Energy expended during static exercises

[Eric vdm]

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

 

[davenn]

Hi
welcome to PF

(i.e. static hangs from rings or handstands etc.)

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

 

[Dale]

During static exercises the efficiency is zero. So energy is expended to do 0 work.

 

[Eric vdm]

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

 

[Dale]

No energy is required to resist gravity. E.g. a table can hold a book against gravity indefinitely using no energy.

 

[jim mcnamara]

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.