A.V. Illarionova, postgraduate student
L.V. Kapilevich, professor, Dr.Med.
National Research Tomsk State University, Tomsk, Russia

Key words: muscles, bioelectrical activity, graduated power, coordination.

Introduction. The bioelectrical activity of muscles when performing exercises for accurate power graduation during balance training (unbalanced surface training) was investigated. According to the findings, it is important for the development of coordination to form the ability to dose muscular power and to distribute the load between the muscles when performing comprehensive coordination actions. It is accompanied by the multiphase EMG and synchronous achievement of peak amplitude and frequency characteristics of EMG. Reduced accuracy of test effort during the unbalanced surface training is accompanied by an increase in the number of multi-phase EMG and decrease in the number of EMG with the presence of hyper-synchronous high-amplitude potentials.

The accuracy of movements is provided by regulating external and internal power related to the human body arising when implementing a motor task [2]. In this case, the object of control is muscular efforts that induce and regulate movements rather than the movements themselves [1]. One of the ways to improve the coordination abilities is to develop the accuracy of perception and reproduction of efforts applied when dealing with various kinds of motor tasks [6]. 

The purpose of the present research was to investigate the bioelectric activity of muscles when performing exercises intended to train accurate power graduation in the context of balance training.

Materials and methods. The research was performed using the multifunctional equipment «HUBER». A special feature of this device is a multisensory effect on proprioception, exteroception and sense organs of the patient during isotonic and isometric effort in various ways of implementing a motor task that vary by the speed and the amplitude of motion of the mounting platform [5].

 The surface electromyogram (EMG) was registered using the electromyograph «BTS FREEMG 300» by the «BTS Bioengineering» company.

Twenty men of the age of 19-26 were examined. Two groups were formed. The core group consisted of candidate for masters of sports in skiing (10 men). The control group consisted of 10 men not doing sports.

The subjects were asked to perform a test task: staying on a fixed platform, perform pressure and traction on the strength measuring elements of the device with their upper limbs, using their utmost force.   Testing (reference) efforts obtained were then to be reproduced while in the same position, but on the rotating platform (20 rotations per minute, slope of the platform being up to 5^о). At the same time during the rotation of the platform a feedback element was used with regards to the accuracy of the task performance by means of visual color information that was received from the coordination board of the device.

Results and discussion. During isometric exercise all muscle groups get involved into the performance simultaneously due to specific characteristics of these exercises. At the same time there are different variations with respect to the phase coherence of strain and relaxation of muscles [3]. We have identified the following EMG patterns obtained during exercising on the «HUBER» device (Figure 1):

1. Even EMG characterized by a gradual increase of the amplitude and frequency characteristics of bioelectrical activity up to a certain relatively stable value, keeping it for a certain time and then gradual decrease of the said parameters.

2. EMG characterized by maintaining constant tension in the muscles both during exercise and between sets.

3. Multi-phase EMG characterized by the presence of several gradually increasing and decreasing amplitude and frequency peaks of bioelectrical activity.

4. Firing-like EMG characterized by a sharp upsurge of amplitude and frequency parameters of bioelectrical activity during a short time at the beginning of the phase of strain followed by a rapid decline of these parameters.

5. EMG of the stage of fatigue characterized by the presence of high-amplitude hyper synchronous potentials superimposed on a background of rich EMG and exceeding its amplitude.

The most common pattern during the test tasks performance in the group of athletes is multi-phase EMG, indicating that the current load is not the maximum one for the body and its further increase is possible. At the same time the athletes tend to simultaneously engage all the muscles involved in the movement and synchronously achieve peak amplitude and frequency parameters of EMG.

For the group of untrained people the most characteristic pattern is that of EMG of the stage of fatigue containing a large number of high-amplitude hyper-synchronous potentials superimposed on a background of rich EMG. Apparently, the main obstacle in achieving a better result in the control group is poorly developed skeletal muscles (especially in terms of strength endurance); their strain leads to feeling fatigue faster (compared with the group of athletes) and prevents the establishment of a coherent interaction between muscle groups involved in the exercise.

The largest number of EMG with the symptoms of fatigue (that is, presence of hyper-synchronous potentials) was recorded during the first (in both groups) and the second (in the group of untrained men) test tasks performance, and this number reduced by the time the fourth task was performed. In the fourth exercise multi-phase EMG dominated in case of all the subjects, and muscle work was most synchronous (especially in the group of athletes). At the same time by the time the fourth task was performed an increase was noted between the reference and reproduced values that was larger for the untrained men and smaller for athletes (Figure 2) as well as decrease in the average duration of the reproduced effort.

It can be assumed that hyper-synchronous potentials are provoked by strenuous training as a result of the summation of action potentials of a large number of synchronized motor units. The low intensity muscle work is accompanied by low frequency nerve impulses and the involvement of a small number of motor units, resulting in the multi-phase EMG registered [4]. Thus, as fatigue was accumulated, the subjects continued to demonstrate a good reference result, but it was more difficult for them to reproduce it.

Conclusions. The results obtained indicate that formation of the ability to control muscular efforts

and distribute the load between muscles when performing comprehensively coordinated moves are important factors of coordination development. This is accompanied by the multi-phase EMG and the synchronous achievement of peak amplitude and frequency values of EMG parameters.

Reduced accuracy of test effort reproduction while performing the exercises on a mobile platform is accompanied by an increase in the number of multi-phase EMG and a decrease in the number of EMG with high amplitude hyper-synchronous potentials.  

References

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6. Koshelskaja, E.V., Kapilevich L.V., Bajenov V.N., Andreev V.I., Buravel O.I. Physiological and Biomechanical Characteristics of the Kick and Goal Techniques of Football Players // Bulletin of Experimental Biology and Medicine. 2012. V. 153. I. 2. P. 266–268.

Corresponding author: kapil@yandex.ru