Tanita SC-240 Instruction Manual page 28

Technical notes
- Factors giving errors in measurement
In the BIA method, impedance is measured and the body composition is calculated based on the
value. It is known that impedance changes by the amount of the total body water that occupies
about 60% of weight and the change in its distribution and temperature change. Therefore, for the
purpose of research or for daily repeating of measurements, the measurement conditions must be
kept constant. Measurement under the changing conditions of temperature and total body water
distribution or blood flow volume of extremities due to exercising, taking a bath, etc., affects the
measurement result since the electric resistance in the body also changes.
Therefore, it is recommended to measure under the following conditions for stable measurement.
1) 3 hours have passed after getting up and normal lifestyle activities are carried out during this
period. (The impedance transits staying at a high level if you remain sitting after getting up or
drive a car, etc.)
2) 3 hours or more have passed after eating. (For 2 – 3 hours after eating, the impedance has a
tendency to decrease.)
3) 12 hours or more have passed after vigorous exercise for measurement. (The tendency toward
changes in impedance is not stable depending on the type and rigorousness of the exercise.)
4) If possible urinate before taking measurement.
5) For repeated measurements, measure at the same hour as much as possible. (At the same time of
measurement of weight, the measurements can be made more stable by measuring at the same
time of the day)
Very stable measured values can be obtained by measuring under the above conditions.
And in the development of this equipment, the following 6 items were set as conditions for the
regression equation.
1) Prohibition of alcohol intake for 12 hours before measurement
2) Prohibition of excessive exercise for 12 hours before measurement.
3) Prohibition of excessive eating and drinking the day before measurement
4) Prohibition of eating and drinking for 3 hours before measurement
5) Urination just before measurement
6) Avoid measurements during menstruation (for female)
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