How is this not obvious to everyone?

Frequent sexual intercourse may cut down on a man's chances of developing erectile dysfunction, Finnish researchers report.

"This is the same as any other part of the body. It's what we in vascular surgery refer to as the 'use it or lose it' concept," said Dr. Hossein Sadeghi-Nejad, an associate professor of urology at UMDNJ New Jersey Medical School Hackensack University Medical Center. "Sexual activity will promote maintenance of normal erectile function down the line."

The heart works better when you force it to work harder through exercise.

Muscles get bigger and stronger by forcing them to adapt to the increased load placed on them.

Your lungs become stronger when you ask them to breathe deeper and more rapidly.

And your penis will respond more readily if you take it out and put it through its paces more often. Duh!

So the next time your girlfriend/wife/mother bust you for watching porn on your computer, simply tell her that you are exercising and you would appreciate some privacy. Actually if it is your wife or girlfriend you might even ask if she would be willing to spot you while you exercise.