A few sensible bouts of jogging each week can help build a healthier system, reducing the likelihood of developing heart problems. (For Spectrum Health Beat) Even a slight improvement in your heart and lung fitness could reduce your risk of a heart attack, a new study reveals. Between 2006 and 2008, researchers assessed the cardiorespiratory—heart and lung—fitness of just over 4,500 men and women in Norway. None had heart disease, high blood pressure or cancer and most were considered at…