Why is physical activity so important for my heart?

Researchers are still trying to find out exactly why physical activity plays such an important part in preventing coronary heart disease. It seems to act in the following ways:

Physical activity helps to lower high blood pressure, and prevent high blood pressure from developing:- 

High blood pressure is one of the major risk factors for coronary heart disease. In 9 out of 10 people with high blood pressure, there is no single cause of the high blood pressure. However, unhealthy lifestyles play an important part. In particular, being overweight or obese,eating too much salt, drinking too much alcohol and physical inactivity can all raise blood pressure.
Regular, moderate rhythmic exercise such as walking, cycling or dancing helps to reduce blood pressure in people with high blood pressure. This sort of exercise may also prevent high blood pressure from developing.