**3. Assessment of the degree of asymmetry by the measured muscle strength of the limbs**

The main purpose of segmental body examination methods is to obtain estimates of the composition and differences of individual body segments. Such analysis can be performed both statically and dynamically to investigate the differences between segments under various influences. The body segments analyzed are usually the limbs and trunk, and in some cases the head.

The asymmetry of the structure of the human body, expressed to a greater extent in the limbs, is a widespread phenomenon. The degree of this asymmetry is affected by the way of life, the experience of a person's professional activity, which is manifested in the aggregate of signs of inequality in the functions of arms, legs, halves of the body, and face during the formation of general motor behavior.

Even in relatively uniform cross-sectional areas of the body, the musculoskeletal mass is unevenly distributed. For example, in the overwhelming majority of the world's population, the right hand is superior to the left in strength. This symmetry is expressed by the formula

$$\mathbf{A} = \mathbf{S}/\mathbf{D},$$

where D - muscle strength of the right, S - muscle strength of the left hand [13]. This ratio is less than one for right-handers, more than one for the left, and equal to one for ambidextra.

There are different methods and means for assessing asymmetry (anthropometric, bioimpedance analysis, assessment of strength indicators, etc.), which allow such comparisons to be made both quantitatively and visually [14–17].

To assess the asymmetry of the limbs of the studied patients, the results of in vivo experiments were used using a 12-channel ME6000-EMG device. We studied the biopotentials of three muscles of the lower extremities, two of them lateral and one medial direction (**Table 3**). Measurement time - 30 sec.

For the studied muscle types, 6 leads were used, thus six signals were recorded for the right (R) and left (L) sides. **Table 4** shows the values for three examples of the maximum amplitudes of biopotentials in microvolts, the values of which are proportional to the muscle strength of the objects under consideration.

For the corresponding leads for the left and right sides, the difference in the maximum amplitude values of the signals can be estimated as follows, for example:

Δ*A QFM* ð Þ¼ *:rf QFM:rf max*ð Þ� *L QFM:rf max*ð Þ *R*

For one and the same derivation, when calculating the average value of the difference in amplitudes (AVDA), it is necessary to take into account the difference of all measured values. For instance,

$$\begin{aligned} \text{AVDA} &= \left(\Delta \mathbf{A}\_{\text{npus. 1}}(\text{QFM.pf}) + \Delta \mathbf{A}\_{\text{npus. 1}}(\text{QFM.vl}) + \Delta \mathbf{A}\_{\text{npus. 1}}(\text{QFM.vm})\right) \\ &+ \Delta \mathbf{A}\_{\text{npus. 1}}(\text{QM.lp}) + \Delta \mathbf{A}\_{\text{npus. 1}}(\text{QM.mp}) + \Delta \mathbf{A}\_{\text{npus. 1}}(\text{BFM})\right) / \Theta \end{aligned}$$


**Table 3.** *Studied biopotentials.* *Methods and Tools for Assessing Muscle Asymmetry in the Analysis of Electromyographic… DOI: http://dx.doi.org/10.5772/intechopen.103061*


#### **Table 4.**

*The values for three examples of the maximum amplitudes of biopotentials.*


#### **Table 5.**

*The difference in the maximum amplitudes of the received signals (in percentage terms).*

#### **Figure 4.**

*Comparison of the average values of the measured signals for different leads for two examples.*

For the corresponding leads, the difference in the maximum amplitudes of the received signals (in percentage terms), as well as the difference in the average values of the measured signals, are shown in **Table 5**.

Comparison of the average values of the measured signals for different leads for two examples (in the form of histograms) is shown in **Figure 4**.

For example 1, it can be seen that only for one muscle QFM-vl there is a pronounced asymmetry, and for other muscles relative to the mean value there is no tendency to asymmetry. In example 3, the maximum asymmetry is observed in lead BFM; however, there is a tendency to asymmetry in leads QFM-vl and QM-mp. In this case, the average value of the difference in amplitudes can be used as the degree of asymmetry A, since this value is with the difference in muscle strength measured from the corresponding muscle of the limbs.

It is possible to conventionally accept the range of variation of A from 0 to 1. If we accept the degree of asymmetry equal to 0.5 as an average level, then the value <0.5 is estimated as a low degree, and the value >0.5 as a high degree of asymmetry. For the examples shown, the degree of asymmetry can be assessed according to the following scale (**Figure 5**).

#### **Figure 5.**

*Scale of the degree of asymmetry.*

The proposed approach makes it possible to quantitatively assess the severity of the asymmetry of the studied limbs.

If you use directly the measurement results using the 12-channel ME6000-EMG device, then the measurement results are reflected in the protocol—**Figure 6** (for two examples).

For the leads used (left and right), 12 signals of the studied muscle are recorded during the period of innervation and reinnervation. In this case, the assessment of the measurement results is carried out visually to the values of biopotentials, proportional to the muscle strength of the object under study. As can be seen from **Figure 3**, these values are maximum for the Quadriceps femoris muscle - vastus lateralis.

For the first example, the maximum value of muscle strength corresponds to the 9th line, for the second example it is the 3rd line. However, it is impossible to establish the degree of asymmetry of the studied muscle in a particular patient from the given measurement protocol. It is possible to group the results of measurements of muscle strength for different muscles of patients—**Figure 7a, b**. The obtained histograms for the left and right sides of the studied muscles of patients do not make it possible to assess the degree of asymmetry and the magnitude of this asymmetry, since the maximum values for different leads (QFM-vl and QFM-vm) can be maximum.

Thus, in comparison with the results of direct measurements and with the subsequent visualization of the obtained protocol, the proposed method for assessing the degree of asymmetry, and then the severity of asymmetry of the muscles under study, is more acceptable.

To obtain reliable and reproducible results on the example of 30 patients, all requirements of the measurement procedure were met.

#### **Figure 6.**

*The measurement results using the 12-channel ME6000-EMG device.*

*Methods and Tools for Assessing Muscle Asymmetry in the Analysis of Electromyographic… DOI: http://dx.doi.org/10.5772/intechopen.103061*

**Figure 7.**

*Grouping results of measurements of muscle strength for different muscles of patients.*

Assessment of the degree of asymmetry of muscle strength according to the proposed method allows an expert doctor to accurately assess the differences in the biopotentials of the studied muscles of the limbs and effectively use the treatment method to reduce the degree of asymmetry.
