Exercise and kids: How much exercise per week

The question:
How much physical exercise does a child need each week?

The Pediatrician Answers:
We know that 1 to 2 hours of vigorous aerobic exercise (exercise where one moves his or her body through space) every other day has a maximal health benefit in adults. Children need at least this much if not more and they are less likely to get hurt doing it.

The type of exercise does not seem to matter with taking a walk at top speed was as good as running or biking or swimming. The goal is to get the base heart rate to double during the exercise. Anaerobic exercise such as weightlifting does not harm, but does not help physical fitness.

Why do we need exercise? We know it prolongs life, decrease number of infections, makes one feel happier and, probably most importantly, builds bones so that older people do not have as many fractures.