Exercise is a good way to improve a bad mood and to change a bad habit. In this way, exercise serves a double purpose. For thousands of years, people had to hunt for food and were very active. In the last 100 years, modern machines have made it possible for people to live with almost no exercise. This lack of activity has led to new health problems such as obesity and heart trouble.
Exercise helps burn excess calories and prevents obesity.
A person who keeps a normal weight is less likely to have a heart attack in later life. The heart of a person who is in good physical shape can do the same work with fewer heartbeats. Many people who exercise regularly will have values in the 60s. Blood pressure tends to be lower in people who exercise. Thus, the heart doesn't have to pump as hard.