London, March 23 : A new research suggests that spikes in physical activity -- such as during sex -- can have the opposite effect -- triggering heart attacks and cardiac arrests.

The increased risk - as much as 2.7 times higher than normal - applies mainly to people who are otherwise unhealthy, and can be reduced by regular physical activity. But a small risk does apply to everyone.

Scientists at Tufts and Harvard Universities in the US reviewed the results of a number of previous studies to come up with the findings, the Journal of the American Medical Association reports.

They found that "episodic activity" was associated with more than two and a half times increased risk of heart attack and sudden cardiac death (SCD), according to the Telegraph.

However, regularly indulging in exercise - including sex - offset the increased risk by almost half for each additional time per week it was carried out.

"Regular physical activity has been identified as strongly associated with a decreased risk of cardiovascular disease and related mortality," the researchers wrote.

They looked at more than 14 studies looking at what caused heart attacks and found that a small but significant number happened during physical and sexual activity.

They found that all kinds of physical activity accounted for three and a half times increased risk and sex 2.7 times. (IANS)