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Marķa Patrocinio E. de Guzman
Food and Nutrition Research Institute, National Science Development Board, Manila, Philippines
Laguna Rice Farmers
This study is the first of a series of energy expenditure studies made on the occupational activities of Filipinos. A total of 33 farmers served as subjects for a seven-day assessment of the total daily energy expenditure and time spent in farming and basic activities as well as of dietary intake. Their characteristics are shown in table 1. Only measurement of the calorie cost of the various farming activities was done on the remaining 24 subjects which comprised 15 males and 9 females.
Indirect calorimetry, using the Max Planck respirometer and the Beckman E-2 gas analyser, was employed to measure the metabolic cost of the different activities.
The mean daily calorie intake and expenditure of the nine male farmers and the mean time spent each day in the various activities. and their calorie equivalents, are presented (table 2). Metabolic costs of the various farming activities of the 24 subjects are also given (table 3).
Measurements of the total energy expenditure and dietary intake for seven days were made on nine male rice farmers in barrio (village) Cabanbanan, Santa Cruz, Laguna. Energy costs of both agricultural and non-farming activities performed by the farmers are given (table 4). Measurements of the metabolic cost of various farming activities were made on 24 additional farmers (15 males and nine females). Values obtained from harrowing and ploughing using the carabao indicated a lower energy cost per unit of time compared to the use of the hand tractor for the same activities. The speed of the tractor, however, would result in much lower total energy costs if the time involved in the performance of the task were considered. There was no significant difference obtained between the energy cost of the same farming activities done by the male and female subjects in this study.
TABLE 1. Physical Characteristics of Farmer Groups Studied
|No.||Sex||Age (yrs)||Height (cm)||Weight (kg)||Group|
|9||Male||28 ± 17a||159 ± 6||515 ± 70||Initial|
|15||Male||27 ± 9||161 ± 5||510 ± 6 1||Additional|
|9||Female||24 ± 12||153 ± 6||466 ± 7 2||Additional|
a. Mean ± SD
TABLE 2 Mean Energy Expenditure of Farmers (Sitting Standing, and Walking)
|Sitting||1.62 ± 0.21||0.031|
|Standing||1.66 ± 0.22||0.032|
|Walking (own pace)||3.72 ± 0.58||0.072|
TABLE 3. Mean Energy Cost of Various Farming Activities
|Activity||Male (kcal/kg/min) (n = 24)||Female (kcal/kg/min) (n = 9)|
|Riding carabao||0.044 17)|
|Cutting weeds with bolo||0.097 (1)|
|Chopping with axe||0.139 (4)|
|Harvesting||0.109 (5)||0.100 (6)|
|Threshing (hands)||0.123 (5)||0.113 (1)|
|Threshing (feet)||0.130 (4)|
|Ploughing (carabao)||0.137 (8)|
|Ploughing (hand tractor)||0.154 (4)|
|Harrowing (carabao)||0.134 (7)|
|Harrowing (hand tractor)||0.167 (2)|
|Planting||0.099 (4)||0.088 (5)|
|Sorting rice stalks||0.060 (1)|
|Watering plants||0.088 (1)|
TABLE 4. Mean Daily Energy (E) Intake (I) and Expenditure Per Day of Nine Male Farmers
|Subject||Intake (kcal)||Expenditure (kcal)||Difference (E:I)|
|Mean ± SD||2,471 + 795||3,307 + 783||836 + 830|
Nine of the farmers under study consumed a considerably lower caloric intake compared with their expenditure. A mean energy expenditure of 3,307 kcal and a mean intake of 2,471 kcal were obtained for the farmers It has been observed that active work on the farm covers only an average of five months, while the rest of the year the farmers' work is sedentary in nature. Considering this annual pattern of activity of a typical Filipino farmer, it is most likely that farmers would be able to subsist on a low-calorie intake during their peak months of activity and make up for the lack during the less active part of the year. Furthermore, it is possible that the generally low productivity of Filipino farmers may be attributed to the large discrepancy between their food intake and energy expenditure. However, the effect of this discrepancy on the working efficiency of the farmers studied was not determined. This offers another avenue for future research on the subject.
Shoemakers and Housewives
The next group studied included 10 shoemakers and 10 housewives in the municipality of Marikina, Rizal Province, where the shoemaking industry is concentrated. The same methodology was used as in the study on farmers, wherein one week's data on the energy expenditure of each subject were measured by indirect calorimetry while they performed their usual daily activities. Time spent and the mean daily food intake of the subjects were likewise measured during the same period. Their characteristics are given in table 5.
In this study, we attempted to measure the total energy expenditure and dietary intake for seven days of 10 shoemakers and 10 housewives. Energy costs of both basic and occupational activities are given (tables 6-8). Measurements of the metabolic cost of various shoemaking activities were also made on eight additional shoemakers. Values obtained for the metabolic cost of basic activities (sitting. standing, walking) of the housewives were found to be lower than those obtained for the shoemakers. Of the activities tested, a higher mean value (0.063 kcal/kg/min) was obtained in trimming the sole and heel of the shoe as compared with other shoemaking activities.
TABLE 5. Physical Characteristics of the Groups Studied
|Shoemakers||10||Male||26 ± 7a||167 ± 4||56.3 + 4.1|
|Housewives||10||Female||34 + 8||155 .+ 6||54 0 ± 1 1 4|
|Additional shoemakers||8||Male||26 + 7||165 ± 6||57 1 + 5.3|
TABLE 6. Mean Energy Expenditure of Shoemakers and Housewives (Sitting, Standing and Walking)
|Group and Basic Activity||Kcal/min||Kcal/kg/min|
|Shoemakers (n = 18)|
|- Sitting||1.57 ± 0.23||0.028|
|- Standing||1.65 ± 0 15||0.029|
|- Walking||3.98 ± 0.33||0 071|
|Housewives (n = 10)|
|- Sitting||1.20 ± 0.25||0 023|
|- Standing||1.30 ± 0.25||0.024|
|- Walking||2.39 ± 042||0.046|
TABLE 7. Mean Energy Cost of Various Activities of Shoemakers and Housewives
|Group and Activity||Kcal/kg/min|
|Shoemakers (n = 18)|
|- Moulding top portion of shoes (Naglalapat)||0.054 (18)|
|- Attaching sole (Nagsusuelas)||0 054 (18)|
|- Trimming sole and heel (Nagdidispatsa)||0 063 (18)|
|Housewives (n = 10)|
|- Uppermaking (preparation of top portion of shoes)||0 037 (6)|
|- Bathing child (standing)||0058 (2)|
|- Carrying child (standing)||0 032 (6)|
|- Washing clothes||0044 (3)|
|- Cooking||0.036 (10)|
TABLE 8. Mean Daily Energy Intake (1) and Expenditure (E) Per Day of Ten Shoemakers and Ten Housewives
Group and Subjects
|Mean + SD||1,594 ± 701||2,712 ± 510|
|Mean ± SD||1.785 ± 553||2,040 ± 328|
The increase, however, gave only an average expenditure of 18 calories per hour more than the value obtained when the subject was sitting quietly in a chair. For the housewives, bathing a child and washing clothes resulted in highest metabolic cost. They entailed an increase in energy expenditure of 95 and 75 calories per hour, respectively, over the expenditure when the subject sat quietly. Variations in performing the varied domestic activities are so great that the energy expenditure necessary for performing a given household task would depend on existing conveniences. There was no significant difference obtained between the mean energy expenditure and the mean intake obtained for either shoemakers or housewives studied.
An evaluation of the diets of the shoemakers showed that the percentage of protein and calorie intakes was found to be comparable with the recommended daily allowance for the moderately active Filipino reference man 25 years old whose weight approximates the weight of the shoemakers studied. No statistical significance was found between the mean protein intake of housewives studied and the recommended daily allowance in terms of the standard ratio of gram protein to body weight.
From the results of this study. we could easily classify the shoemakers as belonging to the moderately active group. and the housewives to the sedentary group.
Department of Nutrition and Food Sciences, Zhong Shan Medical College. Guangzhou (Canton), China
Understanding energy expenditure and the caloric requirements of different kinds of labourers is a basic problem of the nutritional sciences (1). There has been worldwide discussion of human protein and energy requirements since the 1973 Joint FAO/WHO Ad Hoc Expert Committee published its report (2), and it is generally recognized that the protein requirement is very closely correlated with energy expenditure.
In a subtropical area, we estimated the energy expenditures of three categories of labourers: (a) miners doing five varieties of work; (b) shipbuilders doing six kinds of work; and (c) peasant women, whose work mainly involves growing vegetables in the Guong Dong Province of southern China.
Subjects and Methods
Ninety-two labourers, 22 to 36 years old, participated in these studies. Their mean ± SD weight was 55.4 ± 4.8 kg and height 159.3 ± 10.6 cm. Subjects were certified as healthy on the basis of medical examination. All of them were informed about the purpose, meaning, and procedures of this study. All of them were volunteers. All miners were male, as were most of the shipbuilders, except for a few females working on lathes, but all the peasants working in vegetable fields were female, as is the custom in this area.
The energy expenditure was estimated by an indirect method, i.e. by oxygen consumption in the fields where the subjects worked. Mouthpieces and Douglas bags were used to collect expired air, and its oxygen and carbon dioxide content, as well as the composition of fresh air the subjects breathed, all analysed by Haldane's method (3-5). The apparatus for collecting expired air was set up while the subjects were performing their usual work. About 20 minutes or more were required by each subject to adapt well enough to the apparatus so that he or she could work normally. The air expired by each subject during a specific occupational activity was collected for a specified time. The volume of air was determined by airometer, and samples were taken for analysis.
Subsequently, the physical activities, in terms of kind and duration, of each subject during 24 hours (1,440 minutes) were directly observed using a printed chart that listed typical activities.
By interviewing each subject, we verified that the schedule of activities observed by us, including housework and social activities. was basically typical for that subject. The averages of daily energy expenditure for specific activities of different categories of workers were calculated, and typical schedules of daily activities for specific groups were established.
The total 24-hour energy expenditure was obtained as the sum of basal metabolism, a small increment due to specific dynamic actions of food, and the energy expended in various types of physical activity. The energy cost of occupational work was measured. We also measured some of the off-the-job activities, such as walking on steep mountain slopes in the case of the miners. The energy expenditures in other activities, such as sleeping, were estimated from the data reported in the literature (5).
All the subjects observed were in medium-sized mines or factories where physical labour still constituted an important part of their work; that is, for the most part, workers used semi-manual machines, and the peasants basically performed manual labour in the field. The specifications of working activities were as follows:
1. The drillers, using pneumatic drills, bored blast-holes in the rocks or ores. All drills had to be held by hand because of the vibration of the machine. The driller chose the time to shift drilling position and move the drill. He had an assistant for heavy tasks when a medium-sized drill was required.
2. The ore porters worked in association with two miners in transporting the ore from the pit to the storage shed outside the mine. The ore, shovelled by hand into the ore car, weighed about 500 kg, and the total weight of the car was about 600 kg.
3. Hammer operators used a hammer weighing about 5 lb to pound the drill rod to make blast-holes in the rock when pneumatic drills could not be used, especially in vertical mines and inclined mines. Two workers held the drill rod and the hammer hit the rod about 15 times a minute. Sometimes the hammerer smoothed the newly developed pit by knocking off the irregular parts of the rock with the hammer after blasting.
4. Ore-dressing workers transferred the ores from storage sheds to the dresser and controlled the water flow for ore processing. They used an iron picker in the ores in order to separate the mineral ores with a sieve. They worked standing, but most often in a bent posture.
5. The prop-setting workers made supports for the roof of the pits, especially after a new drilling had been made, mostly using timber posts that they adapted to the location. They carried all the wooden material to the pit on their shoulders and used a hand-saw and bush knife for processing the timbers.
1. The cutters used an oxyhydrogen (or acetylene oxygen) flame to cut steel plates and sheets of varied thickness to different sizes or shapes. They handled the plates manually when they were small, but used cranes for the bigger ones.
2. The hammerers used a hand-held hammer weighing 3 to 5 kg to give a specified shape or curve to steel sheets. usually 1 to 2 cm thick, and sometimes used preliminary flame heat treatment of the sheet before hammering.
3. The planers used a portable pneumatic planer weighing 6 to 7 kg to cut off the extra or irregular parts, or to smooth parts of the ship surface. according to design. They worked up and down the ship body in different postures-i.e. kneeing, bending, sitting, and standing, as required.
4. Electrical welders used regular welding equipment, and climbed up and down the ship body.
5. Engine lathe operators used mostly automatic lathes of different kinds for milling, shaping, planing, and drilling different metal parts of the ship, working in a standing position, sometimes having to remove tools and processing units by hand.
6. The carpenters used mostly power-driven tools to process different wooden ship materials.
There were 11 kinds of tasks carried out by peasants cultivating vegetables. These workers also participated in some of the operations involved in growing rice.
1. Transporting materials on their shoulders. they carried loads that varied from about 8 to 40 kg, mostly using a balance pole with a barrel attached to each end.
2. Watering: irrigating containers were filled with water (total weight about 30 kg), Ioaded onto the women's shoulders by a pole, for watering vegetables by walking back and forth between rows.
3. Hoeing: workers used a hoe weighing 2 to 3 kg to turn over and loosen the soil and to rake the ground for planting. In hoeing, the hoe was lifted about 50-60 cm high about 10-16 times per minute.
4. Irrigating by water-wheel: the wheel of a wooden machine was rotated, using both hands, to move the water from a lower level to a higher one for irrigation. The wheel rotated about 20 to 30 times per minute.
5. Transporting materials by a two-wheel cart: two women pulled or pushed a cart weighing about 50 to 100 kg, at a speed of about 5 kilometres per hour.
6. Fertilizing: filled fertilizer-tanks weighed about 16 kg. The fertilizer (in liquid or powder form) was spread around the roots of the plants by walking around the edge of a plot. Sometimes they sprayed plants with pesticides, using similar equipment but lighter in weight (about 5 to 10 kg}.
7. Sowing: after the ground had been smoothed and the loosened soil watered, holes were made by a small rod or trowel, and the seeds were put in and covered with soil.
8. Harvesting: the vegetables were cut by knife or whole plants were pulled out by hand, washed, and bundled.
9. Seedling cultivation: some vegetables required transplantation of seedlings. The work was similar to sowing.
10. Gathering of rice seedlings. paddy rice seedlings were carefully collected from a special field, then bundled, and prepared for transplantation.
11. Transplanting rice seedlings: the seedlings were transplanted by women standing in muddy fields and bending while working.
Estimated Energy Expenditure per Minute of Work
Energy expenditure at work depends on the work load. The ore porters in the mines expended the greatest amount of energy, about 7.98 kcal/min on average. The drillers in the mine had a much lower energy expenditure, about 2.43 kcal/min, and the remaining miners expended about 3.5 to 5.5 kcal/min. Additional energy was expended by the miners in climbing up the ladders of a shaft or walking up an inclined mine during working hours (table 1).
TABLE 1. The Energy Expenditure of Miners
Kind of Work
Number of Cases
|Holding drill rod||2||2.43||0.0485|
|Full car||5||7 98||2.34||0.1407||0.0370|
The energy expenditure of the shipbuilders was generally lower than that of the miners because of greater use of machinery. Hammerers who did hard physical work had the highest energy expenditure among shipbuilders, about 5.4 kcal/min (table 2).
The peasant women growing vegetables were engaged in various kinds of physical work, and their energy expenditure varied from 1.29 to 4.12 kcal/min. The average body weight of these women was 41.2 kg. Therefore, the energy expenditure required for some of their work was quite high (table 3).
Estimated Energy Expenditure per 24 Hours
The average energy expenditure per 24 hours depends upon the intensity of occupational work as well as on activities after work. The miners did less household work than shipbuilding workers, but in going from home to the mines they had to walk up and down steep mountain slopes. This took about 1 to 1.5 hours a day. Both male and female shipbuilders did household work (tables 4 and 5). For female peasants. the energy expenditure varied from season to season; it was highest during summer, when they had to work harder and for longer hours. The daily energy expenditure varied from about 2,050 kcal during the off-season to 3.210 kcal during the busiest time. The intensity of their work was influenced by the weight of the load they carried. We observed that they engaged in this type of activity about 23 per cent of the working day.
TABLE 2. The Energy Expenditure of Shipbuilding Workers
Number of Cases
|Engine lathe operating||9||1.66||0.450||0.0323||0.003|
|Electric welding workers||12||1.64||0.200||0.0293||0.021|
|Cutting with gas torch||4||1.32||0.090||00275||0.004|
|Climbing up and|
|down the ship||3||3.54||0.770||0.6664||0.009|
TABLE 3 Energy Expenditure of Vegetable Growers
Number of Cases
|Rice seedling gathering||20||1.29||0.36||0.0571||0.010|
|Shoulder load transporting|
|Rice seedling transplantation||2.25||0.69||0.0571||0.010|
|Rest (standing)||0 0155||0.003|
TABLE 4. 24-Hour Total Energy Expenditures of Miners
|Kind of Work||Kcal Expended in Working Hours||Kcal Expended in Off-work Hours||Kcal/24 hrs|
TABLE 5. The 24-Hour Total Energy Expenditure of Shipbuilding Workers (Calculated as 55 kg Body Weight)
|Kind of Work||Kcal Expended in Working Hours||Kcal Expended in Off-work Hours||Total|
It is less complicated to measure energy expenditure at work than to estimate total energy requirements because of individual differences in efficiency of utilization of energy as well as factors that cause variations in energy metabolism. The individual variation in energy expended in a given activity is substantial. Harries (6) observed 11 kinds of work and found that the coefficient of variation ranged from 6.7 to 21.3. We found that the variation in the same activities was less than indicated by Harries' figures, perhaps because the patterns of motion were simpler. As for energy expenditure, we found that the miners walking from home to the pits up steep mountain slopes in stooping postures expended more energy (4.77 kcal/min) than during working hours when using machines, as observed by Thomas (7) and Sweetland (8). Travelling from home to the mines required 1 to 1.5 hours a day. Seasonal variation in the activities of peasants were large, as were the individual differences in household chores and work in home gardens. Therefore, we calculated an average of activities for the same group of labourers. Edholm et al. (9) found it more accurate to observe a group instead of an individual within a given period of time.
Our values for energy expenditure during heavy physical work are quite close to Liu's (10) observations in the steel industry, and the energy expenditure of peasant women is similar to those reported by Yu (11) found in the Fu-kin survey (12). However, much research remains to be done to establish the energy requirements for different kinds of workers and for different age groups (13).
I wish to thank Dr. S.G. Wong for supporting this estimation and Dr. C. Cheng for his participation in the estimation of the experiment on peasants, and to thank Dr. J. Brozek for his helpful advice.
1. Hsien Wu ''Calorie Requirement." Texas Report on Biology and Medicine, 9:854 (1951).
2. Joint FAD/WHO Ad Hoc Expert Committee, Energy and Protein Requirements (WHO Tech. Rep. Ser.. 522, Geneva, 1973).
3. C.P. Consoiazio, Metabolic Methods (Hill Co., 1951), p 312
4. E.F. DuBois, Basal Metabolism in Health and Disease, (Lea and Febiger, 1936), p. 93.
5. J.V.G.A. Durnin. Habitual Physical Activity and Health, (WHO Regional Publications. European Ser. No 6. 1978), p. 171.
6. J.M. Harries. "Individual Variation in Energy Expenditure and Intake.'' Proc. Nutr. Soc.. 21:157 (1962).
7. B Thomas and C.G Warner. "The Energy Expended While Walking in Stooping Postures. Brit. J. Industr Med., 12:290 (1955).
8. K.S. Sweetland. "The Energy Expenditure of Coalminers at Work," Brit. J. Industr Med., 19:264 (1962).
9. O.G. Edholm, J G. Fletcher, E.M Widdowson, and R.A. McCance, ''The Energy Expenditure of Food Intake of Individual Men," Brit. J Nutr, 9:286 (19551.
10. K Y Liu, "The Energy Expenditure of Some Kinds of Work in Steel Factories," Acta Nutrimenta Sinica, 2:221 (1957) (in Chinese)
11. S.S. Yu, ''The Energy Expenditure of Peasants," J. People's Sanitation, 2:148 (1960) (in Chinese).
12. Institute of Health of Fu-kin. "Primary Survey on the Energy Expenditure of Peasants," Chinese J. Hyg., 9:348 (1964).
13. J.V.G.A. Durnin, O.G. Edholm, D.S. Miller, and J.C. Waterlow, ''How Much Food does Man Require?," Nature, 242:418 (1973)
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