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How an Erection Works

***click on underlined links to access PubMed abstracts***

Penile physiology/biochemistry: NO means yes!

Nitric oxide (NO) is the most important factor increasing blood flow into the penis to cause engorgement. Sexual arousal activates the production of NO in the penile nerves. There it activates release of cyclic GMP, which causes the smooth muscle surrounding the penile arteries to relax.The result is a very large increase in blood flow, giving the man that "turned on" feeling. Lou Ignarro, a UCLA PhD who shared the Nobel Prize in Medicine in 1998 for the discovery of NO and its role in the erectile response, has co-authored 4 of our reviews and wrote the forword for our book, saying "I have no doubt that this book will help millions of couples around the world by improving male sexual performance".

Distension and rigidity of the penis also depend on factors that limit outflow of blood. As with a fire hose, if there was no nozzle to limit outflow, the hose would remain limp. However, the penile veins are strategically placed within and adjacent to the fibrous sheath that surrounds the penis. The distention caused by the large inflow of blood together with the surrounding pelvic floor muscles are therefore able to markedly constrict outflow of blood. The pelvic floor muscles also put direct pressure on the penile sheath resulting in elevations of pressure within the penis that can be much greater than in the inflowing blood, resulting in maximum erection hardness.(Meldrum, 2014)

Inflow of Blood

A very large increase of blood flow into the penis is absolutely necessary for an adequate erection to occur. We can't emphasize enough the importance of sexual arousal in stimulating the production of nitric oxide (NO) in the penile nerves and thereby inflow of blood. However, that topic is clearly an extensive one which we can’t cover here. We suggest couples access the Sinclair Institute’s website to explore that in more detail.

Once NO is sufficiently activated in the penile nerve endings, levels must be high enough and last long enough to relax the penile arteries to carry a large amount of blood into the penis. That in turn causes engorgement to initiate the erection as well as to put pressure on the penile veins to restrict outflow (covered below). NO is actually a gas, which lasts only a few seconds before being rapidly broken down. It’s startling that the survival of our species relies on such a delicate substance, but fortunately, the body has very effective antioxidant systems that counteract NO breakdown for a lasting effect on blood flow. Unfortunately, average levels of a principal circulating antioxidant, Pon-1, and of a principal tissue antioxidant, glutathione, are decreased in men with low erectile function (erectile dysfunction, ED). In a well-designed study, pycnogenol, a fully characterized commercial preparation of antioxidants like in blueberries, was shown to markedly improve erectile function scoring by the study participants. Also, chocolate (cocoa), a very potent antioxidant, markedly stimulates NO levels, even in young, healthy men. These findings together show how critical antioxidants are for maintaining NO levels and action and suggest that antioxidants may also maximize erectile function in men without ED. We will discuss how to keep your antioxidant levels high in the page “lifestyle and erectile quality”, and a listing of great antioxidants is to the right of every page. Neural NO release is also prolonged by a Cyclic-AMP mediated mechanism. Cafeine stimulates Cyclic-AMP levels, so a cup of coffee after a romantic dinner may help with later evening pleasures!

Here’s where the Viagra-like drugs enter the scene. NO acts to cause relaxation of muscle in the wall of the penile arteries and the tissue within the penis itself through an intermediate substance called Cyclic GMP (Rajfer J, 1992). These drugs act to block the biochemical pathway (phosphodiesterase 5, PDE-5) that breaks down Cyclic GMP, thereby raising cyclic GMP levels. These “PDE-5 inhibitors” work reasonably well for many men but remember they will not work if there is very little NO passing from where it is produced (in the blood vessel lining) into the surrounding muscle. Also, it is very important for your health to have lots of NO (see the “Erections and Health” page.

The pressure of the blood entering the penile arteries is a factor, but don’t be fooled. It is actually the exact opposite of what you might think. In someone who has higher blood pressure, blood vessels are constricted, which lowers the flow of blood into the penis. In men with high blood pressure the chance of having ED is 2-3 times higher (Doumas M, 2006). Of course the pressure of blood flowing into the penis can’t be higher than the pressure in the man’s circulation. Because pressures up to 2-4 times peak circulation pressure have been measured in young healthy men (Lavoisier, 1986), that clearly shows that something else determines maximum erection hardness (see “Outflow of Blood”/pelvic floor exercises below.

On the “lifestyle and erectile quality” page we will discuss other factors that can increase or decrease NO and inflow of blood.

Outflow of Blood

If there is no nozzle on a fire hose, the hose will remain limp in spite of a large amount of water flowing through it. Likewise, if the penile veins are wide open, erection will not occur. The “nozzle” for the penis is created by the penile veins being constricted as they pass through and next to the tough fibrous sheath surrounding the penis, both by the pressure of blood distending the penis, but also by pressure and contractions from the surrounding pelvic floor muscles. In a remarkably well-structured study of pelvic floor exercises (PFE’s) (Dorey, 2004 and 2005), 40% of men had their ED resolve and in another 35% it was improved. Their sexual partners experienced increased satisfaction and desire (Dorey, 2004). The benefits were of a similar magnitude compared to those of Viagra. However, the benefits of Viagra-like drugs and PFE's aren’t competitive. They work on entirely different aspects of erectile function and would at a minimum add together to promote better erectile quality. More than that, there are men whose decreased erectile function will have an inadequate response to Viagra and other PDE-5 inhibitors because the penile veins are too open, and men who will not respond to PFE’s because of insufficient inflow of blood. Erectile fuction will be maximized and for the highest percentage of men by combining efforts to both increase inflow and decrease outflow. (Meldrum, 2014) It is not surprising that erection hardness is an excellent predictor for men to continue use of one of the Viagra-like drugs. (Mazzola, 2013)

The pelvic floor muscles are not only important in constricting outflow of blood, but they also exert pressure on the penis by surrounding and being attached to the penile sheath. That is why pressure in the penis in healthy young men has been measured at levels 2-4 times higher than the peak pressure of the inflowing blood. Contractions of those muscles are stimulated by distention of the penis and by pressure on the end of the penis (the “glans penis”) (Lavoisier P, 1986) (Shafik A, 2006). Therefore, coital thrusting further increases penile hardness, provided that the pelvic floor muscles are sufficiently developed. PFE’s are described in detail online by the British researcher who led the above study.

So what do I do to get "George" maxed out?

First, do everything you can to increase NO in your blood vessels and penis, further described in the page "Lifestyle and erectile quality". The real bonus is that increasing NO by the ways we describe will also increase your general health and your "healthspan" (the number of extra years of healthy life).

Second, maximize the strength of your pelvic floor muscles throughout each day by doing the PFE's while standing, sitting, walking and lying down. If you practice them while doing other activities they will take no more time from your day and no one will know you are doing them. For example, do them while standing shaving in the morning, while standing or sitting in front of your computer screen or in your car at a stop light, while doing your daily exercise, and while lying on your back in bed or when exercising at the gym. It is particularly important when walking, as a study showed walking was associated with decreased pelvic floor strength (Sousa LE, 2018). That is likely because the natural tendency is to relax those muscles when walking. 

Third, be sure to also read our book survival of the firmestcalled "Survival of the Firmest", available at Amazon/kindle or itunes or for download below. You will find more information there and on some topics not covered here. Even for the same material it may be explained in a different way that you may find easier to understand and it describes 10 steps toward better erections. Above all, carefully read chapter 8, which may save you half of your net worth, heartbreak for many loved ones and friends, and numerous complications in your life.

Buy Now "Survival Of The Firmest" $9.99

Stress and erectile performance

Stress is certainly a factor. stress All men have come to realize that stress is a non-starter for developing an adequate erection. Stress activates nerves that constrict blood flow, the exact opposite of what is required for distention of the penis with blood. The role of stress is too complex a topic to cover here. It may require simply taking on fewer tasks, or it may require visiting a psychologist for therapy. Yoga, meditation, and other forms of relaxation therapy may be helpful. If stress is a factor, you will want to maximize all of the factors we outine in this website and in our book.

How about my partner?

It is very likely if you do all of the things recommended here and in our book, your erections, sexual enjoyment and desire will markedly improve. Studies have shown that improved erectile function results in marked increases in female sexual function and satisfaction. (Cayan, 2004)) It may be difficult for any man to know how good he is at this, but one thing you will both know for sure is when he is better! And you will be less likely to develop erectile dysfunction and vascular diseases as you get older.  Now that’s a no-brainer.

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Great antioxidants:








Green tea

Dark chocolate

--low sugar



--particularly cooked


--e.g. ginger, oregano, tumeric, cumin