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Energy expended during static exercises

  1. Feb 11, 2017 #1
    Trying to wrap my head around how to calculate the energy/power expended when doing static exercises (i.e. static hangs from rings or handstands etc.) for various intervals...

    How do I relate the impulse (between myself and the rings or surface) to the total energy or work performed in say calories?

    Thanks in advance.
    Eric
     
  2. jcsd
  3. Feb 11, 2017 #2

    davenn

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    Science Advisor
    Gold Member

    Hi
    welcome to PF :smile:

    Work = F x s (s = displacement)
    since there is no displacement, there is no force and therefore no work is being performed

    I'm not qualified to answer what biochemical actions /reactions are occurring in the muscles
    maybe some one else can answer that
     
  4. Feb 11, 2017 #3

    Dale

    Staff: Mentor

    During static exercises the efficiency is zero. So energy is expended to do 0 work.
     
  5. Feb 12, 2017 #4
    Thanks for your reply's.

    I understand in classical mechanics zero displacement = zero work.

    What I don't get is the energy expended in order to resit gravity alone.

    I tried to calculate the gravitational potential energy between myself and the center of the earth...(G.m1.m2/R) but the answer is senseless.

    Confusing o_O
     
  6. Feb 12, 2017 #5

    Dale

    Staff: Mentor

    No energy is required to resist gravity. E.g. a table can hold a book against gravity indefinitely using no energy.
     
  7. Feb 12, 2017 #6

    jim mcnamara

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    Staff: Mentor

    Here is an applet: http://www.juststand.org/OnlineToolbox/tabid/637/Default.aspx

    This applet takes a bioenergetics approach. Straight mechanics, like @Dale cites, is correct if you were a dead blob. Most of us are at least conscious blobs. Humans use food energy, consume oxygen, and generate CO2. Simply doing zero movement.

    This energy consumption is typically stated in exercise physiology and medicine in terms of units called a MET, or metabolic equivalent.. To calculate this using standard Physics is complex to say the least. So measuring oxygen consumption works as a very easily measured and pretty accurate proxy for this energy use.
    There are standards for determining this value, so you can use tables to get an approximate value.

    https://en.wikipedia.org/wiki/Metabolic_equivalent.

    So, simply sitting still, for a 60kg human, uses ~1 MET. Illness or trauma affects this value, for example.
    Exercise machines in gyms, like treadmills, often have an option to enter your weight and show a running estimate of METs as you exercise. Example: Prescribed exercise may expect you to shoot for 3.0 METs, so if you exercise at that rate for one hour you have 3 * 60 = 180 MET minutes.
     
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