Efficiency / Why pedal in circles?

Without denying that there is benefit in developing the hip flexors, I would like to inquire into the line of thought posed by Andrew Coggan, namely, that efficiency may be optimal in some areas of the pedal revolution, and not as high in others. The ‘holy grail’ of pedalling technique, since long before PCs came on the market, was perfectly distributed torque throughout the pedal revolution. My simple question is: Why?

The study of pedalling efficiency has a lot of factors to it. One factor is whether the angle of force applied is perpendicular to the crank arm at any given point. Anything off perpendicular will involve application of force that does not contribute to the propulsion of the bike. The loss is relatively small at angles that are not far from perpendicular, but can become substantial as the angle increases.

However, there is biomechanical efficiency to consider as well. The discussion about hip flexor usage has focussed upon the weakness of the muscles relative to the weight of the leg and/or driving force that ‘ought’ to be applied to the pedal. But, in the same way as application of force at the pedal can be inefficient depending on the angle of application, there must also be a biomechanical factor to consider. Given the dimensions of femur, tibia and foot; the size (strength) of the relevant muscles; the leverage based on the distance from tendon attachment from joint; there must be optimal loading (pedal driving force) for each point on the pedalling circle; and that force is not likely to be constant.

Assuming this is correct (and, although I don’t have the knowledge to study it in depth, my gut feeling is that it must be correct, because having all the factors cancel each other out is extremely unlikely), my question is whether pedalling efficiency would increase with a pedal-force curve that is not flat, but tuned to biomechanical factors.

Therefore I wonder whether both Frank Day and Andrew Coggan are at opposite points of a spectrum, and the optimum is somewhere in the middle. On the one hand, I doubt that ‘stomping’ is the optimal method, since some smaller muscle groups are underutilised. On the other hand, I doubt that the PowerCrank ideal is optimal, because some of the smaller muscle groups are probably overutilised. (I guess Frank would argue that this overutilisation is a compensatory secret weapon.) This is not to say that PCs are no good; they are probably the best we can do at the moment; but Frank, would you acknowledge that perhaps an improvement is possible over the purely constant-force pedal stroke?

Regardless, it seems to me that a new invention, a ‘PowerPedal’ product, which teaches the body only to apply force perpendicular to the crank arm, would be a useful tool (and maybe more in my price range) which would complement the PowerCranks. But can such a thing be invented? Or has it been already?

It may be worth noting that Shimano’s Biopace eccentric (kind of smashed rhomboid) chainrings were an attempt to accomodate the body’s natural difficulty with pedalling circles. In 1997 I did some test on a compu-trainer using a Shimano “Biopace-HP” 42 tooth chainring and a standard round chainring, comparing heart rate, cadence and power output. At best this was an informal investigation, but the trends I recorded suggested strongly enough that the Biopace (since mothballed and ridiculed) HP chainring actually facilitated identical (or near) climbing velocities at slightly reduced workloads. I used this chainring on my bike at Ironman Canada 1997 and had a good race (10:42:15, good for me)ascending Righter Pass and Yellow Lake pretty easily and having relatively decent legs for the run. I still my “secret weapon” Biopace HP 42 tooth chainring and may use it again now that all the young’ins have never been exposed to Biopace. I wonder… Do you think it really worked?

pedaller. that is an interesting set of points, there. i would not offer resolution, but another couple ideas: 1. the power used in PC pedalling outside stomping is a lot less than the driving stomp. the upper part of the lift around 10:00 is just barely maintaining positive pressure, for example - just enought to keep in synch and out of the way. or at least, it CAN be that way - here are many options of how much or little power you apply so long as it is postive. . . . .except for …

  1. are you familiar with rotorcranks? these devices are causing a little stir in the pro ranks. they use a link system which causes the drive leg to travel 8 hrs of the circle while the recovery leg only goes 4 hrs. you can do this on PC’s, as much or little as you want, also (and also, once your legs are PC trained i think the benefit of this style pedalling would be negligible). i am not sure how this figures into your ideas, other than to say they seem to be enjoying some success, and it goes to show that perhaps, as you say, the final word on pedalling has yet to be said.

Anybody remember the Powercam?

yup. it was a “mechanical oval ring”, as i recall.

Ultimately, and I’m not being sarcastic or condescending here, the reason to pedal in circles is the current norm is that chainrings are round. As Francois (I believe) pointed out the UCI banned non-round chainrings after the Laurent Fignon, Jackie Durant Castorama attempt- about the same time they outlawed the saddle fairings used in the tour that year. So, part of the skill set of being a cyclist, in addition to rudimentary balance, bike handling, etc. is to develop that very counter-instinctive motion of pedalling in circles. My point is, any tool that helps facilitate that skill seems beneficial. Unless you sneak and use Biopace like I did…

Back in the day I used Bio Pace chain rings. The one mistake I thought Shimano made was not making the chain rings big enough. I always felt that that the Bio Pace chain ring allowed you to naturally push a bigger gear than you normally could with a round one. They didn’t make anything bigger than 53, they should have gone up to 54 or 55. They also seemed to market them toward tourist which didn’t help much either. They worked ok for me ridicule not withstanding.

Yup, me too…

i believe the biggest problem with biopace was that you were constantly accerating and decelerating the bicycle. if you ever rode in a group with a dude with them you could see this readily. or, if you ever pulled a burly with them it was equally evident. constant and pronounced accererations would unduly sap your energy, and in the end this would take more than you got from the rings. climbing is slower, and the accerations are lessened - maybe the balance was tipped back in the favorof the rings in this case. . . .

" perfectly distributed torque throughout the pedal revolution. " It has to do with applying the driving force along the tangential of the circle. One would expect the bigger muscles to push harder than the smaller muscles and there are a wide variety of muscles that must be used to push in the many various directions as one goes around the circle.

While it may someday be shown that optimum pedaaling is perfectly distributed torque perfectly aligned to the tangent (a power distribution of an electric motor). I doubt it.

I think it is clear based upon the physics (and reports of users) that simly applying a forward force all the way around, however unequal, is a big improvement over what people have been doing up to now, even what the pros have been doing up to now.

Frank

Dr. Day wrote, “I think it is clear based upon the physics (and reports of users) that simly applying a forward force all the way around, however unequal, is a big improvement over what people have been doing up to now…”

Heck, just getting the non-power leg out of the way on it’s own accord instead of having to assist it at least some, like I was doing, will result in a power increase to the crank. Pulling UP? I hope to, some day!

I gather that the PCs encourage lifting the leg but make no requirement for positive force beyond that. Thus there is still a lot of freedom to vary the actual force at the pedal. Sorry if I misrepresented the product; this only clicked just now.

I think you have gotten to one aspect of the problem even with regular chainrings.

As Tom says we pedal in circles because chainrings are round. Not pedaling in something resembling a circle means that we accelerate/decelerate approximately 160 times a minute.

A wasteful proposition.

i believe the biggest problem with biopace was that you were constantly accerating and decelerating the bicycle.

Are you talking about 2 accelerate/decelerate cycles per pedal revolution? I have trouble grasping how it would be pronounced enough to be noticeable. I can see that the legs themselves would accelerate and decelerate, unless the ankles move to accommodate and keep the legs moving. The part about it sapping your strength after a while – could the issue partly be reduced recovery time for the muscles?

Pedaling researchers are like people trying to dig their way out of a whole and all because they believe
that maximum pedal pressure has to be applied in
the 3 o’clock area. Their other main error was in
attempting to apply tangential force to chainwheel
circle at all times. This has led to all types of
inventions biopace, rotor cranks and the failure of
cycling’s medical experts to solve the mystery
of cycling related lower back pain. Maximum power
to the pedal is best applied in the 1 to 3 o’clock
area using a special toes down technique and by
concentrating on applying tangential force to one of
the pedal axles at all times, you come as close as
is possible to pedaling perfection, eliminating the
root cause of all cycling’s lower back pain in the
process and also making use of maximum combined
arm/leg power possible when riding at speed in the saddle. To prove this, I hope to get a few of the
worst lower back pain victims together and after
some detailed explanation and demonstration, they
should be able to pedal completely pain free next
day, although it will take a year before they will have
fully perfected this special Anquetil technique because the muscles have to get accustomed to
their new workloads. Riders who have been forced
out of the sport by back pain and who are eager to
return would be the ideal riders for this test.

to pedaller. on the biopace acceleration thing - indeed in a tight paceline guys on biopace would always be surging ahead and behind. the rider did not feel it but it was observable to him and to the terror of guys behind him relative to everybody around him. and, as i note, it was almost impossible to smoothly pull a burly trailer, the surging would actually establish a harmonic type deal with the mass behind you and rock the kid to sleep, while you triied all for the world to knock it off so you could actaully get somewhere. those were the days. :slight_smile:

Of course “whole” should have been written as “hole”.

Once again, a post about anqetil that is long on bluster and short on actual specifics.

Please just go ahead and write the book, or ebook whatever and then come back and tell us to buy it. It’s pretty obvious you’re dying for us to ask you for more information.

that allows the Computrainer to calculate the Spinscan. By correlating the instantaneous acceleration or deceleration with the crank position one can cacluate the force on the wheel at that position. Unfortunately, it is the combined force of two cranks. Fortunately, most of the force is on the downstroke so the upstroke can be ignored, which is what they do.

Frank

you simply haven’t ridden a pair. Until you do it is almost impossible to understand.

“Pedaling in circles” means different things to different people and maybe we should be talking about “improving pedaling efficiency” (to increase pedaling power) instead. There are lots of devices and techniques devoted to this end (biopace, rotor cranks, Computrainer, one-legged pedaling drills, PowerCranks, post-it notes, etc. etc.) and the debate should be which one is most effective, not what is the best way to pedal, as a “best way” that is impossible for riders to actually achieve (perfectly even and tangential circular pedaling) is meaningless.

Frank