Why do they call them sit bones?

[dekindy]

In 2008, RBR's Fred Matheny attended the annual Serotta International Cycling Institute Science Symposium and Expo in Denver, Colorado.

As a result he published 9 articles on his website, RoadBikeRider.com. One of the article was, "The Search for the Ultimate Saddle". Darryl Thelen Ph.D. and Heidi Ploeg Ph.D. from the Department of Mechanincal and Biomechanical Engineering at the University of Wisconsin-Madison presented there. 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(Italics added.

They also indicate that sit bone width for women is about 20mm wider on the average than for me.

I am going to ask the folks at RoadBikeRider.com what that means for saddle width. I am wondering if the 134-136 width of the Prologo Scratch Pro has a good chance of being wide enough or should I try the more expensive version. I purchased the smaller width version on the Real Cyclist website at a 75% discount so it will be considerably more expensive to experiment with the 143 since I will probably not be able to find even close to that good a deal again.

[fourflys]

In 2008, RBR's Fred Matheny attended the annual Serotta International Cycling Institute Science Symposium and Expo in Denver, Colorado.

As a result he published 9 articles on his website, RoadBikeRider.com. One of the article was, "The Search for the Ultimate Saddle". Darryl Thelen Ph.D. and Heidi Ploeg Ph.D. from the Department of Mechanincal and Biomechanical Engineering at the University of Wisconsin-Madison presented there. 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(Italics added.

They also indicate that sit bone width for women is about 20mm wider on the average than for me.

I am going to ask the folks at RoadBikeRider.com what that means for saddle width. I am wondering if the 134-136 width of the Prologo Scratch Pro has a good chance of being wide enough or should I try the more expensive version. I purchased the smaller width version on the Real Cyclist website at a 75% discount so it will be considerably more expensive to experiment with the 143 since I will probably not be able to find even close to that good a deal again.

while I can see what they are getting at (and they're a lot smarter than me), I think it depends on how you ride to some extent... a more aero position will equate to less weight on the "sit bone" area I would think...

The reason say this is I have a couple of Brooks saddles, a B17 (upright saddle) and a Swift (more like a traditional road bike saddle). On both saddles, I can see an indent when something that looks like "sit bones" have been putting weight on the saddle...

I can also tell you that a Fizik Antares saddle (143mm) is a LOT more comfy for me than an Arione (130 something mm)... how that equates to how I sit on the saddle, I have no idea... I just know my butt tells me one is a LOT more comfy than the other...

[oliver1850]

for me, shape is more important than width. I'm uncomfortable on anything with a curved top, like a Turbo, or even a Rolls or Flite. So while maybe the study is accurate about not much load on the actual sit bones, it may be because the saddle shapes they tested are concentrating the load in between them.

[zray67]

Excellent tread. I'm not knowledgeable enough to add to this tread. But, thank you for the issues that were presented.

[dekindy]

Fred Matheny replied back.

Fourflys was correct in that it refers to a more aero position. That begs the question as to what is defined as aero. Does it have to be in the drops or does that include riding on the hoods as well? I interpret from his comments that when climbing with hands on top of the bars weight is on your sit bones. But if you are riding in a semi-aero position with the bars lower than the saddlem and leaning forward you are not concentrating your weight on the sit bones. Maybe Paraic could chime in?

[Louis]

Specialized has some similar saddle information on their web site: here (http://www.specialized.com/specs/spec.jsp?speccode=bodygeometrysaddles)

[dekindy]

Specialized has some similar saddle information on their web site: here (http://www.specialized.com/specs/spec.jsp?speccode=bodygeometrysaddles)

Using the Assometer and sitting in their special stand which has a foot stool to raise the feet, my sit bones measured 144. What angle does this simulate? What width saddle would you recommend? They recommended the 143 which happened to be all they had in stock currently. Coincidence?

I tested the 143 Romin and it felt very good, slot seemed to be working. However there was much more pressure focused on my sit bones. I did not know if it is worth it to try it for 30 days to see if I would make the adjustment or if a 155 would be better. Historically I have spent most of my time on the hoods but am gradually emphasizing riding more and more in the drops.

[fourflys]

Using the Assometer and sitting in their special stand which has a foot stool to raise the feet, my sit bones measured 144. What angle does this simulate? What width saddle would you recommend? They recommended the 143 which happened to be all they had in stock currently. Coincidence?

I tested the 143 Romin and it felt very good, slot seemed to be working. However there was much more pressure focused on my sit bones. I did not know if it is worth it to try it for 30 days to see if I would make the adjustment or if a 155 would be better. Historically I have spent most of my time on the hoods but am gradually emphasizing riding more and more in the drops.

well, I finally got a chance to actually ride the WTB Silverado I'm demoing yesterday... I figured it would be horrible since the width is 133mm and my Antares I like is 142mm wide... now I didn't ride it long as I was on the cross bike and it was a short trail, but I didn't even notice the saddle under me... I figured I would at felt a little discomfort, but none... time will tell if this saddle will indeed work for me, but I was very surprised...

so, I guess I'm saying I'm going to throw out ALL preconceived notions about a saddle based merely on specs...

:beer:

[shiftyfixedgear]

I think they're called "sit-bones" because "ass - bones" just sounds too harsh.

Zat a good enough answer ? :)

[Dhphat]

They are actually called the Sitz bones, named after the man who discovered them.

http://en.wikipedia.org/wiki/Tuberosity_of_the_ischium

Now as far as the saddle goes, you have to pay attention to a lot more then just the width of a saddle when you are choosing one. Yes, it is very important to have a seat the correct width, but the shape of the rear of a saddle, can effectively change the fit of the saddle. I like to think of the rear of the saddle as the platform for you pelvis. If it is domed like lets say a old Flite, a Scratch or a Aliante, the seat effectively fits narrower. Because the domed part of the seat basically penetrates in between your sitz bones, making it harder for them to be properly supported. An unsupported pelvis can cause many different issues.

So I'm assuming it won't fit you, but its up to you obviously.

just my 2 cents.

[1centaur]

Not sure what you mean by "domed" re: Scratch and Aliante. I hate saddles that have a rounded lump down the middle of the target area - seems designed specifically to cut off blood flow by pressing into soft tissue. The Scratch and Aliante are relatively flat in that down-swale area, with the dip designed to provide room for soft tissue that humps, or domes, do not. They use the dip to take the place of a cut-out, in the process forcing the sitz bones to take the load, while humps spread the load but into undesirable places, IMO.