根据文意及首字母提示补全短文。
As everyone knows, not o____ fast walk but also slow walk does good to the muscles and lungs of human. So people walk to build up their bodies, or to lose w____. But only some of them know that taking a walk every day is also good for p____ people's hearts. Heart attack has become the first disease in the world b____ more and more people suffer from it.
Taking a walk can improve the blood supply to our hearts. If you try to walk as o____ as possible, you'll have a healthier heart.
