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Over time, my seat (butt) has been broken in by my saddle. I don't have a callus, and nothing obvious has changed. Physiologically, why doesn't riding cause seat soreness anymore?

On the flip-side, what does a saddle do to a less-experienced posterior? Is soreness caused by something as simple as bruising, or is there some other effect going on?

EDIT:

To clarify, I am referring to muscle soreness caused by the saddle rather than soreness of the skin (e.g., saddle sores). The question is about why the soreness doesn't affect experienced cyclists who have adapted (over the course of many months or years).

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I'm curious too. I know this phenomena from both biking and skydiving. Suspect it's got something to do with muscle fiber thickening, but would love to hear from a physiologist. –  Ken Hiatt May 20 '12 at 23:46
    
@amcnabb - Clarification requested. Are you asking about saddle sores? Or are you asking more about structural (muscle/bone) soreness? These are different issues, but it seems that you're asking more about the structural issue. –  user313 May 23 '12 at 20:22
    
I was indeed talking more about the structural soreness. Saddle sores seem to be more commonly discussed, while structural soreness seems to be ignored because it affects new riders much more than experienced cyclists. –  amcnabb May 23 '12 at 21:41
    
@amcnabb - I'm trying to think of a better title for your post. "...as your seat breaks in..." probably comes across as "how your saddle breaks in", which is an entirely different question. I'm thinking, "What happens physiologically as one's butt adapts to sitting on a bike saddle for a while?" –  user313 May 23 '12 at 23:29
    
@wdypdx22, I made a really quick edit, but there's probably something better. I also like yours with the "for a while" removed. –  amcnabb May 24 '12 at 1:41

5 Answers 5

up vote 12 down vote accepted

When seated on the saddle, your weight is primarily supported (or should be) at the ischial tuberosities which are commonly known as the "sit bones".

Quoted from Wikipedia:

When sitting, the weight is frequently placed upon the ischial tuberosity.[2] The gluteus maximus covers it in the upright posture, but leaves it free in the seated position.

Essentially, there is very little sub-cutaneous fat or muscle tissue covering the sit bones while sitting on a bicycle saddle and thus little "padding" between the skin and bone. So, when you go through periods of not riding or are new to riding, that region is not adapted to compression and impact from the saddle. After riding for a while, the bone, tendons, and muscle in that region adapts by strengthening in that region, and no doubt vascular and nerve changes occur as well.

What happens in the case of an inexperienced cyclist or one getting back into cycling, is that micro-damage occurs to the bone, muscle, tendons and other tissue in the area. The micro-damage leads to inflammation and thus pain/soreness. At that point, the the tissues begin to repair and strengthen. The bone is thicker and stronger, the muscles/tendons are stronger, nerves are adapted to the stresses, new blood vessels, etc. Once those tissues have remodeled and healed, there is no more soreness. (Actually, the process can happen again if one goes say, riding for 3 hours to riding for 6 hours, but usually won't be as bad the second time around.)

It's pretty much like any other area of the body that goes through the adaptations from not being exercised to being exercised. So, one gets sore at first, but as muscle/skeletal tissue adapts, one is not sore later on. To some degree, the issue is similar a bruise, but it's much more like the muscular/skeletal adaptations that occurs from exercise.

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As I've remarked several times, part of the "break in" involves pulling the hairs from your butt. It's the hairs, all tangled together, that create most of the "butt burn" that you tend to experience on longer rides.

Shaving your butt short-circuits this step and lets you tolerate long rides much better, with less "break in".

Of course, there are other factors -- you need to develop some "inner calluses" in the areas of most pressure. And you also just need to develop your riding style and the strength in your arms and legs to enable you to remove some of the pressure from your butt.

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Women don't have much or any butt hair, so I think that hair would have to be a secondary rather than primary issue. I would love to learn more about inner calluses; is there a technical name for this, or do you have a link? –  amcnabb May 21 '12 at 3:03
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Women have more butt hair than they might think. It's the small, fine hairs right near "the crack" that are the problem. No technical term for the "inner calluses" -- it's just a general toughening up of the tissue. –  Daniel R Hicks May 21 '12 at 3:55
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Interesting. I am not saying this is wrong - I have no reason to think it is, and your answers have always been good here - but does anyone have any references on this? I really always assumed this was an issue of the muscles in your butt getting stronger. But this answer makes a lot of sense. –  Neil Fein May 23 '12 at 2:31
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All I can say is that this is from experience. I annually take a week-long bike trip (coming up soon) a bit too early in the season for my butt to be fully "conditioned". One year I sorta figured out that shaving my butt might help and did it and it worked. The next year I did the same but missed a spot. The spot I missed was incredibly painful. Now I'm careful to not miss any spots. –  Daniel R Hicks May 23 '12 at 2:47
    
In retrospect, I suppose the question could have more carefully clarified that I was asking about a deep soreness that seems to be felt in the muscles. The pain you're describing is more of a skin soreness, right? In any case, the fact that shaving reduced soreness for you is a very interesting point. –  amcnabb May 23 '12 at 21:46

Here's my theory based on things that do happen in other areas of physical existence that I think are similar. That soreness is actually just discomfort from interrupted flows of vascular systems. You can see similar effects from sitting Japanese style on the floor on your knees. If you keep doing it, eventually your body gets used to the new position, begins flowing elsewhere to compensate, and the soreness is relieved as you have no systems suffering from the lack of flows. Interestingly, this is less prevalent in very young children, who are both incredibly flexible, and do not have established paths of preference for blood. A lot of pains we have come this way, especially if you're like me and sit around most of the day.

I actually thought about this when cuddling with the wife last night because of your question. It's probably the same thing that causes my arm discomfort as she lays on it, but I never get used to it because after a brief while of it becoming annoying I usually shift out of it. The same thing happens to a lot of traditional martial arts students. They don't sit in seiza for very long, so they never have to get used to it. I imagine the same thing would happen if you only biked for 10-15 minutes instead of forcing yourself to endure it for a while and acclimating.

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Not directly to the point of the question, but it should be pointed out that, among other things, "serious" cyclists "self-select": If a person is genetically inclined to have a sorer than normal butt, they're less likely to stick to cycling and more apt to engage in some other sport.

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I suspect that a suspended seatpost + sorbothane saddle will solve this issue completely. First is to absorb large bumps/shocks and the sorbothane absorbs road vibration. Unfortunately I have not been able to find sorbothane saddle or gloves/handle bars.

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The OP wasn't looking for a solution to saddle numbness, he/she was looking for the physiological response that decreases/prevents muscle soreness after many miles of cycling over a long period of time. –  jimirings Oct 2 '12 at 14:28

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