as everyone knows， either fast walk or slow walk does good to the muscles （肌肉） and lungs of human. so people walk to build up their body， or to lose weight. but only some of them know that taking a walk every day is also good for protecting man's heart. heart attack has become the first disease in the world because most people suffer from it.　taking a walk can improve the blood supply to our heart. if you try to walk as often as possible， you'll have a healthier heart.