According to a new research, having sex increases the chance of suffering a heart attack.
Scientists have revealed that patients are twice as likely to suffer a heart attack one hour after sex than those who do not have sex.
For those who do little or no exercise, the risk increases four-fold. The results contrast with other studies which have shown that men actually improve their health by having regular sex.
But they support the widely-held belief that sex can bring on a heart attack among those who are over 50 or overweight.
The latest study - carried out by scientists at the Karolinska Institute, in Stockholm, Sweden - was based on interviews with 650 people admitted to hospital with their first heart attack.
More than three-quarters were men and half were aged between 45 and 60.
They were interviewed shortly after recovery about any symptoms and the circumstances, including sexual activity, during the four days leading up to their heart attack. They were also asked general questions about the frequency and timing of sex and how often they exercised.
The researchers - whose work appears in the journal Heart --then identified those patients who had had sex around two hours before their attack.
Using medical records they assessed the patients' likelihood of having a heart attack and compared that to symptoms they exhibited one hour after sex.
According to previous research, about one in 100 attacks results from sexual activity - when the heart rate increases to 120 beats a minute and blood pressure rises.
However, the Swedish scientists emphasised that their study looked only at people who were already suffering from heart disease.
And they pointed out that, although the risk of heart attack increased after sex, it was still very small.
As a result, they conclude that sex once a week poses only 'minimal risk'. And they said doctors should encourage heart patients to exercise more frequently, rather than abstain from sex.
A spokesman for the British Heart Foundation said: 'Those with heart disease should not be afraid to resume their sex lives, as part of a return to a healthy, active lifestyle.
'There is no reason why sex should not become an integral part of your life after having a heart attack.'
Previous studies have shown that sex becomes much more dangerous for men who are cheating on their wives. The physical strain on the heart is matched by the psychological anxiety of having an affair.
Heart disease, including strokes, claims an estimated 250,000 lives in Britain each year.
It accounts for one in four deaths in men and one in five deaths in women.
