Design of Ergonomic Tables and Chair for Special Needs Students (Case Study: Elia Junior High School Surabaya)

Elia Junior High School is one of the private middle schools in Surabaya. The school has special needs students. Elia Junior High School uses normal sized school chairs and tables for students in general, when using it they often complaints of pain in the neck, and shoulders to the size of the table is too high and the table is not flexible, pain in the spine caused the back of the chair too upright, also the table does not have a drawer and a place to put a drink and hang shoes. The purpose of this study to design school tables and chairs for special needs students with ergonomic at Elia Junior High School Surabaya with the Anthropometry approach to reduce the grievances felt by these junior high school students. Finally, on the results of the study, the size of ergonomic school tables and chair of the seat high is 40.31 cm, the seat length is 45 cm, the seat width is 35 cm, the high back of the chair is 50 cm, the seatback width is 45.44 cm, the high t of the bottom table is 54 cm, the high of the top table is 70 cm, the length, and width of the table is 54.24 cm and the high of the drawer is 10 cm. These school tables and chairs are flexible because height and inclination can be adjusted to the dimensions of the student's body and have a drawer for storing drinks, and a place to hang shoes.


Introduction
Tables and chairs are school facilities that influence students' sitting attitudes while studying, besides from being a means and infrastructure in teaching and learning activities, these tables and chairs also have other functions and roles outside of learning activities. The relationship of school tables and chairs to students is very close, namely almost as much as 80% of the time students at school almost always involve school tables and chairs in activities in the classroom. Closely the role of school tables and chairs for student activities in the classroom will indirectly relate to the design of ergonomic school tables and chairs which, due to learning activities that are more than six hours, can cause students to experience physical and mental stress due to mismatches in size school tables and chair.
The literature studies used in this study are: A Review of the Methodology and Applications of Anthropometry in Ergonomics and Product Design (Dianat et al., 2018), Design of Ergonomic Tables and Chairs that Can Support Activities and Needs in Playing Games with the Thinking Design Process (Aprillina et al., 2019), Anthropometric measurement for the ergonomic design of students' furniture in India (Taifa & Desai, 2017), Hand Anthropometry of Indonesia Young Adult Females (Nidiaputri, & Ardiyanto, 2017), Design a Spring Iron Product Using the Kano Method (Nurjannah & Purnomo, 2018) 210 guidelines to reduce the musculoskeletal disorders among the teachers (Kibria & Rafiquzzaman, 2019), Designing a New Ergonomic Student Backpack. The results showed that the new backpack using a medical belt based on ergonomic features with appropriate features provides a greater sense of comfort for users and it is improved compared to the existing backpack which is available in the Iranian market and design based on previous studies (Mansoorian et al., 2019), Determination Application of Ergonomics Chair Design in Batik Activities to Increase Productivity (Sugiharto, & Sokhibi, 2019) and Design of Tables as a Tool for Welding Process Based on Ergonomic Principles (Sutrisno et al., 2020) Elia Junior High School is one of the Private Middle Schools in Surabaya, the school has students whose physical development difference of students in general. it uses normal sized school tables and chairs for students in general, where complaints often appear in the neck and shoulder pain because the size of the table is too high and not flexible, back pain is caused the back of the chair is too upright, and the table doesn't have a drawer and a place to put drinks following government policy that suggest bringing a drink holder to school. The purpose of this study to design ergonomic school tables and chairs in Elia Junior High School Surabaya with the Anthropometry approach with the hope of reducing the complaints felt by the Junior school students.

Research Method
Steps of the research method :

Anthropometric data collection
Human

Data Uniformity Test
Data uniformity test to find out uniform data or not (extreme data or not) using map control. Extreme data is data that exceeds the control limit and then the data is discarded (Wignjosoebroto, 2016). The data uniformity test steps are as follows: a. The average value of observation.

Data adequacy test
Test the adequacy of the data to find out whether the amount of data taken is sufficient or not, if (N'≤ N) then the data is sufficient, and if (N> N) then the data is insufficient and must be re-measured until the data is sufficient (Wignjosoebroto, 2016).
Data adequacy test:  Table 1, shows the formula that will be used in calculating the size of the product design by using percentile values suitable for product design. The design of the school table and chair in this study uses 5th, 50-th, and 95-th percentiles.

Designing a school table and chair design
Designing a school table and chair concerning the results of the calculation of percentiles and other existing data. (4)

Proposed use of school table and chair
Proposed school tables and chairs are subjected to a trial run process until an ergonomic design is obtained.

Data uniformity test
Knee Fold high (KFH)   Table 2.  Table 2, shows the results of the data uniformity of all body dimensions are uniform so that all measurement data can be used for further data processing.

Data adequacy test
The data adequacy test uses a level of accuracy of 5% and a confidence level of 95%. Knee Fold High (KFH) data adequacy test: Value of N' (4.20) ≤ N (35), then the data from the measurements taken are sufficient to represent Junior High School special needs students. The results of data adequacy tests for other body dimensions can be seen in Table 3.  Table 3 shows the results of the adequacy test of all body dimensions where there is enough data, so no additional measurements are needed.

Size of proposed school tables and chairs based on percentile value
 The high of the chair seat uses 50 percentile The hight of the chair seat = X = 40.31 cm  The length of the chair seat uses 50 percentile   Figure 2, shows the design of an ergonomic table and chair proposal because it is following the body dimensions of special needs students and flexible where the table and chair can be tilted so that when using, it does not cause pain in the neck, shoulders, and back. In terms of function, the proposed school table and chair have a place to put drinks and a place to hang shoes.

Conclusion
Based on the body dimensions of the special needs student's, obtained an ergonomic school table and chair-size has the hight of the chair seat is 40.31 cm, the length of the chair seat is 45 cm, The width of the chair seat is 35 cm, the high back of the chair is 50 cm, the width back of the chair is 45.44 cm, the high of the bottom table is 54 cm, the high of the top table is 70 cm, the length and width of the table is 54.24 cm and the high of the drawer is 10 cm. The table and chair are flexible, where the high and slope of the table and the slope of the back of the chair can be adjusted to the dimensions of the junior high school student's body. The proposed school table and chair also have a drawer for put drinks and a place to hang shoes.