|Activity, Energy Expenditure and Energy Requirements of Infants and Children (International Dietary Energy Consultative Group - IDECG, 1989, 412 pages)|
|Long-term developmental implications of motor maturation and physical activity in infancy in a nutritionally at risk population|
Researchers investigating relationships between nutrition and function face formidable challenges in the search for an answer to the question of whether the maintenance of energy balance at low levels of energy intake in infancy and early childhood has adverse behavioral or psychological effects in adolescence and adulthood. In addition to requiring longitudinal data which are costly, the nature of the task precludes tightly controlled experiments with infants and children. Moreover, the question calls for a close integration of concepts and methods from, at least, nutrition, physiology and developmental psychology. Difficulties notwithstanding, the question must be faced as it is a crucial aspect of the problem of human capital formation in many developing countries (POLLITT and AMANTE, 1984).
The question as generally formulated (Figure 1; BEATON, 1984) suggests that physical activity as a component of energy expenditure and physical activity as a determinant of development are equivalent. Such a formulation, however, is equivocal. Theoretically, it is to be expected that the nature of physical activity as a dependent variable in the equation of energy balance, and as an independent variable in the equation of developmental effects must differ substantively.
Physical activity as a component of energy expenditure includes all body movements (directed e.g., grasping and non-directed actions). Measurements of energy expenditure resulting from physical activity yield information on a single dimension of an action; their behavioral or adaptive significance is irrelevant in such a context. On the other hand, physical activity of developmental significance is a more complex construct which does not lend itself to a simple unidimensional expression, particularly when we consider the multiple systems and subsystems involved. In addition to energy expenditure, developmentally meaningful motor actions imply the involvement of critical dimensions related to the organization of motor schemes, information processes, and motivational and affective elements, among others. The time-space configuration of a behavioral action goes beyond the simple summation of how energy was spent. At issue is how to identify developmentally meaningful motor actions.