WO2022157541A1

WO2022157541A1 - Device for determining a fitness level

Info

Publication number: WO2022157541A1
Application number: PCT/IB2021/050442
Authority: WO
Inventors: Zhibo Chen
Original assignee: Zhibo Chen
Priority date: 2021-01-21
Filing date: 2021-01-21
Publication date: 2022-07-28

Abstract

A device (1, 100) for determining a fitness level of a user. The device (1, 100) comprises a main body (10) including a recessed portion (20) for receiving a user's sweat and a sweat sensing electrode (30, 110) in the recessed portion (20) for contacting the user's sweat. The device (1, 100) furher comprises a front-end module (120) for processing a signal received from the electrode (30, 110) and a processor (130) for analysing the sweat based on a signal received from the front-end module (120). The device (1, 100) also includes an output module (140) for outputing an indication of the fitness level of the user in response to a signal from the processor (130).

Description

DEVICE FOR DETERMINING A FITNESS LEVEL

BACKGROUND

Physical fitness can be measured by a variety of ways including muscle strength, flexibility, body composition etc. However, when there is no objective measurement, people tend to overestimate their fitness level, which can lead to over-exertion and injury. Scales with bioelectric impedance analysis allow a user to measure their weight and also estimate their body composition such as percentage body fat. Meanwhile, pulse monitors allow a user to check their heart rate before, during and after exercise. However, bio-electric impedance machines are expensive and cannot be used outside of the gym, while heart rate monitors only provide limited feedback with respect to heart rate and need to be kept in contact with the body during exercise.

SUMMARY

A first aspect of the present disclosure provides a device for determining a fitness level of a user, the device comprising: a main body including a recessed portion for receiving a user’s sweat, a sweat sensing electrode in the recessed portion for contacting the user’s sweat; a front-end module for processing a signal received from the sweat sensing electrode; a processor for analysing the sweat based on a signal received from the front-end module; and an output module for outputting an indication of the fitness level of the user in response to a signal from the processor.

The output module may for instance be a display or a wireless communications module. The front-end module may include circuitry to convert analogue signals from the sweat sensing electrode into digital signals and/or to condition analogue signals received from the sweat sensing electrode.

In some examples the front-end module may include a waveform generator to inject an excitation signal having a frequency to the sweat sensing electrode. In some examples, the front-end module or the processor may be configured to measure an admittance of the sweat based on a response of the sweat sensing electrode to the excitation signal. In some examples the front-end module or the processor may be configured to determine an analyte concentration of the sweat based on an electrical parameter of the sweat measured by the sweat sensing electrode.

BRIEF DESCRIPTION OF THE DRAWINGS Examples of the present disclosure will be explained below with reference to the accompanying drawings, in which:-

Fig. 1 shows a perspective view from above of a device according to an example of the present disclosure;

Fig. 2 is a schematic diagram showing components of a device according to an example of the present disclosure;

Fig. 3 shows an example of a protective lid for protecting a sweat sensing electrode of a device according to an example of the present disclosure;

Fig. 4 shows a perspective view from below of a device according to an example of the present disclosure;

Fig. 5 shows an example of an attachment member for use with a device according to an example of the present disclosure;

Fig. 6. shows an example a charging dock together with a device of Fig. 1 according to an example of the present disclosure;

Fig. 7 shows an example of the device of Fig. 1 when placed on a charging dock according to an example of the present disclosure;

Fig. 8 shows an example of a device according to the present disclosure in use when a drop of sweat is being deposited in a recess of the device;

Fig. 9 shows an example of a device according to the present disclosure in use when a user is pressing a button to active the device; and

Fig. 10 is a flow diagram showing an example method of determining a fitness level of a user by using a device according to an example of the present disclosure.

Fig. 11 A is a circuit diagram of an example sweat sensing electrode and analogue front end according to the present disclosure;

Fig. 11 B is a circuit diagram of another example sweat sensing electrode and analogue front end according to the present disclosure;

Fig. 11C is a circuit diagram of another example sweat sensing electrode and analogue front end according to the present disclosure;

Fig. 11 D is a circuit diagram of another example sweat sensing electrode and analogue front end according to the present disclosure; Fig. 12A is a diagram showing a structure of an example sweat sensing electrode according to the present disclosure;

Fig. 12B is a diagram showing a structure of another example sweat sensing electrode according to the present disclosure;

Fig. 12C is a diagram showing a structure of an example sweat sensing electrode according to the present disclosure;

Fig. 12D is a diagram showing a structure of an example sweat sensing electrode according to the present disclosure;

Fig. 12E is a diagram showing a structure of an example sweat sensing electrode according to the present disclosure;

Fig. 12F is a diagram showing a structure of an example sweat sensing electrode according to the present disclosure; and

Fig. 13 is a graph showing analyte concentration of a solution as determined according to measurements of electrical admittance versus the actual analyte concentration according to an example of the present disclosure;

Fig. 14 is a schematic diagram showing an assembly according to an example of the present disclosure; and

Fig. 15 is a schematic diagram showing components of a device according to a further example of the present disclosure.

DETAILED DESCRIPTION

Various examples of the disclosure are discussed below. While specific implementations are discussed, it should be understood that this is done for illustrative purposes and variations with other components and configurations may be used without departing from the scope of the disclosure as defined by appended claims. In the context of the present disclosure the terms “a” and “an” refer to one or more of a particular element.

It would be desirable to provide a device which is capable of determining the fitness level of a user. Such a device could, for example, be used to determine a suitable range of exercises for a person beginning a fitness programme and/or allow a person to track their progress as their fitness improves over time. The inventor has devised a device that analyses sweat content in order to determine a user’s fitness. Fig. 1 is a perspective view from above of one example of such a device. The device 1 includes a main body 10 including a recessed portion 20 for receiving a user’s sweat. At least one sweat sensing electrode 30 is provided in the recessed portion 20 and is configured for contacting sweat of a user which may be deposited by the user in the recessed portion. The device 1 further comprises an output module in the form of a plurality of light emitting diodes (LEDs) 40A, 40B, 40C which act as a display. In the example of Fig. 1, the device 1 further includes an activation button 50 and an aperture 60 at one end thereof.

Fig. 2 is a schematic diagram showing the components of an example device 100 for monitoring the fitness level of a user. The device 100 includes a sweat sensing electrode 110, a front-end module 120, a processor 130 and an output module 140.

It is to be understood that Fig. 1 and Fig. 2 are representative examples showing different aspects of a device for monitoring fitness level. Thus, the device of Fig. 1 may include any of the features shown in Fig. 2 and the device of Fig. 2 may include any of the features shown in Fig. 1. For instance, the electrode 110 in Fig. 2 may correspond to the electrode 30 in Fig. 1 and the output module 130 in Fig. 1 may be implemented as a display 40A, 40B, 40C as shown in Fig. 1. Meanwhile, while Fig. 1 does not show a processer or front end module, it is to be understood that such features may be provided inside the main body 10 of the device of Fig. 1.

The sweat sensing electrode 30, 110 is an electrode which is to contact sweat deposited in the cessed portion 20. The electrode may include a pattern of electrical contacts on a surface of the recessed portion and may include further structure below the surface. The electrode 30, 110 may be connected to the front-end module 120 by a first signal line formed of conductive material. A signal representative of an electrical parameter of the sweat may be conveyed over the first signal line from the electrode 30, 110 to the front-end module 120. The front-end module 120 is configured for processing a signal received from the sweat sensing electrode. For example the front-end module may include electrical components to measure an electrical parameter of sweat in contact with the electrical contacts of the sweat sensing electrode. The front-end module may include electrical circuitry to convert analogue signals from the sweat sensing electrode into digital signals and/or for conditioning analogue signals received from the sweat sensing electrode electrical. The signal conditioning may include filtering out noise and/or amplifying the analogue signals. The front-end module 120 may be connected to the processor 130 by a second signal line formed of conductive material.

The processor 130 may for example be a microprocessor, logic chip or central processing unit. The processor include memory as well as a processing unit. The processor 130 is configured for analysing the sweat based on a signal received from the front-end module 120. For example, the front-end module may send a signal representative of an electrical parameter of the sweat over the second signal line to the processor and the processor may determine a concentration of a sweat analyte based on the electrical parameter. The processor may compare the determined concentration of the sweat analyte with one or more thresholds stored in a memory to determine a fitness level of the user. In other examples, the front-end module may include electronic circuitry to determine the concentration of the sweat analyte and the processor may determine a fitness level of the user based on the concentration of sweat analyte communicated by the front-end module. The processor 130 is connected to the output module 140 by a third signal line formed of conductive material.

The output module 140 is configured for outputting an indication of the fitness level of the user in response to a signal from the processor 130 received over the third signal line. The output module 140 may for instance be a display for displaying a visual indicator of the fitness level. The display may include a screen to indicate the fitness level numerically or by means of a graphic such a bar of variable length. In other examples the display may include one or more light emitting diodes (LEDs) and indicate the fitness level by lighting a particular LED or a particular colour. In still other examples, the output module 140 may include a wireless communication module for sending an indicator of the fitness level wirelessly to a remote device. For instance the wireless communication module may Wifi chip or Bluetooth chip etc. In some examples the device may include both a display and a wireless communication module.

In the example shown in Fig. 1, the output module is a display comprising a plurality of LEDs 40A, 40B, 40C and at least one signal line connects the processor and the plurality of LEDs. Each LED of the plurality of LEDs may have a different colour, so that the fitness level can be indicated by lighting a particular colour of LED.

It will be appreciated from the above that the device includes a plurality of electrically conductive signal lines for conveying signals between the electrode, front-end module, processor and output module. For example, the device may include a first signal line between the sweat sensing electrode 110 and the front end module 120, a second signal line between the front end module 120 and the processor 130 for conveying a signal output from the front-end module 130 to the processor 140. The device may further include a third signal line between the processor 130 and the output module 140 for conveying a signal indicating a fitness level of the user. The signal lines may for instance comprise a metal, such as but not limited to copper, gold etc, or a conductive polymer and may be embedded in a printed circuit board contained in the main body 10 of the device.

The electrode 30, 110 may be exposed on a surface of the recessed portion 20 of the device 1 , 100 and thus vulnerable to damage. Accordingly, the device may further comprise a removable protective lid 70 which is fittable over the recessed portion 30 to protect the electrode. An example of a protective lid 70 for the use with the device of Fig. 1 is shown in Fig. 3. In some examples the removable protective lid 70 may form a snap fit with the recessed portion 20. In other examples, the protective lid may have a rubber or other compressible material, such as rubber, on the underside which compressible material may fit into the recess 20 and push against edges of the recess 20 in order to secure the protective lid in place. In some examples, the protective lid may form a watertight or waterproof seal with the recess, so as to protect the electrode 30 from corrosion or water damage.

The main body 10 of the device may comprise plastic material. For instance the main body 10 may comprise a plastic casing which encloses electronic components such as the front-end module and the processor. As plastic is waterproof, this helps protect the internal components of the device. As shown in Fig. 1, the main body may have a tear drop shape and the recessed portion may have a circular shape. Such a shape is convenient and allows a wider end of the device to accommodate the electrode 30, while having a narrower width at the other end thus reducing the device foot print.

In some examples, the device may include an actuation button 50 for actuating the device to measure characteristics or parameters of sweat deposited in the in the recessed portion and determine a fitness level of the user. For instance, the button may be connected by a signal line to the processor and/or the front-end module and pressing the button 50 may activate the processor and/or front-end module to analyse the sweat and determine a fitness level of the user. In some examples, the actuation button 50 may be located between the recessed portion 30 and the aperture 60.

The main body 10 of the device may include an aperture 60 for facilitating attachment of the device to a key ring, clothing or other object. The aperture 60 may be at a narrower end of the device, as shown in Fig. 1. The device may further comprise an attachment member which removably attaches to the aperture and which may be used to attach the device to another object. For instance the attachment member may be a carabiner. Fig. 5 shows an example of a carabiner 90 which includes a partial ring or U-shaped member 92 with a hinged portion 94. The hinged portion 94 may be biased into a closed position, as shown in Fig. 5, and opened to attach the carabiner to the aperture 60 by slotting the member 92 through the aperture and then closing the hinge portion 94.

Fig. 4 shows a perspective view of the device 1 of Fig. 1 from below. As can be seen from Fig. 4, the aperture 60 extends through the main body from top to bottom. The bottom of the main body may comprise a removable cover 90 which may be secured in place by securing means 92, such as a bolt, screw, other type of fastening component or adhesive etc. This allows easy assembly of the main body and internal electronic parts in the manufacturing process. In some examples, the cover 90 may be removable in order to facilitate repair.

The main body includes charging contacts 80 for receiving electrical power. For instance, the charging contacts may be connected by power lines to a battery inside the main body 10 of the device. The battery may be configured to supply power to the processor, front-end module and output module via one or more power lines. The device charging contacts 80 may in some examples be provided on the bottom of the device as shown in Fig 4. However, this is an example only and in other implementations the charging contacts may provided on another part of the main body.

As shown in Figs. 6 and 7, the device may further comprise a charging dock 210 for charging the device. The charging dock 210 may comprise a receiving portion 220 for receiving the main body of the device 10. The charging dock 230 may include contacts 230 to interface with the charging contacts 80 of the main body. The charging dock 210 may further include a cable 240 for connecting the charging dock 230 to a power source, such as computer, power adaptor or a mains electricity plug etc. In some examples, the cable 240 may be a universal serial bus (USB) cable.

The main body 10 of the device may be mounted onto receiving portion 220 of the charging dock 210 in order to receive electrical power and charge the device as shown in Fig. 7. The charging dock 210 may include one or more magnets (not shown) for aligning the charging contacts 80 of the main body with the charging dock contacts 230.

Figs. 8 and 9 show an example of the device in operation. In Fig. 8, after exercising a user deposits a drop of sweat 300 in the recessed portion 20 of the main body 10 of the device. For example, due to the convenient shape of the device, the user may use it as a ‘spoon’ to scrape some sweat off their skin, or the user may use a finger or other member to transfer a drop of sweat from their skin to the recessed portion of the device. The sweat sensing electrode may comprise a pattern of electrical contacts on the surface of the main body and in some examples the electrode surface area may be surrounded by a spacer, such as a ring. The effective surface area of the electrode pattern may be relatively compact, e.g. between 80mm² to 150mm².

After depositing the sweat in the recessed portion, such that the sweat contacts the electrode, the user may press the button 50 to activate the device as shown in Fig. 9.

Fig. 10 show an example method 400 of using the device according to the present disclosure.

At block 410, the user exercises for a predetermined period of time. The period time and/or intensity of exercise may be specified by the device manufacturer. For instance the exercise may be such that the user is at a specified level of aerobic function. By specifying the period and intensity of exercise it is possible to ensure the user is a specified aerobic zone and extract consistent chemical data from the sweat.

In the example of Fig.10 the user is instructed to exercise for 30 minutes with heart rate at maximum aerobic function (MAF). The “MAF 180 Formula” enables athletes to find the ideal maximum aerobic heart rate in which to base all aerobic training and to quickly define the exact heart rate for user reference. Under the MAF 180 formula, a user is considered to have maximum aerobic function if their heart rate in beats per minute is at or above 180 minus their age in years. Normally, when a user exercises and keeps the heart rate within the aerobic zone for more than 15 mins (minimum), more than 90% of the body energy will be contributed by the aerobic system and therefore sweat from this stage can be considered meaningful. Therefore, in one example exercise with heart rate at maximum aerobic function for 30 minutes is recommended in order to obtain the most accurate results.

At block 420, after finishing exercising at the intensity and duration specified in block 410, the user scoops a drop of sweat into the recessed portion of the device, e.g. as shown in Fig. 8. The sweat thus contacts the sweat sensing electrode 30. In some examples, the user may then push a button to activate the device as shown in Fig. 9.

At block 430, the electrode 30, 110 and front-end module 120 sense an electrical parameter of the sweat. The front-end module 120 may then send a signal representative of this electrical parameter to the processor 130 and the processor may determines a concentration of a sweat analyte, such as NaCI or ions thereof, based on the electrical parameter. In other examples, the front-end module may determine a concentration of a sweat analyte and send a signal representative of the concentration to the processor.

At block 440, in response to receiving the signal from the front-end module, the processor sends a signal to the display to indicate a fitness level of the user based on the sweat analyte concentration. In other examples, instead of or in addition to displaying the fitness level on a display of the device, the processor may cause a wireless module to wirelessly transmit the fitness level for display on an external device. In some examples, the processor may store the fitness level and/or determined sweat analyte concentration in a memory of the device.

The processor may be configured to determine the fitness level of the user by comparing the analyte concentration of the sweat with at least one threshold. For instance the determined analyte concentration in sweat of the user may be compared with thresholds for different levels of fitness stored in a memory of the processor. Such thresholds may be set by the manufacturer and may either be based on a generic average user or may take into account characteristics of the user, such as age, height, weight, gender etc. In one example the processor is configured to place the user in one of three fitness categories: low, medium and high. The processor may be configured to light an LED corresponding to the fitness level. In one example, the processor is configured to light a red LED for low fitness, yellow LED for medium fitness and green LED for high fitness. However, this is just an example and the processor may be configured to determine a different number of fitness levels. Further the LEDs may all have the same colour or different colours to those mentioned above and in still other examples the display may represent the fitness level differently for example by displaying a number or bar of variable length, or other graphical representation etc.

The front-end module 120 of the device may include circuitry to convert analogue signals from the sweat sensing electrode into digital signals and/or to condition analogue signals received from the sweat sensing electrode. For instance, the front-end module may comprise a plurality of electronic components, such as a filters, resistors, capacitors, amplifiers, an analogue to digital converter and/or a waveform generator. The processor may comprise a processor, such as a central processing unit, microprocessor or logic chip, together with one or more supporting components such as resistors, capacitors, a memory etc.

The device of the present disclosure includes at least one sweat sensing electrode. The sweat sensing electrode(s) may be implemented in a variety of different ways. The sweat sensing electrode(s) may comprise one or more bare metal electrodes and/or one or more electrodes with a surface treatment for reacting with a particular sweat electrolyte. The electrode(s) may be positioned on or protrude through a surface of the device so that the electrodes may contact epidermal sweat deposited by the user into the recessed portion of the main body of the device and so that the front-end module may take electrical readings from the electrode(s) which electrical readings are affected by the presence and qualities of the epidermal sweat.

The sweat sensing electrode(s) together with the front-end module may be capable of detecting various electrical parameters of the sweat depending on the type of electrodes used. The sweat sensing electrode(s) together with the front end module may be used to measure an electrical parameter of the sweat, such as an impedance of the sweat, electrical resistance of the sweat, conductivity of the sweat, admittance of the sweat and/or a current passing through the sweat from a first electrode to a second electrode or a potential difference between a first electrode and second electrode.

Figs. 11 A to 11 D below show example arrangements of the sweat sensing electrode(s) and front-end module, but it is to be understood these are examples only and other implementations and variations are possible within the scope of the present disclosure. For instance different arrangements of circuitry for measuring the electrical sweat parameters are possible. Furthermore, amplifiers, signal conditioning components, an analogue to digital converter and/or logical circuitry could be added to the front-end module.

Fig. 11A shows an example of an arrangement 700A for measuring an electrical parameter of epidermal sweat. The arrangement includes a pair of sweat sensing electrodes 712A, 712B and an analogue front end module 720 comprising a signal generator 722. The signal generator 722 is configured to generate an input signal which may be a DC current or an AC current (i.e. an excitation frequency). The input signal may be injected into the first sweat sensing electrode 712A via a conductive line 715A connecting the first sweat sensing electrode 712A with the analogue front end module. The second sweat sensing electrode 712B is connected to the analogue front end by a second conductive line 715B which may detect a signal output from the second sweat sensing electrode. Thus the first electrode 712A acts as a working electrode and the second electrode 712B acts as a counter electrode.

The electrical parameter of the epidermal sweat, such as conductance or admittance etc., may be determined based on the signal output from the second sweat sensing electrode 712B. For instance, a known current may be injected into the epidermal sweat by the first 712A and the analogue front end 720 may measure a voltage drop between the signal injected into the first electrode 712A by the analogue front end module and the signal received from the second electrode 712B by the analogue front end module, and/or a current flowing between the first and second electrodes 712A, 712B. Use of an alternating current (AC) input signal with a high frequency may provide a more accurate measurement, as AC helps to reduce electrode polarization and Faradic and double layer capacitance at the electrodes is less at higher frequencies.

Fig. 11 B shows another example of an arrangement 700B for measuring an admittance of epidermal sweat. The arrangement includes a pair of sweat sensing electrodes 712A, 712B, an analogue front end module 720 including a signal generator 722 and conductive lines 715A, 715B, similar to Fig. 7A, which parts are the same as in Fig. 7A. In addition, the example of Fig. 7B includes a voltmeter 723 for measuring a potential difference between the first sweat sensing electrode 712A and the second sweat sensing electrode 712B. The first sweat sensing electrode 712A may be connected to the voltmeter 123 by a third conductive line 715C and the second sweat sensing electrode 712B may be connected to the voltmeter 123 by a fourth conductive line 715D.

The arrangement of Fig. 11 B is similar to that of Fig. 11 A, but while Fig. 11 A is a two point method, Fig. 11 B is a four point method as a pair of electrodes 712A, 712B is used to inject the current into the sample and meanwhile the same pair of electrodes 712A, 712B is used to measure the resulting voltage drop. In principle, because no current flows through the voltmeter 723, the injected current completely flows through the sample and therefore, the contact resistance between each electrode 712A/712B and the respective conducting line 715C/715D is largely counteracted. Thus, in Fig. 7B, an electrical parameter of the epidermal sweat, such as conductance or admittance etc., may be determined based on the signal output from the second sweat sensing electrode 712B.

Fig. 11 C shows an example of an arrangement 700C for measuring a current and potential difference between two electrodes. The arrangement includes three sweat sensing electrodes 712A, 712B and 712C and an analogue front end module 720 including a signal generator 722 and a voltmeter 723. The first sweat sensing electrode 712A and the second sweat sensing electrode 712B are connected to the signal generator 722 and a ground of the analogue front end 720 in the same way as for the arrangement of Fig. 11 A described above. The voltmeter 723 is arranged to measure a potential difference between the first electrode 712A and the third electrode 712C, which is a reference electrode. The voltmeter may for example be connected to the first electrode 712A by the first conductive line 715A and the third electrode 712C by a third conductive line 715C. An electrical parameter of the epidermal sweat may be determined based on the current signal output from the second electrode 712B, the potential difference between the first electrode 712A and second electrode 712B and/or the potential of the third electrode 712C compared to the first or second electrode.

Fig. 11 C, is a three point solution as the first, second and third electrodes, 712A, 712B, 712C act as working, counter and reference electrodes respectively. Three-electrode setups have the advantage that, due to the reference electrode they are able to measure potential changes of the working electrode independently of any changes that occur at the counter electrode. That is they are able to specifically measure a parameter of the part of the sweat sample between the working and reference electrodes.

Fig. 11 D shows an example of an arrangement for measuring a current and/or potential difference between sweat sensing electrodes. The arrangement includes four sweat sensing electrodes 712A, 712B, 712C, 712D and an analogue front end module 720 including a signal generator 722 and a voltmeter 723. The first sweat sensing electrode 712A and the second sweat sensing electrode 712B are connected to the signal generator 722 and a ground of the analogue front end 720 in the same way as for the arrangement of Fig. 7A described above. The voltmeter 723 is arranged to measure a potential difference between the third electrode 712C and the fourth electrode 712D; the voltmeter 723 may for example be connected to the third electrode 712C by a third conductive line 715C and the fourth electrode 712D by a fourth conductive line 715D. An electrical parameter of the epidermal sweat may be determined based on the current signal output from the second electrode 712B and the potential difference between the third electrode 712C and fourth electrode 712D.

The arrangement of Fig. 11 D is a full four point system with four separate electrodes, in which the first electrode 712A acts as a working electrode, the second electrode 712B acts as the counter electrode, the third electrode 712C acts as the working sense electrode and the fourth electrode 712D acts as the reference electrode. In this arrangement, the electrode-electrolyte interface impedance between the electrodes 712A/B/C/D and their respective connecting lines 715A/B/C/D has no influence on the measurement. Therefore, this setup may make more accurate measures of the electrical parameters of the sweat sample.

As will be appreciated from the above, depending upon the electrical sweat parameter to be measured and design of the system, there may be one sweat sensing electrode, two sweat sensing electrodes or more than two sweat sensing electrodes. In some examples the sweat sensing electrode is a co-planar electrode, i.e. a structure comprising two or more electrodes in the same plane. By way of example, various co-planar electrode structures are shown in Figs. 12A-12F, but the present disclosure is not limited thereto. Figs. 12A-12C have three electrodes, while Figs. 12D and 12E have four electrodes and Fig. 12F has twelve electrodes. In some examples the sweat sensing electrodes may be interdigitated electrodes. An interdigitated electrode is an electrode structure in which at least two co-planar electrodes have interlocking parts, such as inter-laced fingers or interlocking spirals. Figs. 12C and 12D are examples of interdigitated electrodes.

The sweat sensing electrodes may be bare electrodes formed of copper, gold, platinum or another metal or another conductive material such as graphite, or may be electrodes in which the metal or conductive material is coated with a chemical reactant which is to react with the sweat. In some examples each of the electrodes may be formed of the same material, while in other examples each of, or some of, the electrodes may be formed of different materials.

The front end module may output a digital signal to the processing unit, wherein the digital signal includes the electrical parameter of the sweat as measured by the sweat sensing electrode(s) and front end module or a value based on the electrical parameter. The electrical parameter of the sweat may be used to calculate another sweat parameter which is related to the electrical parameter. For example, the inventor has found that electrical admittance of the sweat is correlated with sweat analyte concentration. Therefore the front-end module or the processor may determine a concentration of the sweat analyte based on the measured electrical admittance of the sweat. Fig. 13 is a graph in which the x-axis represents the NaCI concentration of a solution determined based on the measured admittance of the solution and the y-axis represents the actual NaCI concentration of the solution. As can be seen there was a high level of agreement between the calculated concentration and actual concentration and the relationship was linear within the range of concentrations tested, indicating that the NaCI concentration in the sweat can be determined fairly accurately based on measuring the admittance of the sweat.

Fig. 14 is a functional diagram showing an example structure of an assembly 900 according to an example of the present disclosure which is capable of measuring the admittance of sweat. The assembly includes a printed circuit board 910, a plurality of sweat sensing electrodes 920, a waveform generator 930 and processing circuitry 940, all of which are mounted to the flexible printed circuit board. The waveform generator 930 is configured to inject an excitation signal having a frequency to at least one of the sweat sensing electrodes 920. The processing circuitry 940 is configured to measure an admittance of sweat between sweat sensing electrodes based on a response of at least one of the plurality of sweat sensing electrodes to the excitation signal. The excitation frequency may for example be in the range 1mHz -1MHz. The processing circuitry may comprise a processor, such as a microprocessor, which is configured to determine a concentration of an electrolyte in the sweat based on the measured admittance. As discussed above, admittance has a strong relationship to electrolyte concentration and thus is a relatively reliable indicator of electrolyte concentration.

This assembly 900 may be implemented in a fitness monitoring device 1, 100, as shown in Figs. 1 and 2 or the other examples above. For instance the plurality of sweat sensing electrodes 920 may be implemented by the electrode 30, 110 in Figs. 1 and 2 and/or the electrodes shown in Figs. 11A to 11 D and 12A to 12D, the waveform generator 940 may be implemented by the front-end module 120 and/or the corresponding front-end module components shown in Figs. 11 A to 11 D and the processing circuitry 940 may be implemented by the front-end module 120 and/or the processor 130 of Fig. 2. The excitation signal may be conveyed to the at least one sweat sensing electrode over a first signal line connecting the front end module and the at least one sweat sensing electrode. The response of the at least one sweat sensing electrode to the excitation signal may be received by the processing circuitry over said first signal line or another signal line connecting the at least one sweat sensing electrode to the front-end module.

Fig. 15 shows a further example of a device 1000 for monitoring the fitness level of a user according to the present disclosure. The device 1000 comprises a sweat sensing electrode 1010, a front end module 1020, a processor 1030 and a display 1040 which are similar to the corresponding parts described in Fig. 2 and the other examples above. In addition the device 1000 comprises a temperature sensor 1050. The temperature sensor may for example be a thermocouple, resistance thermometer, MEMs device or other device for measuring temperature. In the example of Fig. 15, the temperature sensor is connected to the processor 1030 by a temperature signal line and the processor receives a temperature signal representative of the temperature sensed by the temperature sensor over the temperature signal line.

The processor 1030 is configured to control the output module 1040 to output an indication of the fitness level of the user based on the temperature signal and the electrode signal received by the front-end module. For instance the sweat parameter or fitness level may be adjusted based on the sensed temperature. In one example, the device is calibrated at 25 degrees Celsius and the processor configured to calculate the fitness level from the sweat parameter at 25 degrees Celsius. However, the sweat parameter for a particular person having a given level of fitness may vary with temperature. For example, sweat analyte concentration may increase with temperature. Accordingly, the processor may compensate the determined sweat parameter and/or fitness level to account for differences between the measured temperature and the temperature at which the device was calibrated. In other examples the temperature signal line may connect the temperature sensor to the front-end module and the front-end module may be configured to adjust the sweat parameter to correct for variations in temperature. The device of Fig. 15 may have any of the features of the other examples described above with reference to Figs. 1-14.

The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

For clarity of explanation, in some instances the present technology has been presented as including individual functional blocks including functional blocks comprising devices, device components, steps or routines in a method embodied in software, or combinations of hardware and software.

Although a variety of examples and other information was used to explain aspects within the scope of the appended claims, no limitation of the claims should be implied based on particular features or arrangements in such examples, as one of ordinary skill would be able to use these examples to derive a wide variety of implementations. Further and although some subject matter may have been described in language specific to examples of structural features and/or method steps, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to these described features or acts. For example, such functionality can be distributed differently or performed in components other than those identified herein. Rather, the described features and steps are disclosed as examples of components of systems and methods within the scope of the appended claims.

It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with any features of any other of the examples, or any combination of any other of the examples.

Claims

1. A device for determining a fitness level of a user, the device comprising: a main body including a recessed portion for receiving a user’s sweat, a sweat sensing electrode in the recessed portion for contacting the user’s sweat; a front-end module for processing a signal received from the electrode; a processor for analysing the sweat based on a signal received from the front-end module; an output module for outputting an indication of the fitness level of the user in response to a signal from the processor.

2. The device of claim 1 wherein the output module is a display.

3. The device of claim 2 wherein the display comprises a plurality of LEDs and at least one signal line between the processor and the plurality of LEDs.

4. The device of claim 3 wherein each LED of the plurality of LEDs has a different colour.

5. The device of claim 1 wherein the device includes a button for activating the processor to analyse the sweat and a signal line connecting the button and the processor.

6. The device of any one of the above claims further comprising a charging dock comprising a receiving portion for receiving the main body and charging dock contacts to interface with charging contacts of the main body.

7. The device of claim 6 wherein the charging dock includes one or more magnets for aligning the charging contacts of the main body with the charging dock contacts.

8. The device of any one of the above claims further comprising a removable protective lid which is fittable over the recessed portion to protect the electrode.

9. The device of any one of the above claims wherein the main body comprises plastic material.

10. The device of any one of the above claims wherein the main body includes an aperture and wherein the device further comprises an attachment member which removably attaches to the aperture.

11. The device of claim 10 wherein the attachment member is a carabiner.

12. The device of any one of the above claims wherein the main body has a tear drop shape and the recessed portion has a circular shape.

13. The device of any one of the above claims comprising a first signal line between the sweat sensing electrode and the front end module for conveying a signal representative of on an electrical parameter of the sweat to the front end module, a second signal line between the front end module and the processor for conveying a signal output from the font end module to the processor and a third signal line between the processor and the output module for conveying a signal indicating a fitness level of the user.

14. The device of any one of the above claims wherein the processor is configured to compare an analyte concentration of the sweat with at least one threshold to generate the second signal indicating the fitness level of the user.

15. The device of any one of the above claims wherein the output module is a wireless communication module for sending the indication of the fitness level wirelessly to a remote device.

16. The device of any one of the above claims further comprising a temperature sensor and a temperature signal line connecting the temperature sensor to the front-end module or the processor, wherein the processor is to control the output module to output an indication of the fitness level of the user based on the electrode signal received by the front-end module and a temperature signal received by either the front-end module or the processor.

17. The device of any one of the above claims wherein the front-end module comprises a waveform generator configured to inject an excitation signal having a frequency into the sweat sensing electrode.

18. The device of claim 17 wherein at least one of the processor and the front-end module comprises processing circuitry to measure an admittance of sweat in the recessed portion based on a response of the sweat sensing electrode to the excitation signal.

19. The device of claim 18 wherein at least one of the processor and the front-end module is configured to determine an analyte concentration of the sweat based on the measured admittance of the sweat.