It is a popular locker room colloquialism that was considered by many to be an urban myth.
But scientists have found that some men do in fact fall into two categories when it comes to their penis size — ‘growers’ and ‘showers’.
The terms are used to define those who have large flaccid penises – showers – versus those whose members are less impressive naturally but grow significantly larger when erect – growers.
Spanish researchers have now drawn up a scientific definition to determine which group men fall into. It comes after a study found the average penis length has grown 25 percent in recent decades.
Scientists have put exact definitions of what it a grower and what is a shower in place. They found that a man whose flaccid penis grows 56 percent of more when getting an erection is a grower. If it grows 31 percent or less, then it is a shower. Around half of men fall within the middle area in-between, though, and are neither growers nor showers
The Spanish research team found that men whose penis grows more than 56 percent from when it is flaccid to erect are ‘growers’, while those who gain an extra 31 percent of their length or less are ‘showers’.
The average penis grows 42 percent when moving from flaccid to erect, with a majority of men falling into the gray area in-between both categories.
In total, 24 percent of men are growers while 25 percent are showers. The remaining 51 percent of men do not fall into either category.
Dr Manuel Alonso Isa, a urologist who led the research, told DailyMail.com: ‘Our study tried to give explanation to different types of penis when they get harder.
‘The purpose for our study is to give information to our patients for [length and growth] expectations before they choose surgery.’
He said many men are concerned about their penis size and hopes these findings will help doctors assure them they are fine.
‘As a urologist, we treat many patients who are concerned about their size… they want lengthening,’ he explained.
Penis enlargement surgeries have been trending upwards in recent years, with anecdotal reports of increases in demand appearing across America.
The most common type of penis enlargement is a ligamentolysis, where a ligament that connects your penis to the skeleton is cut – causing your member to hang lower.
Other procedures use fat from the stomach or even fillers to enlarge the penis.
These procedures do not come without risk, though. They can sometimes lead to erectile dysfunction or a loss in sensation on the penis.
In cases where the operation is botched, it could even lead to their being an odd bending or angling of the genitalia.
Dr Alonso Isa hopes many men that have a grower – a penis that is small while flaccid but greatly expands while erect – will see the concept now established in science and feel more comfortable with their length.
For the research, which will be presented at the European Association of Urology Congress in Milan, Italy, Dr Alonso Isa’s team gathered data from 225 men.
Each of them had their penis length and girth measured while flaccid and while erect.
They were given a prostaglandin injection, used to give a person an erection as a treatment for erectile dysfunction.
Researchers then compared penis lengths at flaccid and erect states for each participant.
The average penis in the study was 4.2inches long. When erect, it was 5.7inches. A typical man’s penis will grow around 42 percent when it reaches erection.
Dr Alonso Isa added that whether a person is a grower, shower or somewhere in the middle has no impact on their overall penile health or fertility.
‘We didn’t see any factors that predict any health impacts,’ he said.
But, there is a mental health impact to many men concerned about the size of their member, he said.
‘I think for mental health, it is smart for [doctors] to advise people their penis is normal [no matter if it is a grower or shower].’
He said further research on the topic should be into whether there are genetic – or other pre-determining factors – on whether a person is a grower or shower.