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  #941  
Old 01-22-13, 16:57
FrankDay FrankDay is offline
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Originally Posted by coapman View Post
My definition of pedalling efficiency is the percentage torque return from the force that is applied to the pedal. Pedalling effectiveness I would describe as the number of degrees out of a possible 180 that a rider could apply effective maximal force to the pedal. The difficulty for scientists is they are stuck with the one natural technique and they have nothing to compare except for playing around with variations of the same basic technique.
Your definition of pedaling efficiency is the same as those authors definition of pedaling effectiveness (if you integrate it around the entire circle). To most scientists efficiency is refers to energy. Unless you use the same definitions you cannot have a discussion with anyone. You ought to try to bring your use of these terms in line with the rest of the world so the world can understand what you are trying to say.
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  #942  
Old 01-22-13, 17:17
coapman coapman is offline
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Originally Posted by FrankDay View Post
Your definition of pedaling efficiency is the same as those authors definition of pedaling effectiveness (if you integrate it around the entire circle). To most scientists efficiency is refers to energy. Unless you use the same definitions you cannot have a discussion with anyone. You ought to try to bring your use of these terms in line with the rest of the world so the world can understand what you are trying to say.
W are discussing pedalling and power application not how the body reacts to it. Over how many degrees of the pedalling circle is your leg capable of applying maximal force to the pedal ?
  #943  
Old 01-22-13, 17:36
FrankDay FrankDay is offline
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Originally Posted by coapman View Post
W are discussing pedalling and power application not how the body reacts to it. Over how many degrees of the pedalling circle is your leg capable of applying maximal force to the pedal ?
The important thing is not over how many degrees one can apply maximum force to the pedal but what is the average force applied around the entire circle (including the upstroke) since that (when both pedals are added together) is the average power the bike sees and the power a power meter will measure. Your approach is no more worthy than the "just push harder" folks as both of you ignore the rest of the stroke and the power the bike sees is determined by the entirety of the stroke. I mean, really, do you (or anyone in the just push harder group) think it doesn't matter how large the negative forces are on the upstroke as long as you are pushing hard (or hard for a long time) on the downstroke?

In other words, I don't care how many degrees of the pedaling circle I am capable of applying maximum force. I don't care what my peak force is. My main concern is figuring out how to maximize total power delivered or pedaling efficiency or both. I believe that involves both improving "pedaling effectiveness" (getting more power to the bike out of each muscle contraction) and spreading the power application out over as much of the 360 circle as possible even if it is not at "maximum" for much of that circle.
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  #944  
Old 01-22-13, 18:40
coapman coapman is offline
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Originally Posted by FrankDay View Post
The important thing is not over how many degrees one can apply maximum force to the pedal but what is the average force applied around the entire circle (including the upstroke) since that (when both pedals are added together) is the average power the bike sees and the power a power meter will measure. Your approach is no more worthy than the "just push harder" folks as both of you ignore the rest of the stroke and the power the bike sees is determined by the entirety of the stroke.

The difference between my technique and the push harder folk is I push harder for longer over the entire 180 deg., and 90 deg. of this maximal power is giving almost 100 % torque return. Using the (idling) leg in an attempt to increase power output results in an overall loss of power but when you use the idling arm, this situation is reversed. What you are not making clear is, do you attempt to apply power as the pedal rises or do you only unweight in this sector. If you only unweight there, your extra torque can only be applied at the bottom and top of the pedalling circle. From the graph you made available, only minimal torque was applied in these sectors whereas I can apply maximal torque there in addition to the increased efficiency elsewhere.
  #945  
Old 01-22-13, 18:56
FrankDay FrankDay is offline
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The difference between my technique and the push harder folk is I push harder for longer over the entire 180 deg., and 90 deg. of this maximal power is giving almost 100 % torque return. Using the (idling) leg in an attempt to increase power output results in an overall loss of power but when you use the idling arm, this situation is reversed. What you are not making clear is, do you attempt to apply power as the pedal rises or do you only unweight in this sector. If you only unweight there, your extra torque can only be applied at the bottom and top of the pedalling circle. From the graph you made available, only minimal torque was applied in these sectors whereas I can apply maximal torque there in addition to the increased efficiency elsewhere.
Remember, there are 360º to the pedaling circle and the pedal is rising during 180º of that circle. Once the pedal is beyond BDC it is rising until it gets to TDC so anyone trying to "scrape the mud off the shoes" is applying positive force when the pedal is rising even if they are not thinking about "pulling up". Or those like you, because you are starting your "max power" application before TDC are also applying positive force when the pedal is rising even though you are not "pulling up".

I believe that best technique involves "scraping the mud off" well across the bottom and starting the "push over the top" well before the top, and complete unweighting in between, in addition to pushing down with substantial force. Focusing on only a small portion of the circle wastes a lot of potential IMHO.
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Last edited by FrankDay; 01-22-13 at 19:25.
  #946  
Old 01-22-13, 20:52
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Originally Posted by FrankDay View Post
Two points. Crank speed is effectively constant regardless of what the rider does or what chain rings they use (except in the case of Rotor cranks where there is a substantial variation between peak upstroke speed and peak downstroke speed). The reason for this is the mass of the bike/rider and bike speed and the pedaling cadence means there is a large momentum, small variations in forces, and little time to affect speed changes such that pedal speed will remain essentially constant. Another time this isn't quite the case is when on the trainer and the mass of the rider is removed from the equation such that the small mass of the wheel allows for noticeable changes in speed (which can be heard in the whir, whir, whir in the wheel) but even these variations are small at normal cadences.

Regarding efficiency. Efficiency becomes more and more important, eventually trumping power, the longer the rider is asked to ride. This is because energy requirements and metabolism (and the need to refuel) is more important in a race like the RAAM and, perhaps, a race like the TDF or, even, an Ironman. Surely power trumps efficiency in a short track race like the sprint or pursuit but at some point as distances increase efficiency becomes equally important and later more important than power since we are limited in our ability to refuel.
I agree with both those points although for the latter, if one can produce more power I think they will still take it as it means an ability to ride their target pace at an even lower fraction of their threshold (and further spare glycogen stores). Not sure I'd rate it more important but in any case, efficiency is a factor in such events. I thought I originally had a line in there about ultra endurance events in my earlier post but must have deleted it, probably not wanting to confuse my point.

Back to the crank speed thing though - there are still some small variations and someone measured them on the bike riding, both flat and on hills. Will see if I can locate. It was a discussion where the "micro-accelerations on hills cost you a lot of extra energy" hypothesis needed the Mythbusters treatment.
  #947  
Old 01-22-13, 21:06
FrankDay FrankDay is offline
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Originally Posted by Alex Simmons/RST View Post
I agree with both those points although for the latter, if one can produce more power I think they will still take it as it means an ability to ride their target pace at an even lower fraction of their threshold (and further spare glycogen stores). Not sure I'd rate it more important but in any case, efficiency is a factor in such events. I thought I originally had a line in there about ultra endurance events in my earlier post but must have deleted it, probably not wanting to confuse my point.
I think we are in agreement here. For endurance events we are talking about sustainable power. There is one area where we probably differ. That would go to that study that showed that asking the riders to pull up improved effectiveness but decreased efficiency. I would contend that with enough time training the more effective method of pedaling would eventually result in improved efficiency also. That is what is reasonably concluded from Luttrell. Otherwise, I think the scientist is left with the difficult job of trying to explain why effectiveness and efficiency are not both related to power directly (as opposed to having opposite slopes). It is not enough to hae "results". One also needs a mechanism to explain the results that can be used to make correct predictions.
Quote:
Back to the crank speed thing though - there are still some small variations and someone measured them on the bike riding, both flat and on hills. Will see if I can locate. It was a discussion where the "micro-accelerations on hills cost you a lot of extra energy" hypothesis needed the Mythbusters treatment.
Of course there are micro-accelerations, that is how spin-scan works. F=ma. I once thought this might play a role in efficiency. I no longer believe this because they are so small they can be effectively ignored.
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Last edited by FrankDay; 01-22-13 at 21:38.
  #948  
Old 01-22-13, 21:13
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Alex Simmons/RST Alex Simmons/RST is offline
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Here it is - although looking at what I can find, I can't verify if data was from from road rider or trainer simulations (there is reference to "simulated" gear which suggests trainer). In any case, it's still interesting.

From April 2011:

Quote:
Well it just so happens that Eric Lin serendipitously posted some data on the wattage forum to show the difference in micro accelerations/speed during pedaling on flat v steep climb.

As per Eric's post:





Y-axes are speed in meters per second.

Cadence was 70-80 rpm for the
2nd graph in a simulated 39x27 gear and 270-300W.

It demonstrates that the variance between each scenario (in terms of changes of speed during each pedal stroke) is pretty small.

i.e. there isn't a large difference between the amplitudes of speed plots, ~0.03 - 0.04m/s in 0% grade scenario vs ~ 0.035 - 0.045 m/s in the low cadence 10% grade scenario.
  #949  
Old 01-22-13, 21:20
FrankDay FrankDay is offline
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2nd graph in a simulated 39x27 gear and 270-300W.
My guess this is from a trainer ride or an exercise bike, either way a bike with small "momentum" compared to riding on the road and still these changes in pedal speed are tiny. Without these variations tools like spinscan could not work but that doesn't make them important to a rider going fast or slow.
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  #950  
Old 01-23-13, 01:02
JayKosta JayKosta is offline
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Originally Posted by FrankDay View Post
My guess this is from a trainer ride or an exercise bike, either way a bike with small "momentum" compared to riding on the road and still these changes in pedal speed are tiny. Without these variations tools like spinscan could not work but that doesn't make them important to a rider going fast or slow.
====================================
Frank,

I don't understand why you think the variations in crank speed through a rotation are unimportant.

If the crank speed was constant through the full rotation, then the torque would also be constant.

I think that the torque decreases at certain crank positions mainly because the crank speed slows at those locations. Basically the foot/feet doesn't (or can't) maintain enough circular speed to keep a constant torque.

Jay Kosta
Endwell NY USA
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