Bad news today for idle crisp-scoffing lardos who seldom get much attention from the opposite/desired sex: when you finally do achieve some boudoir action, there is a measurable chance that the excitement will kill you.

The news comes in a new study-of-studies conducted by docs in America, investigating the causes of heart attacks. It seems on first superficial glance that the safest thing is to stay on the sofa and make sure that nobody joins you there. Low-level physical activity of any kind, including steamy sessions of rumpy-pumpy, triple the risk of a sudden catastrophic ticker mishap. Proper exercise quintuples it.

Even so, the medi-boffins conducting the research caution that their message should not be misunderstood.

"It would be really bad if someone thought our paper means people should not exercise," Dr Issa Dahabreh tells the AP. "If anything, it's the opposite."

Rather than advocating a state of terrified immobility so as to avoid any potentially fatal exertion or nookie, the docs point out that in general people who suffer heart attacks are older - typically late 50s or more. Furthermore, the deadliness of sex - or indeed any other kind of exertion - mainly results from not having done any for a long time previously.

In other words, the more you do it the safer it is. And should companionship not be forthcoming, rather than moping in a sessile condition on the floor of the pie cupboard, one should stay fit in order to avoid fatal consequences when you finally do get lucky.

"Engaging in regular physical activity is a requirement for maintaining a long, safe, healthy sex life," says heart disease expert Mercedes Carnethon, commenting on the new calculations to the AP. "If this isn't more motivation for people to maintain some degree of physical activity, I'm not sure what is."

Particularly for those of a certain age having abstained from exercise or jig-jig for some time, the advice is to ease back into it gradually: one should start exercising again with some relatively gentle activity as opposed to, say, the Ironman Triathlon. Likewise those having had a lengthy stay on the bench sex-wise should probably not kick off with a huge Italian prime minister style orgy.

Nonetheless one should also bear in mind that risk to individuals is very low even if you do suddenly get lucky after years of belt-busting idleness. Among 10,000 people all suddenly cranking up their activity levels by an hour a week, only two or three would suffer heart attacks.

The research is published today in the Journal of the American Medical Association. ®