Robert Chung said:
"The Pomeranian" wrote
Quoted message said:Well, don't worry, I don't see the same thing, now I see less.
That's interesting. In your earlier message, you pointed out that both riders spent most of their
time around 95rpm, and explained it as incentivized preference (I'm more used to the phrase
"revealed preference" (and "automagically" was a typo--though perhaps more a Freudian slip since
I've seen it used and think it, too, a repugnant neologism)). Now, seeing that a different cadence
was used on the hill than on the flat, you reject the theory of incentivized (shudder) preference
as inappropriate. I would classify that as seeing more.
It is because the samples are reduced. Note that I wrote _before_ you noted the incorrect graph
"There (in the red line) appears to be higher power output at lower cadences, but the sample numbers
are low and again this may point to unsustainability, and probably does considering the rather
significant power output."
The sample numbers are low in that range (coloring them red didn't change that), and I further
pointed out the sequencing problem, which you've only cleared up just now (and that just in words,
not in an actual sequenced data presentation). I asked the question "Was the hill climbing rider
really able to put out 350 sustainable watts at 70 rpm, but only 250 sustainable watts at 95 rpm
(-1.5 dB or -39%)?" So I'm saying I still have trouble with low sample numbers, a unexplained
disparate power output, and the actual sequencing.
Far from shuddering, I left the whole thing open to more scrutiny:
"I suppose that as a social science, we should ask if the "body has a wisdom" about this. Riders are
incentivized to do as well as possible In seeking the optimum because of the reward incentive, they
"listen to their bodies." The question is are they being fooled by the body or is the body telling
the truth? Are they interpreting the message rightly? Have other social influences come into play
that distort the results? For example, a popularized theme of "spin to win" that may or may not have
been sufficiently scrutinized. Or is the spin-to-win advice generally good but properly vague, and
based on 100 years of bike racing experience?"
I see those question marks as question marks.
Quoted message said:Quoted message said:For me this topic isn't what power someone put out at some specific instant or short time period
(2.52 & 5 s), but is rather roughly that of attaining the most Joules out over a "whole race
time period" (for both TTs and Hill Climb TTs: sustainable power).
For me, this topic is whether or not there is such a thing as an optimum cadence and, if so, is it
universal or dependent on conditions (i.e., factor or response). Your original post was that for
you 80+ rpm while climbing is optimal.
No, I didn't write that. Read it again. You're merging separate sentences. I already explicity asked
you "Where do you think I think it is?" You didn't answer then, and now a number of posts later your
presumption pops out. Do you know why I said "I think it is a decent gearing goal, even if it can't
always be met, to have a gear you can turn at 80 rpm while climbing?" You didn't ask or comment one
way or the other.
Quoted message said:I have no doubt that you know yourself well; I was asking if you had come to that finding through
measurement.
Actually, I'm opening myself fully to the possibility that maybe I don't know, or maybe I could do
better with a judicious re-evaluation. I'm questioning established prejudices that I, or anyone else
may hold on the matter, and for basic technical analysis. I don't care how it comes out either way.
Quoted message said:Quoted message said:For example, a rider climbing a hill reaches a short steep switchback for which he/she has
inadequately low gears, and so "stomps on it" for 5 seconds. The "stomping" requires
unsustainable power output, but the sample does show high power there. Immediately after exiting
the steeper section, the rider sits down, "spins fast," and does 10 s of recovery riding. The
recovery riding will be lower than what would normally be sustainable, so the power sample is
distorted low, for the higher cadence. The low cadence is distorted high. How many times has
this exact scenario occurred? A lot I'll bet, and it is due to either habit or lack of low
gears.
I'm sure it happens a lot. However, that scenario does not apply to these particular data.
Why the disparate power? Can I assume you are saying assuredly that the lower powers (higher
cadences) and higher powers (lower cadences) both occurred with an equal sense of effort by the
rider? You aren't at all concerned by any possible distortions?
Quoted message said:Quoted message said:So I don't believe the difference in powers v. cadence as shown in the plot are yet meaningful
as they stand.
They may not be. This is not a plot to settle an issue but rather to raise one (and I know how
unusual that is in an rbr post): do varying conditions influence the relationship between
sustainable power and cadence? I'm way short of asking what that relationship might be, or its
magnitude -- I'm still in the plausibility stage. I think these data (and data from other rides
I've seen) support the theory that cadence is a response.
I can't argue with that other than to say "response to what?" I raised a few more questions
regarding what I believe needs to be sorted out.
Quoted message said:Quoted message said:Quoted message said:> I'm not sure why gradient would be too much of a factor (or any
factor?)
Quoted message said:Quoted message said:> regarding power v. rpm. Maybe it is, but I just don't know why it
would
Quoted message said:Quoted message said:> be...
Because of force. We all appear to know that given a particular gear,
power
Quoted message said:Quoted message said:scales supralinearly with rpm.
We all? I don't presume your wrong (at all), but I don't presume the parameters. Explain.
For a given gear speed is linear with rpm, so power scales the same way with rpm as it does
with speed.
Supralinear, as I've always understood it (and had it related to me), is basically a log
scale/response with an axis translation such that the resulting function passes through zero. So for
flat, with the power required varying as the cube of the velocity, I don't see the "supralinear"
aspect. That's why I asked. I assume P(rpm) because that's the way you phrased it.
Quoted message said:Quoted message said:I don't see how this shows why the so-called "optimum cadence" would change for climb v. flat.
[...] I guess I see it as simply the power is
delivered
Quoted message said:via force and rotation of the pedals. What does it matter if the energy
lifts
Quoted message said:a weight or gets gas molecules moving? How does the body know if the energy (power*time) is
being transferred to potential energy by lifting a weight, or transferred into kinetic energy of
surrounding gases? The legs are simply pushing on the pedals, at a cadence selectable within 8%.
I believe it plausible that the body may know for (at least) two different reasons:
1. Because power = force * f(cadence) and the force response is different on a hill vs. on the
flat: on a hill, pedal force is inelastic wrt to rpm while on the flat the opposite is true.
With 8% gear steps, you can be within 4% of optimum, if such a thing as optimum exists. The power is
applied to the pedals and nowhere else in all cases. If the rider doesn't like the force required on
the pedals, they simply change gears. The steps have sufficient resolution. I do hold the
presumption and belief that "optimum cadence" is not sensitive to 4%, and in any case there is
nothing that can be done about it with the current equipment. The resolution is not sufficient to
change tactics during climbing v. flat, as far as I currently understand things.
Quoted message said:2. Convective cooling.
Consider: EX-1. A rider pedals at 90 rpm in a 53x15, and goes 25.0703 mph. They change the gear to a
53x16, while pedaling at 96 rpm. The speed is unchanged at 25.0703 mph. How did convection cooling
change in any significant way?
EX-2. A rider pedals at 70 rpm in a 39x21, and goes 10.2489 mph. They change the gear to a 39x23,
while pedaling at 76.7 rpm. The speed is unchanged at 10.2489 mph. How did convection cooling change
in any significant way?
Once under a condition, the convection does not change according to rpm, it only changes according
to speed. If there is a baseline energy cost accorded to cadence (which I assume there is, and I
wrote about it under the banner of conservation of energy), then there could be a cooling trade off
in there if pedaling slower has a cooling (efficiency) advantage. That necessarily means that the
power available during climbing is less than that of "flatting." So explain the disparate power of
the climb samples. Why are the climb samples _higher_ in power? They should be lower. Something is
distorted. Either that, or the rider should shift _all pedaling_ to slower comparative rates.
I can't say the "optimum cadence" should not vary according to condition, I'm trying to understand
why it would.