“Overdosing on high intensity exercise may actually increase the risk of death from a heart attack or stroke in those with existing heart disease, suggests German research published online in the journalHeart.
Similarly, a second Swedish study in the journal suggests 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.
Both sets of findings indicate a J-shaped curve for the health benefits of exercise, with more not always meaning better, and raise questions about the intensity and duration of physical activity at different times of life, says a linked editorial.
In the German study, the researchers tracked the frequency and intensity of physical activity and the survival of more than 1000 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.
Current guidance recommends that heart disease patients should do up to an hour of moderate intensity aerobic activity at least five times a week. Around 40% were physically active 2-4 times weekly; 30% did more; 30% did less. Overall, one in 10 said they rarely or never did any exercise.
Exercise frequency tended to tail off off during the monitoring period, although it remained stable for those physically active 2-4 times a week.
After taking account of other influential factors, 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.”
Full article here