Is BMI Valid For Cyclists?

Discussion in 'Cycling Equipment' started by Andrew Swan, Jan 27, 2004.

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  1. Andrew Swan

    Andrew Swan Guest

    Sorry if this isn't the right NG for this, but I was wondering if Body Mass Index is a valid measure
    for a reasonably fit road (not MTB or track) cyclist, or if not, is there some other yardstick for
    telling if a cyclist's weight is appropriate to their height?

    Just wondering...

    &roo
     
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  2. Robert Chung

    Robert Chung Guest

    Andrew Swan wrote:
    > I was wondering if Body Mass Index is a valid measure for a reasonably fit road (not MTB or track)
    > cyclist, or if not, is there some other yardstick for telling if a cyclist's weight is appropriate
    > to their height?

    This is like asking if height is a valid measure of how tall someone is: BMI is BMI.

    Nonetheless, here's some data from the 1997 TdF. Look about a quarter of the way down the page:
    http://www.cyclingnews.com/results/1998/feb98/feb6.html
     
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    In article <[email protected]>, Andrew Swan
    <[email protected]wMUSTswanDIE.com> wrote:
    >Sorry if this isn't the right NG for this, but I was wondering if Body Mass Index is a valid
    >measure for a reasonably fit road (not MTB or track) cyclist, or if not, is there some other
    >yardstick for telling if a cyclist's weight is appropriate to their height?
    >

    _ The only sport BMI makes any sense for is channel surfing.

    _ Booker C. Bense

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  4. Rik O'Shea

    Rik O'Shea Guest

    Andrew Swan <[email protected]> wrote in message news:<[email protected]>...
    > Sorry if this isn't the right NG for this, but I was wondering if Body Mass Index is a valid
    > measure for a reasonably fit road (not MTB or track) cyclist, or if not, is there some other
    > yardstick for telling if a cyclist's weight is appropriate to their height?
    >
    > Just wondering...
    >
    > &roo

    It depends on whether you think BMI is useful for anything. You probably shouldn't get too carried
    away with it.

    The pro riders in the Tour de France (1997 data) have values from 19 to 23. The average is 21.4701 I
    think Pantani had one of the lowest just below 19 but dont forget this is their full time job.

    A good rule of thumb for amateur racers of medium/slim build who want to climb well is 1 kg for
    every inch of height. So 5-foot-10-inch (70 inches) = 70 kg = 154 lb. Although use your discretion
    if you are a larger build (I dont mean big & fat) or stocky and or muscular.
     
  5. Derk

    Derk Guest

    Robert Chung wrote:

    > This is like asking if height is a valid measure of how tall someone is: BMI is BMI.
    I don't agree with you. BMI is for everybody else who doesn't work out also, but some cyclists (or
    other athletes) have a lot of extra muscles (sprinter's legs e.g.). This weight is counted in the
    overall picture, so in reality their BMI would be lower since the "extra" weight is not fat, but
    muscles. BMI can't tell teh difference between fat and muscles, so at a same given BMI one person
    can carry far more fat than someone else with the same BMI number.

    A friend of mine, who is a cyclist also, did an online BMI test and got the advice to exercise less,
    because his BMI was be too low. This guy can eat 2 horses and a pile of puddings and stay skinny. He
    was just born this way, so I don't think BMI says it all.

    I find the weight they give as being maximum weight allowed before being overweight FAR too
    high. I weigh 70.5 kg and am 185cm tall. Look how much they claim I could gain and still be
    considered normal.

    Greets, Derk
     
  6. Matt O'Toole

    Matt O'Toole Guest

    [email protected] wrote:

    > In article <[email protected]>, Andrew Swan
    > <[email protected]> wrote:

    >> Sorry if this isn't the right NG for this, but I was wondering if Body Mass Index is a valid
    >> measure for a reasonably fit road (not MTB or track) cyclist, or if not, is there some other
    >> yardstick for telling if a cyclist's weight is appropriate to their height?
    >>
    >
    > _ The only sport BMI makes any sense for is channel surfing.

    ...which is the one most people engage in. For the rest of us, it probably isn't as applicable.

    Matt O.
     
  7. Robert Chung

    Robert Chung Guest

    Derk wrote:
    > Robert Chung wrote:
    >
    >> This is like asking if height is a valid measure of how tall someone is: BMI is BMI.

    > I don't agree with you. BMI is for everybody else who doesn't work out also, but some cyclists (or
    > other athletes) have a lot of extra muscles (sprinter's legs e.g.). This weight is counted in the
    > overall picture, so in reality their BMI would be lower since the "extra" weight is not fat, but
    > muscles. BMI can't tell teh difference between fat and muscles, so at a same given BMI one person
    > can carry far more fat than someone else with the same BMI number.

    So you're saying height isn't a good metric for how tall basketball players are?
     
  8. Derk wrote:

    > I find the weight they give as being maximum weight allowed before being overweight FAR too
    > high. I weigh 70.5 kg and am 185cm tall. Look how much they claim I could gain and still be
    > considered normal.

    As someone who is right on the BMI=25 limit, I disagree! Everyone says I look thin - some people are
    just more "dense".
     
  9. Pk

    Pk Guest

    Robert Chung wrote:
    > Derk wrote:
    >> Robert Chung wrote:
    >>
    >>> This is like asking if height is a valid measure of how tall someone is: BMI is BMI.
    >
    >> I don't agree with you. BMI is for everybody else who doesn't work out also, but some cyclists
    >> (or other athletes) have a lot of extra muscles (sprinter's legs e.g.). This weight is counted in
    >> the overall picture, so in reality their BMI would be lower since the "extra" weight is not fat,
    >> but muscles. BMI can't tell teh difference between fat and muscles, so at a same given BMI one
    >> person can carry far more fat than someone else with the same BMI number.
    >
    > So you're saying height isn't a good metric for how tall basketball players are?

    a good few of the English rugby team who just won the world cup are "obese" by BMI measures

    see http://www.rugbyrugby.com/COUNTRY_BY_COUNTRY/New_Zealand/Country_News/story_33140.shtml

    for more on BMI & sportsmen.

    pk
     
  10. Derk

    Derk Guest

    Robert Chung wrote:

    > So you're saying height isn't a good metric for how tall basketball players are?
    You're twisting my words. Of course height is OK for determining how tall anybody is, but here we're
    not measuring 1 integer as height or fat pecentage, but the *RELATION* between two values.

    Greets, Derk
     
  11. Robert Chung

    Robert Chung Guest

    Derk wrote:
    > Robert Chung wrote:
    >
    >> So you're saying height isn't a good metric for how tall basketball players are?
    > You're twisting my words. Of course height is OK for determining how tall anybody is, but here
    > we're not measuring 1 integer as height or fat pecentage, but the *RELATION* between two values.

    So you're saying newtons aren't a good metric for force?
     
  12. Ray Heindl

    Ray Heindl Guest

    "David L. Johnson" <[email protected]> wrote:

    > BMI is silly, since it factors height in linearly with respect to weight.

    Au contraire. BMI = weight/(height^2).

    > For the same proportions, a 5-ft tall person weighs
    > (5/6)^3 =0.57 times that of an 6-foot person. So, those two people with the same build would have
    > the short guy considered thin, but the tall guy considered fat.

    I've never seen an explanation of why height is squared rather than cubed in the BMI definition. It
    might have to do with the way things scale in the real world; an elephant's bones are
    proportionately much heavier than an mouse's, for example. Or maybe it just came out of some kind of
    fit to actual data.

    --
    Ray Heindl (remove the Xs to reply)
     
  13. Derk

    Derk Guest

    Zog The Undeniable wrote:

    > As someone who is right on the BMI=25 limit, I disagree! Everyone says
    I wasn't speaking about other people, but about myself. So, sorry if I offended you.

    > I look thin - some people are just more "dense".
    OK, I calculated that I could weigh 86 kg and still have a BMI of 25.

    Please don't tell me that if I would put 15 kg of fat onmy body now, I still wouldn't look chubby.
    Where do I leave all that weight?

    I know what I'm talking about, since I used to be 30 kg heavier about 8 years ago. This was the
    reason I started cycling. I can assure you I wasn't thin when I weighed 85 kg.

    Greets, Derk
     
  14. Derk

    Derk Guest

    Robert Chung wrote:
    > So you're saying newtons aren't a good metric for force?
    This is a scientific formaula, that you can prove over and over again.

    BMI isn't a given formula based on scientific evidence.It has a lot of fuzzyness: your BMI is OK if
    it's between 20 and 25. Why those numbers? Why not between 19.9 and 25.2 for example?

    Greets, Derk
     
  15. Derk <[email protected]> wrote:

    > I find the weight they give as being maximum weight allowed before being overweight FAR too
    > high. I weigh 70.5 kg and am 185cm tall. Look how much they claim I could gain and still be
    > considered normal.

    I'm 169 cm and 60 kg, so I should be able to gain 12 kg and remain within the supposed normal
    limits. This is a bit curious, as I don't have a particularly low body fat percentage even now, and
    the BMI formula should also be working against short people like me.

    Lately in the local newspaper there's been letters from various medical experts about the problems
    of the standard BMI formula. The fundamental problem they keep pointing out is the fact that body
    mass just doesn't increase relative to the square of height. Supposedly it would be a lot more
    accurate for people of different height, if the mass was raised to the power of about 2.6, in the
    formula. Even then it would ignore muscle mass, but it would be a better starting point.

    -as
     
  16. Antti Salonen <[email protected]> wrote:

    > Supposedly it would be a lot more accurate for people of different height, if the mass was raised
    > to the power of about 2.6, in the formula.

    I obviously meant to say height, not mass. The suggested formula is thus:

    BMI = mass(kg) / height(m) ^ 2.6

    -as
     
  17. Carl Fogel

    Carl Fogel Guest

    Derk <[email protected]> wrote in message news:<[email protected]>...
    > Robert Chung wrote:
    > > So you're saying newtons aren't a good metric for force?
    > This is a scientific formaula, that you can prove over and over again.
    >
    > BMI isn't a given formula based on scientific evidence.It has a lot of fuzzyness: your BMI is OK
    > if it's between 20 and 25. Why those numbers? Why not between 19.9 and 25.2 for example?
    >
    > Greets, Derk

    Dear Derk,

    You've pointed out an obvious problem with BMI. Unlike Newton-meters, it doesn't really tell us as
    much as people believe.

    BMI unquestionably defines a precise and scientific ratio between our weight and our height.

    So what?

    Equally precise and scientific ratios can be calculated between our weight and our shoe size, wrist-
    elbow distance, pelvic width, femur length, shoulder breadth, and--well, let's not get into personal
    areas where the ladies assure us that size doesn't matter, anyway.

    For all its spurious air of precision, our BMI fluctuates daily, since we can lose an inch of height
    during the day as our spinal discs compress or a few pounds of weight through processes too terrible
    to contemplate.

    Even when accurately calculated, BMI says nothing about whether the mass being related to height is
    composed of fat, muscle, or bone. If you have a high BMI, all that it tells you is that you have
    more mass than average--possibly fat, perhaps muscle, maybe heavier bones, or any combination of
    the three.

    An extremely fit athlete may have a low BMI (marathon runners) or a high BMI (heavyweight boxers).
    And they may match the BMI's of sedentary office workers in their fifties.

    Height in basketball players isn't much more useful than BMI. Height can help, but scouts are
    painfully familiar with tall fellows who can't play basketball well enough to make the junior
    varsity squad.

    Greets,

    Carl Fogel
     
  18. Chalo

    Chalo Guest

    Andrew Swan <[email protected]> wrote:

    > Sorry if this isn't the right NG for this, but I was wondering if Body Mass Index is a valid
    > measure for a reasonably fit road (not MTB or track) cyclist, or if not, is there some other
    > yardstick for telling if a cyclist's weight is appropriate to their height?

    BMI is a bogus measure for any purpose. It's like prescribing a "correct" waist circumference
    or hat size.

    The problem is that BMI calls for dividing weight by the square of height, when weight scales as the
    cube of height. The result is that a tall person can have the same proportions and body composition
    percentages as a short person, but have a higher BMI. Can a gymnast be "underweight" while an
    equally lean and fit basketball player is "overweight"?

    The implication of this basic mathematical fault is that there is no "right" BMI number, and
    since it is an index invented for the purpose of having a "right" number, it fails at its
    intended purpose.

    BMI must have a strong appeal to folks' ingrained sizeist crap, because it has gained great cultural
    traction despite its lack of scientific value.

    Chalo Colina
     
  19. Tim McNamara

    Tim McNamara Guest

    Antti Salonen <[email protected]> writes:

    > Antti Salonen <[email protected]> wrote:
    >
    >> Supposedly it would be a lot more accurate for people of different height, if the mass was raised
    >> to the power of about 2.6, in the formula.
    >
    > I obviously meant to say height, not mass. The suggested formula is thus:
    >
    > BMI = mass(kg) / height(m) ^ 2.6

    If I've done my math right:

    mass = 99 kg height = 1.91 m

    Old formula:

    BMI = 99/(1.91 ^2) = 99/3.65 = 27.12 (overweight).

    Proposed formula:

    BMI = 99/(1.91 ^2.6) = 99/5.38 = 18.40 (anorexic)

    Under the normal formula, I'd have to weigh something under 144 lbs to achieve a BMI of 18.40.
    Methinks the factor of ^2.6 is in error. I think that the standard factor of ^2 is accurate enough
    for my height. At 217 lbs I am about 20 lbs above my optimal weight from practical experience, and
    that coincides with the BMI. I couldn't tell you how accurate it is for shorter people. Getting back
    to my optimal weight is this year's goal.

    Excellent information available at:

    http://www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt/index.htm
     
  20. Robert Chung

    Robert Chung Guest

    Derk wrote:
    > Robert Chung wrote:
    >> So you're saying newtons aren't a good metric for force?
    > This is a scientific formaula, that you can prove over and over again.
    >
    > BMI isn't a given formula based on scientific evidence.It has a lot of fuzzyness: your BMI is OK
    > if it's between 20 and 25. Why those numbers? Why not between 19.9 and 25.2 for example?
    >
    > Greets, Derk

    Sigh.

    Two points on the map are 10 kilometers distant. I contend that distance in kilometers is a valid
    measure of how far apart they are, regardless of whether you are on foot, on a bicycle, in a car, or
    in an airplane; or whether there is a canyon, a river, a range of mountains, or a straight and flat
    road between them. Distance is distance.

    BMI is a measure, and it is a perfectly valid measure. BMI is BMI. The interpretation of that
    measure depends on what you're trying to use it for. Do not confuse the metric itself with the scale
    of interpretation. The poster didn't ask if a BMI of 25 (or 19.9 or 25.2) was appropriate or valid,
    he asked if BMI was valid. Of all the posts in this thread, mine was the only one that put that
    metric into context by pointing to a data table with the BMIs of actual TdF riders.
     
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