# How to determine energy dissipated from work applied on a load cell

I am using a load cell to see how much force people can apply on it, to help determine their health.

I am integrating the force applied on the bracket in Newtons in relationship to time, giving me the area under the curve as an impulse in Newton*second

I was wondering if I could transform these results in kinetic energy somehow.

Since no velocity is generated from the exercise (the load cell is bending by a few micrometers), this would mean that I would have zero energy generated, but this doesnt make sense, of course energy must be dissipated from pushing on the load cell.

What is the relationship of the inpulse I measure in regards to energy?

Thanks!

in this scenario, if you are concerned more about the energy of human body that is consumed, then anyway most of that energy is not translated into work.

If you substitute the human body and arms with just the force applied to the structure, then that force is applied and transmitted to the load cell. There is a small portion of work that is translated to dynamic energy (in the sense that the molecular bonds are compressed like springs).

That dynamic energy is only a small portion with respect to the energy that is expended in order to keep the bonds compressed. However, the energy is expended on maintaining the position. The result is that the person applying the force after a while will most likely start to sweat (if the exertion is significant).

Now, in order to associate the impulse to energy (I think kinetic is out of the question), the only way that I can think of is that you need to measure the miniscule displacement of the load cell, and then multiply that displacement with the force applied, that will give you an indication of the work. However, that is not energy, and in reality what you are after should be power (i.e. Energy per unit time).

• And what if I integrate torque in function of time? say I have a bracket shaped load cell and the users are applying torque to it, I get a N*m result multiplied by time. Can thiis be associated to watts? thanks a lot for your answer
– JCSB
Mar 4, 2021 at 22:45
• @JCSB Basically the efficiency of the human body is zero in this arrangement. You might be able to develop some connection between torque and wasted energy, sure, but you would need to measure the wasted energy using some medical tests as kamran says. It might be different for each person, or it might not - if it's not, then you can extrapolate the relationship to new people to estimate their wasted energy too. Mar 5, 2021 at 11:15

This is called Isometric exercise. like pushing against a wall, static contraction.

The muscle length is constant but there is work done by the the muscle due to its contraction.

There are no analitical ways to measure the work done other than measuring the persons vital signs and oxigen consumption.

• There is NO work done by the muscle, energy is only wasted in the muscle's internal processes! Mar 5, 2021 at 11:16