Retul Bike fits

If you've read my blog before you know that I use the Retul system of motion capture (www.retul.com). I get a lot of questions about it -- and a lot of business frankly.

I often hear,

"Wow, that must really make the fittings easier, huh?"

After using the system for a while now I finally have an answer to that. Does it make the fittings easier? The short answer is "No", unequivocally, it does not make the process simpler.

Blasphemy, right? Retul is definitely the most influential technology to come into bike fitting in, well, maybe forever, and here I am dissing it?

Well, I don't think it is a "knock" on the system because it doesn't make bike fits easier. People and companies (i.e. Specialized) have been taking a reductionist approach to bike fitting and it has done nothing positive to the process. The *Fit Kit", *BG Fit*, *Wobblenaught* among others have tried to take this very complex process and turn it into a nice neat, packaged "revenue driver" that every bike shop in the world can become an expert in.

I think it is actually a tribute to the system that it doesn't "dumb down" the process. It in no way tells you what you should do to take corrective action for the cyclist - it just provides a lot of very accurate data about the cyclist's mechanics.

For each of the parameters it measures -- for instance the frontal angle a rider's knee tracks at relative to the vertical, called Knee Travel Tilt -- Retul provides a range of normal limits that each one, in an ideal situation, should stay within.

The difficulty lies in the shear amount of data. If you focus on one measurement and make changes to the rider's position to "fix" just that one measurement, often other measurements that are also a problem, don't change or get worse.

So, no, my bike fitting process has not gotten simpler. But I'm not the least bit disappointed. Actually this has been the most productive and fun year for me with bike fittings (in my 12 years as a physical therapist).

My bike fittings have gotten better, and that's the important part. The Retul system has allowed a level of accuracy and confidence that is hard to beat. Plus when it comes to bike fitting, "simple" isn't always the best solution.

But "better" is.

Musings about credentials for bike fitting

I get asked a lot by people out of state, My next trip to Colorado, I'm going to come in for a fitting. But do you know anyone in my area that can do a good bike fitting?

That's a hard one. I don't have a lot of names that I trust implicitly to do a comprehensive bike fitting. I think by endorsing someone, I am putting my reputation in their hands. Not many people out there I would do that for. There are a few, and if you live in their territory I will let you know who they are.

I am pretty particular about my fitting process, and I think too many shops out there are relying on the WOW factor of their gadgets, and their client's....I don't want to say ignorance, because that seems harsh -- after all, bike shops should know bikes, and many riders just don't have the inclination to learn about their bike and that's just fine. That's why you have a bike shop! But many clients do trust that their bike shop knows all things bike. Bike fit included.

Unfortunately that is just not the case. Most bike shops know bikes. They should. "The bike" is the easy part in the equation of bike fitting. Truly, anyone with a little time and motivation can learn enough in a short time to WORK in a bike shop. Every year thousands of high school and college age kids begin working at a bike shop and in pretty short order they are assembling and repairing bikes right alongside the "career mechanic." There are bike mechanic schools out there, but very few people building bikes in the United States are attending them. I think that's a shame. It doesn't say much for the person who is a career mechanic and it certainly doesn't help them earn a better living. When you have a profession that is unregulated, unlicensed, and requires no formal training, then you just don't have to pay those people that much. (and by "you" I mean the market in general).

Side note: A very experienced and skilled bike mechanic is an amazing thing. They are such a wealth of bike knowledge that at times is indispensable. I want to be clear how much I respect the true experts of this discipline. My point is that you likely won't go to you bike mechanic for a bike fitting just as you wouldn't go to your bike fitter for a question about derailleur actuation ratios or air chamber pressures on your rear shock.

So to get back to my point, the bike is the easy part to learn about. The variables are few and relatively fixed.

The human body, however, is exactly the opposite. It's not likely that you are going to be able to "apprentice" with a doctor, or a PT, or an exercise physiologist, and learn their trade in a few weeks or months. There are too many variables, and what's more, often these variables are hidden under layers of skin, muscle and fascia, so an intimate knowledge of their location, function, and physiology is necessary. (Again, in contrast, most of a bike's parts are easily seen and quantified.)

So you can see how it would be easy for a bike shop to alter your bike for you, but difficult for them to explain to you why you need it changed.

Some bike shops will say that they have been doing bike fits long enough that they know the 10 most common syndromes associated with ill-fitting bikes, and that that covers them for most cyclists. I don't know about you, but I don't want to pay someone hundreds of dollars in a fitting fee and more money for new equipment if they don't KNOW that it is going to help. In the last ten years I have done more fittings than most bike shops in the country, and I would estimate that fully 25-35% had some combination of mechanical issues that manifested themselves on the bike in a way I had not seen before, and about 50% fell outside of what I would consider to be the "10 most common bike fit issues". In these situations I had to rely on my education and experience with the biomechanics of the human body. 

To understand all these differences it takes time and lots and lots of clients -- I call it the "Malcolm Gladwell Effect".  In his fantastic book Outliers: The Story of Success, he explains that thorough research has come up with a metric for understanding why some people become experts at the top of the field, and the general threshold for this is 10,000 hours of practice.  Bill Gates began programming as a "tween" at  a time when only a handful of people on the planet even had access to a computer to program on.  Michael Jordan out-worked all his competitors by spending hours and hours EVERY single day to improve his skills. 

Similarly, a bike fitter only gets to be an expert when they spend every day working their diagnostic muscles.  This is where physical therapists and other clinicians have a huge advantage over bike shop employees and other fitters -- we get to practice and flex those same mental muscles every day, even outside of our bike fittings as we treat 5, 10, 15 clients a day.  The treatments are different but the "work" and knowledge gained and reinforced is the same.  Typically even a busy bike fitter may see 5-10 clients a week -- this would be an awfully slow way to learn the craft.

This also brings up a point that bike shops are in the business of selling bikes and bike parts. Unfortunately with the boom in the number of shops offering "fitting services" many did so because their industry advisors were telling them how many replacement parts and accessories they could sell.

I'm not trying to make people paranoid or distrustful of their LBS. Fact is I think there are plenty of shops out there TRYING to do the right thing. I just think that they in over their head with the complexity of many bike fits.

The difficulty lies in the fact that many people experience discomfort or a decrease in power and if you just LOOK at them, they appear to be set up in a very typical road position.

Example:
I had a client recently come in for a fitting on a bike she had bought a few months before. She hadn't ridden it much because she bought at the end of the fall and she was not a cold weather rider. She got a "good deal" on the bike. The young salesperson helping her helped her find the bike, they set her up on a trainer and she pedaled the bike for 2 or 3 minutes. It felt "Okay" (her words) while she was on the trainer, but to be sure, they stopped the lone "bike fit guru" (who is also the head mechanic and part owner) as he was rushing across the shop in search of a part for another client, to have a look. He watched her sit on the bike and pedal for 5 or 6 pedal strokes and declared, "Looks good." And he rushed off. Sometimes the shop (but really the client) might get lucky and everything might actually BE good.

In this case, however, once she spent more than 5 or 10 minutes on the bike it was clear she wasn't comfortable. So they came to see me, and this is when she had her second chance to get lucky -- the bike could be the right size but just need some adjustments - maybe we could "make it work". Unfortunately, the frame was the wrong size and to have an appropriate reach on the bike she'd need to have the seat all the way forward on the rails (with a 0 degree setback post) and a 60 mm stem -- definitely not ideal.

So what is the lesson with that story? Again, not that you should distrust your LBS, because I think this shop was TRYING to do the right thing (admittedly a bit half a**ed). They are just not very good at it.

Luckily there are more and more bike fitters that have education in anatomy, biomechanics etc. AND have years of experience applying this knowledge. These two things are incredibly important and you should do some digging to find out about any bike fitter you intend to visit.

What are our muscles really doing when we pedal?

So my fit Studio is in a  Physical Therapy clinic, which makes sense, because I am a practicing PT.  My co-worker, and owner of the PT clinic, Rik is trained in a new biofeedback system.  Biofeedback uses electrode patches placed over the muscles to determine how much these muscles are working -- how much, how soon they kick in, how long they stay "on", how they "turn off", etc.  As you can imagine, this is highly useful with our clients.

So we decided to test a few cyclists and see what we came up with.  We could simultaneously use the Retul, to pick up movement imbalances and then cross reference with the biofeedback to try and figure out what the muscles on each side of the body were and were not doing.  We can even then use the biofeedback while the person pedals to "train" them what activating certain muscles at specific times "feels" like to help correct the underlying muscular problem.

First we have to test as many people as we can, to start to figure out common muscular patterns.  Hopefully we can figure out what is "normal" but if my line of work has taught me anything, it's that there aren't many "normals" out there.  That's why I think it's more likely we'll find common motor patterns that may not be symmetric, amongst many athletes.

Subject #1 : Me, 33 y/o, male, 5'10", 175#

I have a fairly symmetrical pedal stroke.  If I had to guess I would think that I am a bit right side dominant, and probably scoot off the right side of my saddle because of it.  But we don't have to guess, because here is a right and left Retul file from a recent test on myself:

Not bad.

Next was to hook up the biofeedback.  This involves placing small sticker-like electrodes strategically over the muscles you want to test.  Wires snap to the electrodes and run to a little processing unit that reminds me of a car radar detector.

The "radar detector" talks to the laptop via a BlueTooth connection -- the setup is pretty slick.

The software that Rik uses seems to have endless choices on how to set up the display screens so that you can simultaneously see what the

 different muscle groups are doing.

  When I was hooked up to the biofeedback unit we decided to test vastus lateralis (VL) (the quadricep or thigh muscle on the outside of the

 leg -- this tends to be very pronounced in cyclists), vastus medialis (VM) (quad to the inside just above the knee, and the hamstring.  We tested these muscles on both legs, so we could compare how much more the right or the left lateral quad was working, but we could also compare how much and when the medial vs. the lateral quad did work on the same side.  We could also compare this to how the hamstrings worked.

We tested all three muscle group -- VL, VM, hamstring -- on both legs, of course at 150 watts and at 215 watts.

The printout from the biofeedback looks like this:

The lines and squiggles at the top half of the page are usually in color, but they are a bit above what we want to get into here. 

Below are the printouts bottom half of the page.  The colum to focus on is the one that says "Mean" -- they are basically the normalized mA that the electrodes pick up from each of the

 muscles.

There are four sets of data:  comparing VMO/VL at 150 Watts, VMO/VL at 215 watts, VMO/hamstring at 150 watts, and VMO/hamstring at 215 watts.

VM/VL @ 150 watts

VM/VL @ 215 watts

VM/hamstring @150 watts

VM/hamstring @ 215 watts

As you can see from the sheets, my right quads (medial and lateral) both work more than the left at all wattages.  But when I increased from 150 watts to 215 watts my left quads increased their activity 18% while the right increased 23% (VL) and 29% (VM).

The next round of tests, comparing the VM to the hamstrings on both sides confirmed an 18% and 29% increase respectively for left and right for the VM when going from 150 watts to 215 watts.  The hamstrings, which overall, were not very active increased 31% on the right and 38% on the left; this increase on the left might make one think that the left "evens out" at higher wattage, but I think it is still a bigger issue: the right hamstring was more active at 150 than the left was at 215.  The fact that the starting point for the left hamstring was so bad made it's improvement seem more drastic.

What did we learn?

I think this first round of tests is encouraging and shows that we can, with good effect correlate what our mechanics are like (from the Retul data) and what the muscles themselves are doing.  We should be able to explain why a cyclist may pedal with an asymmetry and whether it is due to a poor motor plan or if it has more structural origins.

I think we can safely say that one of the main reason that I sit a bit skewed on the saddle is because my pedal stroke's motor plan has a significant emphasis on my dominant right leg.  I think with more data we will see that my current pedal stroke is poor in the efficiency category because I have not been riding as much  lately and I am getting a very small contribution from the hamstring muscles.  I am not "pedaling ellipses" but rather more up and down (and definitely more down than up).

Theory

I have a theory as well about the activation of our quadriceps when we pedal that has to do with left and right efficiency.  I believe I am more coordinated (because pedaling is a coordinated task) on my right leg -- it's clear my hamstring are more active on the right and help to smooth out my pedal stroke.  I am also more skilled at one leg pedaling drills on my right leg -- less "clunking" through the stroke and better cadence.  

I think, based on some of the muscle activation graphs that I saw for me (and they would have been difficult to post here -- sorry), that our more efficient leg will see the quads activate later and relax earlier than the non-dominant side.  So the non-dominant side will have a more consistent or longer activation patter than the dominant side.  

This to me seemed counter-intuitive at first, but after some thought I realized that because my dominant side hamstring were activating better, they would inhibit the quads sooner since the load was now taken up by this new group of muscles -- the more "normal" or efficient pedal stroke.  The dominant side could more accurately and quickly kick itself on and off in time with my cadence and when it kicked on it could fire more motor units more quickly.  I think this would have implications, of course, on negative torque values (when your quads are still pushing down on the pedal after it has passed the dead bottom center position and therefore exerting negative torque or power) but also in terms of fatigue.  The non-dominant quad is staying "on" longer, even when it shouldn't and wastes unnecessary effort -- it fatigues quicker even though it is adding less to the overall workload.

Anyway, I should have more data coming this weekend and next week with a  few more guinea pigs so stay tuned.

Talkin' bike seats

I mentioned in my last post that, for the average woman, and ideal seat design would be wide in the back to support the wider ischial tuberosities, but then needs to quickly narrow to avoid compressing the tissues distal and lateral to the sit bones. 

This narrower space between the femur and sit bones that we tend to rest (which ends up being the proximal hamstring -- medially the semi-membranosus and laterally the biceps femoris) is not the only reason for this saddle shape.  The woman's sit bones are oriented more in the frontal plane (more side to side) than a man's.  The male sit bones are set more in the sagittal plane (front to back).

When you factor in the natural translation of the hips and pelvis downward at the bottom of the pedal stroke, you can visualize that the male sit bones can more readily follow this path of movement -- sort of like a knife blade slicing through the dirt.  The female sit bones can't move as easily in this path -- imagine running the same knife through the dirt now turned to it's side a few degrees, like a plow.  The amount of shear force (or at least the potential for shearing) is much greater.

Essentially, all the angles of the pubic and ischial rami (the structures that form the "loops" on the bottom of the pelvis, and that we sit on) are steeper and sharper and because of this, less contact with saddles is probable.  I think this is the reason women often struggle with saddles -- more contact and shear forces -- and not just the fact that they have wider sit bones.

Saddle position

Of course, the right saddle is nothing without it being fit in the right position.  Many cyclists are on saddles they are unhappy with, but the reason is that they are not sitting on the part of the saddle that is meant to be sat on.  Most are scooted too far forward, even to the point where the sit bones don't rest on the saddle, but rather the saddle is squeezed in between them and the rider is resting more on their soft tissue -- this is a problem, obviously.  A huge mistake I see all too often is having the saddle tilted down --- yes, even a little is generally not a good thing.  

A bike seat needs to be in the right place fore and aft so that the sit bones can contact the wider, more cushioned portion of the saddle, and then it needs to be level so that the sit bones can rest on it.  If you aren't perched on your bike seat, then you aren't effectively stabilized to make full use of your pedal stroke. 

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Think about this: 

If you have a seat slid all the way back on the rails, so that the seatpost clamp is at the front of the seat, and it is level.  What happens when you sit on the saddle?  What if the rails are made of Steel?  Titanium?  What I'm getting at, is that a saddle has a static (or unweighted) position and a dynamic (weighted) position.  The dynamic position is the only one that really matters.  It has been my experience that especially with titanium railed seats if the seatpost clamp is to the back of the rails the seat will flex downward, if towards the front of the rails the seat will flex backward.  Therefore I have allowed some seats to leave my Studio tilted up or down at times to accommodate.

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This leveling of the seat brings me to my last point about a good seat -- for a man or a woman.  The seat should have at least some portion of it's surface should be flat and not fully sloping. 

This FSA saddle is a good example of when some seat designs can cause trouble for people.

The centerline of the seat is the high point and the cover slopes downward to either side.  I am sure there are people who find this saddle comfortable, but I haven't met them yet.

I am intrigued by the new fizik Antares -- the entire saddle looks flat.  I will have to try it out and get back to you on that one.

Next up :  Some top secret stuff going on in the lab.  Well, not really secret, but it should be pretty cool.  We are combining the use of the Retul dynamic "mo-cap" with a very sensitive biofeedback system so we can see what exactly some muscles are doing when we pedal, and using all the information (and there is tons!) to try to determine what the leg muscles are doing when....say, a knee tracks laterally more then the other side. 

From the preliminary findings, I think I can say that many will be surprised at what we are finding.

--J