Russian Journal of Biomechanics

The stress-strain state of the human eye, which cornea in its apexis is weakened after myopia surgical correction, is studied. The elastic system “cornea-sclera” is presented as two joint transversely isotropic spherical segments with tapered thickness, different radii of curvature and biomechanical properties. Cornea is modeled as multilayer shell. The simulated eye shell is loaded with internal pressure. Mathematical models of three different laser vision correction surgeries: small incision lenticule extraction (SMILE), laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK), are developed in the engineering simulation software ANSYS Inc. The diameter and thickness of the lenticular in SMILE, the diameter of the ablation zone and the maximum thickness (depth) of the corneal ablation in LASIK and PRK define optical surgery areas and are considered as comparable parameters. Finite element simulation shows that after LASIK vision correction the apex of the cornea has a greater displacement and the stress increase greater in the stroma than after SMILE and PRK.

Weightlifting exercises are coordinately complex, speed and power based movements, which simultaneously combine the maximum muscle work with different contraction types and limit the result with special functional features of the neuromuscular apparatus. According to modern views, indicators of biomechanics of the motor act and electromyographic characteristics of leading muscles during performance of the act show different aspects of the same process of contraction and can be used as criteria for an evaluation of muscle efforts and the functional state of the neuromuscular apparatus. The objective of this study is to identify special features of dynamics of muscle electric activity parameters and maximum power characteristics in different phases of weightlifting snatch. The study involved 35 male elite weightlifters with the Master of Sports qualification. The study was conducted with the BTS Motion System (made by BTS Bioengineering, Italy). A computer program was developed to analyze the technique of the snatch (the certificate RU 2020660142 from 28.08.2020). The study included registration and following analysis of biomechanical (dynamic, kinematic) and electromyographic indicators during performance of the snatch by athletes with 80% intensity of the maximum weight directly during the training session. Features of dynamics of muscles’ electric activity parameters and maximum power characteristics, which are significantly changing in different phases of performance of the snatch, were revealed in the study. Pull phases are characterized by the increase of muscle tension, muscle work in the concentric dynamic contraction. Snatch phases are characterized by the maximum power of muscle tension and the speed of its dynamics according to both biomechanical features and electrical processes in muscles: a maximum tension and high frequency of impulsion of motor units of extensor muscles were noted. Squat phases are characterized by the decrease of muscle tension and speed of its changing, muscle work in the combined type of contraction, including eccentric and static types. High, but not maximum indicators of power and tension of muscles characterize phases of standing-up. It was revealed that the eccentric muscle contraption, according to EMG indicators, is manifested in the decrease of both amplitude and frequency characteristics. The concluded study allowed to present data characterizing biomechanics of the motor act and special physiological features of leading muscles’ work of elite weightlifters during performance of the exercise. Power and electromyographic parameters in various types of muscle work in different phases of the snatch were determined.

Severe non-specific pneumonia is complicated by airway obstruction, which is caused by swelling of the mucous membranes of the airways and blockage of their mucus, pus and thick sputum with streaks of blood. A particularly significant decrease in airiness occurs in the peripheral regions of the lungs. This is why the air introduced through the upper respiratory tract does not reach the alveoli, primarily in the peripheral areas of the lungs. Under these conditions, traditional ventilation of the lungs provides a back-and-forth movement of air only in the trachea, large and small bronchi, since only these areas of the respiratory tract remain unclogged by mucus and pus. But these areas of the respiratory tract do not provide effective oxygenation of the patient's blood. Therefore, conventional artificial lung ventilation (ventilator) cannot normalize the biomechanics of respiration until the elimination of respiratory obstruction. Therefore, in the case of respiratory biomechanics depression caused by respiratory obstruction, it is currently customary to oxygenate blood by extrapulmonary route - using extracorporeal membrane oxygenation (ECMO). However, ECMO is a very dangerous and poorly available method of treatment. Therefore, to save the lives of patients with severe hypoxia, it is proposed to urgently restore pulmonary blood oxygenation by oxygenating the lungs by injecting a solution of pus solvent into the peripheral areas of the lungs. At the same time, intra-pulmonary injection of an alkaline peroxide solvent of pus provides an immediate appearance of oxygen gas in the peripheral respiratory tract, since pus and blood veins contain the enzyme catalase, which immediately decomposes hydrogen peroxide into oxygen gas and water. In this case, mucus, pus and sputum with streaks of blood immediately turn into oxygen foam, which is easily removed through the upper respiratory tract to the outside.

Restoration of the locomotor function is one of the most essential problems of medicine. This problem becomes especially essential, when we deal with those children, who can’t walk from their birth. Term “abilitation” is used just in relation to such children, what means not retraining children the right stereotype of walking, but appearance of this skill and its further adequate development. Nowadays, more and more specialists, who occupy themselves with abilitation of children of the early age, realize necessity of the instrumental estimation of the locomotor function. This phenomenon is connected with the fact, that in contrast with the score system of estimation, instrumental estimation of walking is maximally concrete and exact, and complex investigation of the biomechanical and innervative structure of walking gives complete idea of the locomotor disturbances of the child. Authors of this article investigated biomechanical and innervative structure of walking of 4 healthy children at the age of 2-2.5 years. On the basis of these investigations, it has been revealed, that the following peculiarities of walking are characteristic of children at the age of 2: remarkable diminution of the mean walking velocity, increase of cadence and shortening of the step length, essential transformation of the temporal structure of walking (growth of duration of the stance and double-support phase and decrease of duration of the swing phase), flexion position of the lower extremities, displacement of all extreme values of the angular displacements to the right along the temporal axis, considerable prolongation of the maximums of activity, absence of the second maximum of activity in a number of muscles, severe disturbances in the resonance properties of the lower extremities. All these peculiarities point out to the immaturity of the process of locomotion in children at the age of 2. The received data are necessary first of all as the standard ones, because walking parameters of children with the locomotor disorders of the early age must be compared with the corresponding parameters of the healthy children of the same age.