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View Full Version : Are bio impedence measurements a bunch of voodoo?


MC
November 25th 04, 06:39 AM
My Gym has one of these machines that measures your weight and body's
impedence to get composition data.
What do you think?

Voodoo or valid technology?



http://www.tanita.com/BodyComposition.shtml


---------Begin Quote from website---------------------

BC-418 Segmental Body Composition
Analyzer/Scale
The addition of hand grips to our standard platform-based electrode
system allows the BC-418 to calculate regional body composition,
empowering healthcare professionals to better determine health risk
associated with visceral and abdominal fat.

Tanita is proud to introduce a significant improvement to the
calculation of Basal Metabolic Rate. Instead of simply relying on
weight, age and gender, Tanita's proprietary formula takes into
account Fat Free Mass, providing a higher level of accuracy compared
to current BMR formulas.




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Per Elmsäter
November 25th 04, 09:34 AM
MC wrote:
> My Gym has one of these machines that measures your weight and body's
> impedence to get composition data.
> What do you think?
>
> Voodoo or valid technology?
>
I have one of these at home and my bodyfat varies about 2% in the course of
a day. It is however consistent and constantly the same error compared to my
calipers. In other words it will show progress/digression if measured at the
same time of day and under the same circumstances. Measurements will get
boggled if you have recently done a cardio workout or lifting weights. There
is a warning in the manual saying that Bio impedance does not work
satisfactorily if you are a bodybuilder. This is a Tanita scale I have.

--
Perre
I gave up on SPAM and redirected it to hotmail instead.

KennyCrox
November 25th 04, 02:25 PM
>
>My Gym has one of these machines that measures your weight and body's
>impedence to get composition data.
>What do you think?
>
> Voodoo or valid technology?

The bioelectrical impedence devices have problems. There is a protocol you
must follow. You cannot have eaten, exercised or taken a shower with three
houses of using it. Doing so, throws the reading off.

Also, you must be well hydrated. If you aren't that throws the reading off.

The device does not work well for those who are overly fat and those with very
low body fat percentages.

The Tanita, one's you stand on, are slanged so they measure more the lower body
fat levels than the upper body. The hand held models do the reverse, They
tend to measure more of the upper body fat levels than the lower.

Perre noted in a previous post on this subject that his Tanita vary 2% during
the day. So, if one were 200 lbs that would mean that they would have 4 pound
more muscle at one reading and 4 pounds more fat at another reading. That is a
huge difference.

As for Perre statement that the Tanita are comparative to his hand held
calipers...there are only a limited number of people who know how to use
callipers. I doubt that he or who ever he has calibrating him know what they
are doing.

A good technician will use a pen and tape measure. They will mark you with a
pen and measure the same spot.

The hand callipers Perre are probably the cheap ones that don't go in to much
detail on how to do it right. It also takes practice with 100s of people to
become good at it.

Your mirror and you tape measure will do more for you...and they don't cost as
much.

Kenny Croxdale

bc
November 25th 04, 03:10 PM
"Per Elmsäter" > wrote in message >...
> MC wrote:
> > My Gym has one of these machines that measures your weight and body's
> > impedence to get composition data.
> > What do you think?
> >
> > Voodoo or valid technology?
> >
> I have one of these at home and my bodyfat varies about 2% in the course of
> a day. It is however consistent and constantly the same error compared to my
> calipers. In other words it will show progress/digression if measured at the
> same time of day and under the same circumstances. Measurements will get
> boggled if you have recently done a cardio workout or lifting weights. There
> is a warning in the manual saying that Bio impedance does not work
> satisfactorily if you are a bodybuilder. This is a Tanita scale I have.

The basic technology is sound. But the application to bodyfat
measurement for a live person in a home environment is frought with
variations which make absolute accuracy difficult.

http://www.solartronanalytical.com/technicalpages/techbioimp.html

I suspect that you can detect trends as mentioned above, and if you
can minimize the variation in your trials, i.e. same time of day, same
state of hydration, etc, you can build up a useful log of results as
long as you don't care too much about the accuracy of any one
measurement.

- bc

DRS
November 25th 04, 03:17 PM
"bc" > wrote in message
om
> "Per Elmsäter" > wrote in message
> >...
>> MC wrote:
>>> My Gym has one of these machines that measures your weight and
>>> body's impedence to get composition data.
>>> What do you think?
>>>
>>> Voodoo or valid technology?
>>>
>> I have one of these at home and my bodyfat varies about 2% in the
>> course of a day. It is however consistent and constantly the same
>> error compared to my calipers. In other words it will show
>> progress/digression if measured at the same time of day and under
>> the same circumstances. Measurements will get boggled if you have
>> recently done a cardio workout or lifting weights. There is a
>> warning in the manual saying that Bio impedance does not work
>> satisfactorily if you are a bodybuilder. This is a Tanita scale I
>> have.
>
> The basic technology is sound. But the application to bodyfat
> measurement for a live person in a home environment is frought with
> variations which make absolute accuracy difficult.
>
> http://www.solartronanalytical.com/technicalpages/techbioimp.html
>
> I suspect that you can detect trends as mentioned above, and if you
> can minimize the variation in your trials, i.e. same time of day, same
> state of hydration, etc, you can build up a useful log of results as
> long as you don't care too much about the accuracy of any one
> measurement.

Which is just anothe way of saying use it according to the manufacturer's
instructions. Studies have shown bio impedance as accurate as anu other
method when used properly.

--

"As democracy is perfected, the office of president represents, more and
more closely, the inner soul of the people. On some great and glorious day
the plain folks of the land will reach their heart's desire at last and the
White House will be adorned by a downright moron."
H.L. Mencken (1880 - 1956)

Per Elmsäter
November 25th 04, 05:48 PM
KennyCrox wrote:
> As for Perre statement that the Tanita are comparative to his hand
> held calipers...there are only a limited number of people who know
> how to use callipers. I doubt that he or who ever he has calibrating
> him know what they are doing.

I didn't say they are comparative. I said the error is constant. Ie my
Caliper measurements are approximately 1% lower than the lowest my Tanita
will show during the course of a day. Remember they are both an estimate.
I'm not going to argue whether I'm proficient with the calipers. However I
believe you spout just the slightest bit of prejudice there don't you think.
As far as you know I might very well have the most expensive set of calipers
etc etc..

One day when I supposedly get down to below 10% I'll go throw myself in a
tank. Until then knowing which way I'm heading and how fast is good enough.
--
Perre
I gave up on SPAM and redirected it to hotmail instead.