As a child, you need exercise to help build your body muscles, your growth rate and control your weight. A child needs a lot of exercise in order to build up their body muscles, bones and heart. I a child is deprived of exercise they will end up with weaker bones, heart, overweight, prone to heart attacks, and many other medical issues. The child will become very lazy and all they will want to do is sleep. Furthermore, in school, the child won't have enough energy to concentrate on the assignments and stay awake in class.
If you fail to do any type of physical activity this can lead to muscle problems, the bad flow of blood to your heart, will weaken your heat, and cause you to overeat, sleep and gain an extreme amount of weight. Your body will start to retain sugar and other fats which will add fat around your heart. This in return will cause the weakening of your heat and you'll end up with a heart attack or stroke because of this.
As a child or an adult, it is very important to get out and move around. Find some sort of physical activity that you enjoy. It could be walking, swimming, riding a bike or even playing sports. You have to start now if you want to live a longer healthier life and not have tons of medical problems when you get older.