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Where EXACTLY are the sit bones?

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Where EXACTLY are the sit bones?

Old 09-11-08, 09:12 AM
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CharlieWoo
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Where EXACTLY are the sit bones?

Responses to my thread "Hypothesis: Sit bone span equal to finger span"

(www.bikeforums.net/showthread.php?t=464117 )

indicate a huge variation in not only the width of what riders call their "sit bones" but,apparently, where they are measuring. References to "having us put our hands up our butts" make it sound like some riders are measuring way far back.

Various sources describe how to measure the gap in the ischial tuberosity. However, this bony structure is V-shaped (?) and the portion that is used in riding depends on the individual's position, yes?

In my case, I run a pretty significant saddle-to-bar drop (15 cm.) and am rotated pretty far forward, so most of my weight rests on the small, forward part of the V. Someone in a more upright position would put their weight further back. So, isn't it true that what constitute your true "sit bones" is dependent on the activity we are talking about?
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Old 09-11-08, 10:37 AM
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get measured out by specialized's butt-o-meter...
or just sit in a hunched forward position on carbon-copy paper.
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Old 09-11-08, 10:39 AM
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I believe the distance between the sit bones is exactly four fingers.
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Old 09-11-08, 11:04 AM
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They are actually called the ischial tuberosities...





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Old 09-11-08, 11:08 AM
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Originally Posted by Hammertoe
They are actually called the ischial tuberosities...
Yeah, yeah. The point is those things are not the part of the pelvis that bears the weight in a typical road-bike position. So what's the point in measuring them********************************************************************************??

It looks (from your diagram0 that the bones that bear most of the weight in road biking are the "inferior pubic ramus".

Inferior Pubic Ramus: new name for Pcad.
.

Last edited by CharlieWoo; 09-11-08 at 11:12 AM.
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Old 09-11-08, 11:09 AM
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They are not...

How do you sit on a saddle...
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Old 09-11-08, 11:11 AM
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Originally Posted by Hammertoe
They are not...

How do you sit on a saddle...
Not with those things. I use them on the sofa.
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Old 09-11-08, 12:04 PM
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This picture should clear any confusion:


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Old 09-11-08, 12:09 PM
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Find a crappy saddle and ride a century on it. You'll know exactly where your sit bones are by the end
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Old 09-11-08, 12:09 PM
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I have similar socks...she looks much better in them.
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Old 09-11-08, 12:22 PM
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Originally Posted by CharlieWoo
Not with those things. I use them on the sofa.
I agree that for me the sit bones are irrelevant for either my road bike or my touring bike. That is not the part that bears most of the weight when I ride. The whole "sit bone thing" always confused me.

Anytime I bring this up people seem to think I am from Mars. Maybe you and I are just both weird?
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Old 09-11-08, 12:31 PM
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Originally Posted by staehpj1
I agree that for me the sit bones are irrelevant for either my road bike or my touring bike. That is not the part that bears most of the weight when I ride. The whole "sit bone thing" always confused me.

Anytime I bring this up people seem to think I am from Mars. Maybe you and I are just both weird?
Guess so, but I'm from UrAnus.
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Old 09-11-08, 12:35 PM
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Originally Posted by CharlieWoo
Yeah, yeah. The point is those things are not the part of the pelvis that bears the weight in a typical road-bike position. So what's the point in measuring them********************************************************************************??

It looks (from your diagram0 that the bones that bear most of the weight in road biking are the "inferior pubic ramus".

Inferior Pubic Ramus: new name for Pcad.
.
Incorrect. The ischial tuberosities are the weight-bearing area. When you're down in an aero position the inferior rami/pubic symphysis get a little pressure, hence the extra padding on the nose of TT/Tri saddles.
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Old 09-11-08, 12:37 PM
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Originally Posted by DrPete
Incorrect. The ischial tuberosities are the weight-bearing area. When you're down in an aero position the inferior rami/pubic symphysis get a little pressure, hence the extra padding on the nose of TT/Tri saddles.
But I am right about the new name for Pcad?
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Old 09-11-08, 02:04 PM
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DrPete is absolutely right. You should be weight bearing predominantly through your ischial tuberosities/sit bones, with some light pressure on your pubic ramus, and slightly more in an aero position. If you are sitting further back, you are sitting on your sacrum or coccyx (which a lot of people do). This can cause injuries from sacrotuberous sprain to muscle straings to nerve root impingement, and so on.

If you're riding further forward, your pelvis is tilted likely more anteriorly or forward, and you are sitting on your perineum, and resting on the ischiopubic rami, and the internal portion of genitalia. NOT a place which was designed to bear weight. This area is surrounded by nerves and arteries.

If I ride that far forward, it just squishes my girl parts... which kust sucks. If you're a man and you're bearing weight in this area, you're also squishing erectile tissue and your urethra.

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Old 09-11-08, 02:06 PM
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Originally Posted by SSarah
DrPete is absolutely right. You should be weight bearing predominantly through your ischial tuberosities/sit bones, with some light pressure on your pubic ramus, and slightly more in an aero position. If you are sitting further back, you are sitting on your sacrum or coccyx (which a lot of people do). This can cause injuries from sacrotuberous sprain to muscle straings to nerve root impingement, and so on.

If you're riding further forward, your pelvis is tilted likely more anteriorly or forward, and you are sitting on your perineum, and resting on the ischiopubic rami, and the internal portion of genitalia. NOT a place which was designed to bear weight. This area is surrounded by nerves and arteries.

If I ride that far forward, it just squishes my girl parts... which kust sucks. If you're a man and you're bearing weight in this area, you're also squishing erectile tissue and your urethra.

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Old 09-11-08, 02:07 PM
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Originally Posted by SSarah
DrPete is absolutely right. You should be weight bearing predominantly through your ischial tuberosities/sit bones, with some light pressure on your pubic ramus, and slightly more in an aero position. If you are sitting further back, you are sitting on your sacrum or coccyx (which a lot of people do). This can cause injuries from sacrotuberous sprain to muscle straings to nerve root impingement, and so on.

If you're riding further forward, your pelvis is tilted likely more anteriorly or forward, and you are sitting on your perineum, and resting on the ischiopubic rami, and the internal portion of genitalia. NOT a place which was designed to bear weight. This area is surrounded by nerves and arteries.

If I ride that far forward, it just squishes my girl parts... which kust sucks. If you're a man and you're bearing weight in this area, you're also squishing erectile tissue and your urethra.

tata
Wow - that post has me aroused. Especially the part about light pressure on my pubis ramus.
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Old 09-11-08, 02:10 PM
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I'm glad you enjoyed it. Practice on and off the saddle. It's the sleazy way.
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Old 09-11-08, 02:11 PM
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I can't make any guarantees, but if I had to put money one way or the other-- YES. you are going to die... sooner or later.
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Old 09-11-08, 02:14 PM
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Originally Posted by SSarah
I can't make any guarantees, but if I had to put money one way or the other-- YES. you are going to die... sooner or later.
Dang.

I better get my saddle jollies in while I can.
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Old 09-11-08, 02:15 PM
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Originally Posted by BananaTugger
Am I going to die?
not yet...but I can't same the same about this line.
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Old 09-11-08, 04:17 PM
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Originally Posted by AlanS
This picture should clear any confusion:


It didn't, but I forgot the question so I guess it did!
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Old 09-11-08, 04:50 PM
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Originally Posted by BananaTugger
Am I going to die?
Excellent questionI will leave that one to the more "axademic" dudes.
Rest assured that your sphincter will be well protected by you sit bones.
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Old 09-11-08, 05:38 PM
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"Where EXACTLY are the sit bones? "

In your case, either side of your ears.
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Old 09-11-08, 05:47 PM
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Originally Posted by BananaTugger
Am I going to die?
No.

Luckily, there is a solution.

HTFU and pedal harder. That'll put more weight on your feet and less on your sit bones.

I see way too many riders with the saddle too low. This not only means the pedalling is inefficient but also too much weight is being borne by the sit bones.
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