Fans of abstinence had better be sitting down. 'Saving yourself' before the big game, the big business deal, the big hoedown or the big bake-off may indeed confer some moral benefit. But corporeally it does absolutely zip. There's no evidence it sharpens your competitive edge.
The best that modern science can say for sexual abstinence is that it's harmless when practiced in moderation. Having regular and enthusiastic sex, by contrast, confers a host of measurable physiological advantages, whether you're male or female. (This assumes that you are engaging in sex without contracting a sexually transmitted disease.) 
In one of the most credible studies correlating overall health with sexual frequency, Queens University in Belfast, Ireland, tracked the mortality of about 1,000 middle-aged men over the course of a decade. The study was designed to compare persons of comparable circumstances, age and health. Its findings, published in 1997 in the British Medical Journal, were that men who reported the highest frequency of orgasm enjoyed a death rate half that of the laggards.
While possession of a robust appetite for sex -- and the physical ability to gratify it -- may not always be a prescription for perfect health, a reluctance to engage can be a sign that something is seriously on the fritz, especially where the culprit is an infirm erection.
Dr J Francois Eid, a urologist with Weill Medical College of Cornell University and New York Presbyterian Hospital, observes that erectile dysfunction is an extension of the vascular system. A lethargic member may be telling you that you have diseased blood vessels elsewhere in your body. "It could be a first sign of hypertension or diabetes or increased cholesterol levels," Eid says. "It's a red flag that you should see your doctor."
Treatment and exercise, says Eid, can have things looking up again. "Men who exercise and have a good heart and low heart rate, and who are cardio-fit, have firmer erections," he says. "There very definitely is a relationship."
But is there such a thing as too much sex?
The answer, in purely physiological terms, is this: If you're female, probably not. If you're male? You betcha.
Dr Claire Bailey of England's University of Bristol says there is little or no risk of a woman's overdosing on sex. In fact, she says, regular sessions will not only firm a woman's tummy and buttocks but also improve her posture.
Dr George Winch Jr, an obstetrician/gynaecologist in Elko, Nevada, US, concurs. If a woman is pre-menopausal and otherwise healthy, says Winch, having an extraordinary amount of intercourse ought not to pose a problem. "I don't think women can have too much intercourse," he says, "so long as no sexually transmitted disease is introduced and there's not an inadvertent pregnancy. Sometimes you can have a lubrication problem. If you have that, there can be vaginal excoriation -- vaginal scrape."
Women who abstain from sex run some risks. In postmenopausal women, these include vaginal atrophy. Winch has a middle-aged patient of whom he says, "She hasn't had intercourse in three years. Just isn't interested. The opening of her vagina is narrowing from disuse. It's a condition that can lead to dysparenia, or pain associated with intercourse. I told her, 'Look, you'd better buy a vibrator or you're going to lose function there.' "
As for men, Eid says it's definitely possible to get too much of a good thing, now that drugs such as Viagra and Levitra have given men far more staying power than may actually be good for them.
The penis, says Eid, is wonderfully resilient. But everything has its limits. Penile tissues, if given too roistering or prolonged pummelling, can sustain damage. Or, in cases you'd just as soon not hear about, permanent damage.
"It is possible for a young man who is very forceful and who likes rough sex to damage his erectile tissue," Eid says. The drugs increase rigidity; moreover, they make it possible for a man to have second and third orgasms without having to wait out intermission.
"I see it in pro football players," says Eid. "They use Viagra because they're so sexually active. What they demand of their body is unreasonable. It's part of playing football: you play through the pain." This type of guy doesn't listen to his body. He takes a shot of cortisone and keeps on going. And they have sex in similar fashion."
There's a reason the penis, in its natural state, undergoes a period of flaccidity. That's when it takes a breather. The blood within it is replenished with oxygen.
"During an erection," explains Eid, "very little blood flows to the penis. During thrusting, pressure can go as high as 200 millilitres of water. Zero blood flows into penis at that time."
To absorb oxygen, the tissue must become relaxed. "If you do not allow the penis to rest," Eid says, "then the muscle tissue does not get enough oxygen. The individual gets prolonged erections, gets decreased oxygen to tissue and could potentially suffer priapism." (We recommend you get a medical encyclopedia and look it up.)
"The muscle becomes so engorged, it's painful," Eid says. "Pressure inside starts to increase. Cells start dying. More pressure and less blood flow. Eventually the muscle dies. Then there's scarring. That's why it's considered an emergency."
