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Ergonomics in the home
Applied Ergonomics 1970, 1.4,223-227
Ergonomics in the home Joan S. Ward Department of Ergonomicsand Cybernetics,University of Technology, Loughborough.
The house and housework are as appropriate an area of ergonomics study as is the factory floor, but much less concerted effort has been put into studying the problems of the housewife. It is suggested that investigations to determine the amount of physiological effort (particularly that of muscle activity by techniques such as electromyography), the optimum dimensional accord between equipment and user, and the provision of satisfactory environmental conditions, are needed in order to ensure that the housewife performs her tasks with the minimum of unnecessary effort and maximum satisfaction.
Introduction
Job description of housework
The principal aim of ergonomics is to 'promote learning and advance education in the subject of . . . . the relation between man and his occupation, equipment and environment, and particularly the application of anatomical, physiological and psychological knowledge to the problems arising therefrom.'
It is not easy to define housework as a task, but perhaps the following quotation from Steidl and Bratton's 'Work in the Home' (1968) is appropriate:-
The development of ergonomics from its war-time concern with vital industrial production has tended to keep its emphasis on the problems of man (and woman) on the factory floor. Without in any way suggesting that this is not a necessary sphere of study, it is here proposed that the place in which men, and particularly women, spend an even greater proportion of their lives - the home - is no less worthy of ergonomic investigation. It might be considered that the problems of the housewife are not so acute that they require study - no industrial disputes, strikes (at least official large-scale ones), public protests or organised complaints, arise - the national balance of payments is not affected and there does not appear to be any call for new training schemes or, indeed, for any education, at least from housewives themselves. It may be further argued that technological advances have already taken the hard work out of housework. The housewife today has merely to press buttons and manoeuvre yards of flex to achieve what her grandmother did with manual labour. I would like to suggest however, that the case for considering the housewife and her work to be a serious subject for ergonomic study is as follows. In the first place, as already stated, ergonomics is concerned with man (and woman) in their working environment, so the housewife qualifies as a subject for study. In the second place, in 'advanced' or 'developed' countries women are an increasing force in the paid labour market and their dual role as home-maker and breadwinner needs easing if they are to do both jobs properly. Thirdly, in the less advanced or developed countries, where many technological advances in the domestic sphere are yet to come, there is an excellent opportunity to get the ergonomics right before the mass introduction of mechanical aids to housework.
Job title: housewife By Harold W. Jacobson, Job Analyst National Company Inc., Malden, Mass. Grade: High
Description: • Functions in several capacities and offices performing a wide variety of duties semi-routine in nature but where the exercise of independent judgement is required in the application of practices and policies to situations not previously covered. •
Effects the purchase of a wide variety of organic materials for processing, giving special consideration to costs, market conditions, and state of material. Plan, layout, and schedule processing operations, maintaining strict control of flow and inventory to meet schedules. Conduct necessary chemical operations, using various heat treatments as required to transform basic organic materials into completed form for distribution to consumer.
• Maintains budgeting, cost control and cost accounting systems, operating within a limited financial framework. Strike semi-monthly trial balances to determine relationship between accounts-payable and accountsreceivable and, as required, perform necessary magic to bring accounts into balance. •
Operates and maintains a variety of manually and electrically powered equipment for heating, cooling, stitching, suctioning, cleansing, etc.
• Performs other miscellaneous duties of a routine nature not specifically mentioned, but where such duties are a normal outgrowth of the job.
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223
Education (This factor appraises the minimum amount of theoretical education required, however attained). Broad general knowledge of several specialised fields such as chemistry, mechanical and electrical engineering, marketing, accounting and fundamentals of human relations. Complexity of duties (This factor appraises the need for initiative, ingenuity, and independent judgement). Perform a wide variety of semi-routine duties directed toward the attainment of a general objective: the physiological and psychic welfare of a small social group. Performance requires the use of judgement in devising new methods and modifying or adapting standard practice to meet new conditions. Responsibility (This factor appraises the responsibility for equipment, material, process, and health, safety, and work of others).
according to the availability of appliances, in addition, of course, to 'culturally' determined patterns of living, house design and eating habits. The authors of the most recent critical review of published studies (Steidl and Bratton, 1968) make it clear that further studies in many areas are needed.
Effort A considerable body of information is available on the amount of effort (usually in terms of calories per unit of time) expanded in a variety of household tasks. Table 1 (collated from a number of sources) presents in general terms energy costs for selected activities.
Table 1 Energy (which is measured in joules/minute, with calories/minute given in brackets) costs for selected activities.
Complete responsibility in terms of costs, methods, and personnel for equipment, material, process etc. Supervise and direct one inept male in the performance of a limited number of routine duties such as: rub, scrub, sweep, brush, mop, polish, etc.
Energy Joules/ minute
(Calories/ minute)
Activity
4"18
(1)
Resting
Effort (This factor appraises the mental and/or visual demand required).
4"18-8"37
(1-2)
Seated - sewing, knitting, paring potatoes. Standing - ironing, dishwashing, stooping to 559 mm (22") above floor.
8"37--12"55
(2--3)
Walking, sweeping, hanging clothes from basket on floor or table.
12"55-16"74
(3--4)
Washing floor, waxing floor, bedmaking, changing sheets, cleaning carpeted stairs.
Over 16"74
(Over 4)
Picking up items from floor, climbing up and down stairs, weeding garden.
High degree of concentration where the volume and nature of work require unusual co-ordination of hand and eye.
Working conditions (This factor appraises the surroundings or physical conditions under which the job must be performed. It includes health and accident hazards). Somewhat disagreeable working conditions due to exposure to dust, dirt, heat, etc. Exposure to accidents where results will probably be minor in nature: cuts, bruises, burns, etc, which, although painful, are not incapacitating in nature. Health hazards negligible. Fatigue factor high." Ergonomics and housework
From the ergonomics point of view, we would primarily be interested in those aspects of the task that are listed, lightheartedly but accurately, as 'operate', 'perform', 'effort' and 'working conditions', although not necessarily in that order. It would, in fact, be appropriate to look at them both from the point of view of how much is already known, and what gaps there are in current knowledge. The greatest number of published studies on the housewife and work in the home have come from the United States. It might be thought that such transatlantic findings would be conveniently extrapolated to the British scene. Direct extrapolation is not always the solution, however, for the principal reason that 'home-making' methods, attitudes and 'standard' equipment are not necessarily the same in both countries. In 1965, for instance, it was calculated that 81.4% of American homes had washing machines and 13-5% dishwashers (Steidl and Bratton, 1968). The comparable figures for Britain in that year were 56% had washing machines and less than 1% had dishwashers (Electricity Council, 1970). Methods of cleaning, laundering and food preparation will thus differ 224
Applied Ergonomics September 1970
The amount of physical effort required for the majority of household tasks, as Table 1 shows, is not great, especially as the times spent on tasks are usually both of short duration and under the voluntary control of the housewife. So it is not necessarily the total daily amount of energy expended that is of importance in the home. It is more often the physiological strain placed on particular muscles by the maintenance of static posture or the prolonged use of certain limbs or body segments. Calorimetry - the direct or indirect determination of the amount of physical energy expended during any activity - is not the most appropriate method by which to determine the effort expended by only one or two or small groups of muscles. The technique of measuring muscle activity is known as electromyography. To quote Steidl and Bratton (1968): 'Electromyography is the measurement of electric phenomena occurring in muscle during contraction and can be used to determine if certain muscles are acting or not acting in different positions or
movements of the b o d y . . . The equipment is similar to that used in making electrocardiograms...' For detailed information on this technique the interested reader is referred to Basmajian (1962). For present purposes, it can be stated that, although electromyography has been applied to some problems of the seated posture (Floyd and Silver 1955: Floyd and Ward, 1969), it has only very recently been employed to ascertain the muscle activity involved in certain domestic tasks undertaken by women of differing stature at different working heights (Saville, 1969). It is hoped that an account of this latter work will appear in a subsequent issue of this journal. Clearly, however, this method could be employed to great advantage in determining the muscular cost of many, if not most, household tasks and thence to the more appropriate design of equipment and appliances involving considerable muscular effort.
Performance In the past the most widely used method of determining the appropriate way to perform household tasks has been either to ask the subject how he or she prefers to do it or to observe how the task is done - the rationale being that the individual is the best judge of his or her capacity and requirements. Relevant examples of 'preferred' working situations a r e : • 'Relation of posture to fatigue in ironing'. (Knowles, 1945) • 'Preferred depth and height for kitchen sinks'. Council for Scientific Management in the Home, 1961. However, unless the conditions under which a subject is to state a preference are carefully controlled, the'preference' may be a poor guide to the real requirements. Human beings are immensely adaptable and can accustom themselves to a wide variety of situations. This is, of course, admirable in the Darwinian sense, but it can also mean that what someone says he 'prefers' is often simply what he has become accustomed or habituated to, and it may be far from the optimum. Nevertheless, an individual can when his attention is drawn specifically to a selected aspect, or some selected aspects, of a situation or object, be shown to be highly reliable in his judgement of the subjective ease and comfort of that situation or object. The 'preference' method therefore, properly applied, is a most useful technique for evaluating the performance of a task. Some studies have related preferred working positions to physiological and/or anthropometric measurements; an example of such an investigation into ironing (see Fig 1) is given by Knowles (1945) and, more recently, Ward and Kirk (1970)have reported an investigation into the relationship between preferred working surface heights for various tasks both standing and seated and some anthropometric dimensions. An earlier publication (Floyd et al, 1965) dealt with the physiological, anatomical and psychological principles that should govern the design of household jugs. A number of publications dealing with the design aspects of domestic appliances have pointed to ergonomic faults in such designs. (Anon., 1961; Anon., 1962a, 1962b).
Operation In this country, and some others, an increasing emphasis is being placed on the desirability of more leisure, or
A Fig 1
B
The effect upon posture of ironing at different
heights:A - at a height suitable for the subject B - 76 mm (3 in) lower. (Adapted from Knowles, 1945).
additional time in which the housewife may undertake gainful employment. The development of equipment to take over, or facilitate, her tasks in the home will presumably continue. And it is in this area that ergonomics can play a vital part. No one will argue against the need to make equipment fit the user so that both can perform to maximum advantage. It is necessary to determine if the operation of equipment by the user, either in terms of overall expenditure of energy or of individual muscle/muscle group activity, is within her physiological compass. The answers are unlikely to be the same for a widow of 60 managing her own bungalow and the young housewife who still plays hockey for the Old Girls. Even more fundamentally, equipment of every kind, whether stationary or movable, should at least be in accord dimensionally with the user. Too often however, the solution to this dimensional problem has been to make it suitable for the average user. In practice this means that all users above the 'average' and, often more critically, all below the 'average' are incorrectly or, at best, less well catered for (see Fig 2). It is in addition forgotten (or probably not known) that an individual who is, say, 'average' as regards stature, is not necessarily 'average' in other bodily dimensions. To provide, for example, a fixed wall cupboard or storage unit to the top shelf of which persons of 'average' height can reach means, first of all, that it suits no one shorter than this 'average' because they
Applied Ergonomics September 1970
225
will not be able to reach up to it; and secondly, because the determinant is more accurately arm reach plus stature, not stature only, even persons of 'average' stature but of less than 'average' arm reach will also not be properly suited. It is the range of sizes of persons or, rather the range of the relevant anatomical diriaensions in the appropriate group of persons, that is of primary concern in determining the correct dimensions and siting of equipment. To return to the example of the fixed wall cupboard: the solution would be to consider the range of arm reach lengths, plus stature, of the population to be catered for. If the top shelf of this cupboard is to be within reach of, say, all adult British women, then the upper limit should be based on the shortest arm reach of the shortest woman. For some solutions to dimensional problems, dearly, only one end of the appropriate range of human dimensions needs to be taken into account. The example of the wall cupboard shelf required the main consideration to be placed on the lower end of the arm reach and stature range. Clearance through apertures, the lengths of beds, widths calculated for multiple seating are examples where the stature or maximum widths of the tallest and/or largest persons only are required. Difficulties arise when the requirements of both tall and short (or thin and fat, or old and young, or combinations of any or all of these) have to be met in one solution. As has been stated, the 'average' is seldom the right solution. The answer is flexibility or adjustability. Equipment should be
capable of adjustment to suit the range of sizes of people for whom it is intended and the range of the particular anatomical dimensions or physiological capacities relevant to the operation of the equipment. Adjustability may be incorporated in one piece of equipment (the typist's chair), or it may require two or three variations of the same object (the 5 sizes of chair and desk recommended for schools BS 3030:1959 is an example), or one item of equipment, designed to suit the smallest user, may be supplied with plinths of differing thicknesses to raise it to levels suitable for both 'average' and tall users. The ineffectiveness of solutions based on 'average' users is further emphasised by the fact that the physical dimensions of people are changing. At a recent meeting it was stated that " . . . . over the past century, Europeans have shown a startling and consistent increase in average mature height of the order of 0"6 cm per d e c a d e . . , thus in thirty years' time the population is likely to be about 2-0 cm taller on a v e r a g e . . . " (Broman Dahlberg and Lichtenstein, 1942, quoted by Davis and Beevis at a Conference organised by the Institute of Mechanical Engineers, September 1969). In planning for the future, therefore, this increase must be borne in mind, together with the fact (ibid) that, in about thirty years' time " . . . . the period of growth to about full adult stature will be 1 2 - 1 4 years instead of 1 5 - 1 6 years as at present and the new post-adolescent will be several centimetres taller than his counterpart in the past . . . . " Whether this continuing increase in size will be matched by a parallel increase in muscular and general physiological capacity is not necessarily automatic, but raises some intriguing problems for future design. Optimum operation of equipment, in addition to requiring dimensional accord with the user, needs also of course to be capable of easy and safe control.(see Fig 3). Examples of the types of questions that require to be satisfactorily answered to ensure such proper control a r e : 1. Do the controls on an appliance move in the accepted direction, or are they reversed from the usual procedure? 2. Are controls clearly marked? Can the on-off positions be distinguished clearly? 3. Are intermediate settings marked so that the control setting can be adjusted accurately? 4. Are controls easily accessible? 5. Will it be dangerous to reach them while the appliance is in use? 6. Are the controls arranged in logical order of use? The above is not a comprehensive questionnaire examples of the types of more exhaustive check lists necessary to ensure safe and easy control can be found in Morgan et al (1963) and Murrell (1965), and reference to this topic was made in the first issue of this journal (pages 26 to 28).
Working Conditions Fig 2 This illustration, from Erik Berglund's book 'Skap' (Svenska SI6djf6reningen, 1960) is an example of the inadequacy of offering a single solution to a design problem without taking into account the varying requirements of users.
226
AppliedErgonomics September 1970
Accepting that the home, and particularly certain areas of it such as the kitchen, is a work place in the industrial sense, then current recommendations for and knowledge of the thermal, visual and acoustic environment characteristics desirable for workplaces are relevant. FroIa the ergonomic point of view therefore, the Ergonomics for Industry publications Nos. 6 'Noise in Industry', and 8 'Thermal
comfort in Industry', published in this issue as chapters 8 and 9 of the handbook (Applied Ergonomics, 1.4, 210-222), could well be appropriate to the domestic working situation.
Conclusion
It is evident that a certain amount of ergonomics information already exists which could be used by architects, interior and industrial designers, and domestic equipment manufacturers, more than it is at present. However, it must also be emphasised that more attention should be given by research workers to ergonomics problems in the home; only too often still, when ergonomics advice is requested by architects or designers, it becomes clear that all the necessary knowledge is not yet available. This short paper does not set out to offer detailed lists of investigations that need to be undertaken in the domestic area. It must suffice to suggest that two basic approaches should be made to the problems of the home and housework:1. Surveys need to be undertaken to determine what are the desirable and satisfactory characteristics required by the housewife in domestic equipment, layout and the environment; and . Experimental studies are required into those problems which are known to exist and those which will come to light as a consequence of surveys in these areas.
References
Anon 1961 Design, No. 1 5 1 , 6 1 - 7 0 . Design analysis 22 - washing machines. Anon 1962a Design No. 160, 5 2 - 5 7 . Design analysis 24 - vacuum cleaner. Anon 1962b Design No. 163, 3 2 - 3 7 . Design analysis 25 dishwasher Basmajian, J. V. 1962 'Muscles alive: their functions revealed by electromyography'. 2nd edition. Baltimore: Williams and Wilkins. British Standards Institution 1959 'Pupils' classroom chairs and tables'; BS 3030: Part 3. Council for Scientific Management in the Home 1961 Preferred depth and height for kitchen sinks. (Unpublished report). Electricity Council 1970 Personal communication from the Electricity Council. 30 Millbank, London, SWl. Floyd, W. F., Harding, R., Kirk, N. S. and Ward, J. S. 1965 Ergonomics, 8.4, 455--465. Some ergonomic aspects of household jugs. Floyd, W. F. and Ward, J. S. 1969 Anthropometric and physiological considerations in school, office and factory seating. In 'Sitting Posture' 18-25;ed. E. Grandjean. London: Taylor & Francis.
Fig 3 The necessity for easy and safe control of appliances is emphasised by this illustration (from Design, 160, 1962), where the carrying strap on the vacuum cleaner slips off the shoulder; and the hand that should be free to control the appliance has to be employed solely to hold it. The posture thus adopted is awkward and likely, if maintained for long, to be fatiguing.
Knowles, E. E. 1945 Journal of Home Economics, 3 7 , 5 8 4 - 5 8 7 . Relation of posture to fatigue in ironing. Knowles, E. E. 1946 CorneU University Agricultural Station Bulletin, 833, 5-57. Some effects of the height of ironing surface on the worker. Morgan, C. T., Cooke, J. S., Chapanis, A. and Lund, M. W. (Eds.) 1963 'Human engineering guide to equipment design'. London: McGraw-Hill. Murrell, K. F. H. 1965 'Ergonomics - man in his working environment'. London: Chapman and Hall. SaviUe, B. F. 1969 Optimum domestic work heights - a postural analysis. Ph. D. Thesis to University of Technology, Loughborough. Steidl, R. E., and Bratton, E. C. 1968 'Work in the home'. London: Wiley and Sons. Ward, J. S., and Kirk, N. S. 1970 Ergonomics (in press). The relation between some anthropometric dimensions and preferred working surface heights in the kitchen.
Applied Ergonomics September 1970
227
Ergonomics in the home Joan S. Ward Department of Ergonomicsand Cybernetics,University of Technology, Loughborough.
The house and housework are as appropriate an area of ergonomics study as is the factory floor, but much less concerted effort has been put into studying the problems of the housewife. It is suggested that investigations to determine the amount of physiological effort (particularly that of muscle activity by techniques such as electromyography), the optimum dimensional accord between equipment and user, and the provision of satisfactory environmental conditions, are needed in order to ensure that the housewife performs her tasks with the minimum of unnecessary effort and maximum satisfaction.
Introduction
Job description of housework
The principal aim of ergonomics is to 'promote learning and advance education in the subject of . . . . the relation between man and his occupation, equipment and environment, and particularly the application of anatomical, physiological and psychological knowledge to the problems arising therefrom.'
It is not easy to define housework as a task, but perhaps the following quotation from Steidl and Bratton's 'Work in the Home' (1968) is appropriate:-
The development of ergonomics from its war-time concern with vital industrial production has tended to keep its emphasis on the problems of man (and woman) on the factory floor. Without in any way suggesting that this is not a necessary sphere of study, it is here proposed that the place in which men, and particularly women, spend an even greater proportion of their lives - the home - is no less worthy of ergonomic investigation. It might be considered that the problems of the housewife are not so acute that they require study - no industrial disputes, strikes (at least official large-scale ones), public protests or organised complaints, arise - the national balance of payments is not affected and there does not appear to be any call for new training schemes or, indeed, for any education, at least from housewives themselves. It may be further argued that technological advances have already taken the hard work out of housework. The housewife today has merely to press buttons and manoeuvre yards of flex to achieve what her grandmother did with manual labour. I would like to suggest however, that the case for considering the housewife and her work to be a serious subject for ergonomic study is as follows. In the first place, as already stated, ergonomics is concerned with man (and woman) in their working environment, so the housewife qualifies as a subject for study. In the second place, in 'advanced' or 'developed' countries women are an increasing force in the paid labour market and their dual role as home-maker and breadwinner needs easing if they are to do both jobs properly. Thirdly, in the less advanced or developed countries, where many technological advances in the domestic sphere are yet to come, there is an excellent opportunity to get the ergonomics right before the mass introduction of mechanical aids to housework.
Job title: housewife By Harold W. Jacobson, Job Analyst National Company Inc., Malden, Mass. Grade: High
Description: • Functions in several capacities and offices performing a wide variety of duties semi-routine in nature but where the exercise of independent judgement is required in the application of practices and policies to situations not previously covered. •
Effects the purchase of a wide variety of organic materials for processing, giving special consideration to costs, market conditions, and state of material. Plan, layout, and schedule processing operations, maintaining strict control of flow and inventory to meet schedules. Conduct necessary chemical operations, using various heat treatments as required to transform basic organic materials into completed form for distribution to consumer.
• Maintains budgeting, cost control and cost accounting systems, operating within a limited financial framework. Strike semi-monthly trial balances to determine relationship between accounts-payable and accountsreceivable and, as required, perform necessary magic to bring accounts into balance. •
Operates and maintains a variety of manually and electrically powered equipment for heating, cooling, stitching, suctioning, cleansing, etc.
• Performs other miscellaneous duties of a routine nature not specifically mentioned, but where such duties are a normal outgrowth of the job.
Applied Ergonomics September 1970
223
Education (This factor appraises the minimum amount of theoretical education required, however attained). Broad general knowledge of several specialised fields such as chemistry, mechanical and electrical engineering, marketing, accounting and fundamentals of human relations. Complexity of duties (This factor appraises the need for initiative, ingenuity, and independent judgement). Perform a wide variety of semi-routine duties directed toward the attainment of a general objective: the physiological and psychic welfare of a small social group. Performance requires the use of judgement in devising new methods and modifying or adapting standard practice to meet new conditions. Responsibility (This factor appraises the responsibility for equipment, material, process, and health, safety, and work of others).
according to the availability of appliances, in addition, of course, to 'culturally' determined patterns of living, house design and eating habits. The authors of the most recent critical review of published studies (Steidl and Bratton, 1968) make it clear that further studies in many areas are needed.
Effort A considerable body of information is available on the amount of effort (usually in terms of calories per unit of time) expanded in a variety of household tasks. Table 1 (collated from a number of sources) presents in general terms energy costs for selected activities.
Table 1 Energy (which is measured in joules/minute, with calories/minute given in brackets) costs for selected activities.
Complete responsibility in terms of costs, methods, and personnel for equipment, material, process etc. Supervise and direct one inept male in the performance of a limited number of routine duties such as: rub, scrub, sweep, brush, mop, polish, etc.
Energy Joules/ minute
(Calories/ minute)
Activity
4"18
(1)
Resting
Effort (This factor appraises the mental and/or visual demand required).
4"18-8"37
(1-2)
Seated - sewing, knitting, paring potatoes. Standing - ironing, dishwashing, stooping to 559 mm (22") above floor.
8"37--12"55
(2--3)
Walking, sweeping, hanging clothes from basket on floor or table.
12"55-16"74
(3--4)
Washing floor, waxing floor, bedmaking, changing sheets, cleaning carpeted stairs.
Over 16"74
(Over 4)
Picking up items from floor, climbing up and down stairs, weeding garden.
High degree of concentration where the volume and nature of work require unusual co-ordination of hand and eye.
Working conditions (This factor appraises the surroundings or physical conditions under which the job must be performed. It includes health and accident hazards). Somewhat disagreeable working conditions due to exposure to dust, dirt, heat, etc. Exposure to accidents where results will probably be minor in nature: cuts, bruises, burns, etc, which, although painful, are not incapacitating in nature. Health hazards negligible. Fatigue factor high." Ergonomics and housework
From the ergonomics point of view, we would primarily be interested in those aspects of the task that are listed, lightheartedly but accurately, as 'operate', 'perform', 'effort' and 'working conditions', although not necessarily in that order. It would, in fact, be appropriate to look at them both from the point of view of how much is already known, and what gaps there are in current knowledge. The greatest number of published studies on the housewife and work in the home have come from the United States. It might be thought that such transatlantic findings would be conveniently extrapolated to the British scene. Direct extrapolation is not always the solution, however, for the principal reason that 'home-making' methods, attitudes and 'standard' equipment are not necessarily the same in both countries. In 1965, for instance, it was calculated that 81.4% of American homes had washing machines and 13-5% dishwashers (Steidl and Bratton, 1968). The comparable figures for Britain in that year were 56% had washing machines and less than 1% had dishwashers (Electricity Council, 1970). Methods of cleaning, laundering and food preparation will thus differ 224
Applied Ergonomics September 1970
The amount of physical effort required for the majority of household tasks, as Table 1 shows, is not great, especially as the times spent on tasks are usually both of short duration and under the voluntary control of the housewife. So it is not necessarily the total daily amount of energy expended that is of importance in the home. It is more often the physiological strain placed on particular muscles by the maintenance of static posture or the prolonged use of certain limbs or body segments. Calorimetry - the direct or indirect determination of the amount of physical energy expended during any activity - is not the most appropriate method by which to determine the effort expended by only one or two or small groups of muscles. The technique of measuring muscle activity is known as electromyography. To quote Steidl and Bratton (1968): 'Electromyography is the measurement of electric phenomena occurring in muscle during contraction and can be used to determine if certain muscles are acting or not acting in different positions or
movements of the b o d y . . . The equipment is similar to that used in making electrocardiograms...' For detailed information on this technique the interested reader is referred to Basmajian (1962). For present purposes, it can be stated that, although electromyography has been applied to some problems of the seated posture (Floyd and Silver 1955: Floyd and Ward, 1969), it has only very recently been employed to ascertain the muscle activity involved in certain domestic tasks undertaken by women of differing stature at different working heights (Saville, 1969). It is hoped that an account of this latter work will appear in a subsequent issue of this journal. Clearly, however, this method could be employed to great advantage in determining the muscular cost of many, if not most, household tasks and thence to the more appropriate design of equipment and appliances involving considerable muscular effort.
Performance In the past the most widely used method of determining the appropriate way to perform household tasks has been either to ask the subject how he or she prefers to do it or to observe how the task is done - the rationale being that the individual is the best judge of his or her capacity and requirements. Relevant examples of 'preferred' working situations a r e : • 'Relation of posture to fatigue in ironing'. (Knowles, 1945) • 'Preferred depth and height for kitchen sinks'. Council for Scientific Management in the Home, 1961. However, unless the conditions under which a subject is to state a preference are carefully controlled, the'preference' may be a poor guide to the real requirements. Human beings are immensely adaptable and can accustom themselves to a wide variety of situations. This is, of course, admirable in the Darwinian sense, but it can also mean that what someone says he 'prefers' is often simply what he has become accustomed or habituated to, and it may be far from the optimum. Nevertheless, an individual can when his attention is drawn specifically to a selected aspect, or some selected aspects, of a situation or object, be shown to be highly reliable in his judgement of the subjective ease and comfort of that situation or object. The 'preference' method therefore, properly applied, is a most useful technique for evaluating the performance of a task. Some studies have related preferred working positions to physiological and/or anthropometric measurements; an example of such an investigation into ironing (see Fig 1) is given by Knowles (1945) and, more recently, Ward and Kirk (1970)have reported an investigation into the relationship between preferred working surface heights for various tasks both standing and seated and some anthropometric dimensions. An earlier publication (Floyd et al, 1965) dealt with the physiological, anatomical and psychological principles that should govern the design of household jugs. A number of publications dealing with the design aspects of domestic appliances have pointed to ergonomic faults in such designs. (Anon., 1961; Anon., 1962a, 1962b).
Operation In this country, and some others, an increasing emphasis is being placed on the desirability of more leisure, or
A Fig 1
B
The effect upon posture of ironing at different
heights:A - at a height suitable for the subject B - 76 mm (3 in) lower. (Adapted from Knowles, 1945).
additional time in which the housewife may undertake gainful employment. The development of equipment to take over, or facilitate, her tasks in the home will presumably continue. And it is in this area that ergonomics can play a vital part. No one will argue against the need to make equipment fit the user so that both can perform to maximum advantage. It is necessary to determine if the operation of equipment by the user, either in terms of overall expenditure of energy or of individual muscle/muscle group activity, is within her physiological compass. The answers are unlikely to be the same for a widow of 60 managing her own bungalow and the young housewife who still plays hockey for the Old Girls. Even more fundamentally, equipment of every kind, whether stationary or movable, should at least be in accord dimensionally with the user. Too often however, the solution to this dimensional problem has been to make it suitable for the average user. In practice this means that all users above the 'average' and, often more critically, all below the 'average' are incorrectly or, at best, less well catered for (see Fig 2). It is in addition forgotten (or probably not known) that an individual who is, say, 'average' as regards stature, is not necessarily 'average' in other bodily dimensions. To provide, for example, a fixed wall cupboard or storage unit to the top shelf of which persons of 'average' height can reach means, first of all, that it suits no one shorter than this 'average' because they
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will not be able to reach up to it; and secondly, because the determinant is more accurately arm reach plus stature, not stature only, even persons of 'average' stature but of less than 'average' arm reach will also not be properly suited. It is the range of sizes of persons or, rather the range of the relevant anatomical diriaensions in the appropriate group of persons, that is of primary concern in determining the correct dimensions and siting of equipment. To return to the example of the fixed wall cupboard: the solution would be to consider the range of arm reach lengths, plus stature, of the population to be catered for. If the top shelf of this cupboard is to be within reach of, say, all adult British women, then the upper limit should be based on the shortest arm reach of the shortest woman. For some solutions to dimensional problems, dearly, only one end of the appropriate range of human dimensions needs to be taken into account. The example of the wall cupboard shelf required the main consideration to be placed on the lower end of the arm reach and stature range. Clearance through apertures, the lengths of beds, widths calculated for multiple seating are examples where the stature or maximum widths of the tallest and/or largest persons only are required. Difficulties arise when the requirements of both tall and short (or thin and fat, or old and young, or combinations of any or all of these) have to be met in one solution. As has been stated, the 'average' is seldom the right solution. The answer is flexibility or adjustability. Equipment should be
capable of adjustment to suit the range of sizes of people for whom it is intended and the range of the particular anatomical dimensions or physiological capacities relevant to the operation of the equipment. Adjustability may be incorporated in one piece of equipment (the typist's chair), or it may require two or three variations of the same object (the 5 sizes of chair and desk recommended for schools BS 3030:1959 is an example), or one item of equipment, designed to suit the smallest user, may be supplied with plinths of differing thicknesses to raise it to levels suitable for both 'average' and tall users. The ineffectiveness of solutions based on 'average' users is further emphasised by the fact that the physical dimensions of people are changing. At a recent meeting it was stated that " . . . . over the past century, Europeans have shown a startling and consistent increase in average mature height of the order of 0"6 cm per d e c a d e . . , thus in thirty years' time the population is likely to be about 2-0 cm taller on a v e r a g e . . . " (Broman Dahlberg and Lichtenstein, 1942, quoted by Davis and Beevis at a Conference organised by the Institute of Mechanical Engineers, September 1969). In planning for the future, therefore, this increase must be borne in mind, together with the fact (ibid) that, in about thirty years' time " . . . . the period of growth to about full adult stature will be 1 2 - 1 4 years instead of 1 5 - 1 6 years as at present and the new post-adolescent will be several centimetres taller than his counterpart in the past . . . . " Whether this continuing increase in size will be matched by a parallel increase in muscular and general physiological capacity is not necessarily automatic, but raises some intriguing problems for future design. Optimum operation of equipment, in addition to requiring dimensional accord with the user, needs also of course to be capable of easy and safe control.(see Fig 3). Examples of the types of questions that require to be satisfactorily answered to ensure such proper control a r e : 1. Do the controls on an appliance move in the accepted direction, or are they reversed from the usual procedure? 2. Are controls clearly marked? Can the on-off positions be distinguished clearly? 3. Are intermediate settings marked so that the control setting can be adjusted accurately? 4. Are controls easily accessible? 5. Will it be dangerous to reach them while the appliance is in use? 6. Are the controls arranged in logical order of use? The above is not a comprehensive questionnaire examples of the types of more exhaustive check lists necessary to ensure safe and easy control can be found in Morgan et al (1963) and Murrell (1965), and reference to this topic was made in the first issue of this journal (pages 26 to 28).
Working Conditions Fig 2 This illustration, from Erik Berglund's book 'Skap' (Svenska SI6djf6reningen, 1960) is an example of the inadequacy of offering a single solution to a design problem without taking into account the varying requirements of users.
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Accepting that the home, and particularly certain areas of it such as the kitchen, is a work place in the industrial sense, then current recommendations for and knowledge of the thermal, visual and acoustic environment characteristics desirable for workplaces are relevant. FroIa the ergonomic point of view therefore, the Ergonomics for Industry publications Nos. 6 'Noise in Industry', and 8 'Thermal
comfort in Industry', published in this issue as chapters 8 and 9 of the handbook (Applied Ergonomics, 1.4, 210-222), could well be appropriate to the domestic working situation.
Conclusion
It is evident that a certain amount of ergonomics information already exists which could be used by architects, interior and industrial designers, and domestic equipment manufacturers, more than it is at present. However, it must also be emphasised that more attention should be given by research workers to ergonomics problems in the home; only too often still, when ergonomics advice is requested by architects or designers, it becomes clear that all the necessary knowledge is not yet available. This short paper does not set out to offer detailed lists of investigations that need to be undertaken in the domestic area. It must suffice to suggest that two basic approaches should be made to the problems of the home and housework:1. Surveys need to be undertaken to determine what are the desirable and satisfactory characteristics required by the housewife in domestic equipment, layout and the environment; and . Experimental studies are required into those problems which are known to exist and those which will come to light as a consequence of surveys in these areas.
References
Anon 1961 Design, No. 1 5 1 , 6 1 - 7 0 . Design analysis 22 - washing machines. Anon 1962a Design No. 160, 5 2 - 5 7 . Design analysis 24 - vacuum cleaner. Anon 1962b Design No. 163, 3 2 - 3 7 . Design analysis 25 dishwasher Basmajian, J. V. 1962 'Muscles alive: their functions revealed by electromyography'. 2nd edition. Baltimore: Williams and Wilkins. British Standards Institution 1959 'Pupils' classroom chairs and tables'; BS 3030: Part 3. Council for Scientific Management in the Home 1961 Preferred depth and height for kitchen sinks. (Unpublished report). Electricity Council 1970 Personal communication from the Electricity Council. 30 Millbank, London, SWl. Floyd, W. F., Harding, R., Kirk, N. S. and Ward, J. S. 1965 Ergonomics, 8.4, 455--465. Some ergonomic aspects of household jugs. Floyd, W. F. and Ward, J. S. 1969 Anthropometric and physiological considerations in school, office and factory seating. In 'Sitting Posture' 18-25;ed. E. Grandjean. London: Taylor & Francis.
Fig 3 The necessity for easy and safe control of appliances is emphasised by this illustration (from Design, 160, 1962), where the carrying strap on the vacuum cleaner slips off the shoulder; and the hand that should be free to control the appliance has to be employed solely to hold it. The posture thus adopted is awkward and likely, if maintained for long, to be fatiguing.
Knowles, E. E. 1945 Journal of Home Economics, 3 7 , 5 8 4 - 5 8 7 . Relation of posture to fatigue in ironing. Knowles, E. E. 1946 CorneU University Agricultural Station Bulletin, 833, 5-57. Some effects of the height of ironing surface on the worker. Morgan, C. T., Cooke, J. S., Chapanis, A. and Lund, M. W. (Eds.) 1963 'Human engineering guide to equipment design'. London: McGraw-Hill. Murrell, K. F. H. 1965 'Ergonomics - man in his working environment'. London: Chapman and Hall. SaviUe, B. F. 1969 Optimum domestic work heights - a postural analysis. Ph. D. Thesis to University of Technology, Loughborough. Steidl, R. E., and Bratton, E. C. 1968 'Work in the home'. London: Wiley and Sons. Ward, J. S., and Kirk, N. S. 1970 Ergonomics (in press). The relation between some anthropometric dimensions and preferred working surface heights in the kitchen.
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