New subject: Vevarmar -->pedalling technique

15 Oct 2002


      Hej hej,
My name is Frederik and I have been trying to read along with your Swedish 
mailing list, sometimes very interesting. BTW, I'm from Belgium and I study 
at KTH in Stockholm in an international program in English, jätte trevligt 
:-)
Anyway, I have an 'opinion' on all the Bikedrive, Biopace stuff and even 
short and long cranks for that matter. I think, if these alternative systems 
have any gain, it is from making better use of the pedalling technique the 
cyclist uses. With this I mean that, if there is a gain with these systems, 
it is not because they are 'wonder' system of mechanics by themselves, but 
of adaptation to the individual biomechanics (=the pedalling 
style/technique).
To remind: P = F x V or P = F x L x C
   with
  P = power
  F = force on pedal in circular direction
  V = speed of the pedal
  L = Length of the crank
  C = cadence
I think a effective pedalling style on traditional cranks can be quantified 
as followed:
A The force on the pedal is always in the direction the pedal moves
B Good use is made of the circular momentum of the spin to smoothen out peak 
forces and to overcome the upper and bottom dead points
C The cadence is so that you can apply all your force without discomfort and 
as such that you can still keep good technique from A and B.
If this pedalling technique of a certain rider is not good, we are offered 
two options:
- Change the geometry of the movement
- Improve your pedalling technique/ style
Now take Biopace and Eggrings etc. this is a classical case I would say of 
adapting the geometry to the cyclist. From a pure mechanical point of view, 
there is no reason to believe that one or the other is better if your style 
is good. But, if it feels better and more fluent, than it is probably better 
(usually if you like to excercise a lot of force in the downward stroke).  
So this could improve point B for some people.
Length of cranks. Basically, if you shorten the cranks (L), you have to 
increase your cadence C to keep the same power P. And the other way around. 
So you can use this to change cadence. Since most recumbent cyclist find it 
difficult to keep a high enough cadence, shorter cranks could be a solution 
for a better pedalling technique with more 'momentum'.
So you can use this to influence point C for a better pedalling technique.
Bikedrive is a difficult proposal to say something about. In a way it is 
similar to eggrings or biopace, with the difference that when you load the 
spring with a certain force F, it coincides with a higher momental speed V 
and when the spring unloads, it coincides with a reduction in speed. 
Basically this effect seems comparable to riding a bike with not enough 
stiffness in the chain line of the frame, but with less actual losses as a 
frame would have. I personally find this effect very unpleasant... but I can 
imagine it could work for some people. Some ;-)
Powercrank is very interesting, because it addresses a major flaw in the 
pedalling technique of most cyclist: in the backstroke the leg gets lifted 
by the opposite pedal, effectively having force in the wrong direction. I 
think everyone should at least try a powercrank-equipped bike. So this can 
improve point A for a better technique.
I think my point is, the importance of an effective pedalling technique and 
possible improvement of it seems to me not often mentioned in general. The 
way you pedal seems to be accepted as a fixed fact. Pedalling is more 
complex than just pushing down. Also, our leg is sometimes too easily 
compared with a piston(engine), forgetting we can also exert considerable 
power in the other stages of the pedal stroke.
Some literature I once read, said that the force we think are using to pedal 
is not necessarily in the instantaneous direction of movement of the pedal, 
although we think it is. Together with the backstroke this is what I suspect 
could be the main cause for lost efficiency of the pedal movement.
Ideal to improve your technique would be to be able to measure the actual 
forces on the pedal real time and so adjust your technique.
But more realistic, I would recommend the following tips that, I think, 
could possibly be way more effective than the costly wonder solutions like 
Bikedrive can give:
1 Get used to SPD or any other fixed but quick releasing link!! And use 
them. Without it, you HAVE to push in the wrong direction of the backstroke 
to keep your foot on the pedal. This IS BAD for efficiency!! Avoiding this 
can be practised then by pedalling with one foot.
2 Experiment now and then with different cadence.
-	Very low cadence so you can focus on pushing in the right circular 
direction, also pulling/pushing your leg up and down on a recumbent.
-	Very high cadence to get used to making a very fluent movement, not just 
in circles but also with constant pedal speed (no peak forces of bouncing in 
the saddle)
3 Our mind and feeling has some delay. So instead of thinking of pushing 
your foot forward when you are already doing it, think of pushing when you 
foot is going up. Similarly, think of pulling down in the top position, 
pulling back in the forward position, pushing up in the lowest position of 
the pedal. You could say a 90 degree advance thinking is needed. This cannot 
be solved with any crank trick, so if you get this right, your power can 
go up seriously without using more effort.
Of course this is only my experience. I usually think of pedalling technique 
when I have a little down in average speed. And usually just thinking about 
it raises my speed with 2-3 km/h :-)
Anyway, I hope this was of some help,
Frederik
P.S: I will soon regain recumbent mobility, so if anyone in the 
neighbourhood would like to go for a spin I live in Upplands Väsby, near 
Stockholm. You can call me on 070 469 7210
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Re: Vevarmar -->pedalling technique