The purpose of the work was to develop a model of maintaining balance in accordance with the parameters of the human body, which ensures the function of maintaining the body's balance in space. The key indicator of stable balance is the center of mass (CM) of the human body. The stability of the posture is ensured by the projection of the center of mass (CM) within the support area. The article describes two models that assess the displacement of the CM projection relative to the support area. The principle of operation of the models is based on pendulum motion in the sagittal plane (forward-backward movements) and the frontal plane (lateral movements). The model includes a comprehensive visualization of the CM projection on the support area in real time, as well as a quantitative assessment of stability by counting the percentage of time spent in the support area. The model provides a more comprehensive understanding of the mechanisms involved in maintaining equilibrium.

Keywords: balance maintenance mechanisms, modeling, biomechanics, and the center of mass

The article is devoted to the analysis of methodological approaches to the definition and assessment of the psychofunctional state of a person. In connection with the need to improve the reliability of human-machine systems, the study of the psychofunctional state of a person controlling a dynamic object is of scientific interest, since to create reliable human-machine systems it is necessary to take into account the reliability factors of technical means and the human factor as well. The analysis of methodological approaches showed that to solve problems dedicated to increasing the reliability of "human-machine" systems, it is advisable to use a systems approach that considers a person not as an independent subject, but as an element of the system. The systems approach has a broad methodological base, allows us to study the psychofunctional state of a person in dynamics.

Keywords: psychofunctional state, functional state, systems approach, energy approach, behavioral approach, phenomenological approach, structural-integrative approach, electrophysiological methods, control of a dynamic object

The article presents an analysis of the problems of diagnosis and restoration of the human respiratory system after diseases, including COVID-19. The review of analogues of small-sized spirometers is carried out. On the basis of which an individual small-sized device has been developed for effective training of the respiratory system. The functional scheme of the pneumatic trainer is described and the main simulator-game scenarios for achieving a therapeutic effect are analyzed.

Keywords: respiratory system, COVID-19, pneumatic trainer, portable device, pressure sensor, MEMS technology