As far back as the 1950s, couples have been asked to strap on monitors, blood-pressure cuffs and other paraphernalia and copulate, to scientifically quantify the impacts of sex . The focus is often on whether sex can kill you by precipitating a heart attack. Happily, these studies generally show that heart rates rise during intercourse, but tolerably. The risk for sex -related cardiac arrest is vanishingly small, statistics show, though it may be greater when the act is extramarital.
The issue of sex as exercise, however, has remained largely unexplored. “There are these myths,” including that sex burns 100 calories per session, said Antony D Karelis, a professor of exercise science at the University of Quebec, Montreal, who undertook a study, published in PLOS One in October, to look at how much energy is actually exerted during sex . “But nobody had tested” those assumptions.
To do so, Karelis and his colleagues recruited 21 young committed hetero sex ual couples and had them jog on treadmills for 30 minutes, while researchers monitored their energy expenditure and other metrics, in order to provide a comparison for the physical demands of sex . The scientists next gave their volunteers unobtrusive armband activity monitors that gauge exertion in terms of calories and METs, or metabolic equivalent of task, a physiological measure comparing an activity to sitting perfectly still, which is a 1-MET task. Then the scientists sent the couples home, instructing them to complete at least one sex act a week for a month while wearing the
armbands, and to fill out questionnaires about how each session made them feel especially compared with running on the treadmill.
When the researchers analysed all of the resulting data, it was clear, Karelis said, that sex qualified as ‘moderate exercise,’ a 6-MET activity for men and 5.6-MET activity for women. That’s the equivalent, according to various estimates, of playing doubles tennis or walking uphill. The jogging, by comparison, was more strenuous, an 8.5-MET activity for the men in the study and 8.4 for women. (Though some men used more energy for brief periods during sex than they did jogging.) The sex also burned four calories per minute for men and three per minute for women, during sessions that ranged from 10 to 57 minutes, including foreplay.
Over all, the data reveal that “ sex can be considered, at times, a significant exercise,” Karelis said, worth encouraging in people who otherwise balk at working out. Ninety-eight percent of Karelis’s volunteers reported that sex felt more fun than jogging.
—©2013 The New York Times