Influence of bicycle seat pressure on compression of the perineum: a MRI analysis.

It is a common belief that bicycle seat pressure compresses neurovascular tissues in the perineum and may lead to perineal and penile pathologies in male cyclists. The purpose of this study was to examine the effect bicycle seat pressure has on compression of the perineal cavernous spaces, which house the penile neurovascular tissues. A second purpose was to identify where peak cavernous compression occurs in relation to a bicycle seat. Five males were assessed for compression of the corpus spongiosum and corpora cavernosa with and without bicycle seat pressure using MRI. Seat pressure was applied using a custom loading device designed to replicate seat pressure recorded during stationary bicycling. The distance between a horizontal midline of the seat and the point of peak cavernous space compression was made on sagittal plane images. Diameter measurements of the cavernous spaces at the point of peak compression were made on coronal plane images. Results revealed that peak cavernous space compression occurred below the pubic symphysis, 40.7(+/-11.4) mm anterior to the midline of the seat. Corpus spongiosum values in the unloaded condition were 148% greater than the loaded condition (p=0.008). Similarly, the left and right corpora cavernosa values for the unloaded condition were 252% and 232% greater, respectively, than the loaded condition (p=0.02-0.03). Cavernous spaces that house penile arteries and nerves were compressed maximally below the pubic symphysis. Because this location of peak compression was not different between subjects, it may be a universal impingement zone that limits blood flow and neural activity to and from the penis. This information can be used to optimize seat design and thus reduce perineal injuries.