from the keep-dancing-on-the-pedals departmentThis article appeared in the pages of Cycle, the membership magazine of the CTC, almost ten years ago. It doesn't seem to be easily available online there, and it's still useful, so I'm pasting it here for those in need.
When I confessed to my own saddle problems in the rather public forum of the London Cyclist ten years ago, I certainly discovered one thing: cyclists' bottom problems are a taboo area. There were lots of giggles for a few months after publication, which fortunately the dignity of my profession enabled me rise above them. The article also proffered the anecdote of my own resolution of the problem--a couple of boils on the perineum. Round town I switched from gel to sprung leather, and, on long distance rides, adopted a recumbent. Result: no more problems.
The part of the body that relates to the saddle on a conventional machine is technically termed the perineum. Now, most animals are quadrupeds, and their perineum has less to do, being vertically inclined and acting as the side, rather than the base of the bucket. But humans' upright stance makes the pelvic outlet (as it is known) an insoluble conflict between ease of labour in childbirth and mechanical efficiency when walking on two legs.
The umbrella of muscles suspended from the inside of the pelvis and sacrum collectively is known as the pelvic floor. In men its only defect is the anus, but woman need the space of the birth canal too. Hence, as is widely understood, the adult female's broader girth about the hips, on average, than males.
This fact of nature—the distance between the ischial tuberosities that form the lateral bony boundary of the pelvic outlet—is an important variable in saddle selection. Best bought in person, grasp the demonstration model in the shop, and bring it firmly into alignment with the your ischial tuberosities there and then. Any saddle whose widest part is narrower than this distance runs the risk of inflicting pressure injuries potentially deeper than the skin, as the right and left perineal blood vessels and nerves course forward to the genitalia close to the midline. The anus is also in the midline, but its internal and external sphincters are reasonably robust to saddle trauma.
Out of the shop, saddle correctly fitted, the most obvious saddle injury, instantly painful, is an unexpected blow from an unyielding saddle on an unsprung bike. Unexpected road surfaces--I speak of potholes--can result in a stiff biff where the sun don't shine that is rarely appreciated if unanticipated. Usually the pain settles in a few minutes and the damage is minor, but you certainly don't do it for fun.
More insidious but with the same disastrous potential as a direct hit, is damage caused by lack of blood flow when the pressure of the saddle exceeds the pressure in the blood vessels. The circulation of the skin and pelvic floor muscles is rarely a problem in young adults of either sex, but older riders may start to notice problems, with the first symptom noticeably slower recovery and healing times after longer rides.
The perineal skin can suffer local infection at any time, though it is more likely in summer or warmer climes, when the increased transpiration of moisture from the sweat glands encourages yeasty organisms such as Candida, and mechanical problems such as chafing and maceration of damp skin. If you're prone to a spot of groin rot over the summer months it's probably safe to suggest a strategy of a couple of days of rest off the bike, preferably in a sarong rather than a pair of Y-fronts, and the application of a little clotrimazole cream twice a day, while nature runs its course. Hint: a small folding mirror and a good light can be very helpful when monitoring the progress of your perineum through the course of its cycling career.
There's much more that could be said of course, but do so would require longer than the editor allows: consult your doctor if symptoms persist.
Among cyclists who really know about these matters: the randonneurs and racers of this world, opinion divides on both prevention and treatment of perineal problems, but on one fact all will agree: if you're not dancing in the pedals, you are already finished. As to the merits of padded shorts, the application of pre- and post- ride ungents (such as Vaseline), or specially-shaped saddles (once the basic requirement of physical fit has been satisfied), none agree, as you would expect from the ruggedly individualistic body of cyclists.