Improve your pedalling style. The Munich engineer and biomechanics expert Wolfgang Petze calls just about everything into question, ever published about “smooth action”. We explain his method and show how you can use to it improve your technique.
Pedal in a smooth circular style and make sure that all the forces on the cranks are used for efficient propulsion: That is how the well known smooth pedalling action might be summarised. At each turn of the cranks, continuously push, drag and pull - that is how correct pedalling has been taught to date… And it is wrong, says Wolfgang Petzke. His theory is that it isn`t neccessary to concentrate on getting as much force as possible as smoothly as possible onto the pedals, but on improving the action of the legs biomechanically and energetically.
Petzke isnt just saying that, he has studied the sporting cyclists leg and pedalling action like no-one else. The mechanical engineer was always fascinated right from his student days by this bio/technical problem. In the meantime he has developed a testing technique, with which he can tell not only total pedalling power but the magnitude and direction of the forces working on the pedal. He has also programmed software which simulates realistically the complex orchestration of muscles, joints and levers in a cyclist`s leg. Both these techniques together have been given the name Caloped, which has for some years been used in the medical profession, to help patients in rehabilitation relearn muscle coordination and motion. Wolfgang Petzke also offers racing cyclists individual tests, to improve pedalling technique or to eradicate chronic afflictions caused by bad load distribution.
Aim: to have the muscles working together rather than against each other
The revolutionary approach in Caloped is that the force applied to the crank is no longer the main point; it isn`t important, Petzke says, whether the forces are acting in the correct direction, whether the foot is pulling, dragging or pushing. Pretzke rather takes the leg (including hip and ankle joints) as a system and examines how movement and finally propulsive energy results from muscle tension. The trick in his programme is that by using the data from an exactly measured leg and the forces measured on his test pedal, he finds the working balance between each joint (hip, knee, ankle). The software shows this as power at hip, knee and foot. Now he can see if the muscles are working in harmony or antagonism - whether single muscle groups are helping propulsion or even opposing it. It is important to eliminate from the equation, the influence which the leg has, just through its mass and speed during the pedalling action. Other experts agree that this is an improvement over previous methods. Thomas Jaitner - junior professor in motion and training science at Kaiserslauten Technical University says, “The system works very well. The advantage lies in being able to study the reasons causing the motion.”
The idea of uniform pedalling power is wrong … (See complete atricle at URL above)
"The idea of uniform pedalling power is wrong … (See complete atricle at URL above)
What do you think? "
If you mean some concept of pedaling in circles is wrong, then I’d say my impression is that the clear consensus of cycling experts is to apply force when it is most effective/efficient – on the downstroke. Been many threads here on that, as you may know.
Question is how many posts before this becomes all about powercranks and will perfection appear?
I guess I would agree with some of what I read and I also guess I would disagree.
I would agree that pedaling is a complicated system involving many muscles so it is not easy to analyze and perfect.
I would agree that technique does matter
I would agree that, from an energy perspective, it is useful to eliminate (or, at least, consider) the dead weight of the leg from the pedal forces equation although that weight is important to consider in many other aspects in the analysis.
I would disagree that “it isn`t neccessary to concentrate on getting as much force as possible as smoothly as possible onto the pedals”. That is where all the power is generated. I would also note that his diagram showing “good technique” mimmicks what I consider to be a good “pedaling in circles” style. He can complicate this as much as he wants but the forces applied to the pedal are always the result of the addition (or subtraction) of the forces and lever arms of the leg in a gravitational field.
I would be surprised if his technique of: “. . .using the data from an exactly measured leg and the forces measured on his test pedal, he finds the working balance between each joint (hip, knee, ankle). The software shows this as power at hip, knee and foot. Now he can see if the muscles are working in harmony or antagonism - whether single muscle groups are helping propulsion or even opposing it” can actually change anything. I would look forward to seeing how effective his interventions are.
I would agree that, from an energy perspective, it is useful to eliminate (or, at least, consider) the dead weight of the leg from the pedal forces equation although that weight is important to consider in many other aspects in the analysis.
I didn’t read the article, but from a physics stand point, that just seems like a stupid thing to do. Dead-weight of the leg IS a factor in the energy equation. It may not be one that people like to think about because everyones legs weigh a different amount, but it most definitely is a factor. How else can you do a proper evaluation of the energy and mechanics involved if that isn’t considered as a variable?
I would agree that, from an energy perspective, it is useful to eliminate (or, at least, consider) the dead weight of the leg from the pedal forces equation although that weight is important to consider in many other aspects in the analysis.
I didn’t read the article, but from a physics stand point, that just seems like a stupid thing to do. Dead-weight of the leg IS a factor in the energy equation. It may not be one that people like to think about because everyones legs weigh a different amount, but it most definitely is a factor. How else can you do a proper evaluation of the energy and mechanics involved if that isn’t considered as a variable?
Well, it is confusing to most people. When you just look at the pedal forces for most people you see that there are very large forces on the down stroke and slightly negative forces on the upstroke. People interpret this to mean that all the work is done on the pushing part of the stroke and nothing is done on the backstroke, forgetting that substantial work is done on the backstroke overcoming the effects of gravity to get those small forces and the very large forces on the downstroke is as large as it is because of the added effects of the weight of the leg. Even though the forces on the pedals are small on the backstroke (either positive or negative) they are small because the muscles are unweighting the pedals. This unweighting is putting potential energy into the leg as it lifts against gravity. This energy is all recovered as work on the downstroke. If one eliminates the effects of gravity it better illustrates the work the various muscles are REALLY doing. That was what I was agreeing with.
Another major aspect of the mass of the leg that is important but generally ignored as to how it affects cycling is the energy requirements to continually accelerate and decelerate the leg, mostly the thigh up and down, that start to get very large as the cadence gets high.
Similarly, I flap my arms up and down while riding. That unweights my arms, reducing my overall weight by however much my arms weigh, allowing me to climb faster.
Similarly, I flap my arms up and down while riding. That unweights my arms, reducing my overall weight by however much my arms weigh, allowing me to climb faster.
It does? I would love to see your data on that.
What do you think?
That he’s trying to sell you something.
It looks like he has simply outfitted a crank arm with a strain gauge set-up that will give both tangential and radial forces. Whether his method of analyzing these forces is worth anything or not is still to be answered. Depending upon the cost (and reliability that could be a real boon to the academic community and to some of the very top end coaches (and to someone like us) who want to measure this stuff. From the bolt pattern it appears it may just screw into the SRM system which is how it is getting power and could be used to calibrate his system. Since the English pages were not up I couldn’t figure out any details including any cost data. Did you see what the cost is and is the cost for one or two cranks?
You can’t look at it as a system that goes up and down. It’s really two systems, one that goes up and down, and one that works on centripetal (wanted to put in pedal just for the play on words) motion. Both need to be taken into acount, as they affect the dynamics of the system. Looking at it the way you are is an oversimplification of the system, and is not taking into account the full extent to which energy would play a roll.
You can’t look at it as a system that goes up and down. It’s really two systems, one that goes up and down, and one that works on centripetal (wanted to put in pedal just for the play on words) motion. Both need to be taken into acount, as they affect the dynamics of the system. Looking at it the way you are is an oversimplification of the system, and is not taking into account the full extent to which energy would play a roll.
The centripetal motion plays almost no role in the energy analysis since a rotating disk will rotate forever without frictional losses. Therefore, the cranks and pedals and foot can move at whatever speed one wants and the only energy required is the energy it takes to get it up to speed and to overcome frictional losses. However, the further one gets from the foot the less circular the motion becomes. The lower leg at the ankle is moving in an almost circular ellipse where the upper tibia is moving in a very eccentric ellipse, almost an up and down motion. The thigh is a completely back and forth “pumping” motion since the hip is “fixed” at the saddle. In order to analyze any complicated engineering system requires breaking the system down into analyzable components. If you do that you will find that the “up and down” motion of the thigh requires a great deal of energy at high cadences.
Not sure where you learned physics, but the only place that you reach no friction, is in a total vacuum. I don’t disagree that it requires a great deal of energy, but being an engineer here, I’m saying that you’re not looking at the picture properly. If you were in a biomech class, your system would get destroyed for not being complete. You have centripetal motion centered at the center of the crank that needs to be taken into account. There’s also motion at the pedal, because there’s no way you’re going to have someone applying pressure, and have the foot stay in a static relative postion (doesn’t work that way sorry). The way you have it pictured, is more or less a perpetual motion kind of machine, because in your scenario the legs don’t count going down, because they go up. It doesn’t work that way. I think you need to have a good talk with an engineer about this, as your conceptualization of the system is very close, but very far off the mark. Just remember, energy can neither be created nor destroyed. This does not imply that you can ignore it, just that you can’t make up a system to suit your fancy, because it sounds good.
Not sure where you learned physics, but the only place that you reach no friction, is in a total vacuum. I don’t disagree that it requires a great deal of energy, but being an engineer here, I’m saying that you’re not looking at the picture properly. If you were in a biomech class, your system would get destroyed for not being complete. You have centripetal motion centered at the center of the crank that needs to be taken into account. There’s also motion at the pedal, because there’s no way you’re going to have someone applying pressure, and have the foot stay in a static relative postion (doesn’t work that way sorry). The way you have it pictured, is more or less a perpetual motion kind of machine, because in your scenario the legs don’t count going down, because they go up. It doesn’t work that way. I think you need to have a good talk with an engineer about this, as your conceptualization of the system is very close, but very far off the mark. Just remember, energy can neither be created nor destroyed. This does not imply that you can ignore it, just that you can’t make up a system to suit your fancy, because it sounds good.
Ugh, I don’t think you understand what I said. And, I have had a good talk with an engineer about this, me. It is a pretty simple analysis if you break it down far enough. Tedious but simple. It is a lot simpler if you assume frictional losses are zero. If you don’t I look forward to your telling me how you assess the internal frictional losses of the muscles and joints of the legs.
Anyhow. Do the energy analysis of the rider while making the pedals go around at a constant rpm, make the feet go around (assume they rotate however you want), the lower leg to move however you want to describe that movement, and the amount to cause the thighs the way they move. You can also include the potential energy of the various parts if you like. You will find that by far the biggest losses come from accelerating and decelerating the thighs whether friction is assumed to be zero or some other number. This is because the thighs are the most massive part of this system and their change in momentum is the most dramatic. If you look at the total energy of the rider through one cycle of the pedals you will find that it varies substantially, the amount depending upon the cadence (and the anatomic variables). The energy variation in a closed system requires energy to be lost from the system or put into it. Well, the losses are easy to explain, the rider can put them to the wheel, but the increases are not so easy to explain as there is no external input. This means the energy increases must be being generated internally from the muscles. I look forward to your proving me wrong.
Do the analysis and then come back to me if I am wrong.
Frank’s demonstrated his unique understanding on physics many, many times on this forum. you’re wasting your time trying to discuss it with him as it pertains to the real world.
I’m not talking internal muscle/skeletal frictions, i’m talking about the person interacting with the bike, and the bike itself. You may not agree, you may have spoken to an engineer; but your assumption, and theirs is incorrect. I’ve done research in the bio-mechanics field, and I’m telling you that your interpretation of the system is incorrect. You can argue your point of view all you want, but it is still wrong. You can’t just ignore something because it suits your fancy, or makes things easier for you, it doesn’t work that way and leads to improper assumption involving the system in question. What you’re doing is creating a perpetual motion machine where the interaction of the leg with the bike is concerned. Although I wish it were true (and I’m sure that many others do as well), it simply isn’t.
I’m not talking internal muscle/skeletal frictions, i’m talking about the person interacting with the bike, and the bike itself. You may not agree, you may have spoken to an engineer; but your assumption, and theirs is incorrect. I’ve done research in the bio-mechanics field, and I’m telling you that your interpretation of the system is incorrect. You can argue your point of view all you want, but it is still wrong. You can’t just ignore something because it suits your fancy, or makes things easier for you, it doesn’t work that way and leads to improper assumption involving the system in question. What you’re doing is creating a perpetual motion machine where the interaction of the leg with the bike is concerned. Although I wish it were true (and I’m sure that many others do as well), it simply isn’t.
I take it you have misunderstood what I have said. I am not creating a perpetual motion machine because my analysis requires constant energy input to keep the pedals going around (even with zero power out and zero bearing friction loss), the amount of that energy required depends upon the mass and anatomical arrangement of the legs and varies with the square of the cadence. This is probably the major reason that cycling efficiency tends to fall as the cadence gets above 60-80 or so. The energy math is what it is regardless of the bio-mechanics. It is a simple but somewhat tedious analysis. Do the math if you don’t understand.
I’m not talking internal muscle/skeletal frictions, i’m talking about the person interacting with the bike, and the bike itself. You may not agree, you may have spoken to an engineer; but your assumption, and theirs is incorrect. I’ve done research in the bio-mechanics field, and I’m telling you that your interpretation of the system is incorrect. You can argue your point of view all you want, but it is still wrong. You can’t just ignore something because it suits your fancy, or makes things easier for you, it doesn’t work that way and leads to improper assumption involving the system in question. What you’re doing is creating a perpetual motion machine where the interaction of the leg with the bike is concerned. Although I wish it were true (and I’m sure that many others do as well), it simply isn’t.
I take it you have misunderstood what I have said. I am not creating a perpetual motion machine because my analysis requires constant energy input to keep the pedals going around (even with zero power out and zero bearing friction loss), the amount of that energy required depends upon the mass and anatomical arrangement of the legs and varies with the square of the cadence. This is probably the major reason that cycling efficiency tends to fall as the cadence gets above 60-80 or so. The energy math is what it is regardless of the bio-mechanics. It is a simple but somewhat tedious analysis. Do the math if you don’t understand.
It’s that bolded section where you are running into difficutlties. Talk to a civil/bio-mech engineer. I’m telling you that the system that you’ve created is wrong. I say talk to a civil, because they’ll just look at the dynamics involved, and be able to show you on paper where you are running afoul in the determination of your system. I can tell by what you’ve written, that you really don’t understand the forces involved, nor the relationship that force and energy have. It’s not a big deal, but if you’re going to act like you know the physics involved in this determination, at least make the effort to truly know how the dynamics work. It will make life much easier for those who read what you say, and avoid cringing on the part of people who do know how this works.
I’m not talking internal muscle/skeletal frictions, i’m talking about the person interacting with the bike, and the bike itself. You may not agree, you may have spoken to an engineer; but your assumption, and theirs is incorrect. I’ve done research in the bio-mechanics field, and I’m telling you that your interpretation of the system is incorrect. You can argue your point of view all you want, but it is still wrong. You can’t just ignore something because it suits your fancy, or makes things easier for you, it doesn’t work that way and leads to improper assumption involving the system in question. What you’re doing is creating a perpetual motion machine where the interaction of the leg with the bike is concerned. Although I wish it were true (and I’m sure that many others do as well), it simply isn’t.
I take it you have misunderstood what I have said. I am not creating a perpetual motion machine because my analysis requires constant energy input to keep the pedals going around (even with zero power out and zero bearing friction loss), the amount of that energy required depends upon the mass and anatomical arrangement of the legs and varies with the square of the cadence. This is probably the major reason that cycling efficiency tends to fall as the cadence gets above 60-80 or so. The energy math is what it is regardless of the bio-mechanics. It is a simple but somewhat tedious analysis. Do the math if you don’t understand.
It’s that bolded section where you are running into difficutlties. Talk to a civil/bio-mech engineer. I’m telling you that the system that you’ve created is wrong. I say talk to a civil, because they’ll just look at the dynamics involved, and be able to show you on paper where you are running afoul in the determination of your system. I can tell by what you’ve written, that you really don’t understand the forces involved, nor the relationship that force and energy have. It’s not a big deal, but if you’re going to act like you know the physics involved in this determination, at least make the effort to truly know how the dynamics work. It will make life much easier for those who read what you say, and avoid cringing on the part of people who do know how this works.
Why don’t you just tell me where I am “running afoul”. The system being a person pedaling a bicycle. Legs go up and down, pedals go around and around, no requirement to provide any power to the wheel. If it requires no energy to keep the pedals going around then, if we can eliminate friction, we have a perpetual motion machine if the output power is zero. If it does require energy, why?, and where does it come from? I can tell by your criticism that you have never actually done the analysis yourself. Do it, then get back to me.
Edit, as an example of what I am talking about, take the chain off your bicycle and put the bicycle on a trainer. Then ride it for awhile at a cadence of 140 and tell me why your HR is going up.
