Human Engg. & Safety 2(1+1)

Lesson 10. ANTHROPOMETRY

10.1.1 Basic Ergonomics Design Principles:

a) Design for the average:  The design of average is not fit for anyone. Because no one is average in all dimensions. These designs are utilized for design public facilities like public transport buses seats, roadside benches, these facilities are used by a large variety of peoples.

b) Design for the extremes: The extremes value may be large or very small for examples a tractor seat is designed for accommodate a range of persons, if the person is for heavy or the largest person or the smallest, so it may be not suitable for extremes.

c) Design for a range: it is the most common design philosophy and commonly used by the ergonomic to design arrange of population. A typical range of 5^th and 95^th percentile of population is used such a design would be expected to accommodate 90% of population.

10.2. Measurement of Anthropometric data:

There are very few studies available on anthropometric data on agricultural workers, again which are mainly case studies and involving only male workers.       Therefore, a comprehensive data base involving 79 body dimensions and 16 strength parameters of at least 1000 agricultural workers (male : female :: 70% : 30%) as     formulated by the ICAR is a major step towards future machinery design and        development and also for modification in design of the existing machinery.

10.2.1. Equipments used for Measurement of Anthropometric Dimensions

a) Anthropometric equipment type A : It consists of a fixed  pipe structure rigidly attached to a pentagonal base.  Several lateral pipes are attached to the main pipe.  All the steel pipes bear a linear metric scale so that measurement can be easily taken.  The pipes can also rotate about their axis and locked in any position with the help of wing nuts.

b) Anthropometric equipment type B : It consists of several  square section tubes which bear linear scale in centimeters.  The tubular sections can be prolonged by sliding and inserting one end into the other.  A veneer provision helps taking down various kinds of and difficult measurements.  A span of 210 mm  can be measured with this equipment. However, minimum distance measurable being only 0.6 cm (Fig.10.1).

c) Anthropometric seat/ chair : It consist of a number of angled  iron which are arranged together to form a seat.  The seat surface and the back one are made of plywood.  The seat height is of 600 cm while the back being 100.0 cm & the width and length being 50.0 and 70.0 cm respectively.  In accordance with the data requirement, the seat surface slides along the slots in the four legs of the seat for a distance of 24.0 cm vertically while horizontally it is 14 cm.

The seat surface board is fixed and fastened by tightening the four set of nuts and bolts.  According to the comfort at the subject, the seat height is adjusted by loosening and then tightening the four set of bolts  and nuts.  This prepares the subject to undergo anthropometric test of data collection (Fig.10.1).

The equipments consisted of the following:

i) Anthropometer in canvass bag for measurement of length 0-960 mm on one side and 0-2100 mm on opposite side.

ii) Base plate for anthropometer.

iii) Re-curved measuring branches for anthropometer.

iv) Martin type sliding caliper used for measuring length up to 200 mm and depth up to 50 mm. 

v) Spreading caliper with rounded ends having a measuring range of 0-600 mm.

vi) Skin fold caliper for measuring skin fold dimensions. 

vii) Plastic tape of length of 2000 mm.

Grip cone

A truncated cone having a height of 27.8 cm was fabricated for measuring grip diameter (inside as well as outside). Its diameter range varied between 35-95 mm. Another cone of height 18.8 cm was fabricated for measuring middle figure–palm grip diameter.  This cone has a measuring range of 10-40 mm.

Weighing balance

A spring type weighing balance having a least count of 0.5 kg and a range of 0-130 kg was used for measuring body weight of the subjects. 

10.3. Procedure for measuring Anthropometric dimensions:

1) Isolate the equipments and prepare the subject.

2) Let the subject stand on the pentagonal platform of anthropometric equipment type A.

3) Measure the height,  while standing, and while sitting in accordance with the instruments depicted in Fig.10.4 (a)

4) Note the dimensions where the equipment type A and then introduce equipment type B. (Fig.10.2) Vice-versa is also possible

5) Record each reading according to specifications

6) Put the subject into the anthropometric seat and take the dimensions as per the diagram Fig.10.4 (b).

7) Repeat similarly to different number of subjects

10.4. Analysis of Anthropometric Data:

Human being must not only fit spatially in a man task system, but must also be able to move in the work space. With the aid of anthropometric data we can provide an optimum work space layout, including good posture, contributing to considerable decrease in work load and an improvement in the performance. Normally, during collection of human engineering data skip the first and last five percentile. Thus while designing a seat; it should be designed to accommodate a reasonable range of individuals, usually from 5^th to 95^th percentiles. Seat should be designed to take maximum weight expected. In order to realize a good performance, it is necessary that the movements of the body members are in synchrony, simple and logical motions are made, which can be performed almost automatically by the central nervous system. Lower percentile values of seat height and seat depth should be taken.

For Indian agricultural workers including male and female workers, the stature would vary from 1350 mm to 1830 mm, thus the range would be 1830-1350=480 mm. according to the formula given by Raghavrao (1983), the standard deviation can be estimated from range as follows:

It is defined as the ratio of weight of a person to his /her height squared (Keys, 1972)

Measures of central tendency (mean) and dispersion (standard deviation) are good descriptive statistics of the distribution of the mass of data. Beside these two, there are two other characteristics of the distribution. These are Asymmetry also known as skewness (β) and Kurtosis or Peakedness (β₂).

The skewness (β₁):

For normal distribution, the value of β₁ as well as _β2 would be 0 to give the idea of distribution of mass data for different dimensions; the values of β₁ and β₂ have been calculated and given in here.

Table. 10.1 Anthropometric dimensions of agricultural workers

Roebuck et al. (1975) quoted to design engineering anthropometry. It is concerned with the physical measurements of human body required mainly to develop the basic engineering standards, set specific requirements and desire suitability of any manufactured product intended for the human consumer. Gite et al. (2009) collected anthropometric data of agricultural workers and compiled the data on all India, Arunachal Pradesh, Gujarat, Jammu & Kashmir, Madhya Pradesh, Maharashtra, Meghalaya, Mizoram, Orissa, Punjab, Tamil Nadu, Uttar Pradesh and West Bengal. They suggested the use of data for design of farm machinery on the basis of 5th, 50th and 95th percentile values of the dimensions (Table.10.2). 

 

Table. 10.2 Mean anthropometric and strength data of Male and Female Indian Agricultural Workers

		Male			Female
	95th	Mean	5th	95th	Mean	5th
Weight (Kg)	68.9	54.7	40.4	59.1	46.3	33.55
Stature	1774	1633	1521	1615	1515	1414
Acromial height	1468	1362	1248	1353	1261	1196
Arm reach from the wall	921	838	756	848	773	681
Bi-acromial breadth	402	330	364	340	292	243
Bideltoid breadth	471	416	361	423	371	318
Calf circumference	367	312	310	353	292	230
Chest circumference	944	845	746	934	813	693
Chest depth	243	208	173	259	207	154
Coronoid fossa to hand length	439	392	345	400	357	314
Elbow- elbow breadth sitting	452	375	297	413	350	286
Elbow height	1115	1027	938	1037	960	883
Elbow rest height	266	214	162	259	208	158
Eye height	1636	1522	1409	1504	1403	1302
Foot breadth (ball of foot)	110	94	78	101	89	76
Foot length	269	245	221	243	227	212
Forearm hand length	503	453	408	462	417	378
Hand length	197	178	160	182	167	151
Head breadth	171	148	125	202	142	156
head length	205	185	166	202	179	156
Hip breadth sitting	364	311	258	355	302	249
Instep length	208	184	142	191	167	149
Knee height	530	472	415	488	438	388
Medial malleous height	96	80	63	92	74	56
Menton to top of the head	246	213	179	232	197	162
Metacarpal-III height	763	690	616	718	649	581
Olecranon height	1085	999	913	1011	936	861
Popliteal height sitting	468	417	367	441	391	342
Sitting Acromial height	645	568	492	597	529	461
Sitting eye height	812	726	640	743	771	599
Sitting height	916	830	744	847	775	702
Span	1832	1697	1562	1680	1551	1422
Span Akimbo	964	872	780	872	790	707
Trochanteric height	925	814	703	842	777	695
Vertical reach	2237	2080	1923	2063	1921	1778
Waist back length	510	443	375	447	385	367
Waist circumference	901	765	629	858	720	582

(Source:Gite, 2009)

References:

Gite LP. 2009. Anthropometric and strength data of Indian Agricultural Workers for farm equipment design. AICRP on ESA. CIAE, Bhopal.