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How much does body weight affect running?

  1. Apr 22, 2007 #1
    Compare someone who is 10kg overweight to normal weight, how much faster and better can the normal weight person run a 5km race? Assuming each received did the same training and diet during the training. So both person might lose weight after the training period but their weight difference will still stand.
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  3. Apr 22, 2007 #2
    I'm 6' 3" and i weight 72kgs. I slow as snails when it comes to running or jogging and i run alot. But I have alot of endurance. So i think weight has been irrelavent to speed ( to an extent).
  4. Apr 22, 2007 #3


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    I guess it doesn't matter, since +10kg with respect to "normal" weight (assuming a specific height and body constitution) isn't specially "overweight".
  5. Apr 22, 2007 #4
    10kg overweight suggests that the person is carrying an extra 10kg of fat. That is extra weight that the person has to move that does not contribute to their performance.

    There are many factors that determine how well a person runs. Diet and training can be very helpful in conditioning muscles to produce ATP and absorb lactic acid. This results in better muscle performance for longer duration.

    There are also different types of muscle fibers. There are fast twitching and slow twiching fibers that make up the voluntary muscles. Fast twitching muscles contract and relax rapidly and are used for quick movement. Slow twitch fibers have more capillaries to increase blood flow and create ATP and more mitochondria to absorb lactic acid. These are more resistant to fatigue. Most of the muscles in your body have both types of muscle fibers.
  6. Apr 22, 2007 #5


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    Performance is determined by strength to weight ratio and conditioning.

    As Huckleberry mentioned, there are fast twitching fibers (useful for sprints) and slow twitching fibers (for long distance running).

    Runners tend not to be overweight, but have an optimal weight based on there activity. The average person is ill-conditioned for athletic performance, especially the older the person.
  7. Apr 22, 2007 #6
    Well, the more mass you have, the harder your cardiovascular and respiratory systems have you work in order to keep the cells nourished. I consider myself to be in pretty good shape, lifting weights 3 days a week, running or biking or playing hockey 3-4 days a week...I've gained a few more pounds of muscle since I started lifting seriously again, and I noticed a difference when I started running again. The heavier you are, the harder it is going to be to get into decent shape if you are just starting out.
  8. Apr 22, 2007 #7
    Thought 1: you might think of the difference between running with a 10 kg backpack or without it.

    Thought 2: an extra 10 kg of body weight is not located in one position like a backpack but is disseminated throughout your body. It would be better balanced. Carrying this extra weight would also be something you are already used to 24 hours a day so it should be more manageable.

    Thought 3: since the extra 10 kg is living tissue, it will respond to the workout requirements. The training might train fat cells to respond better in releasing their energy more efficiently when needed, which would counter some of the drawback of carrying this weight. I don't know if it would actually do this and to what degree, but it's something to look into.

    Thought 4: your scenario assumes that both the normal and the overweight runners would retain their weight difference if they undergo the same training. I think the heavier person is likely to expend more energy during the training due to the extra weight so the weight drop should be greater, all else being equal.

    Thought 5: many more differences than just weight affect running. For example, upper body strength doesn't help much here, you need leg endurance, strong heart, lung capacity, proper technique and so on. It would be hard to just compare two separate individuals and reach a conclusion on the effect of weight alone.
  9. Apr 22, 2007 #8

    Chi Meson

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    If I dropped 10 pounds, I could expect to take 1 to 3 milutes off a 3 mile race. 10 kg is 22 lbs. That is a phenomenal amount of weight to drop if you are already a runner. If you are just starting to run (approx 20 mile--30 km per week), then that weight will come off quickly, and your time will drop rapidly.
  10. Apr 22, 2007 #9
    Usually excessive weight goes hand in hand with a lack of flexibility. Pay attention when running that your legs move straight forwards, and straight backwards, your toes point straight, your pushing of with your big toe, and your hip, knee, and big toes form a straight line.

    It is impossible to force your body to run this way, but it will happen automatically if you stretch your hamstrings. An extra 20Kgs of stomach gets in the way for stretching, makes it more unpleasant.
  11. Apr 22, 2007 #10
    If losing that extra weight is the purpose then running is a pretty good idea. It's amazing how fast the body adapts to the excersice. For the first few weeks just concentrate on maintaining an elevated heart rate for about 15 minutes. Don't worry about distance or speed for that time. It doesn't matter if you have to walk during that time, as long as the heartrate stays up. It should be difficult, but not to the point where you have to stop. In those first few weeks you will see several minutes drop off your time for a mile. It's a very encouraging feeling.

    When I used to run the first mile was simple. The next two I worked through the pain. By the end of the 5th mile I was moving faster than when I started. The adrenaline had kicked in and I felt great, like I could run all day. I had myself down to 5 miles in 40 minutes and 1.5 miles in under 10 minutes. That acheivement gave me confidence in other areas of my life. If you think you might be interested in running, I highly recommend it.
  12. Apr 22, 2007 #11
    Sorry but this is like doing this for a comparison:

    what is the difference between a 911 turbo and a VW Bettle over a 10 Mile stretch if you ensure that the 911 has 100KG more weight.

    The weight is not as important as cadence, and respiratory ability, stamina, strength.. etc etc

    Im about 80KG and only 5"8 a tad overweight according to most books, but I play a lot of sport, specially Rugby, and my pb in 100m in 11.2 Secs, and 400 in 52s, (a few years ago :biggrin: ). However I was about the same weight.

    So weight is no way to judge athletic ability. Now if you turned your question round and said, could one athlete by loosing some extra weight be able to run faster and further the answer could well be yes.
  13. Apr 22, 2007 #12
    Find a 10kg vest and try running in it.

    I tried to find a good article on the net that gives some suggestions and maybe answers to your question but I can't find anything.
    Last edited: Apr 22, 2007
  14. Apr 23, 2007 #13


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    Think of it this way. Assuming by "overweight," you mean that the extra 10 KG is fat, not muscle. So the two people will have the same amount of muscle fact, and ceteris parabus, that is, assuming max VO2, lactic acid tolerance, and fast twitch/slow twitch muscle fiber ratios are about the same, which would happen if the two are close enough genetically and in diet and training, should be able to express about equal amounts of power. The ratio you end up with is that the time of the heavier guy divided by the time of the lighter guy is (x+100)/x Newtons.

    To give a more concrete example, I weigh about 87 kgs and can run a 5K in right around 18 minutes. If I dropped 10 kgs without losing any muscle mass and maintained about the same level of muscular and aerobic endurance, I'd cut my time to about 15:55. Notably, I was about 10 kgs lighter in high school and ran in the mid 16 minute range. I'd reckon I actually have far less endurance now than I did then, but I have much more muscle mass, and thus can express far greater amounts of power.
  15. Apr 23, 2007 #14
    You people and your athleticism. And I was proud of my 2km per day.....
  16. Sep 7, 2008 #15
    Weight affects running a lot, if my performance today is any indication! I'm 7 pounds more than normal, which caused me to run my 25K almost 8 minutes slower than I would at my normal 123.

    Here's the site:
    http://www.runningforfitness.org/calc/weighteffect.php [Broken]
    Last edited by a moderator: May 3, 2017
  17. Sep 7, 2008 #16
    Be careful when you stretch.:surprised

    Last edited by a moderator: Sep 25, 2014
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