How many calories can you safely burn in 2 hours?

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tom_whitebox
tom_whitebox Posts: 3
in Fitness and Exercise
I am actually building an educational application for kids that requires that survivors of an earthquake in Alaska most efficiently collect materials to build a shelter ... I know this is well off topic for this group but this seemed like a sensible place to ask a community for help.

Basically we have a reasonably fit "survivor", but he/she needs to work their tail off for a couple of hours hiking and hauling materials back to a shelter build site (there will be 4 different survivors all going in different directions). Some materials will require that they use far more energy than others. So, my basic question is this:

What would be a reasonable upper limit on Calorie burn in an hour? Two hours?

And, whatever that limit is - what's the reason? What would happen to you if you exceeded the limit? Would your body simply fail to function ... Obviously this is different from dieting - the effects are short term indeed, so I may be asking the wrong question(s) ...

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  • Timshel_
    Timshel_ Posts: 22,834 Member
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    If you ran at a really hard pace for an hour you basically max out your cardio system. Burns for running are somewhere around 900 to 1400 calories per hour, depending on the person's stats burning them. This would be helpful to know during a zombie Apocalypse, since zombies are fairly slow and you need to keep moving. You would need to sustain that calorie burn with food though, which movies fail to ever show. These people run around like crazy, burning an athletes share of calories trying to stay alive, but they never eat.

    But I digress.
  • tom_whitebox
    tom_whitebox Posts: 3
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    And what would be the risk of pushing the limits of your cardio system? Heart attack for an otherwise perfectly healthy person? Other potential damages to the circulatory system other than heart issues?

    Thanks a million!

    P.S. Now I have something to think about when season 4 of the The Walking Dead comes to Netflix!
  • cjudesaenz
    cjudesaenz Posts: 67 Member
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    you run the risk of a lot really. Look up rhabdomyolysis. I see a lot of new cadets from FD, PD, BP come in to the ED with this when they start their intense training. You can have kidney failure/cardiac failure/respiratory failure etc... CRAZY **** REALLY... In fact I've had marathon runner come in from cardiac collapse.... HEALTHY PEOPLE JUST DIE
  • tom_whitebox
    tom_whitebox Posts: 3
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    Thank you all so much. I think I have what I need!
  • JoRocka
    JoRocka Posts: 17,525 Member
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    you run the risk of a lot really. Look up rhabdomyolysis. I see a lot of new cadets from FD, PD, BP come in to the ED with this when they start their intense training. You can have kidney failure/cardiac failure/respiratory failure etc... CRAZY **** REALLY... In fact I've had marathon runner come in from cardiac collapse.... HEALTHY PEOPLE JUST DIE

    I highly doubt anyone is going to get rhybo from survival skills. It doesn't work like that. Read Endurance about Shackleton's trans-artic expedition- none of them suffered rhybo and I can tell you they were working damn hard some day.

    In those situations you are not going to be concerned with how much- but as long as you get food- you'd be very concerned about getting/finding/stocking as much food as you could. And then being very meticulous about rationing it out.

    the human body is an amazing thing- and will adapt to it's environment.
  • scorpio516
    scorpio516 Posts: 955 Member
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    What would be a reasonable upper limit on Calorie burn in an hour? Two hours?

    Depends on mass. But 1200 KCal/hr is very hard to break for an average size younger(under 35) male. If you are a very fit 300 lb male, you can easily break 1200 KCal/hr just cause it's harder to move the mass.
    And, whatever that limit is - what's the reason?

    It's simply too hard to work harder.
    A world record marathon, as a 160 lb male, would burn ~2600 KCal over 120 minutes.
    Two reasons that's not going to happen - 120 minutes is 3 minutes faster than the record. And it's almost impossible to run WR pace at 160 lbs. The fastest runners are in the 120-135 range. They'd burn about 2100 KCal for the 123 minutes.
    What would happen to you if you exceeded the limit? Would your body simply fail to function ... Obviously this is different from dieting - the effects are short term indeed, so I may be asking the wrong question(s) ...

    You'd be really hungry. And tired.
    That's about it.

    Basically, if you worked hard enough to be above your lactic threshold, you'd reach a point where your body cannot process anymore lactic acid. Then you'd slow down. You wouldn't cease to function, you just couldn't function at a high level.
    i.e. if you are running. You reach your limit. You don't suddenly fall to the ground unable to do anything. You can walk, talk, etc. You can't really exert yourself till your body catches back up on processing lactic acid.
    Lactic threshold and processing has nothing to do with calorie usage. You can keep going with a HR below threshold for hours and hours and hours.

    I'll give another example. Say you are 160 lbs. You finish a iron-distance triathlon. It takes about 1100 Calories to swim 24 miles. If you put out a steady 200W, biking 112 miles burns 3350 KCal. Running a marathon next takes 2600 KCal. To complete the race, that's 7050 Calories.
    Winners, who usually fall in the 150-160 lbs range, finish in a little over 8 hours. Say 8.25 hrs. That's about 850 KCal/hr. There is a bunch of intake of calories over that time! But, they all safely burn over 800 KCal per hour for over 8 hours straight.

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