|Activity, Energy Expenditure and Energy Requirements of Infants and Children (International Dietary Energy Consultative Group - IDECG, 1989, 412 pages)|
|Methods to assess physical activity and the energy expended for it by infants and children|
|2. Methods of acquiring information on the physical activity of infants and children|
Some questionnaires may be conscientiously filled in by a parent in 15-20 minutes, others may require the services of a skilled, experienced interviewer and may take 1-2 hours to complete. Which variant is chosen depends on the objective of the study, on the target population, and on the background and beliefs of the investigator.
Physical activity, or the lack of it, will affect mental and physical development almost from the age at which the infant begins to crawl around. Therefore, activity may need to be measured from the age of between 1 and 2 years. Since we are concerned here with problems of measuring energy and activity in infants and children, it is pertinent to ask the question: "Up to what age will these measurements be significantly different from a similar assessment in adults?". It is difficult to give a precise, generally valid answer to this question, since it will be affected by various factors such as the type of population (a poor village in a developing country or a middle-class group in an industrialized country, for example), the type of activity (children's games), weight and body composition, and probably others, in most situations it is likely that from the age of young adolescence there are no major differences from adults, so the age span discussed in this paper is roughly from 1-2 years up to 10 years.
In the older part of this age range, children can be questionned directly about their physical activity but filling out such a questionnaire would require the services of a skilled interviewer; it is improbable that any self-administered system will, in general, be suitable for children up to 10 years of age. Otherwise, the techniques of acquiring data on physical activity in children will often be very similar to the equivalent situation in adults.
Basically, the information needed about physical activity is (1) a detailed description of the activity, (2) the intensity (preferably, by objective assessment rather than subjectively), (3) the duration, and perhaps (4) the total energy expended in the activity (which may be estimated indirectly from existing tables and may not require actual direct measurements of oxygen consumption).
Data on these matters will permit us to speculate with reasonable precision about whether or not the child is active, how active he or she is and for how long, and roughly the likely energy expended in the activity.
To obtain the requisite information by questionnaire might be done via a 24-hour recall to the parent, plus an extrapolation to the previous days to arrive at an impression about the habitual activity levels of the child. However, it is difficult to imagine that what we learn in this way can be anything other than qualitative and, at best, may allow ranking of the child into one of 3 or 4 groupings. SARIS (1985), in studies on Dutch children aged from 4 to 12 years, used questionnaires of this sort, and examples of the type of questions asked are given in his paper.
A diary method of recording what an individual child actually does, used prospectively either by a parent or other observer, could, at least theoretically, produce useful data. However, it requires considerable dedication by the observer - perhaps noting down once every 2 or 5 minutes exactly what the child is doing at that moment. The recording has to be relatively simple, e.g., perhaps only the four categories of sitting, standing, walking, and running (with each of the last two being described in two levels - 'high' end 'low') would be adequate. The actual observation does not, of course, have to extend over the whole waking day and might, for preschool children, have a duration of only a few hours, from say, mid-morning to late afternoon. In order to obtain observations which would probably be more representative of normal behaviour, these observation periods should take place on at least 3 different days to avoid an unusual day giving bias to the results. For school children, much of the school period entails enforced inactivity, and the intervals between classes and the immediate after-school period might, for various reasons, be difficult to record and might not represent average behaviour; the week-end might be more representative of normal activity patterns.