You seem to be confusing metabolic cost with mechanical cost.


Hagberg et al. found a somewhat similar relationship for cycling way back in 1981:

http://www.ncbi.nlm.nih.gov/pubmed/7263451

In any case, though, the results of either study are completely at odds with your hypothesis.

Since the UCI recently outlawed motors, it seems to me that metabolic cost and mechanical cost are directly related.

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Frank,
An original Ironman and the Inventor of PowerCranks

Nope.

It's hard to argue with that logic.

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____________________________________________
Virtual Run Coach
iPhone or iPad: http://goo.gl/KoWru7
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Prove it.

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Frank,
An original Ironman and the Inventor of PowerCranks

It was proven - for running - in this study (http://faculty.css.edu/tboone2/asep/Harris.doc) where metabolic cost remained constant while mechanical cost decreased as speed increased.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Determinants of metabolic cost during submaximal cycling
http://jap.physiology.org/cgi/content/full/93/3/823

J. McDaniel, J. L. Durstine, G. A. Hand, and J. C. Martin

The metabolic cost of producing submaximal cycling power has been reported to vary with pedaling rate. Pedaling rate, however, governs two physiological phenomena known to influence metabolic cost and efficiency: muscle shortening velocity and the frequency of muscle activation and relaxation. The purpose of this investigation was to determine the relative influence of those two phenomena on metabolic cost during submaximal cycling. Nine trained male cyclists performed submaximal cycling at power outputs intended to elicit 30, 60, and 90% of their individual lactate threshold at four pedaling rates (40, 60, 80, 100 rpm) with three different crank lengths (145, 170, and 195 mm). The combination of four pedaling rates and three crank lengths produced 12 pedal speeds ranging from 0.61 to 2.04 m/s. Metabolic cost was determined by indirect calorimetery, and power output and pedaling rate were recorded. A stepwise multiple linear regression procedure selected mechanical power output, pedal speed, and pedal speed squared as the main determinants of metabolic cost (R2 = 0.99 ± 0.01). Neither pedaling rate nor crank length significantly contributed to the regression model. The cost of unloaded cycling and delta efficiency were 150 metabolic watts and 24.7%, respectively, when data from all crank lengths and pedal speeds were included in a regression. Those values increased with increasing pedal speed and ranged from a low of 73 ± 7 metabolic watts and 22.1 ± 0.3% (145-mm cranks, 40 rpm) to a high of 297 ± 23 metabolic watts and 26.6 ± 0.7% (195-mm cranks, 100 rpm). These results suggest that mechanical power output and pedal speed, a marker for muscle shortening velocity, are the main determinants of metabolic cost during submaximal cycling, whereas pedaling rate (i.e., activation-relaxation rate) does not significantly contribute to metabolic cost.

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______________________________________
"Competetive sport begins where healthy sport ends"

Are you proposing that inefficiency (mechanical or metabolic) increases with the square of the cadence....or with the square of the cadence only above the cadence?
If the latter, what do you propose is the natural cadence?

It's hard to argue with logic.

Frank has always argued for the former, incorrectly claiming that it a physical (as in, physics-based) requirement.

The difference between the mechanical cost and the metabolic cost is that the latter but not the former is biological in origin.

So this study basically says that the metabolic cost is not based on the cadence, but the velocity of the muscle shortening no? So 40rpm @ 200mm cranks is the same as 80rpm at 100mm so the cadence does not necessarily dictate metabolic cost, however, if we are assuming the same crank length then an increase in cadence would lead to an increase in muscle shortening velocity and an increase in metabolic cost no? Am I reading this wrong?

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Ride Scoozy Electric Bicycles
http://www.RideScoozy.com

LOL. I had simply stated that mechanical cost and metabolic cost were related. You replied "nope". Your comment would mean that the metabolic cost of generating more power is unrelated to the power to the wheel because one is mechanical and the other biological.

The only way the body has to overcome mechanical costs associated with cycling (or anything else) is biological. Therefore, they are related. There might be some small deviations from a strictly direct relationship, as efficiencies might change as the circumstances change, because we are dealing with a biological system, but they are related. Thank you for your participation.

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Frank,
An original Ironman and the Inventor of PowerCranks

Prove I am incorrect in that assertion. The only "evidence" you have in that regard is point to a model that is constructed such as to not allow any "physical losses". It is possible for me to come up with a rigid pendulum model that would have no "walking" losses either, at any cadence. Of course, this paper shows that such a model doesn't reflect reality.

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Frank,
An original Ironman and the Inventor of PowerCranks

Must...destroy...science...to...sell...gimmicks.

Yes the "Performance Artist" strikes again.

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Hamish Ferguson: Cycling Coach

No. You said that they were directly related. Again, they are not. For example, a perfectly rigid cyclist with frictionless joints and locked ankles pedaling in a complete vacuum experiences no mechanical cost whatsoever (if it did, it would be a violation of the 1st Law of Thermodynamics). A pedaling human, OTOH, does incur a metabolic cost that is a function of power output and speed of muscle shortening.

I love Frank. He is 100% correct 100% of the time in his own mind. And he can never be persuaded otherwise. That is awesome. It reminds me of a lot of great people.

What is not awesome (except if you love train wrecks) is that he tries to market a product to the same group he loves to antagonistically argue with. I cringe at the economic value destroyed by every keystroke. Maybe less so now than a few years ago (not cringing, destroying value).

Frank - you need a pseudonym for ST.

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re muscle shortening:

" pedal speed, a marker for muscle shortening velocity, are the main determinants of metabolic cost during submaximal cycling"

Assuming constant crank length isn't pedal speed based on cadence therefore metabolic cost is based on cadence? If this were not true then the article should say metabolic cost is only based on power output but it doesn't.

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Ride Scoozy Electric Bicycles
http://www.RideScoozy.com

They are directly related in the sense that if one increases the other increases (reasonably) linearly as opposed to an inverse relationship where if one increases the other decreases or an exponential relationship. (edit: see http://en.wikipedia.org/.../Direct_relationship

And, use your model that violates the physical laws of the universe (there being no perfectly rigid material) to prove that no losses occur in the real world if you must. I find it laughable that you insist on using a model that prohibits losses to analyze losses.

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Frank,
An original Ironman and the Inventor of PowerCranks

So, AC doesn't agree with what FD posted. BFD. Where does everyone get off sniping at FD just because he stated something that AC doesn't agree with? If all of you who lie in the weeds waiting for a chance to take pot shots at someone from AC's grassy hillside actually did some useful experimentation and shared it with the rest of the SlowTwitch brethren, the world would be a much better place.

End Of Rant...

Mechanical Cost versus Metabolic Cost - WGARA??? Personal experience tells me that walking up a flight of stairs the day after a 40K time trial is one hell of a lot easier after using 165mm cranks with a cadence of 99 rpm versus using 177.5mm cranks at 80 rpm on the same course with the same conditions (not scientifically verified - sorry AC) given the same relative power output (+/- 5 watts) and same relative speed (+/- 0.2 kmh).

According to AC, riding the 165s at 1.710 m/s should have a higher metabolic cost than riding 177.5s at 1.487 m/s, unless, of course, I completely misunderstood the article he referenced (which, if you knew me, would be completely understandable).

So, where does that leave me? I sit here with just as many questions as before, but no more answers. Am I experiencing less Mechanical Stress, less Metabolic Stress, or less of both at the same time?

Okay grassy hillside inhabiters, flame away...

Just remember,

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I know enough to know I don't know enough...

your cadence is ~20% higher with the 165's?

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Ride Scoozy Electric Bicycles
http://www.RideScoozy.com

Yes... Although I have been consciously trying to increase my cadence since I switched to the 165s on June 9th. The first 'test' time trial I did with the cranks, which was June 10th, resulted in a cadence increase to 88 from 81. I must admit, however, I was highly motivated to spin as much as possible during the test.

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I know enough to know I don't know enough...

Shouldn't the higher cadence lead to more slow twitch fiber recruitment? Walking up stairs is all fast twitch so it is not suprising that it is easier to walk up stairs after using the 165's. I would even bear to say that you could generate more power by recruiting a few more fast twitch muscles with a slightly lower cadence - somewhere inbetween the two. You should be exhausting your slow twitch and fast twitch muscles where in the first case you seemed to have and in the second cause your fast twitch muscles still had something left afterwords meaning you didn't utilize them during the test. This is all speculation of course :)

edit: my point is I don't necessarily think your sense of fatigue is based on metabolic efficiency. You could of burned more calories at the higher cadence. The reason it is easier to walk up stairs is because you didn't fully utilize the fast twitch muscles, not that you burned less calories.

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Ride Scoozy Electric Bicycles
http://www.RideScoozy.com