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Physiology/Bio Mechanics(14 posts)

Physiology/Bio MechanicsDY
Feb 23, 2002 12:52 AM
Is there anyone out there that really understands the relationship between the body and the machine (bike)? It seems that there are so many variables in people to have everyone ride the same (basically) equipment. I'm speaking mostly about how the leg interacts with the pedal/crank. There seems to be so many different body types. Some people pronate, some are neutral and some supinate. There are leg length differences. Some are "pigeon footed" and others "duck footed". Some have wider hips and others narrower. If we make a big deal out of the difference between a 170 mm crank and a 172.5 mm (a 2.5mm difference) and we are so sure to have exactly 120 psi in our tires, then why aren't we equally detail oriented with our bodies? With the difference between the length of our legs or the fact that maybe one foot points out a little more than the other or that one foot is usually larger than the other. I know maybe some won't be interested in this, but I'm hoping to find more of a scientific person that may understand this and be able to shed a little light. I'm interested more from an injury standpoint rather than performance gain. Is there a company that offers a pedal that could take all of these variables into account?
re: Physiology/Bio Mechanicsallervite
Feb 26, 2002 9:00 PM
Most pedals do provide for some of these variables and other components on the bike provide for the rest.

Pronate and Supinate are striding terms not spinning ones. They describe the lateral movement of the foot as the heel strikes the ground and the weight of the body rolls forward over the span of the foot to the ball of the foot. Since the weight of the effort remains on the ball of the foot while cycling, these terms have no use here. However, it is true that your foot may naturally tilt inward or outward while pedaling and there are cleat shims and orthotic inserts on the market that address this issue. I personaly don't think that either are necessary for most cyclists.

As far as leg length differences, if your lower legs are long than saddle height is all you have to worry about. If you have long or short femurs than crank length and fore/aft saddle position take care of this issue.

Pigeon footed and duck footed riders simply adjust the cleats of their shoes clockwise or counter clock wise.

Riders with wide hips get wider axles on their bottom brackets and/or move the cleats of their shoes inward. Narrower hipped riders do the opposite.

There are a lot of riders that are very serious even obsessively detail oriented over bike fit. Eddy Merckx was one of them. Edmund Burke has filled books with this type of minutiae.
re: Physiology/Bio MechanicsDY
Feb 27, 2002 12:30 AM
Thanks Allervite.

You're right about the two terms refering to running. I was just trying to somehow communicate what I meant by the feet having a tilt in or out. I think that you have covered about all of the options to fit a bike to the legs/feet. I guess what I am looking for is someone in my area (San Diego) that understands all of that in practical hands-on terms. I've done a lot of trial and error over time, but I would be very interested to find someone that knows more. I have developed some knee problems and it worries me that it will only get worse if I don't do something about it. I don't want to get stuck in the details, but I want to make sure I get healthy and can ride for many more years.
re: Physiology/Bio Mechanicspeloton
Feb 27, 2002 1:28 AM
The terms you are thinking of- supination and pronation would be talked about in terms of forefoot varus (supination) and valgus (pronation) for cycling. Looking at how your foot angles when barefoot, and what surrounding musculature is developed can show which you do. I have a great deal of forefoot varus, and you can see quite well how my forefoot angles, and how the muscles on the lateral upper side of my shin are developed as a result of correction for this issue.

BTW- What is the knee problem? There may be some generalizations for what is wrong with your alignment.
re: Physiology/Bio MechanicsDY
Feb 27, 2002 2:28 PM
Thanks Peloton for the info. I took a pic of my knee. Thought if would be easier to describe it with some arrows. I tend to be a bit bow feet naturally turn to the outside when standing (ie. duck footed) and my feet when hanging naturally tend to be in the forefoot varus position. Any general help or insight would be appreciated.
re: Physiology/Bio Mechanicspeloton
Feb 27, 2002 3:49 PM
It looks from the picture that you have a little retroversion of the femoral head that is causing some external rotation of your foot. This also decreases your q factor a little too. If you are also a little bowlegged this could be parially due to this, and perhaps the angle of inclination at which your femoral neck called coxa vara. It's probably not real significant, but it may be there. This also can decrease the effective length of your leg, so if one leg has more than the other you can see how this could create a leg length descrptancy. You describe rolling to the outside of your shoe, so I imagine you have some forefoot varus too. Hold your foot up behind you with the knee at at 90 degree angle and have someone see if the medial side of your forefoot is 'closer' in relation to your body than the lateral side of your foot. It should be easy to see, as if you put a stick on the forefoot it would be at an angle instead of flat. I would imagine that you have pretty good development of your tibialus anterior on the outside upper of your shin too if this is the case. These could be some of the things that are causing some of the pain, or it could be a musclular imbalance, or even other problems with the knee.

In the first 90 degrees of your cycling stroke, when your foot is at the angle you are experiencing pain there is great activation of the quadriceps femoris group, and the gluteus maximus. The vastus medialus is one of these muscles, and it is the muscle at which you are pointing that pain is originating from too. Maybe there is something there? Hard to say for sure in this forum, and maybe I'm reaching on what little I know about your knee and biomechanics. You also talk about pain from the 'ligaments' on the back of your knee. In the area you are pointing there is the popliteal fosa tendon and the tendons of your inner hamstrings, maybe these are what is hurting? Some of these tendons come from the muscles that abduct your thigh like the gracilus and other muscles of the groin. These muscles are more capable as abductors in people with coxa vara. The popliteal fosa comes from the semitendinous, a hamstring muscle. Maybe there is injury or imbalance here?

I guess what I am trying to say is that there could be some biomechanical factors at work here that are contributing to your pain. Real hard to say for sure though especially with only one picture and no other knowledge of medical history or biomechanics, and I would send you straight to an orthopedic if I were working with you so that a diagnosis could be made. I'm in no way qualified to make medical decisions, and even with my background in kinesiology my biomechanical guesses could be way off without seeing you in person. Doctors are the only ones that can say for sure, and maybe an orthotic or some change in your position can be made from there. See a doctor so as to know for sure what you are dealing with, and then solid decisions could be made to rectify your situation. Hope this helped more than it confused. :)
re: Physiology/Bio MechanicsDY
Feb 27, 2002 6:16 PM
Thanks for the info. I am really out of my element with these discussions on anatomy. I did go to a doctor about 2 years ago (orthopedic). He took x-rays and found nothing wrong with the "bones" He thought I had a mild cartilage tear. He thought it was from the tennis I played (I played from about age 8 up through high school and college). It never hurt me during tennis or biking for that matter. There was never an "event" that I could point to and say that is where I injured it. I just woke up with a swollen knee unable to walk. Then the pain and swelling gradually go away. Well It was my left knee about 2 years agao and now my right, with pretty much the same problems/pains. I'd be more than happy to send you more pics if thay would help. In the mean time I guess I'll continue to keep looking for an expert in my local area. If you'd like to mail me your address, you can mail it to
Feb 27, 2002 11:16 PM
A cartilage tear could definitely cause you some discomfort when cycling. Meniscus damage like that from the wear and tear is not all that unusual in athletes. Repetitive motion or repeated jarring could cause this condition. The doctors call it 'crabmeat' from it's appearance. The good news about it is even if you have to have it 'scoped to remove some of the crabmeat, the recover time is real quick. I've seen guys back on skis in under two weeks from having this surgery. Everyone I know who has had this done for has also reported better range of motion, less discomfort, and less locking of the knee joint. It sounds like you know what this condition feels like from your other knee, so maybe it's worth getting it checked. I'll try to remember to shoot you an e-mail soon.
re: Physiology/Bio Mechanicsjswhern
Feb 28, 2002 3:58 PM
Not all Ortho's are on equal terms as are these comments. These would be doctor's. The individual with a diagnosis from a picture where did you get your lic. from Kodak? DY, you need to get a second opinion. For all you know it could be your whole postural alignment that could be causing this. You have to look at the total body. The words pro/supination are basic anatomical terms and relate more to than just your feet--give me break. They also refer to the hands and forearms. Before you offer medical advice you need to renew your subscription to AMA. Good grief Charlie Brown!! DY, How come you never had an MRI? For x-rays to show anything it must be a very significant involement. Take charge of your situation and be proactive in your diagnosis and treatment. GET AN MRI.
Just to let you know:allervite
Feb 28, 2002 6:26 PM
This is a "Message Board". People post on it to get other people's input. This is not a doctor's office, hospital, or sport's medicine clinic and has never claimed to be so.

DY posted his question of his own freewill to see if anyone had any suggestions or related experience. I'm willing to bet that he is intelligent enough not to perform self-surgery if someone on this board told him to.

Insulting a poster because he gave an honest opinion to another poster's problem is ludicrous, and Peloton did suggest DY see a professional.

Where did you get your common sense? Perhaps it was from the same bubblegum machine that you found your tact.
re: Physiology/Bio Mechanicspeloton
Mar 1, 2002 6:45 AM
Get a clue, man.

If you re-read my posts, you will see that my only real advice is to see a doctor. I did make some general obervations of his knee, and offered that they could be off seeing as this is only one picture and that I can't see him in person. From his descriptions, and the picture I ventured some guess that look and sound feasable from my experience. Never did I say to get anything done, or that it was a diagnosis of sorts. The man wanted some ideas, and I offered some. If you have any better, then feel free to share. I would love to hear from your wealth of information.

I hate to sound like a jerk, but come on now...
Sorry this discussion got so heated...DY
Mar 1, 2002 5:47 PM
What I was really looking for was some general ideas on how my set-up could be effecting me physically. I have always done things by trail and error, but since I had an injury I was a little more interested in doing things better. I thought that if I said my knee hurt in the back or on the side that someone could give a general place where to start, like "if your knee hurts in the back, your seat is too high" Well that's the kind of stuff I get at bike shops when I talk to them. I thought that the guys here would have a better understanding possibly. That's why I posted the topic. I just wanted a general idea of where to start tweaking (cm by cm) my seat height, set back, etc... I lowered my seat a bit, purchased some of the "big meat wedges" and have been riding my trainer for about 20mins every other night just to get back on the bike and see how it feels.. No problems so far, but I also haven't been pushing like I would on the road or a hill. Thanks
Feb 27, 2002 10:33 AM
There are a number of books that cover this issue, but I agree with you that it is hard to do it yourself. You should be able to find a coach down there that will look at your position and fit you. They may even do it for free.

Call your USCF rep or the sports dept. of UCSD. A lot of racing clubs have a coach too. We do.
re: Physiology/Bio Mechanicspeloton
Feb 27, 2002 12:47 AM
Sure, what your body does biomechanically makes a large difference. Some pedals do take some of this into account, but not to a huge extent. There is a Look pedal with range of adjustment for q factor, and shims for forefoot varus or valgus. Pretty pricey though, and most people probably don't need or know what to do with these features anyway.

I think a lot of the information that you will find out there is catering more to a striding movement like running, which may or may not entirely cross over to be applicable to cycling. A lot of people concentrate on just the foot as well, even though a lot of the alignment picture occurs much higher up on the body. A pigeon toed rider may have anteversion of the femoral head bringing the toes in. A rider with toes out may have retroversion of the femoral head. Coxa vara or valga of the femur can affect the angle at which the femur points down to the knee inside or out and affects the q factor as well. All these conditions can also affect how different muscles work as well. An individual with coxz valga (the femur angles out, decreasing the q factor- think bowlegged) can more effectively use the muscles of the groin for abduction. Other muscle groups are also affected by changes in aligment brought on by either muscular or structural differences. It just goes to show that there is a lot to aligning one's self on the bike. Some people can produce more power in certain positions due to their physiology and alignment factors. It's hard to say that it can all be taken care of by a pedal for this reason. I guess the good part is that most people aren't to the point where their aligment is so different that anything real radical needs to be done, but we can all benefit from a little tweaking of our bike position and pedal interface.

I really think the biggest structural deficiency that we ignore is leg length descreptancy. Everyone's legs are slightly different lengths, and you may be surprised how different yours are. Try having someone measure from your navel to the bottom of your feet while laying down to see what I mean. This alingment factor can contribute to a large number of problems and issues here. I think of lot of knee, hip, and back problems could be rectified by addressing leg length, and possible performances gains as well. This could be taken care of with an orthotic, shim, or combination of both depending on needs.

I think though probably the biggest problems with alignment is the lack of good information out there, and even misinformation applicable to cycling specific situations.

Cool topic though.