Richard Diaz

The Buzz on Professional Bike Fitting



Posted: Friday, May 08, 2009

by Richard Diaz
diaz human performance LLC

I've ridden a bike with "purposeful intentions" for over two decades now and like most cycling enthusiasts, the extent of my fitting experience had been limited to what occurred at the conclusion of my purchase. The friendly sales person who had me mount my shiny new bike, after which he summarily had me put my foot at the bottom of the pedal stroke, adjusted my seat post and sent me on my way. Bike fit complete, no conversation regarding comfort, aerodynamics or really anything else for that matter.

With the popularity of triathlon and the evolution of the tri-specific bikes, things have gotten a bit more complicated more tweaking is necessary to arrive at the optimal posture on our bikes in order to eek out every drop of performance.

Here is an important distinction to remember:

Bike sizing is about determining the correct frame size to suit the rider.

Bike fitting on the other hand is about altering the components and or accessories to fit the cyclist's body architecture for maximal comfort and efficiency. Simply stated: sizing is about the bike, fitting is about you!

In our facility we provide custom bike fits for clients whom have come to the realization that an "off the rack fit" is just not going to cut it. It is not unusual for a competitive cyclist or triathlete to spend several thousands of dollars on wheels, a lighter frame, and carbon components, all to improve aerodynamics where in fact a well thought out bike fit could easily produce far greater performance at a fraction of the cost of these high tech accessories. To perform a custom bike fit properly requires, in some cases, in excess of 2 hours from start to finish but the investment in time is well worth it.

You might ask, what could possibly take so long to fit someone? There are basically five contact points between the rider and the bike (the hands, hips and feet). If you trace these contact point back from the feet to the hands there are several joints that are directly or indirectly affected by the alignment and positioning of the rider. The pecking order of a great fit begins with "comfort" followed by enhanced "power output" and finally "aerodynamics".

From a fitter's prospective it's interesting that many riders tend poorly prioritize the order of concerns and jeopardize the final outcome. Forcing the equipment and rider into a radically aggressive aero position certainly minimizes drag from the wind but in many cases the trade off is the sacrifice of power output due to the cramped posture. A more aero position that drastically reduces power is of no value. Being in a radically aerodynamic posture is also difficult to sustain even if the power is not lost due to the position. Violating the order (comfort, power, aerodynamics) with the hope of achieving a better time in an event is not recommended.

Simply put, if you are more comfortable you can work harder for longer. The fitters challenge is to create a reasonable compromise among these postural characteristics, and clearly this is where the art of the fit is defined. As they say, "the proof is in the pudding". Even though the fit subject may note dramatic improvements in the lab during the fit process, we wait to hear the field test result which is really the only thing that matters.

"I had heard that a professional fit can make all the difference in power and comfort. Prior to the fit, I felt that my bike splits were pretty decent but I had chronic pain in my neck and shoulders after long rides. I got fitted at dhp just prior to participating in the recent breath of life triathlon. I was astonished by my improvement in speed, nearly 3 miles per hour average and a seamless transition off the bike. My legs felt fresh and I did not experience the heavy leg syndrome I generally expect. It was the most effective thing I have done in all my racing."

Frankie Ayers,



I think its important to note that with training as the rider evolves, the needs of the fit may change. Many seasoned riders are far more capable of sustaining deeper and flatter postures without compromising comfort and keeping this more horizontal torso is the goal to get below the wind and cut down on resistance.



The fitting process



To begin with, there are several questions that need to be answered to determine where the ultimate fit will lead. The primary goal as mentioned earlier is always comfort first. If you are not comfortable, you will train reluctantly and your lack of comfort is generally the first sign that you are on your way to pain and eventual injury.



Pre-fit interview query

One of the first questions we ask prior to the fit is to rate your current comfort level on the bike on a 1-10 scale. Most clients, surprisingly grade their comfort level between an 8 and10. Then mid way though the fitting process, they commonly discover that they were not nearly as comfortable as they had thought. As a species we tend to adapt to our environment regardless of how harsh it may be, and in the absence of a better feel we have nothing to gage our current state of comfort. Here are a few other questions we typically ask prior to the fit.





Off the bike bio-mechanical observations

It is important to observe the way a client walks in order to determine the direction that the feet normally travel during a normal unencumbered gait. This is a pre-fit analysis that is often overlooked. Consider that most pedal/cleat systems do provide a bit of lateral float but the foot is still attached to the pedal and generally forced into a specific plane of movement. If the connection between either of the feet and the pedals are forced outside the normal direction of travel the outcome is generally pain at the knee and less force production with each pedal stroke.



Client Feedback

At the end of the day, it does not matter how right or wrong a rider looks on his or her bike. What matters is the functionality of the relationship between the rider and bike. It is critical to involve the rider in the cause and effect process; "is this better, worse or unremarkable"? The fitter needs to be a good listener because the rider's feedback is really the only thing that matters? Generally putting a rider into the appropriate "starting angles" will feel more comfortable but as the fit process becomes more intricate, first observations may be confusing. More load in areas of musculature that did not carry load in the past will feel different or possibly cause soreness but after a few rides the results will start to restore faith in the process.



The Adjustments

In most typical fits the chief areas of concern are general; they amount to a seat height adjustment, a fore / aft seat adjustment and a simple cleat alignment. Our approach to determining these adjustments are performed in the traditional methods, by using a goinometer and a plumb bob, but we feel that these old school methods of measurement which are static (no motion) are generally not as precise as dynamic (moving) measurements. In our opinion this only "puts us in the ball park". We incorporate high speed frame by frame video capture software that affords us the ability to cross reference the static and dynamic measurements to arrive at the most appropriate angles for the seat height, fore and aft position of the knees and the positioning of the torso over the frame, spinal alignment which shows us stress points at the neck, the level of flexibility exhibited and a host of other "reproducible bits of information that we can compare during the adjustment process.



The contact points between the bike and the rider begin at the hands/handlebars, hips/saddle and the feet/pedals, with the feet being the most critical of all the contact points. We have two feet that interface with the pedals and up to five adjustments per foot which need to be considered. Before we begin the process of adjusting we carefully measure the subjects' feet to note the angles the feet are positioned naturally. As it turns out nearly 90% of the population naturally make contact with the ground with the outside lateral edge of the foot. This angle is known as "varus", very few people make contact in a "neutral" position and even fewer make contact in the "valgus" position (the inside of the foot). The reason that this measurement is important is that it dictates the travel of the lower limb (foot to knee). If you press down with the inside or outside of the foot the outcome is stress at the knee. Studies have shown us that the majority of cycling related injuries occurs at the knees. This is why it is so important to hone in on how the feet interface with the pedals, it is where the pain typically manifested and where the power is going to originate or leak.



Here are the variations of adjustment at the pedal:





We employ the use of lasers and bio-mechanical body markers that clearly provide us with very telling information in respect to the travel of the knees and feet. This and the use of a variety of other tools and appliances' support our goal of complete and positive alignment of the most critical contact point in the fitting process.



Over the past few years many of the quality bike shops are slowly beginning to employ more comprehensive fitting processes. I highly recommend that before you start dumping countless dollars into your bike with the hope of purchasing speed that you allow a qualified bike fitter to help you get more efficiently acquainted with your bike and you'll undoubtedly be pleasantly surprised at how much more performance you can acquire. The rest is just icing on the cake!







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