If there's one thing that almost every guy is an expert at, it's masturbation. After years of extensive, hands-on experience, you think you know everything there is to know. But according to the experts, maybe you don't. Here are some that may surprise you. 1. Masturbation doesn't have the health benefits that sex does. "It appears that not all orgasms are created equally," says Tobias S. Köhler, MD, MPH, an associate professor at Southern Illinois University School of Medicine in Springfield. Study after study shows that intercourse has all sorts of benefits for men -- for your blood pressure, heart and prostate health, pain, and more. You'd think that masturbation would, too. But it doesn't. Why would it make a difference whether you ejaculate during sex or on your own? No one's sure. But your body seems to respond differently. Even the makeup of semen is different if you masturbate instead of having sex. Still, does it really matter? Have you honestly been masturbating all these years only because you wanted to boost your prostate health? Didn't think so. But one study, Harvard’s Health Professional Followup, showed that Masturbation may help lower risk of prostate cancer. 2. Masturbation is not risk-free. Sure, it's low-risk. It's the safest form of sex possible. No one ever caught an STD from themselves or made themselves pregnant. But like other low-risk activities (chewing, walking), it still has some risks. Frequent or rough masturbation can cause minor skin irritation. Forcefully bending an erect penis can rupture the chambers that fill with blood, a rare but gruesome condition called penile fracture. Köhler has seen guys with it after vigorous masturbation. "Afterward, the penis looks like an eggplant," he says. "It's purple and swollen." Most men need surgery to repair it. 3. There's no "normal" amount of masturbation. Guys can get hung up on whether they masturbate too much. But it's not how many times you masturbate in a week (or day) that really matters, says Logan Levkoff, PhD, a sexologist and sex educator. It's how it fits into your life. If you masturbate many times a day and have a healthy, satisfying life, good for you. But if you masturbate many times a day and you're missing work or giving up on sex with your partner because of it, consider seeing a sex therapist. Even then, there's nothing specific about masturbation that's the problem. Compulsive masturbation is like any behavior that disrupts your life -- whether it's compulsively playing poker or checking your social media every other minute. SUGGESTED 4. Masturbating doesn't reflect on your relationship. Levkoff says the most damaging myth about male masturbation is that it's a sign something is wrong in your relationship. The fact is that most guys masturbate. They masturbate if they're single, in a bad relationship, or in a great relationship. It's just something they do that has nothing to do with their partners. Masturbation isn't only about sex, Levkoff says. For many, it's a routine way of relieving stress, clearing your head before work, or going to sleep. 5. Masturbation is almost certainly good for your sex life. Masturbation can help your sex life, since it's how guys learn what they like during sex. "I think women would be more satisfied sexually in their relationships if they masturbated as much as men do," Levkoff says. Are there exceptions? Some guys do get so hooked on a certain amount of pressure during masturbation or the stimulation of porn that they can't perform with a partner, says Ian Kerner, PhD, a sex therapist and author of She Comes First. Still, Kerner says those guys are the exception. "For the vast majority of men, masturbation is a healthy thing," he says. "I'm usually more concerned about a guy who's stopped masturbating -- which can be a sign of anxiety or health problems -- than a guy who's doing it regularly."