hi its not a n muscle as such as its blood that keeps it erect but if you go to www. pegym. com and click on penis exercises your find just doing some of then like jelqing and stretching will help you a lot chuck in some kegels and your away for life. but do follow what the tell you to do do go in blind read up it all first try reading down the forums as well. hope this helps your penis. good luck ps yes the more we use it the better it is and keeps erect but this is where you come in don't just let it sit there use it encourage him to the bedroom or what ever room you use but do try using all of them make sex fun as well as enjoyable time to keep his penis up.
a doctor told my husband that if you don't use you lose it that the penis is a muscle that needs exercise. true?