Apparently there is some form of correlation between both riding (cycling) and general exercise (non cycling) and slightly elevated PSA levels, especially for those that log 3+ rides or more per week at an hour or more per ride.
There isn't much documentation available however. The LS website mentions the relationship. Cycling (frequency and duration) seems to be indicated factors, moreso than general exercise. The relationship is so poorly understood/medically documented that the general preparation instructions for the blood test do not caution/advise against engaging in activity that can raise the PSA level.
If you are of the age that a PSA test is part of your periodic health regimen, it might be appropriate to discuss with your physician whether you may need to temporarily suspend your riding for 2 - 3 days before your blood test. Might prevent an unneeded biopsy.
I am in search of the documentation... if it exists.