Actually, the studies done on this subject support your current uro's
position...ron

Clin Chem Lab Med. 2004 Mar;42(3):347-9

Long-distance mountain biking does not disturb the measurement of
total, free or complexed prostate-specific antigen in healthy men.

Herrmann M, Scharhag J, Sand-Hill M, Kindermann W, Herrmann W.

Department of Clinical Chemistry, University Hospital of Saarland,
Homburg/Saar, Germany.

PURPOSE: Mechanical manipulation of the prostate is a generally
accepted interfering factor for the measurement of prostate-specific
antigen (PSA). However, only few studies have focused on common daily
mechanical manipulations, such as bicycle riding. Furthermore,
physical exercise is also supposed to modulate PSA serum
concentration. Long-distance mountain biking is an excellent model to
study the combined effect of mechanical prostate manipulation by
bicycle riding and strenuous endurance exercise on total, free and
complexed PSA (tPSA, fPSA, cPSA).
MATERIALS AND METHODS: We investigated tPSA, fPSA and cPSA in 42
healthy male cyclists (mean age 35+/-6 years) before and after a 120
km off-road mountain bike race. Blood sampling was done before, 15 min
and 3 h after the race.
RESULTS: Mean race time was 342+/-65 min. All athletes had normal
serum levels of tPSA, fPSA or cPSA. None of these parameters was
modified by the race.
CONCLUSIONS: In healthy men the measurement of tPSA, fPSA and cPSA is
not disturbed by preceding long distance mountain biking or endurance
exercise. Based on the present data, there is no evidence for a
recommendation to limit bicycle riding or physical activity before the
measurement of tPSA, fPSA or cPSA.

Bicycle riding has no important impact on total and free prostate-
specific antigen serum levels in older men.
Luboldt HJ,  et al. Urology. 2003 Jun;61(6):1177-80.

Johns Hopkins Postate Bulletin 04/07/04

http://www.hopkinsprostate.com/html/GrandRounds/2003/gr1003_07.html

Bicycling And BPH

Q. My query concerns something my wife has been badgering me about for
the past year. I have what I consider to be moderate BPH. I’m 46 and
have to get up to go to the bathroom about twice a night, and have
been doing so for the past two years. I tried saw palmetto but that
didn’t reduce my bathroom frequency at all. My wife thinks that my
urination problems are caused by my bike riding and says I should
switch to swimming. Armchair doctor that she is, she thinks that
sitting so long on my small, hard bike seat has somehow aggravated my
prostate and caused my problems. What do you think? For the past
decade, I have been riding well over 150 miles a week, and each year I
ride several "centuries" with my friends, which are one-day, non-stop
100-mile rides. I tell her that age is causing my problems, not
cycling. Your thoughts, please. Atlanta, GA

A. There are some data to suggest that cycling does not traumatize the
prostate. In a study done after a four-day, 250-mile bicycle race,
there was no significant increase in PSA when compared to the PSA
before the race began. PSA is a sensitive marker of prostate trauma,
and if cycling caused prostate trauma, one would have expected to see
an increase in the PSA.

Even with heavy bicycle riding, I would consider a 2.6 between to scores
less than 1.0 to be an anomaly; more likely a lab problem than a uro
problem.

Well, as a long time cyclist I have a slightly different take on this
subject.

On one hand I've read the studies and understand what they say about
what I would call the theory of physically induced greater PSA due to
pressure.  Meaning all that bouncing around and sitting on the bicycle
seat pushing on the prostate.

But looking at it from another point of view I think there may, in
some men, be a possible way in which cycling can induce a higher PSA
score.
That way would not be from direct and immediate causation during
recent rides, but rather from a much longer term aggravation of the
prostate and associated areas.   Meaning a cycling induced chronic,
though possibly asymptomatic,  case of prostatitis.

In my case I had a feeling that my cycling might be having an effect
after getting my first PSA in 5.3 years only to have it jump up to 2.9
from the prior .8 reading.
6 months later, and after taking 20 days off the bike while visiting
friends in Hawaii,   I retested and it was 1.6.
I might add,  that laying off the bike seemed like it allowed a slight
prostatitis urgency to subside.

Now, as I'm sure some will say,  that slight urgency could have come
and gone for reasons other than cycling.   True, and of course I'm a
case study of one.   Also between the 2.9 and the 1.6 tests I also
made other dietary changes...
In subsequent tests I allow myself a several days off the bike 5-7
before drawing blood.

All I can say is that as a longer term cyclist doing well over 100
miles per week,  I just have this hunch that the extra cycling might
well induce a bit of prostatitis with only minor to nil symptoms, and
yet capable of bumping up a PSA result by 1 or 2 points.

I could be completely wrong about that chain of events connection to a
higher PSA.

Still,  before my next PSA test I'll probably take 5 to 7 days
off.....and for other reasons my current biking is only about 70 miles
a week with the rides being 3 x 23 mile loops.....all rather quickly
done so no long lingering on the saddle.....and also full of climbing
so I am out of the saddle more often.

OK........thats my longer term,  non-immediate pressure theory, of how
cycling might give a higher than normal PSA reading