Confirming that too much of a good thing can be bad, especially for your heart, researchers have found that overdose of high intensity exercise may increase risks of a heart attack or stroke in those with existing heart disease.For the study, researchers tracked the frequency and intensity of physical activity and the survival of more than 1,000 people with stable coronary artery heart disease for 10 years.All the participants, most of whom were in their 60s, had attended a cardiac rehabilitation programme to help them exercise regularly and ward off a further heart attack or stroke.The most physically inactive were around twice as likely to have a heart attack/stroke as those who were regularly physically active and they were around four times as likely to die of cardiovascular and all other causes.
But somewhat surprisingly, those who did the most strenuous daily exercise were also more than twice as likely to die of a heart attack/stroke, the findings showed.Another study found that young men undertaking endurance exercise for more than five hours a week may increase their risk of developing an irregular heart rhythm in later life.While it seems "counterintuitive" to think that physical activity could aggravate heart disease, other smaller studies have also suggested this possibility, experts added, with endurance training in particular, linked to an acute (reversible) pro-inflammatory state.The findings appeared in the journal Heart.