Tatyana Baltina

Background: The functional state of skeletal muscle is governed by the interaction of mechanical loading, neural control, and proprioceptive afferentation. Nonetheless, the relative impact of the disruption of these components on muscle function and structure remains insufficiently characterized. Methods: In the present study, we investigated three rat models of muscle disuse and two combined models: hindlimb unloading (n = 40), denervation (D, n = 40), tenotomy (T, n = 40), and the combinations HU + D (n = 8) and HU + T (n = 8), with the cumulative effects evaluated at 7, 14, 35, and 50 days. Functional changes were assessed using electrophysiological methods (M-response recording), and structural changes were evaluated by histological, immunohistochemical, and immunofluorescence analysis. Results: The disuse models elicited significantly distinct trajectories of muscle maladaptation. Hindlimb unloading induced coordinated functional and structural remodeling; denervation provoked early functional decline followed by structural changes; tenotomy largely preserved functional activity despite progressive structural remodeling. The combination of denervation with unloading partially attenuated the negative effects, whereas the combination of unloading and tenotomy led to functional enhancement in some cases. These findings provide insight into the degree of convergence, additivity, and synergy of the disruption of regulatory components and indicate that reduced electrical activity is not invariably associated with synchronous structural degradation, revealing a functional–structural dissociation wherein functional status fails to reflect structural integrity. Conclusions: This observation suggests a previously unrecognized mechanism of maladaptation, which diverges from classical atrophy, broadening our understanding of muscle disuse physiology and offering new perspectives for the development of preventive and therapeutic strategies against atrophic processes.

Concrete structures exposed to biological attack undergo degradation caused by organic acids produced by microorganisms. To improve the resistance of cementitious materials, this study applied mechanical activation of Portland cement using a vortex layer device. Porosity and compressive strength of control and mechanically activated hardened cement paste (HCP) specimens were evaluated after 0, 14, and 28 days of exposure to a model acidic environment (pH 3, a mixture of carboxylic acids). Spatiotemporal heterogeneity of degradation in control and activated HCP was assessed for the first time by 4D X-ray computed tomography, which tracked individual pores across the same time points and revealed degradation patterns inaccessible to bulk measurements. Mechanical activation was found to increase the initial compressive strength by 33% (59.3 MPa vs. 44.5 MPa). After 28 days, the activated specimens retained 75% of their initial strength, compared with 62% for the control ones. Despite higher initial porosity (1.5% vs. 1%), the mechanically activated specimens exhibited lower volumetric loss (27% vs. 56%) and maintained spatial stability of the pore framework. These findings support the potential of this approach for structures operating under microbiological corrosion conditions.

Postural control is a multilevel adaptive system that stabilizes the body in space through dynamic sensory rebalancing and predictive neuromotor regulation. This review synthesizes current data on the neural mechanisms of balance maintenance, individual strategies for integrating multisensory information, and the role of immersive virtual reality as a controlled experimental and neuromodulation platform, synthesising evidence from 73 studies across neuroscience, cognitive psychology, and VR-based rehabilitation. Particular attention is paid to the cognitive style of “field dependence/independence”, which reflects stable preferences for the dominance of visual or vestibular-proprioceptive signals and consistently predicts the selection of postural strategies. We show that traditional averaged models ignore interpersonal variability, whereas immersive VR allows for the parametric induction of sensory conflicts, quantitative assessment of sensory dependence profiles, and facilitates the study of adaptive reorganization at the cortical, brainstem, and spinal levels. The review substantiates the need to move from standardized protocols to personalized approaches in diagnostics and neurorehabilitation that consider individual patterns of input rebalancing. The integration of behavioural metrics with neurophysiological markers in a VR environment provides a foundation for developing predictive balance models and targeted training interventions. However, the translational application of VR-based approaches requires careful consideration of methodological limitations, including cybersickness, hardware latency, and ecological validity, to ensure robust and generalisable outcomes.

Individual differences in cognitive style—field-dependence/field-independence (FD/FI)—are thought to influence how sensory information is integrated for postural control. This study examined the impact of FD/FI on postural control during different sensory conditions. Forty-one healthy young adults were classified as FD (n = 18) or FI (n = 23) using the Gottschaldt Figures trial. Postural stability was assessed using a force platform. Participants completed a protocol of 60-s standing trials under different sensory conditions: eyes open (EO) or eyes closed (EC), on a hard (HS) or soft (SS) surface, and during exposure to a virtual reality (VR). Primary outcome measures included the ellipse area (ELLS), total path length (TL(y)) and average linear velocity (ALV(y)) of the center of pressure (CoP) in the sagittal plane and mean angular velocity (MAV) of CoP. Visual deprivation, proprioceptive disruption, and VR exposure increased postural sway in all participants, but with distinct group differences. With EC on HS, FI individuals demonstrated lower TL(y), ELLS, and ALV(y) compared to FD individuals, indicating more effective postural control in FI. A similar FI advantage was observed during standing on a SS with EO. VR exposure on HS destabilized FD participants, resulting in greater increases in postural sway parameters than in the FI group. FD individuals showed a faster return to baseline stability after the VR on an SS trial, whereas FI individuals showed a transient degradation in postural control immediately after VR exposure. These findings demonstrate that cognitive style predicts an individual’s strategy for maintaining and recovering balance under sensory conflict.

This study examined the effects of different sensory stimuli on postural control in healthy volunteers. The experimental conditions included standing with the eyes closed, standing on a compliant surface, transcutaneous electrical stimulation of the cervical spinal cord (tSCS) at 5 and 30 Hz and at different intensities (subthreshold and suprathreshold), and exposure to virtual reality (VR). Time–frequency analysis of stabilograms revealed increased high-frequency postural sway during standing with the eyes closed and on a compliant surface, indicating a greater contribution of somatosensory and proprioceptive inputs to balance control. tSCS at both frequencies tended to reduce sway amplitude irrespective of stimulation intensity. Viewing video sequences through a VR headset increased the statokinesiogram area and mean linear velocity, indicating postural instability. These findings indicate that changes in afferent input affect postural control mechanisms. tSCS appears to have a compensatory effect by promoting redistribution of the functional load across different levels of balance regulation, whereas VR enhances destabilizing effects when proprioceptive input is less reliable.

Представлен метод кластеризации данных видеофиксации, направленный на оценку постуральной устойчивости с использованием персистентных гомологий – современного подхода топологического анализа, обладающего высокой устойчивостью к шуму и вариабельности динамичных видеоданных. Исследование базируется на экспериментальных данных видеозаписей испытуемых при выполнении теста Ромберга с открытыми и закрытыми глазами, параллельно со стабилометрическим тестированием. Разработанный комплекс методов включает автоматическую сегментацию человеческой фигуры с применением предобученной модели Segment Anything Model, выделение ключевых анатомических точек и расчет угловых параметров тела во временной последовательности. Полученные временные ряды углов выполняются с помощью фильтрации Морса, обеспечивающей отслеживание топологических изменений, и представляются в виде диаграмм персистентности. Далее для анализа сходства и различий между диаграммами используется метрика Вассерштейна. Кластеризация происходит с помощью алгоритма k-средних, что позволяет выявить группы участников и их индивидуальные стратегии компенсации дисбаланса. Результаты демонстрируют, что топологический анализ видеоданных дает более глубокое и детализированное разделение испытуемых по паттернам постуральной устойчивости по сравнению с классической стабилометрией. Методы выявляют различные стратегии стабилизации равновесия – от изменений углов туловища до контроля головы и рук, что способствует качественному пониманию механизмов поддержания баланса. Авторы подчеркивают важность учета оптических искажений для повышения точности анализа и подтверждают высокую воспроизводимость и информативность предложенного подхода, открывающего перспективы для персонализированной диагностики и реабилитации пациентов.

This paper presents a method for clustering video data aimed at assessing postural stability using persistent homologies – a modern approach in topological data analysis characterized by high robustness to noise and variability in dynamic video data. The study is based on experimental video recordings of subjects performing the Romberg test with eyes open and closed, conducted in parallel with stabilometric testing. The de-veloped methodological framework includes automatic segmentation of the human figure utilizing a pretrained Segment Anything Model, extraction of key anatomical points, and calculation of angular body parameters over time sequences. The resulting time series of angles are analyzed using Morse filtering to track topological changes and are repre-sented as persistence diagrams. Subsequently, the Wasserstein metric is employed to analyze similarities and differences between the diagrams. Clustering is performed using the k-means algorithm, enabling identification of participant groups and their individual strategies for balance compensation. The results demonstrate that topological analysis of video data provides a deeper and more detailed stratification of subjects according to postural stability patterns compared to classical stabilometry. The methods reveal various strategies for equilibrium stabilization – ranging from changes in torso angles to control of the head and hands – facilitating a qualitative understanding of balance maintenance mechanisms. The authors emphasize the importance of accounting for optical distortions to enhance analysis accuracy and confirm the high reproducibility and informativeness of the proposed approach, opening prospects for personalized diagnosis and rehabili-tation of patients.

Modern methods of human posture and movement assessment used in medical practice for diagnosing and monitoring the condition of patients with musculoskeletal disorders are discussed in the article. The advantages and disadvantages of traditional methods, such as goniometry and body topography, as well as modern technologies, including 3D video analysis systems, are described. The authors propose a new ap-proach based on the use of digital video cameras to create standardized video protocols for patient screening. This methodology provides accessibility, objectivity, and the pos-sibility of application in the routine practice of doctors from various specialties, such as neurology, orthopedics, rehabilitation, and sports medicine. The aim of the research is to develop a technology for assessing static coordination and detecting body asymmetry in patients. The developed software and hardware system provides automated pro-cessing of video recordings to analyze human posture symmetry. This process begins with marking the first frame and concludes with the calculation of numerical characteris-tics based on segmentation and object tracking. The program utilizes a pre-trained neural model to segment images and identify control points such as the center of mass, key joints, and body lines. The program allows to save angles, area and deviations at each moment in time. The processing results are then converted into numerical tables and visualized as plots. The software is designed to generate video protocols, facilitating dynamic assessment of patients in ambulatory care settings. Its application revealed pos-itive results: patients were divided into three significant groups, which correlates with common musculoskeletal syndromes. Specifically, the identified groups correspond to comorbidities in the craniocervical-shoulder and lumbar-femoral regions, as well as a combination of temporomandibular joint dysfunction with psychological affective disor-ders. These findings highlight the potential of digital visual assessment for accelerating patient diagnosis and identifying muscle imbalances caused by modern sedentary life-styles.

Определение механических параметров выступает одним из актуальных направлений при расчёте элементов негомогенных сред. Необходимость построения численных моделей в первую очередь обусловливается развитием современных подходов к воссозданию мате риалов различной композитной структуры. Применение расчётных моделей в клинической практике также позволяет исследовать прочностные показатели объектов биологического происхождения, к особенностям которых можно отнести уникальность структурного распределения материала. Наибольшее распространение в этом случае получили подходы, основанные на применении данных с изображений. В рамках данной работы представлен метод построения матрицы упругих постоянных на основе данных цифрового двойника. В ходе работы выполняется построение изображений с заданной структурой материала, а также извлечение данных из снимков компьютерной томографии натурных образцов. Усреднение механических показателей выполнялось на основе метода конечных элементов для области квадратной или кубической геометрии, определяющей элементарную ячейку. Проведение расчётов предложенным методом показало сходимость метода с данными аналитического расчёта на примере решения тестовых задач, а также определило качественное соответствие результатов особенностям структурного распределения материала в натурных образцах. Представленный метод гомогенизации позволяет определять упругие характеристики элемента среды с учётом неоднородных свойств образующего материалаx.

The determination of mechanical parameters is one of the relevant directions in the calculation of inhomogeneous media elements. The need to build numerical models is primarily due to the development of modern approaches to the reconstruction of materials of various composite structures. The use of computational models in clinical practice also makes it possible to study the strength characteristics of objects of biological origin, the features of which include the uniqueness of the material structural distribution. The most widespread approaches in this case are based on the use of image data. Within the framework of this work, a method for constructing an elasticity matrix based on digital twin data is presented. During the work, images with a given material structure are constructed, as well as data extraction from CT scans of full-scale samples. The averaging of mechanical parameters was performed on the basis of the finite element method for the area of square or cubic geometry defining the unit cell. The calculations performed by the proposed method showed the convergence of the method with the analytical calculation data on the example of solving test problems, and also determined the qualitative correspondence of the results to the features of the structural distribution of the material in full-scale samples. The presented homogenization method makes it possible to determine the elastic characteristics of a medium element, taking into account the inhomogeneous properties of the forming material.