MASTER’S THESIS
2003:102 CIV
Nguyen Bich Diep
Evaluation of Fitness Between School Furniture and Children Body Size in Two
Primary Schools in Haiphong, Vietnam
MASTER OF SCIENCE PROGRAMME M.Sc. Programme in Industrial Ergonomics
Department of Human Work Sciences
Luleå University Of Technology Department of Human Science Division of Industrial Ergonomics
EVALUATION OF FITNESS BETWEEN SCHOOL FURNITURE AND CHILDREN BODY SIZE IN TWO
PRIMARY SCHOOLS IN HAIPHONG, VIETNAM
BY
NGUYEN BICH DIEP MSc. Students in Ergonomics
Supervisors: A/Prof. Stephen Legg
Massey University, Newzeland Dr. Nguyen Ngoc Nga
National Institute of Occupational &
Environmental Health, Vietnam
March 2003
Acknowledgement
First of all, I would like to express my special thanks to Prof. Houshang Shahnavaz, Director of Center for Ergonomics of Developing Countries, Head of Division of Industrial Ergonomics, Department of Human Work Science, Lulea University of Technology, for granting me the scholarship to attend the Master of Science Program on Ergonomics in Lulea University of Technology. I am greatly indebted to him for his kindness.
My special thanks also to Dr. Nguyen Ngoc Nga, Vice Director of the National Institute of Occupational and Environmental Health in Vietnam for nominating me to attend the Master of Science Program on Ergonomics in Lulea University of Technology and for giving me an opportunity to carry out the research on school ergonomics for my thesis.
My sincere gratitude and thanks to Associate Professor Emma Christine Lonoroth, Program Coordinator for devoting her precious time helping and encouraging me to over come every difficulties I met during my staying in Lulea , Sweden.
My special gratitude and thanks to all professors and lecturers in the Master of Science Program on Ergonomics for giving me knowledge and experiences on ergonomic science as well as devoting their precious time imparting me with needed knowledge and skills.
My thanks to all my classmates and my friends from different countries as China, Philippines, Indonesia, Thailand, Iran, South Africa, Ghana, Pakistan, Egypt, Canada, Colombia, Sweden, India and Hungary for their cooperation and participation with whom I spend very nice time during study time, group work, field trips, and also during spare time getting together in party. Their friendly dealings given me the opportunity to bear my homesickness.
My thanks also to all my colleagues in Department of Psycho-physiology of Work and Ergonomics, Department of School Health, the National Institute of Occupational & Environmental Health, and medical staffs in Haiphong Preventive Medicine Center for helping me to collect the data for my thesis.
Finally, I would like to express my sincere gratitude and thanks to my husband: Do Quang Binh and my children: Do Bich Ngoc & Do Nhat Quang for devoting their time to help me to accomplish the Master of Science Program on Ergonomics in Lulea University of Technology.
I also would like to express my admiration to the Swedish people, the most kind and lovely people I have ever met.
TABLE OF CONTENT
Pages
ACKOWLEDGEMENT 1
ABSTRACT 3
I INTRODUCTION 4
II LITERATURE REVIEW 5
2.1. Sitting position 5
2.2. School furniture 8
2.2.1. School furniture design 8
2.2.2. Body size and furniture design 11
2.3. Effects of designed school furniture and sitting positions on children behaviour and health
15
III OBJECTIVES
3.1. General objective 18
3.2. Specific objective 18
IV SUBJECTS AND METHODOLOGY 18
4.1. Subjects 18
4.2. Methodology 18
V RESULTS 22
5.1. General information of studied schools 22
Figure 3: School furniture style in Urban Primary School 23 Figure 4: School furniture style in Suburb Primary School 24 5.2. Table/desk and chair characteristics in two primary schools 32 5.3. Anthropometric measures for 240 students (Grade 1, 3 and 5) 33 5.4. Mismatch between children body dimensions and classroom furniture 36 5.4.1. Mismatch between seat height/depth and popliteal height/buttock-
popliteal length
36
5.4.2. Mismatch between Knee height and desk/table clearance 37 5.4.3. Mismatch between Elbow rest height and Desk/table height 37
5.5. Musculoskeletal complains among students 39
VI DISCUSSION 48
VII CONCLUSION 55
REFERENCES 56
ANEXEX 62
EVALUATION OF FITNESS BETWEEN SCHOOL FURNITURE AND CHILDREN BODY SIZE IN TWO PRIMARY SCHOOLS
IN HAIPHONG CITY, VIETNAM By Nguyen Bich Diep
MSc.Students
Industrial Ergonomics, Department of Human Work Sciences, Luleå University of Technology
Key words: children body size, school furniture, mismatch, fitness, anthropometry SUMMARY
Children spend a large time on school furniture in the classroom. However, very few studies evaluate the extent of a possible mismatch between school furniture and schoolchildren’s body dimensions This study was carried out in order to determine the level of mismatch between students’ body size and the furniture (chair/desk) that they use at two primary schools including urban and suburb primary schools in Haiphong city, Vietnam.
A total of 240 student participants (2 schools x 3 form levels x 40 students per form) were investigated (120 boys and 120 girls). They were divided into age groups (6, 8 and 10 years) according to the grade of each child at the moment of the survey.
The body size of each student was assessed using standard anthropometric measurement techniques including measurements of sitting elbow height, shoulder height, upperarm length, knee height, popliteal height, buttock-popliteal length, stature and weight. The existing furniture dimensions were also measured, including seat height, depth, and slope; table/desk height, depth and slope. The comparison between student body size and furniture dimension were done by using the following criteria of mismatch: seat height = >99% or <80% of popliteal height; seat depth = <80% or >99% of the buttock-popliteal length; desk/table is <2cm higher than knee height; maximum desk height is determined by: hE =0.8517 hEv + 0.1483 hS, where hEv is vertical elbow height; and hS is shoulder height. And this value was added by existing seat height and compared with existing desk height. In addition, the questionnaire on musculo-skeletal discomfort was applied to assess musculoskeletal discomfort among students.
The results of study showed that there was a gradual increase in students’ body dimensions by age, but not significant differences by gender and locations (urban or suburb schools). The stature was significantly and highly correlated to almost body dimensions (r=0.52-0.88, p<0.05 & 0.01), except sitting elbow height for girls at age 6 years, and for boys age 8 and 10 years (r=0.04-0.12, p>0.05) and upper arm for girls at 6 and 10 years (r=0.24-0.28, p>0.05). There was a variety of school furniture used in two schools. Majority of students found the seat too high and too deep or too shallow depending on grades and schools. In the suburb school, 95-100% of students in grade 1 85-100% in grade 3 and 75-100% in grade 5 found the existing seat too high and too shallow. In urban school, 100% of students in grade 1 found the existing seat too high and too shallow while 55% of students in grade 3 and 32.5% in grade 5 found their seats too high and too deep. Almost students were not fit to the existing chair-desk combinations, except 3 students (accounted for 1.25%) in grade 1 of the suburb school who were fit one of chair- desk combinations available to them. There were 20.8% students in urban school and 22.5% of students in suburb school who complained musculo-skeletal pain in different body parts. The distribution of complains by grades was different in two schools. The relationship between mismatch and musculoskeletal pain was not found.
Further investigation on a larger sample of primary school children representative over Vietnam should be carried out in order to have children body size data. And based on these data, the dimensions of school furniture will be developed to be fit to children.
I. INTRODUCTION
Children spend a large part of their school days in the classroom. In every society, school furniture is used extensively by children during what is a vital period of human physical development. Storr-Paulsen and Aagaard-Hensen (1994) noted that 8- and 9- year-olds were expected to sit for more than 60 min in any 90 min period, while Dillon (1976) observed that nursery school children were seated for 37.2% of their time in the classroom through to 78.7% for senior school pupils aged 13 to 16 years. Since school- aged children might spend 30% of their waking hours at school (Linton et al. 1994), the amount of time they are seated is considerable. As well as varying across the age range, the amount of time children are required to remain seated in the classroom also varies from country to country and according to pedagogic fashion.
The sitting position was found to be the most troublesome situation in connection with low back pain (Salminen 1984, Balague et al. 1988, Salminen et al. 1992, Troussier et al. 1994). In addition, design of school furniture is one of the contributing factors to back pain among students as indicated in some studies (Mandal, 1985; Evans, 1992;
Aagaard-Hansen et al., 1991 & 2001). Nowadays, back problems are not confined to the adult population. A surprising number of grade school children and adolescents are reported to have regular bouts of back, neck, and headache pain (Nemi et al., 1997;
Olsen et al., 1992; Trousier et al., 1994; Balague et al., 1988). Back pains also have a substantial economic impact. In 1990, direct medical care costs for low back pain exceeded $24 billion in USA, and total costs increase substantially when the indirect costs of disability are included (Lahad et al. 1994). In Great Britain alone back pain is reported to cost over 100 million pounds a year (Corlett 1999). To reduce the back pain in industry, ergonomic seating and proper positioning during the performance of activities is a major focus, especially active concerning the recommendations of new principles for the design of chairs and desks. This focus, however, is typically ignored or little interest has been shown in this largest workplace of all: the school where our youngest workers spend the majority of their time. Although school children are one group who appear to be particularly at risk because of the wide range of body size, the prolonged seated posture and the possible adverse developmental effects of prolonged exposure to postural stresses (Evans et al., 1992), there are very rare studies that
evaluate the extent of a possible mismatch between school furniture and schoolchildren’s bodily dimensions (Parcells et al. 1999; Knight & Noyes 1999). No such studies have been conducted in primary school students, nor in Vietnam.
II. LITERATURE REVIEW 2.1. Sitting position
The detrimental effects of improper classroom furniture on the spine have been known for a long time (Zacharkow 1988). The dynamics of sitting can best be understood by studying the mechanics of both the relevant body parts and the external support system involved. 75% of the total body weight is supported by only 4 inch2 (26 cm2) of surface when sitting. This small area is under the ischial tuberosities of the pelvis. The heavy load concentrated in this area results in high compressive stresses estimated at 85–100 pounds per square inch (Tichauer 1978). Structurally, the tuberosities form a two-point support system which is inherently unstable, since the center of gravity of a seated person’s body above the seat may not be directly over the tuberosities. Therefore, the seat alone is insufficient for stabilization, and the use of the legs, feet, and back in contact with other surfaces, as well as muscular forces, are necessary to produce equilibrium (Branton 1969). Leg support is also critical for distributing and reducing buttock and thigh loads. Feet need to rest firmly on the floor or foot support so that the lower leg weight is not supported by the front part of the thighs resting on the seat (Chaffin and Anderson 1991). If the major weight is to be placed on the ischial tuberosities and the proximal half of the posterior thighs, seat support should occur under and anterior to the ischial tuberosities. To maintain the weight bearing over and anterior to the ischial tuberosities, sacral and pelvic support are needed which prevent or reduce backward rotation of the pelvis and subsequent lumbar kyphosis, also known as posterior curve. Lumbar lordosis, the normal anterior curve of the lumbar vertebrae, helps to transfer some of the weight (as much as 25%) over the posterior thighs (Drummond, Narechania, Rosenthal et al. 1982).
Keegan (1953), an American Orthopedic surgeon, analyzed different postures by making a series of x-rays of people lying on their sides which documented the large movements that took place in the lumbar section of the spinal column as the position
changed from standing (a) to right angle sitting (c) and bent-over positions (d). The (b) posture is the natural resting position, as when people lie on their side while sleeping.
The lumbar curve is retained and the muscles are relaxed and well balanced (figure 1)
Figure 1. Pelvic rotation as posture varies
Pheasant (1998) also described the spine in relaxed sitting and up right sitting (figure 2).
In the relaxed sitting the pelvis rotates backward and the spine flexed. This backward rotation must be compensated by the equivalent degree of flexion in the lumbar spine-if the overall line of the trunk is to remain vertical. Hence, in sitting down we tend to flatten out the concavity (lordosis) of the lumbar region.
In order to ‘sit up straight’ and regain our lost lordosis we must make a muscular effort to overcome the tension in the hamstrings (the effort probably comes from a muscle deep within the pelvis called iliopsoas). We cannot merely relax the hamstrings since their tension is a passive one, caused by the stretching of tissue (just like an elastic band) rather than by actual muscular contraction. We shall probably also need to activate our back muscles to support weight of our trunk. If prolonged, this static muscle loading may become a major source of postural discomfort, particularly in someone who has a pre-existing tendency to suffer from back trouble (Pheasant, 1998).
Mandal (1981) called a sitting posture that approaches the natural resting position (labeled (b) in figure 1), which is a more suitable position and allows the spine to carry the body weight in a more comfortable way as "Balanced Seating". He studied the
relaxed sitting positions of 1035 children and found that none preserved a lumbar curve characteristic of the naturally relaxed position (labelled (b) in figure 1). If children were told to `sit up’ (i.e. with conscious muscular tension), 30.5% demonstrated a lumbar curve. However, this position is hard to maintain for long, so in normal seating the lumbar region tends to revert to a convex curve (labelled (c) in figure 1).
Figure 2: The relaxed sitting (left) and the sitting up straight (right). IT: Ischial tuberosities
According to Jenny et al. (2001) the lordosed seated posture, regularly interspersed with movement, is the optimal sitting posture and assists in maintaining lumbar postural health and preventing low back pain. And lordotic postures with forward leaned pelvis and low mobility are the principal causes of the increase of discomfort (Vergara & Page 2002)
Floyd and Ward (1969) studied the most frequent postural positions adopted in the classroom. It was found that three types of behaviour were most frequently observed:
sitting without support from the backrest (the backrest of a chair was most often used when only one arm was resting on the desk or when arms were not in contact with the desk at all); the trunk inclined forwards; and this forward inclination with both arms supported by leaning them on the desk. This latter posture was adopted not only when writing, but for a considerable amount of the time during other activities, so that some pupils were spending up to 80% of their time in this forward sloping position. This is
understandable given that writing activities occupy primary school children for about 30% of their desk time (Hira,1980).
Similarly, Knight and Noyes (1999) emphasized the importance of occurring the two ways of sitting during each school day, leaning backward while resting or watching the activities at the blackboard, and leaning forward when writing or reading. The time spent sitting is roughly distributed equally between backward-leaning and forward- leaning positions: a fact to be remembered when designing school furniture for the future (Storr-Paulsen and Aagaard-Hensen, 1994)
2. 2. School furniture
2.2.1. School furniture design
When designing products the criteria that defines a successful match between the products and users are commonly important include the followings (Pheasant, 1998):
Functional efficiency (as measured productivity, task performance, etc)
Ease of use
Comfort
Health and safety
Quality of working life – and so on
In the case of designing school furniture where sitting constitutes a considerable time in the school (Dillon, 1976 and Linton et al., 1994) seat becomes important in terms of comfort. All seats are uncomfortable in the long run, but some seats become uncomfortable rapidly than others, and in any particular seat, some people will be more uncomfortable than others. Comfort may also be influenced by the task or activity that the user is engaged in at that time. In other word comfort will depend upon the interaction of seats characteristics, users characteristics and task characteristics (Pheasant, 1998). It is the principle user-centered design. To achieve the best possible match between the school furniture and children (its users), the furniture should be designed in context of the (learning) task and physical and mental characteristics of school children (users). This model can be conceptualized in figure 3.
Figure 3: User center design: The furniture, the school children (users) and the task
Mandal (1985) suggested that historically it is thought that an early school desk design by Staffel in 1884 has been very influential in the design of school furniture in the twentieth century in UK. This early design required pupils to sit up straight, and indeed this is recognized that this upright seating position is infrequently adopted by children, it does appear that chairs and tables have been designed according to this standard position (Karvonen et al. 1962, Oxford 1966).
Knight and Noyes (1999) also observed that two major functions of school furniture are to support the child when attending to the teacher, and when writing or drawing on the working surface; these activities require adoption of quite different physical positions by the child. Although a chair and table could be designed to provide support for both, a compromise represented by the traditional chair design has been reached in the UK.
Another less often cited function of school furniture is to ensure that children stay in one place, in order to facilitate monitoring of their behaviour and performance and to minimize distracting interactions. A further function of the furniture should be to facilitate learning through providing a comfortable and stress-free workstation. In order to achieve this, it is generally accepted that classroom furniture needs to be designed to
The furniture’s characteristics:
Furniture dimension
Furniture angle
Furniture profile
Upholstery
The School Children’s characteristics:
Body dimension
Body aches & pain
Circulation
State of mind
The task characteristics:
Duration
Visual demands
Physical demands:
- Hand - Feet
Mental demands
allow the children to move about in their seats, as it is unnatural to keep still for long periods (Glover 1994), and localized muscle fatigue and pain can result from postural immobilization (Laville 1985). Paradoxically, this may seem to conflict with the need to keep children in one location for the majority of the time.
School children find the sitting position to be unpleasant (Salminen 1984, Balague et al.
1988, Salminen et al. 1992, Troussier et al. 1994). Sitting in the same posture in a forward bending position for a long time puts an extremely undesirable physiological strain on the muscles, the ligaments and, in particular, on the discs (Keegan 1953, Mandal 1981). It is generally accepted that sitting with a straight back is healthy.
However, few individuals can maintain this posture over time as the ischial tuberosities give relatively little support and the back muscles cannot support the trunk for very long periods when no sufficient back rest is provided (Knigh and Noyes, 1999). For this problem, Bendix et al. (1983), Bendix (1984, 1987) suggested that the seat should have a forward inclination of approximately 50, and the height of the table should normally correspond to the elbow height plus 3 - 5 cm. Moreover, the table should have a tilted desk with an inclination of 35 – 450. While a forward-inclining seat seems to affect the lumbar spine in a positive direction, a sloping desk appears to accomplish the same and, in addition, improves the posture of the other parts of the spine.
Similarly, Mandal (1976, 1981, 1982) chose an alternative design by proposing a chair with a significant forward tilt of the seat pan combined with a raised and tilted desk with an inclination of 0 – 200. This chair increases the trunk thigh angle and, by doing so, it may decrease the load supported by the spine and its musculature. He also recommended that chair height is one-third of the person's height, and the desk height one half. Most people with back pain will find this very comfortable, but for the first weeks they will only be able to sit like this for 5-10 minutes, because their back muscles need training.
Wall et al., (1991) studied sitting posture with the desk of 100 inclination and found that the position of the head in the sagittal plane was found to be 6 degrees more erect and the position of the trunk 7 degrees more erect when working at a desk with a 10 degree
inclination than when working at a flat desk. The maximal decrease in load observed on the cervical spine was 35% and on the thoracic spine 95%.
Forward sloping seats are universally accepted based on their increased trunk-thigh angle during sitting and preserve the lumbar lordosis, thereby making them more comfortable for the sitter. However, these seats are not preferred by some individuals due to reasons such as excessive pressure on knees, difficulties during ingress and egress, and postural fixity during sitting (Goonitilleke and Rao 1999).
Yeats (1997) suggested that the adjustability of school furniture is an important design feature if children are to have equal educational opportunity, increased comfort, and decreased incidences of musculoskeletal symptoms.
Apart from studies such as Linton et al. (1994), and Aagaard-Hansen and Storr-Paulsen (1995), the major part of the research on the seated working position has focused on the forward leaning posture, probably because of the predominant interest in adult subjects, and their occupations in offices or factories. It is for this reason that results obtained from studies of adults cannot automatically be applied to schoolchildren (Knight and Noyes, 1999).
2.2.2. Body size and furniture design
When designing products, it is necessary to know the body dimensions of the potential user. Relevant reasons for this are that accidents may occur due to incorrect product dimensions and sizes that do not meet the children’s dimensional requirements (Steenbekkers and Molenbroek,1990) and health problems such as musculoskeletal, visual, and circulatory (Kayis and Ozok, 1991).
Parcell et al. (1999) had some comments on design of school furniture in USA after personal communication with two school furniture manufacturers in 1996. They found that classroom furniture from manufacturers is typically not designed to accommodate the dimensions of the individual user. While a few desks offer an overall height adjustment and chairs of different sizes are available, individual adjustments for the
seat, arm and back are not offered. Instead, a one-size-fits-all philosophy has been adopted in the industry, because such furniture is less costly to manufacture and easier to sell at a lower price, and lessens the inventory problems for manufacturers and schools. Lane and Richardson, (1993) also asked the five major school furniture manufacturers in the United States, what research they relied on for their furniture designs, the response was that they did not rely on any. Instead, each company based their designs on specifications from the American Furniture Manufacturers Association and the National Standards Board to decide “seat width, belly room, and prohibited combustible materials”. Existing designs have basically been unaltered for years. While manufacturing and inventory costs are important concerns, there are also costs involved in products that do not reflect designs based on properly selected anthropometric data and ergonomics. Without proper design, sitting will require greater muscular force and control to maintain stability and equilibrium. This, in turn, results in greater fatigue and discomfort and is likely to lead to poor postural habits as well as neck or back complaints. Most important for schoolchildren, musculoskeletal stress resulting from efforts to maintain stability and comfort of seating may make for a fidgety individual, a condition not conducive to focused learning (Parcell et al., 1999).
The education of children in developing countries has long been regarded as an important element of economic development. Although well-designed school furniture has been shown to contribute to the learning process, school furniture used in these countries often detracts rather than facilitates education. Often the furniture is of low quality, has rough writing surfaces, falls apart quickly, and does not fit the children, yet it is relatively costly and consumes a disproportionate amount of limited educational budgets (Hui Zhu et al, 1998).
Current research in the area of school chair and desk design has predominantly been conducted in the Scandinavian countries and in some other countries. Furniture designs that take account of such research are now being produced in Denmark and Sweden.
The trend is also spreading in Germany, France, and Switzerland (Mandal, 1993). There are very few developing countries which have anthropometric data of school children for the purpose of furniture design. Hong Kong is one of the countries applying
anthropometric data of Hong Kong schoolchildren in design of chairs and tables for use in Hong Kong Government co-educational schools (Evan et al. 1988). Lilia, Rosalino and Elia in Mexico conducted an anthropometric survey on 4758 children (boys and girls) age (6-11 years) at Mexican primary school in the metropolitan area of the city of Guadalajara. A set of 50 body dimensions was taken based on international standards, which are necessary for the design of school furniture, "fittings and equipment in order to minimize musculoskeletal, visual, and circulatory problems resulting from using those badly designed elements (Lilia, Rosalino and Elia, 2001). Similarly, Mououdi and Choobineh (1997) measured anthropometric dimensions in 1758 children age 6-11 years in Mazandaran province, Iran. These obtained data were also used in school furniture. In USA, even in the most extensive anthropometric data on children aged 11–13 years completed in 1975 by the Highway Safety Research Institute for the Consumer Product Safety Commission, two key measurements, i.e., popliteal height and buttock to popliteal length, were not included in that study (Parcell et al., 1999). These measures of popliteal height and buttock popliteal length are needed to understand the impact of chair height and depth on posture. If the seating surface is too high, the underside of the thigh becomes compressed causing discomfort and restriction in blood circulation. To compensate for this, a sitting person usually moves his buttocks forward on the chair seat. This can result in a slumped, kyphotic posture due to lack of back support. In addition, the feet do not have proper contact with the floor surface (heels are off the floor) and body stability is weakened. On the other hand, if the seat surface is too low, the knee flexion angle becomes small, the user’s weight is transferred to a small area at the ischial tuberosities, and there is a lack of pressure distribution over the posterior thighs (Zacharkow, 1988). When the seat is too deep, the front edge of the seat will press into the area just behind the knees, cutting off circulation to the legs and feet. To alleviate the discomfort, the person in the seat will slide forward but will lose proper lumbar and backrest support. Again, this is likely to result in a slumped, kyphotic posture with excessive pressure over and posterior to the ischial tuberosities (Zacharkow, 1988, Panero et al., 1979). Too shallow a seat depth may cause the user to have the sensation of falling off the front of the chair as well as result in a lack of support of the lower thighs (Panero et al., 1979). A free area between the back of the lower limb and the seat pan is useful to facilitate the suggested 80° flexion of the knees
for rising out of the chair and for leg movements (Diffrient et al., 1974). Diffrient et al.
(1974) suggested a seat depth of 32.5 cm for an 11-year-old. Knee and elbow rest height are also important in studying posture. When knee height exceeds the desk/table clearance, the patella or anterior thigh will strike the underside of the desk or table. This may lead the user to extend and position the legs forward. The feet then lack stability. If the elbow rest height is lower than the desk or table surface, the working arm must be raised. To compensate, shoulders must also be raised or abducted placing a stress on the deeper posterior neck musculature to provide stabilization of the head posture. If the elbow rest height exceeds that of the desk or table, it will result in the user bending forward by spinal flexion, with the body weight being supported by the arms. A kyphotic spinal posture with round shoulders will result. When performing deskwork, a shoulder flexion angle of 25° and a shoulder abduction angle of between 15° and 20° is indicated (Chaffin and Anderson, 1991).
Moreover, the sex differences in anthropometry are very important for school furniture design. According to a study by Jeong and Park, 1990, the stature had a high relationship to body dimensions for school furniture design, and that there were significant sex differences in relationships between stature and the body dimensions. In particular, boys above 126 cm in stature required higher desk and chair heights than girls of the same stature. On the other hand, girls above 120 cm in stature required a larger depth and breadth of chair than boys of the same stature (Jeong and Park, 1990).
There are very few studies on fitness of furniture to student body size as indicated by Knight and Noyes, 1999; Parcells et al. (1999). Evan et al. (1992) studied on 224 students in four schools and evaluated the fitness between school furniture and students body size. The mismatch was found between thigh length and seat depth, and between the seated elbow height and the desk height. Similarly, Parcells et al. (1999) found a substantial degree of mismatch between the students’ bodily dimensions and the classroom furniture available to them. Fewer than 20% of students can find acceptable chair/desk combinations. Most students are sitting in chairs with seats that are too high or too deep and at desks that are too high. Even after controlling for body stature, girls are less likely to find fitting chairs.
Nowadays, computers have been used widely among school children. The alarming finding that 60% of the children suffer discomfort when using their laptop computer is a major outcome of a survey by Curtin University of Technology researchers (Harris and Straker, 2000). The school children are exposing themselves to prolonged poor postures with laptop use that is leading to discomfort. This is of particular concern as it occurs during critical periods of their skeletal growth (Harris and Straker, 2000). In addition, many school computers are set up without accommodation for healthy typing postures, putting children at risk of developing cumulative trauma disorders as indicated in the study examining the ergonomics of computers in the classroom completed by Cornell University involving observation of 95 elementary school children from 11 schools as they worked at computers in classrooms and labs (Alan Hedge et al. 1999). The problem is a desk that is the ideal height for pen and paper writing is often too high for comfort when typing on a computer or looking at a monitor. Most conventional chairs hold the spine in the wrong position, forcing the natural S curve of the back into an unnatural C curve. Children were sitting watching monitors placed out of appropriate viewing heights. They were sitting in some instances far forward with their feet on the floor, but backs unsupported or far rearward with their backs supported, but their legs or feet left dangling (Alan Hedge et al. 1999).
2.3. Effects of designed school furniture and sitting positions on children behaviour and health
Inadequate school furniture is frequently taken to be the reason of severe posture problems in adulthood. Therefore, chairs and desks used by children for considerable periods of time need to be evaluated carefully (Schroder, 1997). Linton et al. (1994) tested the effects of implementing ergonomically designed school furniture on measures of comfort, sitting posture and symptoms in three classes of fourth graders (10 years old) in comparison with control group using traditional furniture. They found that the experimental class rated their furniture as being significantly more comfortable and experienced a reduction in musculoskeletal symptoms relative to the control group after implementing the ergonomically designed furniture. This result suggests that furniture design is one aspect of a multidimensional problem.
Aagaard- Hansen and Storr-Paulsen (1995), in a similar prospective study found that table height, chair height and reading and writing position were significantly better for the pupils using Mandal’ s furniture. The feature of the tiltable desk-top, the back rest, and the global assessment is perceived as significantly positive independently of the other factors.
Similarly, Trousier et al. (1999) evaluated two different kinds of furniture, Mandal’s furniture and the ISO standard furniture for schoolchildren, in a real-life environment and on a long-term basis. The findings of this study are in accordance with those of previous studies (Linton et al. 1994, Aagaard-Hansen and Storr-Paulsen 1995). The ergonomically designed furniture is the best, especially for reading and writing activities because of the backrest as well as the height of the chair and the table.
Knight and Noyes (1999) also compared the effects on children's behaviour and sitting position of traditional classroom furniture with a recently designed chair known as 'Chair 2000' and associated tables by Counties Furniture, Shrewsbury, UK (Knight and Noyes 1999). The results seem likely to be associated with the highly significant reduction in nonstandard sitting observed with the Chair 2000 furniture. When children are facing forwards and not shuffling position so often, they are more likely to be judged to be `on-task’ and this impression may well be valid. Non-standard sitting might be expected to have a clearer significant relationship with fit. The significant results for the Chair 2000 in this respect are important from a design point of view as they confirm the need to match child to furniture. Moreover, the absence of a significant relationship with the commonly used guide of stature is important. The suggestion is that children’ s height is not a particularly accurate substitute for separate body part measurements and should not be used to guide seating decisions, as is current standard practice amongst manufacturers.
Marschall et al. (1995) compared muscular activity levels and sitting posture displayed by 10 children when performing tracing tasks while seated at a traditional work station (level desk top, 5 degrees backward sloping seat) and at an ergonomically designed work station (15 degrees sloping desk top, 15 degrees forward sloping seat) by EMG
profiles of latissimus dorsi (LD), erector spine (ES), and superior trapezius (ST). The results of study showed that there was no significant difference in either ES or ST muscle activity as a function of workstation design. However, subjects demonstrated significantly less LD activity when seated at the ergonomic workstation (mean = 20.9 V ms) compared with the traditional workstation (mean = 24.4 V ms, t = -2.88, p = 0.018).
Opposite results were found by Schroder (1997) in observations and records of numerous differences of movement patterns (frequencies, the possibility of choosing extreme postures in order to interrupt monotonous permanent positions, and freedom of movements for the legs) with respect to sex, age, and type of furniture. In general, the ordinary standardized school furniture under investigation turned out to meet the ergonomic demands better than a second type of furniture, which had been advertised to be especially "ergonomic".
Prolonged sitting with poor posture is associated with the development of lower back pain (Jenny et al., 2001). Nowadays, low back pain (LBP) in school children is a serious public health problem (Olsen et al., 1992). School-based surveys have shown a high prevalence of backache and particularly LBP among children and teenagers. The reported cumulative prevalence varies from country to country, Finland, 20% (Salminen 1984), England, 27% (Fairbank et al. 1984), Canada, 33% (Mierau et al. 1989), USA, 36% (Olsen et al. 1992), France, 51% (Troussier et al. 1994). The first pain episodes often occur at 13 to 14 years of age and the prevalence increases with age (Troussier et al., 1999). Among schoolchildren aged 8 to 12 years, the cumulative prevalence of LBP is lower, 6% reported by Davoine et al. (1994) and 11.6% reported by Burton et al.
(1996). Approximately 23% of elementary school children complain of backache, and that percentage rises to about 33% among the secondary school population (Mierau, 1984, cited in Marschall, Harrington, and Steele, 1995).
It is not possible to state that there is a direct causal-effect link between school furniture and back problems. However, the failure of anthropometric mismatches to fully account for expressed pain suggests that other factors contributing to postural discomfort need to be sought in addition to furniture mismatches (Evan et al., 1992). In addition, faulty
posture during childhood is an important causal factor for the development of degenerative conditions of the spinal column, which present in adults in the form of back pain, with or without functional disturbances (Knusel and Jelk, 1997). Some studies found the relationship between back, neck pain with mismatch of school furniture. Mandal (1985) conducted a survey of 14- to 15-year olds and found that 60%
of these teenagers complained of pains in the back, neck or shoulders for which they blamed the furniture. Salminen et al. (1992) also thought that low back pain was at least to some extent, due to an unsuitable school desk. The desks are probably too low in Finland, as suggested by Salminen et al. (1992): this forces the low back into a forward- leaning position where it is placed under a load. In addition, Evan et al. (1992) found that a mismatch between thigh length and seat depth was significantly related to general seated discomfort, and that a mismatch in the seated elbow height and the desk height was significantly related to pain in the shoulders and neck. The high level of reported pain and discomfort are a matter for considerable concern, and warrants further investigation.
Sitting was also found to be the trouble factor in connection with LBP. Salminen (1984), in his first survey of 370 children aged from 11 to 17 years, found that 58.9% of the low back pain sufferings had LBP in the sitting position. In addition, Balague et al.
(1988) and Troussier et al. (1994) have shown among schoolchildren that LBP increases with the duration of the sitting position at school. Furthermore, in study of Troussier et al. (1999) 37 children (23%) experienced back pain in the sitting position, and the frequency of back pain increased with the duration of the sitting posture at school.
Children are human beings, and their need for good ergonomic designs for their school workstations and equipment and future recreational toys and equipment is not well publicized. Prolonged sitting and poor posture in school are associated to low back pain in children. In addition, designed school furniture not matched the students’ body size is a contributable risk affected students’ health and behaviour. Education of proper sitting and ergonomically designed furniture should be introduced in school. Further researches on effects of school furniture on postural and visual problems should be continued.
III. OBJECTIVES:
3.1. General objective:
To improve school furniture and students’ health in primary schools in Vietnam 3.2. Specific objective:
To determine the level of mismatch between students’ body size and the furniture (chair/desk) that they use at two primary school in Haiphong city, Vietnam.
IV. SUBJECTS AND METHODOLOGY
4.1. Subjects
¾ Two primary schools (one in the city and one in the suburb area) in Haiphong city were randomly selected to participate in this research.
¾ Two single classes (each comprising 20 students) from the 1st, 3rd, and 5th Form years in each school were selected: classes 1A &1B; 3A & 3B; 5A & 5B in suburb school; and classes 1A1 & 1A2; 3C1 & 3C2; 5E4 & 5E6 in urban school were randomly selected
¾ A total of 240 student participants (2 schools x 3 form levels x 40 students per form) were obtained (120 boys and 120 girls). They were divided into age groups (6, 8 and 10 years) according to the grade of each child at the moment of the survey
4.2. Methodology
4.2.1. Research design: a cross sectional study 4.2.2. Anthropometric method:
The body size of each student was assessed using standard anthropometric measurement techniques, based on a study by Parcells et al (1999). All anthropometric measures were taken with the subject in a relaxed and erect posture. Each student was measured in T- shirt and shorts. Student dimensions (with the exception of height) were taken with the student seated erect on a flat horizontal surface, with knees bent 90°, and feet (without shoes) flat on an adjustable horizontal surface. Height was taken standing erect without shoes. The following human body dimensions, which are essential for seating and work surface design, were measured in this study:
Elbow height. The vertical distance from the bottom of the tip of the elbow (olecranon) to the students’ seated surface, measured with the elbow in 90 degrees of flexion.
Shoulder height. The vertical distance from the top of the shoulder at the acromion process to the students’ sitting surface.
Upper arm length. The difference between the elbow height and the shoulder height.
Knee height. The vertical distance measured, with 90 degree knee flexion, from the foot resting surface to the top of the kneecap, just in back and above the patella (the kneecap).
Popliteal height. The vertical distance measured, with 90 degree knee flexion, from the foot resting surface to the posterior surface of the knee( popliteal space).
Buttock-popliteal length. The horizontal distance, with 90 degree knee flexion, from the posterior surface of the buttock to the posterior surface of the knee or popliteal space.
The following measurements were also made:
Stature (body height). The vertical distance from a flat surface upon which the student stands erect, unshod and looking straight ahead, to the top of the head.
Body mass. The weight of the student, using a calibrated balance upon which the student stands.
- The following variables represent relevant dimensions of classroom furniture (chair and desk):
Seat height. The chair seat height is the vertical distance from the floor to the highest point on the front of the seat.
Seat depth. The chair seat depth is the horizontal distance of the sitting surface from the back of the seat, at a point where it is assumed that the buttocks begins, to the front of the seat.
Seat slope. The chair seat slope is the direction and angle of pitch of the seat of the chair.
Desk/table height. The desk/table height is the vertical distance from the floor to the top of the front edge of the desk or table.
Desk/table clearance. The desk/table clearance is the vertical distance from the floor to the bottom of the front edge of the desk or table.
Desk slope. The desk slope is the angle of pitch of the top of the desk.
Chair, desk, and table dimensions are measured with a metal tape, and seat and desk slopes with an angle finder. The anthropometrical and furniture measures are then combined to operationalize mismatch, which is defined as incompatibility between the dimensions of the classroom furniture and the dimensions of the student’s body.
4.2.3. Questionnaire: musculo-skeletal pain in different body parts, degree of pain and frequencies of pain, students’ opinion about fitness of furniture when sitting on and number of studying hours/day in school were assessed by asking each student to complete a questionnaire that is developed for use in this research (Annex 1).
4.2.4. Data analysis:
- Data will be analyzed statistically by using the SPSS and Excel programs:
descriptive and analytical statistics were used, ‘Student’ t test and X square test were used to compare the musculo-skeletal frequencies in two schools,
correlation was calculated between different variables in order to find the relationships between them.
- The anthropometrical data can be analyzed in average, standard deviation and 5%-ile, 50%-ile, and 95%-ile according to gender, age, school and area.
- The comparison between student body size and furniture dimension will be done by using the criteria of mismatch in Parcells et al. study (1999) as follows:
Popliteal height and seat height mismatch: seat height = >99% or <80% of popliteal height
Buttock-popliteal length and seat depth: seat depth = <80% 0r >99% of the buttock-popliteal length
Knee height and desk/table clearance mismatch: desk/table is <2cm higher than knee height
Elbow rest height and dest/table height mismatch: To determine acceptable elbow rest height with shoulder flexion and abduction (hE), the
measurements of shoulder height (hS), vertical elbow height (hEv) upper arm length (U = hS - hEv), shoulder flexion (u), and shoulder abduction (b) will be used in the following equation: hE = hEv + U[(1 - cosθ) + cosθ (1 - cosβ)] or maximum desk height is determined by: hE =0.8517 hEv + 0.1483 hS
V. RESULTS
5.1. General information of studied schools:
The studied schools including an urban and a suburb schools are located in Haiphong city, 100 km far from Hanoi capital. They are both primary schools. The urban school is called Nguyen Du Primary School located inside HaiPhong city. It is one of the biggest primary schools in Haiphong city with more than 2000 pupils. The suburb school called Anh Dung Primary School is located about 20 km far from Haiphong city. It is not big as Nguyen Du Primary School. There are about 500 pupils. Both schools comprise five grades including 1st, 2nd, 3rd, 4th and 5th grades. Each grade consists of many classes in which there are about 60-65 students/class in the urban school and 2-3 classes in which 30-35 students/class in the suburb school. The number of studying hour/day at school was similar in the same grade in different schools. In grade 1, students spend 4 hours/day at school while the grade 3 and 5 spend 5 hours/day at school for study.
Students usually study for 45 minutes and have 5 minute of break. After 2 or 3 hours they have longer break lasting 15 minutes. The welfare facilities are different in two schools. The urban school is equipped by new types of school furniture e.g. a desk with two separate chairs for two students. While in the suburb school the old furniture are still used. A long desk with bench is used by 3-4 students. Only one class in this school (Class 1A) was used the new style of furniture which is similar to that of the urban school e.g. one desk with two separate chairs (Figure 4 & 5).
Figure 4: School furniture style in the Urban Primary School Hanging
legs due to the seats are too high
Figure 5: The New (above) and Old (below) school furniture style in the Suburb School
Short Distance from eyes to table surface
Table 1 : Chair and desk/table characteristics by grades and schools
Chairs Seat height (cm)
Seat depth (cm)
Seat slope (degree)
Desk Height (cm)
Clearance (cm)
Surface Angle (degree) Grade 1:
Suburb school: 1A 1 40 38 0 1 66 41 0
1B 1 35.5 16.5 0 1 60 40 5
2 36.5 20.5 0 2 61.5 44 5
3 39 18.5 0 3 59 41 0
4 33 20 0 4 59 41 0
Urban school: 1A1 1 37 32 0 1 61 44.5 0
1A2 1 36 31.5 0 1 60.5 45 0
2 36 31.5 0 2 62.5 47 0
Grade 3:
Suburb school:: 3A 1 34 20 0 1 67 50.5 10
2 40 21.5 0 2 68 48.5 0
3 36 21 0 3 67 49.5 10
4 39 18 0 4 66.5 48 10
3B 1 40 19.5 0 1 67 52 5
2 41 20.5 0 2 69 49 10
3 36 22 0 3 68 49 10
4 40 18 0 4 68 48.5 0
Urban school: 3C1 1 39 33.5 0 1 70 54 1
3C2 2 36 32 0 2 62 46 0
Grade 5:
Suburb school: 5A 1 34 20 0 1 67 50.5 10
2 40 21.5 0 2 68 48.5 0
3 36 21 0 3 67 49.5 10
4 39 18 0 4 66.5 48 10
5B 1 40 19.5 0 1 67 49.5 10
2 41 20.5 0 2 69 52 5
3 36 22 0 3 68 49 10
4 40 18 0 4 68 48.5 0
Urban school:5E4 &5E6 1 40 34.5 0 1 70 54 10
Table 2: Summary of Anthropometric dimensions among children aged 6 years at Grade 1 in two Primary Schools (All measurements in cm except weight in Kg) (n=80)
Anthropometric Boys (n=40) Girls (n=40)
Dimensions Mean SD Min. Media
n
Max. 5%-ile 50%- ile
95%- ile
Mean SD Min. Media
n
Max. 5%-ile 50%- ile
95%-ile
Stature 113.2 4.9 103.2 112 127 106.5 112 121.7 111.5 4.6 102.2 110.7 122 104.2 110.7 118.6
Elbow Height 17.2 1.7 13.4 17.5 21.9 14.0 17.5 19.4 16.6 1.7 13.1 16.4 21 14.4 16.4 19.6
Sitting Shoulder height
39.2 3.3 32.8 38.9 47.2 34.5 38.9 45 38.3 2.9 32.2 38.1 45.5 34.4 38.1 43.1
Upper arm length 21.8 2.8 15.2 21.6 29.6 21.6 21.6 25.9 21.9 2.9 15.9 21.6 27.7 17.6 21.6 25.9
Sitting Knee height 33.8 1.9 30.9 33.8 40 31.1 33.8 37 32.6 2.4 27.5 33 38 28 33 35.9
Sitting Popliteal height
27.5 1.3 24.9 27.5 31 25.8 27.5 29.6 26.8 2 22.1 27.1 30.5 22.8 27.1 29.5
Buttock-popliteal length
29.5 2 25.4 29.5 34.6 27 29.5 33.4 29 2 23.8 29.1 33.2 26 29.1 32
Weight (kg) 19.2 3.5 15 18.8 34.5 15.5 18.8 25.1 18.1 2.5 14 18 27.5 14.5 18 21.1
Table 3: Summary of Anthropometric dimensions among children aged 8 years at Grade 3 in two Primary Schools (All measurements in cm except weight in Kg) (n=80)
Boys (n=40) Girls (n=40)
Mean SD Min. Median Max. 5%-ile 50%- ile
95%- ile
Mean SD Min. Media
n
Max. 5%-ile 50%- ile
95%- ile Stature 121.6 4.8 109.2 121.1 133 114.1 121.1 130.1 123.1 6.5 109.9 122.9 136.5 112.6 122.9 132.6
Elbow Height 17.5 2 13.2 17.5 21.5 15.1 17.4 20.9 17.5 1.8 13.5 17.7 21 15.1 17.8 20.4
Sitting Shoulder height
40.9 3.2 32.5 40.6 49.7 35.2 40.5 45.9 40.9 2.9 32 41 49.2 35.6 41 45.6
Upper arm length 23 2.8 17.2 22.7 28.5 19.5 22.6 27.7 23.4 2.9 15.9 23.6 28.6 17.9 23.6 27.4
Sitting Knee height 37.2 2 32.3 37.1 40.9 34.3 37 39.8 37.5 2.5 31.1 37.5 41.9 33.9 37.6 41.3
Sitting Popliteal height
30.1 1.7 26.7 30.2 33 27.7 30.1 32.8 30.5 2.1 26.3 30.5 35.2 27 30.5 34.3
Buttock-popliteal length
32.7 1.8 28.8 32.7 36.4 30.2 32.7 36 33.3 2.7 27 33.8 39.3 29.8 33.8 37.8
Weight (kg) 22.6 3.2 17.5 22 32.5 18.9 22 27.3 21.4 3.3 15 21.5 30 16 21.5 26
