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  1. #8
    Join Date
    Dec 2015
    Wilton Street Glasgow

    Re: Venous foot pump


    So for calculating angular acceleration (ac) we have ac = v x v/r This means that if an individual has a leg length of 0.7 m and is walking at 1.5 m/s then the angular acceleration is 3.2 m/s . Thus for the stance leg during gait the force acting on the column of blood at the ankle is not just gravity x mass , as has previously been the assumption but gravity plus angular acceleration giving a total force of about 13.2 x mass .

    Now , after toe off , the reference foot undergoes rapid acceleration , quickly reaching a velocity which allows it to catch and pass the body , so that it is in place for the next cycle . So let's say the reference foot reaches 3 m/s during the swing phase , so that gives an angular acceleration of (3x3) /.7 = 12.8m/s/s
    So the force applied to the venous valves at the ankle by the section of the column of blood immediately above is the mass of the blood x 22.8 ,not mass x 10

    That's a big difference compared to what was originally thought .

    What about running at say 3m/s ? During the swing phase that would give a foot velocity of about 6m/s . So angular acceleration = vxv/.7 = 51 m/s/s

    So for our section of the column of blood , that gives a force on the valves of mass x 60 . Not mass x ten (gravity only ).

    So with regard to venous return during gait , when you add the centrifugal effect into the equation ,in addition to gravity , you can see how vital the foot and calf pumps are .

    Last edited by Gerrard Farrell; 03-11-2019 at 08:41 AM.

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