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The biking and damage to the male organ, with a new twist.(14 posts)
 The biking and damage to the male organ, with a new twist.  onespeed Dec 2, 2002 8:31 AM   Mountain biking found to harm scrotum
CHICAGO (Reuters)  Men who log 3,000 miles or more a year on their mountain bikes suffer scrotal damage that could reduce their fertility, a study has found.
The report, based on examinations of 40 "extreme" bikers and 35 noncyclists, suggests that men who spend the most time on their bikes should invest in shock absorbers and suspension systems that could double the cost of a standard mountain bike, the study said on Monday.
Scrotal examinations of the bikers found that 88 percent had cysts, calcification, varicose veins and other abnormalities compared to 26 percent of the nonbiking group.
Sperm samples showed that the extreme bikers had a count that was only a third that of the noncyclists while bikers' sperm had less motility or movement than nonbikers.
"We believe that extreme mountain biking results in semen alteration, which may have an impact on fertility," said lead author Ferdinand Frauscher of University Hospital in Innsbruck, Austria.
"We believe that repeated mechanical trauma to the testicles results in some degree of vascular damage and may thereby cause a reduction in sperm motility," he said.
His report was released at the annual meeting of the Radiological Society of North America. 
 Loss of fertility is a GOOD thing; impotence is the problem  cory Dec 2, 2002 8:36 AM   Of course I already have my two kids, but you could make a pretty good argument that anything that reduces the birth rate has a positive side. There are a lot of people having kids who don't have any idea what to do with them once they bring them home. 
 A sampling of 40 cyclists and 35 noncyclists...  No_sprint Dec 2, 2002 8:45 AM   Those numbers are so very small that they are truly meaningless. This person doesn't have any knowledge of statistical analysis whatsoever. 
 statistical significance = size of effect * size of study  KenS Dec 2, 2002 11:10 AM   The phrase in the title is the mantra of Robert Rosenthal, a wellknown statistician. Adequate sample size depends on the size of the effect. If the effect is large then you don't need many subjects. 
 True, but...  PsyDoc Dec 2, 2002 11:56 AM   ...when you are dealing with a relatively new finding, then one does not know whether one has adequate power or whether the results could be a Type I error. Also, "number of participants" is just one component that impacts experimental power as you could have 1,000 participants (HUGE power) and then use substandard procedures, materials, underqualified experimenters, etc. and make a Type I error. 
 Confused Type I and Type II error  KenS Dec 3, 2002 6:10 AM   A Type I error occurs when one rejects the null (no difference) hypothesis when the null hypothesis is true. Since this study reported there was a difference, the null hypothesis was rejected and a Type I error may have occurred. Power is connected to a Type II error, which occurs when one *fails* to reject the null hypothesis when it is false. An increase in the power of a test means that one is less likely to make a Type II error. In other words, an increase in power means that one is less likely to fail to reject the null. Since the authors reported a significant difference, power is not an issue here. 
 Wait a minute...  PsyDoc Dec 6, 2002 5:31 AM   So, if they report a significant difference, then isn't it is still possible that power is an issue. For example, with such a small sample size (according to the power charts, alpha set at .05 for a medium effect, they would need ~50 per group for a mean comparison...which is what they did), they still could have obtained a significant difference due to random fluctuations not associated with a "true" difference. Additionally, they are using an sample with extreme characteristics (extreme moutain bikers) during a particular time of the year. The use of such a sample threatens the internal validity of the study (statistical regression aka regression toward the mean). 
 We know the answer...  Eager Beagle Dec 2, 2002 9:14 AM   http://www.moonsaddle.com/specs.htm 
 "extreme" cyclist ???  PaulCL Dec 2, 2002 9:37 AM   What is an "extreme" cyclist??
Is it someone who puts on over 3000 miles per year?
Is it only a MTB ride with 3000 miles??
Is it a MTB rider who loves to do big jumps,hence, squishing 'the boys'?
The sampling is so small....but then again, I'm in denial.
Paul 
 riders that drink mountain dew  collinsc Dec 2, 2002 9:53 AM   what was that talk about yellow 5 again? 
 re: The biking and damage to the male organ, with a new twist.  BikeViking Dec 2, 2002 12:39 PM   DOn't care if they're blanks, just as long as the "hydraulics" are working!!! 
 using the words male organ and twist in the same sentence...  Frith Dec 2, 2002 1:31 PM   ouch. 
 Selection bias  jtlmd Dec 3, 2002 7:49 PM   This data may not be applicable to most of us. How many of you actually ride more that 2 hours a day for 6 days a week? The study suffers from a selection bias and the result may not be applicable to the general population.
The author didn't publish the study in a peer reviewed journal yet. It was presented at a conference. I'll wait until I see it published. 
 Selection bias...  PsyDoc Dec 6, 2002 5:37 AM   ...typically results when the participants selfselect themselves into the group(s) of an experiment. This is a threat to internal validity whenever participants are not selected randomly, which might be the case with this study. With such a study, you also have to deal with regression toward the mean due to the extreme characteristics of the sample as jtlmd points out. The results of this study will generalize only to other "extreme mountain bikers" who ride/train with the same schedule. I am also interested to see if this study makes it into a peerreviewed journal. 
 

