Hi welcome to HCM Dear , every health problem we face , has an apparent cause . Remove or tackle the cause , You may have develop an enlarged heart temporarily because of a stress on your body, such as pregnancy, or because of a medical condition, such as the weakening of the heart muscle, coronary artery disease, heart valve problems or abnormal heart rhythms in your case due to running , as your doctor advised . An enlarged heart may be treatable by correcting the cause. Treatment for an enlarged heart can include medications, modifying your food habits and your life style . Include essential nutrients and antioxidants - citrus fruit , green veges , Almonds ,Amla , Aloe vera , cow s milk Quit smoking . Lose excess weight. Limit salt in your diet. Control diabetes. Monitor your blood pressure. Avoid fried fast foods , fat , salt , fine flours stress , worry , over exertion , dehydration and constipation Regular walk ,do practise Yoga postures , Pranayam - Deep Breathing , Kapal bhati , in moderate speed , Anulom Vilom , Tribandh , Bhrameri , Yognidra - Shavassan under guidance of trained Guru all help you to gain physical and mental health and ensure healthy . Get modest exercise, after discussing with your doctor the most appropriate program of physical activity. Hope this helps solves your query . Take care . All the best