WO2016005915A2

WO2016005915A2 - A device, for example in the form of a watch, a bracelet, a belt or an auto-adhesive plaster, capable of monitoring the variations of the body hydration condition, in particular during the performance of sports activities

Info

Publication number: WO2016005915A2
Application number: PCT/IB2015/055162
Authority: WO
Inventors: Andrea TELLATIN; Antonio Talluri
Original assignee: Si14 S.P.A.
Priority date: 2014-07-08
Filing date: 2015-07-08
Publication date: 2016-01-14
Also published as: WO2016005915A3

Abstract

The present invention concerns a device (1) for the self-measurement of the body hydration condition of a subject and comprising: - A generator (G) for generating a voltage; - First means (a-a' ) for injecting in the subject a first current (I1) obtained through the generator (G); - Second means (b-b') to obtain a delivery current (12) circulating in the subject as a consequence of the first current (I1) injected; - Measurement means (V) to obtain a measure of the body hydration condition on the basis of the current injected (I1) and of the delivery current (12) detected. In accordance with the invention, the device is configured to result to be applicable to the body of a subject in such a way as to result to be transportable, preferably applicable to one of the extremities or to the torso.

Description

TITLE

A DEVICE, FOR EXAMPLE IN THE FORM OF A WATCH, A BRACELET, A BELT OR AN AUTO-ADHESIVE PLASTER, CAPABLE OF MONITORING THE VARIATIONS OF THE BODY HYDRATION CONDITION, IN PARTICULAR DURING THE PERFORMANCE OF SPORTS ACTIVITIES

Technical field

The present invention concerns the technical field relative to the instruments for the monitoring and evaluation of the variations of the body hydration condition .

In particular, the invention refers to an innovative device, in particular an apparatus that can have the form of a watch, bracelet, belt or self-adhesive plaster which, when normally brought to one of the body extremities, for example to the wrist or to the arm of the user, is capable of detecting, monitoring and comparing continuously, at pre-determined intervals or upon request, the variations of the body hydration condition of the user and referred to a basal line of reference, as a check of itself.

Background art

It is known that the determination in the human body of the electrical parameters of resistance R and reactance Xc, or the measurement of the module of impedance Z obtained at at least two frequencies of significantly different value (for example, non limiting to 5 kHz and to 200 kHz) , are useful to identify the volume proportions of the intra/extra cellular fluids without the need to be implemented with known formulas, in order to obtain the volume thereof.

For example, the known art regarding this refers to the articles of Thommasset "Proprietes bio-electriques des tissus" or articles of Prof. J. Nyboer or Dr. W.C. Chumlea .

The hydration condition in men is classified (in terms of hypo, normo, hyper) not by the total quantity of the fluids (Total water or TBW "Total Body Water") referred to the body weight, but rather by the percentage of the fluids contained in the lean mass (TBW/FFM) .

In that sense, scientific articles in this regard have been written by authors such as Olesen, Moore and others.

The Italian patent application entitled "A procedure and a domestic device for the self-check of the degree of hydration of a subject" under publication number ITFI20050202 , describes in fact an apparatus that allows the patient to take a self-measurement for monitoring the variations of its own body hydration condition.

To that aim, a generator has been foreseen capable of generating an alternate voltage reference signal, deliverable at at least two frequencies (5-100Khz) , which is injected in the patient through pairs of plates or electrodes. In the case of plates, these are grasped by the hand of the patient with the thumb and fingertips of the remaining fingers. In that manner, the electrical signal is injected through a plate and went through the body that serves as conductor to reach the opposite plate. In particular, the current injected goes through the plates on which the fingertips of the fingers of both hands rested. A voltmeter connected to the thumbs measures the voltage from which to detect the impedance (system known as tetra-polar bioelectrical impedance analysis) . In that manner, it was possible to derive relations of impedance at the two frequencies, to obtain a hydration condition .

It is also known the method of the analysis of the signal with statistics methodology called bivariate vector of the values of R and Xc which is, for example, described in patent US20040167423 and to which reference has to be made for all the bases of interpretation of the same.

The knowledge, therefore, of said electrical parameters, allows to classify or monitor the body hydration condition.

The knowledge of the body hydration condition on the human being is very important in various medical/clinical/sports sectors.

In fact, an anomalous hydration condition can be indicative of various pathologies, also serious ones.

In the sports field, the knowledge of the body hydration condition can result to be extremely useful for the athlete to understand when it is necessary to reintegrate the body fluids, above all to solicit the reintegration at the right moment, for example during a competition or a training session. It is known that a loss of body fluids of about the 2% or more is enough to influence the performance negatively.

At the current state of the art, there does not exist any wearable device at one of the extremities of the body capable of giving this information to a subject that is making for example sport, physical or working activity that determines important quick hydration variations.

In the same manner, at the current state of the art, there does not exist any wearable device capable of giving this information to a subject that in a comfortable and precise manner wants to determine the variation or stability of the own hydration condition during the day (for example also during a walk, or during a work in a hot and humid environment) .

This is because, even though di per se machineries to estimate the body hydration through bioelectrical impedance analysis measurements are known, these machineries are not idoneous to be transported easily by the subject during its physical activity since, naturally, they are very heavy and bulky.

Moreover, some of such devices base their calculation on known formulas which, apart from being always precise, are applicable only where the measure is detected in a significant segment of the body, which implies the realization of bulky devices.

Disclosure of invention

It is therefore the aim of the present invention to provide an innovative device that allows to solve said technical inconveniences.

In particular, it is the aim of the present invention to provide a portable and compact device, therefore for example in the form of a watch, a bracelet, a belt or a self-adhesive plaster (Patch) that can be applied comfortably without creating encumbrance, obstacles and bother for the user and that is capable of detecting the body hydration.

In particular, it is the aim of the present invention to provide a device that allows to monitor in a continuative manner the own condition of body hydration, for example during the performance of sports activity, without resulting to be heavy or bulky.

It is also the aim of the present invention to provide a device that results to be precise in the measurement of the hydration condition.

These and other aims are therefore obtained with the present device for the sel f-measurement of the body hydration condition of a subject, as per claim 1.

The device (1) comprises:

- A generator ( G) for generating a voltage; - First means (a-a' ) for injecting in the subject a first current (II) obtained through the generator (G) ;

- Second means (b-b' ) for receiving a delivery current (12) circulating in the subject as a consequence of the first current (II) injected;

Measurement means (V) for obtaining a measure of the body hydration condition on the basis of the current injected (II) and of the delivery current (12) detected, as per the tetra-polar technique.

In accordance with the invention, the device is in the form of a watch or of a strap in such a way as to result to be applicable to one of the extremities of a subject, preferably to the wrist, and result to be transportable.

In this way, the user, in particular the sportsman, can monitor the own body hydration condition during his training session and programme the re-integration of the liquids on the basis of the own specific needs. The watch has the advantage of integrating other functions generally known and already used in specific watches for sports activities .

Further advantages can be deduced from the dependent claims .

Brief description of drawings

Further features and advantages of the present device 1, as per the invention, will result clearer with the description that follows of some embodiments, made to illustrate but not to limit, with reference to the annexed drawings, wherein:

- Figure 1 and figure 2 both show schematically a device, for example a wristwatch, in accordance with the present invention;

- Figures 3 and 4 schematize the process of injection of current in one of the extremities of the body where applied;

- Figure 5 shows an electric scheme that is represented as an equivalent circuital model and highlights a portion of tissue with cells and extra-cellular material;

- Figure 6 schematizes a diagram of the measure that is taken;

- Figure 7 and figure 8 schematize a watch with the "display" on which the variation of the hydration condition is visualized.

Description of some preferred embodiments

Figure 1 describes a watch in accordance with the invention .

It is therefore highlighted a strap 20 that is connected to the case 25 of the watch containing all the components necessary for its functioning.

Naturally, the strap 20 and the case 25 can be realized in any way and with different materials, without for this moving apart from the present inventive concept.

In that sense, the representation of a hand watch is not to be considered limiting and obviously also a simple container, or box, of an idoneous volume and shape to hold the electronic circuits to execute the functions described below can be implemented, without for this moving apart from the present invention. Moreover, also eventual containers that have simultaneously also the function of watch, either digital, underwater, plastic, for sports activities ones, etc., can equally be implemented without for this moving apart from the present invention.

Further, as said, such a device does not have to necessarily be in the form of a watch, but it can also be in the form, for example, of a bracelet and further wearable on any one of the extremities of the body, not necessarily on the single wrist (for example, applicable to the ankle or to the torso) .

It is also plausible a solution wherein the form is that of a belt suitable to enclose the chest, for example, exactly as in the case of a heart rate monitor or of a plaster to apply to any part of the body.

In all cases it is therefore present a tape that forms the belt or the strap (variable measure according to where it is applied) and with the tape that foresees or is connected to the containment case of the electronic components and that allows the visualization of the measure .

In the same manner, the plaster is in fact a self- adhesive tape (in any material, obviously) and that contains a lodging case of the components.

The solution with the plaster is therefore identical to the preceding ones except for the fact that the tape foresees an adhesive layer to apply to the body in a removable manner (also more than once, obviously) .

In one of the infinite possibilities of realization you can, for example, foresee a closed ring in rubber (therefore highly deformable for adapting itself to various measures of wrist or torso) and having a seat into which the case is inserted with the components described. In this way, the ring would be interchangeable in different measures, colors and forms.

In all its embodiments, therefore, the device presents itself in such a shape as to result to be applicable to a part of the body, in particular or in the form of a tape that can wrap a part of the body or, as said, in the form of a plaster, and that foresees a case that contains the functioning components.

In this way, the object is compact and light, it does not foresee components separated from it and can therefore be comfortably used during the sports activity. The detailed description, below indicated and referred to the watch, and/or to one of its applications to a wrist, is not therefore to be considered limiting.

In accordance with the invention, the instrument foresees a case 25.

Figure 2 shows the same watch-shaped instrument of figure 1 but turned upside down, or the surface of the case 25 is visualized that is in direct contact with the wrist of the user when it is normally worn.

In that sense, the case 25, on the opposite side to that of visualization of all the parameters desired and measurable, foresees a surface (a-a' , 3) which goes in direct contact with the wrist of the user.

Such a surface (a-a', 3) foresees a dielectric 3 that separates and isolates between them two areas a-a' of metal or anyway in a conductive material.

The dielectric, as well known in the state of the art, is an isolator that separates between them the two conducting areas, impeding that there is a flow of current between an area (a) and the adjacent area (a' ) .

The two said conducting surfaces a-a' will result to be electrodes a-a' through which the current is injected in the human tissues by means of one contact thereof with the wrist when the watch is worn. Naturally, such electrodes a-a' can be such as to interest the entire case in terms of size but could also be in the "spot" shape, that is point-shaped.

They can be internal or external to the case and therefore in direct contact with the skin or not, provided that it is placed in a condition to inject current.

They are therefore integrated in the case, internally or externally to it.

The watch, or anyway the container, foresees inside it a generator of alternate current ( G ) , which can operate at a frequency or at two or more frequencies (for example 5Khz and lOOkhz) .

The generator (G) , placed inside the case, is connected, obviously, to the injectors (a- a' ) in a known way, for example with conductors and relative connectors or weldings. The generator creates a potential V and thus determines a first current flow (Ii) which results to be an inflow in the human body through the spots (a-a' ) or anyway the areas placed in contact with the wrist.

The system is provided with a mechanism of feed-back

(well-known and not further described) that permits to keep the delivery of the current constant (for example, not limiting to keep a constant current of 400 micro amperes, innocuous current, obviously, for the human body) .

The strap foresees two metallic areas, also eventually in the shape of bars or of "spots" (b-b' ) .

The two metallic areas (b-b' ) are connected to a Voltmeter (V) , preferably contained also it in the case 25. The two metallic areas (b-b') are obviously connected to the voltmeter (V) through normal electrical wires which, for example, can be made to pass through a channel obtained in the strap to conduct it to the case where the voltmeter (V) is placed.

The constant current generated by the generator (G) is therefore diffused in the tissues of the wrist, through the contacts a-a' . It is detected by the said conducting areas b-b' placed in a pre-determined point in the strap and connected to the voltmeter (V) , as per the classic bioelectrical impedance analysis with tetra-polar technique. In such a manner, the voltmeter measures a voltage drop.

The use of a measurement of tetra-polar impedance permits to minimize the effects of bother introduced by the skin-sensor contact which is particularly unstable during the sports practice.

Moreover, also the use of separate contacts allows, above all in the sports field, to reduce the measurement bother.

A' processor, as described in detail below, implements a calculation of detection of the hydration condition that is derived as a direct function of the electric measures detected, in particular on the basis of the voltage drop.

The processor is preferably arranged inside the case 25 as well.

In fact, therefore, the system can be compared to two normal electrodes, connected for injecting current, kept constant, and other two normal electrodes to detect the voltage with which the current goes through the segment under observation.

With reference to figure 3 and to figure 4, a phase of injection of current is shown.

The electrodes a-a' , for example contained in the case or in the immediate vicinity (highlighted in red and constructed in a rigid and/or soft bio-compatible material, anyway highly conducting), are connected to the generator ( G ) of constant current (of the sinusoidal type in the option of a sensor "sensitive to the phase" or sinusoidal or anyway pulsed indifferently in the rectangular, square, triangular bi-phasic form, in the option of multi-frequency technique) . Such electrodes inject in the wrist, or in the segment of the arm on which the instrument is placed, a micro current (of about 200 +/- 400 Micro-Amperes) which is kept of constant intensity and saturates the conducting body on which they rest and of almost cylindrical shape, as shown in the underlying figure 4 with saturation highlighted in red spray. The metallic electrodes b-b' , or of a soft material, but conducting and bio-compatible, are connected electrically through wires, or other, to said voltmeter (V), contained in the case as well, which determines the impedance (Z) of the conductor saturated by the constant micro current. The voltage values measured are digitalized, conditioned and sent to the microprocessor to be then transferred for visualization of the user on a display, once processed.

As shown in figure 3 and 4, in order to inject and detect the current in a correct way, it is preferable that the electrodes are arranged in the shape of a crown or hemicycle. This means that the imaginary line that joins the electrodes has to trace a continuous course, and particularly "in a waterfall-like manner" and "in line", as for example in figure 3.

The electrodes (b-b' ) can also be translatable, in order to modify their reciprocal distance along the strap. This allows to modify and arrange the correct position of the electrodes (b-b' ) on the basis of the size of the wrist of the user, making in such a way that the electrodes (b-b' ) are always positioned in the correct area (generally the soft sides of the wrist indicated as "anatomical snuffbox") . In the case of alternative positioning to that of the wrist, for example on a distal or proximal or dorsal limb (superior or inferior) , the reading electrodes (Voltmeter) will be adequately positioned to detect the circulating current on the greatest quantity of soft tissue possible.

If the aim is that of monitoring the variations of the hydration condition in a short term (within a few hours) , without the need or wish to classify them, the relation of fluids I/E (Intracellular on Extracellular) is sufficiently sensitive and specific in healthy subjects (sportsmen or anyway non pathological people) to indicate an eventual margin of increase or decrease of the hydration condition. This is because the variations in the short term (a few hours or a few days) of the proportion ICW/ECW (relation between intra-cellular and extracellular fluid) is almost totally in charge of the extracellular fluids .

In that sense, it is possible to obtain with precision a measure of the body hydration condition by measuring a non-dimensional index that is indicative precisely of the variation of conductibility of the extracellular.

In particular, during a training session or during motion in general, there is a loss of liquids, as said, that is mainly in charge of the extra-cellular (E) while the cells, which represent a conservative closed system, keep in a more or less unvaried way the quantity of liquid. In that sense, the intra-cellular varies in a negligible manner.

Having said that, if we change in a healthy subject the quantity of liquid mainly in the extra-cellular, obviously the conductivity of the single extra-cellular will change, which in fact becomes more resistive in case of loss of fluids, while the intra-cellular remains unvaried.

In that sense, physically, what happens is that the current, with the same current applied, is reduced in the extra-cellular as the body hydration condition diminishes, while in the intra-cellular it remains almost constant, since it does not change in the short term.

A sort of re-distribution of the currents takes place, which can be measured with precision not through known mathematical formulas of conversion of the electric measure taken, in order to obtain a hydration value (something complex di per se and possibly subject to error) , but using a simple non-dimensional numerical relation (non-dimensional index) based on such an electric measure executed with at least two frequencies or at one frequency but with sensitivity to the phase shift (phase angle) .

It is noted, in fact, precisely in accordance with such a solution addressed particularly to a "sports" use through a simple and light device which is easily wearable on one of the extremities of limb or around the body, it would not be absolutely possible to implement other methods of calculation of the hydration condition (for example, the use of known mathematical formulas that obtain the hydration condition always through the knowledge of the current injected and detected) . This is because we are observing a not significant segment of the body, that is one of the extremities of wrist or leg. Any equation to estimate the volumes is based on the concept of equation of the bioelectric volume, that is the volume of distribution of the current (and therefore of the fluids) which is based on the known formula D^A2/R, that is length squared divided by impedance. In that sense, it is clear that the segment observed in crown does not permit to estimate the volume. For the volume of the segment it would be necessary to take the tetra-polar measure longitudinally. Therefore, the so-called structural solution would not permit other implementations of calculation other than the one described below, precisely by virtue of its conformation.

In a first embodiment of the invention, the measure can be taken of the value of impedance Z at two different frequencies that are sufficiently spaced one from the other (for example at 5khz - low frequency (Zi) and lOOkhz high frequency (Zh) ) and determining a relation (therefore a non-dimensional index) Z_low- frequency/Z_high_frequency, that is Z5/Z100. This non- dimensional index is then compared to a same relation made in an initial condition taken as reference.

In particular, a body system can be assimilated to a circuit (R, C) represented in figure 5 and representing an assembly of cells (I) and an extra-cellular assembly (E) , where R is the resistive equivalent conductor of the interstitial fluids and C is the equivalent effect of a condenser generated by the cellular membranes.

Initially, a measure is taken in rest condition (for example, as soon as you wake up in the morning or before physical activity) . The device injects current to the two frequencies and calculates, shows, and if necessary memorizes their relative value (relation Z5/Z100) .

It is reminded that the impedance Z is in fact the vector obtained in the complex plane and composed by the components of resistance R and reactance Xc. It is measured in Ohm and is detected with the Voltmeter (V) . In particular, the generator (G) injects a certain voltage and, through a feedback system, the inlet current is kept constant, for example 500 micro-Amperes. The voltmeter detects the voltage at the ends of the spots (b-b' ) and measures the impedance as the relation between the current injected (for example, the said 500 microamperes) and the voltage measured at the ends of the spots (b-b') (for example 3V) .

In the case, instead, of sensitivity to the phase, the direct relation between the reactance and the resistance is calculated, which can eventually be rendered with angular value with the formula:

Phase angle = arctangent (Xc/R) x 180/π;

In a sequential manner, in initial condition, a current at a first frequency is injected and the voltmeter detects the first value of Z at said frequency (Zs) . Immediately afterwards, a sequence of injection of current at a value of high frequency takes place and, in the same manner, the voltmeter measures a value of impedance Zioo, therefore at high frequency. The processor receives these two measures and calculates the relation between the two impedances, thus determining a pure number (relation between the two impedances Zs/Zioo) .

This measure has been taken, as said, in a condition of normal hydration (good quantity of hydration in the extra and in the intra-cellular ) , that is before a training session, a competition, etc. The non-dimensional number will therefore be a reference value that is indicative, in the healthy subject, of its hydration basal reference condition.

During any sports activity there is a certain loss of liquids that, as said, takes place mainly in the extracellular. All this changes, obviously, the conduction state (it becomes more resistive) only and exclusively of the extra-cellular area.

The new relation that is measured ( Z_l/Z_h) fin in a certain moment of the day (for example during a training session) changes with respect to the reference index initially measured since, being the extra-cellular less conductor, they substantially change in mode not correlated among them the measures of Z at low and high frequency (this is because the extra-cellular hydration condition has changed) .

As shown in figure 6, the two relations (that of "basal" reference and that "measured in the course of activity") will have a deviation that will depend on the quantity of liquid lost, loss that has modified, as said, the conduction of extra-cellular current.

This deviation (Δ) is therefore indicative of a variation of the hydration state with respect to the condition of rest measurement, and is therefore indicative of a measure of loss of liquid.

Such a deviation can easily be visualized in an indicative measure of the deviation and can be obtained, for example, through a relation between reference basal measure and that taken at a certain moment.

(Z5/Z l 00)in

Δ

Alternatively, the measure that indicates hydration loss can be obtained with a difference:

Unlike known machineries, known formulas are not used that convert the electric measure in measures of intra and extra cellular volume and this, obviously, simplifies significantly, in terms of software, the device and can reduce, above all, the margin of error.

Such a type of measurement can be used also for checking the quality of the measure itself.

In fact, the value of Z_low_frequency has to result to be always higher of the value of Z_high_frequency since with the increase of the frequency there increases also the volume of distribution of the current, which from mainly extracellular in low frequency passes to be also and always more intracellular with the increase of the frequency. In that sense, a verifying programming of such values can be foreseen in such a way as to annul the measurement and repeat it in case Z_high_frequency results to be greater or equal to the measure of Z_low_frequency .

It is important that the two frequencies are separated by at least an order of magnitude (for example 5khz and lOOkhz) since this allows to render significant the relation which, otherwise, would be close to 1.

In a possible variant of the invention, it is possible to use the same methodology but measuring, as said, the phase of current (indexed measure).

Exactly like in the preceding case, it is measured in initial condition, at rest, a phase of current by injecting in this case a single-frequency current and determining a first index at rest (Xc/Riniz) .

During the training session the system will inject the same frequency to measure the new relation of phase that has been modified as a consequence of the loss of hydration (Xc/Rfin) .

The next step is the same calculation of the relation that will be indicative of the variation of the hydration condition.

Xc/Riniz

Δ = -

Exactly like in the preceding case, also a difference can be used to indicate the variation of the hydration condition.

Figure 7 shows in a non-limiting way a schematization that highlights a "display" of visualization of the hydration index measured.

In use, therefore, a user can take a measure at the beginning of the day, for example as soon as he has woken up. To that aim, he controls the injection of the current at the two frequencies and the system memorizes a first non-dimensional reference index that can be, as said, a relation or a difference of impedances.

In the case of phase, a single frequency is injected. It is preferable, in that case, a value of frequency of 50khz which allows better to monitor the electric behavior of the body and its variations. In particular, the frequency in the proximal range to the 50 kHz is that in which the greatest phase shift in the human tissues is registered, and is therefore the frequency most favorable to measure the delay between voltage and current (phase) .

During a training session, competition or anyway during the day, it is possible to request a new hydration index through a specific button that will activate the device, in such a way that the screen 6 visualizes in numerical terms what has been processed.

In particular, the system, when initialized, can memorize a reference value that can be kept in memory or can be updated every time (that is updated day by day or when the user desires it) .

During, for example, a training session, it is possible to take the measure by pressing a specific button of activation that activates the injection of current at the two different frequencies (or at a single one in case of phase) in such a way as to calculate the new relation of non-dimensional indexes (be them phase or impedance). The processor processes a relation or a difference between the two indexes measured (initial and during the training) and extrapolates a number that is indicative of the hydration condition, therefore for example of a percentage of loss of liquid.

The system can be automatized in various ways.

For example, once the training session has started, it is enough to press just once a start button and, in pre-determined intervals of time, the processor will send the current to take the measures that will be every time visualized and eventually memorized.

Alternatively, the user can manually control every time the start of a measure.

Naturally, the system lends itself well to other integrations. For example, a critical threshold of loss of liquids can be memorized and foresees a sound or a led light of illumination (like also notices on the display) to indicate the reaching of a critical hydration threshold .

In the case of remote monitoring of a trainer the sending of the significant values (proportions Zl/Zh or variations of phase) is foreseen in telemetry, for example on an I-Phone device with specific application.

Naturally, even if the present invention is addressed mainly to a sports use, its use can also be that of a normal self-monitoring with the purpose of preventing dangerous pathologies connected to anomalous hydration condition or anyway an everyday monitoring for verifying the own wellness state.

Claims

1. A device (1) for the self-measurement of the body hydration condition of a subject and comprising:

- A generator (G) for generating a voltage;

- First means (a-a' ) for injecting in the subject a first current (Ii) obtained through the generator (G) ;

- Second means (b-b' ) for receiving a recovery current (I2) circulating in the subject as a consequence of the first current (Ii) injected;

- Measurement means (V) for obtaining a measure of the body hydration condition on the basis of the current injected (Ii) and of the delivery current (I2) detected in accordance with the tetra-polar technique;

Characterized in that the device is in the form of a watch or a strap in such a way as to result to be applicable to one of the extremities of a subject, preferably the wrist, and to be transportable.

2. A device (1), as per claim 1, wherein the watch or the strap both foresee a screen (6) to visualize the datum of hydration detected.

3. A device (1), as per claim 1 or 2, wherein a case (25) is foreseen comprising:

- The generator (G) ;

- The measurement means (V) to obtain a measure of the body hydration condition and;

- The first means (a-a' ) .

4. A device (1), as per claim 1 or 3, wherein said measurement means (V) comprise a Voltmeter that measures the voltage drop and said first means (a-a' ) are in the form of a pair of electrodes (a-a' ) .

5. A device (1), as per claim 4, wherein said pair of electrodes (a-a' ) are separated between them by a dielectric ( 3 ) .

6. A device (1), as per one or more of the preceding claims, wherein said pair of electrodes (a-a' ) are applied on the external surface of the case on the part destined to be in contact with the user.

7. A device (1), as per one or more of the preceding claims, wherein said second means (b-b' ) are in the form of a pair of electrodes (b-b' ) arranged externally and spaced from the case (25) and, in the case of a watch-like form, are placed along the strap (20) foreseen in the watch.

8. A device (1), as per claim 7, wherein said pair of electrodes (b-b' ) is adjustable at different reciprocal distances.

9. A device (1), as per one or more of the preceding claims, wherein said measurement means are configured to obtain the measure of the body hydration condition through the determination of a first non-dimensional index (Z5/Z100; (pin) , indicative of the condition of electrical conduction of the subject in a predetermined instant of reference, a second non- dimensional index (Z5/Z100; cpf in) , indicative of the condition of electrical conduction of the subject in a subsequent instant, and a comparison between said two non-dimensional indexes.

10. A device (1), as per claim 9, wherein said comparison comprises the determination of a relation between said first and second non-dimensional index or an algebraic difference between said first and second non- dimensional index.

A device (1), as per claim 9 or 10, wherein said first non-dimensional index (Zs/Zioo; (pin ) and said second non-dimensional index (Z5/Z100; (pfin ) can be at choice:

- A relation of impedance (Zs/Zioo) calculated at two different frequencies, preferably separated by at least an order of magnitude, still more preferably starting from a low frequency inferior to lOkhz;

- A relation of phase ((ps) calculated at a single frequency, preferably at 50khz.

A device (1), as per one or more of the preceding claims, wherein said measurement means comprise a voltmeter (V) to obtain the measure of impedance (Z) or of phase (<p) of current and a processor that determines the condition of hydration through the value of impedance or of phase measured.