Variety of physical characteristics in industrially developing countries— ergonomic consequences

117

International Journal of Industrial Ergonomics, 4 (1989) 117-138 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands

VARIETY OF PHYSICAL CHARACTERISTICS IN INDUSTRIALLY DEVELOPING COUNTRIES ERGONOMIC CONSEQUENCES A. Wisner Conservatoire National Des Arts eL M#tiers, Ergonomie eL Neurophysiologie du Travail, 41, Rue Gay-Lussac, 75005 Paris (France)

ABSTRACT In many industrially developing countries, data concerning the physical characteristics of populations have been collected for various technical and scientific purposes and published in a very scattered way. Results obtained in 39 countries and described in 103 publications have been selected. Data evaluation is not so much concerning with the ethnic differences which are normally stressed than with the influence of biological, social, economic and geographic factors such as sex, age, health, condition, socio-occupational background, altitude or climate. The ergonomic consequences of this study affect the dimensional characteristics of the production locations or the industrial product. Some products such as cars may suit the purchaser population all over the world. On the other hand, industrial and especially agricultural machines and tools should be linked to users" characteristics. Further ergonomic considerations are related to the occasionally excessive physical strength limits of many populations in industrially developing countries. Efforts to be made, loads to lift and distances to cover over bad ground have moderate or dangerous effects according to the physical capacities of the persons in question. Highlighted as such, the actual workers' capacities have a significant effect on production and economic development. The preservation and increase of these capacities may be obtained in accordance with specific ways and means.

1. I N T R O D U C T I O N Anthropometric measurements were among the first data used by new-born ergonomics 40 years ago. But most of these data are from the military sources of O E C D member-countries. Nowadays, economic exchange is commonplace among industrially developing countries (IDC) but is unsatisfactory in many respects. This paper will be limited to the ergonomic viewpoint. Too often, the engineering systems, machines and products transferred are not suited to the physical characteristics of the people in IDCs. In fact these characteristics 0169-8141/89/$03.50

© 1989 Elsevier Science Publishers B.V.

are not known. The references mentioned in this text come from highly varied sources, most of which are little known in their country of origin. Many other measurements, of which the author is unaware, may well have been taken. Moreover, these anthropometric data have only been partially analyzed in order to determine the systematic influence of age, sex, socio-occupational conditions and state of health on the characteristics of the people observed. Only ethnical considerations were developed. It will be seen that ethnical considerations often have little relevance from the ergonomic viewpoint since, in factories and

118 stores, ethnic groups are often mixed for economic reasons. Finally, it will be seen that military sources are not always usable since, depending on the system of values prevailing in each country, a soldier can be a professional with a high standard of living and good nutrition, or someone drafted against his will and living a hard life. A successive study will be made of the general physical characteristics and their consequences on segmental dimensions and workstation design, then the working power and its effect on the laboriousness of tasks.

2. GENERAL PHYSICAL CHARACTERISTICS The data which are easiest to obtain are the standing height and body weight. These values cannot be used directly but, as will be seen further on, they can be used to evaluate the data necessary to built the workstation and organize the activity. An analysis of the results of 296 native population samples from all over the world by Tildesley (1950) established the average height at 1650 mm. Roberts (1975), using the results from 1,200 European and African population samples, suggests an average height of 1671 mm, which is higher since the evaluation does not take into consideration the people of South and East Asian, numerous, small-stature populations. But such general data are just curiosities in the field of ergonomics which mainly requires accurate and suitable recommendations. People's anthropometric characteristics appear to be unchangeable and specific. But ergonomists have long been inclined to believe that differences of age, sex, social environment and secular divisions in the same country should be taken into consideration, for example, when designing a car driver's seat for the largest number of users (Wisner and Rebiffr, 1963a, b). The study of the physical dimensions of the world's different populations highlights such sources of variation along with ethnic differences. As will be seen, ethnic differences do not always have a genetic origin, nor do social differences always have a nutritional origin.

2.1. India Due to a lack of basic data, it is impossible to make an intensive study of these various factors for the world's population. The only industrially developing country where it seems possible to confirm what is seen in industrialized countries is India, which is both a large economic power and a country with a high scientific development level. Some of the 44 references, over half of which come from R.N. Sen and his student P.K. Nag, have been taken into consideration here. For complex reasons, the samples studied are often few and far between and there is no guarantee of their representativeness in terms of the population studied. The people studied in the samples are probably in better physical condition that the average population since it is often stated that young and apparently healthy workers were examined. This fact obviously rules out the unemployed, the elderly and the sick. In most cases, the significance of the results is increased to a considerable extent by the fact that the study includes a job analysis of the people studied and a description of their living standards and the conditions under which measurements were taken. Most measurement were taken in Northern India. Table 1 summarizes the results obtained by Indian authors from their fellow citizens. The male Indian farmer (usually a poor farmer) has an average height of 157 cm and a mean weight of 39 kg. There is a slight tendency for the young (20-29 years) to be 1-2 kg heavier (Nag, 1981). The Indian industrial worker has an average height of 164 cm and an average weight of 55 kg (Sen and Sarkar, 1979). This indicates a considerable difference compared to poor farmers. In industrialized countries, the difference is usually only 1-2 cm. The explanation for the large variation in India could be due to genetical differences linked to the caste system, but is more likely because of the standard of living and, in particular, the nutritional level in large industrial cities in the North. An indication of the comparative nutritional well-being of workers is the fact that in one sample studied older men (aged 40-45) had a higher average weight (62 kg) than younger mean (20-29) who only weighed 54 kg.

119 TABLE 1 Diverse male Indian groups (after 44 Indian references) Population

N

Age (years)

Height (cm)

Weight (kg)

Body surface (m2) 1.50

Body fat (%)

Lean body weight (kg)

7? 7

42 43

4

44

(1/min)

VO2 (ml/kg min)

1.91 2.01

42 44

VO 2

Maximal heart rate (b/rain)

Young agricultural workers

131 74

27 22.23

157 157

45 46

Country working people of eastern India

192

21

161

46

Miners

154

31

161

49

1.9

39

Railway track maintenance

50

30

163

48

1.9

40

Load carriers Sherpas

11

30 28

164 160

50 54

2.3 3.8

44 73

2460

35 ?

164

55

2.3

41

Students

352

2

167

53

2.5

41

Soldiers

10

26

168

59

2.7

45

197

Mine rescue workers

40

32

170

62

1.8

29

180

Industry workers

W o r k e r s o u t s i d e u r b a n i n d u s t r y are n o t so fortunate. F o r instance, r a i l w a y t r a c k r e p a i r m e n are 163 c m tall a n d weigh 48 kg ( N a g et al., 1985) a n d D h a n b a d miners are 161 c m a n d weigh 49 kg ( C h a k r a b o r t y et al., 1979a). It s h o u l d be n o t e d t h a t in S o u t h Africa, S t r y d o m r e c o m m e n d s that no miners u n d e r 50 kg should b e h i r e d ( S t r y d o m et al., 1971). O t h e r e m p l o y e e s in the D h a n b a d mines, the rescue teams, are in even b e t t e r c o n d i t i o n ( H = 170 cm, W = 62 kg), b u t u n f o r t u n a t e l y their p h y s i c a l c o n d i t i o n is n o t as g o o d as their living a n d nutrition s t a n d a r d s , as shown b y their low a e r o b i c p o w e r p e r kg ( G u h a r a y et al., 1979). H e a v y w o r k e r s in various p a r t s of the c o u n t r y (vehicle pushers o r pullers, porters) are the s a m e height as f a c t o r y w o r k e r s (164 cm), b u t are lighter (50 kg) ( D a t t a et al., 1983). I n b e t t e r - o f f social classes, p e o p l e are taller. I n various s t u d e n t groups, the average height is 167 c m a n d the weight 53 kg ( B a n d o p a d h y a y a n d C h a t t o p a d h y a y , 1981). T h e difference in height b e t w e e n w o r k e r s a n d s t u d e n t s is similar to that f o u n d in i n d u s t r i a l i z e d countries. T h e average height of a group of female s t u d e n t s is 155 c m a n d the weight 49 kg ( O b e r o i et al., 1983).

1.58

7

50

184

I n India, as in m a n y i n d u s t r i a l l y d e v e l o p i n g countries, soldiers c o n s t i t u t e a privileged g r o u p : H = 168 c m a n d W = 59 kg ( S e n g u p t a et al., 1977). P h e a s a n t (1986) states 164 c m as the average height of the I n d i a n m a l e a n d 151.5 c m for the I n d i a n f e m a l e b a s e d o n certain w o r k d o n e b y R . N . Sen. T h e values are right for w o r k e r s b u t are t o o high for f a r m e r s a n d too low for the m i d d l e classes. These r e m a r k s have c o n s e q u e n c e s from the e r g o n o m i c v i e w p o i n t d e p e n d i n g o n w h e t h e r e q u i p m e n t is d e s i g n e d for use b y p o o r farmers, w o r k e r s o r those w h o are well off.

2.2. Southeast Asia In Indonesia, d a t a are less b u t m o r e significant t h a n k s to M a n u a b a (1976), S u m a m u r (1985), H a t tori et al., (1985) a n d H y o d o (1985). P e o p l e are a l m o s t always slightly taller in Bali t h a n in Java, a l t h o u g h this difference is n o t necessarily significant. F a r m e r s are the smallest, at 162 c m in Bali a n d 160 c m ( s o m e t i m e s even 157 cm) in J a v a a n d a weight of a r o u n d 50 kg. M a n u a l w o r k e r s in the c o u n t r y are a b o u t the s a m e height as farmers: 1 6 1 - 1 6 2 c m b u t are slightly heavier (53 kg). C i t y dwellers o n average are 163 c m in J a v a a n d 164

120 cm in Bali and have an average weight of 53 kg. Middle classes have an average height of more than 168 cm and weigh between 60 kg (young people) and 70 kg (older people). Thus, the same differences are found in Indonesia and India, perhaps with a comparative height and weight more favourable to villagers. The height of Indonesian women, like that of men, varies according to the social level. Women in villages are 148 cm tall and weigh 45 kg, women in towns are 153 cm and weigh 45 kg and those in cities are 154 cm tall and weigh 50 kg. Female workers are about 152 cm tall and weight 45 kg. In Thailand, White (1964a) observed an average height of 163 cm for a mean weight of 56 kg for soldiers. Chautipunt (1984) noted 164 cm and 52 kg in male foundry workers, while female workers were 156 cm and weighed 49 kg. In Vietnam, Bui-Thu et al. (1971) noted a height of 158 cm and 49 kg in North Vietnamese workers while female workers were 150 cm and 44 kg. These particularly low values are confirmed by the results obtained by White (1964b) for South Vietnamese soldiers; height 161 cm and weight 51 kg and those obtained by Philippe (1976) from South-Vietnamese students in Paris: height 162 cm and weight 50 kg. The measurements of citizens in other countries of the Indochinese Peninsula are slightly closer to those of Thais. Philippe (1976) found among Laotian students in Paris a height of 163 cm and a weight of 55 kg and in Combodian students a height of 165 cm and a weight of 57 kg. A study by Ong and Sothy (1986) provides data from 225 men in Singapore whose ethnic origins are as varied as this city state: Chinese, Indians and Malayans. The average age was 28, height 166 cm and weight 61 kg. In Papua New-Guinea, Hornabrook (1977) notes an average height of 163 cm and a mean weight of 49 kg in male villagers with a height of 154 cm and a weight of 54 kg for women.

2.3. East Asia Very little data is available for China. In 1972, sample of 263 adults aged 20 to 59 in the ChangPing district, Chin-Chuan province, revealed an average height of 165 cm. A very different population was measured by Lee (1981), that of men

aged between 22 and 55 living in Hong Kong who have an average height of 168 cm. A study by Kay (1961) indicated a height of 164 cm and a weight of 50 kg for South Korean soldiers. The case of Japan is extremely interesting since it has been monitored scientifically for a long time and shows the tremendous influence of economic development on food consumption and biological transformation. As shown by Suzuki (1981), the average Japanese consumer's income has increased six-fold since the start of the century, with a collapse in the forties. Food consumption, which was 2,200 kcal between 1930 and 1940, dropped to 1,500 kcal in 1964, rose swiftly thereafter, then settled at a level of around 2,500 kcal since 1970. Daily protein consumption was around 55 g between 1930 and 1940, dropped to 35 g in 1946, then rose steadily again, exceeding 80 g in 1980. Simultaneously, the m a x i m u m average height of young men rose from 161 cm in 1949 to 170 in 1979 and young women from 151 cm in 1949 to 158 cm in 1979. The m a x i m u m height reached by young men at the age of 24 in 1949 was reached at just 19 years of age in 1979. This very fast growth has slowed down lately. Some authors even contemplate a height limit for Japanese. This concept of a height limit has already been mentioned for other people when growth slowed down, but was never verified. In fact, as Suzuki states " w h e n predicting the body height, one should consider the contribution of heredity and environmental factors during the development process. For instance, the mother's height, her nutritional condition and her health in the broad sense may affect the state of the foetus." The improvement potential for these factors has not been exhausted as yet in Japan. Suzuki's results are confirmed by those of Oshima et al. (1965) who found a height of only 165 cm and a weight of 61 kg in Japanese air force pilots. H y o d o (1985) compared male students in 1932 (height 163 cm, weight 56 kg) with students in 1982 (height 172 cm, weight 62 kg) and female students in 1932 (height 152 cm, weight 50 kg) and in 1982 (height 158 cm, weight 52 kg). The 1932 results may be compared with those for 1949 since this was the period when the nutritional and anthropometric effects of World War II faded out. The same differences of 9 cm will be noted be-

121 tween the extreme periods, with a high level for students, which is general in all countries. The main lesson to be learned from the evolution of the Japanese population is that the height of the "small people", like those in South and East Asia, is by no means unchangeable as indicated in each of these countries by the greater height of younger people in the privileged classes. Although ergonomists nowadays have to take into account the variety of physical measurements in countries throughout the world, anthropologists can forecast a relative homogenization through genetic cross-breeding and, above all, through a greater equality of economic development and the development of food and health resources. However, doctors remain reserved since, although there is hardly any negative relationship between health and small stature, lumber troubles, on the contrary, increase with height. In addition, as will be seen, body strength bears no relation to height.

2.4. Black Africa Anthropometric data from Black Africa are very heterogeneous. Africa is a vast and varied continent. There are very few local specialists in physical anthropology, so data have been collected for a multitude of reasons: nutritional, medical and industrial. There is a tremendous ethnic variety in Africa. There are recordings of small stature group: the male Twas, Zaire pygmies, are 160 cm tall and weigh 51 kg (Ghesquiere, 1972). South African Bushmen, like pygmies, are genetically different from other populations but their precarious living and nourishment conditions influence their anthropometric characteristics. The change in their environment over the last 50 year seems to have been accompanied by an increase in heigth and weight (Tobias, 1972). In the opposite sense, very high statures are recorded in Chad and Sudan; in Fort-Archambault and in a village (Ndila), Hiernaux (1972) noted an average height of 175 cm in Sara-Majingay men. Multiple, high-quality research gives a good idea of the variety of Sudanese populations according to the social environment (Awad E1-Karim et al., 1981; Collins et al., 1976; Ballal et al., 1982; etc.). Farmers on average are 170 cm tall and weigh 57 kg. Female farmers have an average height of 157

cm and an average weight of 44 kg. Urban workers on average are 172 cm tall and weigh 62 kg. Female physical education students are 152 cm tall and weigh 56 kg. Medical students are 177 cm tall and weigh 62 kg. Thus, for a generally tall population, the same relationships are found between social class and height as in India or Indonesia. Professional soldiers are as privileged in Sudan as elsewhere: height 173 cm, weight 62 kg. The remaining data available on Black African countries indicate that the average height for men is 168 cm. Yet when data are available, the mark of the social level is always evident. In Nigeria, Ojikutu et al. (1972) found an average height of 169 cm and a mean weight of 62 kg for both villagers and workers but male students are 173 cm tall and weigh 69 kg while female students are 161 cm tall and weigh 51 kg. In Zaire, Ghesqui~re (1972) found an average height of 168 cm and an average weight of 59 kg in the villages. The figures for workers are similar, 168 cm and 57 kg. On the other hand, students are 172 cm tall and weigh 62 kg. Football players are also 172 cm, but weigh 66 kg. Social traces are perceptible as early as school age. In Kinshasa, at 11 1/2, well-off pupils are 143 cm tall and weigh 35 kg, while the poorest are 132 cm tall and weigh 27 kg. At 17, there is a noticeable difference between young men depending on whether they live in Kinshasa (162 cm, 52 kg) or a village (154 cm, 47 kg). At 17, young females show similar differences: well-off urban classes (162 cm, 53 kg), poor urban classes (158 cm, 48 kg); rural background (155 cm, 47 kg). In Eastern Black Africa, south of Sudan, villagers have an average height of 169 cm and an average weight of 55 kg, in Ethiopia (LangeAnderson, 1972), a mean weight of 58 kg in Kenya (Prampero and Ceritelli, 1969), an average height of 166 cm in Malawi (Nurse, 1972), a mean height of 165 cm and a weight of 54 kg in Tanzania (Davies, 1979). In should be noted that in villages the weight is not steady, due to scarce food resources and intensive work in the rainy season. During this period, in Burkino-Fasso Brun and Bunny (1979) noted an average weight drop of 2 kg in young women (53 ~ 51 kg) and old women (48 ~ 46 kg) and in old men (59 ~ 57 kg). This difference reaches 3 kg in young men (61 ~ 58 kg).

122 In all seasons, for both sexes, the weight of young people (20-39 years) is more than that of older people (40-59 years). All these phenomena are typical of populations living at the limits of food resources. The black population of South Africa is famous for a particular group of people, the Bantu miners who work in the gold mines. These miners constitute a very homogeneous group owing to the very strict selection which excludes, in particular, men weighing under 50 kg (Strydom et al., 1971). The average height of the miners is 168 cm (Morrisson et al., 1968). Their weight when recruited is 57 kg and reaches 61 kg after training (Wyndham et al., 1962), a fact that will be discussed further on. The average height of those under 50 kg who are excluded is 158 cm and their average weight is 47 kg. Female Bantus' measurements are not known. There is no significant difference between Bantu ethnic groups (Pedi and Venda (Van Graan et al., 1972)). The study of Bantu gold miners was done by the Human Sciences Laboratory Transvaal and Orange Free State Chamber of Mines, Johannesburg, Transvaal, successively headed by C.H. Wyndham and C.B. Strydom. Eighteen articles published between 1963 and 1972 were studied whereas, for the rest of Black Africa, only thirteen articles published by various authors between 1969 and 1982 were available. C.T.M. Davies and his former students also made a considerable contribution.

be more precise, in urban life, height and weight increase according to the scale of socio-occupational categories. Workers at the U.N.A.M. (National University) are 164 cm tall (Casillas et al., 1978) while the teaching staff of a U N A M Institute measure 172 cm on average (Casillas and Vargas, 1979). Medical students are 169 cm tall at the age of 20 (Casillas et al., 1978) and 170 cm at the age of 25 (Vargas et al., 1975). In Brazil, thanks to Siqueira (1976) we know that Sao Paulo industrial workers are 168 cm tall. Such a difference with Mexico City workers is due to both ethnical and nutritional reasons. On the other hand, in 1962 Newman reported a height of 154-159 cm in various Amazonian Indian tribes and Baker and Weiner (1966) a height of 159 cm and weight of 59 kg for Warao Indians. Here again, ethnic causes of small stature are linked to nutritional causes related to the difficult survival of these tribes. Besides these data, the measurements taken by Dobbins and Kindick (1967) from military personnel belonging to 18 Latin American countries during training in the USA may be noted: height 166 cm and weight 63 kg. It would be interesting to know the method used to select this type of population in order to obtain the full significance of these data.

2.6. Mediterranean periphery and neighbouring countries

2.5. Latin America The anthropometry of Latin America is badly known, except for Mexico which has a major school of anthropology. Pharmaceutical industry workers in the Mexico City area are 164 cm tall (Casillas and Vargas, 1979) and those of the textile industry in the same area are 161 cm (Cuellar et al., 1980). "Mestizo" workers in Jalapa are 162 cm tall and those in Cordoba 159 cm tall (Faulhaber, 1971). These data can be compared with those obtained by Comas (1971) in a Maya village: average height 153 cm (see also Comas, 1966). A basic phenomenon, which is truer as the country is poorer, is seen here again: the poor farmer is the smallest and lightest, while height and weight increase with industralization and urbanization. To

It might appear odd not to divide Northern Africans, Southern Europeans and Far Western Asians (Near East) into three distinct sections, but a common history, extensive chmatic similarities and common ethnic origins (Indo-European) lead to very close anthropometric features in the peoples of the Mediterranean area. It may be noted that the height of young workers is similar (169 cm) in Algeria (Bourliere and Parot, 1962; Chamla, 1972; Rebiff6 et al., 1974); in Egypt (El Ghawabi et al., 1976); in Morocco (Rebiffr, 1974); in Tunisia (Rebiff6 et al., 1974; Sahbi, 1985). Similar values are found in Southern Europe: 170 cm in Greek soldiers (Hertzberg et al., 1963), 171 cm in Italian soliders (Hertzberg, 1963), but only 168 cm in male workers in the same country

123 and 157 cm in female workers (Locati, 1973), 169 cm in Turkish soldiers (Hertzberg et al., 1963), 167 cm in Iranian soldiers (Noorani et al., 1971), 168 cm in iron and steel workers in the same country (Shahnawaz and Tuxworth, 1978), but only 164 cm in poor Iranian farmers ( B r u n e t al., 1979). In Spain, Rebiff4 et al. (1974) found 167 cm in male workers and Commalo-Malo and Pujol (1965) 157 cm in female workers. Thus, Spaniards seem slightly smaller, yet this should be treated with caution in view of the influence of the socio-occupational background, the regional origin and the trend of improved living standards. The values already found some time ago by Pimentel in poor farmers in Northern Portugal (164 cm) and in Porto workers (165 cm) should be compared with those he found in young men in Lisbon (167 cm) and those reported by Rebiff6 in 1970 in a population of workers of various ages (167 cm). On the other hand, the values reported in France are relatively higher: Ducros (1955) reported 171 cm for air force personnel: 172 cm for male and 160 cm for female car purchasers measured in 1983 by Rebiff4 et al. In fact, when considering male workers in the French Mediterranean regions in particular, 170 cm is found. As such, it is possible to state that workers in the Mediterranean region (as a whole) have an average height of 169 cm, with extreme values of 167 cm in Portugal and 170 cm in Mediterranean France, indicating remarkable anthropometric homogeneity.

2.7. Industrialized countries in Northern Europe and North America The scope of the present study does not include a thorough analysis of the abundant and often described anthropometric data from industrialized countries in Northern Europe and North America. Special reference could be made to Pheasant's book (1986) containing information about Britons of all ages (adult men 1740 ram, 74.5 kg, women 1610 ram, 62 kg), Americans (adult US men 1750 mm, 78.4 kg, women 1625 mm, 64.7 kg), Germans (adult men 1745 mm, 76.2 kg), women 1635 mm), Swedes (men 1740 mm, women 1640 mm, 59.3 kg), Poles (men 1695 mm, women 1575 ram).

2.8. Main factors influencing height Regional and national data as indicated previously suggest that differences are ethnic above all else. In fact, long-standing data already indicated that in one or two generations, Japanese who emigrated to the United States, Indians to Great Britain and North Africans to France reached a height comparable to the people of their adopted country. There are also signs of evolution on a national scale, related to rising living standards. The height increase between 1880 and 1960 was about 1 mm a year in all industrialized countries (Tanner, 1966). In Japan the change was particularly fast between 1957 and 1967:3.3 mm a year and still very high from 1967 to 1977:1.9 mm a year. The question as to whether this growth has a limit, according to the genetic potentialities of all peoples, is rather academic and still very controversial. When the height of a population is measured in terms of different age brackets, there is a drop with age which, up to the age of 50, corresponds to the secular height increase. After 50, the drop is more marked due to osteo-articular deterioration. In poor sectors of industrially developing countries, no secular growth is noted, but the height drop linked to osteo-articular deterioration takes place earlier. Weight increase with age is a phenomenon specific to rich countries and rich classes in poor countries. Sahbi (1985) indicated this for Tunisian and British miners (Fig. 1).

WEIGHT

76

76

72

ANGL.

~ ,0" . 0

.Q 0 ,-0

68

72

.°o..o." ~."

68

**

.,Cr.0"

64 .,(~

64 TUN.

60

60 56

SS ](~)1 I I I I I I I I,~l I I I 16 18 20 22 2'4/25 30 315 40 45 29 34 39 4 4 4 9

AGE

Fig. 1. Weight related to the age of English miners (Ward, 1952-1962) compared to Tunisian miners (1981) (after Sahbi, 1985).

124 The heigth difference between males and females is around 6-8%. In fact, this relation would be known more precisely if male and female samples were properly .matched, but this is rare. Height differences between socio-occupational classes are classic phenomena (Trrmolirres and Boulanger, 1950) but are not always clearly indicated in the statistics from various countries and anthropometric studies. A recent investigation of the French population by Rebiff6 et al. (1983) shows considerable differences (Table 2) since this is more than 7 cm between extreme groups. These differences may be compared with those observed in Sudan (8 cm), Indonesia (9 cm), India (10 cm) and Mexico (10 cm). For a medium sized country which has been extensively centralized for some considerable time, like France, Rebiff6 found important regional differences in 1983 (Table 3). The maximum difference is 4.5 cm between the North and West, which could be explained by the ethnical variety and the degree of urbanization. These data could be compared with those of Malhotra (1966) which show (Fig. 2) an average difference of 6 cm between the average stature of men in Southern India (163.5 cm in Kerala and Madras) and in Northern India (168.5 in Punjab and Delhi). For Malhotra, the height difference is explained by very unequal nutrition: 2000 calories and 62 g of protein in the South, 3300 calories and 91 g of protein in the North. In fact, improved nutrition acts on height during gestation, childhood and adolescence and probably for several generations. In certain regions of France, espe-

TABLE 3 Mean standing heights of French people of both sexes following their birth region (Rebiff~ et al., 1983) Regions

Males

Females

North East Ile de France West South-West South-East Center East Foreigners, overseas departments and territories

174.1 173.1 172.7 169.6 170.5 171.3 171.8

161.2 161.2 160.5 158.0 160.0 160.6 161.3

171.2

159.4

cially the West and Centre, the living standards of some of the population at the start of the 20th century are comparable to the poor classes of developing countries at the present time. For complex historical, social and cultural reasons, the general rise in living standards has determined nutritional and anthropometric changes which appear sooner or later depending on the country or the region.

CALORIES PROTEIN(g) 3300

-

3100 -

I

[ ] CALORfES

~'~

O0

3000 2900 -

TABLE 2

2800

Mean standing height of French people of both sexes following the socio-professionalcategories (Rebiff6 et al., 1983)

90

-

2"/00-

I

0o

2000 -

Socio-professional catrgories

Height (cm) Men Women

Farmers Industrial workers Clerical workers and commerce Low management technicians Managers professionals No occupation

167.5 170.8

157.4 159.1

172.6

160.4

o

-

Z400 2300 .

2200173.2 174.6 170.9

160.7 162.7 161.0

• 70

2t00 -

|

s'r^'ruR

00

i\ l

o

n, llllfl ~..-'"

o~"

Madras Gujarat Bengal Uttar Punjab Kerala Bombay Bihar Pradesh Delhi

110° ~ 108

i''° 1~

105

1 t'4< :lU

Fig. 2. Effects of nutrition on stature in different regions of India (from Malhotra (1966)).

125 3. S E G M E N T A L WORKSTATION

MEASUREMENTS DESIGN

SITTIN HEIGHT(ram)

AND

55

54

53

_~

050-

The importance of height measurement is significant since this dimension is closely correlated to every segment of the body. As such, it is possible to predict, with reasonable accuracy, every segmental measurement on the basis of height. For instance, according to Rebiff6 et al. (1983), the correlation with the standing height is very high (> 0.800), for the sitting height (0.829), the leg height (0.887) and that from the popliteal pit to the ground (0.830), the length of the upper limb (0.813) and the forearm (0.805). The correlation remains high ( > 0.700) for the length between buttock and popliteal pit (0.747), the arm length (0.692) and the upper limb reaching distance. Predictions improve as populations become more ethnically homogeneous. Figure 3, taken from Pheasant (1986), shows that the sitting height is between 51 and 53% of the stature of people of European and European ascent and Indo-Mediterranean people. It is between 50 and 52% in Subsaharian African peoples and between 53 and 55% in Fareastern peoples. It could be said relatively

o~

900

[] [on

850

~-" e uo/ . ~,|OOoo / 0ot~

-

~,~u

~ 50

-~-~

mua

o 1600

I

J

I

i

1650

1700

1750

1800

Fig. 3. Ethnic differences in the relationship between average sitting height and average stature in samples of adult men (after Pheasant (1986)). key: • European (including samples of predominately European descent), o Indo-Mediterranean, [] Far Eastern, and • African.

that Africans have a shorter trunk and longer limbs and Asians have a longer trunk and shorter limbs than Europeans. In Table 4, the main measurements of four samples of male populations are given as an example: 1,500 French people measured by Rebiff6 et al. (1983), 1,940 Hong Kong Chinese measured by Lee (1981) and described by Courtney and Wong (1985), 485 Bantu miners measured by Morrison

TABLE 4 Anthropometric dimensions of four continents male population samples

Number Weight in kg Standing height Sitting height Sitting eye height Sitting shoulder height Sitting knee height Sitting poplital height Sitting thigh clearance Buttock knee length Buttock poplital length Foot length Acromion-elbow length Elbow-hand length Upper-limb length Maximal reach Functional reach Abdominal depth Breadth across hip

French males

Chinese males

Bantu male workers

Mexican industrial works

Dim. (cm)

Dim. (cm)

Dim. (cm)

Dim. (cm)

1500 74 171.6 91.0 79.6 62.1 53.2 42.3 18.1 59.3 48.0 26.0 35,8 46.9 77.0 88.3 76.8 27.1 36.8

Dim. in 7~ of st. height

Dim. in 7o~of st. height

1940

530 464 362 310 247 346 280 209 273 449 515 448

168.0 90.1 78.2 60.9 49.4 40.2 12.8 55.2 44.5 25.0 34.0 44.5 73.0

536 465 363 294 239 329 265

485 60 168.4 86.2 74.7 56.6 53.5 41.6 13.7 63.7

512 444 336 318 247 378

160.5 84.7 74.9 56.3 53.3 (?) 42.6 (?) 15.7 55.1 45.7

26.2

31.4

Dim. in 7~ of st. height

50

201 265 435 76.9

19.0 33.3

Dim. in 7~ of st height

457 27.4 33.8

528 467 351 332 (?) 265 (?) 343 285

126 et al. (1968) and 50 Mexican textile workers measured by Cuellar et al. (1980). In addition, the ratios between some of these measurements and statures were calculated when there was a high correlation. As such, it can be ascertained that on average Hong Kong Chinese have a relatively higher sitting height and relative shorter limbs than French people while Bantus have a relatively lower sitting height but relatively longer limbs than French people. The measurements for Mexicans are proportionally the same as those of the French, except perhaps for comparatively longer legs. This table indicates the systematic differences reported for some time which may be critical in ergonomic practice. It is not so much a matter of measurements concerning the trunk: the average height of eyes above the seat only differs by 2 cm in the four populations. Yet when examining a group of men 1.70 m tall in each country or region, a sitting height of 87 cm is found in Black Africans, 89 cm in populations of European or Indo-European origin, 90 cm in Chinese, Koreans and Vietnamese and 92 cm in Japanese. As for limb dimensions, the differences are greater. In Table 4, for the knee height above the ground, the gap is 4 cm and for the buttock-knee length 8.5 cm. In order to simplify work relative to ethnic variations, the very practical tables prepared by Pheasant (1986) can be used, although the unification influence is not fully convincing, in view of the varied sources (general population, soldiers, workers). Besides, these tables includes data about India, Japan and Hong Kong but give no information about Latin American countries where the Indian origin often prevails, nor any concerning Black African countries. Pheasant quite rightly demonstrates that the anthropometric dimensions of Asian, and especially Japanese, populations alter with their higher income and their resulting nutritional improvement. Not only does height increase, but limbs become relatively longer, which brings their proportions closer to those of European and Indo-Mediterranean origin. Yet the latter evolution is a lot less marked than that of the height. In order to design workstations, and especially car drivers' seats, it is vital to know the actual

220-220-225

~-132f4-143,4

_1 I_ 55-0o-05 Fig. 4. Bidimensional manikin of a male population of French bus drivers estimated for 1995 (5th, 50th, 95th centiles) (after Guillien and Rebiff6 (1986)).

population of users, while allowing for ethnic origin, sex, age and socio-occupational background. In a single country, regional differences which may coincide with ethnic differences could be taken into account. The measurements of the user population may be evaluated through calculation methods (Roebuck et al., 1975; Pheasant, 1986) when the population's characteristics are known in terms of the sources of the variations stated previously. In the case of drafting or CAD, it may be useful to have a two-dimensional manikin like the one proposed by Guillien and Rebiff6 (1986) (Fig. 4). In this figure, the measurements of every body segment are those of truck drivers (estimate of a male population working in France in 1995 (stature 172 cm), considering the 5th, 50th and 95th centiles. Figure 5 indicates the "comfort angles" for a driver's seat. Such considerations are nothing new (Wisner and Rebiffr, 1963b), but their repeated use and the thought process used indicates that they may be generally practical as long as most of the characteristics of the actual user population are taken into account (Courtney and Wong, 1985). As such, a driving seat would be designed for a man measuring 165 cm and a woman measuring

127

20"< AI< 95 "< A2 < 95 "< A3 < 86"< A4 < 0"< A5< 0"
30" 120" 135" 105" 45" 20" ABDUCTION

A

7

~

M

FLEXION 170"< A7<190" EXTENSION RADICAL 180"< A7 < 190" CUBITAL INCLIN A4

A

T S Fig. 5. Driving comfort angles (after Rebiff6 et al., 1974).

154 cm, if the whole of mankind were considered; but when this is limited to the world's car buyer population, the driving seat would be designed for a man 1.70 tall and a woman 1.60 m tall. An interesting practical remark can be deduced from these considerations. Products requiring a fairly high income from their owners, such as cars, suit both the general population of industrialized countries, where women drive nearly as much as men, and the rich population of industrially developing countries. It should be noted that, as regards craft and agricultural tools and machines, the choice of imported equipment m a y be an error, since the population taken into account for manufacturing tools and machines in industrialized countries has a height between 170 and 173 cm (including Japan), whereas in South and East Asia and Latin America, most villagers are close to 160 cm tall and women are 150 cm. For these populations, local or regional products are much more suitable than goods designed on the basis of an international scale pattern. More generally, the accurate or even approximate knowledge of the population's measurements helps with the design, purchase and adaptation of the most sophisticated and modern technical device as well as the most simple and traditional one, in order to avoid wrong postures which would soon become unbearable and would help workers benefit from the most advantageous biomechanical relations. It should be noted that abundant subject matter literature can be used as long as a rule of three is applied to the measurement of the

populations to be supplied, as well as the measurements considered by the author of the documentary source. Sex, age and the socio-occupational background should be given the utmost consideration in the calculation by relating the population measured to the potential user population.

4. WORKING POWER AND LABORIOUSNESS OF TASKS 4.1. Overall considerations and methodological directions A l t h o u g h b i o m e c h a n i c a l a d v a n t a g e s are valuable, the critical element is still human body strength in most work situations in I D C s since the other energy sources are scarce and expensive. In what follows, physical strength will be referred to in terms of aerobic power or m a x i m u m oxygen uptake expressed in litres per minute (max VO 2 (oxygen uptake) 1/min) and m a x i m u m oxygen consumption in millilitres per kilogramme per minute (max VO 2 m l / k g / m i n ) . In this case, weight is that of the whole body. This expression is acceptable for thin populations as found in I D C villages. It is more questionable for better fed populations in industrial countries or industrial or urban regions in some IDCs. In the latter case, the lean body weight should be used. This can be calculated on the basis of underwater weighing, taking into account the residual lung volume or, more conveniently, on the basis of the skinfold at

128 2 or 3 points of the body according to well-tried methods (Sloan and de Weir, 1970). The tricipital spot is probably the best. Located half-way between the elbow and shoulder at the back of the arm, it is easily accessible in men and women of all cultures. The direct measurement of oxygen consumption is a difficult operation, requiring a costly and complex device and skilled staff. In theory, the physical activity during the test requires heavy equipment: ergometric bicycle, treadmill, etc. In actual fact, a reasonable approximation can be obtained by measuring the heartbeat which, within ceratin fimits, is closely related to VO 2. The reference activity itself can be simplified by using a step test or, better still, a self-paced walking test under three conditions (walking rather slowly, normally and rather fast over three distances of 120 m (Davies, 1979)). These measurements in a sub-maximal situation require calculation of the maximum VO 2 by extrapolation. In warm countries, measurements should be taken very early in the morning to avoid the influence of temperature on the heartbeat which, obviously, would distort relations between heartbeat and VO 2. Heartbeat can be measured through a portable heartbeat recorder. As we know, it is possible to obtain information about the workload by taking the pulse of a sitting person for the last 30 seconds for the 1st, 2nd and 3rd minutes following stoppage of work (Brouha, 1967). Calculation of VO 2 becomes rather risky in such conditions; yet it is noticed that certain assessments of a population's physical capacity can be obtained with just a measuring tape, scales and a stopwatch.

4.2. Data concerning aerobic power in Africa Literature provides valuable information about the probable values of the maximum VO 2 according to peoples' characteristics. Here again, the significant work of C.H. Wyndham's and N.B. Strydom's Laboratory in Johannesburg, published between 1963 and 1973, is available. Newly-recruited young miners weigh an average of 57 kg, have a maximum VO2 of 2.41 l / m i n , which gives a max VO 2 per kg of 42 m l / k g / m i n (Wyndham and Heyns, 1969). Applicants elimi-

nated because they were less than 50 kg had an average weight of 47 kg and a m a x V O 2 of 2.12 1 / m in, which gives a max VO 2 per kg of 45 m l / k g / m i n (Strydom et al., 1971). These eliminated applicants have a physical capacity per weight unit slightly higher than those selected (45 compared to 42 m l / k g / m i n ) but their lower weight explains a total max VO 2 of 2.12 1/min only, suggesting that they would not reach a total max VO 2 of 2.5 1/min after training. A vital result, obtained by Wyndham et al. (1962) is the significant effect of training, a period in which nutrition, previously lacking in calories and proteins, is replaced by nutrition of 4000 k c a l / d about 15% of which comes from proteins. The diet is combined with a significant physical activity. As such, the physical capacity of 20 recruits, shown in Table 5, expressed in the total max VO 2, increased by 18% in one month and 22% in four months. This demonstrates that, at least in the case of young men, capacities can be increased to a considerable extent in a short period of time through plentiful and good-quality nutrition. A human resources policy must take this essential fact into account. The study of the various samples of miners confirms this result (Wyndham et al., 1963). A trained worker weighs about 60 kg and has a total max VO 2 of 2.9 1, i.e. a maximum VO 2 per kg of 48 m l / k g / m i n . Some exceptionally strong miners weight 65 kg and have a max VO 2 per kg of 3.2 1, i.e. a maximum VO 2 per kg of 49 m l / k g / m i n . As is seen in these miners, good nutrition and intensive physical exercise initially increases the max VO 2 per kg to around 50 m l / k g / m i n . An additional increase in the total physical capacity is only obtained through a weight increase in the muscular mass. TABLE 5 Variation in the physical capacity of 20 recruits in South African gold wines in terms of their nutrition and physical activity (according to W y n d h a m et al. (1962))

W h e n hired After I m o n t h After 4 m o n t h

Weight (kg)

Max VO 2 (l/win)

Max VO 2 (ml/kg/min)

55 58 58

2.32 2.73 2.83

42 47 49

129 Going back to the characteristics of Bantu males who are not miners (Wyndham, 1973), the average weight of villagers is 57 kg with a total max VO2 of 2.25 1/min and a maximum VO2 per kg of 39.5 ml/kg/min, which both indicates poor nutrition and a rather low physical activity which is probably related to feeding limits. The average weight of city-dwelling males is 63 kg with a maximum VO2 of 2.58 1/min and a maximum V O 2 per kg of 41 ml/kg/min, which indicates both better nutrition and greater physical activity than villagers. Differences between ethnic groups (Venda and Pedi) are very slight and probably related to differences in food resources in the villages. A special study of Venda populations (Van Graan et al., 1972) shows that in the village, weight increases slightly at adulthood (58 kg) then drops again after the age of 45 (56 kg), which is typical of restricted nutrition. On the other hand, city-dwelling Vendas are lighter between 16-25 years (60 kg) then reach and remain at 65 kg which indicates more abundant nutrition. The maximum V O z per kg increases in both villagers and city dwellers from youth (40 ml/kg/min) to adulthood (42-43 ml/kg/min) then drops again after the age of 45 years, especially in urban Vendas (38 ml/kg/min). Table 6 shows the variation in aerobic power according to age, for one of the black South African populations, that is more favourable than that generally admitted in Europe. This variation corresponds to the fact that properly fed heavy workers were concerned. Wyndham et al. (1963) show that Bushmen have a high total V O z of 2.39 1/min for a low weight (51 kg) since their maximum VO2 per kg is

TABLE 6 Variation in the physical capacity, according to age, of Venda males living in South African cities (according to Van Graan et al. (1972)) Age (years)

Weight (kg)

Max VO 2 (l/rain)

Max VO 2 (ml/kg/min)

16-25 26-35 36-45 46-55

60 67 65 65

2.4 2.83 2.56 2.47

40 42.5 39 38

TABLE 7 Variation in the physical capacity of Tanzanian sugar cane cutters according to their anaemia rate of parasitic origin (according to Davies (1979)) Rate of anaemia

Hemoglobin rate (g/100 ml blood)

Maximum VO 2 (l/rain)

Maximum VO2 (ml/kg/min)

No anaemia Mild anaemia Severe anaemia

14.5 9.2 6.7

2.88 2.20 1.90

52 43 35

high (47 ml/kg/min). This indicates their high level of training without which they probably could not survive. It should be stressed in this respect that physical strength bears no relation to height but to weight in as much as adiposity is low (< 12% of total weight). Taking into account the results obtained in South Africa from a very homogeneous and specific population, with substantial samples and very accurate techniques, the results obtained in other Black African countries in more difficult conditions can be interpreted. The results obtained from Bushmen may be compared with those of Zaire pygmies: weight 51 kg; total maximum VO2 2.4 1, maximum VO2/kg 48 m l / k g / m i n (Ghesquirre, 1972). In Black African regions where nutrition is most restricted, very low total maximum VO2 values, less than 2.1, are found in Ethiopia (Lange-Andersen, 1972), close to 2.2 1 in Sudanese villagers (Awad el Karim et al., 1981). Between 2.5 and 3 1/min are found for the maximum VO2 of Kenyan villagers (Di Prampero and Ceritelli, 1969) (2.8 1/min), those of Nigeria (3 1/min) (Ojikutu et al., 1972) of Zaire (2.5 1/min) (Ghesquirre, 1972) and of Tanzania. In Tanzania, a study by Davies (1979) shows substantial variations in sugar cane cutters. Those who cut a lot of cane reach 3.2 l/rain for the total maximum VO2 and 51 m l / k g / m i n for the maximum VO2/kg. The values for average cutters reach, respectively, 2.95 1 and 48 m l / k g / m i n and for low-rate cutters 2.80 1 and 47 ml/kg/min. Old cutters have a total maximum VO2 of 2.76 1/min and a maximum VO2 of 43 m l / k g / m i n . Similar differences are reported in terms of the blood hemoglobin rate (Hb) related to bilharziosis and malaria (Table 7).

130 A study carried out in Sudan (Collins et al., 1976) where villagers were classed according to their level of infection by bilharziosis and where anaemia was mild is less conclusive. In other countries, for cane cutters in Guatemala and female tea pickers in Sri Lanka, a sharp drop in output is reported along with anaemia. This is linked to parasitoses, vegetarian nutrition and frequent pregnancies in women. As regards other social classes, very high values of maximum VO 2 are found in heavy industry workers in Nigeria (Ojikutu et al., 1972) (total maximum VO 2 3.35 1/min, maximum VO2 57 m l / k g / m i n ) , but usually total VO 2 values between 2.5 1 and 3 1 are found in workers of various Black African countries: light industries in Nigeria (Ojikutu et al., 1972; maximum VO 2 = 2.55 1, VO2/kg = 47 m l / k g / m i n ) and Zaire (Ghesqui~re, 1972; maximum VO2: 2.50 1, VOz/kg = 42 m l / k g / m i n ) , Zaire carriers (maximum VO2:2.56 1, VOz/kg = 48 m l / k g / m i n ) . Nigerian students have a maximum VO 2 of 3.03 1/min (maximum VO 2 kg = 45 m l / k g / m i n ) (Ojikutu et al., 1972). Zairean students have a maximum VO 2 of 2.75 1/min (maximum VO2/kg = 44 m l / k g / m i n ) (Ghesqui+re, 1972). Zairean professional footballers have a total maximum VO 2 of 3.46 1/min ( V O 2 / k g = 53 m l / k g / m i n ) (Ghesqui6re, 1972). Sudanese soldiers have a total maximum VO 2 of 3.54 1/min (50 m l / k g / m i n ) which again indicates their excellent nutrition and their good physical condition (Awad el Karim et al., 1981). It should be noted that, contrary to what is commonly thought, it is not necessarily the people whose work involves considerable effort who have the best physical capacities. These are more prevalent in young men in privileged positions in each country, with good nutrition and a good physical condition such as students, sportsmen and professional soldiers. As regards women, for the whole of Black Africa only the maximum VO 2 measurements for 17 Nigerian female students are available and these are hardly significant (VO 2 = 1.70 1/min) (Ojikutu et al., 1972). It is known that calculating the maximum VO2/kg by dividing total maximum VO2 by the weight is biased when the people are not very thin.

Generally in Africa the lean weight is 12% less than the total weight in the poorest men and 17% less for those who have the best nutrition, corresponding to the extent of body fat. These values are relatively high compared to those noted in other parts of the world, especially in Asia. Yet there is nothing to indicate that the groups studied can be compared from one continent to another. Wyndham (1973) sums up the various influences on physical capacity mentioned previously (age, sex, nutrition, parasitoses). He also emphasizes that the simple fact of being confined to bed can cause a healthy person to lose 27% of maximum VO2. In addition, he demonstrated that for all the people of the world, the maximum VO 2 levels is similar in every professional class. Young men with a significant physical activity (soldiers) are between 3 and 4 l/min. Young industrial workers in developed countries are between 3 and 3.3 1/min as are young men from privileged backgrounds. All these values relate to well-fed people.

4.3. Data concerning aerobic power in Asia Wyndham's comments mainly concern industrial populations and certain African populations. Theoretically they are also true for Latin American Indians or for South and Southeast Asia. These latter regions, with one third of the world's population, have mostly ill-fed and undernourished inhabitants. As such, the situation is very different in South and East Asia where a total maximum VO 2 over 3 1/min is only reported in Himalayan Sherpas (total maximum VO 2 = 3.9 1/min). This high value is obtained despite a low weight (54 kg) through intensive training at high altitude. Pugh (1964) reported the drop in Everest climbers' maximum VO2 in terms of increasing altitude (Table 8). Conversely, men like Sherpas who have been trained as carriers since childhood in villages at an altitude of 5000 metres can reach maximum VO2/kg values 30% higher than those they would reach at sea level and can reach or exceed a maximum VO2/kg of 70 m l / k g / m i n (Nag and Sen, 1978; Nag et al., 1978a).

131 TABLE 8 Variations in physical capacity in terms of altitude (according to Pugh (1964)) Altitude

Maximum VO 2

% drop

Sea level 2000 m 4000 m 6000 m 8000 m

50 46 40 33 20

0 8 20 34 46

In India, a high maximum V O 2 is quite exceptional since only one group of well-trained soldiers achieved 2.7 1/min (Sengupta et al., 1977). Students reach 2.5 1/min (Maitra, 1979). Industrial workers (Sen and Sarkar, 1979) and porters (Samanta and Chatterjee, 1981) are between 2 1 and 2.5 1/min. Farmers (Nag, 1981), miners (Chakraborty et al., 1979a), railway maintenance workers (Nag et al., 1985) hardly exceed 2 l/rain. In particular, it should be noted that miners have a mean weight (49 kg) below the recruitment exclusion level in South Africa and have a total maximum oxygen uptake (VO2) of 1.9 1/min, 25% below that considered as minimal in South African mines. In fact the muscular capacity expressed by the maximum VOz/kg is similar in Africa and Asia and is between 40 and 45 m l / k g / m i n as in any young, thin, trained man. It may be noted that the maximum VO2/kg values obtained by dividing the total weight are proportionally lower for Indians since they are thinner than Africans (12-17% body fats) (Lange-Andersen, 1972; Ojikutu et al., 1972). The body fat rate is between 5 and 10% in India for farmers (Nag, 1981) and porters (Nag and Sen, 1978) with an average of 7%. In Indian women, body fats are between 13 and 19% (Nag et al., 1978b). What mainly distinguishes Indians and Southeast Asian from Africans or people elsewhere in the world is their low weight which is around 43 kg in poor farmers, 49 kg for miners and railway workers, 50-55 kg for industrial workers and porters, 53 kg for students and 60 kg for soldiers. The only workers with a comparatively high weight (62 kg for 170 cm) are mine rescue workers (Guharay et al., 1979) who have a particularly low maximum VO2 uptake (VO2) (1.8 1/min) which

TABLE 9 Drop in actual physical capacity with increasing heat load (according to Sengnpta et al. (1977)) Total maximum VO2 (l/rain) Comfortable climate Very hot and dry climate Warm and wet climate Very hot and dry climate Very hot and wet climate

% drop

2.66

Maximum VO2/kg (ml/kg/min)

45

2.54

5

43

2.40

10

41

2.37

11

40

2.29

14

39

does not indicate a good training level (max VO2/kg: 29 ml/kg/min). Most of the populations of IDCs have tropical climates. Their actual working capacity is limited by heat (Sengupta et al., 1977); a study of professional soldiers with an average weight of 59 kg shows the comparative drop in total VO2 and VO2/kg with heat (table 9). Sen and Sarkar (1979) produced comparable results (Table 10) This shows to what extent physical activity in a warm country can be reduced in terms of the heat environment, especially in people with a low capacity and in the case of substantial efforts in people with a normal capacity. It is obvious how useful air conditioning can be for health and output as was demonstrated by Wyndham and Brouha. TABLE 10 Drop in actual body capacity with increasing heat load (according to Sen and Sarkar (1979)) Climate

Comfortable C.E.T. 21.3 o C Warm C.E.T. 27.1° C Hot C.E.T. 32.4° C

Total maximum VO2 (l/rain)

% drop

2.31

Maximum VO2/kg (ml/kg/min)

41

2.05

11

36

1.81

22

32

132 T A B L E 11

T A B L E 13

Reduction of physical capacity with age in Indian villagers (according to Nag (1981))

Relations between the workload characterizing various tasks and the body capacity of the workers who carry them out (according to Sen and Sarkar (1979))

Age (years)

Total weight

(kg) 20-29 30-39 40-49

46 43 42

Total max VO 2 (l/min) 2.16 1.98 1.76

% loss total max VO 2 8 19

Min VO 2 (ml/kg/ min)

Max pulse

47 46 42

188 184 173

It is easy to see how an expression such as "tropical laziness" may be based on a misunderstanding of the biological effects of poor nutrition, high heat load and, usually, various parasitoses. The results obtained by Nag (1981) on the reduction of capacities through a g e in an Indian village are significant (Table 11). The 8% loss in the 30-39 year age bracket and the 19% loss in the 40-49 year bracket are almost fully explained by weight reduction when lean weight is taken into account since body fats increase by 4-7% with age. Sen and Sarkar (1979) obtained more favourable results in Indian industrial workers (Table 12). Losses in total maximum VO 2 are 50% less and it may be noted that the second bracket covers 40 to 59 years of age instead of 40 to 49 years of age. Moreover, Indian industrial workers put on weight with age, which suggests a sufficient nutritional intake for physical work and a comparatively higher maximum VOz/kg value when lean weight is taken into consideration These results may be compared with those obtained in South African rural and urban Pedis and Vendas where the total max VO 2 drop is slight or non existent up to 50 years of age and with those

TABLE 12 Decrease of physical capacity with age in Indian industrial workers (according to Sen and Sarkar (1979)) Age (years)

Total weight in kg

Total max. VO 2 (1/min)

20-29 30-39 40-59

54 55 62

2.46 2.33 2.13

Total loss in max. VO2 5 13

Min VO 2 (ml/kg/min)

46 35 35

Physical load

Total m a x i m u m VO 2 (l/rain)

Maximum VO 2 (ml/kg/min)

light medium heavy very heavy extremely heavy

1.67 1.91 2.27 2.50 3.17

31 36 41 42 56

obtained from South African miners of European origin in whom the VO 2 remains above 3 1 until they reach the 50 to 59 age bracket. Sen and Sarkar (1979) also show a strong relation between the physical load related to every task, the total maximum VO2 and the maximum VO2/kg of the workers who carry them out (Table 13). These results may be compared with those from Tanzanian cane cutters studied by Davies (1979). The average max. VO 2 of Indian industrial workers studied by Sen and Sarkar (1979) is 2.31 1/min. These values are below the average values of African industrial workers (2.55 1/min) or trained South African miners (2.9 1/min). In particular they are below those found by and presented by Astrand and Rodahl (1970) in Swedish physical education students (4.11 l/min). Kukkonen-Harjula and Ravramaa (1984) in a Finnish lumberjack population (3.94 l/rain) or even Hedberg and Niemi (1986) in Swedish truck drivers (2.8 1/min). These data stress the absolute necessity for better definition of work laboriousness scales in terms of the characteristics of world populations as will be seen later on. There are less Indian data on w o m e n than on men. Yet these studies give an evaluation of Indian women's capacities at a low level. This level is linked to the low weight both in female villagers (39 kg) (Nag et al., 1978b) and in female students (45 kg) (Maitra, 1979; Oberoi et al., 1983). It is also linked to the rather low level of the muscular capacity expressed by maximum VO2/kg: between 30 and 35 m l / k g / m i n in female villagers as in female students. As such, a total maximum VO2 of between 1 and 1.3 l / m i n is reported in poor village women and 1.5 l / r a i n in female students.

133 Indian physiologists (Nag et al., 1982; Goswani et al., 1984) made an extensive study of the physical capacities of disabled persons, especially paraplegics. With an average weight of 40 kg, the paraplegics examined had a maximum VO2 of between 1 and 1.3 1/min. It is known how significant these data are for the design of motorless wheelchairs since an excessive and sustained effort could provoke heart failure.

4.4. Permissable workloads There is tremendous confusion in the definition of the categories of physical loads laboriousness. In fact, as seen previously, considerable differences in capacity are noted between workers from one country to another and in the same country between one social group and another, that a universal rule could seem delusive and dangerous. Yet the demands of international work organization require some clarification in this field. The most reliable criterion is the heartbeat since it takes into account both physical capacity and heat conditions. However, it is known that the maximum heartbeat rate, and probably the maximum tolerable heartbeat rate, drops with age. It is more or less universally admitted that heartbeat rates should not exceed 110 beats/minute for long periods during the working day. During more intensive work periods, 130 b e a t s / m i n u t e should not be exceeded. In favourable temperature conditions, the acceptable workload (AWL) proposed by Saha et al. (1979) is 35% of the maximum VO 2 for every individual. It corresponds to the proportions selected by Lehmann (1953), Soula et al. (1961), Brouha (1967), Bonjer (1963) at the time when this same type of problem arose in Europe and North America. From work by Nag et al. (1980) it appears that for healthy young Indian farm workers, a 110 b e a t / m i n u t e rate corresponds to 25% of their maximum VO 2. These proportions are close to the recommendations made in industrialized countries. However, since the maximum VO 2 is higher in industrialized countries, the recommended absolute work VO 2 values are higher than in India. As such, there is internal agreement concerning the adaptation of a scale of relative laboriousness

expressed as a percentage of the maximum VO 2 of each person, each group or each sub-group. Soula et al. (1961), confirmed by Monod (1981), consider that "light work uses as least 25% of aerobic power. This category covers most professional tasks; intense work corresponds to the use of 25-50% of aerobic power. This is the category which includes heavy work. Submaximal work corresponds to 50-75% of the aerobic power. Such intense tasks are frequent in heavy industry and mines and in the course of some sports. Maximum work uses 75-100% of aerobic power. Such high level professional tasks are exceptional, yet have been noted in foundries. Exhausting work is done with power in excess of the maximum level of aerobic power. Anaerobic power is largely used as indicated by the extent of the oxygen debt. Exhaustion generally follows within a few minutes." Apart from a few variations in vocabulary, these expressions relative to laboriousness are generally accepted. Yet scientific literature also states absolute task evaluation scales like those of Brouha (1967) which tacitly relate to a worker with a maximum VO 2 of 3 1/min. Such aerobic power is quite exceptional in industrial developing countries, especially in South and Southeast Asia; it is even quite rare in industrialized countries where heavy workers often originate from IDCs or the poorest regions of industrialized countries. On the other hand, aerobic power of 3 1/min is very often found in physical education students in all countries. As such, it is advisable to avoid expressing the laboriousness of a task in absolute terms and better to express it relative to the worker's capacity. Figure 6 shows that the requirements of the same task (e.g. expressed according to Brouha's classification) may vary considerably according to the capacities of the human group which performs it. Thus, a task requiring oxygen uptake of 1 1/minute is regarded as the upper limit of light work by Brouha and by Soula and Monod for Swedish physical education students. Using Soula's and Monod's classification, it is noted that this same work is intense for Norwegian workers, at the limit between intense and submaximal for Indian and Ethiopian farmers at at the limit of maximal and exhausting work for Indian women and Indian paraplegics.

134 MALESWEDISH

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Such considerations may also be expressed in terms of maximum work time or frequency and duration of the necessary breaks. The importance of training is shown in Fig. 7 taken from Astrand and Rodahl (1970). Thus, a task requiring 25% of the maximum VO 2 may last for several hours in untrained subjects, whereas in trained subjects prolonged work may reach 50% m a x i m u m VO 2. It is known that workers suffering from denutrition

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cannot reach a satisfactory training level (Wyndham et al., 1962).

5. Conclusions There are substantial differences among worker populations throughout the world. These differences are partly explained by ethnic factors, sex, age and health condition. However, the major source of variety remains the way of life and food resources. Abundant nutrition rich in animal protein combined with physical exercise will produce a 20% increase in the physical capacity of a young, previously underfed adult within a very short time. Thereafter, the tasks this worker has to perform will be at a lower level on his scale of laboriousness. He is able to work harder, longer and with less risk for his health. The rapid increase in physical capacity of a young, healthy adult is an essential element of an industrial policy and, more generally, a development policy. In m a n y regions of the world, undernutrition and heat leave workers with very little physical capacity for productive

135 work and this leads to the continuation of poverty. A fact related to this situation, common to industrialized and industrially developing countries, is that people high socio-occupational classes whose job involves little physical work have greater or much greater physical strength than farmers or industrial workers of the same age and sex. This fact is essential if wrong predictions are to be avoided. As regards body measurements, major differences are noted, the origins of which are similar to those of the physical capacity differences. Ethnic variations show genetically. Other factors act very early; the influence of anthropometric features and the nutritional condition of the mother are decisive for the future characteristics of the child when he reaches adulthood. Anthropometric changes take place according to the socio-economic level of countries and human groups. Over the last 100 years, secular growth has reached 1 mm a year in countries which have been industrialized for some time. Similar growth of around 100 mm has been recorded in Japan in just one third of this time, related to a very fast change in living and nutritional standards. Similar differences (100 mm) may be noted between different socio-occupational spheres in industrially developing countries and, to a lesser extent, in industrialized countries. Two types of conclusion may be drawn from these findings. On the one hand, the anthropometric features of people are not unchangeable. The part played by genetic factors is not isolated. Socio-economic changes may have a considerable effect on the height and other physical measurements of the world's populations. Another more ergonomic and immediate consequence is that expensive industrial products like cars could be mass-produced according to a design based on the characteristics of purchasers throughout the world. In fact rich populations in poor countries and the general population in rich countries have similar dimensional characteristics, especially when the distribution of potential drivers is taken into account in terms of age and sex. On the other hand, the machines and equipment for industrial work, and especially those for farming have to be altered to a great extent or even produced locally to suit users. Such considerations are particularly true when considering the most

varied worker populations: those of long-industrialized countries in Northern Europe and America and those of South and Southeast Asia and Latin America. On the contrary, workers in countries around the Mediterranean and, to a lesser extent, Black African countries, have similar dimensional features favouring exchanges. Significant links thus appear between people's physical characteristics and their socio-economic development. The dynamics of these evolutions is of considerable interest for the ergonomist anxious to improve technology transfers. From an anthropotechnological viewpoint, the ergonomist will therefore prove useful to both exporters and importers of work facilities. He will be able to help each national economy develop the work facilities it needs and does not find on the international market due to excessive standardization based on the features of industrialized countries.

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