Too much exercise can be bad for your heart, two new studies have warned.
Research
by German scientists found overdoing high intensity exercise may
actually increase the risk of death from a heart attack or stroke in
those with existing heart disease.
And
a Swedish study, also published online in the journal Heart, 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.
The
studies support research released yesterday which showed that young men
who run marathons are more likely to need pacemakers in old age.
Both
sets of new findings indicate that more does not always mean better
when it comes to the health benefits of exercise, and raise questions
about the intensity and duration of physical activity at different times
of life.
In
the German study, the 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 sixties, 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 per cent were physically active two to four times weekly, 30 per
cent did more and 30 per cent did less. Overall, one in 10 said they
rarely or never did any exercise.
After
taking account of other influential factors, the most physically
inactive were around twice as likely to have a heart attack or stroke as
those who were regularly physically active. And they were around four
times as likely to die of cardiovascular disease and all other causes.
However,
surprisingly, researchers found those who did the most strenuous daily
exercise were also more than twice as likely to die of a heart attack or
stroke.
In
the Swedish study, the researchers questioned more than 44,000 45 to
79-year-old men about their leisure time physical activity patterns at
the ages of 15, 30, 50, and during the past year, when their average age
was 60.
Their
heart health was tracked for an average of 12 years from 1997 onwards
to gauge how many developed an irregular heartbeat - a known risk factor
for stroke.
The studies support research released yesterday which showed men who run marathons are more likely to need pacemakers in old age
They
found that men who had exercised intensively for more than five hours a
week were 19 per cent more likely to have developed the condition by
the age of 60 than those exercising for less than one hour a week.
The
level of risk rose to 49 per cent among those who did more than five
hours of exercise a week at the age of 30, but who subsequently did less
than an hour by the time they were 60.
However,
those who cycled or walked briskly for an hour a day or more at the age
of 60 were around 13 per cent less likely to develop an irregular
heartbeat than those who did virtually no exercise at all.
Despite these findings, the researchers insist that exercising remains important for the health
Researchers
suggest that this might be because the intensity of exercise is likely
to be greater at the age of 30 than it is at the age of 60, so may have
less extreme effects on the body.
Dr
Lluis Mont, of the Hospital Clinic de Barcelona in Spain, said:
‘Maximum cardiovascular benefits are obtained if performed at moderate
doses, while these benefits are lost with [very high] intensity and
prolonged efforts.’
However,
Dr Mont emphasised that not exercising at all is bad for our long term
health, adding: ‘A thin line separates accurate information and
unnecessary alarmism, leading to inactivity and consequent heart
disease.
‘The benefits of exercise are definitely not to be questioned, on the contrary, they should be reinforced.
‘The
studies, and future studies, will serve to maximise benefits obtained
by regular exercise while preventing undesirable effects - just like all
other drugs and therapies.’
Just yesterday another study revealed that running marathons can be bad for the heart.
Researchers
at the University of Manchester found that people who take part in
extreme sporting challenges when they are young are more likely to need
pacemakers in old age.
Tests
on mice, funded by the British Heart Foundation, showed microscopic
changes take place in the body due to exercise training.
This can disrupt the electrical pulse of the heart, causing the super-fit to suffer abnormal heart rhythms.
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