The idea of abstinence before sport has been around since, well, sports were invented. The ancient Greeks believed in it. Muhammed Ali would reportedly abstain from sex for the six weeks before a big fight. But is there any truth to the idea? Science doesn't seem to think so.
One study took 14 married males, all former athletes, and had them perform a maximum strength grip test the morning after sex and after a six day period of abstinence. No significant difference was found. Another study took 10 fit, married men ages 18-45, and tested for "grip strength, balance, lateral movement, reaction time, aerobic power (stair-climbing exercise), and VO2max (treadmill test)" (VO2 max is a measure of the maximum volume of oxygen an athlete consumes during exercise).
Again, the results did not change due to sexual activity. And if you're worried about those bodybuilding forums and the know-it-all guy at the gym spouting their "facts" about ejaculation decreasing your testosterone levels, don't pay them much mind. Science has largely disproved this theory. In fact, in one very unscientific survey of 1,000 male and female runners by Brooks Running, 48 percent of respondents under 40 years old said that having sex before races helped their performance.
There's another vein of thought in this debate which focuses on the idea that sex burns valuable energy best saved for your competition or race the next day.
But as it turns out, unless you're going at it aggressively for hours on end, the energy you expend is pretty negligible. If you weigh 150lbs and get down for 15 minutes, you're only burning about 70 calories, the equivalent of climbing a few stories of stairs. Up the minutes to 45 and you're still only burning about 200 calories. Not negligible, but not much either.
It's not all about science, though. As anyone who pushes themselves to the limits at the gym knows, competition and performance is just as much mental as it is physical. Athletes who subscribe to the abstinence before competition theory often cite the belief that sex can sap one's aggression and motivation. As Marty Liquori, a U.S. Olympian in the 1500 meters in 1968 and the third ever American high schooler to break the four minute mile mark once said, "Sex makes you happy. Happy people do not run a 3:47 mile." The effect of sex on aggression was a key reason why Ali would abstain, too.
In the end, the theory of abstaining may be rooted more in the idea of chasing sex before a competition than in having some quick coitus before laying down to sleep. Leave it to Casey Stengel, the legendary New York Yankees manager from 1949-1960 (the Yanks won seven World Series championships during his tenure), to possibly sum up the debate better than any scientific study or research paper ever could. "It's not the sex that wrecks these guys," said Stengel. "It's staying up all night looking for it."