JP2023073088A - Bioelectrical impedance measuring device and measuring method - Google Patents

Abstract

To easily measure impedance inside a living body.SOLUTION: A pair of first electrodes 10 are disposed separately at a predetermined position of a living body. A pair of second electrodes 11 are disposed on a straight line connecting the pair of first electrodes 10 separately, and the pair of first electrodes 10 are disposed inside the pair of second electrodes 11. A pair of third electrodes 12 are disposed separately on the straight line connecting the pair of first electrodes 10, and the pair of second electrodes 11 are disposed inside the pair of third electrodes 12. An electric current I1 is applied to the living body by a first power source 13 through the second electrodes 11 to calculate impedance Zout. In the meanwhile, an electric current I2 is applied to the living body by a second power source 14 through the third electrodes 12 to calculate impedance Zall. Impedance Zin inside the living body is calculated by Zin=Zout×Zall/(Zout-Zall).SELECTED DRAWING: Figure 1

Description

The present invention relates to a bioelectrical impedance measuring device and method, and more particularly to measuring internal impedance.

A method is known in which an electric current is applied to a living body to measure bioelectrical impedance to evaluate muscle mass and water content.

In Patent Document 1, a large number of electrodes that are in contact with the living body are arranged in an annular shape, a current is passed through the living body from one pair of electrodes, a plurality of voltages are measured with the remaining electrodes, and calculations are performed based on these measurement results. A device is described for processing to image a bioelectrical impedance distribution.

Non-Patent Document 1 describes measuring bioelectrical impedance by a four-electrode method and evaluating the degree of muscle fatigue from the impedance before and after high-load muscle exercise.

JP 2014-233619 A

Todd J. Freeborn, Bo Fu, "Fatigue-Induced Cole Electrical Impedance Model Changes of Biceps Tissue Bioimpedance" Fractal Fract, Vol.2, No.4, 2018

The bioelectrical impedance that can be measured by the method of Non-Patent Document 1 is the impedance of the entire inside of the living body, but the impedance of the skin changes greatly depending on the humidity. Therefore, with the method of Non-Patent Document 1, it was difficult to measure only the impedance change of the muscle inside the living body. In particular, when the area of the device is reduced, the current concentrates on the surface of the living body, making it more difficult to measure the internal impedance.

In addition, in the method of Patent Document 1, it is necessary to arrange a large number of electrodes over a wide area in order to image the internal impedance distribution, which increases the size and complexity of the device or system and increases the amount of calculations to be processed. I had a lot of problems. In addition, since the electrodes are close to each other, the current is concentrated on the surface of the human body, and variations in the surface impedance reduce the measurement accuracy of the internal impedance.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a measuring apparatus and a measuring method capable of easily measuring the impedance inside a living body.

A first aspect of the present invention includes a pair of first electrodes to be brought into contact with a living body, and a pair of electrodes to be brought into contact with a living body, which are spaced apart on a straight line connecting the pair of first electrodes, and one A second electrode arranged such that the pair of first electrodes is on the inner side, and a pair of electrodes to be brought into contact with the living body, which are arranged separately on a straight line connecting the pair of first electrodes, and a pair of A current is passed through the living body through the third electrode arranged so that the second electrode of the second electrode is on the inner side, and the current value is measured and the voltage value between the first electrodes is measured to measure the voltage value of the living body. The impedance of the surface of the living body is measured, current is passed through the living body via the third electrode, the current value is measured, and the voltage value between the first electrodes is measured to measure the impedance of the entire cross section of the living body. and a measuring unit for calculating the impedance inside the living body from the impedance of the whole cross section of the living body.

In the first aspect of the present invention, the measurement section may have one current source and a switch that switches between connection between the current source and the second electrode and connection between the current source and the third electrode.

A second aspect of the present invention includes a pair of first electrodes to be brought into contact with a living body, and a pair of electrodes to be brought into contact with a living body, which are spaced apart on a straight line connecting the pair of first electrodes, and one A second electrode arranged such that the pair of first electrodes is on the inner side, and a pair of electrodes to be brought into contact with the living body, which are arranged separately on a straight line connecting the pair of first electrodes, and a pair of a third electrode arranged such that the second electrode of the second electrode is on the inner side; a measurement unit that applies a second current, measures the current value in this state, measures the voltage value between the first electrodes, and calculates the impedance inside the living body. It is a device.

In the present invention, the second electrode may have a linear shape extending in a direction perpendicular to a straight line connecting the pair of first electrodes.

In the present invention, 0.1≦L1/D1≦5 may be satisfied, where D1 is the thickness of the part of the living body whose internal impedance is to be measured, and L1 is the distance between the third electrodes.

In the present invention, 0.1≦L2/D2≦5 may be satisfied, where D2 is the skin thickness of the part of the living body whose internal impedance is to be measured, and L2 is the interval between the second electrodes.

In the present invention, the measurement unit may evaluate the degree of muscle fatigue from changes in impedance inside the living body.

In the present invention, the measurement unit may measure the internal impedance of the living body at different frequencies and evaluate the degree of muscle fatigue based on changes in the impedance ratio.

A third aspect of the present invention is a pair of first electrodes and a pair of electrodes, which are arranged separately on a straight line connecting the pair of first electrodes, and the pair of first electrodes are arranged inside and a pair of electrodes, which are spaced apart on a straight line connecting the pair of first electrodes, and the pair of second electrodes are arranged on the inner side. 3 electrodes are brought into contact with a living body, current is passed through the living body through the second electrode, the current value is measured, and the voltage value between the first electrodes is measured to measure the impedance of the surface of the living body. A current is passed through the living body through three electrodes, and the current value is measured, and the voltage value between the first electrodes is measured to measure the impedance of the entire cross section of the living body. A bioelectrical impedance measuring method characterized by calculating the internal impedance of a living body from the impedance.

A fourth aspect of the present invention is a pair of first electrodes, and a pair of electrodes, which are spaced apart on a straight line connecting the pair of first electrodes, and the pair of first electrodes are inside and a pair of electrodes, which are spaced apart on a straight line connecting the pair of first electrodes, and the pair of second electrodes are arranged on the inner side. The three electrodes are brought into contact with the living body, and a first current is passed through the living body through the second electrode, and a second current having a phase opposite to the first current is passed through the living body through the third electrode. and calculating the impedance inside the living body by measuring the current value and measuring the voltage value between the first electrodes.

According to the present invention, the impedance inside the living body can be easily measured.

1 is a diagram showing the configuration of a bioelectrical impedance measuring device according to a first embodiment; FIG. The figure which showed the structure of the arm part of a living body. Equivalent circuit of the arm part of the living body. The figure which showed the modification of 1st Embodiment. The figure which showed the modification of 1st Embodiment. The figure which showed the modification of 1st Embodiment. The figure which showed the electric current distribution in a biological cross section. The figure which showed the biological model. The figure which showed the equivalent circuit of a living body. The figure which showed the cole-cole plot display of the bioelectrical impedance Z. FIG. The figure which showed the change of the bioelectrical impedance Z before and after muscle fatigue. The figure which showed the equivalent circuit of the living body which considered the complex impedance. The figure which showed the calculation example of Zall, Zin, and Zout. The figure which showed the structure of the muscle-fatigue measuring apparatus. The figure which showed the result of having calculated|required the electric current distribution inside a living body by the electromagnetic field simulation.

(First embodiment)
FIG. 1 is a diagram showing the configuration of a bioelectrical impedance measuring device according to the first embodiment. As shown in FIG. 1, the bioelectrical impedance measuring device of the first embodiment includes a pair of first electrodes 10, a pair of second electrodes 11, a pair of third electrodes 12, and a first current source. 13 , a second current source 14 , a first ammeter 15 , a second ammeter 16 , a voltmeter 17 , and a calculator 18 . The first current source 13, the second current source 14, the first ammeter 15, the second ammeter 16, the voltmeter 17, and the calculator 18 correspond to the measuring section of the present invention.

The first electrode 10 is an electrode that is brought into contact with a living body and is an electrode for measuring voltage applied to the living body. A pair of first electrodes 10 are spaced apart at predetermined positions on the living body. The shape of the electrodes is circular. Other shapes such as rectangles and squares may also be used. Also, the electrode material is Au, Al, Cu, Ag/AgCl, or the like.

The second electrode 11 is an electrode that is brought into contact with a living body, and is an electrode for applying current to the living body. The pair of second electrodes 11 are spaced apart on a straight line connecting the pair of first electrodes 10, and are arranged such that the pair of first electrodes 10 are inside the pair of second electrodes 11. be. The shape and material of the electrode are the same as those of the first electrode 10 .

The third electrode 12 is an electrode that is brought into contact with the living body, and is an electrode for applying current to the living body. The pair of third electrodes 12 are arranged separately on a straight line connecting the pair of first electrodes 10, and the pair of second electrodes 11 are arranged inside the pair of third electrodes 12. be. The shape and material of the electrode are the same as those of the first electrode 10 .

The first current source 13 is a current source for applying current to the living body via the second electrode 11 . Both ends of the first current source 13 are connected to the first ammeter 15 and the second electrode 11, respectively. The current applied to the living body has a frequency of 1 kHz to 1 MHz and 500 μA or less.

The second current source 14 is a current source for applying current to the living body via the third electrode 12 . Both ends of the second current source 14 are connected to the second ammeter 16 and the third electrode 12, respectively. The current supplied to the living body is the same as that of the first current source 13, with a frequency of 1 kHz to 1 MHz and 500 μA or less. The current from the first current source 13 and the current from the second current source 14 are controlled so as not to flow at the same time, but only one of them. For example, control is performed so that current is supplied alternately at intervals of 1 to 10 ms.

The first ammeter 15 is a device that measures the current value of the current I1 flowing through the living body via the second electrode 11 .

The second ammeter 16 is a device that measures the current value of the current I2 flowing through the living body via the third electrode 12 .

The voltmeter 17 is a device that is connected between the first electrodes 10 and measures the voltage between the first electrodes 10 .

The calculation unit 18 calculates the internal impedance of the living body from the current values measured by the first ammeter 15 and the second ammeter 16 and the voltage value measured by the voltmeter 17, and evaluates the degree of muscle fatigue. is. The details will be described later.

Next, a method for measuring bioelectrical impedance according to the first embodiment will be described.

FIG. 2 is a diagram showing the structure of the arm of a living body, and FIG. 3 is a diagram showing its equivalent circuit. As shown in FIG. 2, the arm of a living body has a bone structure in the center, muscle around it, a layer of fat on the outside of the muscle, and skin on the outside of the fat. Therefore, the impedance of the entire arm of the living body can be approximated by the parallel impedance of skin impedance, fat impedance, muscle impedance, and bone impedance. Among these, fat and bone have relatively low conductivity. Therefore, as shown in FIG. 3, it can be further approximated by the parallel impedance of the impedance of the skin and the impedance of the muscle.

Here, during muscle exercise, a lot of blood flows into the muscle and its conductivity changes. Therefore, if the muscle conductivity can be measured, the degree of muscle fatigue can be evaluated. However, when sweating occurs simultaneously with muscle exercise, the electrical conductivity of the skin changes significantly. In measuring the impedance of the entire cross section of the arm of the living body, there are two factors of variation, the blood volume in the muscle and the amount of perspiration.

Therefore, in the first embodiment, the impedance inside the living body is measured as follows. A current I1 is supplied to the living body through the second electrode 11 by the first current source 13, and the current value and voltage value at this time are measured by the first ammeter 15 and the voltmeter 17, respectively. Then, the impedance Zout is calculated by dividing the voltage value by the current value.

On the other hand, the current I2 is passed through the living body through the third electrode 12 by the second current source 14, and the current value and voltage value at this time are measured by the second ammeter 16 and the voltmeter 17, respectively. Then, the impedance Zall is calculated by dividing the voltage value by the current value.

The third electrode 12 is spaced widely, the second electrode 11 is arranged inside the third electrode 12, and the space between the electrodes is short. Therefore, the current I2 is distributed from the surface to the inside of the living body, while the current I1 is distributed unevenly on the surface of the living body. Therefore, the impedance Zout can be approximated to the impedance of the biological surface, and the impedance Zall can be approximated to the impedance of the entire biological cross section.

FIG. 15 is a diagram showing results obtained by electromagnetic field simulation of the current distribution inside the living body. FIG. 15(a) shows the distribution of the current I2, and FIG. 15(b) shows the distribution of the current I1. The biological model is as shown in FIG. 2, and the outer diameter of bone is 20 mm, the thickness of muscle is 30 mm, the thickness of fat is 7 mm, the thickness of skin is 3 mm, and I1 and I2 are 500 Hz. Also, the electrical conductivity was 0.34 S/m for skin, 0.4327 S/m for fat, 0.351828 S/m for muscle, and 0.02064 S/m for bone. As shown in FIG. 15, the current I2 is distributed deep inside the living body, whereas the current I1 is concentrated on the surface of the living body.

Here, as shown in FIG. 3, the impedance Zall of the entire cross section of the living body can be approximated to the parallel impedance of the impedance Zout on the surface of the living body and the impedance Zin inside the living body. Therefore, if Zout and Zall are obtained, Zin can be calculated by Zin=Zout×Zall/(Zout−Zall). Thus, the calculator 18 calculates the impedance Zin inside the living body from the measured values of the first ammeter 15 , the second ammeter 16 and the voltmeter 17 . Since the impedance Zin inside the living body can be approximated to the impedance of muscles, it can be used for various evaluations of muscles, such as the degree of muscle fatigue.

As described above, according to the first embodiment, the impedance inside the living body can be measured with a simple configuration.

Next, a more detailed model of the living body and measurement of muscle fatigue will be described.

In general, bioelectrical impedance is treated as complex impedance. FIG. 8 shows the current flow in the living body. As shown in FIG. 8, the cell membrane has capacitance, and at low frequencies the current bypasses the cell and flows through the external fluid. On the other hand, at high frequencies, current flows not only in the external fluid but also in the internal fluid inside the cell. FIG. 9 shows an equivalent circuit of a living body. As shown in FIG. 9, where Re is the resistance of the extracellular fluid, Ri is the resistance of the intracellular fluid, and Cm is the capacitance of the cell membrane, it is represented by a series connection of Cm and Ri and a parallel connection of Re. At low frequencies, the current flows on the Re side as shown in FIG. 9(a), and at high frequencies it flows on both sides as shown in FIG. 9(b). FIG. 10 is a cole-cole plot representation of bioelectrical impedance Z. FIG. Theoretically, the lower the frequency, the closer to Re, and the higher the frequency, the closer to Re//Ri (parallel resistance of Re and Ri).

When a muscle is tired, blood flows to the muscle. Since the conductivity of blood is higher than that of muscle, bioelectrical impedance Z decreases with muscle fatigue. FIG. 11 shows the bioelectrical impedance Z of muscle before and after fatigue. As shown in FIG. 11, since the real part of Z decreases due to muscle fatigue, the degree of muscle fatigue can be evaluated by evaluating the amount of change by measuring the impedance inside the living body.

However, there are individual differences in the real part of Z, and it may be difficult to evaluate the degree of muscle fatigue based only on the amount of change in the real part of Z. Therefore, by using changes in the intracellular and extracellular fluid resistance ratio Re/Ri and changes in the impedance ratio in the living body at different frequencies as evaluation indices, errors due to individual differences can be reduced and muscle fatigue can be estimated more accurately. can be measured. The ratio of the impedance inside the body at different frequencies is, for example, the ratio of the impedance inside the body at low frequencies and the impedance inside the body at high frequencies. Low frequencies are, for example, 100 Hz to 10 kHz, and high frequencies are, for example, 100 kHz to 10 MHz.

FIG. 12 is an equivalent circuit of a living body considering complex impedance. In the case of such a circuit as well, the impedance inside the living body can be measured by Zin=Zout×Zall/(Zout−Zall). FIG. 13 is a calculation example of Zall, Zin, and Zout. It can be confirmed that the impedance Zin inside the living body can be calculated even when the complex impedance is taken into consideration.

Next, a preferable range of the distance between the electrodes will be described. The wider the distance between the electrodes through which the current is applied, the deeper the current can be applied. Therefore, it is preferable that 0.1≦L1/D1≦5, where D1 is the thickness of the part of the living body whose internal impedance is to be measured, and L1 is the distance between the third electrodes 12 . By setting L1 to be approximately the same as D1, it is possible to allow the current to flow deep into the device while miniaturizing the device. Also, the current flowing through the second electrode 11 must be localized on the skin of the living body. Therefore, it is preferable that 0.1≦L2/D2≦5, where D2 is the skin thickness of the part of the living body whose internal impedance is to be measured, and L2 is the interval between the second electrodes 11 . By making L2 approximately the same as D2, the current is localized to the skin portion of the living body. In terms of the arrangement of the electrodes, L3<L2<L1 is satisfied, where L3 is the interval between the first electrodes 10 . The interval L3 between the first electrodes 10 may be set arbitrarily within a range that satisfies 0<L3<L2.

FIG. 14 is a diagram showing the configuration of a muscle fatigue measuring device using the bioelectrical impedance measuring device of the first embodiment. As shown in FIG. 14, the muscle fatigue level measuring device is a bandage type device, and an adhesive is applied to one surface (referred to as the back surface) of an insulating sheet 21 . A first electrode 10, a second electrode 11, and a third electrode 12 are arranged on the back surface of the insulating sheet 21 in the same manner as in the first embodiment. In addition, on the surface of the sheet 21, the first current source 13, the second current source 14, the first ammeter 15, the second ammeter 16, the voltmeter 17, the calculation unit 18, and the display unit 20 are integrated into one. the device is installed. The back surface of the sheet 21 is attached to the living body, the first electrode 10, the second electrode 11, and the third electrode 12 are brought into contact with the living body, and the impedance inside the living body is measured in the same manner as in the first embodiment. The calculator 18 estimates the degree of muscle fatigue from the calculated change in impedance inside the living body. The display unit 20 displays the estimated degree of fatigue in characters or the like. For example, the degree of fatigue is determined in three stages of low, medium, and high, and displayed as "high degree of fatigue".

Instead of or in addition to the display by the display unit 20, the fatigue level may be notified by an alarm, voice, or the like. Also, instead of or in addition to the display unit 20, a wireless communication device such as Bluetooth (registered trademark) may be provided. Information on the degree of muscle fatigue obtained by the calculation unit 18 is transmitted by a wireless communication device, received by a wireless communication terminal such as a smartphone or a tablet terminal, and displayed on the wireless communication terminal. can be notified by In this case, the calculator 18 may be an application installed in the wireless communication terminal.

(Modification 1)
As shown in FIG. 4, the shape of the second electrode 11 may be an arcuate shape protruding toward the first electrode 10 side. If it is linear extending in the direction perpendicular to the straight line connecting the first electrodes 10, it does not have to be a circular arc. With such an electrode shape, the current distribution on the surface of the living body when the current is passed through the second electrode 11 and the current distribution on the surface of the living body when the current is passed through the third electrode 12 are obtained. are equivalent to each other, and the impedance inside the living body can be obtained with higher accuracy. As shown in FIG. 5, where x is the length of the second electrode 11 (the length in the direction perpendicular to the straight line connecting the first electrodes 10), L1 is the interval between the third electrodes 12, and L2 is the interval between the second electrodes 11, x is preferably 0.8≦(2(L1−L2)) ^1/2 ≦1.2. Within this range, the current distribution on the surface of the living body when the current is passed through the second electrode 11 and the current distribution on the surface of the living body when the current is passed through the third electrode 12 can be brought closer to the same level. be able to.

(Modification 2)
As shown in FIG. 5, only the first current source 13 is used as the current source, and a pair of switches 19 are provided so that the switch 19 switches the connection between the first current source 13 and the second electrode 11 and the third electrode 12. You may FIG. 5(a) shows a state in which the first current source 13 and the third electrode 12 are connected. FIG. 5(b) shows a state in which the first current source 13 and the second electrode 11 are connected. With this configuration, only one current source and one ammeter are required, and the size and cost of the device can be reduced.

(Modification 3)
In the first embodiment, the current I1 from the first current source 13 and the current I2 from the second current source 14 are alternately supplied. However, as shown in FIG. The current I2 from the current source 14 may be reversed in phase and flowed at the same time. In this case, the current distribution in the cross section of the living body is as shown in FIG. As shown in FIG. 7, the current I1 flowing through the living body via the second electrode 11 from the first current source 13 is distributed on the surface of the living body. On the other hand, the current I2 flowing through the living body via the third electrode 12 from the second current source 14 is distributed not only on the surface of the living body but also inside the living body. Here, the current I1 and the current I2 are in opposite phase. Therefore, the current is canceled on the surface of the living body, and the current is mainly distributed inside the living body. By measuring this current value with the second ammeter 16 and measuring the voltage with the voltmeter 17, the impedance inside the living body can be calculated. In short, while the first embodiment is configured to remove the surface impedance by calculation processing, the modified example 3 is configured to physically remove the surface impedance.

When the currents I1 and I2 are opposite in phase and flow simultaneously as in Modification 3, the amplitude of the currents I1 and I2 is 0.1×(L2/L1) ² <k<(I1=k×I2). L2/L1) should be set to ² . If k is set in this manner, I1'<I2' can be established in any region, where I1' is the current density of the current I1 and I2' is the current density of the current I2. In particular, the current can be greatly canceled on the surface of the living body, and the current density can be increased inside the living body. As a result, the influence of impedance fluctuations on the surface of the living body can be further reduced, and the measurement sensitivity of impedance fluctuations inside the living body can be enhanced.

INDUSTRIAL APPLICABILITY The present invention can be used to measure muscle fatigue.

10: first electrode 11: second electrode 12: third electrode 13: first current source 14: second current source 15: first ammeter 16: second ammeter 17: voltmeter 18: calculator 19: switch 20: Display unit 21: Sheet

Claims (10)

a pair of first electrodes to be brought into contact with a living body;
A pair of electrodes to be brought into contact with the living body, the second electrode being spaced apart on a straight line connecting the pair of first electrodes and arranged such that the pair of first electrodes are inside. and,
A pair of electrodes to be brought into contact with the living body, the third electrode being spaced apart on a straight line connecting the pair of first electrodes and arranged such that the pair of second electrodes are inside. and,
A current is passed through the living body through the second electrode, the current value is measured, the voltage value between the first electrodes is measured, the surface impedance of the living body is measured, and the surface impedance of the living body is measured through the third electrode. An electric current is passed through the living body, the current value is measured, and the voltage value between the first electrodes is measured to measure the impedance of the entire cross section of the living body. a measuring unit that calculates the impedance inside the living body from the impedance;
A bioelectrical impedance measuring device comprising: 2. The measuring unit according to claim 1, further comprising a switch for switching between one current source and connection between the current source and the second electrode and connection between the current source and the third electrode. A device for measuring bioelectrical impedance as described. a pair of first electrodes to be brought into contact with a living body;
A pair of electrodes to be brought into contact with the living body, the second electrode being spaced apart on a straight line connecting the pair of first electrodes and arranged such that the pair of first electrodes are inside. and,
A pair of electrodes to be brought into contact with the living body, the third electrode being spaced apart on a straight line connecting the pair of first electrodes and arranged such that the pair of second electrodes are inside. and,
A first current is passed through the living body through the second electrode, and at the same time, a second current opposite in phase to the first current is passed through the living body through the third electrode, and the current value is measured in this state. a measuring unit that measures the voltage value between the first electrodes and calculates the impedance inside the living body;
A bioelectrical impedance measuring device comprising: The second electrode according to any one of claims 1 to 3, characterized in that the second electrode has a linear shape extending in a direction perpendicular to a straight line connecting the pair of first electrodes. A device for measuring bioelectrical impedance. 5. 0.1≦L1/D1≦5, where D1 is the thickness of the part of the living body whose internal impedance is to be measured, and L1 is the distance between the third electrodes. The bioelectrical impedance measuring device according to any one of 1. 1 to 5, wherein 0.1≦L2/D2≦5 is satisfied, where D2 is the skin thickness of the part of the living body whose internal impedance is to be measured, and L2 is the interval between the second electrodes. 6. A bioelectrical impedance measuring device according to any one of items 1 to 5. 7. The bioelectrical impedance measuring device according to any one of claims 1 to 6, wherein the measuring unit evaluates the degree of muscle fatigue from changes in impedance inside the living body. 8. Any one of claims 1 to 7, wherein the measuring unit measures the internal impedance of the living body at different frequencies, and evaluates the degree of muscle fatigue based on changes in the impedance ratio. The bioelectrical impedance measuring device according to the above item. A pair of first electrodes and a pair of electrodes, which are spaced apart on a straight line connecting the pair of first electrodes, and arranged such that the pair of first electrodes are inside. two electrodes; a third electrode, which is a pair of electrodes and is spaced apart on a straight line connecting the pair of first electrodes, and arranged such that the pair of second electrodes are inside; in contact with the living body,
applying a current to the living body through the second electrode and measuring the current value and measuring the voltage value between the first electrodes to measure the surface impedance of the living body;
applying a current to the living body through the third electrode and measuring the current value and measuring the voltage value between the first electrodes to measure the impedance of the entire cross section of the living body;
calculating the impedance inside the living body from the impedance of the surface of the living body and the impedance of the entire cross section of the living body;
A bioelectrical impedance measuring method characterized by: A pair of first electrodes and a pair of electrodes, which are spaced apart on a straight line connecting the pair of first electrodes, and arranged such that the pair of first electrodes are inside. two electrodes; a third electrode, which is a pair of electrodes and is spaced apart on a straight line connecting the pair of first electrodes, and arranged such that the pair of second electrodes are inside; in contact with the living body,
A first current is passed through the living body through the second electrode, and at the same time, a second current opposite in phase to the first current is passed through the living body through the third electrode, and the current value is measured in this state. and calculating the impedance inside the living body by measuring the voltage value between the first electrodes;
A bioelectrical impedance measuring method characterized by:

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