RU2491886C2 - Method for estimating load strength with specifying moment of aerobic-anaerobic transition as shown by electromyogram and working muscle ir-spectroscopy findings - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention refers to medicine, diagnostics, may be used in sports and rehabilitation therapy. When estimating a load strength whereat the muscular work power supply for a linear increasing load test starts involving the active anaerobic processes, the moment of aerobic-anaerobic transition (MAAT) is shown by a maximum position of a time history curve of the hemoglobin concentration in the working muscle measured by IR-spectroscopy to intensity or a high-frequency component of the surface electromyogram of the above muscle.

EFFECT: method provides specifying the MAAT with no near-limit loads used, with enabled MAAT estimation in separate relatively lightweight muscles which when contracted cause no visible changes of the systemic physiological values, simplicity and non-invasiveness of the procedure.

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Description

The invention relates to medical diagnostics and can be used in sports and rehabilitation therapy to determine the aerobic-anaerobic transition according to an electromyogram and IR spectroscopy data of a working muscle.

It is known that the energy supply for long muscular work (more than 5 minutes) is predominantly aerobic [1, 2]. In this regard, the assessment of the intensity of aerobic processes during work is the main indicator of human performance, which is widely used in sports and in rehabilitation medicine to diagnose the functional state and select the optimal load when conducting sports and rehabilitation trainings. To determine physical performance usually use a test with increasing load. As a result of such testing, maximum indicators are determined that characterize the performance of the cardiorespiratory system, such as maximum oxygen consumption (MIC) and maximum cardiac output (MSV), and the load power at which an aerobic-anaerobic transition is observed, i.e. when anaerobic processes begin to be actively involved in the energy supply of muscle work.

To assess the power at which an aerobic-anaerobic transition occurs in a test with a linearly increasing load, systemic physiological parameters are usually used [1, 2]:

1. The dynamics of the accumulation of the concentration of lactate (lactic acid) in the blood, which determine the aerobic threshold, lactate threshold, anaerobic metabolism threshold (ANSP). These values are determined by the power developed by the subjects, at which the concentration of lactate reaches a certain level. So, for example, it is believed that when working with large muscle mass, the level of PANO is achieved at a concentration of lactate in the blood of 4 mm. A drawback of the methods for detecting the aerobic-anaerobic transition in working muscles by the concentration of lactate is its invasiveness - the need to take a blood sample (from the finger in case of work of large muscle mass). With contractions of small muscles, the concentration of lactate in capillary blood remains almost unchanged; to determine the lactate content in muscle tissue, catheterization of a vein is required, which leads to the outflow of blood from a working muscle - a complex and unsafe procedure. Generally speaking, the concentration of lactate in muscle tissue can be determined using NMR spectroscopy, but this method requires expensive, unique devices (MRI scanners with spectroscopic attachments and, in addition, providing the ability to perform muscle work during measurements).

2. The dynamics of pulmonary ventilation and gas exchange indices, with the help of which they determine the ventilatory threshold, the point of respiratory compensation, and other indicators that also reflect the aerobic performance of a person. It should be noted that the experimental recording of the dynamics of these physiological parameters is a fairly methodologically simple procedure, however, determining the moment of aerobic-anaerobic transition is a rather complicated problem, since it usually requires finding the position of singular points (inflection points, points at which deviation from linearity, etc.) on a dynamic curve. In practice, the consequence of this is the low accuracy of determining the desired quantities, the difficulty of comparing these values obtained by different authors using different calculation algorithms. In addition, to determine the values characterizing the moment of aerobic-anaerobic transition, it is necessary to analyze the entire curve that describes the changes in the selected physiological parameters in the test with a linearly increasing load power, and the final period of the test, when the subject performs muscular work with power, is especially important for analysis. close to the limit. It should be noted that the fulfillment of the ultimate work by the subjects is not always possible (testing of patients with cardiovascular disorders to determine individual loads optimal for rehabilitation training, testing of highly qualified athletes in the competitive period, etc.). In addition, this approach is also possible only with "global" muscle work, in which large muscle mass is involved.

Some authors [3] suggest using a surface EMG signal to determine the power at which an aerobic-anaerobic transition occurs in a test with increasing load. The disadvantage of this method is the large fluctuations in the electromyographic signal, as well as a strong dependence of the accuracy of this method on the length of the recording section above the point of aerobic-anaerobic transition. It should be borne in mind that the intensity of EMG activity with a linear increase in load power increases unevenly, which leads to significant errors in determining the aerobic-anaerobic transition at the inflection point.

For non-invasive registration of processes associated with the development of muscle fatigue, the infrared spectrometry method, which provides indicators characterizing the oxygenation of muscle tissue, is often used. In particular, it is known that the blood supply of muscle tissue is determined by the hemoglobin content, and a change in the concentration of the deoxygenated form of hemoglobin in a working muscle reflects oxygen consumption by active muscle fibers (MB).

The technical result of the claimed invention is that during the execution of the test with a linearly increasing load, stable recording of a weak signal of the surface EMG of the working muscle and measurement of the content of various forms of hemoglobin in it are provided, which allows determining the moment of aerobic-anaerobic transition by the dynamics of the recorded parameters, including on-line mode, the method does not require a test at load capacities close to the limiting, it provides an opportunity to assess the moment of aerobic-anaerobic enter the individual small muscle mass, reduced that even at maximum power does not lead to noticeable changes in the system of physiological parameters, in addition, it is methodologically simple and does not require invasive procedures associated with taking blood samples from the subject.

The claimed technical result is achieved due to the fact that the method of determining the power of the load, in which anaerobic processes begin to be actively involved in the energy supply of muscle work when performing a test with a linearly increasing load, characterized in that the moment of aerobic-anaerobic transition is determined by the position of the maximum on the curve reflecting the dynamics of changes in the ratio of the intensity of the surface electromyogram or its high-frequency component to the concentration of hemoglobin in the working muscle, we measure Oh using IR spectroscopy.

In the proposed method for determining the moment of aerobic-anaerobic transition in the test with a linear increase in the load power, in addition to the EMG signal, which reflects the process of recruiting motor units (DE), the information obtained by the method of IR spectroscopy on the change in the concentration of hemoglobin in the working muscle is used. The moment of aerobic-anaerobic transition is determined by the position of the maximum on the smoothed curve of the ratio of hemoglobin concentration to EMG intensity, determined by the rms signal amplitude. Instead of the native EMG signal, it is possible to use its high-frequency component (f> 75 Hz), which is important from a practical point of view, since low-frequency artifacts associated with changes in muscle geometry when it is reduced, as well as industrial frequency pickups, which are often the main obstacle, are cut off stable registration of a weak signal of surface EMG. The proposed approach does not require the entire test to be performed to analyze the obtained dynamic curve, and therefore, this method of determination can be used on-line. In addition, this technique is also suitable for assessing the moment of aerobic-anaerobic transition in individual muscles, the reduction of which even at maximum power does not lead to noticeable changes in systemic physiological parameters.

Figure 1 shows the experimentally obtained dynamics of changes in the EMG intensity of one of the test subjects in a test with a linearly increasing (15 W / min) load power on a bicycle ergometer (a bold line shows a smoothed curve used to determine the moment of aerobic-anaerobic transition). It can be seen that, despite a linear increase in power, the EMG intensity increases nonlinearly. This is especially pronounced at the end of the test, when high-threshold motor units are included in the work. Obviously, on such a curve it is rather difficult to determine the inflection point - the moment corresponding to the aerobic-anaerobic transition.

Figure 2 shows how, during the test, the concentration of hemoglobin [cHb] in the working muscle changes in the same test subject. The scatter of [cHb] values reflects its changes during one cycle of movement, (a smooth line shows a smoothed curve). As noted above, this indicator reflects the blood supply to the working muscle. It is seen that at the end of the test, a gradual deviation of the [cHb] dynamics from a monotonous increase is observed, the curve reaches a plateau, and even a slight decrease in this indicator is noted. This dynamics, apparently, can be explained by an increase in the vasoconstrictive effects of the sympathetic nervous system caused by the activation of chemoreceptors in the working muscle due to the accumulation of metabolic products in it (metaboreflex). As in the case of EMG, it is often also difficult to determine the power at which the aerobic-anaerobic transition in the test with increasing load is obtained from one such curve.

It can be seen that the dynamics of nonlinear sections in the graphs reflecting EMG activity and blood supply to the working muscle is qualitatively different at the end of the test - the concentration of hemoglobin goes to a plateau or even decreases slightly, while the intensity of EMG increases sharply. Therefore, to determine the moment of aerobic-anaerobic transition, it is convenient to use the dynamics of the ratio of these multidirectional indicators. Figure 3 shows the dependence on the load power of the ratio of hemoglobin concentration to the rms amplitude of EMG (dynamics of the ratio of the concentration of hemoglobin in m.vastus lateralis to the intensity of its EMG activity during the test; smoothed curves were used to calculate [cHb] / EMG). It can be seen that the curve has a pronounced maximum.

The maximum position on this curve determines the power corresponding to the aerobic-anaerobic transition (AAP _{EMG / cHb} ) in the test with a linearly increasing load. To confirm the proposed method, an experimental study was conducted in which young, physically active subjects (10 people) performed a test on a bicycle ergometer with a linearly increasing load power (slew rate - 15 W / min) until refusal to continue work. During the test, the subjects continuously recorded surface EMG (silver chloride skin electrodes superimposed on the middle part of m. Vastus lateralis were used) and the hemoglobin content in this muscle, measured using IR spectroscopy (NIRO-200 spectrophotometer, Hamamatsu Photonics, Japan) (see Fig. 1, Fig. 2). In addition, during the test, subjects took a blood sample (20 μl) from a finger every two minutes to determine the lactate concentration (SuperGLeasy + analyzer, DrMuellerGmbH, Germany). Thus, the load power that corresponds to the aerobic-anaerobic transition was determined in two ways: by the concentration of lactate in capillary blood (AAP _La ) - the power at which the concentration of lactate reaches 4 mM [1], and by the maximum ratio [cHb] / EMG. A statistically significant correlation was found between these values (r = 0.78, p <0.05), on average for the group of subjects

$$〈\frac{\mathrm{BUT}\mathrm{BUT}{P}_{HHb/EMG}}{\mathrm{BUT}\mathrm{BUT}{P}_{La}}〉=0.96\pm 0.10$$

It should be noted that the transition from predominantly aerobic provision of muscle contraction to aerobic-anaerobic is not an instantaneous event; this transition is recorded by smooth changes in the dynamics of some physiological parameters, which in one way or another reflect changes in muscle metabolism. The load power at which the aerobic-anaerobic transition is recorded can noticeably vary when using different methods for its determination, but this is not a significant drawback, since in practice it is usually not the absolute value that is important, but its change due to one or another effect on the human body. In sports and medical practice, this indicator of a person’s aerobic performance, measured using the same selected technique, is usually used to determine the effectiveness of sports or rehabilitation workouts.

The proposed method for estimating the moment of an aerobic-anaerobic transition in a test with a continuously increasing load by the integrated EMG intensity and infrared spectroscopy data of a working muscle is methodologically simple and does not require invasive procedures associated with taking blood samples from a subject. In addition, the advantages of the proposed method include the ability to determine with its help the moment of aerobic-anaerobic transition in small muscles.

Information sources

1. Kindermann W, Simon G, Keul J. The significance of the aerobic-anaerobic transition for the determination of work load intensities during endurance training. Eur J AppI Physiol Occup Physiol 1979; 42: 25-34.

2. "Method for assessing aerobic-anaerobic transition"

http://www.belmapo.by/downloads/sport_med/2011/sport/14.doc

3. Koryak Yu.A. Neuromuscular changes under the influence of seven-day mechanical unloading of the muscular apparatus in humans // Fundamental research. - 2008. - No. 9 - P.8-21 URL: http://www.rae.ru/fs/?section=content&op=show_article&article_id=7781229, http://www.rae.ru/fs/pdf/2008 /9/1.pdf

Claims (1)

A method for determining the load power at which anaerobic processes begin to be actively involved in the energy supply of muscle work when performing a test with a linearly increasing load, characterized in that the moment of aerobic-anaerobic transition is determined by the position of the maximum on the curve reflecting the dynamics of the change in the ratio of hemoglobin concentration in the working muscle, measured by infrared spectroscopy, to the intensity or high-frequency component of the surface electromyogram of this muscle.