Anthropometrics for Library Furniture

Ergonomic and Anthropometric Consideration for Library Furniture in an Iranian Public University

R. Osquei-Zadeh, J. Ghamari, M. Abedi, H. Shiri

Abstract

Background: In our competing educational world, students spend a considerable part of their daily life, studying at library furniture. Not surprisingly, due to lack of proper anthropometric databases, these products have typically been ill fitted for the intended user populations.

Objective: To verify the optimum anthropometric match of library furniture within an academic environment, through a combined qualitative and quantitative approach.

Methods: 267 (120 female and 147 male) students, were subjected to 11 standard anthropometric measurements. In line with the measurements, subjective evaluations were also considered through detailed fitting trials on selected groups of participants.

Results: Combinational equations defined the unacceptable furniture dimensions according to elbow and sitting popliteal heights, mainly for smaller and taller divisions of the studied population, which were systematically comparable along with subjective and objective outcomes. In brief, if we classified studied students into “small,” “medium,” and “tall” groups, the design dimensions should be altered by -5.1, -2.2, and +1.6 cm for chair seat height; and by -8.3, -5.4, and +1.1 cm for table height, for each student group, respectively.

Conclusion: The furniture size to be used by Iranian students should be changed to fit their anthropometric measures.

Keywords: Anthropometry; Libraries; Interior design and furnishings; Fitting trial; Iran

Introduction

While humans do all necessary actions for working, continuing their daily life, and meeting their social and cultural needs, they should be able to use their maximal body capacities in a physically comfortable way. This is, however, only possible when the tools and equipment they use are perfectly designed. Otherwise, poor utility and work conditions arise. This, in turn, leads to physical and mental stresses occurring in the people involved in various interactions.1 The physical characteristics of individuals vary with factors including age, gender, nutritional status, genetic structure, etc.2 Therefore, it is necessary to consider the resulting diversity in the design process, and adjust the product dimensions accordingly.3 For that reason, a number of studies and reference texts nowadays are focused on the anthropometrical characteristics of user populations.4-7 It is also confirmed that being confined to awkward postures for specific task demands, at given situations or as influenced by poorly designed products over extended periods, provokes psycho-physiological stress and imposes negative effects on human mental and physical performance.8 So, it is not surprising that designing usable and comfortable products has been the focal point of various academic and industrial projects over the last two decades. School and library furniture are decent examples in support of this matter. In some countries though, there have been attempts to design desks and chairs based on anthropometric data.9-13 In line with them, many other researchers have tried to establish theoretical recommendations, and some have also attempted to define the appropriate dimensions for such products.14-17 Another important milestone in this increasing concern is the publication of principal standards, determining the dimensions and characteristics of various products for the intended user populations.18 Not surprisingly, there are a large number of studies worldwide showing a clear anthropometric mismatch in the design of such furniture.9-17 This mismatch might affect the studying process, even during the most interesting and stimulating interactions and can produce some musculoskeletal disorders, such as neck and low-back pain. The existing library furniture at University of Social Welfare and Rehabilitation Sciences, Tehran, Iran had fixed dimensions for all the students and served as a reference. We hypothesized that this would give uncomfortable and tiring sitting positions to majority of students. The main objective of our study was to perform an anthropometric survey and, in accordance, to define the optimal dimensions and characteristics of library furniture through the application of validated and valuable anthropometric criteria.

Materials and Methods

This study was approved by the University Ethics Committee. The study population consisted of 1512 students in BSc and MSc levels (680 women and 832 men). A stratified sampling method was used, and the population was classified into four age groups (between 18 and 26 years), each one of which, contributing with a specified number of randomly selected individuals. Gender was then considered to determine the overall sample composition. ISO/TR 72 502 was also consulted to calculate the sample size,18 as follows:

Equation-1.jpg

where, CV represents the coefficient of variation, and A is the percentage of relative accuracy desired (95% and 5%, respectively in the presented study). In general, the research question was approached through two methods:

Quantitative Approach

Eleven anthropometric measures of the participants were made from the right side of their body, by adopting proper landmark definitions and standard measuring techniques.7,18 During measurements, the participants were barefooted, wearing light cloths, and instructed to sit in such a way that their thighs were in full contact with the seat, their lower and upper legs were at right angles (knee bent at 90°), their feet were placed on the floor, and the trunk was upright. The anthropometric dimensions, according to Pheasant,7 were the followings:

Stature (S): The vertical distance from the floor to the top of the head, while the person stands erect, looking straight ahead.

Sitting Elbow Height (SEH): The vertical distance from the bottom of the tip of the elbow (olecranon) to the person's seated surface, taken with the elbow flexed at 90°.

Sitting Shoulder Height (SSH): The vertical distance from the top of the shoulder at the acromion process, to the person's seated surface.

Knee Height (KH): The vertical distance from the foot resting surface to the top of the kneecap just in back and above the patella, measured with knee flexed at 90°.

Popliteal Height (PH): The vertical distance from the foot resting surface to the popliteal angle, where the back of the lower leg meets the underside of the thigh, measured with a 90° knee flexion.

Sitting Height (SH): The vertical distance from the seat surface, to the crown of the head (vertex).

Buttock-Knee Length (BKL): The horizontal distance from the back of the uncompressed buttock to the front of the kneecap.

Buttock-Popliteal Length (BPL): The horizontal distance from the back of the uncompressed buttock to the popliteal angle.

Shoulder Breadth (SB): The maximum horizontal breadth across the shoulders, measured to the protrusions of the deltoid muscles.

Hip Breadth (HB): The maximum horizontal distance across the hips in the sitting position.

Thigh Thickness (TT): The vertical distance from the seat surface to the top of the uncompressed soft tissue of the thigh at its thickest point, generally where it meets the abdomen.

In addition, the following dimensions were measured on the library furniture:

Chair Seat Height (CSH): The vertical distance from the floor to the highest point on the front of the seat.

Chair Seat Depth (CSD): The horizontal distance from the back of the sitting surface of the seat to its front.

Chair Seat Width (CSW): The horizontal distance from the outer left side of the sitting surface of the seat to the outer right side.

Chair Backrest Height (CBH): The vertical distance from the top side of the seat surface to the highest point of the backrest.

Table Height (TH): The vertical distance from the floor to the top of the front edge of the table.

Underneath Table Height (UTH): The vertical distance from the floor to the bottom of the front edge of the table.

The equipment used for this purpose included synthetic length measuring tape with an accuracy of 1 mm, Lafayette sliding caliper (range 0–60 cm with an error of 0.5 mm), and Martin anthropometer with a precision of 1 mm. The accuracy and repeatability of measurements were ensured through proper training of the measurers during a pilot study, and also regular calibration of the instruments all the way through data collection process.

To identify any mismatches, anthropometric dimensions of the participants were compared to the relative library furniture dimensions. According to Gouvali,15 mismatch is determined if the calculated value of the critical dimensions is outside the interval quantity (i.e., lower or shorter than the minimum, or higher or taller than the maximum values).

Qualitative Approach

To obtain complementary design solutions for the library furniture, the question was also approached through a qualitative methodology. For this purpose, a sample of 15 participants (3rd to 7th, 28th to 52nd, and 93rd to 97th percentiles of stature) were asked to use an adjustable mock-up of a library chair and desk within a fitting trial. They were asked to see if a particular dimension (e.g., chair seat height) would be “high,” “low,” “acceptable,” or “just right.” During the fitting trial, each participant could simulate performing the studying task, to make their judgments more realistic. The sequence of chair heights was presented twice, once in ascending and again in descending order, being alternated between participants to minimize systematic bias.7 Each trial would take approximately 15 minutes to be completed (two sets of 7-minute slots for ascending and descending sections). The ascending sequence began with a very low seat height. The height was then increased in steps until a point where the chair seat was certainly too high. In the descending sequence, this procedure was repeated until the seat height became too low. The upper and lower thresholds of acceptability were then calculated for each participant by averaging the threshold values measured in the ascending and descending trials.

Results

The results are presented for the whole sample (n=267) on anthropometric measurements, and records from fitting trials (n=15). Data categories were initially analyzed to determine whether each dimension was normally distributed. All but SB appeared to follow the normal distribution. The anthropometric data and the critical dimensions of current furniture in the library are presented in Tables 1 and 2. Based on the above-mentioned results, and using the equations in Table 3, mismatches between library furniture dimensions and students' anthropometric characteristics were mathematically calculated;1,10 the results are summarized in Table 4. Referring to “visual binning” feature in SPSS, for lower stature percentiles (1st to 30th percentiles), the majority of the students were found to be using chairs with high seat and extra-high tables, having inappropriate space underneath the table. In contrast, taller students (71st to 100th percentiles) adopted slopping postures, due to considerably low chair seats and table tops. As it was indicated earlier, a fitting trial was also organized to improve the outcome quality, whose results were notably in line with the above-mentioned findings of the study. It can be seen that smaller and taller students had preferences not being covered by the current library furniture dimensions (Table 5).

Table 1: Students' anthropometric measures (n=267)

Anthropometric Dimension

Mean (cm)

SD (cm)

Min (cm)

Max (cm)

5th %ile

(cm)

50th %ile

(cm)

95th %ile

(cm)

Stature (S)

166.9

9.16

147.0

187.0

152.0

166.7

182.8

Sitting Elbow Height (SEH)

23.7

2.6

17.5

30.0

19.0

23.7

29.9

Sitting Shoulder Height (SSH)

59.1

4.9

46.0

69.0

51.0

59.5

66.0

Knee Height (KH)

51.7

3.0

45.0

58.0

46.0

52.0

56.9

Popliteal Height (PH)

46.6

2.7

40.0

52.2

41.4

46.8

51.2

Sitting Height (SH)

87.7

5.3

76.0

100.0

78.1

88.0

95.9

Buttock-Knee Length (BKL)

55.7

4.5

34.0

64.0

50.0

55.5

62.0

Buttock-Popliteal Length (BPL)

45.9

3.2

41.0

54.0

41.0

45.5

52.0

Shoulder Breadth (SB)

43.0

3.7

35.0

51.0

36.0

42.2

49.9

Hip Breadth (HB)

37.3

2.5

31.0

43.0

33.0

37.0

41.9

Thigh Thickness (TT)

14.3

1.7

11.0

18.0

11.0

14.5

17.0

Table 2: Library furniture dimensions

Furniture Dimension

Size

(cm)

Chair

Chair Seat Height (CSH)

46

Chair Seat Depth (CSD)

40

Chair Seat Width (CSW)

45

Chair Backrest Height (CBH)

48

Table

Table Height (TH)

76

Underneath Table Height (UTH)

66

Table 3: Library furniture dimension combination formulas

Dimension Combination

Formula

1

Chair Seat Height (CSH) and

Popliteal Height (PH)

(PH + 2) cos 30 ≤ CSH ≤ (PH + 2) cos 5

2

Chair Seat Depth (CSD) and

Buttock-Popliteal Length (BPL)

0.80 BPL ≤ CSD ≤ 0.99 BPL

3

Chair Seat Width (CSW) and

Hip Breadth (HB)

1.1 HB ≤ CSW ≤ 1.3 HB

4

Chair Backrest Height (CBH) and

Shoulder Height (SH)

0.60 SH ≤ CBH ≤ 0.80 SH

5

Table Height (TH) and

Elbow-Rest Height (ERH)

(PH + 2) cos 30 + ERH ≤ TH ≤ (PH + 2) cos 30 + 0.85 ERH + 0.14 SH

6

Underneath Table Height (UTH)

(KH + 2) + 2 ≤ UTH ≤ (PH + 2) cos 5 + 0.85 EH + 0.14 SH - 4

Table 4: Mismatches between students' anthropometry and library furniture dimensions

Comparison

Mismatch (%)

1st to 30th %ile

(n=82)

31st to 70th %ile

(n=115)

71st to 100th %ile

(n=70)

Chair Seat Height (CSH)

72

38

62

Chair Seat Depth (CSD)

45

15

30

Chair Seat Width (CSW)

28

7

17

Chair Backrest Height (CBH)

27

11

22

Table Height (TH)

66

58

39

Underneath Table Height (UTH)

64

43

41

Table 5: Chair seat height preference ranges for selected stature percentiles. The cerise boxes show each participant's range of comfort, based on chair seat height alterations.

Seat Height

Adjustment

(cm)

3rd to 7th %iles

48th to 52nd %iles

93rd to 97th %iles

3rd

4th

5th

6th

7th

48th

49th

50th

51st

52nd

93rd

94th

95th

96th

97th

+5

+2.5

0.0

-2.5

-5

-7.5

-10

-12.5

 

Discussion

We tried to identify the optimum anthropometric harmony for library furniture in an academic environment. With certain dimensions, direct comparisons could be made to the elements (e.g., popliteal and knee heights, respectively). However, to accurately refine the questions, the raw data were processed into approved formulas (Table 3), before drawing the final conclusions. In agreement with Table 1, significant variations in body dimensions were to be considered for the whole sample. On the other hand, anthropometric discrepancies for table and chair seat heights were clearly predictable regarding smaller and taller students (Table 4). Similarly, fitting trials confirmed the fact that with the few possible exceptions, there was not an overlap in terms of comfortable chair seat height range, for many students (Table 5). In other words, taller students preferred chairs with much higher seats compared to smaller individuals (nearly 10 cm difference in some cases). Overall, findings showed that the library table-chair combinations were anthropometrically inappropriate for the majority of the students. Based on results of this research, we found that if the studied population be classified into “short,” “medium,” and “tall” groups, the design dimensions should be changed by -5.1, -2.2, and +1.6 cm for chair seat height (CSH); and by -8.3, -5.4, and +1.1 cm for table height (TH), for each student group, respectively. In addition, giving the students, as the main end-users of the library furniture, the opportunity to be involved in various stages of this furniture design and purchasing process, would undoubtedly result in more satisfactory outcomes.

Acknowledgements

The authors would like to appreciate all who supported this study in numerous ways. We also thank the Head of Research and Technology Deputy for the kind permission to conduct this study, and all who participated in the measurements. This work was funded by the Deputy of Research and Technology, University of Social Welfare and Rehabilitation Sciences.

Conflicts of Interest: None declared.

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TAKE-HOME MESSAGE

  • Being confined to awkward postures for specific task demands, at given situations or as influenced by poorly designed products over extended periods, provokes psycho-physiological stress and imposes negative effects on human mental and physical performance.
  • For lack of proper anthropometric databases, school and library furniture, have typically been ill fitted for the intended user populations.
  • It is necessary to consider the diverse capabilities, limitations, and preferences of the end-users, in the design process, and adjust the product traits accordingly.
  • Consulting national and international standards is also critical in developing products and environments.
  • Giving end-users the opportunity to be involved in various stages of design and evaluation would enhance the surrounding interfaces' usability.



 pISSN: 2008-6520
 eISSN: 2008-6814

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