Originally Posted by stryper
Ever climb a hill so steep that all of your weight on a pedal isn't enough to cause you to go? If you have then you know that you can end up pulling a lot.
Any kind of high output effort (steep climb/sprint) on a bike requires pulling. You can only exert your body weight in force downwards before your body is simply lifted up off the seat. To apply more force you need to pull up with the other foot in order to hold yourself down. Pretty simple stuff
Apart from the fact that I did not say that there is no pulling at all let's have a look at some physics (because reading scientific studies seems to be too much for some)
Let's keep it simple and mostly metric:
Rider A weighs 143lbs/65kg: when does he need to pull because the pedal force is higher than his weight?
CL CrankLength 170mm=0.17m, Cad Cadence 90 rpm, Pi is Pi=3.14..., F Force due to his weight 65kg*9.81m/s^2=638N
that gives us P=1022W
Of course it doesn't work like that because the above calculates it for the force being applied during the whole rotation. Let's assume for the ease of calculation that each leg can apply this force for a quarter of a rotation, that makes in total half a rotation.
Thus the above power value is only the half : 511W
That means without any pulling our 65kg rider can dish out some 500Watts. Not bad considering that this is already 7.7W/kg.
Let's look at a heavier guy 80kg, 175mm cranks, 90 rpm gives us: 647Watts
The 65kg guy at 100 rpm, 110 rpm, 120 rpm: 567W, 624W, 681W
Still not enough of course: That means the 65kg athlete needs too pull. Surprisingly it is unheard of that cyclists (especially) sprinters pull at their handlebars.
And yes of course riders pull, even with their legs, but as I said it's not a lot and it is only in a few situations.
Have you ever ridden with a powermeter? How often and for how long did you climb with more than 500Watts?
Back to the studies, there are a number of them out there. Like the good ole German one from 1998: 8 participants, German national elite track cyclist, 6 of them Atlanta 96 participants. 1!!! of the 8 was actively pulling, no wonder they didn't win many medals.
There are more studies about pedaling technique, pretty much all of them show that even pro cyclist rarely pull during "normal" cycling.
Yes, during a sprint you need to pull, with the other leg, with your hands. And real forum pros that sprint up every hill pull like crazy.
I hope you don't mind that I made your "pretty simple stuff" so complicated.
P.S. If you want to know what's it like to pull all the time try "Powercranks". If you are close to Atlanta be my guest.