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B Work done running on an inclined treadmill

  1. Oct 8, 2017 #1
    Why does it cost roughly the same effort to run against an inclined treadmill as up a hill of the same inclination? That is neglecting the movement of the legs and the bobbing up and down as we run and the wind resistance. I remember being told in school physics that there is no work done unless a mass is accelerated or raised. To a first approximation, on a treadmill we do not ascend and we do not accelerate.
    When running up a hill you are going up. So the treadmill should be nearly effortless as you are not raising a weight hence not doing work. Of course it is not effortless so where is my error?
     
  2. jcsd
  3. Oct 8, 2017 #2

    PeroK

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    It's not as hard to move on a treadmill as uphill on the ground at the same angle, but it is harder than a treadmill on the flat. Basically, the treadmill is moving part of your body (the foot and leg) downhill at each step - so, to some extent, your centre of mass. To stay at the same point on the treadmil, you have to keep moving at least some of your body upwards.

    On a real hill, you have to move all your body up the whole time. And that, I think you'll find, is a lot harder than uphill on a treadmill.
     
  4. Oct 8, 2017 #3
    Is it not the case that you have to keep moving your whole body upwards on a treadmill to counter the tread's movement? Say you weigh 60kg. Is the inclined treadmill not somehow forcing you to move all 60kg constantly upward (in a way I don't understand) and not just your legs?
     
  5. Oct 8, 2017 #4

    PeroK

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    No. Your head and upper body remain essentially at the same height.
     
  6. Oct 8, 2017 #5
    I'm having difficulty with this. I can see that your body mostly does not ascend on the treadmill at any time and wholly does not ascend on average (at the end of the run you are in the same place) and you seem to be saying that you do not have to work against the backward movement of the tread to stay put, except for a small component of work involving your lower body. This is not an answer I was expecting because I basically think it is false. I think you do have to work to keep your whole weight stationary against the tread. I asked the original question to find out how.
     
  7. Oct 8, 2017 #6

    PeroK

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    Suppose you attached a monitor to your upper body. How would it detect that you are on a inclined treadmill? If your upper body is not moving, it's not moving.
     
  8. Oct 8, 2017 #7
    If you stop working then your whole body shoots downward. To keep your whole body stationary you have to work.
     
  9. Oct 8, 2017 #8

    PeroK

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    I can do about 6.5 km/h on a 15° treadmill at the gym. On a 15° hill, I can do about 4 km/h. There is no comparison in the effort involved. You have to do no work to stop your body falling. That is no different from standing or walking on the flat.
     
  10. Oct 8, 2017 #9

    PeroK

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    PS I was at the gym today - honestly. I did 20 minutes at 15° at an average of 6 km/h. That is about 500m of ascent in 20 mins. My normal outdoor speed on a mountain is about 600m of ascent an hour. The reason is clear: on the treadmill my upper body is not moving; on a hill, my whole body is moving upwards.
     
  11. Oct 8, 2017 #10
    I admit I'm surprised.
     
  12. Oct 8, 2017 #11

    PeroK

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    It's quite different muscles as well. The uphill treadmill mostly works the calves and not much on the quads. In the mountains, it's both calves and quads that do the work. You really have to push hard to move your body up a mountain. It's much harder than the same speed on a treadmill. If I set the treadmill at my normal outdoor uphill speed of about 3 km/h it would hardly be a workout. That's just easy.
     
  13. Oct 8, 2017 #12

    jbriggs444

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    Completely irrelevant.

    The work that is not done raising your body is done moving the treadmill belt downward. Exactly the same net work done running uphill as on an upward-slanting treadmill.
     
  14. Oct 8, 2017 #13

    PeroK

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    The treadmill moves itself. There is no need to do any work to move the treadmill. To make it go faster, you press a button!

    In any case, it is far, far easier to walk or run uphill on a treadmill than on a real hill. For example, at 15° I can comfortably do 6 km/h, which equates to 1,500m of ascent an hour. On a real hill, I would max out at 750m of ascent an hour.

    1,500m of ascent an hour would make me a world-class mountain runner!
     
  15. Oct 8, 2017 #14

    PeroK

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  16. Oct 8, 2017 #15

    phinds

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    jbriggs, I usually find your comments spot on but I think you seriously missed the boat on this one. (1) The treadmill moves exactly the same whether you are on it or not and (2) yes it DOES matter that you are not raising your center of mass.
     
  17. Oct 8, 2017 #16

    jbriggs444

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    Sorry, you are wrong in this case. The force of the feet on the treadmill is not irrelevant.
     
  18. Oct 8, 2017 #17

    jbriggs444

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    Completely irrelevant. The work done by feet on belt is the same regardless of what other forces act on the belt.
     
  19. Oct 8, 2017 #18

    PeroK

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    What isn't irrelevant is that my gentle warm-up on the treadmill is 4 km/h at 15°, which equates to 1,000m of ascent an hour and is much faster than I could do on a real hill.

    There is simply no comparison. If you climbed mountains and went to the gym, you would know this for yourself.
     
  20. Oct 8, 2017 #19

    jbriggs444

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    Irrelevant. The physics of the situation is what it is.
     
  21. Oct 8, 2017 #20

    PeroK

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    ... says he from the comfort of his armchair!
     
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