pealling push up push down

beerco

The man who figures out how to do that is the man who invents the mechanical perpetual motion machine.



Rowers and skiers don't add a lot of power with their arms. If you look at HPV projects, they almost all started out with legs and arms powering the machine (helicopter, cycle airplane etc.). After testing and consultation with the ex-phys crowd, they all switch to legs only. Why do you suppose that is?

Fday

some engineer. Before I went to medical school I was a nuclear engineer in the Navy so, even though it was a long time ago and I have forgotten a lot of this stuff, we are not talking about very difficult stuff.

I guess it depends upon what you mean by one leg balancing the other. What I might ask you to do is a simple energy analysis of the legs through one revolution of the pedal stroke. While it is true that the potential energy of each leg does tend to balance the other (one legs potential energy is increasing while the other is decreasing) the kinetic energy in each leg (most dramatically in the thighs) do not as they are both at maximum (90º and 270º approximately) and minimum (BDC and TDC approximately) kinetic energy at approximately the same time. It takes energy to simply make the pedals go around and the faster they go around the more energy it takes, and this energy requirement varies with the square of the cadence.

The legs may look like they balance but they do not. If you want proof just put your bike on a training stand and take the chain off your bike and pedal at vaarious cadences. I challenge you (or anyone else) to pedal at a cadence above 120 or so without breathing hard.

If you are really an engineer do the energy analysis. When you are done so me the results and if you are right I will apologize to the world for claiming that pedaling takes energy and that the thigh moves back and forth. The math won't lie.

Frank

beerco

I never said that there are no losses do to friction inside the legs, you tried to put those words in my mouth. I don't have to prove anything because I'm not the one making cockamamie statements.

Let's review what you said:

"But the passive weight of the thigh is another. When the thigh is lifted on the backstroke, potential energy is put into it which is recovered on the downstroke."

Which makes sense so far but then you write:

"If Coyle did not account for the mass differences of the thighs in the riders in his study (which he did not) he cannot say who is pushing harder and who is not."

Which doesn't make any sense what so ever.

You're trying to switch topics here when really the onus is on you to prove that lifting the dead leg is somehow better than pushing it up with the working leg. So far, you have not.

Fday

Mr. Beerco,

You should take a deep breath and read a little more carefully what I write. You are confusing two different thoughts.

First, goes to the pedaling forces. Most look at the pedaling forces measured in cyclists and assume that these forces are due entirely to muscle contractions, and from this conclude that all power comes from pushing and none from pulling. I don't believe I have ever seen an analysis in any scholarly journal (or anywhere else for that matter) that mentions gravity playing any role in the development of these forces. Certianly the most referenced article of them all, the one by Coyle,, didn't. If one doesn't account for gravity one cannot know what role the muscles are playing in causing those resultant forces.

Second, the losses I referred to in the pedaling motion have nothing to do with internal friction losses, they are present even if one assumes no internal friction. They come about because of the constant accelerations and decelerations of the legs, mostly the thigh, that require outside energy to maintain since the total energy of the system is constantly changing and there is no way to store and retrieve this energy (if there were the total energy of the system would not be changing). Do the analysis. It is fairly simple to do, albeit quite tedious. I have done it and I know what is going on.

mitosis

So how much power does gravity contribute?

SolarEnergy

Probably because assumptions are made that it doesn't play that much a significant role in pedaling forces.

mitosis

That's what I was going to say to his next reply! The key word in his last post was scholarly. Something his arguments don't seem to be.

Fday

Gravity contributes nothing to the power generated. Gravity only complicates trying to figure out what the muscles are actually doing by looking at the forces on the pedals. You would generate the same amount of power as you do now if you were pedaling in space but the measured pedal forces would be different.

Fday

It could be as simple as no one has thought about it. Most scholarly research should include what assumptions are being made in evaluating the data. It is not valid to assume they are assuming such without such a statement in the paper. Whatever the reason this confounding factor has been ignored in the literature. Even if such an assumption is being made, assuming the world is the center of the universe or is flat or any other assumption doesn't make it so.

n crowley

Independent use of arms and legs in cycling is not very successful as it has the same effect as trying to push and pull with the legs. But when arms and legs are combined and work as a unit results are very different and power is increased. HPV riders are not in a suitable position nor do they have the style of pedalling that's required for combined arm/leg pedalling. In addition they cannot use the gravity effect and that forms part of it.

SolarEnergy

Canada's head coach of the national team, with whom I happened to have done my level 2 in road cycling, also advocates the use of arms, especially while riding TT using aerobars. A bit like (but not as much) when we climb a hill.


I agree. This is a complicated issue.

I am trying to think of a endurance sport, in which there is no recovery. I can't find one. In most sports, there is a recovery phase, that allow :
1 - a short rest
2 - to position the limb for an other stroke
3 - to let the other limb do its job in the most efficient way

In swimming the free style, the recoverying arm must exit the water. It will carry its own weight. Running, skating, rowing...

Makes sense that there is a recovery phase in cycling as well. Like in the other sports, the recoverying limb also carry its own weight.

n crowley

[QUOTE=SolarEnergy]Canada's head coach of the national team, with whom I happened to have done my level 2 in road cycling, also advocates the use of arms, especially while riding TT using aerobars. A bit like (but not as much) when we climb a hill.





Only when the leg power application and arm resistance lines are parallel can most effective use be made of the arms. This cannot happen with aerobars or with the natural pedalling style. You need "Scott Rake" type bars and a very different pedalling style.

beerco

All you have to do is zero the strain gauges with feet on the pedals with muscles relaxed...real tough. I haven't read the Coyle article recently, but to get meanigful power readings you have to have the system read zero under no power conditions, thereby taking into acount any forces due to gravity....sheeesh.




I understand what you're talking about here, but what does this have to do with the claims for your device? The energy to move the thighs still has to be provided by the rider. Why is it better to have a puny hip flexor do it when you've got a big quad down there? Why is it better to use small muscles instead of big? Why is it more efficient to shuttle blood to more muscle than less?

Fday

If it is so easy why don't these researchers "zero the strain gauges with feet on the pedals with muscles relaxed" as you propose? At least you seem to be coming to the conclusion this should be done. Now, you should be asking why don't researchers do so






This (the energy cost of pedaling) has pretty much nothing to do with the claims for my device except as a way of partially explaining the results we see and PC'ers typically lower their cadence. I also bring it up because those who argue against my device frequently say pedaling has no energy cost. They are wrong. BTW, the HF's are not that puny unless you are looking at the aerobic capacity of these muscles, which is generally puny.

Regarding your other questions you are doing a lot of rationalizing to explain your bias. You should instead be asking instead "what does the data show? If the data shows that the use of PC's does improve efficiency (as shown Luttrell for instance) or power (as reported by many anecdotal reports) then you should be asking why is this happenning, rather than arguing that the data cannot be correct. If the data is insufficient as to what PC's do then you should be arguing for more data rather than arguing what you think PC's can or cannot do based on no experience with them and admittedly inadequate data. Theory should change to agree with the current data rather than expecting the data to change to agree with the current theory.