Keeping a healthy heart

[I read in Steven Covey's 7 habits book the following thing (paraphrased)] Heart is a muscle that pumps bloods in our system. The amount of pressure that the heart exerts in doing so is called the blood pressure. If the heart muscle is not strong or if our arteries have fat deposits, the heart has to exert higher pressure to pump blood through our system (resulting in increased "Blood Pressure"). To keep the heart muscle strong and healthy, exercise is very important. With exercise, we strengthen our heart muscle by increasing its beat rate, much like we exercise our other muscles and brain. On average, a person should aim to increase his/her heart rate to about 60% of 220-age for about 30 minutes every day.