Wayne Smith writes: > > I was instructed some time ago that the driving force on the > bicycle is not the forward foot pushing down, but the rearward foot > pulling upward. Don't concentrate on pushing the forward foot down, but instead, concentrate on lifting the trailing foot. Now, I, > being a Physics major, have a tendency to apply a bit of Physics. If > you lift the back foot by as little as 5 lbs, then the pressure on > the back petal is reduced by 5#. That 5# is transferred to the > forward foot. Which pushes down on the forward petal by 5# - Net > difference = 10# added to the petal stroke. So for every # of lift > that you pull with the back foot, you get back twice in available > petal force.... The reason bikers are taught to pull up as well as to push down is to make them aware of the pressure the rising foot places on the pedal. You're not actually lifting so much as reducing the amount of pressure being applied, which amounts to the same thing, I suppose. Most bikers don't realize that most of the time they've got one leg fighting the other. Wayne goes on: > I have noticed that when I concentrate on pushing the upward paddle > shaft, The amount of effort to paddle appears to go down and the > speed increases. So, I ask myself why.... I have come up with > this weird set of conclusions... 1) IN order to push, you have to > relax the upper hand. Maybe what is happening is that we are > getting more rest during the stroke? I think that's certainly part of it. I notice that a lot of paddlers appear to be simultaneously pushing with one arm and pulling with the other. That results in a lot of energy expended in merely having the arms oppose each other, since, unlike the bicycle, you don't have the benifit of a fixed pivot connecting the two. By concentrating on the pushing, the opposing arm tends to stay fixed instead of working against the pushing arm. This not only conserves effort but also provides a biomechanical advantage, as the pushing arm is working with a much longer lever than the pulling arm. For a rough estimate of this advantage, assume each hand grips the paddle about one-third of the distance from the end. Comparing the pushing arm pivoting around the opposite arm versus the pulling arm pivoting the paddle around the opposite arm, it appears that the pulling arm has a 2:1 mechanical advantage over the pulling arm. -- mike --------------------------------------------------------------- Michael Edelman mje_at_spamcop.net http://www.foldingkayaks.org (nomadics) http://www.findascope.com (choosing a telescope) *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Fri May 11 2001 - 10:53:28 PDT
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