Why Men Fall Asleep After Sex

Seven things most men don’t know about their sexual health.
By Laurie Pawlik-Kienlen for MSN Health & Fitness

Sex and sleep

According to Dr. Billy Goldberg, co-author of Why Do Men Fall Asleep After Sex?, there is little direct evidence explaining why men fall asleep. However, the chemicals oxytocin, prolactin, gamma amino butyric acid (GABA) and other hormones all contribute to “that roll-over-and-snore feeling” because they facilitate sleep.

“A man’s body chemistry changes after orgasm. The biochemical prolactin is released, physically altering his body and making him very tired,” says Dr. David McKenzie, a sex therapist in Vancouver, Canada.

Further, exertion during sex and after climax depletes the muscles of energy-producing glycogen, which leads to sleepiness. Since men have more muscle mass than women, they’re generally sleepier after sex.

Men’s libido goes up and down

Think PMS is only for women? Think again. Your monthly peaks and valleys are triggered by changes in testosterone that affect your mood, libido, energy level, beard growth and sperm count.

According to research by naturopathic physician Dr. Marcus Laux, men have more energy, a greater sense of well being, lower body weight and less need for sleep during the peak of their cycle. The valleys bring apathy, indifference and the tendency to magnify small problems into big ones.

“If you keep track of your personal cycles, whether it’s shifts in energy levels, mood or sex drive, you can anticipate changes,” says Laux. “Then, you can take advantage of the times you’re at your prime and better cope when you’re not feeling your best.”

Your penis is a barometer of overall health

Dr. Mehmet Oz, co-author of You: The Owner’s Manual, calls it your “dipstick” because it reveals the health of your other body parts. The physical mechanisms that send blood to your brain, heart and kidneys also inflate your penis. If it’s not standing tall, you may have arterial problems.

“A man’s lack of interest in sex is a big red flag that something is out of balance. Up to 25 percent of men have a low-to-no sex drive,” says Dr. Laux. “It could be even higher, as men don't talk about low libido.”

The possible causes of restricted blood flow include diabetes, endocrine disorders, heart and vascular problems or kidney diseases. “But,” says Laux, “don't rule out fatigue, psychological factors, relationship issues, poor nutrition, insomnia or lack of exercise.”

Disrupted sleep decreases erections

If you’re struggling with obstructive sleep apnea (OSA), you’re at risk for sexual dysfunction. OSA is a sleep disorder that affects 18 million Americans—many of whom go undiagnosed—and causes sufferers to stop breathing dozens of times per hour.

OSA disrupts rapid-eye-movement (REM) sleep, which is when men routinely experience erections. Decreased REM sleep means fewer REM erections, which affects sexual health. “It’s possible that men need to experience REM erections in order to maintain optimal sexual functioning,” says Dr. Charles Atwood, associate director of the University of Pittsburgh Medical Center's Sleep Medicine Center.

“If you have erectile dysfunction, you should get tested for OSA,” he advises. “Men who are diagnosed and treated for OSA often see an improvement in sexual functioning.”

Eco-friendly transportation could damage your testicles

Whether you’re bicycling to reduce your carbon footprint, save money on gas or get fit, make sure you’re cushioned properly. Cycling doesn’t cause male infertility, but it can lead to testicular damage, impaired sperm functioning and erectile problems. Urological surgeon Vinod Nargund from St. Bartholomew’s and Homerton Hospitals in London found that mountain bikers are more affected than road cyclists.

Dr. Nargund lists the potential problems of prolonged cycling: abrasions, chafing, damaged hair follicles and bruising. Sweating may cause skin problems and a general soreness.

Symptoms to watch for include genital numbness, erection problems and skin irritations. To stay healthy, wear shorts with protective padding. Make sure your seat is also padded, and adjust its position so it doesn’t put pressure on your groin.

Varicocele can cause male infertility

Infertility affects one in six couples, and male factors contribute to at least half of all cases. According to the Center of Reproductive Medicine at Cornell University, the most common identifiable cause of male infertility is varicocele, or enlarged veins in the scrotum. Another possibility is a blockage in the reproductive tract.

Simply being older also affects your fertility. Recent research from the Eylau Centre for Assisted Reproduction in France shows a connection between men over age 35, lower pregnancy rates and higher miscarriage rates. Keep your sperm strong by eating nutritiously, exercising regularly and decreasing your stress level.

Big news

An average penis length of 5 erect and 3 flaccid inches is normal for men—that’s significantly smaller than what most men think is normal.

“Generally, every man [and woman] believes the ultimate in sexiness and masculinity is to have a larger-than-average penis,” says sexologist Dr. Trina Read. “The fact is, men with large penises often find it difficult to find a partner who is comfortable having intercourse and giving oral sex.”

During intercourse, penis size has little to do with partner satisfaction. Most of the sensitive nerve endings are concentrated close to a woman’s vaginal opening—which means a penis of any size can be highly pleasurable.

“What most women really want is technique,” says Dr. Read. The upside? A man who masters his technique in bed may get away with falling asleep right after sex.