Computer work dominates occupational life in many countries worldwide, e.g. within the European Union [1
]. Typically, 70-75% of the workforce use computers in their jobs [2
]. Computer work is usually performed in a seated posture. Therefore, jobs characterized by extensive use of computers are likely to imply extensive periods of sitting and low levels of energy expenditure.
Computers particularly dominate work at call centres (CC), or Contact centres, Customer contact centres
or Customer support centres
, as they are increasingly termed. CCs employ 2-3% of the work force in many Western countries, and have been claimed to be one of the fastest growing trade sectors since their introduction on a larger scale in the mid 1990ies [3
]. In 2005, the number of CC agents was estimated to be approximately 4 million in the US, 200,000 in France, 300,000 in Germany, 800,000 in the UK, and 100,000 in Sweden [4
]. Work in CCs has been described as sedentary, repetitive and monotonous, both mentally and physically [3
]. However, CC work varies in mental complexity from short cycled repetitive operations, such as ticket booking and phone-number information, to complicated and intellectually demanding tasks such as financial or medical advice and computer support. The common denominator for all CC work is the total dominance of customer communication by telephone, assisted by computers. Thus, CC work is mostly performed while seated at a computer workstation [5
Office work comprising extensive computer use has been suggested to be a risk factor for musculoskeletal disorders, and this apprehension has been supported by several studies [6
], while others have been less conclusive [13
A growing concern has, however, been raised about the possible health effects of extensive sitting at offices and in other occupations beyond possible musculoskeletal risks. Sedentary behaviour per se is known from public health research to be associated with a range of serious health risks, including obesity, hypertension, type II diabetes, metabolic syndrome, venous thromboembolism, cardiovascular diseases, cancer and also increased mortality [15
]. These risks are associated with sitting per se, to a large extent independent of whether the individual is otherwise physically active [17
]. Since most people between 18 and 65 years of age spend a large part of their wake time at work, and since several occupations has been shown to imply extensive sitting [25
], sitting in occupational life may contribute significantly to the negative public health effects of sedentariness.
Traditional office ergonomics has primarily focused risk reduction strategies on decreasing the amplitude of muscle and joint loads, but recent studies have stressed the importance of focussing on temporal aspects of work, i.e. the exposure variation [21
]. In general, ample variation in physical exposure has been proposed to be a major prerequisite for good musculoskeletal health [28
]. This focus on the time-line of exposure rather than just the exposure level is well in line with recent public health research on sedentariness, suggesting that interventions should not only address the total duration of sitting, but also the time distribution of breaks from sedentary time [30
In a typical office setting comprising extensive seated computer work, physical variation can be achieved through gross body movements, including leaving the work station. Ideally, this variation would occur naturally if the job per se contained tasks offering (non-seated) exposures differing markedly from those associated with computer work [31
]. In CC settings, such "productive variation" is not easy to create, since very little core CC work can be done away from the computer workstation. The major feasible option for obtaining variation is therefore to change between seated and standing work-postures at the computer. Other, more infrequent opportunities are to leave the computer for coffee and lunch breaks, visit the rest-room, or attend to staff-meetings.
In spite of the increasing awareness among researchers and practitioners that physical variation is important, even in terms of breaking up extensive sedentary periods, only a few studies have been devoted to variation in physical workload among office workers performing their usual work. Juul-Kristensen & Jensen [32
] classified variation among office workers in broad categories, but did not collect any quantitative data. Other studies report postural variation during computer work, either in the field [33
] or during controlled tasks in the laboratory [27
], but these studies have concentrated on arm and neck postures. The occurrence of seated (sedentary) and non-seated work among office or computer workers has been addressed in only a few studies, using either self-reported time of sitting [37
] or inclinometry [39
]. None of these studies assessed the time-pattern of seated and non-seated postures.
One reason that variation in occupational loads and postures has rarely been studied in quantitative terms is probably the paucity of standardized methods to measure "variation" [28
]. Interestingly, a similar frustration in public health research recently led to the proposal of a generic technique to characterize the distribution of sedentary behaviour, based on mathematical modelling [41
]. Conceptually, "variation" in any physical exposure has been suggested to include three different aspects [28
]: A) How much
does exposure change; B) How fast (or how often)
does exposure change; C) How similar
are exposure periods.
Ergonomic recommendations for variation in office work combine these aspects, in particular 'how much' and 'how often', in stating that workers should leave their computer workstation for at least 5 to 10 minutes every hour [42
]. The intention of this recommendation is to give the worker an adequate break, both from a likely sedentary posture, from a steady muscular load with little variation in the shoulder region and the arms, and from the mental demands of the dominating work tasks. None of the recommendations state explicitly whether breaks from seated should be uninterrupted or not. Thus, both an uninterrupted 5-10 minute period in a non-seated posture and shorter but more frequent breaks adding up to 5-10 minutes every hour would satisfy the recommendations. While previous research have indicated that compliance can be a critical concern in implementing initiatives related to break behaviour, no systematic investigation has yet been made of whether office workers behave according to recommendations or not.
Possible differences in the sedentary behaviour of males and females are of interest in this context, since female professional computer users, including CC operators, report more symptoms and other health-related problems than male professional computer users [11
]. The long-term metabolic health effects of sedentary behaviour also seem to differ between men and women [16
The aim of this study was to assess variation in gross body postures amongst male and female CC operators on the basis of whole-shift recordings of seated and standing/walking. To serve this purpose, the paper introduces a number of novel variables describing the temporal structure of postural behaviour. The following aspects were explicitly posed, analysing gender differences: posture duration, frequency of posture changes, similarities in the posture pattern across time, and compliance with standard recommendations for variation.