Anthropometric perspective to classroom furniture ergonomics and the need for standards in Nigerian schools

1 Introduction

Ergonomics is vital to safety, health and performance; and many organizations including educational institutions make changes and mobilize available resources towards improving health, safety and performance at work places [1]. In education, these include organizing the work and study settings of teachers and students in order to reach maximum output and reduce the risk of musculoskeletal discomfort. As it is with firms, when education benefits from the field of ergonomics, it creates improved quality and increased productivity. For example, ergonomic factors such as sitting posture and positioning, significantly affect typing and handwriting performance [2]. The application of ergonomics to design relies on a number of tools, one of which is anthropometry [3, 4]. Anthropometry is concerned with the measurement of human body size, shape and capacity to carry out a task [3]. School furniture is an essential element in learning environments just as sitting is an integral component of school life and if done on ill-fitted furniture can have serious implications on the physical and psychosocial wellbeing of the users. When anthropometric considerations are not made in classroom furniture designs, mismatches result, leading to musculoskeletal disorders, and can have negative effects on school performance as well as on health and motor skills of the students [1, 6].

Most classroom activities involve sitting for long periods of time with little or no breaks. Every effort should be made to ensure that young children do not experience back pain and other musculoskeletal disorders due to prolonged sitting on improperly designed classroom furniture. In addition to reducing the incidence of musculoskeletal disorders, proper sitting posture on ergonomic furniture is necessary to form good sitting habits particularly in children and adolescents [7]. Several studies [8–10] have proposed methods and guidelines for the design of ergonomic classroom furniture for students of various school ages. The various studies have reported the relevant anthropometric dimensions as well as the data for the production of ergonomic classroom furniture. A number of models exist for ergonomic furniture designs but the ‘design for adjustable range’ model is the most recommended [11]. The model relies on a range of the anthropometric measures of end users (usually between the 5th and 95th percentile of the user population). An important reason why proper posture and the use of ergonomic furniture needs to be promoted particularly among younger populations is because postural problems can develop at those ages leading to severe consequences [12, 13] including disability, loss of workplace time and high prevalence of pain in adult age [14].

Furthermore, to have safer schools and learning environments, a number of important steps are required. Due to long hours in sitting postures by school children [14–16] and because the anthropometric measures of people can change over time [17] as a result of a number of factors such as nutrition and diseases, policy makers need to develop standards for classroom furniture designs; these standards must also be revised from time to time as deemed appropriate [18]. In such situations, ergonomic design concepts and forecasts will be required to develop reliable user-friendly furniture [15]. These furniture designs should reduce the risk of musculoskeletal pain and facilitate good sitting postures among school children. School furniture must fit students’ anthropometric characteristics, and the desk must have the possibility of a tilt angle and a slight concave curve in the front, with a high saddle chair [19]. In addition to these, schools should also teach good sitting habits [20] to complement the provision of ergonomic classroom furniture; good sitting posture being described as a flat lower thoracic and lumbar posture and a lumbar lordosis without a thoracic kyphosis [14]. Compliance should also be evaluated from time to time as school children may show resistance to change while learning good sitting habits [20, 21].

Studies on the ergonomic evaluation of classroom furniture have reported huge levels of mismatches between furniture dimensions and users’ anthropometrics. In Brazil, differences in anthropometric measures were reported for 5th and 8th graders, although furniture dimensions for both categories of students were the same. This resulted in huge furniture mismatch in which the seat height was inadequate in 57% of cases, the seat length in 56% and the table height in 81% of cases [22]. In the UAE, seat depth mismatches has been reported for up to 69% and 98% of study participants in two selected schools in one study. The study also reported an alarming 68% and 100% seat height mismatch for students from the schools [6]. In Sri Lanka, a study of classroom furniture ergonomics involving 1607 school children reported 87.3% mismatch between the seat depth and the buttock-popliteal length of the users; 79.8% mismatch between the seat height and popliteal height of the users; and 76.3% mismatch for legroom height and popliteal height of the user. The study further associated mismatched seat depth and buttock-popliteal depth with the risk of developing recurrent musculoskeletal pain [23].

In many societies, disturbing levels of mismatch between classroom furniture dimensions and user anthropometrics have been reported in studies conducted at some primary schools [24–27]; secondary schools [9, 28]; and universities [8, 29–32]. These mismatches result because the furniture were in most cases not designed with the users’ anthropometric measures [26]. Musculoskeletal disorders (MSDs) such as pain in the limbs, spine and neck often result from these mismatches between furniture dimensions and users’ anthropometrics [23]. One study [31] suspects the prevalence of such MSDs among school children in Nigeria with a second study [30] reporting that improved furniture design improved the academic performance of the students in the study, in addition to reduced MSDs among the study participants. The negative impacts of classroom furniture mismatch cannot be overemphasized. Some of these problems, such as low back pain, can commence in school children and adolescents and persist till later years. These have serious health and economic implications. It is for this reason that the present study was designed to survey the anthropometric measures of primary, secondary and tertiary school children/students in Nigeria as well as include an ergonomic evaluation of the classroom furniture available to the study participants.

2 Materials and method

The dimensions of the different furniture types available to students at the surveyed schools are shown in Table 3. Lectures at the university are scheduled across different classrooms so most of students use the different furniture designs available at the venues. At the primary schools, the furniture design for the junior pupils is different from those of the senior pupils and the dimensions from one of the schools are presented. The dimensions of two different designs from the secondary schools in the study are also shown.

The anthropometric measures of all the study participants selected from the university are shown in Table 4. The result shows the minimum, maximum, as well as the mean values of all measures. It also shows the 5th, 50th and 95th percentile of the measures which are required for ergonomic furniture design for the population. In Table 5, the anthropometric measures of the female and male participants are shown. Although classroom furniture is usually not designed on the basis of specific gender measures, the results show how the males and females differ in terms of the anthropometric measures relevant to furniture design.

Table 6 shows the anthropometric measures of all the participants from the secondary schools in the study. Like the results of the measures from the university survey, this also is expressed in terms of the minimum, maximum and mean values of all the measures as well as the 5th, 50th and 95th percentile of the measures. Table 7 shows a comparison of the male and female measures of the secondary school participants. In Table 8 9, the anthropometric measures of the primary school participants are shown. At the surveyed schools, the pupils in the junior primary classes (1–3), use smaller classroom furniture as a result of their smaller body sizes. Therefore, the measures for junior and senior primary classes are presented separately as shown in Table 8 9.

An analysis of the ergonomic suitability of the classroom furniture available to the students and pupils in the study returned worrisome patterns of unsuitability. The results are presented as a match, low mismatch and high match as shown in Table 10. It is important to state as a matter of definition that both low mismatch and high mismatch are undesirable in ergonomic terms.

Ergonomic product designs that suit users and minimize the risk of musculoskeletal disorders rely on users’ anthropometric dimensions. In the present study, various anthropometric measures relevant to ergonomic classroom furniture designs were obtained from the participants across all the three levels of educational institutions –primary, secondary and tertiary. It is instructive to state that a number of studies have surveyed educational populations for the purpose of classroom furniture analysis but this present study, to the best knowledge of the authors, is the first to undertake such study at all three levels. Authors were inquisitive to know if the authorities and policymakers at any of the levels of education were conscious of an important matter as classroom furniture ergonomics or if it was the same pattern of disregard and neglect across all levels.

Generally, for the purpose of ergonomic design and/or analysis of suitability, the fifth percentile values of the popliteal height of the study population should be used to determine the ideal height of the seat. A seat height that accommodates a person with shorter popliteal height is likely to accommodate a person with a longer popliteal height, unlike if the reverse was the case. To design the depth of the seat, the fifth percentile of the buttock-popliteal depth is deployed. To achieve optimum design in the seat width, the ninety-fifth percentile of the hip width is used. For obvious reasons, a seat width that accommodates the largest hip width in the population will definitely accommodate the smaller hip widths. In the same line of argument, optimum seat-desk clearance is designed using the ninety-fifth percentile of the thigh thickness. This ensures that both users with larger and smaller thigh thickness find the under-desk height convenient for use, and may even cross their legs under the desk. The backrest height and seat-desk height are designed using the fifth percentile values of the shoulder height and (sitting) elbow height respectively. The elbow height may also be used to determine the optimum arm rest height of a seat for an individual or a population.

The anthropometric measures of the general population surveyed at the university is presented in Table 4. For the purpose of ergonomic furniture design for this population, this measures presented in Table 4 would be most appropriate. Such furniture would fit a large size of the population more than any other design. In Table 5, the anthropometric measures of the university undergraduates in the study are presented according to gender. The table shows sexual dimorphism in most of the measures. The male students in the study were observed to have greater mean values for shoulder, knee and standing heights than the females. They were also observed to have slightly greater mean values for elbow, popliteal, buttock-popliteal and thigh thickness than the females. Conversely, the females were observed to have a bigger mean value for hip width than the males in the study. Although, most furniture designs for such educational environment will favour the anthropometric measures presented in Table 4 (rather than having separate furniture for each gender), it is important for the purpose of descriptive anthropometrics to show how the males and females in the study population differ.

In Table 6, the anthropometric measures for the study participants from the secondary schools are presented. The table shows a general outlook of the anthropometric measures of children of secondary school age. These measures should expectedly be used to design ergonomically suitable classroom furniture for the population. Table 7 presents the anthropometric measures according to gender. Unlike the situation observed with the university students in the study, the secondary school females were observed to have higher mean values for shoulder, elbow and slightly higher mean value for the buttock-popliteal depth, than their male counterparts. The hip breadth was observed to be higher in the females than the males, as expected. The males were observed to have higher mean values for knee, popliteal and standing heights. One reason that may explain the difference in pattern of the anthropometric measures between the genders in the secondary schools and university is that the secondary school children are largely in their early adolescent stage (mean age of 12.86±1.88 years).

Table 8 presents the anthropometric measures of the pupils in junior primary school while Table 9 shows the anthropometric measures of the senior primary school pupils. At the surveyed schools, the pupils in the junior primary schools use classroom furniture different from the ones available to the senior pupils for obvious reasons. The pupils in the junior primary schools were generally younger and smaller in body size, which warrants the difference in design and size of furniture. In addition, at their ages, there is no much difference between the body sizes of the boys and the girls. These differences often set in between adolescence and early teenage years when the boys grow taller and the girls develop broader hips. The relevant percentiles of the measures are presented as necessary for ergonomic furniture design for the surveyed population.

In Table 10, the result of the ergonomic analysis of the classroom furniture available to the study participants are presented. The result was obtained using the criterion inequalities (1–6) presented in Section 2.6 above, to test the compatibility of the furniture dimensions with the users’ anthropometric measures. The heights of the various seats available to the participants in the study were observed to be compatible with the popliteal height of only 28% of the male and 20% of the female primary school pupils; 57% of the male and 58% of the female secondary school children and only 34% of the participating university undergraduates. The seat height was observed to be unsuitable for about 72% of the male and 70% of the female primary school participants; 43% of the male and 42% of the female secondary school participants and 66% of the participants from the university. Specifically, the seats were too low for 42% of the male and 27% of the female primary school participants; too low for 17% of the male and 9% of the female secondary school participants and 30% of the university undergraduates. They were too high for 30% of the male and 43% of the female primary school participants; too high for 26% of the male and 33% of the female secondary school participants as well as too high for 36% of the university undergraduates in the study.

When the seat depth of the furniture available to the study participants was compared with the buttock-popliteal depth of the users, a substantial level of mismatch was recorded. Across the primary schools, 48% of the males and 44% of the females had their seat depth matching their buttock-popliteal depth. The seats were observed to be shallow for 26% of the males and 29% of the females in the primary schools while being too deep for 27% of both the males and females across the primary schools in the study. Across the secondary schools, the seat depth was observed to be compliant for only 48% of the male participants and 62% of the female participants. About 1% of the males and 2% of the females were observed to use seats that were too shallow while 51% of the males and 36% of the females had seats that were too deep. With the university undergraduates, the seat depth matched the buttock-popliteal depth of only 30% of the participants while being too shallow for 35% and too deep for another 35% of the study participants.

The backrest height and seat-desk height also returned high levels of mismatches across all three categories of study participants. The backrest height which is compared with the shoulder height in sitting position was observed to match only 30% and 39% of the male and female primary school population respectively; none of the entire secondary school population and only 15% of the undergraduates in the study. The seat-desk height did not fit the elbow height of any of the study participant from the primary and secondary schools and only 7% of the undergraduates. In other words, the desks were observed to be too high for all the primary and secondary school pupils and for 93% of the participants from the university surveyed. Only the seat width and seat-desk clearance matched a large size of the study population. In the primary schools, only 1% of the males and 10% of the females have their hip widths larger than the width of the seat. All participants from the secondary schools were observed to have a match between their hip width and the seat width. The same pattern was observed among the undergraduates with the seat width fitting 99% of the study population. The seat-desk clearance was observed to match all the participants from both the secondary schools and the university; and 91% of the males and 93% of the females from the primary schools. This means a large size of the study population can sit on the classroom furniture with their knees fitting comfortably under the desk. This is important to prevent injuries to the knee cap arising from hitting the knee against the desk.

A meticulous observation of Table 10 reveals a pattern of mismatch between the furniture dimensions and users’ anthropometric measures. Where there is a mismatch, it is at a similar level across the three categories of students in the study and same for cases of match. A similar level of match was observed for the seat height among the primary school children and undergraduates; with a higher level of match for the secondary school children. A similar pattern is observed with the seat depth, backrest height and seat-desk height. Conversely, cases of a match as observed with the seat width and seat-desk clearance recorded similar pattern across the groups. This may be indicative of the same source of anthropometric data for all classroom furniture design in Nigeria which unfortunately do not fit the user populations.

The negative health impact of furniture mismatch has been widely reported in literature [38, 47]. High levels of mismatch between furniture dimensions and user anthropometrics is associated with musculoskeletal pains resulting from efforts to maintain stability in the uncomfortable position. These are often around the neck, knee and commonly in the back region. Pain associated with poor sitting posture due to unsuitable furniture may also affect the upper arm, forearm and the shoulder regions. In addition to these musculoskeletal pain, school children tend to be restless in classrooms with uncomfortable furniture as they change their posture in response to the discomfort. This affects their participation in classroom activities, reduces their attention and overall classroom performance. The implications of using unsuitable classroom furniture are costly; affecting the users in the present and as well as having future implications. The need to reevaluate school furniture designs in Nigerian schools, therefore, cannot be overemphasized.

5 Conclusion

The present study was designed to survey the anthropometric measures of school children and adolescents in primary and secondary schools as well as university undergraduates in selected schools in Nigeria and to gain an insight as to the ergonomic suitability of the classroom furniture available in these schools. The anthropometric measures obtained in this study were those relevant to ergonomic furniture designs. An ergonomic evaluation of the classroom furniture available to the study participants returned a high level of mismatch between the different furniture dimensions and the anthropometric measures of the users. In addition, the same patterns of match/mismatch was observed across all the three categories of participants, suggesting a systemic problem of classroom furniture design.

A major limitation of the present study is the fact that only representative primary and secondary schools as well as one university were surveyed in the study. This does not represent the entire educational institutions in the country. Therefore, the results do not necessarily present a general ergonomic outlook of classroom furniture in the country. In a highly populated country as Nigeria with hundreds of schools, a nationwide study will certainly require so much resources and time; nonetheless, such robust study could be an endeavor for future research.

The significance of this study cannot be overemphasized considering that Nigeria imports a lot of furniture and the foreign manufacturers, ideally, will require the correct anthropometric data of the intended users. Furthermore, authors’ observations and verbal communications with the administrators of these schools reveals that there is no existing policy on classroom furniture designs in the studied schools and by extension, the entire country. A major solution to the problem of classroom furniture mismatch as reported in this study may be to consider the use of adjustable furniture which are likely to accommodate a wider range of users. When it is not economically feasible to have height-adjustable (and/or different sizes of) classroom furniture, the government and school authorities should ensure that the available furniture fits the users by ensuring furniture manufacturers adopt the users’ anthropometric measures for their designs. The observations reported in this study is a basis for future studies of ergonomic fits in Nigerian schools and also provides designers of classroom furniture with typical anthropometric measures of target users, at least in the present time.