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The four and a half rules of road saddles
What should I look for in a saddle? How do I find one that fits me and is comfortable?
Each season Cervélo runs various projects to learn more about maximizing performance of the riders and their machines. We've worked like this from the very first Cervélo pro sponsorships, and what we learn by working with pros goes into every new Cervélo.
Saddle research is important to every cyclist. The relating discomfort isn't often talked about, possibly because it involves areas of the anatomy that aren't discussed in polite company. Nevertheless, as one of the three contact points between the bike and the rider the saddle can ruin your riding experience if it's uncomfortable.
Mapping the pressure distribution on the saddle is one tool we can use to learn about saddle discomfort. But a pressure map is not a pain map; some body parts can take the pressure, while other body parts are more sensitive. What this means is that equalizing the pressure everywhere isn't the best solution. Nevertheless, a pressure map can teach athletes, coaches and product designers a lot.
That’s why we brought a Gebiomized pressure measurement system to Team Garmin’s 2012 winter training camp in Mallorca, Spain.
The instrumented saddle cover contained pressure sensors. The rider wore a transmitter and data was displayed and recorded on a laptop in the team car following behind. In the test, riders changed hand position when the Directeur Sportif honked the car's horn.
The resulting pressure map (above) showed high pressure on the saddle nose, under the athlete's pubic bone. This is a typical pressure distribution for male pros, but rarely occurs in female pros. It's not painful for many men, but can be very painful for many women. It's unhealthy for both.
This pressure map shows peak pressure on the left and right sides. The ischia, albeit a centimeter or two medial to the tuberosities, are supporting the most weight here, and the low pressure in the middle is the benefit. This is typical of many women pros and is considered a healthier pressure distribution on the saddle. Based on research in the lab and on the road, along with valuable feedback from athletes, we developed the four and a half rules for selecting a road saddle.
First, some disclaimers: The four and a half rules aren't really rules! They're concepts that can help provide a framework for understanding how to choose a saddle to minimize discomfort along the body's midline. More on this later. The rules also assume a normal road bike riding position; they don't work if your torso is very low, e.g. aggressive TT or tri bike positions, or even some extremely slammed road bike positions. Plus, you should wear good shorts? Now, on to the rules:
1. Wide enough
Choose a saddle that supports your sit bones.
2. Flat enough
It doesn’t poke up uncomfortably in the middle, and you don’t slide forward.
3. Firm enough
You don’t sink in or pinch the saddle’s padding too much in the middle.
4. Try a cutout
Will reduce pressure on the soft tissue under your pubic bone.
4,5 Compare T- or pear-shaped saddles
This is only a “half rule” because there is no real guidance on it.
You could stop reading here, apply these rules when picking out a new saddle, and ride more comfortably. But if you want to explore the rules in greater depth, read on.
RULE 1: WIDE ENOUGH
First, the saddle should comfortably support your ischial tuberosities (or sit bones). If it doesn't, your body weight is being supported by the body parts between them - primarily the labia (in women) and internal penis (in men). Ouch!
The flesh surrounding the sit bones is mainly muscle and fat. Time in the saddle will condition this tissue to do the job of supporting your weight, so comfort will improve over time. On the other hand, the tissue between the sit bones contains many nerves and blood vessels, and over time, sitting on it can reduce blood flow (Schwarzer, 2002), cause numbness and sometimes permanent nerve damage (Weiss, 1994), reducing the duration of erections in men (Shrader, 200) and reducing tactile sensitivity in both men and women. For women especially, too much pressure on the soft tissue under the pubic bone can be immediately painful. To avoid this, reduce or eliminate pressure in the middle. A saddle that's wide enough is the first step. But how wide is wide enough? The illustration below depicts a pelvis on a saddle that's wide enough to support the sit bones and a saddle that's too narrow (right)
Remember: The idea is to support the sit bones. One rule of thumb is that the saddle's seating surface should be equal or greater than the centre-to-centre spacing between your sit bones, plus about 1 centimetre on each side, as depicted below.
You can measure your sit bone spacing in several ways. Many bike shops have "assometers." These devices leave sit bone impressions in a cushion, allowing you to measure the center-to-center distance between impressions. You can do the same thing at home if you are careful. Try sitting on a piece of corrugated cardboard or plasticine wrapped in a plastic bag. A direct measurement is also possible if you are very flexible or have a (very!) good friend around.
Take a few measurements until it's accurate within a few millimeters. Add 2 centimetres. Compare it to the width of the usable seating area of your saddle, or any saddle you're considering trying.
By the way, sit bone spacing has been measured for large populations. This data leads to the following statistical ranges:
Table 1: Ischial tuberostiy spacing among men and women (PeopleSize 1998, http://www.openerg.com/)
The table above lists the distances between ischial tuberosities expected in men and women based on statistical analysis of population data. Once you know your sit bone spacing, you can see if you're in the narrow, medium or wide range of the population. This may suggest you try narrower, average or wider saddles. For many folks who are not average, knowing they are wide or narrow really speeds up saddle selection.
A table of numbers works for some people, but if you’re more the visual type, then the following illustration of the same data may help:
Figure 5: Ischial tuberosity spacing among men and women. A 50th percentile male pelvis is shown, with ischial tuberosity spacing of approximately 118mm.
In the figure above you can see a sketch of a male pelvis with two bell curves superimposed on it. One ischial tuberosity is fixed at the origin (left end of the horizontal axis), and the bell curves represent where the other ischial tuberosity (right side of the image) would fall, assuming a normal distribution of ischial tuberosity spacing among men (red) and women (blue).
This data shows that, on average, men have about 1 centimeter narrower sit bone spacing than women. This may suggest one possible reason that, on average, women have more saddle issues than men. This data also shows that, between the 5th and 95th percentiles, as groups both men and women vary by over 3 centimeters. So statistically speaking, there is roughly three times more variation within each gender than there is between the two genders. (This may partly explain why quite a few women are comfortable riding "men's" saddles, and suggests that some men could consider riding "women's" saddles.) But these are just stats; you aren't a statistic and you'll want to know your individual sit bone spacing to choose the right saddle for you.
What happens if a saddle's more than 2cm wider than sit-bone spacing? Maybe a little more rubbing on the inner thighs and a little extra pressure on the hamstring insertion - assuming a typical road bike riding position and saddle designs - but there is usually not much downside.
On some saddle designs you need more than 2cm extra width. Brooks and similar leather saddles are constructed with a rigid steel cantle plate supporting the perimeter of the leather top. You don't want to sit on the cantle plate, so consider the area between the edges of the cantle plate the effective seating surface, and measure there. Overall, too narrow is typically worse than too wide.
RULE 2: FLAT ENOUGH
Once a saddle is wide enough, it should also be flat enough. If the saddle has too much side-to-side curvature then the centre will be significantly higher than the sides. Too much of this curvature makes the centre of the saddle more likely to exert pressure on the soft tissue below the pubic bone. Almost all saddles have rear view curvature to a degree, so compare several to find one that is less curved.
Figure 6: Exaggerated illustration showing a highly curved saddle (left) and a flatter saddle (right).
You can see the curved saddle decreases clearance under the pubic bone compared the increased clearance on the flatter saddle. Perfectly flat isn't necessarily bad here, although with very flat saddles some cyclists miss the "centered" feeling that keeps the pelvis from moving laterally on the surface of the saddle. Even concave isn't bad if you'd really rather remove contact between the center of the saddle and your body. (You know if this is you: even slight pressure can be painful.) A flattish saddle with a large cutout is sort of concave anyway if you think about it.
RULE 3: FIRM ENOUGH
Saddle padding shouldn't be excessively thick or soft, despite the overstuffed "gel" saddles often recommended to beginner cyclists. Thick, soft padding may initially seem like the obvious solution to saddle discomfort, but usually it just squishes down under the sit bones - and up in the middle - adding pressure where you don't want it.
Figure 7: Exaggerated illustration showing a highly padded saddle (left) and a firmer saddle (right).
The overpadded saddle decreases the clearance under the pubic bone compared to the increase in clearance on the firmer saddle. New riders often quit after replacing uncomfortable saddles with thick, soft saddles that are also uncomfortable. Instead, choose the firmest saddle you can stand.
But is there such a thing as too firm? Some rigid carbon fibre saddles have no padding at all, and some riders of both genders are perfectly happy with them. A saddle with no padding certainly eliminates the "padding squishing up in the middle" issue. Consider trying one that meets the other rules. Initially you might feel some pain around your sit bones, but some of this will go away as the flesh around your sit bones tones up with use and time. If after a few weeks you still feel like you're bruising the flesh surrounding your sit bones then a very hard saddle might be too firm.
RULE 4: TRY A CUTOUT
Even a saddle that's wide, flat and firm enough can still press uncomfortably on the soft tissue under your pubic bone. If so, you may need a cutout.
Figure 8: Saddle with a cutout (left) and saddle without a cutout (right) Here’s an informal “cutout test” (via http://forums.teamestrogen.com):
- Sit on a wooden chair or stone bench or other very hard and unyielding seating surface.
- Hinge forward at your hips (don't bend your back) until you can rest your elbows on your knees.
- Stay that way for a few minutes.
If your "soft tissues" object to this treatment, it is likely you would benefit from a saddle with a cutout. If your "soft tissues" (we're talking labia here, ok?) have no extraordinary issues, it is likely that a cutout is unnecessary, and you might end up being one of the folks who complains about rubbing or pinching at the edges of the cut-out.
A scoop, depression or channel in the middle of the saddle can be an intermediate design that works for some.
RULE 4,5: COMPARE T- OR PEAR-SHAPED SADDLES
The shapes we’re talking about are the silhouettes of saddles when viewed from above:
A T-shaped saddle has the usual narrow front, the usual wider back, and the transition between is also narrow. A pear-shaped saddle has a wider transition between the front and back. A pear is more triangle shaped.
Riders who move backwards and forwards a lot on the saddle sometimes prefer a more pear-shaped saddle. Those who ride a wider saddle often prefer a T-shape. Also, some riders find that a T-shaped saddle reduces chafing on the inner thighs. Athletes who have never suffered saddle discomfort may not understand the need for this in depth saddle analysis. Even some riders with saddle issues might be blind to the beneficial effects of choosing a saddle according to the four and a half rules. They might have even tried and rejected good saddles, often because they didn't feel right. Remember: if you only consider saddles that feel the same you'll keep getting the same. A saddle that makes a real difference usually feels really different. Once you know the four and a half rules and why they work, you can understand why a different feel means the saddle is working. Vivre la difference!
Plenty of riders have confirmed that applying these rules improves saddle comfort, and in turn, training and racing performance.
What about triathlon and time trial?
Once the torso and pelvis rotate forward in the typical triathlon or time trial position, the four and a half rules for road saddles go out the window. With a forward-rotated pelvis, the sit bones are typically off the saddle surface, and the weight is borne in various degrees by the pubic bone, inferior pubic rami and the surrounding tissues. The choice, then, is where to apply pressure? There are three strategies:
Pick a side: Picking a side works with normal road saddles. The athlete sits on the nose with the body offset to either the left or right. The nose of the saddle bears on one inferior pubic ramus or the other. Most roadies do this unconsciously when “on the rivet”. They might not even know it. Some fitters even suggest pointing the saddle to one side. A narrow, rounded saddle nose helps. The pressure can be quite high, since the weight is your body weight and the surface area is quite small.
Figure 10: Pelvis shown with red dot representing a normal road saddle nose on one side.
Pick the middle: This works best with heavily padded, wide triathlon saddle noses. The athlete sits on the nose of the saddle, centered on the soft tissue directly under the pubic bone. The pressure can be lower than picking one side, because although the weight is still your body weight, the surface area can be bigger; the trade off is that you’re sitting on the tissue that’s least able to take the pressure comfortably. For men, sitting on the middle can be somewhat tolerable, but isn’t healthy long term, as penile blood flow is stopped and nerves are compressed. For women this is rarely a comfortable position, as the labia and clitoris are compressed and can be chafed.
By the way, very light and powerful athletes in reasonably short events (say, less than 1 hour) can sometimes tolerate this by changing to a harder gear and pushing harder on the pedals, which takes some weight off the saddle.
Figure 11: Pelvis shown with red oval representing a heavily padded saddle nose.
Pick both sides: This is the ISM Adamo approach. The athlete sits on the two noses of the saddle, with the left and right inferior pubic rami resting on the left and right saddle noses, respectively. This works best when the athlete’s only contact is truly on the tip of the saddle, with most soft tissue off the front of the saddle. Pressure is on only the first few centimeters of the saddle’s noses, with virtually no other saddle contact. (This means for any constant body position, an ISM Adamo saddle should be installed 5 to 7 centimeters farther back.) For many riders, picking both sides may be the best of all possible worlds for the aero position.
Figure 12: Pelvis with two red circles representing twin saddle noses.
None of these strategies have been proven to be completely healthy; in all the regions listed there are important blood vessels and nerves that shouldn't be compressed for long. Nevertheless, the tri position forces athletes to make a choice. The aero position is perhaps one of the least well understood in all of saddlery, so we are not saying any one of these is necessarily the best choice for everyone.
Cervélo pros had been using or experimenting with ISM Adamo saddles, so when we chose a saddle for our tri/TT bikes ISM was already near the top of the list. Since delivering Cervélos with ISM Adamo saddles, the response from athletes and customers has been generally positive. At the 2015 Ironman World Championship, ISM saddles topped the Bike Count. Nevertheless, saddle choice, as with all the contact points, is personal and individual. There is no single best solution for every rider.
- 1. Schwarzer et al., “Cycling and Penile Oxygen Pressure: the Type of Saddle Matters,” European Urology 41 (2002) 139-143.
- 2. Weiss, “Clinical Syndromes Associated with Bicycle Seats,” Clinics in Sports Medicine, Vol. 13 No. 1, January 1994.
- 3. Schrader et al., “Nocturnal Penile Tumescence and Rigidity Testing in Bicycling Patrol Officers,” Journal of Andrology, Vol. 23, No. 6, November/December 2002