As we all sit here getting fat over the holidays and thinking about our setups for next season, Slowman writes articles about fitters, and steadily more people buy P3’s with low-profile armrests which they need six inches of spacers to ride, the need to be properly fit (not just look cool) becomes increasingly evident.
Some fitters have built their method around body angles. This makes sense in many ways, not least of which is the basic physiological argument of ninety degrees being the joints’ strongest position.
Most experts acknowledge that there is a tradeoff between power and aerodynamics; a rider’s most aerodynamic position is not his most powerful. The job of a fitter is neither to make a rider aero nor powerful, but fastest over the long term. Speed, it seems, is the product of three things: aerodynamics, power output, and comfort. Each of these macro categories easily subdivides into other categories as well.
Is the only way to optimize this triumvirate equation a power meter, windtunnel and exposure time? Could these variables be formulated into a general equation from which applications to specific body types be drawn?
Currently most riders use a fitter for ballpark estimates, after which they make further adjustments themselves. In essence we react by feel to the effects of position adjustment on power, aerodynamics, and comfort. Is every triathlete their own best fitter, or is it possible to quantify what has heretofore been subjective?
I did this with Ken Glah many years ago when I still owned Steve’s Multisport. We fit him based on my fit technique and the computrainer’s reading and heart monitor. It took about 2-3 hours until I was comfortable with his position. Ken always and still does ride very low in front.
He then went to the Wind Tunnel with Cobb and he put him in a more “aero” position based on the readings he saw in the tunnel.
Ken then came back to my store and we put him on the computrainer/heart monitor. His results were not a surprise to me. He was aero but lost a lot of watts. Interesting, I see most age groupers in this ultra aero set up, aero bikes, and they (a) can’t ride a straight line (b) can’t control their bikes, and (c) are not efficient on their bikes.
You can take the most aero bikes on the market, put a rider on it in an aero position like I see (critique my position) and everyone has input without knowing what their power output is. I’d rather have a rider not as aero but putting out more watts. There has to be a compromise between the two and very few fitters understand this if they aren’t using a device to check all aspects.
That said, in the 20+ years I’ve been doing this, things have improved and this site has added a lot to the education of both “fitters” and athletes.
That’s something posted here several times. The fitter gets you in the ball park and then listen to your body and read your stop watch to fine tune.
As far as the posted static side view photos are concerned, what they can do is pick up on any gross mistakes. I have fun printing them off and measuring them up with my protractor, but realize that at best, all we’re doing is ball parking.
Is there really a “perfect” bike fit. If so what’s it based upon? I’m skeptical that there is no one way of doing it that will work for everybody. I like the expression that bike fit is trying to mate a machine with a limited degree of adjustability with a human body with a limited degree of adaptability.
It seems to me that most overlooked is post-fit modificiatoin and adaptation that should be required after one undergoes the initial fit and then subsequently trains and gets in different/better shape.
If you are really jacked about the best fit, you will work on it more than once, particularly after significant changes like a new bike and new fitness level.
That being said, I can’t imagine that Ken Glah/John Cobb would do a wind tunnel without a baseline and ongoing wattage analysis as a comparison of the tradeoffs between position and results. That sounds pretty basic…going for was aerodynamics without accounting for the power implications of position changes would seem like a bad approach that any pro would have understood…and which I assume a wind tunnel @ $1000/hour would provide…how can that possibly be a true story?
Francois nailed it. It’s speed at a given level of effort. Not aerodynamics. Not power output.
One can easily see that lower watts at the same speed is better, unless the lower wattage is due to less efficiency…in which case the effort level will have increased for any given power output. If you end up with the same speed though…the more comfortable of the two positions might be best. UNLESS it is a long course, then maybe the position burning the least calories might be best.
Unless you know the metabolic consequences of different positions, you don’t know if the change in power is due to inefficiency. Heartrate would be a simple (although not entirely accurate) tool to help determine the relative metabolic costs of two positions.
Like sharad said, there is STILL comfort to be considered. I’m actually in much less neck pain on my TRI bike than on my road bike…go figure.
There is still a lot of art to a good fit. “Art” is another way of saying “science that is so complicated it hasn’t been nailed down to a formula that fits all”.
Behind this post is an idea that maybe everyone could have the fit that Ken Glah gets using math. I am not at all math inclined, but this is the basic idea.
Intuitively, optimizing speed seems to involve the optimization of the aero, power, and comfort functions.
a=aerodynamics
p=power output
f=flexibility
s=speed
Creating some sort of general equation,
ax+py+fz=s.
If a general equation were created maybe software could be developed which gives the average rider most of the benefits of windtunnel and power analysis without the associated costs.
I put out very low watts for the speeds I hold. As an example, I recently rode 2:13:40 on a flat 1/2 IM. My average wattage was under 200w. The avg spd was 25.5 mph.
I am 5’7’', 128 lbs. If I hit 300w, I am going over 31 mph.
So watts don’t really mean much. You have to learn about your own wattage. They vary from individual, speed doesn’t. 45 kph is 45 kph anywhere.