At exercise intensities well below VO2max, oxygen is essentially limitless and free. Why would one want to use O2 consumption as a measure of economy at typical endurance event intensities?

Kind of like measuring the fuel economy of your car by measuring air consumption instead of fuel consumption...

At these intensities, muscle activation and respiratory quotient would be much more meaningful IMHO. HR and O2 consumption are better than nothing (but not much better).

Dan,

For these explanations to hold any water with me they must also account for the fact that there is an optimal cadence. They seem to focus on why the cadence chosen by competitive cyclists is "higher than optimal" so they come up with an explanation that explains why "higher is better" but fails to explain why cyclists don't choose even higher cadences.

I personally think the real reason are a combination of two. One put forth by Francois in that cyclists are tactical animals and they ride at cadences that allow them to better respond to accelerations (similar to mile runners rarely run all out but simply run to beat the competition, so the races can be relatively slow tactical affairs compared to the potential of the individuals) AND, secondly, they mimick the best cyclists when they are young so they ride at cadences that are higher than optimal for them but they get used to it and since everyone does it it doesn't offer a competitive disadvantage. If 98% of cyclists races were time-trials instead of group races I doubt people would ride the way they do now because they would race strategically, not tactically.

I thank you for the data. It is not that it is not valid or valuable but interpreting data such as this must be done carefully. I put forth what I thought might be weaknesses of the study or interpretation without reading it. I might be wrong.

Actually, this argument has really nothing to do with PC's other than anyone who has ridden them understands how much energy it takes to ride at high cadences (many here think cadence comes "free") and how much bike positioning can affect power output. This is not as obvious to the non-PC experienced rider.

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Frank,
An original Ironman and the Inventor of PowerCranks

"Kind of like measuring the fuel economy of your car by measuring air consumption instead of fuel consumption... "

As opposed to an internal combustion engine, measuring O2 consumption in humans is tantamount to measuring fuel consumption. O2 consumption just happens to be relatively easy to measure. You allude to the fact that respiratory quotient may vary this some but I am not aware that anyone proposes that efficiency changes with cadence because the respiratory quotient changes with cadence.

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Frank,
An original Ironman and the Inventor of PowerCranks

"For these explanations to hold any water with me they must also account for the fact that there is an optimal cadence"

ahlquist does account for it. the "optimal cadence" you're describing is optimal only when considering O2 consumption. a better way to describe it is that it's the most economical cadence, "economy" simply describing O2 consumption.

to that person for whom O2 consumption is the only thing that matters, a cadence in the order of around 65rpm is appropriate.

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Dan Empfield
aka Slowman

Ok. Now that power cranks have been brought into the mix... I have been riding them exclusively for 2 months but my cadence is only 70 maybe 75 but it is really difficult to maintain anything higher. At Ironman Fl this year I averaged around 86. What should my expectations be when I go back to regular cranks? Is it necessary for me to get my PCs up to 80-85? (ouch). I also find it difficult to maintain higher cadence in aero position so is this a sign of a problem with my bike position? (hope not as Mr. Demerly appeared to do an excellent job fitting me).

But, the problem I see is he is trying to explain why experienced racers ride at higher cadences than what has been shown to be most "efficient" based upon reduced glycogen depletion at higher cadences, using lower pedal forces requiring fewer fast twich muscles as the "explanation" of this effect. Does he then explain why this glycogen depletion also has an optimal cadence even though pedal forces would be even smaller at even higher cadences, presumably resulting in even less fast twitch recruitment?

This theory seems sound until looked at critically. It makes no sense to me. It is like those who argue that keeping back pressure on the upstroke has to be the most efficient or best way of pedaling because that is what everyone does (at least, used to).

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Frank,
An original Ironman and the Inventor of PowerCranks

Easy to measure - Yes.

Equivalent to measuring fuel consumption - No. Oxygen demands vary greatly depending on the metabolic pathway used to satisfy muscular energy demands. Muscle activation and/or indirect calorimetry would at least provide some insight into how 'aerobic' or glycogen sparing the effort being measured is.

[snip]

i don't mean to be short or an asshole or anything, but whatever else i say about ahlquist's study is just going to be a restatement of what i've already written, so i hope nobody minds if i just bow out now, and sidestep the inevitable redundancies.

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Dan Empfield
aka Slowman

It goes to show you how much "glycogen depleting muscle contraction" is involved with higher cadences, even with very little force on the pedals. As your muscles develop more blood flow, these muscles will be able to sustain better effort at higher cadences. Takes most people a full season to be able to sustain a cadence of 90. When you can do that you know you are well adapted.

The bike fitters cn comment, especially Tom as he rides on PC's and understands them but i think it points out how little bike fitting takes into account what happens to power (or efficiency) with position. It is not possible to understand the capabilities of each rider by looking at them or by even measuirng power as one doesn't know from which part of the stroke that power is coming from. So they take a one theory fits all approach that works for many but probably is optimum for only a few. Those who do wind tunnel testing have the same problem. If, next year, after you have adapted to the PC's and you went back to Tom to get fitted WITH THE PC"S ON YOUR BIKE I suspect you would end up with a substantially different and better bike position as you would have a real sense of what the position is doing to your ability to produce power. Such a trip in the first few months would be a waste of time beecause things are changing so fast. In the meantime, I recommend you don't worry about it until your engine is further developed. Just remember, if you race at higher cadences or in a position you cannot sustain on the PC's you must revert back to your old habits in order to do this.

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Frank,
An original Ironman and the Inventor of PowerCranks

"Oxygen demands vary greatly depending on the metabolic pathway used to satisfy muscular energy demands. Muscle activation and/or indirect calorimetry would at least provide some insight into how 'aerobic' or glycogen sparing the effort being measured is. "

I agree. I just meant that there is no reason to presume that metabolic pathways change based on cadence so it would seem that measuring oxygen consumption would be a reliable indicator of energy consumption for the short period of a study looking at cadence and efficiency/energy consumption. It would be nice if these studies included both O2 consumption and muscle activation but few of them do.

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Frank,
An original Ironman and the Inventor of PowerCranks

Ok I can't resist, I love a good debate.

So Frank has an issue because the study didn't investigate whther higher cadences would be even more efficient. Well the goal of the study wasn't to acheive that so can't complain about that now. It did however, from want Dan says, show that a higher cadence than the maximal O2 efficiency of 65ish was effective in improving performance, and this is supported by riders in general. Frank you asked why people don't ride at cadences above 90 isn't Lance on 100-110? He looks reasonably efficient. Anyhow, So the next study can investigate higher cadences but heres a few other thoughts:

1. Co-ordination must be a limiting factor here too. I mean how fast can you spin your legs around and not fall off. :)

2. Is it feasable that at higher cadences turnover becomes fast enough to begin increasing fast twitch recruitment again?

3. Keep in mind that the problem with people is that we are all different, so what works well on one case, could be terrible for you. The real answer is to utilize the resources of a major professional cycling team and explore all ossible options :)

4. Riding your bike a lot seems to help the most.

Also with regards to the people who struggle with PC's in the aero position: Muscle fibre recruitment is most efficient in mid range of motion. Hence when you drop onto the aerobars, you shorten the hip flexors, meaning they work in a very shortened position, causing a weaker unit. If you were in a fully lengthend position you'd have the same problem of weakness.

I am probably the a**h arguing about a study I haven't read. I am presuming deficiencies that may or may not be there. Sorry. My points were meant to be pondered, nothing else.

Frank

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Frank,
An original Ironman and the Inventor of PowerCranks

"Frank you asked why people don't ride at cadences above 90 isn't Lance on 100-110?"

Actually, I think Lance tends to ride in the 95-100 range, marginally faster than his competition and I have said this many times, I believe that the higher the power the higher the optimal cadence. Lance probably sustains higher power than just about anyone. That doesn't mean that those cadences are optimum for someone who can sustain 180 watts but many people seem to think so. Before you should try to ride like Lance you had better train like Lance.

I believe your point number 2 is right on. I think I said that earlier.

Frank

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Frank,
An original Ironman and the Inventor of PowerCranks

From one ponderer to another then And these are pretty much off in ponder land, but I'm not sure who else is reading this thread any more....

Unfortunatley I can't afford a pair of PC's (blah blah winge winge) but I am fascinated by them all the same. So I'm going to ask you a couple of my ponders here, and a few things I don't quite understand.

1. What effects of power cranks do you think most attribute to their success running (because recently you said you learnt something more on this). My thoughts are that the strength gains and strength is being used to cover strength, M/s endurance, musularneurocordination etc in the Hamstrings, gluts, hip flexors, and Ant tib, are the most important, and the effect is dependant on how much the individual already uses these muscles in their existing pedal stroke. In running Sprinters especially, running speed is often reflected in strength of Hammies and gluts. So someone who has a poor cycling upstroke, AND a poor running recovery stride is going to gain the most in their running.

2. People struggle to keep a high cadence on PC's. Is this an initial transformation as Neiromuscular and muscle "strength" adapts, or does the recruitment of these muscles with such a larger force mean that they need longer to work, hence a slower stroke.

3. Do you advocate the use of PC's in a race. I can't decide on this one, but putting aside weight etc and focussing purely on technical aspects my thoughts (and we are way into ponderland here) are that PC's work the Hip flexors, hamstings and Ant tib muscles harder than typical cranks (they force you to) so therefore these muscles would further fatigue in training (good thing) but in racing bad thing, as these muscles would be the biggest contributors to running speed. So training them to be more efficient, and share more of the load is great, but on race day, by using normal cranks lets say you are only using these muscles 80% as much in your stroke, so they are fresher. (Your still using them a lot more than you would of before training on the cranks).

4. I find that on my bike, especially hilly rides I don't fatigue in the Quads, its my upper calf's and Hammies that scream at me first, especially climbing. Would this make me a poor candidate for PC's? BTW I think that my Hip flexors are weak and need to harden up :) I also think that agressive aerobar riding works the Hip flexors harder than normal, because of the shortened position they are working in, so general conditioning of these muscles can only help.

5. Its interesting you comment that higher power output should generate higher cadence. What your suggesting then is that everybody has an optimal power output, and the faster cyclists should just spin that power faster? A lot of massive gear pushers in Triathlon used to be the stronger cyclists though. I remember Thomas hellreigel looking like he was pushing a dinner plate for his big chain ring at IMNZ when he won here.

Given that everyone can probably adapt to be come more efficient (but maybe not the most effieient) at a particular cadence and putting that aside, why woud a higher power ouput mean a more efficient faster cadence? Do you theorise that up to power x, recruitment of Muscle fibre is predomiatley slow, and therfore sparing of the legs, ie RAM cyclists, but above power x the fast twitch recruitment increases, so to limit this cadence must increase, lowering individual pedal stroke power and therefore Fast twitch recruitment.

However the counter to this argument is that everyone has a % of their own personal maximal power output that is the optimal blend of fast twitch and slow titch recruitment (just as they probably do for cadence), and therefore it is more efficient to pedal at this personal power output regardless off cadence. When going slow therefore the cadence is reduced and as speed increases/ power increases they are better to increase their cadence, until their optimal blend of fast twitch and slow twitch is reached their also.

I have other ponders, but I'll write a thesis if not careful. BTW I heard an Interview with Lance after the 2002 Tour time trial 1 where he said that he thought he spun too fast and closer to the 120 cadence instead of the 110-115 that is more ideal for him. But we'll have to agree to disagree on this unless Lance is listening ;)

Steve

Sporting trainspotter

Wow, Mr. Nipples (everyone else can tune out) a bunch to get me going. I will try to be concise:

1. "What effects of power cranks do you think most attribute to their success running" At first I thought it was simply training new muscles that could be incorporated into the run. Now I believe it is encouraging more efficient form while training those muscles that allow one to use the form without fatigue.

2. "People struggle to keep a high cadence on PC's. Is this an initial transformation as Neiromuscular and muscle "strength" adapts, or does the recruitment of these muscles with such a larger force mean that they need longer to work, hence a slower stroke." I believe it is simply the muscles are not up to speed. Until you ride PC's you cannot understand how much energy the pedalng motion itself requires, with or without any power. Until the muscles have had any training they cannot do it without substantial rest periods between activation. Hence, the requirement for lower cadences. Once the muscles start to get the capillary bed and enzymes systems of trained muscles they can perform at the level of all the other muscles. This takes substantial time.

3. "Do you advocate the use of PC's in a race. " Yes! In the beginning I thought they were just a training tool and regular cranks would be best for races. I am changing my mind. At least, after initial adaptation and for the first few years i think most will be faster on PC's. I am making some efforts to entice some of my more experienced PC pros to race on them this year which should prove or disprove my theory if I am successful.

4. "I find that on my bike, especially hilly rides I don't fatigue in the Quads, its my upper calf's and Hammies that scream at me first, especially climbing. Would this make me a poor candidate for PC's?" Hill climbing is where most people find the first cycling benefits of PC's. Everyone can b e made better with PC's. That is my story and I am sticking with it!!!

5. "Its interesting you comment that higher power output should generate higher cadence. What your suggesting then is that everybody has an optimal power output, and the faster cyclists should just spin that power faster?" No. Power is force through distance per unti time. To increase power one can either increase force or distance traveled per unit time (increase crank length or increase cadence), or both. Since we are humans we have a limited ability to increase force. However, increased cadence is less efficient. So, the secret is, as we become stronger, then we also have the ability to increase cadence (as we can absorb some of the increased inefficiency of increased cadence) to optimize power overall. In other words, to go from 200 to 400 watts we can either double the force on the pedals, double the cadence or do a some of both. Most would choose a little of both if they were capable. Mostly force and a little cadence is probably the best mix.

I just read Lances book and I don't remember him mentioning cadences like that. Mostly 90-100 if I remember right. He also mentioned working on his hip flexors and efficiency. Wonder what he was using to do that?

Frank

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Frank,
An original Ironman and the Inventor of PowerCranks

While a 2% or 5% change in power doesn't seem like much it is a big deal to most. It is more speed than what people can pick up by getting aero wheels, etc. At the top it is the difference between winning and not being on the podium.

Just using anecdotal data it would seem that many PowerCrankers come to the conclusion that they are faster with a higher stem, more open hip angle (larger frontal area) but more power.

It is just very difficult to know whether any one change is beneficial or not without a trial period.

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Frank,
An original Ironman and the Inventor of PowerCranks