GB2368645A

GB2368645A - Heart rate monitor

Info

Publication number: GB2368645A
Application number: GB0016519A
Authority: GB
Inventors: Richard John Willshire
Original assignee: Healthcare Technology Ltd
Current assignee: Healthcare Technology Ltd
Priority date: 2000-07-05
Filing date: 2000-07-05
Publication date: 2002-05-08
Anticipated expiration: 2020-07-05
Also published as: GB0016519D0; GB2368645B

Abstract

A heart rate monitor comprises a first component 2 for securing in contact with a body of a user 1 and a second component 4 for receiving and processing the electrical signals transmitted by the first component 2. The first component 2 is adapted to sense heart beats of the user and to transmit electrical signals. The second component 4 comprises means for calculating heart rate, means for capturing a desired instantaneous value of heart rate, and means to indicate subsequent departure of monitored heart rate from the instantaneous value. Upper and lower limits relative to this instantaneous value are then determined to provide a target zone for the monitored heart rate.

Description

HEART RATE MONITOR

The present invention relates to apparatus used in the monitoring of heart rate of a living human body.

Such apparatus commonly takes the form of a chest belt containing an electrocardiograph (ecg) signal amplifier and a transmitter. A monitor unit, typically worn on the user's wrist, contains a receiver and a microprocessor which times beat-to-beat intervals and calculates and displays a heart rate in beats per minute. other embodiments are known, such as a single unit which contains two hand contacts and an ecg amplifier and microprocessor, which once again times beat-to-beat intervals and calculates and displays a heart rate.

The purpose of using a heart rate monitor is to allow the user to control the stress level of exercise, by moderating the effort expended in such a way that the heart rate is held constant at a predetermined value, or held within a small range of heart rate values (a socalled"target zone") around this level. The monitor commonly alerts the user to a divergence from the target zone by visible indicators on the monitor's display and/or by an audible warning.

The target zone is established by setting an upper heart rate limit and a lower limit. Typically these limits are

about 10 to 15 beats per minute apart. The actual values of the limits depend on the age of the user, the purpose of the exercise (for example: fat burning, endurance, or speed training), the user's state of fitness, and the present state of well-being of the user. Before an exercise session, therefore, there can be considerable calculation and estimation by the user in order to arrive at the appropriate theoretical values to be set for the upper and lower limits. To follow this procedure, the user must have studied an instruction manual or other text on fitness training. However, it frequently happens that the preset theoretical limit values turn out to demand an uncomfortably high level of activity for the current state of the user, or alternatively the user finds that the demanded level is too low to achieve any real effect on fitness level. The user then stops exercising, and adjusts the upper and lower limits up or down as appropriate to make a better approximation to the desired stress level. This procedure can often require a series of adjustments to arrive at the desired stress level by successive approximations. This can be a long process which disrupts the continuity of exercise.

Another method of adjusting the stress level which is often used by those who exercise just for general fitness and well-being, is to adjust the stress level until they achieve a particular state of mind and body-such as being just able to carry on a conversation with a

neighbouring exerciser. It is very difficult to predict, before the exercise starts, what limit values to set for this target zone.

It is an object of the present invention to overcome the uncertainty in predicting the target zone limits before exercise begins, and also to provide a convenient means of setting a target zone based on the user's actual perceived stress level during exercise.

According to the present invention there is provided a heart rate monitor comprising: a first component for securing in contact with a body of a user and adapted to sense heart beats of the user and to transmit electrical signals corresponding thereto; a second component for receiving and processing the electrical signals transmitted by the first component, the second component comprising means for calculating heart rate, means for capturing a desired instantaneous value of heart rate, and means to indicate subsequent departure of monitored heart rate from the instantaneous value.

The instantaneous value of heart rate may be in a target zone having upper and lower limits relative to the instantaneous value, the means to indicate subsequent departure of the monitored heart rate from the

instantaneous value being arranged to operate when the upper limit or the lower limit is transgressed.

The upper and lower limits may cover a range of about 10 percent of the instantaneous value.

The monitor may include display means for displaying heart rate and/or means for effecting display, on the display means, during use of the heart monitor, of the instantaneous value of heart rate. The means for effecting display on the display means, of the instantaneous value of heart rate may comprise a useroperated control device, such as a key, knob, button or switch, on the second component. Such user-operated control device may be dedicated to its function or may be incorporated in another user-operated control device which additionally serves for setting one or more functions or parameters of the monitor.

The means to indicate subsequent departure of monitored heart rate from the instantaneous value may comprise audible and/or visible means. Such visible means may comprise two illuminated means, such as arrows, both of which may be illuminated when the heart rate is at the instantaneous value, or in the target zone within the upper and lower limits, one of which arrows may be arranged to flash when the heart rate is above the instantaneous value or above the upper limit, and the

other of which is arranged to flash when the heart rate is below the instantaneous value or below the lower limit.

Audible means, when provided, may comprise an electrically operated sounder.

The first component may be arranged to be secured in contact with a chest, hand or ear lobe of the user.

The first component may incorporate, or be associated with, one or more sensing electrodes for contacting the body of the user to sense the heart beats from electrocardiograph signals.

Alternatively the heart beats may be sensed by blood flow detecting means incorporated in, or associated with, the first component. Such blood flow detecting means may comprise optical or ultrasonic means, or means to detect displacement of a blood vessel.

The electrical signals may be transmitted from the first component to the second component by wire or wireless means.

By means of the invention, activation of a special operating control, such as a button, knob, key or switch, on the heart monitor, or an operating sequence on an

operating control which also serves one or more other functions, adopts a current instantaneous heart rate of a user as a captured or selected level for an active target zone. since it is extremely difficult for a user of the monitor to maintain his or her heart rate at a constant level, the target zone set by this procedure is arranged to have the upper limit of the zone a few beats per minute above the heart rate existing at the instant of operation of the operating control. The lower limit of the target zone is similarly set a few beats per minute below the captured or selected instantaneous heart rate.

With a span from the upper limit to the lower limit set typically at about 10 percent of the instantaneous heart rate, a user is provided with sufficient latitude to control heart rate without too frequent activation of the audible and/or visible means.

The advantages provided by this invention over heart monitors of the prior art are: 1. No calculations and little theoretical knowledge are required to set effective target zones. This is particularly attractive to the many users who are not inclined to study instruction manuals.

2. Target zones are set very simply without special setting screens, therefore the monitor becomes simpler to understand and operate.

3. The heart rate monitor can be used for zone training without the complication of setting any user parameters.

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: Figure 1 is a side view of a person exercising by running and wearing a heart rate monitor according to the present invention; Figure 2 is a block diagram of electronic circuitry of a transmitter in the heart rate monitor of Figure 1; Figure 3 is a block diagram of electronic circuitry contained within a receiver in the heart rate monitor of Figure 1; and Figure 4 is a diagrammatic view of a display on the face of the heart rate monitoring receiver of Figure 1.

Referring to Figure 1, a person 1, who is exercising by running, wears a heart rate monitor 2, 4. The heart rate monitor comprises a first component in the form of a transmitter 2 mounted on a chest belt 3 and which picks up electrical activity of the person's heart by means of electrically conducting contacts which are pressed against the chest of the person 1.

The person 1 also wears a second component of the heart rate monitor, in the form of a receiver/monitor 4, on his or her wrist.

Figure 2 illustrates in electronic block form the transmitter 2 which emits a burst of radio waves at each detected heart beat. The electrical signals (electrocardiographic or ecg) from the heart are picked up by two contacts 10, which are disposed horizontally on the chest of the user and spaced apart by about 20 cm.

The signals are amplified by amplifier 11 and then passed through an electronic filter 12 to remove extraneous signal components of too high and too low a frequency, and to pass a so-called R-wave of the user's electrocardiogram. Trigger circuit block 13 delivers a short enabling pulse to the transmitter output stage 14 whenever the filtered signal exceeds a preset threshold amplitude. The radio signal (typically at a very low frequency of 5 kHz) is transmitted from aerial coil 15.

A battery 16 powers the transmitter.

Figure 3 is an electronic block diagram of the receiver/monitor 4 which is housed in a form for mounting on the wrist of the user 1, such as in a wrist watch.

However, other housings can be provided, such as a waistworn module or a module for mounting on the handlebars of a bicycle or the like, in order to suit various exercise regimes. In the case of a self-contained receiver/monitor 4, the radio signals from the transmitter 2 are detected by aerial 22 and amplified by receiver 21. They are fed to a microcontroller 20 which performs the functions of heart rate calculation, heart rate display on a display unit 23, and also services user commands entered via keys M27, S28, A29, L30 and Z31.

Typically, key M27 could be a mode key for switching between main functional modes of the monitor. Key S28 could be a select key to select sub-functions within each mode, and for selecting user parameters for adjustment.

Key A29 could be an adjust key used to adjust the values of parameters selected by the key S28. Key L30 could be a light key used to effect back lighting. Key Z31 is a zone key used to set a target zone at the user's current heart rate, and is the crux of the present invention.

The microcontroller switches on a backlighting panel 24 by energising a backlighting signal generator 25 to illuminate the display when requested by a press of the light key L30. The microcontroller also energises a sounder 26 when the user's heart rate goes outside the

active target zone, or when a preset time of day has been reached. A battery 32 powers the monitor receiver.

Figure 4 shows in detail the display 23 provided on the receiver/monitor 4 of the heart rate monitor. The heart rate is presented in digital format 40 along with a heart symbol 41 which flashes on receipt of every heart beat signal. An"up"arrow 42, when flashing, signifies that the user's heart rate is above the upper limit of the selected active target zone. If the user's heart rate is below the lower limit of the selected target zone, a "down"arrow 44 flashes. If the user's heart rate is within the limits of the selected target zone, the two arrows 42,44 appear together without flashing.

Operation of the heart rate monitor according to the present invention involves the user putting on the monitor, then starting to exercise as usual. When the user detects that he or she has reached an appropriate stress level for his or her needs, he or she presses the zone key Z31. This causes the instantaneous heart rate to be captured and displayed in the digital format 40 and the upper and lower limits appropriate thereto are automatically calculated, to provide the target zone.

The span from the lower to the upper limit is typically arranged to be around 10 percent of the selected instantaneous heart rate.

Further exercise is then carried out at a stress level which does not cause the arrows 42, 44 on the display to flash and which keeps the sounder 26 silent. Any such flashing or sounding indicates that the user's heart rate is outside the upper or lower limit of the target zone.

The sounder 26 may also be arranged to be activated when a pre-set time of day 43 is reached.

Other embodiments of the present invention are possible.

For example the number and nomenclature of the keys in the receiver/monitor 4 is not important. A dedicated zone key Z31 could be omitted. Instead the target zone could be set by applying pressure of extended duration to one of the other keys.

The invention also applies equally to heart monitors that do not employ a wireless communication link between a transmitter 2 and remote receiver/monitor 4, but instead employ a wired link.

The invention also applies to heart monitors which sense heart rate by detection of an ecg signal at a hand of the user, or by detection of blood flow by photoelectric or ultrasonic means or by sensing displacement of a blood vessel. Photoelectric detection is suitably carried out on an ear lobe of the user.

Claims

1. A heart rate monitor comprising : a first component for securing in contact with a body of a user and adapted to sense heart beats of the user and to transmit electrical signals corresponding thereto; a second component for receiving and processing the electrical signals transmitted by the first component, the second component comprising means for calculating heart rate, means for capturing a desired instantaneous value of heart rate, and means to indicate subsequent departure of monitored heart rate from the instantaneous value.

2. A heart rate monitor as claimed in claim 1, wherein the instantaneous value of heart rate is in a target zone having upper and lower limits relative to the instantaneous value.

3. A heart rate monitor as claimed in claim 2, wherein the upper and lower limits cover a range of about 10 percent of the instantaneous value.

4. A heart rate monitor as claimed in claim 2 or 3, wherein the means to indicate subsequent departure of the monitored heart rate from the instantaneous value are

arranged to operate when the upper limit or the lower limit is transgressed.

5. A heart rate monitor as claimed in any preceding claim, wherein the means to indicate subsequent departure of monitored heart rate from the instantaneous value comprises audible means.

6. A heart rate monitor as claimed in claim 5, wherein the audible means comprises an electrically operated sounder.

7. A heart rate monitor as claimed in any preceding claim, wherein the means to indicate subsequent departure of monitored heart rate from the instantaneous value comprises visual means.

8. A heart rate monitor as claimed in claim 7, wherein the visible means comprises two illuminated means, both of which are illuminated when the heart rate is at the instantaneous value, one of which is arranged to flash when the heart rate is above the instantaneous value, and the other of which is arranged to flash when the heart rate is below the instantaneous value.

9. A heart rate monitor as claimed in claim 7, wherein the visible means comprises two illuminated means, both of which are illuminated when the heart rate is in the target

zone within the upper and lower limits, one of which is arranged to flash when the heart rate is above the upper limit, and the other of which is arranged to flash when the heart rate is below the lower limit.

10. A heart rate monitor as claimed in claim 8 or 9, wherein the illuminated means are arrows.

11. A heart rate monitor as claimed in any preceding claim, wherein the monitor includes display means for displaying heart rate.

12. A heart rate monitor as claimed in any preceding claim, wherein the monitor includes means for effecting display, on the display means, during use of the heart monitor, of the instantaneous value of heart rate.

13. A heart rate monitor as claimed in claim 12, wherein the means for effecting display on the display means, of the instantaneous value of heart rate comprises a useroperated control device on the second component.

14. A heart rate monitor as claimed in claim 13, wherein the user-operated control device is selected from a key, knob, button or switch on the second component.

15. A heart rate monitor as claimed in claim 13 or 14, wherein the user-operated control device is dedicated to its function.

16. A heart rate monitor as claimed in claim 13, wherein the user-operated control device is incorporated in another user-operated control device which additionally serves for setting one or more functions or parameters of the monitor.

17. A heart rate monitor as claimed in any preceding claim, wherein the first component is arranged to be secured in contact with a chest, hand or ear lobe of the user.

18. A heart rate monitor as claimed in any preceding claim, wherein the first component incorporates, or is associated with, one or more sensing electrodes for contacting the body of the user to sense the heart beats from electrocardiograph signals.

19. A heart rate monitor as claimed in any preceding claim, wherein heart beats are sensed by blood flow detecting means incorporated in, or associated with, the first component.

20. A heart rate monitor as claimed in claim 19, wherein the blood flow detecting means comprises optical means.

21. A heart rate monitor as claimed in claim 19, wherein the blood flow detecting means comprises ultrasonic means.

22. A heart rate monitor as claimed in claim 19, wherein the blood flow detecting means detect displacement of a blood vessel.

23. A heart rate monitor as claimed in any preceding claim, wherein electrical signals are transmitted from the first component to the second component by wire means.

24. A heart rate monitor as claimed in any preceding claim, wherein electrical signals are transmitted from the first component to the second component by wireless means.

25. A heart rate monitor substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.