Why cycling and running/walking have almost nothing in common

In response to the q-factor debate (some people believe that narrower is always better, others feel it matters little) I often hear someone spout that our stance width when we walk (basically how widely spaced our feet are as we walk or run) is only a few inches wide, and therefore a very narrow q-factor is mechanically the best.

My response to this is very similar to one I heard from Keith Bontrager once "I'm not sure what walking and riding a bike have to do with one another." And that's true really, but let's look at the similarities and differences.

Similarities:

First, they are both reciprocal motions, meaning that one leg moves one direction while the other moves the opposite.

They are both weight-bearing activities. The amount of weight-bearing can vary drastically however. Walking slowly may produce ground forces equal to your body weight while running can record forces up to 9 times as high. Cycling on the other hand often runs on the range of perhaps 10% of body weight for very easy pedaling, to usually 30-40% for spinning on the flats, to perhaps at or just beyond one time your body weight (think about the times you have been pedaling uphill and your cadence slows enough, where you have to push on the pedals hard enough that it nearly lifts your butt off the seat -- this is roughly one time your body weight).

I could manufacture more similarities, like the fact that the quadriceps and hip extensors are the prime movers for locomotion in each activity, but this is a bit mundane seeing as how they are also the cause in most other forms of forward movement (skateboarding, nordic skiing, blah, blah, blah).

This is about where the similarities end.

Differences abound, and as you might imagine, I come down firmly on the skeptical side of the narro q-factor debate in cycling.

Firstly, running has significantly greater impact on the skeletal system, and most of these effects are good, since this aids with bone density. Cycling studies in the last 10 years or so have shown some scary results in nearly osteoporotic cyclists at pretty young ages, because they have years of training on the bike which is a limited weight-bearing activity.

Mechanically there is a lot going on that separates running from cycling. In running, you have one foot in contact with the ground for a short period (we call this a closed-chain position), then neither foot contacting, then the opposite foot in contact (walking has a brief phase where both feet are touching the ground at the same time). Cycling, however has both feet fixed to the pedals. In walking/running, when we have one foot in contact with the ground only, this allows the pelvis to unlock on one side, since it is not fixed in a closed-chain commitment (so we can swing our leg freely).

On the bike this doesn't happen. What about the recovery phase of the pedal stroke, you ask? (Recovery being roughly from the 6 o'clock position to about 11 o'clock) In this position the foot isn't bearing down on the pedal, you say? Well, actually, it still is. A perfect pedal stroke would have the recovery leg pulling up on the pedal to assist the other leg in it's downward force, and while it may feel like you do this when you pedal, all the research to date has shown that even the most efficient pedalers in the world do not "pull" their recovery leg up. That leg simply can't move fast enough to get out of the way, and we are left with a downward force on the pedal on the back side of the stroke, so in fact we all actually exert a negative torque on the pedals.

If you've ever been on a Compu-Trainer and used their SpinScan you will notice that with most riders if you look at the polar or the bar graph of the efficiency of each pedal at points of the stroke, that often the right leg will appear to be less efficient in it's power phase (roughly from 2 o'clock to 6 o'clock). Now this could be because of some imbalance causing weakness in the right leg, but more often than not it has nothing to do with the right leg pushing down, and everything to do with the left leg not getting out of the way fast enough. 

(Incidentally, this is a very common short-coming to the Compu-trainer technology -- the SpinScan is of very limited value because of it's lack of sensitivity.  Whenever I see other technology based on the Compu-trainer's I have to cringe -- the most glaring example being the Dynamic Fit Unit (DFU) from Guru.  Here is a machine that costs tens of thousands of dollars and the assessment tool it uses is the 15 year old software and hardware from Compu-Trainer.)

Without getting too much into it (because it could be a post or even a book unto itself) most of us are wired to favor or be dominant on our right sides -- even if we are left handed. Some people think this is because we talk so much and our talk centers are on the left side of the brain which is also responsible for right side motor control, and the talk centers stimulate everything and keep that side of the brain "lit up" -- I think that's a neat theory but I'm not 100% sure I believe all of it. regardless, this right dominance is something I see every day. It is certainly no coincidence that about 75% of us sit slightly to the right side of our bike seat.

So we've established that there are significant differences between walking and cycling in weight-bearing (or what could be thought of as total impact), the fixed foot or closed-chain nature of cycling is different as well.  A third area of discrepancy is total range of motion.  Walking/running involve moderate amounts of hip extension, while cycling has none.

One of the largest differences is one that I address in every bike fit I do, and that has to do with foot and lower leg mechanics.  In walking, our bodies are built to absorb impact (there's that word again) by having the midfoot move and collapse towards the ground after heel strike in order to absorb the energy of the foot making contact with the ground.  Cycling has none of this.  Part of that has to do with the lack of "impact" on the lower extremity, and the other half is due to only the forefoot being attached to the pedal.  Forefoot mechanics factor in heavily in cycling, and they are not very well understood. 

(I believe this is the case even in professionals who handle foot mechanics for a living.  I have tested dozens of sets of custom orthotics on the infrared system - made by orthotists, podiatrists, doctors, and therapists - and while some didn't cause any problems, many did, and none of them corrected any alignment issues that extended above the ankle.  Some actually made the foot more comfortable in the shoe, and that's great, but rarely is it necessary to go custom, and spend $400 in order to accomplish that.  I have found over-the-counter inserts to do just fine in these cases)

In cycling,  if you can control the forefoot you often have the ability to make corrections at the knee and the hip as well. 

So what about running you ask?  Haven't you expounded on the benefits of forefoot running postures?

Yes, certainly, I am a believer in...well I wouldn't necessarily say forefoot running because that prompts many people to run on their toes...I would say I'm a believer in not landing on your heels.  Does this amount to a similarity between running and cycling?  Perhaps, but not a very strong one due to two previously discussed facts -- the much greater impact on the foot in running really affects the demands on the foot (this makes correction of lower extremity mechanics on the bike a bit easier and more subtle), and the fact that our butt is also attached to the seat (which makes correction of lower extremity mechanics on the bike much more difficult). 

So, I think it's really difficult to make determinations of cycling mechanics by referencing walking/running.  In fact doing so will likely lead you astray and compund problems.  You'd really be hard-pressed to find two activities that are more dissimliar in some respects.  So be careful, if you are getting bike fit advice, in a bike shop or in a clinic, and the person you're talking to starts referencing walking or running mechanics or studies.  Cycling is different and deserves to be distinguished.

Front of the knee pain, but first....

Someone asked me a good question the other day:

By writing this blog, aren't you worried about giving away the bike fitting secrets that you've learned and inceasing your competition?

I guess I never really thought about it that way. To me, it's like an architect being worried that by explaining to his clients how their house is drawn up, then they'll use that information to finish the project on their own. There is just too much to know, and most folks, while they may find the information interesting (and I hope everyone does -- I know it can be a bit dry, but we are all nerdy cyclists at heart, and this is the stuff we love to read about), it's not likely anyone is going to be able to read my blog and open up shop on their own based solely on this information. I think it's important that there are practitioners of bike fitting out there that are taking the process more seriously, and treating it as it should be treated -- a very complex, biomechanics-based area of study, and not just a bike shop service.

So now onto the technical stuff.

One of the most common problems I see on the bike is frontal knee pain. Sometimes it is a force issue (just pushing too big of a gear for too long)

(brief diversion)
****I frequently get front of the knee pain (on the right) as I get back into riding shape. My seat height is good, I sit fairly straight on the saddle (see HERE); so what's the problem? As you can see from some of the biofeedback studies we did HERE, when I am not fit, my pedal stroke is not very efficient and I tend to be right leg dominant (like most of the population) AND I am very quadricep dominant when re-learning my pedal stroke. I am just pushing too much with my right leg and the choppy nature of my pedal stroke is requiring more of my quads, so my kneecap and patellar tendon are under tremendous strain.****

(and we're back...)
, but it can also be a patellar tracking issue, IT Band problems (and, incidentally, patellar tracking and IT band sometimes are not mutually exclusive), increased patellar compression/chondromalacia, or even referred or radicular lumbar pain.

The common "fix" you hear about with front of the knee pain is that your saddle is too low and raising it is necessary. Many times this is the case, but it becomes less likely when the pain is only on one side. (If you have a leg length discrepancy or your pelvis sits skewed on the saddle, the seat height may be too low for one leg and perfect or too high for the other leg; in this case you have to figure out why you aren't sitting symmetrically on the saddle first, and fix that)

So if your seat height is okay, where to next? One often overlooked area is how we toe in and toe out. In much of the research it is called inversion (toeing in) and eversion (toeing out) which on the bike is a little different than the motion we refer to as inversion and eversion in biomechanics. On the bike because of how the cleat fastens to the pedal the motion is truly just toeing in and toeing out, but in biomechanics-speak, the toes go in (medially) with inversion, but the bottom of the foot actually points in (medially) as well; opposite for eversion.

Generally when we invert our feet on the bike it drives the knee and increases what's called a valgus force on the knee (valgus = think of looking at the knee straight on and a force presses on the knee from the outside and forces it into a "knock-kneed" position). Conversely, when we evert our foot, we increase the varus force through the knee (think "bow-legged"). This valgus force at the knee essentially takes the ever-important medial quads out of the equation more. These medial quads (vastus medialis and a bit less correctly, VMO) are important because they need to be adequately active to keep the patella in between the two notches at the bottom of the femur. If the patella is not lined up then the underside of it gets dragged against the lateral notch and can cause cartilage damage and pain. The valgus force at the knee puts the medial quads at a mechanical disadvantage. Everting the foot a small amount may reduce this valgus force, and consequently allow the medial quads do their job and/or aid in patellar tracking.

All of this can be read in a great article by Gregersen, Hull, and Hakansson in the June 2006 Journal of Biomechanical Engineering:

How Changing the Inversion/Eversion Foot Angle Affects the Nondriving Intersegmental Knee Moments and the Relative Activation of the Vastii Muscles in Cycling by Gregersen CS, Hull ML, Hakansson NA

I have many clients who have front of the knee pain and the simple act of toeing their foot out (eversion) sometimes helps. Some clients can feel it "unlock" or "unload" their knee almost immediately.

So this is a good option to try if you are at a loss for your knee pain. Just keep in mind that like a lot of things in bike fitting, very tiny corrections are necessary most of the time. Also, remember that when you are changing cleat/foot position, you have to think in opposites: if you want to toe your foot out, you have to toe the cleat in.

But keep in mind that the consequences of toeing out (decreasing the "knock-kneed" force etc.) is what often, but not always, happens. Because we are all just experiments of one we cannot take this as the only consequence. I have, in fact, had some clients who show signs of an increased valgus force about the knee when they toe out. In at least one case it was due to some odd midfoot mechanics, but this cannot be discounted -- there are other people out their with these same mechanics and there are most certainly other movement asymmetries that could cause this eversion/varus relationship to break down as well.