Saddles -- and their potential for causing crotch crises -- always receive lots of attention.
It could be argued that the search for the ultimate saddle design is the Holy Grail of cycling research, considering that almost every rider suffers pressure, chafing and even saddle sores at some time during his or her career. There's a reason why most experienced riders have a box of old saddles in the garage, discarded in the ongoing search for a comfortable seat.
But it's not just comfort that's at stake here. Saddle pressure has been implicated in impotence in male cyclists and perineal pain and numbness in female riders.
Can science tell you the ideal saddle to buy, a saddle that disappears under you and feels as comfortable after a 6-hour century as in the first 15 minutes of use?
You'd think that the perfect saddle design would have been standardized by now. In the last 10-20 years, researchers have had access to advanced methods of studying perineal blood flow. They can trace pelvic motion precisely using 3D motion analysis equipment. But standardization isn't the case. In fact, there are more saddle designs, and more controversy, than ever. No consensus has been reached.
For example, a 2003 study examined 20 female cyclists riding standard, cutout and noseless saddles to see if moving the hands from the top of the brake levers to the handlebar drops increased the pelvis's forward tilt and, thus, the pressure on soft tissue. The study found that these subjects had an average of a 16-degree pelvic tilt while riding on the lever hoods, and it increased to an average of 29 degrees while riding in the drops.
The pelvic tilt was slightly greater while riding noseless and cutout saddles compared to the standard saddle. This implies that these unorthodox saddles, designed to reduce soft-tissue pressure, may not work well. Even assuming that the cutout or the noseless design lessens perineal pressure, that advantage is probably lost when the rider moves to the drops because the pelvis tilts forward more than it would with a standard saddle design, increasing saddle pressure.
Another problem when setting up studies is determining exactly what the body does during pedaling. This is surprisingly difficult even with modern 3D motion-analysis equipment. This technology uses reflective dots stuck to the skin directly on top of bony anatomical landmarks such as the tibial tuberosity below the kneecap or various areas on the crest of the hip bones.
But it's difficult to make markers on the skin correspond accurately to the underlying bony structures. For example, even if the technician accurately places the reflective dot over an anatomical landmark -- say, the greater trochanter on the side of the hip -- the skin moves over the bone during the pedaling motion. As a result, in some cases the marker moves more than the bone, leading to faulty conclusions.
One subject went to heroic lengths to remedy this situation. In a 1995 study, a 45-year-old male competitor allowed researchers to pierce his skin and install intracortical bone pins. That's as gruesome as it sounds -- pins inserted through the skin and directly into the bone. This remedied the problem of the markers moving during the pedaling motion but it couldn't have been much fun for the subject. Anything for science!
This painful study showed that the marker in the bone moved much less than a marker attached to the skin, demonstrating that previous, less intrusive studies may have been flawed. The hip tilted forward and down about 10 mm during the pedal downstroke, a movement that can contribute to saddle chafing and pressure. But far from being a disadvantage to performance, researchers concluded, that movement actually facilitated power transfer from the upper to the lower body, resulting in a more powerful pedal stroke.
Another attempt to see what happens when men and women pedal was undertaken by Darryl Thelen Ph.D. and Heidi Ploeg Ph.D. from the Department of Mechanical and Biomechanical Engineering at the University of Wisconsin-Madison. They recruited 12 male and 14 female cyclists to ride in their preferred positions on the test bike using 170-mm crankarms and a cadence of 90 rpm. Resistances were set to require 100, 150 and 200 watts. The test saddle used was unmarked but was a standard shape (photo). Each subject was checked for flexibility. A complete 3D analysis was done and saddle pressure was measured using the most advanced equipment.
The findings, while not leading to the "ultimate saddle," are interesting nonetheless. They represent what is currently known about the fraught marriage between the crotch and the saddle during the pedaling motion.
Thelen and Ploeg found that, contrary to popular belief, cyclists don't sit on the saddle in such a way that weight is borne by the ischial tuberosities ("sit bones"), those bony protuberances that press against the cement if you sit on a curb. Instead weight is borne on the rami or inside slopes of the arch-shaped area between the sit bones.
To visualize this distinction think of the sit bones as the points of an inverted V. But even this isn't entirely accurate because males, the researchers point out, have a triangular pubic arch while females have a more rounded arch. Another gender difference: female sit bones are about 20-mm wider on average than male sit bones. And males have more lumbar flexibility than women so they don't need to tilt their pelvis as far forward to get their backs equally flat. These findings seem to point to the wisdom of gender-specific saddle designs.
But one size (or design) doesn't fit all males or all females because of wide individual differences in the size and shape of the pelvic arch. Ploeg and Thelen's study found that in order to support weight in the appropriate place on the rami, cyclists tend to move forward to the narrower part of the saddle if they have a relatively narrow space between their sit bones. If the gap is wider they slide back to the wider, rear section of the saddle.
In other words, riders automatically move on the saddle in order to support pressure in the most comfortable way. Even if a saddle is designed to support the sit bones, riders move until their weight is supported inboard of the sit bones on the rami. This implies (but in no way proves) that saddles designed to support the sit bones may not work because the body will move forward to a narrower part of the saddle regardless of the designer's intentions.
The University of Wisconsin-Madison study also shows that riders move around during the pedal stroke. This is one reason that raw skin and saddle sores develop. The friction produced by this movement eventually abrades the skin.
Ploeg and Thelen measured a 2-degree pelvic tilt at the bottom of the pedal stroke along with 3 degrees of axial rotation. Picture the perineal area grinding and rotating on each pedal stroke. This isn't a pretty picture, but like previous studies have indicated, Ploeg and Thelen found that the pelvic motion during pedal strokes helps transfer power between each leg and from the upper body to the legs.
Demonstrating once again the difficulty of getting solid data, these tilt and rotation figures were slightly higher for female cyclists than for males at the highest power output of 200 watts, but that finding may be flawed by the fact that 200 watts probably represented a higher percent of maximum power for the women than for the men.
An earlier study showed that saddle pressure decreased as power increased because harder pedaling tended to levitate the rider slightly off the saddle. But regardless of wattage, female cyclists had less overall pressure on the saddle than males because the women in the study weighed less.
So what did Ploeg and Thelen discover about saddle shape? What sort of saddle works best?
It appears that preferred saddle shape is as individual as each rider's anatomy, pedaling style, body weight and position on the bike. The saddle that is comfortable for one rider may be supremely uncomfortable for another.
In the question-and-answer period following the presentation, Ploeg, who is an active rider and competitor, was asked what saddle she had settled on after viewing the results of her research.
Her answer: "I'm still looking."
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