I was informed that whether one runs as fast as he can for a mile or a person walks a mile or a person jogs a mile, the same number of calories are expended. Is this true and if so, why?
You can convince yourself that this is false by taking it to the extreme. Would you burn the same number of calories in these two scenarios:
- Walking to the other side of the room
- Flailing violently to the other side of the room?
Different body motions definitely have different efficiencies.
A concrete example of a difference between walking and running is that when you run you waste a good deal of energy stopping your thrusting leg and bringing it back in front before you hit the ground. When you walk, gravity does a lot of this for you. (Your leg swings like a pendulum with a fundamental frequency near the frequency of your steps. You can see this by standing with one leg hanging free (stairs work nicely) and letting it swing.)
There are, of course, other differences. Air resistance (a velocity dependent force) comes to mind.
But, separate from the mechanics of it all, the body just loses efficiency when it has to do the same work in less time (==> more power). This is evidenced by the ease at which one can load a hundred 3 lb bricks on a truck as compared with loading one 300 lb brick, a possibly impossible task.
You’re expending much more energy by running, but you’re doing it for a much shorter time.
Does that make the difference statistically significant?
BTW, does this actually relate to a column?
Is this supposed to be linked to the running/walking/getting wet question?
MU: I don’t know whether or not this has been in a column in the past but I took a chance that it probably had been or something similar to it. By the way, I talked to another physicist today who said that with the question I asked above that essentially the energy utilized is the same …something about work = distance x ? But he’s no Einstein so I’m interested in what others have to say.
If I pick a random nutrition/exercise site off the 'net, I find a claim that running 8 m/h consumes 1165 Cal/h for a 190# man, while walking at 2 m/h consumes 345 Cal/h. With those numbers running turns out to be more efficient at 145 Cal/m instead of 172.
skelton, indeed that guy is no einsein:
work = forcedistance,
force = massacceleration, but
acceleration = derivative of velocity with respect to time = 0 for constant velocity
but, obviously you are doing work in running and in walking, so this just means that it is meaningless to just “count the amount of work done” by the simple work done in moving you forward. you have to take into account all of the little muscle movements of the arms, hips, legs, etc., as well as other factors internal to the body.
“I play the fool, Pyotr Alexandrovitch, to make myself agreeable.”
–Fyodor Pavlovitch, Brothers Karamazov