[pct-l] The meaning of walking model

[Joe Roth]

I agree

On Tuesday, March 6, 2012, Yoshihiro Murakami <completewalker at gmail.com>
wrote:
> Dear American hiker
>
> I am re-thinking about the Dynamic walk model, which was an expanded
> mathematical theory from the inverted pendulum mode.
>
> Kuo, A.D.  2007  The six determinants of gait and the inverted
> pendulum analogy: A dynamic walking perspective. Human Movement
> Science, 26, 617-656.
>
> I am not specialized in Ergonomic, so I may misunderstand the meaning
> of theory. But, I think this model describes important aspects of
> hiking.
>
> The energy consumption is predictable by the simple mathematical
> equation as follows:
> WR =1/8 f^3 s^4
> where WR is work rate, f is normalized step frequency, and s is
> normalized step length. WR is indicated as W/kg in in other pages. So
> I think WR is energy consumption per 1kg body weight.
>
> The prediction by the model:
> The energy consumption per 1 kg body weight is proportional to the
> third power of the step frequency and the forth power of the step
> length.
>
> The influence of step length is larger than step frequency. Then we
> should increase step frequency when we want to walk fast as like
> long-distance runners.
>
> The dynamic walking model is based on the weightless legs. In reality,
> the energy consumption increases by the twist of the waist and the
> movement of the legs. So, there is a upper limit to the step
> frequency.
>
> WR expresses energy consumption per 1 kg in weight. Then,  for
> example, the total energy consumption is estimated by very simple way.
>
> When your body weight is 70kg, the energy consumption is WR x 70, when
> your body weight is 60 kg, the energy consumption is WR x  60, ...
>
> When you carry 20% body weight backpack, your body weight increases as
> 1.2 times. Then the energy consumption is WR x bodyweight x 1.2.
>
> If you want to walk with 20% body weight backpack by the same energy
> consumption to with no backpack condition,
> Assuming :
> step frequency is constant f,
> step lengths are s0, s2, for each condition,
> The energy consumption of no backpack condition is
> WR =1/8 f^3 s0^4
> backpack condition is
> 1.2 WR = 1.2 1/8 f^3 s2^4
> When you want to walk same energy consumption of both conditions,
> 1/8 f^3 s0^4 =1.2 1/8 f^3 s2^4
> Then, s0^4 = 1.2 s2^4
> s2 = 0.956 s0
>
> That is:
> When you carry 20% body weight backpack, and when you set your step
> length to 0.956 times of your step length with no backpack condition,
> your energy consumption of backpack condition became equal to the no
> backpack condition.
> (Sorry, it was difficult to translate. please guess)
>
>
>
>
> --
> Sincerely
> --------------- --------------------------------------
> Hiro    ( Yoshihiro Murakami  村上宣寛 )
> facebook  http://www.facebook.com/completewalker
> Blogs  http://completewalker.blogspot.com/
> Photo  http://picasaweb.google.co.jp/CompleteWalker/
> Backpacking since about 1980 in Japan
> JMT, 2009, 2010, 2011(half).
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