WORK A Journal of Prevention, Assessment &. Rehabilitation ELSEVIER Work 9 (1997) 45-55

Factors that may influence the postural health of schoolchildren (K-12)

Betsey Yeats

15 Hillsdale Road, Arlington, MA 02174, USA

Received 20 June 1996; revised; accepted 11 Febuary 1997

Abstract

Ergonomic seating and proper positioning during the performance of activities is a major focus in the adult workplace. This focus, however, is typically ignored in classrooms where our youngest workers spend the majority of their time. A review of the literature was done to determine the effects of school furniture design on the postural health of schoolchildren (K-12). The review indicated 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. The effectiveness of ergonomic school furniture on schoolchildren has been demon­ strated in only one study reviewed in this paper. The other studies are reviewed in an effort to identify: (1) the variation of anthropometric measures of children; (2) the performance of activities exposing children to various postures; and (3) the physical design features of school furniture as three factors which influence the postural health of schoolchildren. © 1997 Elsevier Science Ireland Ltd.

Keywords: School furniture; Classroom furniture; Schoolchildren

1. Introduction major human performance area that encompasses life roles such as homemaker, employee, volun­ teer, student, or hobbyist' (Jacobs et al., 1992, p. Work means many things to many people and 1086). In keeping with this concept, schoolchil­ is not limited to regular, paid employment in dren (K-12) are workers and their classrooms are which many adults engage. 'Work represents a their work environments. In 1994 alone, there

1051-9815/97/$17.00 © 1997 Elsevier Science Ireland Ltd. All rights reserved. PH S 1051-9815(97) 00022-3 46 B. Yeats / Work 9 (1997) 45-55 were 66427000 students across the United States, mental hazards that predispose injury; educating of which 81% were enrolled in either nursery workers on necessary preventive techniques (Be­ school, kindergarten, elementary school, or high ttencourt, 1995). Because the literature suggests school. Over the course of their educational ca­ that exposure to improper posture early in life is reers, these children will be exposed to a number related to injury in adulthood (Mandai, 1982; of classroom environments, which may not sup­ Olsen, 1992; Knusel and Jelk, 1994), wouldn't the port their postural needs during the performance same principles of ergonomic and injury preven­ of various classroom activities, putting them at tion apply to schoolchildren as they do to the risk for injury. adult population? Occupational therapy practi­ This review paper is intended to summarize the tioners can play an important role, not only in research concerning the effects of school furni­ minimizing the hazards that exist in the class­ ture design on the postural health of schoolchil­ room, but also in educating students on preven­ dren. This paper will examine the literature by tion and the importance and techniques of proper introducing aspects of sitting posture and by fo­ postural care. cusing on the following three factors related to Throughout the years, chairs have become school furniture design that influence the posture readily recognized in connection with both school of schoolchildren: (1) anthropometric measures of and work environments. The history of the chair schoolchildren; (2) the performance of activities; is believed to have its origin nearly 5000 years ago and (3) the physical design features of school when leaders and chiefs sat on thrones and chairs furniture. A computer-indexed and manual inves­ as a sign of dignity, with the others sitting on the tigation into the literature was conducted, yield­ ground (Grismsrud, 1990). The traditional sitting ing a paucity of American studies relating position with straight backs and 90° angles at the schoolchildren and school furniture design. The , , and , is believed to be an studies presented in this paper therefore emanate inherited phenomenon as well, passed down predominantly from foreign countries such as through many generations (Grimsrud, 1990). In Sweden, Denmark, and The Netherlands, among the late 1800s, Staffel of Germany designed school others, where the awareness of schoolchildren in furniture using the straight angles dictated by the their classroom environments appears to be more traditional sitting position, which became the advanced. . post-war model for school furniture in general The relationship between an adult worker's an­ (Grimsrud, 1990). thropometric measures, the physical design fea­ As the class society developed from the disor­ tures of their workspace and proper positioning ganized Nomadic Society, people were taught to during the performance of an activity (i.e. com­ sit in a static position; on church benches, in town puter use) is significant, evidenced by today's halls, etc. Nomadic man was pulled down off his enormous ergonomic focus in the workplace. horse and forced into a chair or onto a bench. Driving this focus is prevention and the common Even today we sit in the same type of chairs belief that proper positioning during the perfor­ which were designed several thousand years ago; mance of activities in the workplace will not only static, stiff and at the wrong angles: a destructive enhance the productivity of the worker, but de­ combination (Grimsrud, 1990, p. 291). crease the incidence of injury and associated Today the sitting position is commonly adopted health care costs as well. In the management of and with it comes associated postural health risks. today's increasing incidences of musculoskeletal Static postures and prolonged sitting are two injuries among adult workers, occupational ther­ identified risk factors for lower (Kumar apy intervention typically includes the following and Mital, 1992). Static work, characterized by principles of ergonomic and injury prevention slow contractions with heavy loads or by long-last­ techniques: analyzing the work environment; ing holding postures, impairs the blood supply eliminating and minimizing exposure to environ- and causes waste products to build up in muscles B. Yeats / Work 9 (1997) 45-55 47 and produce acute pain (Grandjean and Hunting, 2. Anthropometric measures 1977). Decreased blood flow to the organs and muscles, characteristic of the traditional sitting position, can decrease the amount of oxygen sup­ In today's classroom, children are repetitively plied to the brain causing a person to tire more exposed to the hazards of abnormal or awkward easily (Grimsrud, 1990). On a more general level, posturing due to classroom furniture that's often Kumar and Mital (1992) report that biological too big or too small. Because children vary widely tissues have a finite life, are subject to wear and in their anthropometric measurements, both tear and may have a reduced threshold at which across age groups and within the same age groups, point the tissues will fail if continual stress is all chairs and desks do not fit all children. To placed upon them. achieve a proper fit that promotes proper posture As the role of a student requires schoolchildren between school furniture and schoolchildren, it is to spend approximately 1260 h/year for 12 years important that the design of school furniture in the classroom, often sitting in static positions recognize and reflect variations in anthropometric on hard, uniformly designed classroom furniture, measurements across children of different sizes and different cultures. Oxford (1969), Evan et a!. it would appear that they are particularly at risk (1988), Jeong and Park (1990), and Ray et a!. for maladies associated with poor postural health (1995) all conducted studies which focused on (Jones, 1981). Good posture in sitting is impor­ anthropometric measures of children relative to tant in the prevention of injury, yet Wheatley and furniture design. The results of each study, how­ Hallock (1951) report that good posture is hard to ever, cannot be generalized to all children, given achieve without the support of adjusting chairs, the variation of anthropometric measures that desks and tables in the school environment. exist between different cultures. Wheatley and Hallock also report that sitting Data from an anthropometric survey directed habits are inevitably created early in life and that by Oxford (1969), measuring over 13 000 Aus­ the object of the adjustable chair and desk in the tralian participants from infancy to adulthood, classroom is to promote natural, comfortable sit­ indicated that girls reach 65% of their stature at ting positions early in life so that they will be­ age four and 95% at age 13; the same data come habitual. Like Wheatley and Hallock, Floyd indicated that boys reach 60% of their stature at and Ward (1969) contend that the classroom is age four and 95% at age 15. The data demon­ the most appropriate place for the habituation of strates the tremendous amount of physical growth good sitting habits to take place, because bad that takes place during the school years. Also sitting habits acquired early are most difficult to demonstrating the differences in size between change later in adulthood. schoolchildren of the same grade, Oxford found Freudenthal et a!. (1991) indicate that correct that of 578 kindergarten children, 10% had a sitting posture should include: dynamic behavior lower leg measurement equal to the mean, while with many postural changes, sitting erect most of 10% had a seat-to- measurement equal to the time, and leaning back in the chair to rest the the mean. Not one child, however, had both of back, without strong flexion of the cervical spine. the means and according to Oxford these are the Wheatley and Hallock (1951) described good sit­ two measurements most related to chair and table ting posture as having the sit vertically, with heights. According to Oxford, a chair satisfies the forward curve preserved, and the postural requirements when the height of the seat freely hanging back. They further state is equal to the lower-leg measurement and the that 'the points of the seat bones, the crests of backrest can be utilized. Since the lower leg mea­ the hipbones, and the tips should be in surement varies greatly among schoolchildren, the same plane, and in this position there should more than one size of school furniture available be no uncomfortable pressures, strains, pushes or in each classroom would better satisfy a child's pulls' (Wheatley and Hallock, 1951, p. 418). postural and educational needs. Oxford states 48 B. Yeats / Work 9 (1997) 45-55 that 'when pupils sit on chairs that are too low, rean school children in order to provide appropri­ there is a marked tendency for them to slouch, to ately sized chairs and desks for school use. In push the feet forward and become a nuisance to total 1248 participants, ages 6-17 years old, par­ others, and, generally, to adopt bad postural ticipated in their study. There were 52 boys and habits' (Oxford, 1969, p. 153). In addition 'when 52 girls in each age group and all were randomly chairs are too high, pupils are freed to 'perch' on selected from four elementary, middle and senior the front of the seat, to sacrifice the comfort of high schools in Seoul, Korea. Results of the study the backrest, to lean on the table, to fidget, and if indicated that between the ages of 10 and 11, the the table is too high, to sit with and mean height of the girls exceeded the mean height in a state of tension' (Oxford, 1969, p. 154). To of the boys. According to Jeong and Park boys satisfy the need for more than one size of school above 126 cm require higher desk and chair furniture in New South Wales, Australia, Oxford heights than girls of same stature, due to their reported that six heights of movable chairs and relatively higher buttock-popliteal length and el­ desks have been distributed to their classrooms bow to floor distance. In addition, girls above 120 since the end of World War II. cm require a larger seat depth and breadth of Evan et al. (1988) took anthropometric mea­ chair than boys of the same stature, due to their sures from 684 normal, healthy primary and sec­ relatively higher buttock-popliteal length and ondary Hong Kong Chinese schoolchildren, ages breadth than boys of the same stature. Jeong and 6-18, and compared them to anthropometric val­ Park concluded that boys and girls have different ues for Hong Kong children previously published requirements for the design of their work space, by Chan in 1972. The purpose of their study was including the classroom. In addition Jeong and to improve the fit between school children and Park suggested that these results highlighted the the tables and chairs used in Hong Kong's schools important relationship between body dimensions by making design recommendations based on their and stature, citing the usefulness of this relation­ results. Evan et al.'s increased values for stature ship in estimating unknown body dimensions when suggested a trend of increased size. Evan et al. designing school furniture. Jeong and Park at­ (1988) reported that because classrooms are orga­ tributed a reduction of anthropometric measure­ nized by age and not anthropometric measures, ments between age bands to differences in so­ the furniture must accommodate the range of cioeconomic stratum, however, they did not subs­ sizes of pupils in the different classes. Like Ox­ tantiate this proposed relationship. ford (1969), Evan et al. (1988) found rapid growth Ray et al. (1995) also reported that the dimen­ in children aged 6-14 years old, requiring that sions of the chair should have reasonable agree­ four categories of furniture sizes be available to ment with the user's physical dimensions. They achieve a reasonable fit between the anthropo­ conducted a study which focused on 81 anthropo­ metric measures of children and school furniture; metric measures of 198 kindergartners from In­ beyond age 14 one category of furniture size was dia, ages 3-5, specifically citing a lack of data for determined to accommodate five secondary forms this age range. Results indicated that the majority (3-7). This furniture allocation is suggested to of the vertical dimensions have a higher correla­ ensure that the great majority of children can tion with stature than weight, while the horizontal work comfortably in good posture. Both Evan et and circumference measures have a higher corre­ al. and Oxford proposed that discomfor.t and bad lation with weight than stature. Like Jeong and postures associated with badly designed chairs Park (1990), Ray et al. (1995) recommended that and tables used in schools are factors that may the means of the ratio's of each segmental length affect academic performance, as well as the physi­ to stature be used to determine different body cal development of schoolchildren. dimensions of other children in a particular age Jeong and Park (1990) specifically investigated group when stature or body weight is unknown. In gender differences and the interrelationships general the authors report that these data will among the anthropometric measurements of Ko- provide Indian designers with some basic guide- B. Yeats / Work 9 (1997) 45-55 49 lines for the development of products or work total time. Also during a 90-min morning lesson, environments of children aged between three and the teachers wanted the pre-schoolers to work in five. a seated posture without interruption for 19 min, Results from studies conducted by Oxford the ninth formers for 90 min, and the 3rd, 7th, (1969), Evan et al. (1988), Jeong and Park (1990), 8th and 9th formers for an average 60 min. In and Ray et al. (1995) all support the need for addition 43% of the total seated time was spent adjustability or incrementally sized school furni­ in backward-leaning activities, while the other ture in classrooms to accommodate the variation 57% was spent leaning forward, reading or writ­ in anthropometric measures across different age ing. In addition to reporting from both a medical groups, within the same age groups, and between and educational viewpoint that it is not beneficial genders. Both Jeong and Park and Ray et al. cited to be seated for more than 45 min without breaks, the importance of the relationship between body Storr-Paulsen and Aagaard-Hensen also proposed dimensions and stature and the usefulness of this that the effects of time scheduling and the organi­ relationship in estimating unknown body dimen­ zation of teaching be taken into consideration sions when designing school furniture. A proper when evaluating school ergonomics. fit between schoolchildren and school furniture is Floyd and Ward (1969), like Storr-Paulsen and an important aspect of attaining good posture and Aagaard-Hensen (1994) addressed the same issue one that deserves attention if all children are to of task performance while seated, however, they be given equal academic opportunity (Oxford, focused on direct observations of children without 1969). consideration for the teachers scheduling and or­ ganization. Both the amount of time spent per­ 3. Performance of activities forming certain tasks and the proportions of time that postural behaviors were observed to occur in In addition to a poor fit between the anthropo­ parallel with these activities were recorded for 84 metric measures of schoolchildren and school fur­ participants with a mean age of 17.2 years. The niture, the performance of classroom activities subjects were observed at their usual desks and such as reading and writing often place the stu­ chairs during 20-24 lesson periods. Results sug­ dent in abnormal or awkward posturing with the gested that: listening was observed to occupy use of stationary classroom furniture. Both Floyd between 35 and 40% of the total time; writing and Ward (1969) and Storr-Paulsen and occupied nearly 30% of the time; following a text Aagaard-Hansen (1994) identified typical posi­ or reading occupied approximately 10-15% of the tions of schoolchildren during the performance of time; the other activities of reading, looking up, classroom activities, in addition to the corre­ speaking, preparing for class, reaching for con­ sponding amount of time spent in these positions. tents of satchel, coat or desk, standing up and Storr-Paulsen and Aagaard Hensen (1994) con­ sitting down, and being absent temporarily from ducted a survey in Denmark, asking teachers to the classroom took up the remaining 15-25% of record various working positions of 194 time. The following three postures were observed schoolchildren ages 5-15 for a 1-week period. to occur most frequently in parallel with the The study focused specifically on the priorities of aforementioned activities: sitting without support the teachers and their time schedules relative to from the backrest (approx. 77% of the time); the factors that ergonomically constrain schoolchil­ trunk inclined forwards (approx. 72% of the time); dren. For each lesson, both the subject and the leaning forward on the desk with both arms sup­ types of working postures that the teacher ex­ ported on the desk (approx. 65-80% of the time). pected the class to assume during the lesson were Floyd and Ward concluded that although the recorded. The results indicated that the children activity of writing occupied 30% of the student's in pre-school were expected to be physically ac­ time, leaning forward on the desk with both arms tive for 73% of the total time, while the ninth supported occurred nearly 65-80% of the time, formers were expected to be active for 19% of the indicating that this position is assumed even when 50 B. Yeats / Work 9 (1997) 45-55 the constraints of writing do not require it. The desk showed an increase in activity for all mus­ authors also concluded from their analysis that cles, except for the left erector spinae muscle. the use of the backrest was observed most often Floyd and Ward reported that the marked in­ in positions when only one or no arms were crease in the latissimus dorsi muscles on the side resting on the desk. opposite the moving , were a result of those As part of the same study Floyd and Ward muscles actively supporting the trunk against (1969) conducted a pilot electromyographic inves­ gravity. Floyd and Ward also concluded that the tigation with one participant of the same age and symmetrical position of leaning forward with both stature as the 84 participants previously men­ arms supported by desk provoked activity in the tioned. The purpose of the electromyographic latissimus dorsi and the cervical portion of the study was to obtain recordings of simultaneous , indicating that this position is not nec­ bilateral muscle activity of the trunk, including essarily a position of rest. the cervical portion and the mid-clavicular por­ Floyd and Ward (1969) recommended further tion of the trapezius muscle, the post-axillary studies using electromyography; they also pro­ folds of the and the lum­ posed that further analysis of postural behaviors, bar region of the in three coupled with the basic anthropometric require­ symmetrical and three non-symmetrical seated ments, be considered in the design of both seats postures. The symmetrical postures and their re­ and chairs. The results of the electromyographic spective electromyographic results included: (1) portion of the study should be viewed with cau­ sitting at attention without use of the backrest, tion as only one participant participated. In addi­ with legs bent at a right angle at the and tion, the study looks at postural behaviors across with the arms relaxed in the , showed an all of the activities together and therefore certain increase in activity of the erector spinae muscles; postures cannot be correlated specifically to cer­ (2) sitting erect comfortably with use of the back­ tain activities. rest, with the trunk slightly rounded, with legs Floyd and Ward (1969) and Storr-Paulsen and bent at a right angle at the knee and arms relaxed Aagaard Hensen (1994) both identified positions in the lap, showed almost minimum activity in all assumed by schoolchildren during the perfor­ four muscle groups; and (3) sitting with the body mance of classroom activities. Storr-Paulsen and supported by the arms leaning upon the desk and Aagaard Hensen found that as children advance the trunk in a forward relaxed position showed an in grade, the amount of time they're expected to increase in activity of the left and right latissimus sit without interruption also increased, beyond dorsi muscles (larger than that of the erector what they considered to be a healthy amount of spinae muscles in posture 1), as well as an in­ time without a break. Storr-Paulsen and Aagaard crease in the left and right cervical portions of Hensen also reported that 57% of the total time the trapezius muscle, but to a lesser extent. The seated was spent leaning forward, which accord­ asymmetrical postures and their respective elec­ ing to Jeong and Park (1990) is a position that tromyographic results included: (1) sitting erect requires increased muscle activity, as compared to comfortably with the right arm only supported on sitting against a backrest. Like Storr-Paulsen and the desk showed an increase in the right latissi­ Aagaard Hensen, Floyd and Ward found that mus dorsi and erector spinae muscles particularly, participants in their study typically sat (1) without as well as an increase in the mid-clavicular por­ support from the backrest; (2) with the trunk tion of the trapezius muscle; (2) sitting erect inclined forwards; and (3) leaning forward on the comfortably with the left arm only supported on desk with both arms supported on the desk while the desk showed the reverse, with an increase in listening, writing, following a text, reading, look­ the left latissimus dorsi and erector spinae mus­ ing up, speaking, preparing for class, etc. cles, as well as an increase in the mid-clavicular Results of Floyd and Ward's electromyographic portion of the trapezius; and (3) sitting in the study, however, found that the position requiring habitual left-handed position for writing at the the least amount of active contraction from the B. Yeats / Work 9 (1997) 45-55 51 four identified muscle groups was sitting erect for the chair and 50-70 cm for the table. In comfortably using the backrest with the trunk addition the chair was tilted backward 5° and the slightly rounded, with the legs bent at 90° at the table top was oriented horizontally. The subjects knee, and the arms relaxed in the lap. This is also were asked twice to adjust the height of both the the position described by Wheatley and Hallock chair and table to the heights they most pre­ (1951) as typifying good posture and the position ferred. Results of the study suggested that the described by Freudenthal et al. (1991) as a good participants preferred both the table and chair position of rest. Because participants in both heights be 15-24 cm higher than the ISO stan­ studies were typically found leaning fOlward with­ dards. As a general rule, MandaI recommended out use of the backrest for a majority of the time, that a chair be at least one-third the height of the their postural health may be at risk due to static person using it, while a desk be at least one-half contractions and prolonged postures, taxing more the height of the person using it. Mandal con­ muscles over longer periods of the time. With cluded that the study's participants clearly de­ adjustability and variability features built into the monstrated their preferences to sit much higher design of school furniture, however, children could and he further recommended that the seat of the proactively arrange their desks and chairs to fit chair slope forward 10-15° with a fixed cushion to both their physical needs and their preferences counteract sliding forward and that the table top during the performance of activities. slope backward 10-15°. It is unclear in the study, however, as to whether the recommendations for 4. Classroom furniture design features a sloped chair and sloped table were based on preferences set by the participants or if they were In addition to anthropometric measures and preset and then accepted by the participants. In the performance of classroom activities, the phys­ general MandaI reported that students are a cap­ ical features of school furniture design can also tive audience upon which to conduct seating stud­ influence posture. In motor learning literature it ies, because of their: (1) short focal distance of is commonly understood that the regulatory fea­ approximately 30 cm, compared to an adult's fo­ tures of the environment control features of one's cal distance of 50-70 cm due to presbyopia; (2) movement; the physical characteristics of a chair their flexible backs; and (3) the demands of the and desk in a classroom, for instance, dictate the classroom keeping them uniformly focused on the way in which a student must position him or same task. MandaI explains that: herself when sitting in a chair or writing at a desk (Gentile, 1987). Hira (1980), MandaI (1982), In order for a person 180 em tall to position the eyes at a Freudenthal et al. (1991) and Aagaard-Hansen distance of 30 em from a book placed on a table 70 cm and Storr-Paulsen (1995), and all conducted stud­ high, the back will have to bend at an angle of 75° if all of ies investigating the preferred features of school the bending takes place in the lumbar joint. On the other , if the table is 90 cm high, 50° of flexion will be furniture design and proposed subsequent recom­ adequate. If the table is tilted, the flexion can practically be mendations. eliminated, as the book is then brought closer and at a MandaI (1982) conducted an empirical field better angle to the eyes (Mandai, 1982, p. 263). study with the purpose of determining the heights at which 80 participants, ages 7-50, preferred In summary MandaI suggests that the 'abuse of their desks and chairs. If the majority of the children's backs during adolescence could well be participants were adults, however, MandaI's re­ the reason for the rapidly increasing number of commendations would not necessarily be general­ back ailments' (MandaI, 1982, p. 268). He states izable to children. The experiments were con­ that 'designers of furniture have learned nothing ducted using a hydraulic chair and hydraulic table, about the anatomy of the seated person, and local both originally set in accordance with the stan­ school authorities seem to place high priority on dards outlined by the International Standards Or­ low-cost furniture that is easily stacked and com­ ganization (ISO) relative to height, at 30-50 cm pactly stored' (MandaI, 1982, p. 268). While high- 52 B. Yeats / Work 9 (1997) 45-55 lighting important design features, MandaI's seat­ height, especially in the reading position. The ing study appeared to make extensive conclusions authors also suggested that these results be con­ based on short 4 or 5 min observations, raising sidered by school authorities and their medical the question of how seating preferences may have advisors, when choosing school furniture. The au­ changed over time. thor's believe that the back health of school chil­ In a comparative rating study between three dren is a field that involves many disciplines and different kinds of furniture, Aagaard-Hansen and that the focus on school furniture should be only Storr-Paulsen (1995), like MandaI (1982), re­ one aspect of its management. ported that students preferred increased table In addition to both MandaI (1982) and Aa­ heights, in addition to other identified design gaard-Hansen and Storr-Paulsen (1995), Hira features. The study evaluated three different kinds (1980) also found that the table height, among of school furniture, based on the subjective com­ certain other features of both the desk and chair, fort level of 144 participants between the ages of is an important factor in seating design. Hira 7 and 11, in their natural life environment. The conducted a survey to ergonomically evaluate the participants were systematically divided into three most commonly used type of fixed educational groups. In Phase 1 each group received identical desk. Approximately 30 lecture halls in colleges furniture based on the ISO standards. In Phase 2 and the University of Ludhiana in India were each group received either: (1) newly made furni­ surveyed, collecting characteristic dimensions of a ture identical to that used in Phase 1; (2) newly representative group of 14 desks. The relevant made furniture based on MandaI's recommenda­ characteristics studied included: desk height front tions with the desk approximately 15 cm higher edge, desk height rear edge, top horizontal width, than the furniture used in Phase 1, a forward top inclined width, slope, seat desk clearance, slanting seat and the angle of the desk top ad­ seat height, seat depth, back rest width, seat back justable between 0 and 20°; the desk height was rest clearance. also adjustable to suit the preferences of the Hira (1980) applied the established standards students; or (3) newly made furniture marginally found in a thorough literature search whenever higher than the furniture used in Phase 1, with its possible. However, when not possible, he con­ seat slanted forward by 3° and the angle of the ducted experiments using 40 participants to de­ desk top adjustable. Results suggested that partic­ termine suitable values. When students outside of ipants considered all three types of new furniture the identified participant group were found work­ better than the original furniture used in Phase l. ing naturally at their desks, however, they were Results also suggested that the type (2) furniture, also observed. Hira's study resulted in the fol­ with a forward sloping seat, tiltable desk-top lowing recommendations for fixed furniture de­ between 0 and 20°, and a desk height 15 cm sign: a seat height clearance of 16 cm; a desk higher, was considered significantly better than height of 73 cm; a table top slope of 12.14° with a types (1) and (3) in a global comparison between S.D. of 2.7°; a writing surface width of 50 cm; a the new and old furniture, back-rest, reading po­ seat height of 44.5-52 cm; a seat depth of 35-38.5 sition, table height, and chair height. Findings for cm for work seats and 23-33 cm for educational both furniture types (2) and (3), relative to the desks; a horizontal seat with a slight curve at the adjustable desk-top feature, were nearly identical front edge to relieve pressure on the ; and a with scores of 93.9 and 93.2 respectively, support­ back rest with adjustable and sliding seat with ing the student's interest in this feature regard­ cushion to promote comfort and assist in learn­ less of the type of furniture being used. An inter­ ing. esting finding also revealed that 43 of the 144 Hira (1980) emphasized that the application of students surveyed in Phase 2 experienced fre­ ergonomics to fixed seating is very limited and quent back pain. Aagard-Hansen and Storr-Paul­ that more work is needed. For the many studies sen concluded that furniture type (2) was pre­ conducted, Hira provided a summary of the re­ ferred for its back-rest, chair height and table sults and did not include actual data or scores, B. Yeats / Work 9 (1997) 45-55 53 upon which he based his recommendations. In provement in sitting posture by using a tOO in­ addition, participants for the study were selected clined desk was evident and that an improvement· to be representative of the students of Punjab, in workplace design can be attained by using India limiting the generalizability of the results to reading and writing desks with a tOO inclination. children, due to both age and the variations of Recommendations for classroom furniture de­ anthropometric measures across cultures. Hira sign features common to the studies conducted by proposed that the recommended features could Hira (1980), MandaI (1982), and Aagaard-Hansen assist in changing posture over the course of the and Storr-Paulsen (1995), include increased table day, benefiting children by supporting their need height, increased chair height and an adjustable for dynamic positioning, potentially improving cir­ table top. Freudenthal et al.'s (1991) study speci­ culation and spinal alignment, increasing levels of fically evaluated the effects of a tOO sloped desk arousal and alertness, as well as decreasing pres­ top with results showing a significant improve­ sure on the diaphragm and abdominal cavity. ment in sitting posture. Aagaard-Hansen and Freudenthal et al. (1991) conducted a study at a Storr-Paulsen and Hira both recommended the University in The Netherlands with to students back rest as an important design feature to be and staff members, ages 20-60-years-old. Al­ included. MandaI recommended a forward seat though the participants were not in the K-12 age tilt to promote proper posture in leaning forward range, this study is relevant as it directly ad­ by reducing the amount of flexion of the back. dresses the effects on posture of a sloped desk Each of the aforementioned design features were top that was also recommended by Hira (1980), preferred by the participants in the above men­ MandaI (1982), and Aagaard-Hansen and Storr­ tioned studies and are recommended as impor­ Paulsen (1995), during the performance of read­ tant design features in the promotion of good ing and writing tasks typical of students. Freuden­ sitting posture. thal et al. (1991) introduced a tOO inclined office It has been found that anthropometric mea­ desk and made continuous recordings of position sures, the performance of activities, in addition to of the head and trunk to determine the effects of specific design features of school furniture are all the inclined desk on sitting posture while reading factors that influence the postural health of school and writing. Participants were seated in an ad­ children. It is assumed that chairs and desks in justable chair at an adjustable table. Results indi­ classrooms fit all children, however, adjustability cated that a significant improvement in sitting and variability of furniture provided in the class­ posture was found, as more upright posture of the room is needed to satisfy a child's postural and head and trunk was measured, decreasing the educational needs. The effectiveness of ad­ static load placed upon the muscles and liga­ justable, ergonomic seating on schoolchildren, ments. Results also indicated that the average however, has been demonstrated in only one study median measure of the posture of the trunk conducted in Sweden. In 1991 the governing laws changed approximately 8° more upright for the in Sweden enforcing regulations for a safe work trunk and 9° more upright for the position of the environment were amended to include and apply head; in addition flexion of the cervical spine to schoolchildren in the classroom. Linton et al. decreased by about 2°. A decrease in the range of (1994) conducted a two-group design study mea­ postures in the lateral direction was also found, suring the effects of ergonomically designed as was a significant decrease in the range of school furniture on comfort, sitting posture and positions for the head. Freudenthal et al. con­ the incidence of musculoskeletal symptoms among cluded that this finding did not necessarily indi­ schoolchildren. Participants included three classes cate fewer movements, but did indicate less ex­ of 10-year-old schoolchildren in the 4th grade; treme movements taking place less often. They the control group received traditional furniture suggested that this finding reflects less physiologi­ with a flat top desk and a detached chair with a cal discomfort while reading and writing with the straight back and the seat at 90°, while the experi­ tOO inclined desk. It was concluded that the im- mental group received ergonomically designed, 54 B. Yeats / Work 9 (1997) 45-55 adjustable furniture. The students used the furni­ enough and that proper educational instruction is ture for 6 months. In addition to answering a also required to introduce ergonomics and to questionnaire, the students' sitting behavior was teach the students and teachers how to properly observed twice before receiving the furniture, adjust the furniture. Linton et al. encouraged twice after receiving the furniture, and 5 months additional prospective, controlled studies. later at a follow-up session. Results of the obser­ Based on a review of the literature, the design vations assessing the presence or absence of iden­ of school furniture does have an effect on the tified 'sit behaviors' yielded no significant differ­ postural health of schoolchildren. Because the ences between the groups on any of the behav­ physical design features of school furniture re­ iors, however, about half of the participants in the quire schoolchildren of varying shapes and sizes experimental group were reported to improve to fit into uniformly sized chairs and desks, good their posture. Linton et al. (1994) conjectured posture is often sacrificed. Instead poor postures that the noted improvements in posture may be are often assumed, putting at risk both the physi­ important relative to the. measure of muscu­ cal development and academic performance of loskeletal symptoms. Results of the questionnaire schoolchildren (Oxford, 1969; Evan et aI., 1988). indicated that the experimental group had higher In addition, the standard physical design of school comfort ratings after receiving the new furniture, furniture, without adjustability, requires in addition to a significant improvement at the schoolchildren to assume awkward postures dur­ follow-up on ratings of how well they sat. In ing the performance of school activities such as addition, the experimental group experienced a reading and writing. These awkward postures statistically significant reduction in back pain at maintained over long periods of time are risk the follow-up session, while an overall index of factors for musculoskeletal injury, according to back, , headache and tiredness together ap­ Kumar and Mital (1992). In contrast, adjustable proached statistical significance. There were no school furniture would not only address the differences, however, reported between the groups uniqueness of anthropometric measures across regarding their awareness of the school work en­ schoolchildren, but also support the postural vironment. Linton et al. proposed that comfort, needs of schoolchildren during the performance although typically thought of as a 'soft' variable, of school activities. The provision of adjustable may have an important relationship with school furniture, however, is only part of the schoolchildren complying to advice on posture. solution as Linton et al. (1994) discussed. A uni­ Linton et al. states that 'it is unlikely that pupils fied approach addressing the relationships will be persuaded to use correct postures in order between the anthropometric measures of to avoid back pain sometime in the future as an schoolchildren, the performance of activities re­ adult: it is more likely that the immediate effects quired in the classroom and the physical design of comfort may be more effective in ensuring that features of school furniture is needed to support advice about posture is followed' (Linton et al., the postural health of schoolchildren. 1995, p. 304). Linton et al. considered the number Seating has been an important focus in er­ of participants reporting musculoskeletal prob­ gonomics and human factors literature on adults. lems to be high but in keeping with other reports. However, little research has been done on the In addition they state that the need for preven­ student population and the effects of classroom tion is clear, as 'youngsters are aware of muscu­ seating on schoolchildren's postural health. With loskeletal problems early on and these symptoms such widespread adult disability due to muscu­ appear to be very real and relevant to them' loskeletal injury, of which improper posture in (Linton et aI., 1994, p. 304) Linton et al. ques­ sitting is a potential contributing factor, it would tioned if the level of significance of the results appear that more research is needed to detect were masked due to inadequate measures. Also any associations between childhood exposure and as a result of this study, Linton et al. concluded adult injury. The studies discussed in this paper that providing ergonomic furniture alone is not were brought together in an effort to highlight B. 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