Difference between running up and walking up ?

  1. Difference between "running up" and "walking up"?

    A person runs up several flights of stairs and is exhausted when they get to the top. Later, when they have recovered, the same person walks up the same stairs and does not feel as tired. Why is this? Ignoring air resistance, does it take more work or energy to run up the stairs than to walk up? Has anyone ever experienced this? Why is this so!?
  2. jcsd
  3. SteamKing

    SteamKing 10,959
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    You must never have run anywhere in your life.
  4. In theory you would burn the same amount of calories either way, if you don't take into account the jerkiness difference between them.
    But basically it is because one takes place over a shorter period of time for the same distance (or change in elevation), so biologically you have to exert yourself much more.

    The jerkiness is why slow walking burns more calories than fast walking for the same distance. Walking fast enables you to take advantage of reduced momentum changes; walking slow has a stronger component of cyclic forward and backward acceleration with each step. Just imagine the extreme case of taking a single step forward and stopping, then repeating at a rate of one step per second - you would be developing your full momentum and then eliminating it each second, using energy for both.
  5. sketchy answer
  6. I think it has to do with the muscles being utilized. When you walk up stairs, you're using your endurance muscles, which are meant for use over a long period of time. When you run up stairs, you're using your white fiber muscles which don't have much endurance.
    From a physics perspective, I guess you could say you're generating more power when you run up stairs, which is why you're more tired.
  7. "tiredness" is not a quantitative measure of work or energy.

    What you're describing is a physiological effect caused by the oxygen debt which results from anaerobic activity-running up the stairs. Walking up stairs is aerobic, so as long as you're breathing properly, you don't feel tired.

    Physically, the energy difference between you at the top of the stairs and at the bottom is the same, however you climb the stairs, because the gravitational field is conservative- the (gravitational) potential difference is only a function of the two points in the field.

    In practice, running is a less efficient way of getting up some stairs than walking, and the excess calories you burn are released in muscle heat.
  8. kmm

    kmm 137
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    Well, in physics, the work done over some path is the dot product between the force and the distance over which the force acted. Now, the amount of work required to go up some flight of stairs for a person would consist of two parts, the work done over the x and y component of their path. With each step they take, they have to exert some force to move their body forward. To move a body faster requires exerting more force. In the y component of their motion, if they both lift themselves to the same height with each step, then they will put forth the same amount of work since gravity is a conservative vector field. I doubt this would be the case because I suspect the person running would push their body a little higher with each step since they are pushing harder. Assuming they didn't, they would definitely have to exert more force in the x component of their motion since they have to accelerate their body quicker. So, the person running up the stairs must put forth more work.
  9. The work will be the same but the power isn't. Your aerobic power production can't keep up (you feel out of breath), and the anaerobic power production kicks in producing lactic acid in your mussels (you feel tired).
  10. kmm

    kmm 137
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    The work would not be the same.
  11. A.T.

    A.T. 6,456
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    Nope, only more acceleration requires more force. We are ignoring air resistance here.

    Of course running faster requires more acceleration of the moving parts (legs) and the center of mass is not moving at a constant speed either, so more work is indeed done by the muscles. But the main reason is that "tiredness" is not a quantitative measure of work done, as mikeph said. You can get very tried from static exercises, like holding up a weight, where no work is done at all.
  12. kmm

    kmm 137
    Gold Member

    I should have been more specific. Of course it is greater acceleration that requires more force. But I meant in this case, with two people starting from rest at the bottom of the stair case, if we said, "go!" the person running will have a greater acceleration initially. Because the running persons body will be moving quicker, they will experience a greater force backwards each time their foot hits the ground and therefore to maintain their velocity, they will have to exert a greater force forward. I understand that no work is done when holding a weight though.
    Last edited: Mar 9, 2014
  13. A.T.

    A.T. 6,456
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    This is a minor factor if they travel more than a few steps.

    That dependents on their running technique.
  14. By running, your muscles are put through brief but intense work opposed to walking. The same amount of energy is used, for sure, but how much can your body endure per time interval?
  15. kmm

    kmm 137
    Gold Member

    Minor perhaps, but more work required still. Perhaps there could be a running technique that minimizes the force they experience backwards so that it's the same as the walker. I would think this isn't the case for a standard run up the steps though. We could idealize the situation and ignore as many factors we want until we're talking about a point particle moving in a vacuum that experiences no other forces but the gravitational force. I would still say though that in general, someone running up steps puts forth more force on the ground in each step than the walker and therefore does more work, even if it turns out to be not by much.
  16. sophiecentaur

    sophiecentaur 14,712
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    The basic reason is that Anaerobic respiration is less efficient than aerobic respiration. If you restrict your output power within the aerobic limits that your lungs and blood system can support then you will use less chemical energy than if you develop more power. Also there will be waste products (lactic acid) which you need to get rid of when you are producing anaerobic power.
    So taking it slowly would be expected to knacker you less and take less time for you to recover.
  17. If you walked up very slowly taking 1 hour to make each step and two days for the total climb - you would also be pretty exhausted when you get to the top!

    In short the problem is all about the efficiency with which the human body operates at different speeds. Athletes spend a lot of time tuning their bodies to the particular event they are taking part in.
  18. A.T.

    A.T. 6,456
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    And if you walk even more slowly, you will die before you arrive at the top.
  19. I am not an expert in physiology, but I can think of a few things. Running generates heat faster, and your body needs to work hard to remove the heat. Running also requires higher metabolism by your muscles. Your body will use more anaerobic respiration, which is less efficient than aerobic respiration, and generates certain waste products like lactic acid which must be removed. Increasing your heart rate and breathing probably requires certain hormones to be released. Your gait is changed, so that you bounce up and down more, wasting some energy.
  20. It is not very black and white and cannot be analyzed with such simple concepts as work in mechanics. Apart from the different pathways available for ATP synthesis, as mentioned, you have to simply consider that a sprint requires a high rate of force development in the context of a motor unit. A motor unit consists of a groups of muscle fibers and the corresponding innervation. When we do things easy and slow, the nervous system sends low frequency pulses and does not recruit all motor units that are available. This type of control allows is to perform fine motor skills like eating with a fork, performing surgery and playing the piano for example.

    When we decide to go for an all out sprint, the nervous system sends impulses at a higher frequency and recruits as many muscle fibers as possible to make the action happen

    The biochemistry and neuromuscular physiological processes all contribute to you feeling like you did more work while sprinting as opposed to strolling. In fact you did, just not in the classical mechanics sense which only considers the gravitational field in which a 'particle' might be moving. We are not particles and we use the potential energy stored in chemicals (ATP being the 'basic unit' of energy in biochemistry) to get the work done.

    With practice you may be able to sprint the same distance without getting winded because your body can adapt by becoming more efficient with regard to inter- and intra-muscular coordination as well as some adaptations in the pathways which generate ATP.
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