21.

Exercises have numerous physiological and physical benefits on children.
Explain in detail.

There are various physical and physiological advantages of exercise for children which are described below:

1. Exercise Controls Weight: Regular exercise helps in controlling weight. In fact weight gain occurs when child takes more calories than the requirement of his body. The unused or excess calories are accumulated as fats in his body. In this way, he starts gaining weight which ultimately leads him towards overweight and obesity.  Regular exercise helps such children in burning excess calories. The more intense the activity or exercise, the more calories they burn. Regular exercise takes the fat away and lowers the excess weight. 
2. Exercise Strengthens Bones: Exercise builds strong bones. As a matter of fact, exercise increases bone density which helps in preventing osteoporosis. If regular exercise is not performed, the bones usually lose their density, become weak, fragile and porous. Hence, exercise is beneficial for strengthening the bones.
3. Exercise Strengthens the Lungs: Exercise is beneficial for children because it enhances the lungs, capacity and their efficiency in inhalation and exhalation. It increases the size of lungs. Tidal air capacity and vital air capacity are increased.So, it can be said that lungs are strengthened and becomes capable to perform various activities for a longer duration.
4. Promotes Changes in the Brain Structure: Exercise changes the brain structure and functions in infants and young children which are beneficial for them. It also stimulates various chemicals which help the children to feel happier and more relaxed.
5. Exercise Strengthens the Heart: Exercise improves the performance and efficiency of heart. The heart responds to exercise by becoming stronger and more efficient. Exercise not only makes the muscles of heart stronger but increases its size also. Exercise helps in increasing stroke volume, cardiac output, blood volume and total haemoglobin which ultimately improves the function of heart.
6. Exercise Boosts Energy Level: Regular exercise usually make the children more energetic. It allows them to be more active and provides enough energy to do a number of activities without getting fatigue. Exercise helps in delivering oxygen and nutrients to body tissues. It improves the cardiovascular system to work more efficiently which ultimately boosts the energy level.