arrangements and in the design of sitting places. The vertical distance from the surface on which the foot rests to the top of the knee cap. The data is used in interior arrangements, determining underneath heights of desks, tables and benches. The vertical distance from the popliteal space (the posterior surface of the knee) to the surface on which the foot rests The horizontal distance between the maximum lateral protrusions of the right and left deltoid muscles. When the clothed subject is standing, the breadth of the shoulders is measured with a large anthropometric device The maximum breadth of the lower torso while the subject stands erect and looks straight forward. The data is used in interior arrangements, to size clothing, to design equipment, to determine the width of accommodation areas (seat, chair, stool, bar and office chairs, etc.).
Elbow Height (EH) Buttock-Knee Length (BKL) Buttock- Popliteal Length (BPL) Knee Height (KH) Popliteal Height (PH) Shoulder Breadth (SB) Hip Breadth (HB)
Appendix B. Anthropometric Measures of Students (cm) Measure
Gender
Min
%5
Mean
Std.Dev.
%95
Max
Stature (S)
Female Male All Female Male All Female Male All Female Male All Female Male All Female Male All Female
153.00 155.00 153.00 52.50 54.50 52.50 21.50 20.50 20.50 46.00 57.00 46.00 43.00 46.00 43.00 47.00 49.00 47.00 38.00
153.92 166.48 157.91 54.08 57.83 55.84 21.94 20.95 21.13 53.40 59.13 55.67 43.65 47.83 45.83 47.73 51.82 48.81 38.83
163.22 178.00 173.53 58.58 62.46 61.29 25.61 26.57 26.28 58.65 64.88 63.00 49.29 53.17 52.00 51.00 56.61 54.91 43.22
5.64 6.98 9.47 2.73 2.81 3.30 2.23 3.40 3.12 3.18 3.49 4.44 3.41 3.24 3.74 1.98 2.90 3.70 2.66
172.52 189.51 189.16 63.08 67.10 66.74 29.29 32.18 31.43 63.90 70.64 70.33 54.92 58.51 58.16 54.28 61.40 61.02 47.61
176.50 199.50 199.50 64.50 70.00 70.00 31.50 55.00 55.00 66.00 77.00 77.00 67.00 61.50 67.00 55.00 67.50 67.50 54.50
Shoulder Height (SH) Elbow Height (EH) Buttock-Knee Length (BKL) Buttock- Popliteal Length (BPL) Knee Height (KH) Popliteal Height (PH)
(continued on next page)
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International Journal of Industrial Ergonomics 74 (2019) 102864
(continued ) Measure
Shoulder Breadth (SB) Hip Breadth (HB)
Gender
Min
%5
Mean
Std.Dev.
%95
Max
Male All Female Male All Female Male All
40.50 38.00 37.00 38.00 37.00 35.00 34.50 34.50
43.26 40.64 36.74 42.34 38.14 35.00 35.84 35.25
48.10 46.62 40.32 47.41 45.26 38.42 40.60 39.94
2.93 3.63 2.17 3.07 4.32 2.07 2.89 2.85
52.93 52.61 43.89 52.48 52.39 41.84 45.36 44.63
66.00 66.00 45.50 58.00 58.00 43.50 49.00 49.00
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