# How many joules expended for a push up?

1. May 18, 2013

### wannab

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

2. May 18, 2013

### 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.

3. May 20, 2013

### 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 -_-

4. May 20, 2013

### 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.

5. May 20, 2013

### Redbelly98

Staff Emeritus
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.

6. May 20, 2013

### Staff: Mentor

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. Jul 17, 2013

### 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:
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. Jul 17, 2013

### Staff: Mentor

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).

9. Apr 14, 2016

### 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.

10. Apr 14, 2016

### 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.

11. Apr 16, 2016

### 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

12. Apr 16, 2016