3. Conclusions

The assessment of physical activity in infants or children is difficult but nonetheless feasible. For most purposes one, or a combination, of various techniques can be employed - questionnaire to a parent, observation (direct or by video-camera), pedometers, accelerometers, actometers, or heart-rate recorders. Careful and appropriate use of these methods will allow reasonably detailed data on the type, intensity, and duration of activity to be monitored. For this purpose, costly stable isotope techniques have no advantage.

The exact form of the detailed data will vary with the objectives of the study, and will obviously differ in the case of the relative importance of activity for physical development, and for socio-emotional or cognitive development. If nutritional factors are thought to be influencing the ability of the child to be active (e.g., malnutrition resulting in decreased activity) then the assessment of this may require some knowledge of the food intake. There are probably few circumstances when a measurement of the energy expenditure in physical activity will be really necessary, other than perhaps in providing a more exact estimate of the energy expended in specific activities.