Incorporate Pandolf Equation for determining effor while hiking.

[kevingranade]

Is your feature request related to a problem? Please describe.

We have a decent model for mapping exertion to energy expenditure and from there to calorie load and weariness etc, but the input to this model when hiking still ignores a lot of the parameters we have available for fine-tuning exertion.

Describe the solution you'd like

Incorporate details of the Pandolf Equation into our energy expenditure estimation when walking. Article with an overview https://www.outsideonline.com/2315751/ultimate-backpacking-calorie-estimator Short overview of the equation itself.

M = 1.5 W + 2.0 (W + L)(L/W)2 + n(W + L)(1.5V2 + 0.35VG)

Here M is the metabolic rate, which is how quickly you’re burning energy. This equation gives you a value in watts, but that’s easy to convert to other units like calories per hour.

The inputs into the equation are:

W: your weight (kg)
L: the weight of your pack (kg)
V: your hiking speed (m/s)
G: the grade of any incline (%)
n: a “terrain factor” that adjusts the results for different surfaces (for example, a paved road has a terrain factor of 1.0, but a gravel road is 1.2, since it takes more calories to walk on a soft or uneven surface)

[andrei8l]

How does that equation work? I've found other references for it but it does not seem to be valid. It has units of kg + kg + kg*(m^2/s^2 + m/s) (edit: in other terms, it's mass + energy + momentum). Those do not add up and don't convert to Watts.

[Hirmuolio]

That may be intentional.

When human body does "work" it may not be work in physics point of view. For example holding a weight up is non-zero work for us. But from physics point of view the work done is zero.

If you wanted the units to match then those constant multipliers would probably have funny units like J×s/kg/m.

[andrei8l]

For example holding a weight up is non-zero work for us. But from physics point of view the work done is zero.

The work done on the box is zero. The internal work done by your muscles is not zero.

If you wanted the units to match then those constant multipliers would probably have funny units like J×s/kg/m.

There is still an added factor of kg (mass) in there which does not convert to W = kg*m^2/s^3 (power).

[kevingranade]

There's an implied acceleration term from gravity, keeping yourself and your load in an upright position is work that scales with the weight supported, and the efficiency of doing so scales with the ratio between the load and body weight.

If I understand what it's saying, the terms are: 1.5W for metabolic upkeep. 2.0(W + L)(L/W)2 for standing. n(W + L)(1.5V2 + 0.35VG) for locomotion.

[andrei8l]

The original paper (doi:10.1152/jappl.1977.43.4.577) says this for the first term: but isn't as clear for the other two. So it seems like @Hirmuolio was right and every constant is actually c*whatever-unit-makes-it-watts

[actual-nh]

Would this be added to BMR? If so, the 1.5W term may need adjusting downward; I don't have access to the full text of the paper, however, so don't know if a BMR estimate has already been subtracted.

[kevingranade]

I'm not clear about that, based on what I know I would expect this to replace BMR when used.