Energetic Trade-Offs and Physical Activity During Childhood and Adolescence

One unique aspect of the human life span is an extended childhood. Compared to other primates, human offspring grow more slowly and remain dependent on their parents to produce food for much longer post-weaning. All energy during childhood is focused on somatic growth and maintenance, including substantial continued investments in brain growth, learning, and immune development. This chapter examines the important environmental factors that influence energy allocation strategies: resource availability, exposure to infectious diseases and parasites, and mortality risks. Research that demonstrates trade-offs between immune function and growth during childhood is summarized. Putting energy toward physical activity is hypothesized to trade-off similarly against these competing demands. Once pubertal maturation begins, there are increases in energetic demands for the pubertal growth spurt and investment in reproductive maturation. Research from traditional and modern populations suggest that competing demands of somatic growth (including brains) and reproductive maturation influence physical activity during childhood and adolescence.