How many joules expended for a push up?

[wannab]

Just wondering if any of you can do the calculation that well approximates the amount of joules expended by a push up.

 

[256bits]

Sure. Determine the centre of mass of the body ( which might be around your belly button or a bit higher ) and then calculate the amount of work needed to raise the centre of mass by doing a pushup. By the way, this will be lower than the energy the body is using internally. Other muscles, for example the stomach muscles, are contracting to keep the body straight.

 

[wannab]

I'm around 80kg and I go about 0.5m high. So the change in potential energy is 80*9.8*0.5 = 392 J

Is that a reasonable estimate of the total minimum possible expended energy?

Can you believe a few years ago I was on the second year of an undergraduate Physics degree!? It has completely fallen out of my head -_-

 

[wannab]

That would mean a few hundred pushups would be expending the same energy as a half-marathon (according to a running app of mine) ... that can't be true

maybe I'm confusing calories with kcal or something. hmmfph.

 

[Redbelly98]

maybe I'm confusing calories with kcal or something. hmmfph.

That's probably it. You're calculation of 400 J looks reasonable.

Keep in mind that a joule is a pretty miniscule amount of energy. There is a reason electric companies charge by the kW-hr (millions of joules), rather than by the joule.

 

[mfb]

I think 0.5m is a bit on the high side.
There is a large difference between the raw power output (here: used to lift the body) and the amount of chemical energy the body needs. I don't know how the running app calculates its values.

 

[antlhem]

Push up and food

Hi guys, i came up with this relations between food and physical exercise,here my calculations:
Weight=70kg, Distance for push up=0.5m, Distance for squad=0.5m, distance for abs=0.5m.
70kg(9.81m/s2)=686.7N, so in exercise minimum i have to move my center of mass 0.5m:
1 push up=1squad=1abs: 343.35J=82.06cal
Lets say that i eat one can of tuna fish=94.9kcal
To waste the energy from tuna fish i would have to do 385 push ups, squads and abs!
hahahaha to much!
Be aware that these are very simple calculations

 

[mfb]

Your body is not 100% efficient, so this number gets reduced significantly. In addition, you need energy even if you are resting (of the order of 100W thermal, ~2000kcal/day, but with significant variation in the population).

 

[Sloyment]

In a push up, you do not lift the entire body. You lift the head by 50 cm, the arms by 40 cm, the chest by 30 cm … and the toe tips don’t move at all. Assuming that the weight is distributed equally along the length of the body, I therefor added a correction factor of 0.5:

80 kg * 9.8 N/kg * 0.5 m * 0.5 = 196.2 J

For comparison, a slice of bread has 500 kJ, a candy bar has 1000 kJ, and a gram of body fat has 30 kJ.

 

[Burner1]

Well during push-ups a lot of energy is dissipated in the friction between the muscles, maintaining the tension in tendons and ligaments, and much more biological processes.

 

[hackhard]

many websites and apps can do this calculation
by research over many participants over long workout sessions
estimating a variation of joules or calories spent over change in body temp

 

[mfb]

This thread is three years old. Let it rest, please.