- My first impression of the Powercranks was a bit flawed. Their main principle is preventing "resting" (pushing if you like) on the pedal in the up-stroke. Learning to use muscles to lift the foot will increase effective power (theoretically). If the power contribution in the up-stroke remains small (but not negative) it will do nothing to smooth the power curve. This might work, but I'm sceptical. By the way: will this work at all on a recumbent? For me they are worthless anyway since I only ride Mountainbikes. - My own reasoning around the possible benefits of Bikedrive has made my so curious that I just might have to try it. I have my power reading Tacx to check with. Too bad about the extra 400g's. Maybe I can give first hand reports this spring ;).
Loooong message. Sorry about that ;)
/Dick
----- Original Message ----- From: "Frederik Van De Walle" frederixie@hotmail.com To: hpvs@lists.lysator.liu.se Sent: Tuesday, October 22, 2002 5:18 PM Subject: [hpvs] Re: Vevarmar -->pedalling technique
Richard Vizins wrote:
My main objection is that there is (as far as I know) very little
evidence
that even the most skilled proffesional cyclists use more than a small
part
of the down-stroke to produce power.
I disagree :-) I am pretty much convinced that if that was really the
case,
it would be a very bouncy ride!* ;-) Also I know of a clear example where two brothers were doing the final sprint for a race (on lowracers) The one that had the better technique won very easily from his brother, although they had been racing together the whole race. The catch is, he won using
ONE
leg!! And the next year, when the other brother improved his technique, he couldn't even beat him anymore using both.... (I'm sure there are some
other
factors in play here, but still...)
It was this knowledge(from experiments) that initiated Shimanos ill-fated BioPace project. BikeDrive for instance is just another try at the same thing but with a
different approach. Powercranks are very different visually, but really
also adress the same problem. By preventing the cyclist from lifting his up-stroke foot with his down-stroke foot it prevents forces in the wrong direction, thus smoothing the power over the pedal cycle. BikeDrive does the same thing but by storing energy.
I agree and I disagree. The explenation of powercranks is right, but I
think
Bikedrive and Powercranks are completely different issues. Bikedrive in no way punishes wrong pedalling technique as powercranks do! Maybe even to
the
contrary....
Powercranks develops new muscles,
I think that you can actually learn to pull pretty hard on pedals too. During continuous riding, I can keep up the same power only pulling the pedals and relaxing during the push, for quite some time. Sprinting and climbing capacity improve a lot when I have clipless pedals so I can
really
pull....
Bikedrive doesn't require a lot of training and adaptation - which is
best?
Well, as I said before, I don't think very highly of bikedrive and I would like to try out a powercrank, but I wouldn't actually buy it. Yet. I would need to try it first, it's the law of stubborness ;-)
Do any of them make a difference?
Even if there is scinetific 'proof', for me it does not guarantee it works for you, as I believe there is room for a lot of different pedalling techniques for different people. So I say, try it!!! If you buy it, you can always sell it... maybe to see how many people want to get rid of theirs is a better indication if it works ;-)
Cheerio, frederik
*a bouncy ride: a simple calculation:
Let's say we assume 'one-hour record' power: 500W @ 110 rpm equals a
torque
of (500 * 9,54 / 110)= 43Nm average. For one leg this means 21,5 Nm. If
only
during one fourth of the pedal stroke there is effective torque (downstroke), then the torque should be 21,5 Nm x 4 = 86Nm. With a crank length of 0,17m this means an upwardds force of (86Nm/0,17m)=506N or for normal gravity 51,56 kg! So if the assumptions made here were true, the rider has to withstand blows of 50 kg, 220 times per minute!! To me it is clear no such forces exist, because in any aerodynamic position and certainly Boardman's 'superman' position, these forces would be
unbearable.
Of course very simplistic calc, but there should be some truth in it.
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