[Hannah LS (OP)]

Nur asks:

What is the energy required when someone is chopping meat?

What do you think?

[Bored chemist]

If this
https://www.sharecare.com/health/calories/how-calories-burn-doing-housework
 page is right then we use "150 Calories per hour while cooking,"
which seems a fair estimate for chopping meat.
Obviously it will vary from person to person and also with the job.

Depending on what you plan to do with the data, it may make sense to deduct the roughy 100 Calories per hour you use even if you do nothing much.

[alancalverd]

A butcher's assistant probably expends about 60 calories per day cutting meat.

[evan_au]

A paleobiologist(?) investigated how much energy you gain by processing meat in various ways.
- As I recall, they used goat meat in their experiments...
- You get almost no calories from (trying to) chew on a slab of raw goat meat
- You extract a lot more calories by chopping raw goat meat into pieces small enough to swallow
- You extract far more calories again by cooking it before eating

So, overall, chopping meat releases energy!

[Bermendy88]

How many calories lost for a normal person?

[alancalverd]

Nothing abnormal about paelobiologists or butchers' assistants! My estimate was based on about 7 hours of actual cutting and dicing with professional knives. In a domestic kitchen, you might spend 10 minutes dicing enough meat for 3 or 4 people, maybe 1 - 2 Calories allowing for a relatively blunt knife and lack of skill.

[Bored chemist]

Cutting meat is probably one of the more energy intensive bits of cooking but...
People use about 150 Cals per  hour while doing that.
So 7 hrs would be about 1000 Calories
And yet you think "A butcher's assistant probably expends about 60 calories per day cutting meat.".
That does not make a lot of sense.

[syhprum]

Provided volunteer butchers were available how could you go about measuring the calorie consumption of their days work cutting meat.
It seems rather a problem to me with all the variations you would have to allow for the only solution I can visualise is to make force and distance measurements on the tools they use and add in the efficiency of the human body as a heat engine (25% ?) .

[Bored chemist]

It's difficult to assess the efficiency of the human as a heat engine.
One way to do it would involve a bunch of butchers...

You measure how much oxygen they consume.
And/ or, you measure how much food they eat

[alancalverd]

As BC pointed out earlier, the quiescent consumption of a human being is around 100 calories per hour. The most extreme physical labour corresponds to a useful output of about 100 watts but few people can maintain that for more than an hour at a time, the probable world records being held by cross-channel manpowered flight pilots, who were champion cyclists able to maintain 200 W for an hour. Cutting meat uses the arm muscles, which are far weaker than the legs. 10W of useful work is pretty good for a day's duration.

10 Wh = 36000 joules = 8.6 Calories

You can do the measurements several ways. Measuring oxygen consumption isn't particularly easy as you have to analyse the exhaled gas, which still contains a lot of oxygen. Easier to measure exhaled CO2. You can simulate the task with ropes and paddles in a water bath and measure the temperature rise of the water, or use a dynamo load and measure the work electrically. Maybe put a force transducer and accelerometer in the knife handle.

[Bored chemist]

The most extreme physical labour corresponds to a useful output of about 100 watts

You have lost a zero there

Peak powers can exceed a kilowatt
75Kg of me can climb 2.7 metres of stairs in 3 seconds. That's about 600 Watts.
Believe me, I'm no athlete

the quiescent consumption of a human being is around 100 calories per hour.

No It's about 100 Calories per hour (note the Capital C indicating the "great calorie")
That's about 420 KJ per hour
About 120 Watts- doing nothing much but staying alive.
So, what you are saying is that a butcher's assistant is only producing 8% more energy doing their job than just sitting round.

Now, if this site is correct
https://www.fitnessblender.com/articles/calories-burned-by-occupation-how-many-calories-does-my-job-burn
a cook would burn something like an additional 1000 Kcal per day.

That means that actually standing up, doing stuff like cooking increases your throughput by something like 40%

Where's the other 30% or so going.

Measuring oxygen consumption isn't particularly easy as you have to analyse the exhaled gas, which still contains a lot of oxygen. Easier to measure exhaled CO2.

Or, equally
Measuring CO2 consumption isn't particularly easy as you have to analyse the exhaled gas, which now contains a lot of CO2. Easier to measure exhaled O2.

It's not especially easy  either way.
I know I can make an O2 sensor out of a zinc air battery- I don't have a CO2 sensor- so I know which option I'd choose.

If I found that someone doing a physical job that involves standing up was only using another 10W, I'd get someone else. Just standing up* burns a couple of Calories per hour - that's most of the 10W.

* there's lots of stuff about Calories burned using sit/ stand desks.

[alancalverd]

It is true that weightlifters can generate a kilowatt for a few milliseconds, and I've no doubt that you expend 600W hauling yourself up stairs.  But there are a lot of confused quantities there. The question implicitly concerns useful work done by the arms alone, over an extended period. Can you run upstairs at the same speed continuously for 7 hours? You would have climbed Everest before lunch!

Professional cooking involves a lot more than standing still and chopping meat. As a bakery worker, I shovelled coal for 30 minutes 3 times a day (ee, it were a proper bakery - none of your gas and steam stuff, lad), carried a hundredweight of loaves or cakes from the bakehouse to the shop twice an hour, and heaved the said stuff in and out of the ovens as fast as we could sell it. Chopping the odd bit of meat to fit it into the mincer (100 meat pies every lunchtime) was probably the least strenuous part of the day.

Quoting from your reference

This activity, along with energy required for bodily function, adds up to a total of 127.5 calories burned per hour,

So if we subtract 100 Cal/hr "bodily function", we get 27.5 Cal/hr = 32 watts of useful work for a moderately strenuous job pretty much as I said in the first place.

[Bored chemist]

The question implicitly concerns useful work done by the arms alone, over an extended period.

Remind me which bit of "What is the energy required when someone is chopping meat?" mentions arms.
My best guess- and in the absence of any other information, we can only guess,  is the the OP wants a rough idea of how many calories he might burn while doing this.

Chopping the odd bit of meat... was probably the least strenuous part of the day.

Maybe, that's because a butcher's assistant has done the hard work of hauling the carcass around.

So if we subtract 100 Cal/hr "bodily function", we get 27.5 Cal/hr = 32 watts of useful work for a moderately strenuous job pretty much as I said in the first place.

 

A butcher's assistant probably expends about 60 calories per day cutting meat.

Yeah... sure... everyone works a 2 hr day.

[chiralSPO]

It's not especially easy  either way.
I know I can make an O2 sensor out of a zinc air battery- I don't have a CO2 sensor- so I know which option I'd choose.

I would opt to measure CO₂. You can quantify it fairly easily using an IR detector (once adequately calibrated), and even if the detectors themselves were equally sensitive, measurements of produced CO₂ are inherently more sensitive than consumed O₂ because of the change in concentration relative to baseline: the atmosphere is about 21% O₂ and 0.04% CO₂, and because CO₂ and O₂ have a roughly 1:1 correspondence in the stoichiometry of metabolism (depending on how much of the fuel is carbohydrate vs fat) one could expect that the amount of metabolism necessary to double the concentration of CO₂ in the atmosphere would only decrease the concentration of O₂ by about 0.2%. If I were looking for slight changes in atmospheric composition by looking for a 100% increase in one value or a 0.2% decrease in another I know which I would chose to measure...

[Bored chemist]

It's not worth worrying about the precision of the sensors.
Calories derived from fat, sugar or protein correspond to slightly different oxygen consumptions.
And there's also the contribution from gut bacteria etc. Plus, of course, because you are measuring a human, there's a whole stack of other inconsistencies.
Use whatever sensor you have handy.

You can also measure heat release.
https://www.ncbi.nlm.nih.gov/pubmed/638125
but that's a pain in the  neck.

[alancalverd]

Remind me which bit of "What is the energy required when someone is chopping meat?" mentions arms.

Better still, amaze me by using any other part of your body to chop meat!

Quote from: alancalverd on 17/12/2018 17:06:48

A butcher's assistant probably expends about 60 calories per day cutting meat.

Yeah... sure... everyone works a 2 hr day.

Pardon me for answering the question. There's a lot more to working in a butcher's shop than just chopping meat.

[alancalverd]

I finally did some science and weighed my chopper (Chinese, domestic size). 500 gram within a whisker. Raising it 50 cm, twice per second, I would expend 2 x 0.5 x 0.5 x 9.81 = 4.905 watts. From what I recall of my grandmother's professional equipment (she had a butcher's shop) an industrial cleaver weighs about twice as much, so a butcher would expend around 10W chopping meat.

[syhprum]

Now that we have a calculation as to the power output needed from our butcher when he/she is chopping all that is required is to observe our sample group of butchers and note what proportion of their working day is actually spent chopping meat and measure their efficiency as heat engines using one of the systems that BC has suggested when we would have sufficient data to answer the question.

Competitions are held in America for running up the stairs in skyscrapers I think it takes about 30 minutes it would be quite easy to calculate the sustained power output of the contestants .

[Bored chemist]

Better still, amaze me by using any other part of your body to chop meat!

Many of us find it helpful to use our brains for the things we do...

[alancalverd]

"Incisive thinker" is a compliment, but a man who can chop meat by just thinking about it, is a potential danger. Puts a whole new spin on "brain surgeon" though.