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BMI and Bone Structure


FanieFiets

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I recently went for a weight/power/cycle assesment at US sport science centre.

Most interesting fact was my weight. I always thought I was waaaaaaaay overweight. I am 182.5 m tall and according to BMI calculators I must weigh roughly between 68 and 83.

After my bodyfat was checked it turned out that I have 12.7% bodyfat. That is in the lower bracket of the normal range that is between 12 and 18%. Normal kg. is between 82.3 and 88 kgs. Very big diff between that and BMI.

The girl explained that it is due to a very heavy bone density or something like that (grew up on a dairy farm!).

 

Basicly what it means is that if my weight drop to 78 kg. I will have a body fat % of approx. 7%. Elite athletes have an % of between 5% and 9% (men).

 

However that still leaves me with a BMI of 23.4 that is quite high. Just found it interesting and was wondering if anyone else knew that BMI can be so inaccurate. Does that mean that I'm not build for the TdeF?

Anyone knows how accurate the testing is. They just put an electrode on your foot and and hand and kaboom, you have the rusult.
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Those  machines at VA gym are terrible, for the reason that you have just mentioned as well as the fact that people with genetically 'stocky' physiques will be called 'fat'

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BMI is an estimate figure only, as it does not take build into consderation - only height and weight.  You'll find that many bodybuilders for instance, carrying virtually no fat at all, land up with very high BMI's too.

 

I have been told by a couple of sources that the electronic measurement of bodyfat is not quite as accurate as pinch measuring.  If this is true or not, I can't say...
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I think you are right R2S2, as when I try those machines at the gym (always before exercise) I get fat % of 10 to 14 within a few days of each other - while my body weight is fairly constant... so somewhere i am losing/ gaining 3kg of fat? I think level of hydration effects the measurements

I dont use them anymore 
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Given that an electric current is used, and the resistance of tissue used as a measuer, I think varying electrolyte levels in the body can have quite an effect on these machines.  This is in any case the argument I have heard leveled against them.

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Dont know if this is the same machine. This one also gave my water contents in L. 50.2 litres!!!!!!   So i will make a nice Fanie Sappie!

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I recently went for a weight/power/cycle assesment at US sport science centre.

Most interesting fact was my weight. I always thought I was waaaaaaaay overweight. I am 182.5 m tall...

 

If you really are 182.5m tall I think you are more overheight than overweight...

 
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Hi Again Fanie

 

After my facetious reply I s'pose I owe you a more sensible one...

 

BMI is really a 'rough guide'.  IIRC, the range for 'normal' BMI is 18 to 25.

 

Now, the electro-reading doofuses that the gyms use are somewhat odd.  When Mrs Bikemonster wanted to start going to the gym to get back into shape after the birth of Bikemonster jr., we checked out the Active Virgins and Planet Fatarse.  The salesdork at PF did a body fat analysis, using a gadget that you hold out at arm's length, and it puts a small current through.  More comfortable than putting a small currant through you, but I digress.  The wonderful gadget decided that I was 'borderline obese', which I found suprising as I weigh 66kg and have a height of either 170m or 170cm, depending on the measuring standard in use.

 

Back to the 'guideline' status of BMI.  Anything that makes you heavier for your height than a 'normal' person is going to skew your BMI.  If you have a higher than average muscle mass, your BMI will show up as being high.  My guess is that the gym poppie has a BMI measure and a fat percentage measure (of dubious accuracy), and uses bone density as the answer to anything that doesn't otherwise stack up.

 

And finally...the one black mark against cycling is that it is not a weight bearing form of exercise, and bone density can reduce as a result.  Less weight to drag up the hills, but we can snap if we fall off our bikes.
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Heard about the bone density thing of cycling as well, still drink about a litre of milk a day!

 

But still it wasnt a gym poppie that did the tests but she actually has an M.Phil.  I send her an mail asking about the accuracy of the test, seeing that i'm eating a noodle salad at present and maybe should be eating a cucumber salad.
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Fanie,

 

Iewers die quote gesien, wat ek gebruik wanneer mense met vreeslike grade opinies lewer:

 

"Education teaches you that a tomato is a fruit.  Experience teaches you not to use it in fruit salad."

 

Vat haar BMI met meer as net 'n knippie sout!
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