ASSESMENT OF FACTORS AFFECTING THE PRODUCTIVITY OF AMBER CHARKHA AND ERGONOMIC EVALUATION OF WORKERS

Transcription

1 ASSESMENT OF FACTORS AFFECTING THE PRODUCTIVITY OF AMBER CHARKHA AND ERGONOMIC EVALUATION OF WORKERS G. V. THAKRE Bapurao Desmukh College of Engineering, Nagpur University Sevagram (Wardha), Maharashtra, India S. G. PATIL Om College of Engineering, Nagpur University Wardha, Maharashtra, India D. N. AGRAWAL Bapurao Desmukh College of Engineering, Nagpur University Wardha, Maharashtra, India Abstract: Increasing demands of the cotton fabrics, now a day has made it necessary to increase the production of cotton fabrics. To increase the production it is necessary to study the factors affecting the performance of the women workers working on Amber charkha. Most of the Amber charkha in rural areas are hand operated (i.e. they run with the help of human energy input). There are various medical, technical and environmental factors which affect the productivity of women workers working on Amber charkha. This paper discusses some of those factors which are responsible for this. The various factors that are affecting the productivity are health factors, sitting posture, working environment, raw material properties, and man machine system. Each of these factors plays an important role in the overall performance of the women workers. Analysis is carried out by comparing the actual readings with the standard norms available in the literature. The detailed project work is carried out to study the different factors affecting the productivity of Amber charkha. The basic necessity of this study is to provide comfortable sitting arrangement and good working environment which would help the workers for achieving better productivity with work satisfaction. Keywords: Ergonomics, amber charkha, women, biomedical factors, etc. 1. Introduction The inhuman working conditions of the early industrialization and the confidence in the mechanical view of the world of the 19th century in the possibility of planning and creating good conditions provoked the founding of a separate science discipline. Already in 1857, Mr Jastrzebowski from Poland proposed in the journal Nature and Industry to take care of the scientific approach regarding the problems that are imposed by work and to create a separate science in order to obtain from this science the best with the least efforts with the highest satisfaction for the own and public welfare and by acting fair with regard to the own conscience and others. He called this new scientific branch Human Engineering or Ergonomics respectively. This name, however, was forgotten later. Starting in the middle of the last century, many activities happened in the various countries that dealt with a scientific view of human work. The predominant scientific view of the world considered it feasible to transfer the rules of traditional physics to all phenomenon s in nature and therefore also to human life. In the different European countries as well as in the USA, a science was established, which in the German-speaking area is called Human Engineering (in the Anglo-American language also referred to as human factors, or also called ergonomics in the European countries). [9] ISSN : Vol. 3 No.11 November

2 There are different viewpoints regarding the subject of this special field. In the introduction to his major work, W.E. Woodson wrote in 1981: Human Factors Engineering is the practice of designing products so that the user can perform required use, operation, service, and supportive tasks with a minimum of stress and a maximum of efficiency. He also mentions the term Ergonomics, which according to his viewpoint is generally used as a synonym of Human Factor Engineering. The only tangible difference is the fact that Human Factor Engineering is more common in the USA than in other countries. In 1981, M. Helander, who had been the President of the IEA for a long period, wrote: Human factors engineering aims at modifying work procedures and machinery by taking into account the physical and psychological capabilities and limitations of human beings. He did mention different denominations for this discipline, such as Engineering Psychology, Technical Psychology and Ergonomics (the latter mainly used in Europe). Ergonomics is a multi-disciplinary science which uses basic knowledge from Human Science, Engineering Science, and Economic and Social Science. It does comprise occupational medicine, industrial psychology, industrial pedagogic, working-technique and industrial law as well as industrial sociology. All of these sciences, from their different points of views, deal with human work and therefore represent an aspect of this science. With regard to feasibility, this basic knowledge is summarized in so-called phraseologies. The one which is more oriented towards sociology is called macro ergonomics. Its goal is to provide rules for the technical design of work places and work tools. For both, however, research focuses on the individual and it s experiencing the workplace. [6] Figure 1disciplines of ergonomics Regardless of what one sits on, an armchair, a stool, an office chair, a car seat or a wheelchair the body is always mechanically affected. How seating is designed always has an impact. Proper fit becomes much more important when it relates to a product that a person will be physically interacting with for hours at a time. There is one thing that every health professional agrees on: good posture is critical to longevity and good health. Alexander Technique practitioners, Qi Gong and Yoga masters, neurologists, chiropractors, fitness experts and ergonomists all understand that keeping the body in alignment is of utmost importance. [8] The challenge of designing for the human body is that it comes in so many different sizes and shapes. As a result, a design that may be comfortable for one person can be inappropriate for others. Obviously clothes and shoes come in different sizes to accommodate these differences. Once it was all about the desk; now it s about the chair, says Melissa. Many adjustments required to make an office ergonomic workstation comfortable can be made by adjusting the chair. That includes: Seating height from floor level so feet rest flat on the floor Seat usually upright but tilted slightly forwards Adequate support for lower back Proximity to desk should allow forearms to be horizontal and wrists to be straight Proper fit becomes much more important when it relates to a product that a person will be physically interacting with for hours at a time. The principles of a good sitting posture include: ISSN : Vol. 3 No.11 November

3 Pelvis: Symmetrical and upright with bottom well back in the seat Hips: Flexed (bent) at 90 degrees Spine: Symmetrical with normal curves preserved Head: upright and symmetrical, not leaning over desk Knees: Flexed at 90 degrees and thighs well supported on the seat Feet: At 90 degrees to shin and flat on the floor A table at the correct height is essential. Ensure the student can rest their elbows comfortably on the table at approximately 90 degrees Sitting improperly for long periods of time can lead to many problems involving the neck and back. Those whose jobs require mostly sitting are at an increased risk of experiencing neck and back pain. [6] 1.1 Standard Sitting Parameters Chair back strength of 150 pounds (68 kg) Chair stability if weight is transferred completely to the front or back legs Leg strength of 75 pounds (34 kg) applied one inch (25 mm) from the bottom of the leg Seat strength of 225 pounds (102 kg) dropped from six inches (150 mm) above the seat Seat cycle strength of 100,000 repetitions of 125 pounds (57 kg) dropped from 2 inches (50 mm) above the seat While sitting upright, your elbows should be at a 90 degree angle. If they are not, move your seat up or down. If you use armrests, they should be high enough to slightly lift your arms at the shoulders to take stress off your neck and shoulders. If you are sitting at a computer with your head facing forward, your eyes should be aimed at the centre of your computer screen. If your screen is higher or lower than your gaze, raise or lower it accordingly. Your feet should be flat on the floor with a 90 degree angle at your knees. You should be able to slide your fingers easily under your thighs and slide your fist behind your calf and the front of your chair. If you cannot do these things, you can prop your feet up with a footrest or add a lumbar support to the back of your chair. Your ears should be aligned over your shoulders. [10] Figure 2 Standard Sitting Posture ISSN : Vol. 3 No.11 November

4 Table 1 Dimension Showing Heights in Different Postures Ergonomic estimates for adults aged years (in mm) Dimension 5 th % ile 50 th % ile 95 th % ile Sitting Height M 850 M 910 M 965 F 795 F 850 F 910 Sitting shoulder height M 540 M 595 M 645 F 505 F 555 F 610 Shoulder breadth M 420 M 465 M 510 F 355 F 385 F 435 Hip breadth M 310 M 360 M 405 F 310 F 370 F 435 Buttock-popliteal length M 440 M 495 M 550 F 435 F 480 F 530 Popliteal height M 395 M 440 M 490 F 355 F 400 F 445 Male Female 1.2 Necessity of Ergonomic Chair Stable Support Surface A stable supporting surface is necessary to anchor the parts of the body that are active, and/or in motion. When seated, the stability required is for the pelvis, thighs and feet. With good, but not exaggerated, stability provided for the correct appropriate parts of the body, people can be very active physically when seated. Seat stability is often interpreted as meaning that the seat should be firm. Pressure Distribution Besides providing the stability required, a seat that gives such stability must not cause uncomfortable pressure. Pressure is what creates stability but is more efficient if distributed over a larger surface. Pressure distribution over a big, soft area gives more comfort. Support of Back One thing is clear though, the way the back is supported dictates the stability of the upper body. Sometimes too much support, especially when wrongly placed, makes seating more tiresome than less support. Freedom of Feet Another thing we very often overlook is the necessity to move our legs when seated. Moving the legs is one of the important ways of making seating dynamic. We use our legs and feet as instruments to influence the upper body when seated. Security & safety As mentioned earlier, it is important to feel safely and securely seated. A feeling of being safe can increase comfort, and thereby, the time that can be spent seated. You become calmer, physically and mentally. This makes the seating situation more comfortable and functional. Provides Healthy & Comfortable Sitting Posture Healthy, neutral posture improves the function of internal organs and helps harmonize the nervous system by reducing chronic muscle tension, lowering overall stress, and decreasing tension throughout the body. The reduction of pain and sensory motor activity improves the function of the nervous system. Correct posture delays many musculoskeletal degenerative disorders resulting from chronic overuse and inappropriate biomechanical relationships of the joints. [10] ISSN : Vol. 3 No.11 November

5 1.3 Biomedical Factors The menstrual cycle is the scientific term for the physiological changes that can occur in female. Painful menstrual periods are periods in which a woman experiences cramp lower abdominal pain, sharp pain that comes and goes, aching pain, or possibly back pain. Painful menstruation affects many women. For a small number of women, the discomfort makes it difficult to perform normal household & job. Thus it will affect performance of women working on amber charkha. Pain Pain can be described in many ways. Intensity of pain is commonly measured with a simple 0-7 point scale where 0 equals no pain and 7 is the worst pain imaginable. Each of the following descriptions of pain may indicate a different gynecologic condition: Pelvic discomfort Pelvic pressure Abdominal tenderness Abdominal cramps Back ache Back pain Painful urination Home Care The following steps may allow you to avoid prescription medications: Apply a heating pad to your lower abdomen (below your belly button). Be careful NOT to fall asleep with the heating pad on. Do light circular massage with your fingertips around your lower abdomen. Drink warm beverages. Eat light but frequent meals. Follow a diet rich in complex carbohydrates such as whole grains, fruits, and vegetables, but low in salt, sugar, alcohol, and caffeine. Keep your legs elevated while lying down, or lie on your side with your knees bent. Practice relaxation techniques such as meditation or yoga. Try over-the-counter anti-inflammatory medicine, such as ibuprofen. Start taking it the day before your period is expected to start, and continue taking it regularly for the first few days of your period. Try vitamin B6, calcium, and magnesium supplements, especially if your pain is from PMS. Take warm showers or baths. Walk or exercise regularly, including pelvic rocking exercises. Lose weight if you are overweight. [8] Table 2 Standards of Ergonomic Chair Seat Height Seat Width and Depth Backrest Seat Material Armrests A range of inches off the floor should accommodate most users. Thighs should be horizontal, lower legs vertical, feet flat on the floor or on a footrest. Seat height should also allow a 90 degree angle at the elbows for working. A seat width of inches suffices for most people and should be deep enough to permit the back to contact the lumbar backrest without cutting into the backs of knees. The front edge should be rounded and padded. The seat slant should be adjustable (0 to 10 degrees). Avoid bucket-type seats. The seat should swivel easily. The backrest should offer firm support, especially in the lumbar (lower back) region, should be inches wide, and should be easily adjustable both in angle and height, while sitting. The optimum angle between seat and back should permit a working posture of at least 90 degrees between the spine and thighs. Seat pan angle and backrest height and angle should be coordinated to allow for the most comfortable weight load on the spinal column. A chair seat and back should be padded enough to allow comfortable circulation. If a seat is too soft, the muscles must always adjust to maintain a steady posture, causing strain and fatigue. The seat fabric should breathe to allow air circulation through clothes to the skin. Armrests are optional, depending on user preference and task performed. They should not restrict movement or impede the worker s ability to get close enough to the work surface. The worker should not rest his or her forearms while keying. [6] ISSN : Vol. 3 No.11 November

6 1.4 Vertical Anthropometric Measurements All of the anthropometric measurements are based on the position when an individual sits with the popliteal fold 3-5 cm above the seat, with knee flexion of 90º, and with the foot flat on the floor (see fig.3). Sitting height- the vertical distance from the floor to the posterior aspect of the mid-point of the thigh Shoulder height- the vertical distance from the sitting height to the superior aspect of the acromion Elbow height- the vertical distance from the sitting height to the tip of the olecranon with the elbow being flexed to 90º and the upper arm being vertical Thigh height- the vertical distance from the floor to the highest point of the thigh Patellar height- the vertical distance from the floor to the superior aspect of the patella Orbital height- the vertical distance from the floor to the orbit Figure 3 Sagittal Anthropometric Measurements Abdominal depth- the sagittal distance from the posterior aspect of the buttocks to the anterior aspect of the abdomen External sitting depth- the sagittal distance from the posterior aspect of the buttocks to anterior aspect of the patella Internal sitting depth- the sagittal distance from the posterior aspect of the buttocks to the posterior aspect of the popliteal fold. [8] 2. Amber Charkha Figure 4 Vertical Anthropometric Measurements Gandhiji believed that Charkha as a tool can make people self-sufficient. Charkha is a unique device to spin yarn. Originally, designed as the Amber charkha (meaning "sky wheel"), about 40 years ago, had increased the productivity of user spinners and enabled them to earn up to Rs 50 per day by working. ISSN : Vol. 3 No.11 November

7 Amber Charkha designed by Ekambar Nath, a Gandhian worker from Tamil Nadu, following an appeal by the Mahatma for a more productive version of the charkha. It may not look like the typical charkha made of wood and a wheel attached to it. But it is still a simple device and can be operated even by a child. [14] There are two types of Amber Charkha used at Gram Seva Mandal, Wardha, 6 spindle and 8 spindle. Machine i.e. charkha s specifications are shown in tabulated form as follows (see table 4). Table 3 Specifications of Machine SR. NO. SPECIFICATION 6 SPINDLE 8 SPINDLE 1 Speed 40 TO 45 RPM 30 TO 35 RPM 2 Handle Length 381 mm 400 mm 3 Handle Diameter 0.5 cm 1 cm 4 Weight of Machine 35 Kg 45 Kg 5 Height of Machine 508 mm 660 mm 6 Width of Machine 762 mm 914 mm Amber Charkha (see fig. 5) was designed keeping in view to provide employment to rural youths and make them self sufficient and financially independent. Since India is a largest producer of cotton, there is a great opportunity for people from rural areas to make out a livelihood by spinning yarn on amber charkha. Usually a rural person can earn up to Rs. 50 to 60 per day. Generally the workers who are working on Amber charkha are operating the charkha by hand sitting on a floor. They have to operate the charkha for nearly 8 to 10 hours continuously which involves continuous motion of various body parts like hand, shoulder, wrist, knee etc. Because of their hectic work schedule and improper sitting posture, they suffer various health problems in long run. Specification of machine is given in table 3 and all the parameters which are taken are defined. [13] Figure 5 Amber Charkha and its Gear and pulley arrangement 3. Sitting Posture and Ergonomic Design of Table and Chair Table 4 shows the specification taken for sitting posture study and the standard parameters available for different sitting postures. The sitting postures are studied and it is compared with the standards available for the same. It is found that there is great variation in the specification observed and the standard parameter and it gives perspective to design the chair as per ergonomic dimensions available for sitting posture. ISSN : Vol. 3 No.11 November

8 Table 4 Sitting Posture Observation Sr. Specification Standard Observed Parameters No. Parameters 1 Forward Tilt 10 o 20 o 25 o 35 o 2 Backward Tilt 10 o 20 o 15 o 20 o 3 Seat Height inches 0 (there is a floor sitting arrangement) 4 Seat Width and Depth inches There is not chair sitting arrangement. So we cannot calculate the width and depth of seat. 5 Backrest inches There is no back support. wide 6 Angle between upper and 90 o 180 o lower legs 7 Angle between lower leg and floor 0 o 70 o 85 o Table 2 shows the standards for sitting posture of ergonomic chair and table design. Chair and table has been designed for the workers working on amber charkha as per the standards available for the design. Figure 6 shows the drawing of chair and table with dimensions and dimensions are shown in table 5 and figure 6 shows the ergonomic designed and fabricated picture of chair table of amber charkha. Figure 6 Dimensional View of Ergonomic Chair and table ISSN : Vol. 3 No.11 November

9 Table 5 Standards of Ergonomic Chair and Table Seat Height 19 inches Table Height 30 inches Seat Width 17 inches Table Width 21 inches Seat Depth 17 inches Table Length 24 inches Backrest 17 inches Total Height 34 inches Figure 7 Ergonomic Design of Chair and table for Amber Charkha Table 6 Specification of Machine Parameter B B1 Type & make of Machine B2 No. of spindles on Machine B3 Minimum RPM B4 Expected output of M/c as per work B5 Handle Dimension B6 Weight of Machine B7 Distance of M/c from operator B8 Height & width of M/c B1 Amber Charkha B2 6 spindle 8 spindle B rpm rpm B4 25 gundi 30 gundi B5 381 mm 400 mm B6 35 kg 45 kg B7 ½ feet ½ feet ISSN : Vol. 3 No.11 November

10 Figure 8 Women Sitting on Ergonomic Designed table and Chair Table 6 shows the specification of machine, letter B is taken as parameter and different characteristics of machine are defined with this parameter. Figure 7 shows the ergonomic designed table and chair and amber charkha is placed on the table. Figure 8 shows a woman working on amber charkha and sitting on ergonomic chair and table with ergonomic posture. Biomedical factors related to women health are studied and recorded during normal and menstrual time on existing posture of sitting on ground and on ergonomic designed and fabricated chair and table. 4. Biomedical Factors Table 7, 8, 9 and 10 gives information about body Pain & biomedical factors. W1 and W2 are the conditions taken for study. W1 means that women during her normal days and W2 mean women during menstrual cycle. Readings are taken from the month July to March from 12 pm to 4 pm at regular intervals and averages are calculated and are shown in tables. For the observations total 9 women workers are taken. From table 7 it can be seen that the workers are not having problem in pelvic, thigh and laps but the readings for shoulder, knee and spinal cord are high in W1 condition in ground sitting position. Table 8 shows the assessment of women biomedical factors after implementation of ergonomic chair. It can be seen from the table that there is large difference in the readings before implementation and after implementation of ergonomic chair and table. Operator 1 to 9 Parameters: X Shoulder; Y Knee; Z Spinal Cord. P1 Pelvic; P2 Thigh; P3 Laps Table 7 Assessment of Women biomedical factors Before Implementation of Ergonomic Chair W1 (7 scale rating) Body Pain Total (X) Total (Y) Total (Z) Total (P1) Total (P2) Total (P3) ISSN : Vol. 3 No.11 November

11 Table 8 Assessment of Women biomedical factors Woman after Implementation of Ergonomic Chair Body Pain Month Time Total (X) Total (Y) Total (Z) Total (P1) Total (P2) Total (P3) Table 9 shows the readings for women during their menstrual cycle for the same parameters which are taken for normal days while ground sitting posture. It has been observed that the readings for pelvic, thigh and laps are also found during menstrual cycle which was not seen during normal days for the same months and same time period and averages of readings are shown in tables. Table 10 shows the biomedical factors during menstrual cycle in ergonomic posture on chair and table and it has been observed that there is great variation in the readings in normal and menstrual days. The difference can be seen in normal ground sitting posture and ergonomic posture through the readings. Operator 1 to 9 Parameters: X Shoulder; Y Knee; Z Spinal Cord; P1 Pelvic; P2 Thigh; P3 Laps. Table 9 Woman (During Menstrual Cycle) Before Implementation W2 (7 scale rating) Body Pain Month Time Total (X) Total (Y) Total (Z) Total (P1) Total (P2) Total (P3) Table 10 Woman (During Menstrual Cycle) After Implementation of Ergonomic Chair Body Pain Month Time Total (X) Total (Y) Total (Z) Total (P1) Total (P2) Total (P3) Comparison Between Ergonomic Factors Before & After Implementation Of Ergonomic Chair Table 11 shows the comparison of body pain in different parts of body which are defined earlier on the scale of 7 rating before implementation and after implementation of ergonomic chair and table. It can be seen from the table that there is vast change in the readings after implementation of ergonomic table and chair. A table 12 ISSN : Vol. 3 No.11 November

12 shows there is increase in the production of gundis from to around 25 gundis and also the efficiency of the worker has increased to half an hour. Table 11 Body Pain (Scale 7 * Rating) Body Pain Before implementation After implementation Shoulder 3 * 2* Knee 6 * 4* Spinal Cord 5 * 3* 1) Laps 6 * 4* Biomedical Factors 2) Thigh 5 * 3* 3) Pelvis 6 * 4* Table 12 Production Rate Rate of Production Before implementation After implementation Gundi 25 Gundi Table 13 Actual Working Hours Actual Working Hours Before implementation After implementation 5 Hour 5:30 Hour Graph of Shoulder Pain Graph of Knee Pain After Implementation Before Implementation Before Implementation After Implementation ISSN : Vol. 3 No.11 November

13 Graph of Spinal Cord Pain Before Implementation After Implementation Figure 9 Graphs for shoulder pain, knee pain and spinal cord pain in Normal Woman - W1 Graph of Shoulder Pain Graph of Knee Pain After Implementation Before Implementation Before Implemntation After implementation Graph of Spinal Cord Before Implementation After Implementation Figure 10 Graph of shoulder pain, knee pain and spinal cord pain in woman (With Periods) W2 ISSN : Vol. 3 No.11 November

14 Graph of Biomedical Factor - Pelvic Graph of Biomedical Factor - Thigh Before Implementation After Implementation Before Implementation After Implementation Graph of Biomedical Factor - Laps Before Implementation After Implementatoin Figure 11 Graph for biomedical factors- Pelvic, thigh and lap Figure 9 shows the graphs for shoulder pain, knee pain and spinal cord pain during normal days of women before implementation and after implementation of ergonomic chair. Graphically it is easy to analyze the difference between the severities of the problem. Figure 10 shows the graph for same but during menstrual cycle of women before and after implementation of ergonomic chair. Figure 11 shows graph for biomedical factors studied and found. It shows the great difference before and after implementation of ergonomic chair in pelvic, thigh and lap. 5. Effect of Each Factor on Productivity 5.1 Sitting Posture Increase in medical expenditure Increase in work compensation Decrease in productivity Shorter work life Increase in stress level [14] 6. Results and discussion We all know that India is the largest producer of cotton in the World. This situation gives rise to a booming textile sector in the country. As this paper is based on improving working condition of women workers working on Amber Charkha, it will create better working atmosphere for them by providing better sitting posture. From observation tables and results of analysis it has been concluded that production rate increases from 20 gundis to 25 gundis. Rest pauses minimized due to which lead time decreased by half an hour. This study would help to achieve the following objectives. Better working condition for women workers working on amber charkha. Improving the productivity of women workers. To reduce the stress level of women workers. ISSN : Vol. 3 No.11 November

15 To lower down the medical expenditure of workers. To make women from rural areas financially independent. Design modification in ergonomic chair to reduce back & forth movement of worker during work on Amber charkha Arrangement for rotating the handle by both left and right hand (individually, not combined) Regular falling of tweezers can cause obstruction in work as charkha is placed on some height from ground level. 7. Conclusion Analysis and implementation of ergonomic chair gives great difference in the readings taken for different factors. The body pain of both normal women (W1) and women with menstrual cycle (W2) minimizes due to implementation of ergonomic chair. This leads to increase in the productivity and efficiency of the worker. Rest pauses minimized due to which lead time decreases. Capability and concentration of workers increases due to less fatigue observed. 8. References [1] Anil Mital, Shrawan Kumar, Human muscle strength definitions, measurement, and usage, Part I -Guidelines for the practitioner, International Journal of Industrial Ergonomics 22 (1998) [2] Alireza Choobineha*, et. al., Weaving posture analyzing system (WEPAS): Introduction and Validation, International Journal of Industrial Ergonomics 34 (2004) [3] B. Juul-Kristensen *, et.al., Criteria for classification of posture in repetitive work by observation methods, International Journal of Industrial Ergonomics 19 (1997) Received 26 April 1995; revised 5 February 1996 [4] B.M. Blatter*, P.M. Bongers, Duration of computer use and mouse use in relation to musculoskeletal disorders of neck or upper limb, International Journal of Industrial Ergonomics 30 (2002) [5] M.G. Bjoe rkstean*, et.al., Reported neck and shoulder problems in female industrial workers: The importance of factors at work and at home, International Journal of Industrial Ergonomics 27 (2001) [6] ERGONOMIC SEATING A True Challenge - When Using Wheelchairs by B. Engström [7] Sitting on the Earth is reprinted from Steve Hagen's book Meditation Now or Never, published by HarperCollins and copyright 2007 by Steve Hagen. [8] Applying Ergonomic Principles in the Workplace: How the Alexander Technique can Help, by Holly A. Sweeney, M.A. [9] Prof. Oene Hokwerda, ergonomist oene.hokwerda@home.nl [10] Sitting Posture by early school years fact pack [11] Chesapeake, Physical & Aquatic Therapy. [12] Links [13] Chaffin, D.B, & Andersson G.B.J., Occupational Biomechanics, 3rd ed. New York: John Wiley & Sons. pp [14] Echoes of Gandhi in Electricity-Generating Spinning Wheel: A Micro-Power Plant for the Poor by Kimberley Mok, Montreal, Canada. [15] Bapurao Deshmukh Sahakari Sanstha, Quality Control Lab, Sutgirni ISSN : Vol. 3 No.11 November