GB2390429A

GB2390429A - Wristwatch body fat and heart rate measuring device

Info

Publication number: GB2390429A
Application number: GB0215427A
Authority: GB
Inventors: Callum Macgregor; Ronald David Lessels Mackie
Original assignee: Healthcare Technology Ltd
Current assignee: Healthcare Technology Ltd
Priority date: 2002-07-04
Filing date: 2002-07-04
Publication date: 2004-01-07
Also published as: GB0215427D0

Abstract

A wristwatch device 2 attached to an arm 4 of a user measures body fat and may additionally measure heart rate. The device comprises a casing 12 having two electrodes 22, 24 on a rear face 14 and two electrodes 26, 28 on a front face 16. The rear face electrodes 22, 24 contact the arm 4 of the user and the front electrodes contact the hand 10 of the opposite arm 8. An electric current is passed through the body and the developed voltage measured. Two values of voltage may be measured using different pairs of electrodes for supply and measurement and an average value calculated. Body fat is calculated from voltage measurements and specific parameters of the user (such as age, gender, weight etc...) and displayed. Heart rate (ECG) may also be measured using the same contacts and displayed. Buttons 34 are provided on the casing for input of data and control of the device, and an alarm may also be incorporated. The device can be used as a fitness programme tool to calculate optimal heart rate and raise the alarm when heart rate deviates from within safe limits.

Description

1 - APPARATUS FOR MEASURING BODY FAT AND OPTIONALLY HEART

RATE This invention relates to apparatus for use in measuring 5 body fat, and optionally heart rate, of a living being, particularly a human person.

Body fat measuring apparatus is known in the form of weighing scales provided with electrically conducting 10 metal contacts. Two such contacts are arranged to underlie each bare foot of a user.

Another form of apparatus comprises a portable unit which is arranged to be grasped with both hands of a user, each 15 hand making contact with two electrical contacts provided on the unit.

In both of these known forms of apparatus, measurement of body fat involves passing alternating current through the 20 body of the user and measuring the magnitude and phase of a voltage generated across an impedance represented by the body of the user. A calculation involving these measurements, along with data pertaining to the weight, height, age and gender of the user, provides an estimate 25 of the body fat content of the user. If, however, the current is passed through the body between the hands of

- 2 - the user, the fat content of the lower half of the body of the user is not measured. Similarly, if the current is passed through the body from foot to foot, the fat content of the upper half of the body of the user is not 5 measured. Nevertheless, it has been found that measurements made between the hands or between the feet give an adequate estimate of body fat content for domestic health monitoring purposes.

10 More complex and expensive forms of apparatus for medical use incorporate both forms of contact, namely two contacts for each foot and two contacts for each hand.

By this means, more detailed analysis of distribution of body fat throughout the body of a person can be obtained.

In the measurement of body fat content, the electrical impedance of the flesh of a person is measured at one or more electrical frequencies in the region of a few tens to a few hundred kilohertz. In apparatus involving 20 measurement through the hands of a person, the usual method of operation is with each hand of the person touching two metal plates. One plate on each hand is for entry and exit of the applied alternating current and the other pair of plates is used for measuring the voltage 25 between the hands resulting from the applied current.

The reason for applying what is known as a four terminal

- 3 - method is that the skin resistance between the metal s plates and the underlying flesh of the hands of the person is very high, for example about 100 kilohms, whereas the impedance of the body of the person, from -

5 hand to hand, is much lower, for example from a few tens of ohms to a few hundred ohms. If only one contact plate were to be used on each hand for both current injection and voltage measurement, information would be obtained which would be dominated by the resistance of the skin.

10 By using four contact plates, the contribution from the resistance of the skin is largely eliminated.

The apparatus of the prior art for body fat measurement:

is generally cumbersome and relatively expensive.

15 Furthermore, there is a requirement that body fat data should be supplied during a fitness programme in association with monitored heart rate data and such that an optimum heart rate zone, between lower and upper limits of heart rate, can be readily specified as part of 20 an exercise programme for fat reduction specific to a particular person, and having regard to specific parameters of that person, such as age, gender, weight and height. Separate heart rate monitoring apparatus has hitherto been required.

25 -

- 4 - It is an object of the present invention to overcome or ameliorate the above disadvantages by providing apparatus for measuring body fat which is compact and inexpensive and intended for wearing on an arm of a user in the same 5 way as, or incorporated in, a timepiece such as a wristwatch, and which may also be adapted to measure heart rate.

According to the present invention there is provided 10 apparatus for measuring body fat in a living being having a first arm with a first hand and a second arm with a second hand, the apparatus comprising: a casing having first and second opposed faces and adapted to be secured to the first arm of the living being, with the first face 15 of the casing against the first arm; first and second electrical contact means provided on the first face of the casing and adapted to contact the first arm of the living being) third and fourth electrical contact means provided on the second face of the casing and adapted to 20 be contacted by the second hand of the living being; battery-powered electrical processing circuit means incorporated in the casing and adapted to supply electric current through the living being and to measure resulting voltage developed across the living being, by way of the 25 first, second, third and fourth electrical contact means and to compute body fat data therefrom; and display means

provided on the second face of the casing for displaying the computed body fat data.

The electrical processing circuit means may be adapted 5 and arranged whereby the electric current is supplied firstly by way of the first and third electrical contact means and secondly by way of the second and fourth electrical contact means and the developed voltage is measured firstly between the second and fourth electrical 10 contact means and secondly between the first and third electrical contact means. The two values of the measured developed voltage may be averaged.

The resulting developed voltage which is measured may 15 comprise voltage amplitude and phase.

The electrical processing circuit means may comprise an -

electric current generator, a microcontroller, an amplifier and an analogue-to-digital converter.

The computed body fat data may be displayed as a percentage of body mass of the living being, or may be displayed as a body fat index value having regard to one or more specific parameters of the living being. Such 25 one or more specific parameters may be one or more of age, gender, weight and height of the living being.

The casing may be adapted to be secured to the first arm of the living being by means of a strap or band and may be adapted to be secured to the first arm of the living being at a wrist region thereof, adjacent to the first 5 hand.

The third and fourth electrical contact means may be adapted to be contacted by fingers of the second hand of the living being.

The apparatus may also comprise, or may be incorporated in, a timepiece, such as a watch.

The apparatus may additionally be adapted to monitor and 15 display heart rate of the living being. For such monitoring and display of heart rate, supply of electric current through the living being is arranged to be discontinued, the processing circuit means being adapted and arranged to measure a voltage signal generated by a 20 heart of the living being, between the first or second electrical contact means and the third or fourth electrical contact means, when such third or fourth electrical contact means is contacted by the second hand of the user.

The voltage signal generated by the heart of the living being may be an electrocardiograph (ECG) voltage signal conducted through the first and second arms of the living being. The measured voltage signal generated by the heart of the living being may be amplified, digitised and processed by the processing circuit means, having regard to peaks in the measured voltage signal, to compute the heart rate of 10 the living being.

An optimum heart rate value, or a zone of values between lower and upper limits, may be computed for the living being by the processing circuit means and displayed on 15 the display means. Such optimum heart rate value, or zone of values, may be computed having regard to the computed body fat data and/or one or more specific parameters of the living being, such as one or more of age, gender, weight and height of the living being.

One or more control buttons may be provided on the casing, such as at an edge thereof, for manual operation Such one or more control buttons may be arranged for selecting an operating mode of the apparatus and/or for 25 adjustment of the apparatus and/or for programming of the apparatus and/or for inputting one or more specific

À 8 - parameters of the living being, such as one or more of age, gender, weight and height of the living being.

The display means may be one or more digital displays, 5 which may be of liquid crystal form.

Warning means, such as a visual and/or audible alarm, may be provided in the casing. Such warning means may indicate when the heart rate of the living being is 10 outside of a predetermined optimum heart rate zone and/or may serve as a timepiece alarm.

The living being may comprise a human person.

15 For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: 20 Figure 1 is a front view of an embodiment of apparatus according to the present invention provided on an arm of a person at a wrist thereof; Figure 2 is a rear view of the apparatus of Figure 1; and

- 9 - Figure 3 is a block diagram of electrical processing circuit means incorporated in the apparatus of Figures 1 and 2.

5 Referring to Figures 1 and 2, apparatus 2 is provided for measuring body fat in a living being. The living being comprises a human person having a first arm 4 with a first hand 6, and a second arm 8 with a second hand 10.

The apparatus conveniently comprises, or is incorporated 10 in, a batteryoperated digital timepiece, such as a wristwatch, and comprises a casing 12 having a first (i.e., rear) face 14 and a second (i.e., front) face 16.

The casing 12 is provided with a strap or band 18 by means of which it is secured at a wrist region 20 of the 15 first arm 4 of the person, adjacent the first hand 6, and with the first face 14 of the casing 12 against the first arm 4.

First and second separate electrical contacts 22 and 24 20 are provided on the first face 14 of the casing 12. The first and second electrical contacts 22 and 24 are electrically insulated from one another and are adapted to contact skin of the first arm 4 of the person.

25 Third and fourth separate electrical contacts 26 and 28 are provided on the second face 16 of the casing 12. The

- 10 third and fourth electrical contacts 26 and 28 are electrically insulated from one another and are adapted to be contacted by two fingers 30 of the second hand 10 of the person.

The casing 12 is provided with one or more digital display means 32, such as of liquid crystal form.

One or more control buttons 34 is or are provided on the 10 casing 12, such as at an edge region thereof, and adapted for manual operation to enable a desired mode of operation and/or adjustment of the apparatus to be selected and to enter one or more specific parameters.

15 As will be described in detail hereinafter, a battery-

operated electrical processing circuit means, as shown diagrammatically in Figure 3, is provided inside the casing 12.

20 The apparatus 2 is arranged to fulfil the usual time-

keeping functions of a wristwatch and to provide displays such as of time of day and calendar, and may include options such as time of day alarm, hourly alarm, and stop-watch function with or without lap memory. Such 25 time-keeping functions and their implementation are well

known to the skilled person and do not form an essential part of the present invention.

The apparatus 2 of the present invention operates to 5 measure body fat content of a person using it as follows.

An electric current generator 36 is arranged to pass electric current through the body of the user between the first and second electrical contacts 22, 24, on the first face 14 of the casing 12, and the third and fourth 10 electrical contacts 26, 28 on the second face 16 of the casing 12. The route for passage of the current is selectable by means of electronically controlled switches 38 and 40. The voltage developed across the body of the user of the apparatus 2, as a result of passage of the 15 current, is amplified by an amplifier 42, whose output is measured by an analogue-to-digital converter 44. The measured output value is passed to a microcontroller 46 which calculates body fat content therefrom for indication on the display 32.

In operation of the apparatus 2, the user presses an appropriate control button 34, which selects and enters a mode of operation of the apparatus 2 for body fat measurement. The display 32 offers the user a choice of 25 selecting certain parameters of an existing user, or of entering parameters of a new user. This choice is made

- 12 -

by pressing a button 34 dedicated to selection of options If a new user is selected, the display 32 provides a prompt for the user's weight, height, age and gender to be entered. Each of these parameters is set by 5 pressing the appropriate button 34 in a similar fashion to setting the time in a digital watch. When this has been completed, the user is given an option of saving the entered values under a new user number, for more convenient future use.

The user then places two fingers 30 of his or her second hand 10 on the third and fourth electrical contacts 26 and 28 on the second face 16 of the casing 12. The microcontroller 46 directs the switches 38 to provide a 15 current route from the current generator 36 through the body of the user by way of the electrical contacts 22 and 26. At the same time, the microcontroller 46 directs the switches 40 such that a resulting first voltage, developed across the body of the user, is able to be 20 measured between the electrical contacts 24 and 28. The microcontroller 46 then switches on the current generator 36, the generated current being an alternating current of substantially constant fixed amplitude, having a frequency of about 100 kHz and an amplitude of somewhat 25 less than 1 mA. The microcontroller 46 directs the analogue-to-digital converter 44 to take many samples of

- 13 -

the resulting developed first voltage. These samples are processed by the microcontroller 46 to extract and save the amplitude and phase of the first alternating voltage.

5 The level of current from the current generator 36 is arranged to be within safe limits for conduction through the body of the user, although the apparatus 2 would generally be unsafe for use by a person having a medical implant such as a heart pacemaker, or by a person 10 attached to electronic life support equipment.

The microcontroller 46 then switches off the current generator 36 and directs the switches 38 to provide a current route through the body of the user from the 15 electrical contact 24 to the electrical contact 28. At the same time, the switches 40 are directed such that a resulting second voltage developed across the body of the user is able to be measured between the electrical contacts 22 and 26. The current generator 36 is then 20 switched on and the microcontroller 46 directs the analogueto-digital converter 44 to take many samples of the developed second voltage. These samples are processed by the microcontroller 46 to extract and save the amplitude and phase of the second alternating 25 voltage.

- 14 -

The first and second derived alternating voltage results are then averaged to eliminate any asymmetry in electrical contact made to the flesh of the user by the four electrical contacts 22, 24, 26, 28.

The microcontroller 46 then calculates the body fat content of the person, using the measured and averaged voltage amplitude and phase values in conjunction with the entered data relating to the person's weight, height, 10 age and gender. The body fat content is then displayed on the display 32 as a percentage of total body mass and as an actual mass of fat. The calculation makes use of empirical results obtained from extensive trials undertaken during development of the apparatus 2.

Body fat scales in common use generally quote body fat content as a percentage of body mass. This then has to be interpreted by a user with reference to tables of values for men and women, which quote values for thin, 20 normal and obese body forms. In order to simplify interpretation of the result of the body fat measurement, the apparatus 2 of the present invention, in addition to displaying a percentage body fat value, also displays a body fat index value. Such body fat index value is a 25 number ranging from -99 to +99, where 0 is normal for a user of a specific age, gender, weight and height.

- 15 Negative index values represent users who are thinner than normal and positive index values represent users who are fatter than normal. This feature gives a user a simple aiming point (for example, trying to lower a 5 positive index value to reach zero), and is also a convenient means for measuring progress in fat reduction.

The apparatus 2 of the present invention may additionally be employed as a heart rate monitor. An appropriate 10 control button 34 is operated to select a heart rate monitoring mode. The user then places a finger 30 of his or her second hand 10 on the electrical contact 28 on the second face 16 of the casing 12 of the apparatus 2. In this mode, the microcontroller 46 does not switch on the 15 current generator 36, but sets the switches 40 to route a voltage signal, developed in the body of the user between the electrical contacts 24 and 28, to the amplifier 42.

This voltage signal is an electrocardiograph (EGG) signal from the heart of the user, which is conducted down the 20 arms 4, 8 of the user. This signal has a peak, known as the it-wave, of about 1 mV in this part of the body of the user. After amplification, the signal is digitised by the analogue-to-digital converter 44 and samples thereof are processed by the microcontroller 46 to detect times 25 of arrival of the it-waves. By measuring intervals between the it-waves, the heart rate of the user is

- 16 -

calculated by simple arithmetic, by the microcontroller 46, and displayed in beats per minute on the display 32.

A further heart rate monitoring function can be 5 incorporated in the apparatus 2 to assist a user in exercising within a zone of heart rate values. In order to achieve a specific fitness target, such as reducing weight or anaerobic exercise, it is recommended to exercise with the heart rate maintained in a zone within 10 a small range of values. The heart rate values for a particular zone depend upon the user's age, gender and state of fitness and can be entered into the apparatus 2 using appropriate control buttons 34 dedicated to selection and adjustment. In operation, the apparatus 15 can be arranged to flash a warning message or symbol on the display 32. In addition, an audible warning signal, such as bleeps, may be provided by a sounder 48 incorporated in the casing 12, when the heart rate of the user lies outside the pre-set zone. The sounder 48 may 20 also serve to provide an alarm for the apparatus 2 when operated in a time-keeping mode as a wristwatch.

When the apparatus 2 has been operated to provide a value of the body fat content of a user, this value, in 25 conjunction with previously entered parameters of age, gender, weight and height of the user, can be used to

- 17 -

calculate an optimum heart rate zone (between a lower and a higher heart rate) specific to the user, for a fat-

reduction exercise programme.

5 The apparatus 2 of the present invention is advantageous in that, by incorporating it with a wrist watch which performs the usual time-keeping functions, economical manufacture results. Furthermore, measurement of body fat can conveniently be carried out by a user at any time 10 without having to find and set up a special-purpose device. By adding the heart rate monitoring function to the apparatus, a user can be guided to exercise within a 15 range of heart rate values, which are optimised for fat reduction. In particular, once a user's body fat content has been measured, this value can be incorporated in the calculation of a heart rate zone which is tailored to be optimised for fat reduction for that specific user.

Claims

- 18 CLAIMS

1. An apparatus for measuring body fat in a living being having a first arm with a first hand and a second 5 arm with a second hand, the apparatus comprising: a casing having first and second opposed faces and adapted to be secured to the first arm of the living being, with the first face of the casing against the first arm; first and second electrical contact means provided on the first 10 face of the casing and adapted to contact the first arm A.. of the living being; third and fourth electrical contact À *. means provided on the second face of the casing and Àe adapted to be contacted by the second hand of the living À À Àe - A. being; battery-powered electrical processing circuit . 15 means incorporated in the casing and adapted to supply À. À. -- À electric current through the living being and to measure . À resulting voltage developed across the living being, by way of the first, second, third and fourth electrical contact means and to compute body fat data therefrom; and 20 display means provided on the second face of the casing for displaying the computed body fat data.

2. An apparatus as claimed in claim 1, wherein the electrical processing circuit means is adapted and 25 arranged whereby the electric current is supplied firstly by way of the first and third electrical contact means

- 19 -

and secondly by way of the second and fourth electrical contact means and the developed voltage is measured firstly between the second and fourth electrical contact means and secondly between the first and third electrical 5 contact means.

3. An apparatus as claimed in claim 2, wherein the two values of the measured developed voltage are averaged.

10 4. An apparatus as claimed in claim 1, 2 or 3, wherein . the resulting developed voltage which is measured À . comprises voltage amplitude and phase.

À Àe À À Àe 5. An apparatus as claimed in any preceding claim, . 15 wherein the electrical processing circuit means comprises À. À. an electric current generator, a microcontroller, an À amplifier and an analogue-to-digital converter.

6. An apparatus as claimed in any preceding claim, 20 wherein the computed body fat data is displayed as a percentage of body mass of the living being having regard to one or more specific parameters of the living being.

7. An apparatus as claimed in any preceding claim, 25 wherein the computed body fat data is displayed as a body

- 20 fat index value having regard to one or more specific parameters of the living being.

8. An apparatus as claimed in claim 6 or 7, wherein the 5 one or more specific parameters comprise one or more of age, gender, weight and height of the living being.

9. An apparatus as claimed in any preceding claim, wherein the casing is adapted to be secured to the first 10 arm of the living being by means of a strap or band.

*e À. À. À . 10. An apparatus as claimed in claim 9, wherein the casing is adapted to be secured to the first arm of the À. A. living being at a wrist region thereof, adjacent to the . 15 first hand.

À. À.e À.....

À 11. An apparatus as claimed in any preceding claim, wherein the third and fourth electrical contact means are adapted to be contacted by fingers of the second hand of 20 the living being.

12. An apparatus as claimed in any preceding claim, wherein the apparatus also comprises, or is incorporated in, a timepiece.

13. An apparatus as claimed in claim 12, wherein the timepiece is a watch.

14. An apparatus as claimed in any preceding claim, 5 wherein the apparatus is additionally adapted to monitor and display heart rate of the living being.

15. An apparatus as claimed in claim 14, wherein the supply of electric current through the living being is 10 arranged to be discontinued, the processing circuit means A.. being adapted and arranged to measure a voltage signal À . generated by a heart of the living being, between the first or second electrical contact means and the third or À À- fourth electrical contact means, when such third or . 15 fourth electrical contact means is contacted by the .. Àe. second hand of the user.

À 16. An apparatus as claimed in claim 15, wherein the voltage signal generated by the heart of the living being 20 is an electrocardiograph (ECG) voltage signal conducted through the first and second arms of the living being.

17. An apparatus as claimed in claim 15 or 16, wherein the measured voltage signal generated by the heart of the 25 living being is amplified, digitised and processed by the processing circuit means, having regard to peaks in the

- 22 measured voltage signal, to compute the heart rate of the living being.

18. An apparatus as claimed in any one of claims 14 to 5 17, wherein an optimum heart rate value, or a zone of values between lower and upper limits, is computed for the living being by the processing circuit means and displayed on the display means.

10 19. An apparatus as claimed in claim 18, wherein the . optimum heart rate value, or zone of values, is computed . having regard to the computed body fat data of the living being. .. À-:e À:. . 15 20. An apparatus as claimed in claim 18 or 19, wherein . A. the optimum heart rate value, or zone of values, is À computed having regard to one or more specific parameters of the living being.

20 21. An apparatus as claimed in claim 20, wherein the one or more specific parameters comprise one or more of age, gender, weight and height of the living being.

22. An apparatus as claimed in any preceding claim, 25 wherein one or more control buttons are provided on the casing for manual operation.

- 23 23. An apparatus as claimed in claim 22, wherein the one or more control buttons are provided at an edge of the casing. 5 24. An apparatus as claimed in claim 22 or 23, wherein the one or more control buttons are arranged for selecting an operating mode of the apparatus.

25. An apparatus as claimed in claim 22, 23 or 24, 10 wherein the one or more control buttons are arranged for A.. adjustment of the apparatus.

en.. a.-- ,. 26. An apparatus as claimed in any one of claims 22 to Àe- . 25, wherein the one or more control buttons are arranged , 15 for programming of the apparatus.

À. À 27. An apparatus as claimed in any one of claims 22 to 26, wherein the one or more control buttons are arranged for inputting one or more specific parameters of the 20 living being.

28. An apparatus as claimed in claim 27, wherein the one or more specific parameters comprise one or more of age, gender, weight and height of the living being.

À 24 29. An apparatus as claimed in any preceding claim, wherein the display means is one or more digital displays. 5 30. An apparatus as claimed in claim 29, wherein the one or more digital displays are of liquid crystal form.

31. An apparatus as claimed in any preceding claim, wherein warning means is provided in the casing.

. 32. An apparatus as claimed in claim 31, wherein the e . warning means is a visual alarm.

- À À À. À. 33. An apparatus as claimed in claim 31 or 32, wherein , 15 the warning means is an audible alarm.

À. À.- a..... À 34. An apparatus as claimed in any one of claims 31 to 33, wherein the warning means indicates when the heart rate of the living being is outside of a predetermined 20 optimum heart rate zone.

35. An apparatus as claimed in any one of claims 31 to 34, wherein the warning means is a timepiece alarm.

25 36. An apparatus as claimed in any preceding claim, wherein the living being comprises a human person.

- 25 37. An apparatus for measuring body fat in a living being substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

À. ee À À À À e À À Àe.e À À. À.. - À