A new study says that regular and vigorous exercise can activate dormant stem cells in the heart which heal the damage caused by a heart attack . The study by Liverpool John Moores University is the first to suggest that a simple exercise programme has an effect similar to that of the stem cells when they are cajoled into producing new tissues through special shots. Strenuous exercises includes 30 minutes of running or cycling daily enough to work up a sweat the European Heart Journal reports. A study on healthy rats showed that an equivalent amount of exercise resulted in producing more