That does not necessarily mean that a child who does little sport or exercise and enjoys the chair-bound leisure pursuits of many modern children could walk three miles to school without discomfort as his grandparents may well have done.
What it does mean is that the child's ability to transport oxygen from the atmosphere through the lungs, the heart and the blood system to the muscles which will then support physical activity, what is known as aerobic or cardiovascular fitness, is not on a downward spiral.
This is confirmed by research into the physical activity and aerobic fitness of children over the past 10 years at the University of Exeter which shows that although children have surprisingly low levels of physical activity - girls are even worse than boys - their aerobic fitness is adequate.
How can this be? The children we have monitored with microtransmitters minute by minute over a minimum of three days show half the girls and more than a third of the boys did not even experience the equivalent of a 10-minute brisk walk during the whole period of monitoring.
Yet these under-used bodies are still working well. But for how long? We all know what happens if you don't service a new car - absolutely nothing. It only starts to go wrong, rapidly, as it gets older and its system rebels against the lack of care. If these sedentary children don't get moving, their fitness levels are unlikely to follow them into adult life.
Evidence from the recent Allied Dunbar National Fitness Survey suggests that adult physical activity patterns are established during childhood and adolescence. In particular, physical inactivity tracks from childhood into adult life. Many adults have adopted sedentary lifestyles that their children simply repeat. It is a vicious circle.
Yet regular participation in physical activity during adult life can decrease the risk of heart disease, lower blood fats, reduce high blood pressure, counter obesity, retard osteoporosis (brittle bones), improve muscle tone, help to prevent back pain, and increase psychological well- being.
To grow into fit and healthy adults we must promote children's physical activity as well as our own. Parents should campaign on behalf of their children for traffic-calming schemes, safe walkways, extensive cycle paths, attractive play areas, and subsidised and easily accessible leisure facilities.
Children should be encouraged to walk or cycle to school. Children's use of leisure facilities should not be dependent on the availability of an adult to drive them to some out-of-the-way spot.
Local authorities and community leaders should explore the provision and attraction to children of youth clubs, sports clubs, and other similar community organisations. School governing bodies should appraise the rapidly diminishing resources they devote to physical education; they must also evaluate how well they build the links between school and community that are likely to promote after-school physical activities among their students.
Physical education teachers should examine their curriculum and extra- curricular provision and confirm that, within the financial constraints within which they are working, they are offering a balanced programme that provides opportunities for all children and facilitates the adoption of active lifestyles that are likely to be sustained into adult life.
The future health and well-being of our children and their children may depend on the adults of today.
The writer is professor of health and exercise sciences at the School of Education, University of Exeter.
Overleaf Professor Armstrong sets a questionnaire which you can use to discover how active your children are.Reuse content