U.S. patent application number 10/429891 was filed with the patent office on 2003-10-16 for electrical neuromuscular stimulator for measuring muscle responses to electrical stimulation pulses.
This patent application is currently assigned to COMPEX MEDICAL S.A.. Invention is credited to Buhlmann, Felix, Muller, Pierre-Yves, Rigaux, Pierre.
Application Number | 20030195587 10/429891 |
Document ID | / |
Family ID | 23710364 |
Filed Date | 2003-10-16 |
United States Patent
Application |
20030195587 |
Kind Code |
A1 |
Rigaux, Pierre ; et
al. |
October 16, 2003 |
Electrical neuromuscular stimulator for measuring muscle responses
to electrical stimulation pulses
Abstract
The electrical stimulator includes an electrical pulse generator
arranged in a case, stimulation electrodes (7) to be placed on a
user's skin on the motor points of the muscles to be stimulated,
each electrode (7) being connected to an electric cable (5)
connector, the other end of the cable being connected in a
removable manner to a signal input and/or output socket of the case
for receiving the electric pulses, at least one sensor (11) for
measuring the muscle reactions caused by the electric pulses, and
electronic means in the case for receiving the measurements from
the sensor. The sensor (11) is intrinsically linked to one of the
electrodes (7) or to the connector (6). At least one conductor wire
(15) of the cable connects the electrode (7) independently of the
sensor (11). The stimulator finds application in particular in the
field of sports for the passive exercising of muscles stimulated by
electric pulses, or in the re-education of atrophied muscles. In
this case, the sensor (11) is used to provide data as to the
reactivity of the stimulated muscles and their fatigue level. This
data is seen on a display of the stimulator and is used to adjust
the stimulation parameters manually or automatically.
Inventors: |
Rigaux, Pierre; (Liege,
BE) ; Buhlmann, Felix; (Lausanne, CH) ;
Muller, Pierre-Yves; (Hermance, CH) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS, PLLC
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037-3202
US
|
Assignee: |
COMPEX MEDICAL S.A.
|
Family ID: |
23710364 |
Appl. No.: |
10/429891 |
Filed: |
May 6, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10429891 |
May 6, 2003 |
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09940611 |
Aug 29, 2001 |
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09940611 |
Aug 29, 2001 |
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09431080 |
Nov 1, 1999 |
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6324432 |
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Current U.S.
Class: |
607/48 |
Current CPC
Class: |
A61N 1/0456 20130101;
A61N 1/048 20130101; A61N 1/36003 20130101; A61N 1/0492 20130101;
A61N 1/0452 20130101; A61N 1/36014 20130101 |
Class at
Publication: |
607/48 |
International
Class: |
A61N 001/18 |
Claims
What is claimed is:
1. An electrical neuromuscular stimulator for measuring muscle
reactions generated by electrical stimulation pulses, including an
electrical pulse generator arranged in a case of the stimulator, at
least one pair of stimulation electrodes intended to be placed on
an user's skin on the motor points of the muscles to be stimulated,
each electrode being connected to one end of an electric cable, the
other end of which is connected to the case to receive the electric
pulses from the generator, at least one sensor sensitive to the
muscle reactions caused by the electric stimulation signals and
arranged for transmitting electric measuring signals representative
of said muscle reactions to electronic means in the stimulator
case, wherein the sensor is mechanically connected to one of the
electrodes or to the end of one of the cables on the electrode
side, and wherein at least one conductor wire per electric cable
connects the respective electrode independently of the sensor.
2. A stimulator according to claim 1, wherein each end of the
electric cables on the electrode side is securely fixed to the
respective electrode structure.
3. A stimulator according to claim 1, wherein each cable end on the
electrode side has a connector connected to the respective
electrode structure by removable fixing means.
4. A stimulator according to claim 3, wherein the removable fixing
means are of the snap fastening type also acting as electric
contact between the connector and at least one active conducting
surface of the respective electrode.
5. A stimulator according to claim 3, wherein the removable fixing
means, acting also as electric contact between the connector and at
least two active surfaces of the electrode, include at least two
conductive studs inserted with a certain mechanical resistance in
two conductive pots, the studs forming part of the electrode
structure and the pots forming part of the connector, or vice
versa.
6. A stimulator according to claim 1, wherein the measuring sensor
is an electromyographical sensor having at least one active
conductive surface placed without electric contact beside at least
one other active conductive surface of the electrode receiving the
electric pulses, said active surfaces being placed on the motor
points of the muscles to be stimulated.
7. A stimulator according to claim 1, wherein the sensor is an
acceleration meter or a microphone integrated in the connector of
the end of the cable on the electrode side or in the structure of
one of the respective electrodes.
8. A stimulator according to one of claims 6 and 7, wherein the
means for processing the signals received from the sensor are
integrated in the connector or in the electrode structure.
9. A stimulator according to claim 1, wherein the sensor is in
communication with the electronic means of the stimulator via
wireless signal transmitting and/or receiving means housed in the
cable connector or in the electrode structure, or via at least one
conductor wire of the cable other than that of the electrode.
10. A stimulator according to claim 9, wherein an electric power
source is housed in the connector or in the electrode structure for
supplying power to the electronic components for measuring muscle
reactions.
11. A stimulator according to claim 1, wherein it includes, on the
case, a visual display device capable of displaying in particular
electric stimulation programmes and data relating to the electric
muscle reaction measuring signals.
12. An electric cable for a stimulator according to claim 1,
wherein one end of the cable on the electrode side has a connector
for connection to the structure of a stimulation electrode via
removable fixing means also acting as electric contact for the
active surface or surfaces of the electrode, wherein the connector
includes at least a part of a sensor sensitive to muscle reactions,
and wherein it includes in an insulating sheath at least one
conductor wire for connecting the active surface or surfaces of the
stimulation electrode independently of the sensor.
13. An electric cable according to claim 12, wherein the connector
encloses processing means for the signals supplied by the
sensor.
14. An electric cable according to claim 12, wherein the means for
fixing to the electrode are of the snap fastening type or of the
multicontact type.
15. An electric cable according to claim 12, wherein the connector
includes wireless signal transmitting and/or receiving means, and
an electric power source for the electronic components for
measuring the muscle reactions.
16. A stimulation electrode for a stimulator according to claim 1,
wherein it includes at least one active conductive surface for
receiving the electric pulses, and wherein the active surface is
electrically connected to removable means for fixing to a cable
connector.
17. A stimulation electrode according to claim 16, wherein it
includes an electromyographical sensor having at least one other
active conductive surface arranged without electric contact beside
the active surface receiving the electric pulses, or an
acceleration meter or a microphone placed on the electrode
structure.
18. A stimulation electrode according to claim 16, wherein its
structure is flexible so as to be able to match the shape onto
which it is placed, and wherein a portion of its structure,
surrounding the active surface or surfaces in the form of a metal
wire, is coated or covered with a self-adhesive material or film so
as to be able to stay on the skin without using additional holding
elements.
Description
[0001] The invention concerns an electrical neuromuscular
stimulator for measuring muscle reactions generated by electrical
stimulation pulses. The stimulator includes an electrical pulse
generator arranged in a case, at least one pair of stimulation
electrodes intended to be placed on the skin of an user in the
vicinity of the motor points of the muscles to be stimulated, each
electrode being connected to one end of an electric cable, the
other end of which is connected to the case to receive the electric
pulses from the generator, at least one sensor sensitive to the
muscle reactions caused by the electric stimulation pulses and
arranged for transmitting electric measuring signals representative
of said muscle reactions to electronic means in the stimulator
case.
[0002] The invention also concerns an electric cable and a
stimulation electrode for a neuromuscular electric stimulator.
[0003] The sensor supplies data regarding the useful muscle
reactions in particular in order to know the fatigue level of the
electrically stimulated muscles. The measurements obtained from the
sensor allow the parameters of the electric stimulation pulses to
be adjusted either manually by viewing the shape of the signals
received by the sensor on a display or automatically by adjusting
the electric stimulation parameters as a function of the muscle
fatigue. Adjusting the parameters consists in correcting either the
frequency of the pulses, or the amplitude or duration of the
voltage or current pulses, or the duration of muscle contraction
and relaxation, or the number of contraction/relaxation cycles, or
any combination of the preceding parameters.
[0004] The object of electric stimulation or electrostimulation is
to control working of the muscles by the intermediary of electric
voltage or current pulses as a function of programmed parameters.
Each voltage or current pulse provides excitation of the nerve
fibres which control the muscle fibres via the motor end-plate This
excitation causes an elementary mechanical muscle response called a
twitch with a duration of the order of 0.1 seconds.
[0005] The voltage or current pulse is repeated over time at an
adjustable frequency. If this frequency is low, for example 10 Hz,
the working power of the muscles is slight, whereas for a high
frequency, for example 100 Hz, the working power of the stimulated
muscle fibres is very high. This very high power corresponds to a
powerful tetanic contraction. The muscle fibre twitches can no
longer be separated after each pulse at this high frequency, which
means that a temporal summation of the twitches occurs which leads
to a tetanic contraction.
[0006] If the stimulated muscles are stimulated at a high
frequency, they will tend to become tired. In this case, the
exercising session consists in alternating contraction periods and
rest periods. The rest phase allows the fibres to relax and recover
prior to the next contraction phase.
[0007] In the medical field, electric stimulators are used to
assist handicapped persons or accident victims so as to overcome
deficiencies in muscular activity or to allow them to rehabilitate
withered musculature. Electric current or voltage pulses are
transmitted to said muscles via the electrodes placed on the skin
or subcutaneously in order to make them work passively.
Measurements of the muscle reaction caused by the electrically
evoked twitch allows the electric pulses to be transmitted to the
electrodes to be adjusted as a function of the level of the
electrical or mechanical amplitude measured on the innervated
muscles without thereby excessively tiring the muscles stimulated.
This adjustment of the electrical parameters of the stimulator is
used in particular for handicapped persons or accident victims, to
prevent them being continually obliged to ask for external help
when they have to move one or other of their deficient limbs.
[0008] A stimulator of this type is shown in U.S. Pat. No.
5,070,873 which discloses a control loop for the electric pulses to
be supplied to the muscles to give them sufficient motricity. In a
first phase, electromyographic sensors detect the voluntary muscle
activity which in the case of a handicapped person is lacking. The
voltage measurement obtained by the sensors represents the low
contraction state of the activated muscles which leads to adjusting
the electric pulses from the pulse generator to send voltage pulses
adjusted to the expected reaction to the muscle motor nerves, in
particular to allow automatism in the coordination of movements
desired by the handicapped person.
[0009] The electromyographic sensors can be separated from the
stimulation electrodes, but may also be combined therewith. In the
latter case, a third electrode is necessary. If the same active
surface of the electrode is used both as stimulation electrode and
sensor, this involves controlling, with difficulty, the signals
originating from the sensor following the electric pulses sent
across the electrode.
[0010] The combination of the sensor with the electrode requires
rectangular biphasic voltage pulses to be sent to perform the
measurements by the sensor. It is to be noted that in this case,
for voltage pulses, the stimulation current provided depends on the
impedance of the electrode and the skin. This impedance is not the
same from one person to another, or can vary rapidly over time in
the same person, which leads to different muscle reactions for
identical voltage pulses sent to the electrodes.
[0011] The use of a current pulse generator allows one to be rid of
the drawbacks of a voltage pulse generator, since the pulse is kept
constant whatever the impedance of the skin and the electrode, and
thus allows the same number of fibres recruited for stimulation to
be maintained.
[0012] One drawback of this combination of active surfaces of the
sensor and the electrode lies in the fact that after the sequence
of sent biphasic voltage pulses, there remains a residual voltage
which can have a value of ten volts, whereas the measurement
voltage drawn from the muscles by the sensor is of the order of a
few millivolts. It is thus necessary to attenuate this residual
voltage in order to be able to make an accurate measurement in
particularly of the fatigue level of the stimulated muscles. This
is why sensors separated from the electrodes provide better results
than those combined as described hereinbefore.
[0013] French Patent No. FR 2 425 865 also discloses a
bioelectrically controlled electric muscle stimulator. A carrier
frequency generator provides an electric signal to the muscles to
be stimulated which is adjusted as a function of the bioelectrical
activity of the innervated muscles. With this adjustment of the
electric pulses as a function of the measured muscle reaction, this
stimulator offers a wide range of uses. It allows, in particular, a
certain motor automatism of movements for example during sports
exercising or for assisting handicapped persons.
[0014] The measurement sensors are of the electromyographical type
and can also be combined with the stimulation electrodes, but in
this case, since the voltage pulses sent to the muscles are mainly
voltages of the sinusoidal order, drawing the EMG signals
originating from the same stimulation electrodes using filters does
not pose too much of a problem, which is not the case with
rectangular voltage pulses.
[0015] The muscular contraction measurement means for providing
data as to the state of reaction of the stimulated muscles can be
performed in many ways. The measurement can be either electrical
using electromyographical sensors, or mechanical followed by an
electrical conversion for example using acoustic sensors
(microphones). Such an arrangement is shown in U.S. Pat. No.
4,805,636 in which the vibrations of the contracting muscles are
measured.
[0016] In this Patent document, two microphones are placed at
different locations where the innervated muscles respond
mechanically by a twitch to the voltage pulse generated by an
electric pulse generator. A feedback circuit takes account of the
voltage signals given by the two microphones in order to adjust the
twitch or the electric pulses which the generator generates for the
muscles.
[0017] Strain gauges like any other type of electric conversion
mechanical sensor can be used as described in U.S. Pat. No.
5,507,788. The strain gauges are used to measure a torque developed
by the stimulated muscles. They are arranged at a distance from the
stimulation electrodes. The signals thereby obtained from the
gauges are processed by a set of circuits in the stimulator in
order to adjust the stimulation parameters of the pulse generator
as a function in particular of the muscle fatigue.
[0018] The use of strain gauges can only be applied in the case
where it is possible to be able to measure a torque. A sensor of
this type is not, however, appropriate if measurements are made for
dorsal or pectoral muscles for example, which do not involve
movement of a segment.
[0019] One object of the invention is to use a structure combining
a stimulation electrode with a sensor for measuring muscle
reactions which overcomes the drawbacks of the stimulators
described hereinbefore.
[0020] Another object of the invention consists in allowing an user
to think only of placing the electrodes on the muscles as for a
standard electric stimulator while in addition providing, via the
sensors combined with the respective electrodes, measurements of
the muscle reactions at the locations stimulated.
[0021] The objects of the invention are achieved as a result of the
stimulator indicated hereinbefore which is characterised in that
the sensor is mechanically connected to one of the electrodes or to
the end of one of the cables on the electrode side, and in that at
least one conductor wire per electric cable connects the respective
electrode independently of the sensor.
[0022] The objects of the invention are also achieved as a result
of the electric cable for a stimulator which is characterised in
that one end of the cable on the electrode side has a connector for
being connected to the structure of a stimulation electrode via
removable securing means also acting as an electric contact for the
active surface or surfaces of the electrode, in that the connector
includes at least one portion of a muscle reaction measurement
sensor, and in that it includes in an insulating sheath at least
one conductor wire for connecting the active surface or surfaces of
the stimulation electrode independently of the sensor.
[0023] The objects of the invention are also achieved as a result
of the stimulation electrode for a stimulator which is
characterised in that it comprises at least one conductive active
surface for receiving the electric pulses and in that the active
surface is electrically connected to removable securing means to a
cable connector.
[0024] One advantage of the stimulator with the electrode and
measuring sensor combination consists in facilitating the placing
of said elements for example for the passive training of a
sportsman using such a stimulator or for all other applications.
The sportsman knows where to place the electrodes on the motor
points of the muscles which he wishes to exercise. When first using
such a stimulator, he has had to learn to situate the motor points
for the muscles to be exercised. Through habit, he easily knows how
placing them at the desired locations and thus beginning the
exercising session.
[0025] The supplementary addition of a sensor with the electrode
which he positions will not pose any additional problem. In
addition to stimulation, he will be able to take account of the
fatigue of the stimulated muscles for example on a display of the
stimulator.
[0026] Likewise, if the stimulator includes means for receiving
signals from the sensor able to act on the pulse generator, the
electric voltage or current pulses sent to the stimulation
electrodes are automatically adjusted as a function of the muscle
fatigue thereby avoiding any subsequent handling by the user. The
measurement signals transmitted from the sensor to the stimulation
reception means either pass via a different conductor wire to the
electrode conductor wire, insulated in the electric cable sheath,
or using signal transmitting means without any connecting wire.
[0027] One advantage of using a sensor of the electromyographical
type or with mechanical-electrical conversion of the accelerometric
or acoustic type lies in the fact that they can be used for any
muscle in the body. Dorsal muscles are one of the examples of
muscles in which the reaction measurement is not possible using a
strain gauge sensor or more generally using a torque or force
sensor.
[0028] Another advantage in the use of an electromyographical
sensor with an electrode consists in having two active surfaces,
one for the sensor and the other for the electrode. Consequently,
the muscle responses are measured while minimising the disturbances
originating from the active surface of the stimulation
electrode.
[0029] Another advantage of the stimulator according to the
invention consists in minimising the number of electrodes combined
with the measuring sensors necessary on the one hand for
stimulating the muscles and on the other hand for measuring the
muscle reactions. One pair of electrodes combined with at least one
sensor is sufficient to stimulate the muscles at the desired
locations and to provide data as to the reactions of the stimulated
muscles. The conductor wires connecting the sensor and the
respective electrode are regrouped in a single electric cable. The
manufacturing costs are thus reduced to a minimum.
[0030] The objects, advantages and features of the stimulator will
appear more clearly, in a non limiting manner, in the following
description of the different embodiments illustrated by the
drawings, in which:
[0031] FIGS. 1a and 1b show the stimulator before and after the
connection of the electric cables to the electrodes placed on a
user's skin,
[0032] FIG. 2 shows a partial cross-section of a first embodiment
of an electric cable connector with an integrated measuring sensor
fixed onto a stimulation electrode,
[0033] FIGS. 3a and 3b show a partial vertical cross-section and a
bottom view of a second embodiment of an arrangement of an
electromyographical sensor and electrode,
[0034] FIG. 4 shows a partial cross-section of a third embodiment
of an electric cable connector with an integrated measuring sensor
fixed to a stimulation electrode, and
[0035] FIG. 5 shows diagrams of the electric signals sent to the
electrodes and the muscle response.
[0036] The stimulator described hereinafter relates preferably to a
stimulator used within the field of sport and re-education in which
muscle stimulation is used to exercise them passively. Rectangular
current pulses are supplied to electrodes 7 placed on the skin at
the motor points of the muscles to be stimulated. In response to
this stimulation, the muscles contract generating a mechanical
twitch. As previously described, current pulses have proved
preferable to voltage pulses, since one is not dependent upon the
variable impedance of the electrode and the skin of the person
using the stimulator.
[0037] Current pulses are supplied over time at a given frequency.
According to the pulse repetition frequency, the muscles do not
have time to relax before the next pulse which increases the
working power of the muscles, but on the other hand, they become
tired. It is thus advantageous to know the fatigue of the
stimulated muscles in order to know the state of the muscles being
exercised and also to be able to take advantage of this measurement
in order to adjust the stimulation parameters automatically.
[0038] In FIGS. 1a and 1b, the stimulator is represented by a case
1 enclosing in particular the current pulse generator and the means
for receiving the signals originating from the sensor. On said case
1, programme selection buttons 2 are used to select the desired
exercising mode as a function of the sport usually practised or the
stimulation programme as a function of the pathological state
(amyotrophy, hypotony, . . . ) of the muscle to be re-educated. The
stimulator also includes a visual display device 3 for displaying
in particular the programmes selected, the stimulation pulses, the
muscle reaction measurement responses, or even statistics for the
exercising sessions. Display 3 is formed for example by a liquid
crystal display.
[0039] One end 4 of a pair of electric cables 5 is connected in a
removable manner to one of the signal input and output sockets of
stimulator case 1. Other sockets for connecting the cable are
accessible for connecting several pairs of electric cables 5. From
the connection to the corresponding socket, the two cables are
joined so that they are not twisted when stored. They are however
separated over the second half of the length of the cables so that
their connector 6 can be fixed to separated electrodes 7. The
connectors have complementary means which can be fixed in a
removable manner to studs 8 of electrode structure 7.
[0040] Muscle reaction measuring sensors, which are not visible in
FIGS. 1a and 1b, are housed in electrode structure 7 or in
connector 6. The sensors are housed either in one of the electrodes
or in one of the connectors or in both. Measurement of the muscle
reactions usually occurs at the location where the current pulse
reaches the electrodes, since the other electrode is used only for
the return of the current.
[0041] A battery housed in the case supplies the stimulator with
power, but it is also conceivable that the stimulator receives an
external voltage supply through connection to the 220V or 110V
mains supply via a transformer.
[0042] In FIG. 1a, the two connectors 6 are shown in a position at
a distance from electrodes 7, since initially, the user places
flexible self-adhesive electrodes 7 with their active surface in
contact with the skin generally on the motor points. In one
embodiment, the self-adhesive surrounds for example the active
surface which occupies more than half of the surface of the
electrode structure.
[0043] Once the electrodes have been placed on the skin, connectors
6 are fixed to electrodes 7, as can be seen in FIG. 1b. In this
embodiment, connectors 6 are mounted so as to rotate freely on
studs 8.
[0044] FIG. 2 shows a first embodiment of the sensor assembly with
the stimulation electrode. Sensor 11 is embedded in the body 18 of
connector 6 in the case in which it is obtained by moulding a
plastic material. In the connector, just above complementary means
10 for the fixation thereof to stud 8 of the electrode, there is an
acceleration meter forming sensor 11 arranged on a printed circuit
13 which includes all the components 12 for amplifying and
processing the acceleration meter signals. The acceleration
obtained by the vibration of the stimulated muscles is of the order
of several g.
[0045] Instead of acceleration meter 11, an acoustic sensor, such
as a microphone can be mounted on the printed circuit to perform
muscle reaction measurements.
[0046] At least two insulated conductor wires, preferably three
wires 14 are fixed onto metal pads of the printed circuit to bring
on the one hand the electric power supply originating from the
stimulator case to the printed circuit components and on the other
hand to send the muscle vibration measurement signals to the
stimulator case. Another insulated conductor wire 15 is fixed to
metal means 10 to bring the current pulses to the electrode. All
the insulated conductor wires 14 and 15 are enclosed in a sheath of
an electric cable 5.
[0047] The electrode structure is composed of a base plane 17 made
of a flexible insulating material, such as a fabric or an
elastomer, able to match the shape onto which it is placed, for
example a user's arm. Below structure 17, a conductive film is
fixed, for example by bonding or deposition of conductive
particles, over a large portion of the surface of structure 17.
This conductive film constitutes active surface 9 of the electrode
via which the current pulses excite the motor-nerves of the muscles
to be stimulated. Metal film 9 is connected through a conductive
hole 16, in particular a metallised hole, made in structure 17 to
metal stud 8.
[0048] The contour of the active surface of electrode 9 is coated
with a self-adhesive material or a self-adhesive film so as to be
able to hold electrode 7 on a user's skin. These electrodes are in
principle disposable electrodes which can be used for one
exercising session or for several sessions.
[0049] In an alternative embodiment, the fixing of the connector to
the electrode structure via a snap fastener can be reversed by
placing complementary means 10 on base plane 17 and stud 8 on
connector 6.
[0050] FIGS. 3a and 3b show a second embodiment of the electrode
sensor assembly. The sensor used in this embodiment is of the
electromyographical type.
[0051] As in the first embodiment discussed hereinabove, connector
6 which is obtained by plastic moulding 18 can include on the
interior thereof all the electronic components for processing the
signals originating from the EMG sensor, but in this variant of
FIG. 3a, all the electronic components are integrated in the
stimulator case.
[0052] Connector 6 includes two metal pots 10 and 20 each
connected, for example by soldering, to the end of a respective
insulated conductor wire 14 and 15, or conversely. The pots, in
addition to a length of the conductor wires and the end of a
flexible sleeve 19 of electric cable 5, are moulded in plastic
material 18 of the connector.
[0053] Electric cable 5 encloses, in this case, only two insulated
conductor wires 14 and 15 in its insulating sheath.
[0054] The electrode structure includes, under base plane 17, a
first active conductive surface 9 of the stimulation electrode and
a second active conductive surface 11 which has no contact with the
first active surface forming the EMG sensor. The second active
surface is placed beside the first active surface. As shown in FIG.
3b, first active surface 9 is made for example with a greater
dimension than second active surface 11. Around the active
surfaces, the base plane is coated or covered with a self-adhesive
material or film to keep it on the user's skin without using other
means.
[0055] In FIG. 3b, the shape of the active surfaces is
approximately rectangular, but other embodiments are entirely
conceivable, for example having first active surface 9 in a
circular shape placed at the centre of the electrode structure and
the second active surface in the shape of a ring placed coaxially
to the first surface.
[0056] Each active surface 9 and 11 is connected, through
conductive holes 16, in particular metallised holes, to a
corresponding metal stud 8 and 21 situated on the other side of the
base plane. Since these studs 8 and 21 are chamfered on their top
portion they are inserted with a certain mechanical resistance into
metal pots 10 and 20 of the connector to be held therein during
use. The forced insertion into the metal pots using chamfers for
guiding assures a good electric contact for the transmission of the
current pulses to the electrode and the electric measurement of the
muscle reactions. Of course, an arrangement as shown in FIG. 2 can
also be applied in this second embodiment.
[0057] Several active surfaces 9 and 11, whether for electric
stimulation or measurement, can be placed under base plane 17. The
active stimulation or measuring surfaces are either all
electrically connected at the surface of base plane 17 through
metallised holes 16, or each connected to a corresponding stud. In
the latter case, a multipolar connector has to be used.
[0058] The two studs 8 and 21, and the two metal pots 10 and 20 can
be designed closer together, but this involves making metal
conductors on base plane 17 on the side of the connector connecting
metallised holes 16 with each of studs 8 and 21.
[0059] It is also conceivable to provide studs 8 and 21 on
connector 6 and metal pots 10 and 20 on base plane 17.
[0060] As previously, the electrodes have a flexible structure to
match the surface of the skin on which they are placed, but there
is nothing to prevent them having a rigid structure.
[0061] FIG. 4 shows a third embodiment with a sensor 11 which is
identical to that shown in FIG. 2. The elements which are the same
as those of FIG. 2 bear the same reference signs, and will not all
be explained again.
[0062] In this third embodiment, cable 5 includes only one
conductor wire 15 in an insulating sheath for bringing the electric
pulses to the electrode. The measuring signals from sensor 11,
processed or unprocessed in connector 6 are, however, sent by
wireless measuring signal transmitting means 22 via electromagnetic
waves 23 or other waves to electronic receiving means in the
stimulator case. These transmitting means are placed on printed
circuit 13 to receive the measuring signals from sensor 11. Waves
23 picked up by the receiving means of the case are converted into
electric signals representing the measurement values of sensor 11
to be displayed on a display and/to adjust the stimulation
parameters.
[0063] A power source for all the electronic components 11, 12 and
22 is provided in connector 6 in the form of an electric battery
27. The positive and negative poles of battery 27 are in contact in
a battery housing with a metal wall 24 for one of the poles and
with a metal base 25 for the other pole. The battery is kept in its
housing by a plug 26 pressing the battery 27 against its contacts
24 and 25. This plug 26 is either screwed in, driven by force, or
soldered.
[0064] Plug 26 could also be omitted, if the battery in its housing
was embedded in the body of connector 6, in the event that it were
not deemed necessary to change it when it becomes flat.
[0065] The connector is mounted in a removable manner on the
electrode structures whether in the first, second or third
embodiments to allow the user to first place the electrodes at the
selected locations without being inconvenienced by the electric
cables. The connector could also be integral with the electrode
structure.
[0066] The means for fixing the connector to the respective
electrode can take various other forms than those mentioned
previously. One can envisage fixing means using a magnet housed
either in the connector, or on the electrode structure, and a metal
part placed either on the electrode structure or on the connector.
This fixing arrangement has to guarantee the contact between metal
pads between the two elements for supplying electric pulses or also
for the sensor measurement.
[0067] FIG. 5 shows by way of illustration three diagrams of the
signals reaching the stimulation electrodes and those drawn from
the muscle reaction or response measurement whether by an
acceleration meter (VMG) or an electromyographical sensor
(EMG).
[0068] A current pulse is first imposed on the stimulation
electrode. This pulse can be monophase, but is preferably biphase
as shown in FIG. 5.
[0069] The maximum amplitude of the current IA is graduated from 0
to 120 mA. The higher this amplitude, the higher the number of
muscle fibres recruited. This thus corresponds to the spatial
recruitment of the fibres which perform the work required by the
selected programme.
[0070] The second diagram of FIG. 5 shows the schematic shape of
the skin electrode voltage. This voltage passes through a maximum
value Vmax of around 100 V and a minimum value of -10 V. After the
current pulse has returned to 0, there remains a residual voltage
Vres of several volts across the electrodes, which is why it is
difficult to use the same active surface to measure the stimulated
muscle reaction voltage variations using an EMG sensor, since the
voltage measured by the sensor Vmes is of the order of a few
millivolts.
[0071] The variations in voltage due to the muscle vibrations and
measured by the acceleration meter (several g) and the EMG sensor
for low frequency current pulses are shown in the third
diagram.
[0072] At higher frequency pulses, when the muscle is contracted,
the acceleration meter provides a signal only during the initial
and final phases of the contraction. Conversely, the EMG sensor
gives a signal even during the muscle contraction phase.
[0073] Thus, in order to obtain measurements using an acceleration
meter, the acceleration signal generated can be measured either by
one or more muscle twitches between the muscle contraction periods,
or by the initial or final phase of the muscle contraction.
[0074] For a strength programme, the frequency of the pulses is
high, whereas for an endurance programme, this frequency is low. It
should be noted that for slow muscle fibres, the frequency is 30
Hz, whereas for fast muscle fibres, it is 60 Hz.
[0075] Following the description which has just been given, several
other alternative embodiments of a stimulator combining an
electrode with a measuring sensor can be envisaged within the reach
of those skilled in the art without departing from the scope of the
invention.
* * * * *