Anastasiya Vladimirovna Kovaleva

Background. The introduction of software and hardware systems (SHS) with electromyographic (EMG) biofeedback into rehabilitation for the control of real physical objects is hindered by insufficient development of methodological support. Unlike screen-based and virtual trainers, such systems form a closed sensorimotor loop involving proprioceptive feedback, which requires special methodological approaches. In this regard, the study of the physiological support for the use of such systems in healthy volunteers, with a description of both subjective assessment of difficulty and objective performance characteristics, is relevant. Aim. To study the individual characteristics of motor control when using an SHS with EMG biofeedback for controlling a real physical object in healthy subjects, using objective performance indicators of exercise execution based on video analysis and subjective assessment of workload. Methods. The pilot observational cross-sectional study involved 26 subjects aged 18–35 years (15 women; 11 men) without neurological diseases or motor impairments. An SHS «BIOMOD» (Neuro MD LLC, Russia) with two Callibri myographic sensors and Android-based software was used. A modified radio-controlled car was controlled via EMG signals during contraction/relaxation of forearm muscles. Participants in two series of exercises (push/pull) controlled the movement of the car in two postural positions (sitting/standing) within a marked 5 m track. Objective assessment of the exercises was performed using video recordings. Subjective workload assessment was evaluated after completing the tasks using the NASA-TLX questionnaire (Russian-language adaptation). Results. In the sitting position, men showed a tendency toward shorter exercise completion time and lower error frequency; in the standing position, these sex differences were leveled out. The integrative indicator of control quality was characterized by relative stability: no statistically significant differences were found between groups. Analysis of subjective workload on the NASA-TLX scale showed that the most pronounced component was «Time Pressure», with moderate values of mental demand, physical effort, and a relatively low level of frustration. Correlation analysis revealed statistically significant relationships between individual NASA-TLX scales and objective control indicators in men; no such associations were found in women. The obtained data indicate the presence of sex differences in the structure of relationships between subjective perception of workload and the effectiveness of controlling a real object via EMG. Conclusion. The characteristics of motor control when controlling a real object via EMG in healthy volunteers were studied. The obtained data may serve as a basis for a methodology for using such devices in rehabilitation practice.

A major barrier to developing adaptive human–machine systems is the lack of interpretable physiological markers for characterizing physiological responses associated with changes in task demands. The aim of this study was to evaluate the feasibility of machine-learning classification of physiological responses during simple and complex task stages and two standardized task-demand transitions—baseline/rest-to-simple and simple-to-complex—in cognitive and motor-cognitive protocols. Sixty-nine healthy volunteers completed cognitive tasks involving normal and 180° inverted-text reading and motor-cognitive tasks involving simple and complex movement sequences performed with the non-dominant hand. Each protocol comprised a 1 min baseline followed by three consecutive blocks, each including a 1 min simple task, a 1 min complex task, and a 1 min rest period. Photoplethysmography (PPG), skin conductance (SC), and abdominal respiration were recorded continuously. Pulse-to-pulse (PP) intervals were extracted from the PPG signal, and conventional heart rate variability (HRV) indices, including mean RR interval, HR range, SDNN, RMSSD, Total Power, and SD2, were calculated in Kubios HRV from the PPG-derived interval series. Logistic Regression, Random Forest, and Support Vector Machine models were trained using either absolute physiological values or dynamic features (Δ%) calculated for the baseline/rest-to-simple and simple-to-complex transitions. Models based on dynamic features consistently demonstrated higher classification performance than those based on absolute physiological values. For the motor-cognitive protocol, Random Forest achieved an accuracy of 0.726 and a ROC-AUC of 0.730, whereas for the cognitive protocol, Support Vector Machine achieved an accuracy of 0.655 and a ROC-AUC of 0.722 on the held-out participant-level test set. The most informative features included mean RR interval (derived from PPG), Total Power, RMSSD, SDNN, SD2, and HR range in both protocols. Comparable feature-importance patterns across protocols suggest overlap in the physiological variables contributing to classification under the standardized experimental conditions. These findings are limited to the fixed transition sequence used in the present study and require confirmation in randomized or counterbalanced designs.

The Cambridge Neuropsychological Test Automated Battery (CANTAB) is a widely used tool for cognitive assessment, yet its psychometric properties and normative standards for schoolchildren in non-English speaking countries, including Russia, remain understudied. This study established test-retest reliability and age-stratified normative data for CANTAB in a Russian schoolchildren sample (N = 689, aged 7-17). Reliability analyses on a subsample (n = 101) showed good-to-excellent reliability for Spatial Working Memory (SWM errors, ICC = 0.72) and Reaction Time (RTI) accuracy, but poorer reliability for Stockings of Cambridge (SOC) planning measures. Analyses revealed minimal gender effects but robust age-related improvements across most cognitive domains, particularly in visuospatial working memory (SWM), recognition memory (SRM), and processing speed (RTI), reflecting the maturation of executive functions. These age-related differences align with international findings. This work provides the first comprehensive reliability and normative data for CANTAB in Russian schoolchildren. It validates the use of specific, reliable parameters (e.g. SWM errors) for clinical and research applications and supplies essential age-stratified norms for accurate cognitive assessment in this population.

Relevance. The association between competitive anxiety and heart rate variability (HRV) remains inconsistent, especially when athletes are evaluated outside the immediate pre-competition period. Objective. To examine relationships between competitive anxiety and autonomic, respiratory, and sensorimotor regulation in martial arts athletes during a non-competitive training phase. Methods. Forty athletes (aged 16–27) who practice karate, kyokushin, wushu, or taekwondo were assessed during regular training sessions. Competitive anxiety was measured using the Competitive State Anxiety Inventory-2 (CSAI-2). Resting photoplethysmography (5-minutes, seated) was recorded to calculate linear and nonlinear heart rate variability (HRV) indices, as well as respiratory parameters. Sensorimotor performance was assessed using a battery of visual-motor tasks. All variables were standardized using z-scores. Correlation analysis, k-means clustering, and PERMANOVA were used for analysis. Results. No significant correlations were found between anxiety subscales and autonomic or sensorimotor indicators. Cluster analysis identified two psychological profiles: a group with higher anxiety and lower confidence, and a more adaptive group with lower anxiety and higher confidence. Although univariate differences did not reach statistical significance, the group with higher anxiety showed consistent trends towards lower vagal activity (RMSSD, pNN50), reduced abdominal respiratory amplitude, reduced autonomic complexity, and increased variability in choice reaction time. Multivariate analysis suggested a trend towards differentiation of integrated psychophysiological profiles (p=0.08). Conclusion. In non-competitive conditions, anxiety was not related to individual physiological markers, but rather reflected in integrated, multivariate configurations. These findings emphasize the significance of multidimensional approaches in sports psychophysiology.

Heart rate variability (HRV) is a sensitive marker of autonomic regulation. This study examined adolescents in the long‐term postoperative period after early surgical correction of aortic coarctation (CoA) compared with age‐matched healthy peers. Seventy adolescents (35 CoA, 35 controls; 12–17 years) underwent 5‐min resting ECG and respiratory monitoring. HRV was analyzed using time domain, frequency domain, and nonlinear methods; respiratory rate was included as a covariate in ANCOVA models. Adolescents with repaired CoA showed lower time domain indices (SDNN, RMSSD, pNN50; all p < 0.01), reduced total spectral power ( p = 0.002), and higher VLF ( p < 0.001). Group differences in SDNN, RMSSD, and the LF/HF remained significant after adjustment for respiratory rate, indicating that autonomic alterations were not explained by breathing patterns. Nonlinear analysis revealed reduced Poincaré plot parameters (SD1, SD2; p < 0.01) and higher fractal scaling (DFA Alpha2; p < 0.001) in the CoA group, whereas entropy measures and DFA Alpha1 did not differ. These findings demonstrate persistent and selective alterations in autonomic regulation during adolescence despite anatomically successful repair. The coexistence of altered and preserved HRV features suggests domain specific reorganization rather than uniform loss of complexity. Nonlinear HRV indices may improve long term monitoring and help guide individualized rehabilitation.

Heart Rate Variability (HRV) biofeedback could be considered as a tool to help athletes to optimize their performance. This study aimed to examine the effects of a one-week HRV biofeedback (HRV-BFB) program on physiological indices, sensorimotor functions, and kata performance in Eastern martial arts athletes. Forty high-level martial arts athletes (karate, wushu, taekwondo, kyokushinkai) aged 17–27 years were divided into two groups: a control group (n = 20) and a biofeedback group (BFB, n = 20). Athletes from both groups underwent assessment of sensorimotor functions and the technical quality of their kata routines. The primary outcome was the expert-rated kata performance score. All routines were video-recorded and independently rated by three certified judges. The BFB group completed a hybrid HRV-BFB program consisting of supervised resonance-frequency breathing sessions in the laboratory and one week of home-based practice. During supervised sessions, athletes performed slow abdominal-paced breathing (6 breaths/min). At home, they practiced the same breathing pattern twice daily for one week (5 min per session, smartphone-guided). Nonparametric tests were used because several variables deviated from normality, and the sample size per group was limited (n = 20). After completing the HRV-BFB training, movement oscillation frequency improved significantly, reflected by lower movement oscillation frequency (p = 0.0009, r = 0.79), faster choice reaction time at a tendency level (p = 0.0793, r = 0.39), and an increase in blood volume pulse (BVP) (p = 0.037, r = 0.48) in BFB group compared to control group. Following BFB training, the judges’ scores did not change in the control group, while a significant increase was observed in the BFB group (p = 0.038, r = 0.44), indicating a positive effect of BFB training on kata performance. Regular HRV-BFB training emphasizing slow-paced abdominal breathing may enhance autonomic regulation, fine motor control, and improve the technical execution of kata routines in athletes.

The analysis of literature data has studied the pathogenetic mechanisms of heart rate variability (HRV) disorders in patients with congenital heart defects (CHD). The findings demonstrate that HRV alterations begin in utero and are determined by both the type of defect and associated hemodynamic disturbances. In the preoperative period, HRV is influenced by the severity of the defect, patient age at the time of surgical intervention, psychological state, and genetic factors. Surgical correction, particularly under cardiopulmonary bypass conditions, leads to further reduction in HRV due to autonomic nerve fiber damage, systemic inflammatory response, and scar tissue formation. The type of surgery significantly affects the degree of impairment, with more pronounced changes observed in open surgical interventions compared to endovascular methods. In the postoperative period, the pattern of HRV recovery depends on the type of correction and the initial defect. Notably, even in the long-term postoperative period, autonomic regulation imbalance often persists with predominant sympathetic influences. This may be attributed to both residual structural changes and long-term consequences of surgical damage to autonomic innervation. Understanding the mechanisms of HRV disorders is crucial for developing strategies to improve long-term outcomes in CHD patients; however, further research is needed to clarify the role of specific pathogenetic mechanisms and find ways to correct autonomic dysfunction.

This study determined the impact of biofeedback training on the psychophysiological profile and technical actions of athletes.

Introduction. The rhythm of the heart (heart rate, HR) is closely related to the rhythm of breathing. The phenomenon of respiratory sinus arrhythmia (an increase in heart rate during inhalation and a decrease during exhalation) is well known. Cardiorespiratory interactions and synchronization of these two signals are evaluated differently in the literature. The purpose of this work was to propose and test an approach to assess cardiorespiratory synchronization – the calculation of the cross-correlation coefficient between heart rate and respiration curve, for a more objective characterization of an athlete’s bodily states. Methods. A photoplethysmogram and respiration were recorded in 45 healthy athletes (18-25 years old) in three situations: rest, paced breathing at 6 times per minute (resonant frequency) and the performance of a sensorimotor task (tapping with the rhythmic metronome sounds and then reproducing a given rhythm from memory). For the HR and respiration curves, filtering and smoothing algorithms using the Savitsky-Goley method were applied sequentially, and then the cross-correlation coefficient between the two curves was calculated. The spectral parameters of heart rate variability (LF and HF) were also obtained, since during spontaneous breathing its contribution to the HR is reflected in HF band, and when breathing at a resonant frequency, a peak occurs at a frequency of 0.1 Hz in the LF band. Results. The cross-correlation coefficient, as well as the peak of HR spectral power at 0.1 Hz, increases significantly when breathing at a resonant frequency. The relationship between these indicators is most accurately described not by a linear, but by a logarithmic dependence. When performing a sensorimotor task, the so-called respiratory waves in the heart rhythm spectrum (HF) do not change from rest to tapping by a metronome and then to holding the rhythm by memory. At the same time, the cross-correlation coefficient demonstrates significant changes between these situations. In addition, a significant correlation was found between the change in the cross-correlation coefficient and the stability of rhythm maintenance (from memory): an increase in the cardiorespiratory synchronization leads to a decrease in motor rhythm stability. Conclusion. Assessment of cardiorespiratory synchronization due to the peculiarities of both signals (changes in heart rate and respiratory phases) requires preliminary preparation of data arrays: filtering and smoothing the stepped curve of heart rate dynamics. The calculation of the cross-correlation coefficient can be used to assess cardiorespiratory synchronization in real time and is likely to be applicable in short time fragments to assess emotional reactions and other short-term fluctuations in psychophysiological conditions, where the classical method of assessing changes in heart rhythm in the frequency or time domains is not applicable.

Показатели вариабельности ритма сердца (ВРС) являются простыми, неинвазивными, объективными чувствительными индикаторами изменений функционального состояния человека. В ряде исследований отмечается, что дети с врожденными пороками сердца (ВПС), как правило, демонстрируют более низкие показатели общей ВРС по сравнению со здоровыми людьми, что, вероятно, связано с нарушениями в регуляции сердечного ритма, вызванными структурными изменениями в сердце. Цель. Сравнение показателей ВРС в покое, вычисленных при помощи различных видов анализа ритма сердца, у условно здоровых детей и детей с ВПС в отдаленном послеоперационном периоде. Материалы и методы. 70 детей от 12 до 17 лет (Me=14). Из них 26 человек (11 девочек) – после радикальной коррекции коарктации аорты в отдаленном послеоперационном периоде, (группа ВПС) и 44 (30 девочек) условно здоровых ребенка (группа: Норма). Результаты. Выявлены значимо более низкие значения параметров ВРС: SDNN, рNN50, триангулярного индекса и суммарной мощности спектра в группе детей с ВПС по сравнению с условно здоровыми детьми. Также в группе детей с ВПС было зарегистрировано значимое увеличение VLF и аппроксимированной энтропии. Заключение. Сниженная ВРС у детей с ВПС в отдаленном послеоперационном периоде может свидетельствовать о нарушениях вегетативной регуляции сердца, а рост сложности сердечного ритма, по-видимому, отражает необходимость формирования более сложных адаптационных механизмов у таких детей. Heart rate variability (HRV) is simple, non-invasive, objective, sensitive indicator of changes in a person’s functional state. A number of studies have noted that children with congenital heart defects (CHD) tend to have lower overall HRV scores compared to healthy controls, which is likely due to disturbances in heart rate regulation caused by structural changes in the heart. Aim. Comparison of HRV indicators at rest, calculated using various types of heart rhythm analysis, in apparently healthy children and children with CHD in the long-term postoperative period. Materials and methods. Seventy (70) children aged 12 to 17 years (Me=14): children from the first group (n = 26, 11 girls) were after radical correction of aortic coarctation in the late postoperative period; children from the second group (n = 44, 30 girls) were apparently healthy children. Results. Significantly lower values of HRV parameters were revealed: SDNN, pNN50, triangular index and total spectral power in the group of children with CHD compared to apparently healthy children. Also, in the group of children with CHD, a significant increase in VLF and approximate entropy were recorded. Conclusion. Reduced HRV in children with congenital heart disease in the late postoperative period may indicate disturbances in the autonomic regulation of the heart, and an increase in the complexity of the heart rhythm apparently reflects the need for the formation of more complex adaptation mechanisms in such children. congenital heart defects; heart rate variability; autonomic regulation; coarctation