Has anybody ever seen any research on how the power a rider expends in just moving their legs depends on their cadence? This would be with no load, just free wheeling or spinning.
I think it may be small, but a back-of-the-envelop analysis I did last year indicated that it depended on the cadence cubed.
Ted
Nice try shill.
Interesting, I wonder what that means.
It means he is under the impression – since you just registered today – that you are posting merely in order to try to eventually sell something under the guise of a question.
I don’t know what he thinks your are selling, though.
Thank you JoeO.
No I’m just interested in that question because it ties in with a model that I use for estimating the mass specific power (watts/kg) of a runner.
I think the debate relies on whether or not you think there is friction in the muscles.
Take a ride on a set of rollers. The faster you pedal the faster you go so…
Yes, that is probably present, perhaps as a resistive knee-torque. I sort of think that the frictional power requirement is less than the power needed to accelerate the leg-segments up and down.
Last year I and a Ph.D candidate in the UK each build wooden segment legs. Independently, we mounted them on cranks and got them to turn Unfortunately we couldn’t figure out how to hook up a power hub so we could measure the power required to crank the dummy legs around.
I’m not sure what he tried, but I couldn’t figure out a way to drive the back wheel of my “lab” bike (with the dummy legs) with a second bike equipped with a power hub. Basically, I couldn’t figure out a way to lock the back wheel hub of the “lab” bike so it would not coast.
Take a ride on a set of rollers. The faster you pedal the faster you go so…
Absolutely. I am just curious as to how much of the input power is spent on rotating the legs. That helps me solve another regarding a runner power expenditure for leg swing.
I assume that the rest of the input power for a rider goes into other activities.
since the riders legs are connected, the power to move them would be zero, assuming no musculo-skeletal friction and no wind resistance.
for a runner that wouldn’t be the case, as he would have to fight gravity on the way up each time.
I guess it is easy to add the cost of lifting to whatever you find out from cycling though?
There must be a cadence, above which, neuromuscular power output degrades relative to oxygen utilization.
It is probably due to 2 factors: the ability of the muscles to contract that quickly…at some speed you transition from slow twitch fibers to fast twitch…
and second, the ability to turn off the opposing muscles when turning on the other (quads/hams or hip flexors/glutes).
But I have never seen anyone suggest that it has been quantified.
since the riders legs are connected, the power to move them would be zero, assuming no musculo-skeletal friction and no wind resistance.
Yes, the legs are connected so the gravitation factors would cancel each other out. I think that there is another issue: the acceleration and deceleration of the (upper) leg segments as they pass through the top and bottom of the crank cycle.
Just to argue on the basis of contradiction: If it took zero power to move the legs through the crank cycle, then there would be no limit to the cadence. A spinner with zero-drag could pedal at any cadence without limit. I don’t have data on that but I would guess that it might not be possible for a sinner to spin at more than 300 rpm.
Has anybody ever seen any research on how the power a rider expends in just moving their legs depends on their cadence? This would be with no load, just free wheeling or spinning.
I think it may be small, but a back-of-the-envelop analysis I did last year indicated that it depended on the cadence cubed.
Ted
Frank? Is that you?
No.
see…your problem is there’s this guy. He used to hang around here a lot. And argue with these other guys. About a lot of things, but among them the fact that the kinetic energy required to accelerate the legs wasn’t returned…and he was trying to sell something. Being wrong and trying to sell something at the same time usually ends poorly.
Lol I was thinking the same thing as to the reference of the “other” cranks
.
You sure sound like you could be his sock puppet…
Wow. I find that interesting. I guess his goal was commercial gain.
I’m just a runner with a math/physics background who is interesting in figuring out a way of estimating a runner’s energy expenditure. As I think I mentioned above, there is a similarity between the runner and the rider in terms of the power required to accelerate and decelerate their legs. I can’t do it for a runner, but I think it can be done in a lab for a set of legs attached to a crank.
In a way I am surprised that nobody has published anything on this subject.
Thanks,
Ted
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