Is it true that the "round pedalling stroke" is a myth?

Discussion in 'Cycling Training' started by dominikk85, Oct 29, 2012.

  1. dominikk85

    dominikk85 New Member

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    Hey guys, I'm new here. I recently re-started road cycling after doing some track cycling in my teens. now I'm 27 and want to shape again.

    I have a question regarding pedalling.physics dictates that only forces perpendular to the crank generate propulsion. cycling books (at least the ones not older than 20 years old:)) devide the stroke in 4 phases: the push down, pull back, lift up and kick forward phase. my track coaches told me that too and emphazises pedalling with "souplesse" and it makes a lot of sense because you use the full circle.

    http://www.cycle-faster.com/pedaling-technique

    however know I have read that several studies were done with real elite cyclists (I think persuiters) which showed that the generate little forces in the kick forward and paw back phase and even negative force (means they don't even lift their whole leg weight) in the lift phase.

    can it be possible that elite riders have ineffitient strokes? what is the reason for that? or would even better athletes (say armstrong or indurain) have better pedalling?
     
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  2. daveryanwyoming

    daveryanwyoming Well-Known Member

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    Pedaling studies with force measuring pedals show that all riders have distinctly non circular pedal strokes when it comes to application of force and subsequent torque production. Nearly all the torque and power from it is generated during the downstroke. That might 'feel' like circular pedaling but when measured it definitely is not.

    The 1991 Coyle study involved national level and state level time trial specialists and although none of them had what might be called circular or even force application throughout the pedal stroke, the faster riders had even less force application outside of the down stroke. Here's a chart showing pedaling torque from that study:
    [​IMG]

    The folks with the higher peak and lower torque generation during the upstroke were faster than the folks with the lower peak downstroke torque and more lifting on the upstroke.

    I wouldn't conclude that somehow faster riders just happen to be inefficient. More likely that the bicycle as a machine doesn't reward us much for even application of torque all around the pedal stroke and that perhaps it's that bit of rest we get during each cycle that allows us to generate more power through the downstroke phase.

    Bottom line, as much as it seems like common sense and is steeped in tradition, circular pedaling isn't all that important as long as you're smooth enough to get your feet out of the way during the upstroke so you're not actually fighting yourself. But beginners probably have to learn even that bit and many folks struggle and bounce at higher than normal cadences so some attention to pedaling probably makes sense for folks who's events demand a wide useable range of leg speeds and cadences (e.g. track racers or crit sprinters) but don't expect a big return in sustainable power after investing a lot of time devoted to developing a circular pedal stroke.

    -Dave
     
  3. dominikk85

    dominikk85 New Member

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    thanks. there was a study with german national team persuiters that had the same conclusion a few years ago. so it seems to be true that no one has the "round pedal stroke". although by physics the round stroke should be better.

    Maybe physiology is here more important than physics. one explanation that I have is the hamstring muscle. it not only flexes the knee but also extends the hip. so riders might use the paw back and lift phase for relaxing that ham so that it can support the glute and quad in the downstroke. but this is just a theory of course I don't really know.
     
  4. dominikk85

    dominikk85 New Member

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    BTW is it true that "ankling" is not recommended anymore? back then they told you to lift the heel at the bottom and lift the toe before/at the top.
     
  5. daveryanwyoming

    daveryanwyoming Well-Known Member

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    Yeah, I'm not sure anyone has shown the 'why' behind a more pulsed pedal stroke just the consistent observation that well trained and very fast cyclists do not spin round circles. Some folks have speculated that there are clues in contrasting 'ramped' vs. 'ballistic' muscle contractions with the latter being closer to how we pedal. But I suspect you're right, we're not machines and physiology seems to trump simple mechanical models of what 'should be' most efficient vs what actually is most efficient.

    -Dave

    P.S. the gizmo crank folks should be dropping by soon to set us all straight and show us the error of our naive thinking ;)
     
  6. tonyzackery

    tonyzackery Well-Known Member

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    FWIW, I believe pedaling in more of a circle (not necessarily an exact circle) as being advantageous is not a myth. Case in point, I started this fall's indoor TT season on 172.5s and noticed a drop in power to the tune of about 25-30w. Put the 170s back on, and voila - there's the power. My peaks aren't as sharp, but for a time trial I don't need them. With my highly sensitive nerves sending signals, I've eliminated a small, but perceptible 'dead spot' in my pedaling action. More power throughout the entire revolution is something to strive for, but not obsess about or think can be accomplished via training with a magic pill (or new set of cranks/img/vbsmilies/smilies/duck.gif).

    Good call, Dave, with your post script. I'm getting out of this rabbit hole of a thread now, while I still have my loafers on because, with experience as my guide, hip waders will soon become required gear. Anyone hear Frank's footsteps???/img/vbsmilies/smilies/wink.gif
     
  7. jpr95

    jpr95 Active Member

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    I can't say much about applying force throughout a circular pedal stroke, however, I think it is advantageous to train your legs to move your feet in circles while pedaling, instead of just trying to push in a linear fashion, as you would doing squats on a weightlifting machine. If nothing else, it's to develop a smooth pedaling motion, without causing the bike to flop all over the place such that you have to fight it with your arms, wasting energy on non-forward motion.

    What I can say about that application of force is that your strongest leg motion is pushing, so it makes sense that the most force on the pedal is in the downstroke.
     
  8. gudujarlson

    gudujarlson New Member

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    What physics suggests that pedaling in circles is more efficient? As long as you are not pedaling backwards during the upstroke, I don't see why it would change energy loss in the system to apply torque unevenly through the cycle. Where would the energy escape to? Heat? Why would uneven torque cause more heat? The only thing I can think of is heat loss caused by the deformation of the shoes, but it's very unclear whether that would increase with uneven torque to a great enough degree to make a noticeable difference. I just don't think physics is going to be much help here. If there is any difference, it's probably something to do with human physiology; something which physics provides very little understanding because of the sheer complexity of the problem. Of course I've never been wrong about anything before. ;>
     
  9. dominikk85

    dominikk85 New Member

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    Well I was not talking so much about the uneven force generation but about the thing that only forces perpendicular to the crank result in propulsion. forces along the crank just deforms the crank. So if you just push down you have a lot of forces used to deform the crank (it actually won't deform a lot of course).
     
  10. frost

    frost New Member

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    Probably for that good reason the angle of the (peak) force application is quite small.
     
  11. gudujarlson

    gudujarlson New Member

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    Ah ok. I'm not skeptical that non-tangential forces do no useful work. Pushing straight down with your foot when the crank is pointing straight up won't turn the crank. I think I misread your post the first time. Sorry. However, I will say that the physics does not say much about efficiency in this situation. If you replace the human leg with a rock, there is no energy loss. The energy loss in the human leg case comes from the the way muscles work, i.e. physiology. In any case, you can ignore me as I have added little to this discussion. :)
     
  12. dominikk85

    dominikk85 New Member

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    no you added definitely. everyone is welcome to answer:). my point is that if you push straight you only have 100% efficiency at the 3 o clock position. you still have relatively good efficiency over a larger sector but still only a relatively small part of the circle.

    On the other hand this sector is of course the by far most powerfull position of the stroke while the leg is not good at creating perpendicular crank force in most other parts of the sector (especially around the two "dead spots" at 12 and 6).

    So maybe it indeed make sense physiologically to save your energy for the push down phase instead of applying "real" (perpendicular force of course you also apply other forces over a larger sector) force over the whole sector.

    I still like to at least try to have a "round stroke" (i.e perpendicular force as much as possible) because it at leasts prevents me from applying stupid wasted "stretch the crank" forces. so maybe trying to round the stroke at least adds a slightly better force sector or at least prevents breaking forces. so I think trying to pedal "round" is still a good goal as long as you are not wasting too much energy in the dead spots when you won't generate a lot of force anyway (so rather a rather smooth "scrape the mud" (to use greg lemonds words) movement instead of trying to pull like crazy.
     
  13. jpwkeeper

    jpwkeeper Member

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    I suspect the "scrape the mud" portion of the pedal stroke is helpful not so much for the amount of direct force it applies, but because it assists the upper foot during the most oblique portion of the downstroke (as in, from 11 to 2) where it's difficult to apply any power since your leg is pretty much directly above it. Without that, I suspect there is a decline in angular velocity right at that point.

    I would think that elliptical chain rings would also mitigate this.

    If the graph shows the pedal power of a single crank (and I think it does), this assist from the opposite foot would cause a decrease in power through that portion since the one leg isn't working quite so hard at such an awkward angle.

    Does the same place you found that graph show the power applied by the combined cranks compared to a less elite rider?
     
  14. vspa

    vspa Active Member

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    its not a myth and it is often overlooked, much like breathing exercises,
     
  15. frost

    frost New Member

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    Neither of those have very good support in scientific literature, which in my language makes them myths or "earth is flat" category.
     
  16. ambal

    ambal Active Member

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    Pedaling in circles is one of the biggest scams to penetrate cycling, it's almost on the same level as the need to be 'strong' and go to the 'Gym'..... for god sake show me some legitimate data. I'm sick of riding with people who preach this crap.
     
  17. vspa

    vspa Active Member

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    it is technique, maybe it cannot be measured, i don't know really, i just know how important it is for a cyclist, in your next ride just select a big gear and at the 6 o'clock position pull with your gastrocnemius muscle backwards until the 9 o'clock position, if you stand on the pedals then pull up until the 12 o'clock position, another test is to ride a fixed gear bike on the track, if you have access to one, it will depurate your pedalling quite a lot, just try it, if you are drop on a climb and riding in the red zone you need to control your breathing first, before attempting anything else, you can see also how the guys breath in the starting ramp of TT, you concentrate on that too,
     
  18. dominikk85

    dominikk85 New Member

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  19. daveryanwyoming

    daveryanwyoming Well-Known Member

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    Yes, it's very common sense as are many things steeped in cycling tradition. But that's exactly the kind of thing sports science try to sort out via structured studies and both of the long held traditions you've mentioned have been studied and found wanting. Healthy humans are not limited by lung volume or depth of their breathing (sure an asthmatic or someone with COPD but they're not really the target cycling athlete) nor do highly skilled racers pedal 'in circles' no matter how appealing those ideas sound or how solidly they exist in cycling tradition.

    Spend some time on pubmed and you can find studies on both topics.

    -Dave
     
  20. dominikk85

    dominikk85 New Member

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    yes. however if you ask each of those tested cyclists whether they pedal in cycles almost anyone would say yes. that they don't actually pedal in cycles does not mean they are not trying (because anyone is taught to cycle like this).

    the same is true for baseball players. any LL coach says swing down or level (and don't uppercut) and any MLB player will say in interviews that he swings down however high speed videos shows that pros actually swing up a little to hit the ball.

    so the "wrong" teaching can still lead to correct mechanics.
     
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