We’re constantly being told that exercise is good for our health and can protect against a host of diseases.
But a new study suggests you really can have too much of a good thing – especially if you’ve already got a dicky heart.
Researchers have identified a so-called cut-off point where exercise loses its protective effect and becomes dangerous.
Heart attack survivors who ran fewer than 30 miles a week – or walked fewer than 46 miles – were 65 per cent less likely to die from another heart-related events.
But exercising too much, specifically running more than 4.4 miles a day or walking briskly for over 6.6 miles a day, increased the risk of another heart attack.
When the figures are extrapolated, they suggest that one in 20 of us is regularly overdoing it – significantly raising the risk of an early death.
The study, conducted at the Lawrence Berkeley National Laboratory in the U.S., found ‘clear evidence’ of an increase in deaths among heart attack survivors who exercise to excess.
They have now suggested the term ‘cardiac overuse injury’ to describe the fall-out of this ‘more exercise is better’ strategy
In the study, the relationship between exercise and heart disease-related deaths in about 2,400 physically active heart attack survivors was examined.
The study confirmed previous reports indicating that the heart-health benefits of running and walking were the same – providing people knew it takes twice as long to burn the same number of calories when walking.
Study co-author Dr Paul Williams said the new study proved the benefits of running or walking ‘do not accrue indefinitely and that above some level, perhaps 30 miles per week of running, there is a significant increase in risk.
‘Competitive running events also appear to increase the risk of an acute event,’ he added.
However he did stress that the findings from the study sample – which only looked at heart attack survivors – was difficult to apply to ‘the entire population of heavy exercisers’.
Responding to the research, Amy Thompson, Senior Cardiac Nurse at the British Heart Foundation, said: ‘We’re often told how beneficial physical activity is for our heart health.
‘However, this study suggests if you’ve had a heart attack you may be putting yourself at risk of another if you participate in vigorous exercise above the recommended amounts – such as running for more than 30 miles per week.’
Meanwhile, in the same issue of the journal Mayo Clinic Proceedings, investigators in Spain reported on the death trends of elite athletes.
They tracked 42,000 top athletes who had participated in a range of sports including football, baseball, track and field, and cycling, including Olympic level athletes and participants in the Tour de France.
Senior investigator Dr Alejandro Lucia, of the European University Madrid, said: ‘What we found on the evidence available was that elite athletes, mostly men, live longer than the general population, which suggests that the beneficial health effects of exercise, particularly in decreasing cardiovascular disease and cancer risk, are not necessarily confined to moderate doses.’
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