Electromyography is a diagnostic method that is used to register the electrical potential of the muscles in order to examine the neuromuscular system. The first myogram was registered by N. E. Vvedensky in 1884 when he used a telephone device. While the first graphic representation of the electromyogram was created already in 1907. The field of myography started to grow only during the 30’s and the 40’s. This can be explained by the high requirements to such important parameters as accuracy and the quality of the signal. These days we are able to use a huge number of high-quality amplifiers allowing us to get the lowest level of AC interferences in the wide spectrum range (it can reach 10 000 Hz in case of EMG). Such devices caused serious technical advancement in the field of the clinical application of the electromyography.
In general meaning, the neuromuscular system of the body is a functionally united complex of the skeletal muscles and peripherical parts of the nervous system. A functional unit of the neuromuscular system is a motor unit (MU), which contains one motoneuron, its axon and innervated muscle tissues. The contraction of the muscle happens as a result of getting excitation through the motor fibers.
The excitation between the muscle and the neural fibers is transmitted in the neuromuscular synapse. Depending on the functional function of the MU, it may contain a different number of fibers: from 10-25 in small muscles, and up to 2000 in the biggest once. The overall electrical activity of the muscle MU creates a signal, i.e. electromyogram, which is used as the foundation of the electromyographic analysis.
General technical terms
Neurotech Medical Scientific Company is working in the field of manufacturing and developing of the medical equipment for more than 20 years. During the last 5 years, we are actively developing the product range for the sports medicine. One of the main priorities of the company is to develop a wide range of devices form myographic analysis, which can be used as both classic devices for myography in the field of traditional medicine and as portable devices for the related fields. One of our main openings is the wireless sensor for myography. A wireless sensor is a multifunctional device, which has several models, and can be used to register EMG, ECG and other biological potentials, as well as to create electrical stimulation impulses. The main purpose of the wireless sensor is to provide the full range of examinations and therapeutical procedures, including the registration and the analysis of EMG, the EMG and ECG BFB training, the monitoring of the muscular activity for the sports medicine, as well as to perform various diagnostic and rehabilitation procedures in the field of kinesiology etc.
The wireless connection with the sensor is established using a radio channel (2.4 GHz or Bluetooth LE) between the sensor and the device for visualization (it can be a PC, a mobile phone etc.)
The main advantage of the wireless registration is the minimum level of motion artifacts, which gives the patient the freedom of movement and even walking around.
The wireless sensor is a convenient tool to register the biological potentials of an athlete performing various exercises. Wireless design of the device allows minimizing the level of motion artifacts and allows to perform the comprehensive analysis of the processes, which can't be evaluated with traditional wired devices.
Such sensors allow registering the biological potential of the muscles (electromyogram) in order to monitor the activity during the motion. By doing so, one can evaluate and compare the roles of the different muscles in the motion pattern. The user is able to register the electrocardiogram at the very same time, and perform accelerometric analysis of movements and retrieve information from the gyroscope.
Using wireless EMG registration in the field of sports
Before starting the analysis of the potential usage of the wireless EMG registration for the team of archers our specialists have gained a lot of experience in other sports, including speed skating, hockey, and football.
Those sports had almost the similar goal, i.e. to find the dependence between the power of an action (the first movement for skaters, and the punch for boxers) and the speed of EMG increase. Those tasks were successfully completed. We were able to divide the skaters into several groups according to their EMG, as well as the genetic blood test. We also divided boxers according to the power of their punch.
In the case of the archers, we have a slightly different task in the field of EMG. We need to understand, which muscle is more involves the process of bow bracing and shooting. We performed our tests and experiments in the city of Taganrog (Specialized Children and Youth Sports School of the Olympic Reserve #13) and later in the city of Antalya (Turkey) during the training camp in the period from 23rd till 26th of October.
Finding the possibility to use wireless EMG registration technologies in the field of archery
Results obtained during the tests with the members of the Russian team are the most interesting ones. We want to offer you a comparison of those results in order to make them more illustrative. A. Makhnenko, an athlete from the Russian team, agreed to participate in our experiments. Wireless sensors produced by Neurotech Company were used for the registration purposes. They were attached right above the examined muscles using adhesive disposable electrodes. Each sensor is an independent single-channel electromyography, which connects with the personal computer using a wireless interface.
After that, we used special software to register and process the electromyogram in order to record and store it in the database.
The first test involves flexors and extensors of the palm.
When the archer is bracing the bow, he involves the only extensor. When he starts to pull, he activates the flexor, which was around 20% more powerful than the extensor. Both muscles were relaxed immediately after the shot.
The second test involved three muscles: biceps, triceps, and back.
During the process of bracing and shooting the triceps was almost totally relaxed (the upper EMG channel). The biceps took the main load during the process of bracing. When he started to pull, he activated the back, simultaneously relaxing the biceps. The biceps were slightly contracted at the moment of the shot, being sharply relaxed immediately after that. The triceps became relaxed at the same time, while the back was contracted for 1.5 seconds more.
The third (informative) test was carried out with sensors on the left chest, and on the back (two sides).
The chest is slightly involved in the process of bracing and shooting, while two back muscles spared the load. The difference is that the right muscle became active in 1 second after the left, and it was released in 1 second after the left.
We can make the following conclusions after the tests:
1. The wireless sensor is an efficient way to register myogram in order to control the muscular contraction of archers. Unlike all other wired solutions, our devices can’t be considered an obstacle for the athletes, furthermore, they allow avoiding motion artifacts, which is one of the main problems of all wired devices. Such motion artifacts make is simply impossible to evaluate the dynamic changes.
2. Information in the form of myographic signals registered during the process of bracing, pulling and shooting can serve as an additional indicator that allows controlling the overall muscular contraction of an athlete, and perform required correction.
Future of the system
In future, we plan to implement biofeedback solution into the sensor in order to represent the muscular activity of an athlete in the form of a chart. The method of evaluation allows creating a so-called “muscular portrait” of the athlete. After that, the athlete can use special correction methods in order to change and improve their “muscular portrait” and control their muscles.
In case if a muscle works properly, the chart will be green, indicating the current level of contraction. In case if the muscle is almost fine, the chart will be yellow. In case if the muscle is too relaxed or contracted, the chart will become red. By using such visual representation, the athlete has to make all the charts green and learn the action, which results in proper movement of the muscles.