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How many joules expended for a push up? 
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#1
May1813, 09:53 AM

P: 32

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



#2
May1813, 10:15 AM

P: 1,425

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.



#3
May2013, 06:01 PM

P: 32

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 _ 


#4
May2013, 06:03 PM

P: 32

How many joules expended for a push up?
That would mean a few hundred pushups would be expending the same energy as a halfmarathon (according to a running app of mine) ... that can't be true
maybe i'm confusing calories with kcal or something. hmmfph. 


#5
May2013, 06:28 PM

Mentor
P: 12,068

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


#6
May2013, 06:31 PM

Mentor
P: 11,631

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. 


#7
Jul1713, 05:13 PM

P: 1

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 


#8
Jul1713, 06:13 PM

Mentor
P: 11,631

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).



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