DE102019118402A1 - Targeted electromyostimulation - Google Patents

Abstract

A device is proposed for muscular stimulation of the leg muscles by electromyostimulation, comprising a piece of textile resting on the calf with at least one contact electrode integrated into the piece of textile and an electrical line, characterized in that the device further comprises a piece of textile with at least one sensor for detecting the stance and swing phase of the leg, which is arranged below the foot, wherein the at least one sensor and the at least one contact electrode are connected to one another via a stimulation unit.

Description

FIELD OF THE INVENTION

The invention is in the field of electrical muscle stimulation and relates to a device and a method for muscular stimulation of the leg muscles.

STATE OF THE ART

The collection of data is becoming more and more important in the sports sector. Therefore, sensor-based devices are the best way to get different data on athletic performance. Of course, increasing performance is also a goal that every athlete wants to achieve. The improvement in performance can be achieved in several ways. One possibility is to create additional stimulation to increase muscle strength. This can be achieved through the application of electrical stimuli. So-called electromyostimulation (EMS) is a growing field in the field of training equipment.

EMS is an artificial activation of the muscle through an electrical stimulus. Therefore, the innervation occurs externally and is much faster, since the technical impulse comes directly from the technical device and takes over the function of the brain. The feedback is sent to the brain through the spinal cord.

The stimulus is influenced by various parameters such as frequency, intensity, impulse properties, cycle properties, ramp and electrode properties, and placement (Seyri & Maffiuletti, 2011). These factors are individual, but the main parameter is the intensity of the stimulus. In a review (Filipovic, Kleinöder, Dörmann & Mester, 2012) the various parameters were analyzed in more detail. Both the frequency and the intensity of the respective stimulus depend on the maximum voluntary contraction of the muscles. The impulse properties also differ. All in all, the stimulus should be customized due to the wide range of parameters.

The human gait can be roughly divided into two different phases. The swing and stance phase. These can also be divided into the forward and backward swivel and front and rear support phases. The simplest thing here is the swing and stance phase. The human body is a complex building and a functional interaction of various components such as muscles, bones, joints and tendons. Even when moving, there is always an interaction between these components. For muscle activation, the focus is on the muscles. The different muscles are active in different phases of gait. With increasing running speed, the muscle activation also increases. If you compare muscle activation while running and walking at the same speed, there is a shift in muscle activation of different muscles. (Cappellini, Ivanenko, Poppele & Lacquaniti, 2006). This also applies to the triceps surae and the dorsiflexors such as the tibialis anterior. When running compared to walking, the triceps sura is active earlier before the first contact with the ground occurs. The same applies to the tibialis anterior, but vice versa. Here the activation takes place shortly before the swing phase (Gazendam & Hof, 2007).

There are different strategies for recognizing the gait pattern. One possibility is to record gait patterns using force sensors. Other possibilities are accelerometers, flexible goniometers, electromagnetic tracking systems or sensor tissue. For example, the sensors are attached to different parts of the body. This depends on the study design and the location of the setup (Tao, Liu, Zheng & Feng, 2012). By placing force sensors under the foot, it is possible to record the stance and swing phase (O'Reilly, Caulfield, Ward, Johnston & Doherty, 2018).

A disadvantage of these methods, however, is that they cannot be used to stimulate the muscles alternately. Consequently, it was the object of the present invention to provide a device which overcomes the disadvantages of the prior art and with which it is possible to determine the correct point in time for the stimulation of the muscles in order to be able to ensure effective training

DESCRIPTION OF THE INVENTION

The object is achieved by a device for muscular stimulation of the leg muscles by electromyostimulation, comprising a piece of textile lying against the calf with at least one contact electrode integrated into the piece of textile and an electrical line, characterized in that the device further comprises a piece of textile with integrated sensors for detecting the Includes stance and swing phase of the leg, which is arranged below the foot, wherein the sensors and the at least one contact electrode are connected to one another via a stimulation unit.

Surprisingly, it has been found that a device according to the present invention is advantageous because it is a targeted Enables muscle stimulation individually for the respective gait of an individual.

In one embodiment of the present invention, the piece of textile lying against the calf and the piece of textile which is arranged below the foot are the same piece of textile. In a preferred embodiment of the invention, the piece of textile is a stocking, advantageously a knee-length stocking. This can be put on like any other stocking, with the contact electrodes in the calf area and the sensors in the foot area, that is, when worn, below the sole of the foot. The communication via the stimulation unit can take place in any possible form within the meaning of the invention, with or without a cable. In one embodiment of the invention, the contact electrode and the stimulation unit and / or the stimulation unit and sensor are connected to one another in a wireless form. In one embodiment of the invention, communication with the stimulation unit takes place via Bluetooth, with a Bluetooth module also being attached to the piece of textile.

In a further embodiment of the invention, at least three sensors are present in the piece of textile which is arranged below the foot, that is to say in the area of the sole of the foot. The at least three sensors are advantageously arranged as follows: A sensor is arranged in such a way that it is located under the first proximal toe bone (phalanx proximalis) when the piece of textile is worn. A sensor is arranged in such a way that it is located under the fifth toe ray (Os metatarsale) when the piece of textile is worn. A sensor is arranged so that it is located under the heel when the piece of textile is worn.

In one embodiment of the invention, the stimulation unit communicates via Bluetooth with the contact electrodes which are arranged in the textile item. As a result, the modulation pulses, electrical currents, are transmitted to the contact electrodes and there, due to the skin contact, are transmitted to the muscles in the body of the user. For this purpose, the contact electrodes are designed in such a way that a low contact resistance to the skin is ensured over the entire surface of the contact electrodes. The intended stimulation dose is thus transmitted without, however, irritating the nerves of the skin and causing a stinging sensation that is perceived as unpleasant.

In a further embodiment of the invention, the stimulation unit is connected to the electrodes via a cable. This cable can be fully or partially integrated in the piece of textile.

As already described above, an alternating stimulation of the muscles is advantageously achieved by previously determining the gait via the sensors. This ensures targeted, individual stimulation of the muscles, adapted to the various needs of the user.

In one embodiment of the invention, the stimulation unit is an algorithm. This can record and process the data from the sensors and thus send targeted stimulations to the calf muscles that are timed and matched to the gait.

1. (a) Detektion der Stand- und Schwungphase des Beines über die unterhalb des Fußes angeordneten Sensoren;
2. (b) Übermittlung der gewonnenen Informationen aus Schritt (a) an die Stimulationseinheit;
3. (c) Verarbeitung der Informationen und Weiterleitung eines Signals an die mindestens eine Kontaktelektrode;

dadurch gekennzeichnet, dass durch die Detektion der Stand- und Schwungphase des Beines und die Zwischenschaltung einer Stimulationseinheit, die Beinmuskulatur entsprechend der individuellen Schrittfrequenz mit einem zusätzlichen Reiz stimuliert wird.A further embodiment of the invention is a method for muscular stimulation of the leg muscles by electromyostimulation with the aid of the device described above, comprising or consisting of the following steps:

1. (a) Detection of the stance and swing phase of the leg via the sensors arranged below the foot;
2. (b) transmission of the information obtained from step (a) to the stimulation unit;
3. (c) processing the information and forwarding a signal to the at least one contact electrode;

characterized in that through the detection of the stance and swing phase of the leg and the interposition of a stimulation unit, the leg muscles are stimulated with an additional stimulus according to the individual step frequency.

In a preferred embodiment of the invention, the sensors, the at least one contact electrode and the stimulation unit are arranged in a stocking.

In one embodiment of the invention, at least two contact electrodes are used for the stimulation of the M. triceps surae and M. tibialis anterior. In a further preferred embodiment of the invention, at least four contact electrodes are used, in particular two electrodes for stimulating M. triceps surae, a muscle group that includes, for example, M. gastrocnemii and the flexor Hallucis longus and two electrodes for stimulating M. tibialis anterior as well M extensor hallicus longus. These muscle groups are located on the user's calf or shin.

1 shows an exemplary arrangement according to the invention of four electrodes on a calf protector. Here the calf protector is put on so that the calf protector shown on the left side of the sketch is for the right leg and the one placed on the right for the left leg. The central electrodes are placed on the calves. Both sides can be closed with a zipper at the front of the shin so that the side electrodes are lateral to the tibia.

2 shows an embodiment of the invention according to the invention, wherein the piece of textile represents a stocking. The embodiment according to the invention is shown in four views.

EXAMPLES

Draft of the prototype

In order to ensure the right stimulation at the right time on the right muscles, a further development of the calf protector and thus the placement of the electrodes was necessary. With the prototype ( 1 ) alternating stimulation occurs.

The alternating stimulation must take place individually for each muscle. Because of the two electrodes for M. gastrocnemii and the two electrodes for M. tibialis anterior, the electrical system has a plus and a minus connection for each muscle group. The sensors under the foot record the swing and stance phase. With the placement of three sensors, it is possible to record the initial foot contact (heel sensor) and the toe-off phase (first metatarsal sensor). The third in the area of the fifth toe beam records the initial foot contact for forefoot runners. With this setup, the swing and stance phase for all running techniques (forefoot, rearfoot and metatarsus) can be recognized.

programming

For correct stimulation, as defined by Gazendam & Hof, 2007, the swing and stance phase had to be recorded. In addition, an algorithm was developed that sends the timing for the stimulation to the stimulation unit. It was important that the algorithm learns with every step in order to predict the next step. In a test phase, an Arduino Nano was used for one leg, which was connected via a Bluetooth low energy module (RN4020).

With these Bluetooth connections, the commands could be sent to the stimulation unit. The stimulation unit regulates the intensity of the stimulation and is also an energy supplier.

In order to recognize the swing phase, a timer was set between two events. The first event that the timer starts is the triggering of the sensors - i.e. the last foot contact with the floor.

This definitely should S1 his (forefoot, metatarsal or rearfoot blow). To stop the timer, a second event had to occur. This is the foot's first contact with the ground. Therefore, several options are possible. Depending on the running technique, the timer stops when it detects the pressure on S1 or S2 or S3. In this way, the swing and stance phases could be determined for each step (t ₁ , t ₂ , t ₃ ... t _x ).

Stimulation timing

In order to stimulate the muscle at the right time, further parameters are involved. The calf muscle group should be stimulated at some point before taking the next step. In this case, this is defined at a specific point in time when the calf muscle group contracts shortly before the first foot contact. It was therefore necessary to take the mean of the last ten stance phases (T). This mean value had to be subtracted with a certain parameter (t _B ). t _B is defined as 86% of the flight time (see Gazendam & Hof, 2007). The difference between this point in time and the initial foot contact is defined as t _B and is calculated for each next step. $$t_{\mathrm{S.}timcalf\text{-}GrOup}=\mathrm{E.}\left(t_{n-9}-t_n\right)-t_{\mathrm{B.}}$$

To have an algorithm that adapts to running speed and cadence, a moving average must be implemented. For this reason, the last ten steps were used to calculate the mean. With the last ten values, the mean value is more stable than when using each swing time for the calculation. Outliers also have less of an impact on the algorithm. The possibility is also established to adapt to different speed levels while running.

methodology

To assess the functionality of the prototype, a running simulation was carried out in which 40 steps were recorded.

This was done by collecting data from the Arduino's serial monitor, simulating a hindfoot technique with uneven running speed and thus uneven swing times.

The data analysis was done using Excel to compare the calculated values of the working prototype and the expected values.

Results

The timing of the stimulation of the calf muscle group was the main indicator for evaluating the function of the algorithm and thus the correct timing for the stimulation of the calf muscles. The simulated time values of 40 steps were compared with the expected values.

In order to obtain the simulated values, the last ten swing times were analyzed using the algorithm in order to predict the next step and to send the stimulation after a calculated time. The expected values were used to compare the prediction with the real data. They were calculated using the data already measured such as backward analysis. With the algorithm, the predicted values were close to the expected values if the running speed and thus the swing time is constant (step 20-32, 3 and 4th ). In 3 the time of stimulation for the calf muscle group is given. As time changes, we assume a change in speed. In this case the speed change was very high and abrupt.

4th shows the results with a safety factor taken into account. This shows that the deviations in the negative direction are much smaller (black bars). The deviations in the positive direction remain the same (gray bars). The safety factor eliminates outliers when a faster step is taken. If the step is faster, the algorithm would switch on the stimulation after contact with the ground, which is not desired by the movement sequence. This defines the safety factor that the stimulation starts at the latest when the next foot strike occurs. Another safety factor is to switch off the stimulation if the foot is in the air for longer than a certain time or if the foot is on the ground for longer without any action. This prevents the risk of injury.

The minimum deviation between expected and calculated values Diffmin = 0 ms. The maximum deviation Dif f _max = 372.26 ms.

To compare the calculated and simulated values, it was important to compare the standard deviation as well as the maxima and minima. Therefore, Simulated _min = 658 ms, Expected _min = 609.74 ms. The values are therefore almost the same. The values for Simulated _max and Expected _max each correspond to 1291 ms. The standard deviation is higher for the expected data (SD _expected = 115.60 ms) than for the simulated data (SD _simulated = 110.61 ms).

discussion

In the 3 and 4th the attitude to the stimulation of the calf muscle group is clearly visible. The functionality of the prototype could also be demonstrated, and the stimulation was carried out on the correct physical function of the muscles. It has therefore been shown that the device according to the invention can be used on the treadmill and that this advantageously stimulates the leg muscles with an additional stimulus in accordance with the individual step frequency.

Claims (10)

Device for muscular stimulation of the leg muscles by electromyostimulation, comprising a piece of textile lying against the calf with at least one contact electrode integrated into the piece of textile and an electrical line, characterized in that the device further comprises a piece of textile with at least one sensor for detecting the stance and swing phase of the Includes leg, which is arranged below the foot, wherein the at least one sensor and the at least one contact electrode are connected to one another via a stimulation unit. Device according to Claim 1 , whereby the piece of textile lying against the calf and the piece of textile which is arranged below the foot is a stocking. Device according to Claim 1 and / or 2, where at least three sensors are contained in the piece of textile which is arranged below the foot. Device according to Claim 3 , wherein one of the sensors is arranged in the textile piece so that it is located under the first proximal toe bone when the textile piece is worn. Device according to Claim 3 , wherein one of the sensors is arranged in the textile piece so that it is located under the fifth toe beam when the textile piece is worn. Device according to Claim 3 , wherein one of the sensors is arranged in the textile piece so that it is located under the heel when the textile piece is worn. Device according to at least one of the preceding claims, wherein the sensors, the at least one contact electrode and the stimulation unit are connected to one another via a cable or wirelessly. Method for the muscular stimulation of the leg muscles by electromyostimulation with the aid of the device according to FIG Claim 1 , comprising or consisting of the following steps: (a) Detection of the stance and swing phase of the leg via the sensors arranged below the foot; (b) transmission of the information obtained from step (a) to the stimulation unit; (c) processing the information and forwarding a signal to the at least one contact electrode; characterized in that through the detection of the stance and swing phase of the leg and the interposition of a stimulation unit, the leg muscles are stimulated with an additional stimulus according to the individual step frequency. Procedure according to Claim 8 , wherein the sensors, the at least one contact electrode and the stimulation unit are arranged in and / or on a stocking. Procedure according to Claim 8 and / or 9, where at least two contact electrodes are used for the stimulation of M. triceps surae and M. tibialis anterior.

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