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Wednesday, June 24, 2009

Felt B2 triathlon bike fit

I'm just recovering from a weekend of doing bike fits out of town. Occasionally I do this -- mostly around western Colorado and eastern Utah. When I have 3 or more interested clients (that seems to be my comfortable threshold right now for a proper "driving time/fitting fee" ratio -- at least for a 2 - 2.5 hour drive) I will make the trip out to them and set up in a corner somewhere all my equipment.

The Retul travels quite well. It packs away neatly into (what I am told is) a gun case. The most difficult thing to plan for is to have enough parts and equipment for as many possible fitting changes as possible. Carrying a few dozen stems of various sizes is no problem -- it's the handlebars (because of their size), and seatposts (too many different diameters) that are tough.

So anyway, I was in beautiful Basalt, Colorado this Saturday and Sunday to see a number of clients. I ended up doing about 11 hours worth of fittings on Saturday and another 3 hours on Sunday, so you can begin to get an idea of why I am "recovering".

Lots of very nice people, ages ranging from in their 30's to the upper 70's. Yep, you read that right. There are some very fit folks out in this part of the country.

One client that was a lot of fun was Dave C. He is an avid long distance triathlete; he just finished a 70.3 in Boise the week before. He is very fit, motivated, and attentive -- your basic Type A triathlete. He listened very well and asked a lot of good questions - exactly the type of client I like to work with, because the more a client knows about what is going on, the more likely it is they will see the complexity of the decisions that need to be made in their bike fitting. This is a client who will see the process, as we do it, for what it is -- a service that is one of a kind and geared toward only making their bike work better for them.

So Dave is fit, but like all human beings who live on the modern world of driving cars, computer work, and tools that do our work for us, he has a few imbalances:

+ one leg is stronger and more coordinated than the other
+ he is asymmetric through his shoulder motion and strength
+ he has a small twist originating in his lumbar spine
+ somewhat weak intrinsic foot muscles and resultant pronation tendencies, etc. etc.

When you start to list all these things out, you get the impression that he's a wreck -- not so. This is very typical of what I find in my initial body assessment (he actually has fewer and smaller issues than many).

He has some neck discomfort when on the bike for a while; recovering from some knee pain, of the tendinitis sort, and some back pain on occasion as well.

Here are his first two Retul files that we took:

He had his (very well appointed and beautifully built) Felt B2 set up in the more relaxed seatpost position, and had also put on a stem of equal length to the original it came with, but now with more rise to raise the aerobars up some.

Many times I see people where their pedal stroke clearly has a hitch or hesitation in it, but Dave has spent too much time on his bike for that. His issue was more subtle. After doing this for ten years, I can see that his pedal stroke, while very practiced and relatively smooth, seems slightly disjointed. It's almost as if his upper and lower body are working independently of each other, rather than together.

After looking at the Retul files, it was clear his left side was getting sacrificed -- it had more lateral knee travel and the knee tracked at about an 8 degree angle, not to mention more hip motion.

I was more concerned with his angles at his elbow and shoulder, however. The angle at his elbows was almost 100 degrees and his shoulders were open and rather stretched out (the Retul takes two different shoulder or "armpit" angles -- to the elbow and the wrist). When your shoulders are stretched out like that a few things happen. First, your lats (latissimus dorsi) are lengthened and if they are pulled too far, they can exert a force on the lower thoracic and lumbar spine where they originate. This decreases the mobility of the lower half of the spine. Also, the shoulder blades, or scapulae have to move with our shoulder joints, so when the shoulder is flexed excessively, the shoulder blades must protract (move outward), thereby stretching the muscles that attach the shoulder blade to the mid-thoracic spine. Just like with the lats, this decreases the mobility of this portion of the spine. Take a look at this picture and you can see this with the "round-ness" of his back.

Also, note where the elbow and the shoulder dot are located, with the elbow being in front. In the aero position, we would like to support ourselves (especially the upper body) with as little active muscular input as possible, and if we need to use muscles, we'd want to use respiratory muscles (muscles we use in breathing) as little as possible. Often, when the elbow and shoulder have this relative position we are using excessive upper body muscular force to hold us up, rather than just "resting" on our skeletal support.


So to fix things I wanted to first address the upper body, lower body disconnect I was seeing. Dave's Felt was built with a two position seatpost, and he originally had it in the further back, relaxed seat angle position, so we changed it to the steeper configuration. We also made sure the seat was level (a huge mistake that triathletes make with respect to saddle position is to nose-down the saddle to reduce pressure on their perineum. This just causes you to bear more weight on your upper body as you constantly slip off the front of the saddle -- I always think of it as "tripod-ing" on the bike) and made a small seat height adjustment to accommodate the now-level seat.

This fit is proof that a higher handlebar position isn't always more "relaxed" or comfortable. Because we were rotating his hips forward and up over the bottom bracket, and because Dave has good fitness and strength in the right areas, we were able to lower his handlebars and in the process we put his upper body biomechanically where it needed to go. We improved his power, we reduced the muscular requirement to hold himself on his bike (he will have a front heavy sensation on the bike for a while since we brought his center of gravity forward on the bike, but this will decrease as his body begins to proprioceptively "get it") and improved his aerodynamics all with just two changes.

His left side was being sacrificed, as I said before, and we needed to get it in the game. It is less coordinated and not as strong, so we put a couple of forefoot wedges in his left shoe to improve that foot's contact with the pedal. Over time, this correction, will begin to re-train the muscles in the left leg and hip to get through the pedal stroke without inhibiting the right side.

Here is an after photo to compare with the previous one:

Look at how much more relaxed his spine looks. His elbows are tucked underneath him nicely, and because we've taken stress off the muscles supporting the shoulder blades (which incidentally also attach to the neck) he is able to move his head easier from side to side and look up. Go back and look at the first photo -- see the impression that his shoulder blade makes under the skin. No such impression on the after picture because that shoulder blade is resting more comfortably on the back of the rib cage rather than on the side of it.

The position is definitely more compact, and will take some adjustment time -- but luckily Dave is in a step-down period of his training, so he'll benefit from some moderate rides to allow his body to adapt. We may still make some minor tweaks in the near future, but I think he now has a good long distance tri bike position to keep him powerful for a full 112 miles. (But I'll let Dave himself comment here on how the fit is working, if he'd like)

Monday, June 1, 2009

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.

The Big Ride