Brave, Yan Robertovich

Pozdnyakova A.E., Savon G.K., Lev L.P., Baltin M.E., Bravyy Y.R., Onishchenko D.A.

Bravyy Y., Onishchenko D., Baltin M.

A methodology for determining maximal anaerobic power and optimal pedaling cadence in sprint cyclists is presented, which is a key factor in track cycling performance. The study examines the impact of pedaling cadence on performance and emphasizes the importance of gear ratio selection for sprints. The research involved 10 professional sprint cyclists aged 15–19 years. Participants performed three maximal sprints with increasing resistance on a cycle ergometer equipped with an electronic braking system and sensors for precise measurement of left and right leg forces and pedaling cadence. This setup enabled the recording of force–cadence and power–cadence relationships. Data analysis was conducted using linear and quadratic regressions. Morphological assessments were conducted, including calculations of fat and muscle mass percentages using anthropometric methods. The study revealed significant interindividual differences in key performance parameters. Maximal power was achieved at an individual-specific optimal cadence, which varied by 20–40 %. The results validate the effec-tiveness of the proposed methodology for tailoring training processes to individual needs. The power–cadence relationship facilitates the determination of the optimal cadence at which max-imal power is attained. The findings underscore that adjusting the gear ratio to achieve the optimal pedaling cadence during sprints enables maximum performance and optimizes effort distribution during critical moments of track competition. The methodology provides tools for analyzing fatigue and other factors affecting performance. It enables precise evaluation of track cyclists' physical capabilities, optimizes training plans, enhances outcomes, and supports personalized tactical strategies, making it valuable for coaches and researchers in biomechanics and sports physiology.

Rytova A., Petrov M., Simakov S., Dubodelov A., Dyachenko D., Bravyy Y., Onischenko D.

This article discusses the development and implementation of an algorithm for the automatic analysis of schoolchildren's posture using video recordings. The study aims to create an effective tool for detecting posture deviations through biomechanical features, such as shoulder and head tilt angles, distances between anatomical points, and other parameters. The algorithm involves the use of the BlazePose neural network for extracting body key points, identifying irrelevant frames, and analyzing time-series data. The research methodology is based on the application of computer vision techniques and biomechanical feature analysis, followed by data visualization and automated report generation. The results demonstrate that the proposed algorithm effectively identifies posture deviations, providing visual feedback for the prevention and correction of potential disorders. The automation of the process enables large-scale monitoring of schoolchildren's posture and contributes to the prevention of chronic musculoskeletal disorders.

Iskarevskii G.V., Pekonidi A.A., Beknazarova A.M., Pozdnyakova A.E., Onishchenko D.A., Kirsanov A.S., Baltin M.E., Bravyy Y.R.

Cherepanova A.V., Bravy Y.R., Karabelsky A.V., Kotova M.M., Kolesnikova T.O., Kalueff A.V.

Monoamine transporters (MATs) are responsible for the reuptake of dopamine, serotonin, and norepinephrine, modulating concentrations of these essential brain neurotransmitters and thus regulating behavior, mood, and cognitive functions. Studying the role of various genes in complex physiological processes is a promising area of neurobiology and sport physiology. Here, we summarize mounting evidence linking specific genetic variants of MAT genes to various aspects of sport performance. For example, the 10-repeat allele of the dopamine transporter gene (DAT), the L-allele of the serotonin transporter gene (SERT), and the single nucleotide polymorphism rs1805065 of the norepinephrine transporter gene (NET) appear to correlate with a higher athletic performance due to stress resistance, as well as the maintenance of motivation and cognitive behavioral competencies, i.e. qualities required to achieve sporting success. Thus, physiological performance in various sports may be partially genetically determined and controlled by the variability in the MAT genes.

Ahmetov I., Kulemin N., Popov D., Naumov V., Akimov E., Bravy Y., Egorova E., Galeeva A., Generozov E., Kostryukova E., Larin A., Mustafina L., Ospanova E., Pavlenko A., Starnes L., et. al.

Bravyi Y.R., Bersenev E.Y., Makarov V.A., Tarasova O.S., Borovik A.S., Vinogradova O.L.

The effect of strength training on muscle pressor reflex responses was investigated. Ten young, healthy volunteers and eight arm wrestling athletes performed forearm exercises at 30% of maximal voluntary effort until exhaustion. The exercises were either static or rhythmic, with alternating 20-s periods of muscle contraction and relaxation, followed by postexercise forearm arterial occlusion (PEAO). Heart rate, blood pressure (BP), and sympathetic nerve activity directed to muscle blood vessels (MSNA) were continuously recorded during the exercises. MSNA recordings were obtained from the peroneal nerve using a microneurographic method. During static exercises followed by PEAO, there were no differences in BP or MSNA between athletes and nonathlets. In contrast, a significant decrease in muscle pressor reflex responses was observed in the athletes during rhythmic exercises followed by PEAO. The possible relationship between this effect and changes in muscle energy supply, increased wash-out of metabolites, and reduced sensitivity of the muscle receptors in athletes is discussed.

Vinogradova O.L., Popov D.V., Netreba A.I., Tsvirkun D.V., Kurochkina N.S., Bachinin A.V., Bravyi Y.R., Lyubaeva E.V., Lysenko E.A., Miller T.F., Borovik A.S., Tarasova O.S., Orlov O.I.

The hypertrophic effect of strength training is known to be due to mechanical and metabolic stimuli. During exercises with the restricted blood supply of working muscles, i.e., under the conditions of intensified metabolic stress, the training effect may be achieved with much lower external loads (20% of one repetition maximum). The effects of 8 weeks of high-intensity (80–85% of one repetition maximum) strength training were compared to low-intensity (50% of one repetition maximum) training without relaxation. The high-intensity strength training resulted in higher increases in strength and size of the exercised muscles than training without relaxation. During high-intensity training, at the muscle cross section, an increase in the area occupied by type II fibers prevails; while, during training without relaxation, an increase in the area occupied by type I fibers prevails. An exercise session without relaxation leads to a more pronounced increase in the secretion of the growth hormone, insulin-like growth factor-1, and cortisol. The expression of gene regulating myogenesis (Myostatin) is changed in different ways after a high-intensity strength exercise session and after an exercise session without relaxation. Low-intensity strength training (50% of one repetition maximum) without relaxation is an efficient way for inducing increases of the strength and size of the trained muscles. This low-intensive type of training may be used in rehabilitation medicine, sports, and fitness.

Vinogradova O.L., Popov D.V., Tarasova O.S., Bravyi Y.R., Missina S.S., Bersenev E.Y., Borovik A.S.

Physical load increases sympathetic nervous activity, which results in an increased cardiac output, constriction of peripheral vessels, and elevated systemic blood pressure. These changes are outcomes of two mechanisms: the central command from cerebral structures that trigger voluntary movements to activate the vasomotor center and the reflexes initiated by mechanical and metabolic changes in a working muscle. The latter mechanism of the sympathetic system activation is termed ergoreflex. The main effects of ergoreflex on the indices of systemic hemodynamics are the following: activation of mechanosensitive afferents mainly leads to inhibition of the tonic vagal effects on the heart, which explains the rapid increase in heartbeats upon loading; activation of chemosensitive afferents comes with some delay in pace with metabolite accumulation in muscles and leads to an increase in efferent sympathetic activity and a rise in blood pressure. The metabolic reflex effect is particularly high in the case of muscle fatigue. This review deals with the mechanisms underlying the ergoreflex and their adaptation to hypodynamia, physical training, and some pathologies.

Netreba A.I., Bravyy Y.R., Makarov V.A., Ustyuzhanin D.V., Vinogradova O.L.

The goal of this study was to approbate a strength training protocol designed to improve motor skills at the maximum voluntary contraction (MVC) without hypertrophy of muscles. The main difference between this protocol and classical strength training was that the number of movements during a training session was increased to improve the motor skill, and the rest periods between the training movements were increased in order to minimize the damage of muscle fibers, which is one of the factors inducing muscle hypertrophy. Eleven subjects trained knee extensors of the right leg four times a week during four weeks. The evaluation of strength and speed characteristics with simultaneous recording the EMG activity was performed in both trained and untrained legs immediately before, during, and several times after the whole training period. Before and after the four-week training period, the size and contractile properties of the trained and contralateral knee extensors were evaluated by MRI and twitch interpolation technique. The maximal strength gains were about 17% in both trained and untrained legs; they did not differ significantly from each other. Noticeable increases in the EMG activity during the training period were observed. These changes were not accompanied by any significant changes in the muscle size, which demonstrates the “neural” nature of the training effects.

Netreba A.I., Popov D.V., Bravyi Y.R., Misina S.S., Vinogradova O.L.

The effects of low-intensity strength training without relaxation (LISTR) on the force-velocity properties of hip and knee extensor muscles, the power endurance of the knee extensor muscles, and the aerobic performance of the body were studied. The difference between the LISTR and classical strength training (CST) is that the working muscle groups do not relax at the extreme points of the range of motion. The study was performed in two groups each comprising nine young physically active men who trained three times a week for eight weeks. The study showed that LISTR increased the maximum voluntary force to about the same extent as CST, but this was achieved with lower training loads. Moreover, LISTR did not lead to a decrease in the local muscular work capacity, which is usually observed during CST.

Shenkman B.S., Lyubaeva E.V., Popov D.V., Netreba A.I., Bravy Y.R., Tarakin P.P., Lemesheva Y.S., Vinogradova O.L.

Effects of low-frequency electrical stimulation, which is currently considered to be a possible countermeasure for long-duration spaceflights, with and without stretch were evaluated. Twelve young male volunteers were randomly distributed into two groups. In one group anterior thigh muscles—knee extensors of both legs were stimulated with frequency of 15 Hz for 4.5 wks, six times a week; each session was 6-h long. In the other group, electrical stimulation with the same parameters was applied to stretched knee extensors. Following stimulation the subjects exhibited an increase in fatigue resistance, and in the succinate dehydrogenase activity and a 10% gain in the percentage of muscle fibers with slow myosin heavy chain isoforms. In a stimulated group the peak voluntary strength went down significantly, the CSA of fast muscle fibers in m. quadriceps femoris became slightly less in size (10%). Electrical stimulation of the stretched muscles induced an insignificant decline in their strength and an increase of cross-sectional area of muscle fibers of both types. Thus chronic low-frequency electrical stimulation may be proposed as a candidate countermeasure against muscle strength and mass loss if it is combined with stretch.

Maier L.E., Meyer S.E., Deprato A., Busch S., Sivak A., Davenport M.H., Steinback C.D.

Pozdnyakova A.E., Savon G.K., Lev L.P., Baltin M.E., Bravyy Y.R., Onishchenko D.A.

Panagiotou N., Sagonas A., Salata E., Fotis T., Ntoumou E.

Rowe S.J., Bekhuis Y., Mitchell A., Janssens K., D’Ambrosio P., Spencer L.W., Paratz E.D., Claessen G., Fatkin D., La Gerche A.

Carson R.G.

Mendes J., Palma J., Santos A., Ribeiro J., Oliveiros B., Silva H.

Hall E.C., John G., Ahmetov I.I.

Football clubs regularly test and monitor players, with different approaches reflecting player age and competitive level. This narrative review aims to summarise justifications for testing and commonly used testing protocols. We also aim to discuss the validity and reliability of specific tests used to assess football players and provide a holistic overview of protocols currently used in football or those demonstrating potential utility. The PubMed, SportDiscus, and Google Scholar databases were screened for relevant articles from inception to September 2024. Articles that met our inclusion criteria documented tests for several purposes, including talent identification or the assessment of growth/maturation, physiological capacity, sport-specific skill, health status, monitoring fatigue/recovery, training adaptation, and injury risk factors. We provide information on specific tests of anthropometry, physical capacity, biochemical markers, psychological indices, injury risk screening, sport-specific skills, and genetic profile and highlight where certain tests may require further evidence to support their use. The available evidence suggests that test selection and implementation are influenced by financial resources, coach perceptions, and playing schedules. The ability to conduct field-based testing at low cost and to test multiple players simultaneously appear to be key drivers of test development and implementation among practitioners working in elite football environments.

Borovik A.S., Pecheritsa M.A., Vinogradova O.L., Tarasova O.S.

The changes in blood pressure (BP) and heart rate (HR) during exercise grow with the development of muscle fatigue due to activation of the ergoreflex (ER), which is commonly assessed by post-exercise blood flow occlusion. However, this approach does not reproduce ER functioning in natural conditions and is of little use for testing ER from receptors of lower limb muscles, which differ from upper limb muscles in metabolic characteristics, and are also subject to more pronounced changes as a result of physical inactivity in various diseases. The aim of this study was to compare changes in systemic hemodynamics during “natural” ER activation with the development of severe fatigue in a test with rhythmic static contractions of thigh or forearm muscles until failure to work. Nine young men performed rhythmic isometric contractions of the knee extensors or the wrist flexors while maintaining a given load level (40% of the maximum voluntary effort) in a 20 s contraction/20 relaxation mode until fatigue (work duration in both tests was about 30 min). During the tests, systemic BP (Finapres), stroke volume (SV, ModelFlow algorithm) and ECG were continuously recorded. Rhythmic contractions of both muscle groups were accompanied by an increase in BP and HR, while SV decreased. As fatigue developed, the changes in BP and SV during muscle contraction became more pronounced. Importantly, during contractions of the thigh muscles, fatigue potentiated an increase in BP because of an increase in total peripheral resistance, and during contractions of the forearm muscles, because of an increase in cardiac output. Thus, fatigue of various muscle groups is accompanied by activation of different components of the ER – vascular component during lower limb exercise and cardiac component during upper limb exercise. The results obtained must be considered when developing methods for assessing hemodynamic control in cardiovascular diseases, which are often associated with changes in both skeletal muscles and the functioning of the ergoreflex.

Iskarevskii G.V., Pekonidi A.A., Beknazarova A.M., Pozdnyakova A.E., Onishchenko D.A., Kirsanov A.S., Baltin M.E., Bravyy Y.R.

Borzykh A.A., Zhedyaev R.Y., Ponomarev I.I., Vepkhvadze T.F., Zgoda V.G., Orlova M.A., Vavilov N.E., Lednev E.M., Sharlo K.A., Babkova A.R., Makhnovskii P.A., Shenkman B.S., Rukavishnikov I.V., Orlov O.I., Tomilovskaya E.S., et. al.

AbstractAimLow-intensity neuromuscular electrical stimulation was offered as a safe (non-traumatic) approach to prevent the loss of muscle mass, strength, and endurance in patients with severe chronic diseases and in spaceflight. However, the effects of this approach on various leg muscles are poorly investigated.MethodsThis study assessed the efficiency of low-intensity (∼10% of maximal voluntary contraction) electrical stimulation in preventing the negative effects of weekly disuse (dry immersion without and with daily stimulation) on the strength and aerobic performance of the ankle plantar flexors and knee extensors, mitochondrial function in permeabilized muscle fibers, and the proteomic (quantitative mass spectrometry-based analysis) and transcriptomic (RNA-sequencing) profiles of the soleus muscle and vastus lateralis muscle.ResultsApplication of electrical stimulation during dry immersion prevented a decrease in the maximal strength and a slight reduction in aerobic performance of knee extensors, as well as a decrease in maximal (intrinsic) ADP-stimulated mitochondrial respiration and changes in the expression of genes encoding mitochondrial, extracellular matrix, and membrane proteins in the vastus lateralis muscle. In contrast, for the ankle plantar flexors/soleus muscle, electrical stimulation had a positive effect only on maximal mitochondrial respiration, but accelerated the decline in the maximal strength and muscle fiber cross-sectional area, which appears to be related to the activation of inflammatory genes.ConclusionThe data obtained open up broad prospects for the use of low-intensity electrical stimulation to prevent the negative effects of disuse for “mixed” muscles, meanwhile, the optimization of the stimulation protocol is required for “slow” muscles.Practitioner PointsLow-intensity electrical myostimulation is often used as an alternative to exercise and high-intensity electrical stimulation to prevent the loss of muscle mass and function in patients with severe chronic diseases and in spaceflight. However, its effect on muscles with different functional capacities remains uncertain.One week of disuse (dry immersion) lead to a comparable decrease in the maximal strength and (intrinsic) mitochondrial respiration in both the ankle plantar flexors/soleus muscle and the knee extensors/vastus lateralis muscle. Meanwhile changes in gene expression (transcriptome) were three times more pronounced in the soleus muscle than in the vastus lateralis muscle.Application of electrical stimulation during disuse prevented most of the negative effects of disuse in the knee extensors/vastus lateralis muscle, but accelerated the decline in the maximal strength/muscle fiber cross-sectional area in the ankle plantar flexors/soleus muscle, which may be related to the activation of genes regulating the inflammatory response.

Borovik A.S., Pecheritsa M.A., Vinogradova O.L., Tarasova O.S.

The changes in blood pressure (BP) and heart rate (HR) during exercise grow with the development of muscle fatigue due to activation of the ergoreflex (ER), which is commonly assessed by post-exercise blood flow occlusion. However, this approach does not reproduce ER functioning in natural conditions and is of little use for testing ER from receptors of lower limb muscles, which differ from upper limb muscles in metabolic characteristics, and are also subject to more pronounced changes during physical inactivity in various diseases. The aim of this study was to compare changes in systemic hemodynamics during “natural” ER activation in a test with rhythmic static contractions of thigh or forearm muscles until the development of severe fatigue. Nine young men performed rhythmic isometric contractions of the knee extensors or the wrist flexors while maintaining a given load level (40% of the maximum voluntary effort) in a 20 s contraction/20 s relaxation mode until fatigue (work duration in both tests was about 30 min). During the tests, systemic BP (Finapres), stroke volume (SV, ModelFlow algorithm) and ECG were continuously recorded. Rhythmic contractions of both muscle groups were accompanied by an increase in BP and HR, while SV decreased. As fatigue developed, the changes in BP and SV during muscle contraction became more pronounced. Importantly, during contractions of the thigh muscles, fatigue potentiated an increase in BP because of an increase in total peripheral resistance, and during contractions of the forearm muscles because of an increase in cardiac output. Thus, fatigue of various muscle groups is accompanied by activation of different components of the ER: vascular component during lower limb exercise and cardiac component during upper limb exercise. The results must be considered when developing methods for assessing hemodynamic control in cardiovascular diseases, which are often associated with changes in skeletal muscles and ER functioning.

Parnow A., Amani-Shalamzari S., Mohr M., Bagchi S., Dutta S., Sengupta P.

Abstract Objectives This prospective cross-sectional study aimed to delineate associations between the performance and physiological responses to the Bruce test with two field tests, the futsal intermittent endurance test (FIET) and the Yo-Yo intermittent recovery test level-2 (YYIR2) in elite male futsal players, in order to endorse one of field test to futsal coaches. Methods Fifteen elite futsal players (age 20 ± 3 years) have been participated in this study. Main outcome measurements included aerobic power, heart rate, blood lactate, ventilation, VO2, VCO2, VE-VO2, and VE-VCO2 indicators during FIET, YYIR2, and the Bruce test with carrying out a portable gas analyzer. Results The Bruce test is significantly correlated with FIET and YYIR2 with respect to key outcome measures, including performance (r>0.59), aerobic power (r>0.69), heart rate (r>0.80), and blood lactate levels (r>0.60). The two field tests, FIET and YYIR2, were found to exhibit strong to perfect interrelationships. When examining the indicators such as VE, VO2, VCO2, VE-VO2, and VE-VCO2, moderate to strong correlations were identified across all three testing methods. However, the relationship between the Bruce test and YYIR2 was particularly noteworthy in terms of respiratory exchange ratio (RER) and metabolic equivalent of task (METS), showing a significant correlation. Conclusions The YYIR2 and FIET appear to be valid practical field tests for measuring aerobic fitness and performance in competitive male futsal players.

Veterini A.S., Semedi B.P., Airlangga P.S., Firdaus K.M., Uhud A.N., Kriswidyatomo P., Sumara R.

Abstract Background Numerous attempts have been made at both prevention and treatment of COVID-19. Specific genotypes carry a risk of causing clinical symptoms that can be beneficial or detrimental. We performed nutrigenomics testing on COVID-19 survivors who were on ventilators during their treatment and mild COVID-19 survivors who did not require ventilators to determine the risk of genetic variation through nutrigenomic testing regarding COVID-19 incidence. DNA was isolated from saliva and genotyped for genetic markers using a commercially available nutrigenomics test. We compared genotype frequencies between those with severe symptoms (cases) and those with mild symptoms (controls). Result Sequencing results showed that the distribution from pattern of the Sankey diagram included an ultra risk category in the control group, but not in the case group. None of the subjects in the case group were in the ultra risk category for resilience. A descriptive pattern of risk-level distribution was observed in both the control and case groups. One subject in the ultra risk category was in the control group, indicating a lower risk factor for severe COVID-19. Conclusion From this study, a uniqueness begins to emerge, revealing the discovery of ultra-category patterns in the endurance of the control group. The vitamin E risk deficiency is significantly higher in the severe COVID-19 group compared to the mild group, categorized as "typical."

Sutkowy P., Modrzejewska M., Porzych M., Woźniak A.

The significance of physical activity in sports is self-evident. However, its importance is becoming increasingly apparent in the context of public health. The constant desire to improve health and performance suggests looking at genetic predispositions. The knowledge of genes related to physical performance can be utilized initially in the training of athletes to assign them to the appropriate sport. In the field of medicine, this knowledge may be more effectively utilized in the prevention and treatment of cardiometabolic diseases. Physical exertion engages the entire organism, and at a basic physiological level, the organism’s responses are primarily related to oxidant and antioxidant reactions due to intensified cellular respiration. Therefore, the modifications involve the body adjusting to the stresses, especially oxidative stress. The consequence of regular exercise is primarily an increase in antioxidant capacity. Among the genes considered, those that promote oxidative processes dominate, as they are associated with energy production during exercise. What is missing, however, is a look at the other side of the coin, which, in this case, is antioxidant processes and the genes associated with them. It has been demonstrated that antioxidant genes associated with increased physical performance do not always result in increased antioxidant capacity. Nevertheless, it seems that maintaining the oxidant–antioxidant balance is the most important thing in this regard.

Nasb M., Wei M., Lin B., Chen N.

The swift acceleration of advances in precision medicine has attracted clinicians, health systems, and policymakers, thus leaving an indelible mark on the landscape of medical practice. The increasing acknowledgment of precision medicine shows the rise of a promising new field that can change medical practice and provide medical care. Simultaneously, there is an increasing interest in precision exercise, which refers to an approach in healthcare and fitness where exercise regimens are tailored to individual responses and characteristics. Precision exercise has evolved as a response to the understanding that individuals exhibit a wide range of responses to exercise regimens, attributed to genetic modifications and other biological factors. The purpose of this article is to offer a comprehensive evaluation of basic principles, methods, and practical applications of precision exercise. Additionally, exercise biomarkers serve as pivotal indicators, bridging biological mechanisms of exercise with overall health. These biomarkers offer insights into individual physiological responses, enabling the customization of exercise regimens to optimize health outcomes. Herein, this article underscores the transformative potential of precision exercise in revolutionizing personalized healthcare and customized exercise regimens, guided by the insights based on exercise biomarkers. As precision medicine continues to evolve, precision exercise stands at the forefront, thereby promising a future where medical and exercise interventions are uniquely customized for optimal health outcomes.

Iskarevskii G.V., Pekonidi A.A., Beknazarova A.M., Pozdnyakova A.E., Onishchenko D.A., Kirsanov A.S., Baltin M.E., Bravyy Y.R.

Jakubowitz E., Schmidt L., Obermeier A., Spindeldreier S., Windhagen H., Hurschler C.

AbstractThis study investigated how muscle synergies adapt in response to unexpected changes in object weight during lifting tasks. The aim was to discover which motor control strategies individuals use to maintain their grasping performance. Muscle synergies were extracted from the muscle activity of fifteen healthy participants who lifted objects of identical appearance but varying weights in a randomized order, which introduced artificial perturbations. Reaching and manipulation phases of object lifting were analyzed using constrained non-negative matrix factorization and k-means clustering. Participants exhibited a perturbation-independent and thus consistent recruitment of spatial synergy components, while significant adaptations in muscle synergy activation occurred in response to unexpected perturbations. Perturbations caused by unexpectedly heavy objects led to delayed and gradual increases in muscle synergy activation until the force required to lift the object was reached. In contrast, perturbations caused by lighter objects led to reductions in excess muscle synergy activation occurring later. Sensorimotor control maintains the modularity of muscle synergies. Even when external mechanical perturbations occur, the grasping performance is preserved, and control is adapted solely through muscle synergy activation. These results suggest that using pure spatial synergy components as control signals for myoelectric arm prostheses may prevent them from malfunctioning due to external perturbations.

Petrov M., Kniga A., Dyachenko D., Dubodelov A., Simakov S.

The article presents the experience of developing a hardware and software complex designed to monitor the performance of sports exercises and diagnose the state of the athlete’s musculoskeletal system. The algorithms used are described and their significance for the problem being solved is justified.

Lin C., Chen C., Cui Z., Zhu X.

To utilize surface electromyographics (sEMG) for control purposes, it is necessary to perform real-time estimation of the neural drive to the muscles, which involves real-time decomposition of the EMG signals. In this paper, we propose a Bidirectional Gate Recurrent Unit (Bi-GRU) network with attention to perform online decomposition of high-density sEMG signals. The model can give different levels of attention to different parts of the sEMG signal according to their importance using the attention mechanism. The output of gradient convolutional kernel compensation (gCKC) algorithm was used as the training label, and simulated and experimental sEMG data were divided into windows with 120 sample points for model training, the sampling rate of sEMG signal is 2048 Hz. We test different attention mechanisms and find out the ones that could bring the highest F1-score of the model. The simulated sEMG signal is synthesized from Fuglevand method (J. Neurophysiol., 1993). For the decomposition of 10 Motor Units (MUs), the network trained on simulated data achieved an average F1-score of 0.974 (range from 0.96 to 0.98), and the network trained on experimental data achieved an average F1-score of 0.876 (range from 0.82 to 0.97). The average decomposition time for each window was 28 ms (range from 25.6  ms to 30.5 ms), which falls within the lower bound of the human electromechanical delay. The experimental results show the feasibility of using Bi-GRU-Attention network for the real-time decomposition of Motor Units. Compared to the gCKC algorithm, which is considered the gold standard in the medical field, this model sacrifices a small amount of accuracy but significantly improves computational speed by eliminating the need for calculating the cross-correlation matrix and performing iterative computations.

Ma Y., Liu D., Yan Z., Yu L., Gui L., Yang C., Yang W.

Exoskeleton robots hold promising prospects for rehabilitation training in individuals with weakened muscular conditions. However, achieving improved human–machine interaction and delivering customized assistance remains a challenging task. This paper introduces a muscle synergy-based human-in-the-loop (HIL) optimization framework for hip exoskeletons to offer more personalized torque assistance. Initially, we propose a muscle synergy similarity index to quantify the similarity of synergy while walking with and without the assistance of an exoskeleton. By integrating surface electromyography (sEMG) signals to calculate metrics evaluating muscle synergy and iteratively optimizing assistance parameters in real time, a muscle synergy-based HIL optimized torque configuration is presented and tested on a portable hip exoskeleton. Iterative optimization explores the optimal and suboptimal assistance torque profiles for six healthy volunteers, simultaneously testing zero torque and predefined assistance configurations, and verified the corresponding muscle synergy similarity indices through experimental testing. In our validation experiments, the assistance parameters generated through HIL optimization significantly enhance muscle synergy similarity during walking with exoskeletal assistance, with an optimal average of 0.80 ± 0.04 (mean ± std), marking a 6.3% improvement over prior assistive studies and achieving 96.4% similarity compared with free walking. This demonstrates that the proposed muscle synergy-based HIL optimization can ensure robotic exoskeleton-assisted walking as “natural” as possible.

Ao X., Wang F., Wang R., She J.

Muscle synergy analysis for gesture recognition is a fundamental research area in human-machine interaction, particularly in fields such as rehabilitation. However, previous methods for analyzing muscle synergy are typically not end-to-end and lack interpretability. Specifically, these methods involve extracting specific features for gesture recognition from surface electromyography (sEMG) signals and then conducting muscle synergy analysis based on those features. Addressing these limitations, we devised an end-to-end framework, namely Shapley-value-based muscle synergy (SVMS), for muscle synergy analysis. Our approach involves converting sEMG signals into grayscale sEMG images using a sliding window. Subsequently, we convert adjacent grayscale images into color images for gesture recognition. We then use the gradient-weighted class activation mapping (Grad-CAM) method to identify significant feature areas for sEMG images during gesture recognition. Grad-CAM generates a heatmap representation of the images, highlighting the regions that the model uses to make its prediction. Finally, we conduct a quantitative analysis of muscle synergy in the specific area obtained by Grad-CAM based on the Shapley value. The experimental results demonstrate the effectiveness of our SVMS method for muscle synergy analysis. Moreover, we are able to achieve a recognition accuracy of 94.26% for twelve gestures while reducing the required electrode channel information from ten to six dimensions and the analysis rounds from about 1000 to nine.

Lowe T.W., Tenan M.S., Shah K., Griffin L.

Resistance training with low loads in combination with blood flow restriction (BFR) facilitates increases in muscle size and strength comparable with high-intensity exercise. We investigated the effects of BFR on single motor unit discharge behavior throughout a sustained low-intensity isometric contraction. Ten healthy individuals attended two experimental sessions: one with, the other without, BFR. Motor unit discharge rates from the tibialis anterior (TA) were recorded with intramuscular fine-wire electrodes throughout the duration of a sustained fatigue task. Three 5-s dorsiflexion maximal voluntary contractions (MVC) were performed before and after the fatigue task. Each participant held a target force of 20% MVC until endurance limit. A significant decrease in motor unit discharge rate was observed in both the non-BFR condition (from 13.13 ± 0.87 Hz to 11.95 ± 0.43 Hz, P = 0.03) and the BFR condition (from 12.95 ± 0.71 Hz to 10.9 ± 0.75 Hz, P = 0.03). BFR resulted in significantly shorter endurance time and time-to-minimum discharge rates and greater end-stage motor unit variability. Thus, low-load BFR causes an immediate steep decline in motor unit discharge rate that is greater than during contractions performed without BFR. This shortened neuromuscular response of time-to-minimum discharge rate likely contributes to the rapid rate of neuromuscular fatigue observed during BFR.

Shoji H., Ikeda K., Miyakawa T.

AbstractThe serotonin transporter (5-HTT) plays a critical role in the regulation of serotonin neurotransmission. Mice genetically deficient in 5-HTT expression have been used to study the physiological functions of 5-HTT in the brain and have been proposed as a potential animal model for neuropsychiatric and neurodevelopmental disorders. Recent studies have provided evidence for a link between the gut-brain axis and mood disorders. However, the effects of 5-HTT deficiency on gut microbiota, brain function, and behavior remain to be fully characterized. Here we investigated the effects of 5-HTT deficiency on different types of behavior, the gut microbiome, and brain c-Fos expression as a marker of neuronal activation in response to the forced swim test for assessing depression-related behavior in male 5-HTT knockout mice. Behavioral analysis using a battery of 16 different tests showed that 5-HTT−/− mice exhibited markedly reduced locomotor activity, decreased pain sensitivity, reduced motor function, increased anxiety-like and depression-related behavior, altered social behavior in novel and familiar environments, normal working memory, enhanced spatial reference memory, and impaired fear memory compared to 5-HTT+/+ mice. 5-HTT+/− mice showed slightly reduced locomotor activity and impaired social behavior compared to 5-HTT+/+ mice. Analysis of 16S rRNA gene amplicons showed that 5-HTT−/− mice had altered gut microbiota abundances, such as a decrease in Allobaculum, Bifidobacterium, Clostridium sensu stricto, and Turicibacter, compared to 5-HTT+/+ mice. This study also showed that after exposure to the forced swim test, the number of c-Fos-positive cells was higher in the paraventricular thalamus and lateral hypothalamus and was lower in the prefrontal cortical regions, nucleus accumbens shell, dorsolateral septal nucleus, hippocampal regions, and ventromedial hypothalamus in 5-HTT−/− mice than in 5-HTT+/+ mice. These phenotypes of 5-HTT−/− mice partially recapitulate clinical observations in humans with major depressive disorder. The present findings indicate that 5-HTT-deficient mice serve as a good and valid animal model to study anxiety and depression with altered gut microbial composition and abnormal neuronal activity in the brain, highlighting the importance of 5-HTT in brain function and the mechanisms underlying the regulation of anxiety and depression.

Mundt M., Born Z., Goldacre M., Alderson J.

The adoption of computer vision pose estimation approaches, used to identify keypoint locations which are intended to reflect the necessary anatomical landmarks relied upon by biomechanists for musculoskeletal modelling, has gained increasing traction in recent years. This uptake has been further accelerated by keypoint use as inputs into machine learning models used to estimate biomechanical parameters such as ground reaction forces (GRFs) in the absence of instrumentation required for direct measurement. This study first aimed to investigate the keypoint detection rate of three open-source pose estimation models (AlphaPose, BlazePose, and OpenPose) across varying movements, camera views, and trial lengths. Second, this study aimed to assess the suitability and interchangeability of keypoints detected by each pose estimation model when used as inputs into machine learning models for the estimation of GRFs. The keypoint detection rate of BlazePose was distinctly lower than that of AlphaPose and OpenPose. All pose estimation models achieved a high keypoint detection rate at the centre of an image frame and a lower detection rate in the true sagittal plane camera field of view, compared with slightly anteriorly or posteriorly located quasi-sagittal plane camera views. The three-dimensional ground reaction force, instantaneous loading rate, and peak force for running could be estimated using the keypoints of all three pose estimation models. However, only AlphaPose and OpenPose keypoints could be used interchangeably with a machine learning model trained to estimate GRFs based on AlphaPose keypoints resulting in a high estimation accuracy when OpenPose keypoints were used as inputs and vice versa. The findings of this study highlight the need for further evaluation of computer vision-based pose estimation models for application in biomechanical human modelling, and the limitations of machine learning-based GRF estimation models that rely on 2D keypoints. This is of particular relevance given that machine learning models informing athlete monitoring guidelines are being developed for application related to athlete well-being.

Kim J., Yang S., Koo B., Lee S., Park S., Kim S., Cho K.H., Kim Y.

sEMG-based gesture recognition is useful for human–computer interactions, especially for technology supporting rehabilitation training and the control of electric prostheses. However, high variability in the sEMG signals of untrained users degrades the performance of gesture recognition algorithms. In this study, the hand posture recognition algorithm and radar plot-based visual feedback training were developed using multichannel sEMG sensors. Ten healthy adults and one bilateral forearm amputee participated by repeating twelve hand postures ten times. The visual feedback training was performed for two days and five days in healthy adults and a forearm amputee, respectively. Artificial neural network classifiers were trained with two types of feature vectors: a single feature vector and a combination of feature vectors. The classification accuracy of the forearm amputee increased significantly after three days of hand posture training. These results indicate that the visual feedback training efficiently improved the performance of sEMG-based hand posture recognition by reducing variability in the sEMG signal. Furthermore, a bilateral forearm amputee was able to participate in the rehabilitation training by using a radar plot, and the radar plot-based visual feedback training would help the amputees to control various electric prostheses.

Varillas-Delgado D., Del Coso J., Gutiérrez-Hellín J., Aguilar-Navarro M., Muñoz A., Maestro A., Morencos E.

The impact of genetics on physiology and sports performance is one of the most debated research aspects in sports sciences. Nearly 200 genetic polymorphisms have been found to influence sports performance traits, and over 20 polymorphisms may condition the status of the elite athlete. However, with the current evidence, it is certainly too early a stage to determine how to use genotyping as a tool for predicting exercise/sports performance or improving current methods of training. Research on this topic presents methodological limitations such as the lack of measurement of valid exercise performance phenotypes that make the study results difficult to interpret. Additionally, many studies present an insufficient cohort of athletes, or their classification as elite is dubious, which may introduce expectancy effects. Finally, the assessment of a progressively higher number of polymorphisms in the studies and the introduction of new analysis tools, such as the total genotype score (TGS) and genome-wide association studies (GWAS), have produced a considerable advance in the power of the analyses and a change from the study of single variants to determine pathways and systems associated with performance. The purpose of the present study was to comprehensively review evidence on the impact of genetics on endurance- and power-based exercise performance to clearly determine the potential utility of genotyping for detecting sports talent, enhancing training, or preventing exercise-related injuries, and to present an overview of recent research that has attempted to correct the methodological issues found in previous investigations.

Perera E., Zhu X.M., Horner N.S., Bedi A., Ayeni O.R., Khan M.

Blood flow restriction (BFR) training is an increasingly applied tool with potential benefits in muscular hypertrophy, strength, and endurance. This study investigates the effectiveness of BFR training relative to other forms of training on muscle strength, hypertrophy, and endurance.We performed systematic searches of MEDLINE, Embase, and PubMed and assessed the methodological quality of included studies using the Cochrane risk of bias tool.We included 53 randomized controlled trials with 31 included in meta-analyses. For muscular strength comparing low-intensity BFR (LI-BFR) training with high-intensity resistance training (HIRT), the pooled mean difference (MD) for 1 repetition maximum was 5.34 kg (95% CI, 2.58-8.09; P < 0.01) favoring HIRT. When comparing LI-BFR training with HIRT for torque, the MD was 6.35 N·m (95% CI, 0.5-12.3; P = 0.04) also favoring HIRT. However, comparing LI-BFR with low-intensity resistance training (LIRT) for torque, there was a MD of 9.94 N·m (95% CI, 5.43-14.45; P < 0.01) favoring BFR training. Assessing muscle hypertrophy, the MD in cross-sectional area was 0.96 cm2 (95% CI, 0.21-1.7; P = 0.01) favoring pooled BFR training compared with nonocclusive training. Assessing endurance, V̇o2 maximum demonstrated a greater mean increase of 0.37 mL/kg/min (95% CI, -0.97 to 3.17; P = 0.64) in BFR endurance training compared with endurance training alone.Blood flow restriction training produced increases in muscular strength, hypertrophy, and endurance. Comparing LI-BFR training with HIRT, HIRT was a significantly better training modality for increasing muscle hypertrophy and strength. However, LI-BFR was superior when compared with a similar low-intensity protocol. Blood flow restriction training is potentially beneficial to those unable to tolerate the high loads of HIRT; however, better understanding of its risk to benefit ratio is needed before clinical application.Level 1.

Kim J., Koo B., Nam Y., Kim Y.

Surface electromyography (sEMG)-based gesture recognition systems provide the intuitive and accurate recognition of various gestures in human-computer interaction. In this study, an sEMG-based hand posture recognition algorithm was developed, considering three main problems: electrode shift, feature vectors, and posture groups. The sEMG signal was measured using an armband sensor with the electrode shift. An artificial neural network classifier was trained using 21 feature vectors for seven different posture groups. The inter-session and inter-feature Pearson correlation coefficients (PCCs) were calculated. The results indicate that the classification performance improved with the number of training sessions of the electrode shift. The number of sessions necessary for efficient training was four, and the feature vectors with a high inter-session PCC (r > 0.7) exhibited high classification accuracy. Similarities between postures in a posture group decreased the classification accuracy. Our results indicate that the classification accuracy could be improved with the addition of more electrode shift training sessions and that the PCC is useful for selecting the feature vector. Furthermore, hand posture selection was as important as feature vector selection. These findings will help in optimizing the sEMG-based pattern recognition algorithm more easily and quickly.

Grzywacz A., Chmielowiec K., Boroń A., Michałowska-Sawczyn M., Chmielowiec J., Trybek G., Mroczek B., Leźnicka K., Cieszczyk P., Masiak J.

In the mammalian genome, DNA methylation is an epigenetic mechanism involving the transfer of a methyl group onto the C5 position of the cytosine to form 5-methylcytosine. DNA methylation regulates gene expression by recruiting proteins involved in gene repression or by inhibiting the binding of transcription factors (TFs) to DNA. As there are still many questions concerning the role of methylation in creating personality, we concentrated on searching for such associations. The research group was 100 sports male subjects (mean age = 22.88, SD = 6.35), whereas the control group included 239 healthy male volunteers matched for age (mean age = 21.69, SD = 3.39), both of European origin. The methods used in our research were as follows: DNA isolation, methylation-specific PCR, sequencing chromatophores, all conducted according to the manufacturer’s procedure. To evaluate personality traits, the NEO Five-Factor Personality Inventory (NEO-FFI) and STAI Inventory were used. We observed the existence of a statistically significant correlation for all the aspects of personality covered and CpG islands’ methylation. Nonetheless, we think that the tested group and the number of tested promotor islands in the DAT1 gene are still too small to make explicit conclusions, so it needs further profound analysis.

Edinoff A.N., Akuly H.A., Hanna T.A., Ochoa C.O., Patti S.J., Ghaffar Y.A., Kaye A.D., Viswanath O., Urits I., Boyer A.G., Cornett E.M., Kaye A.M.

Depression is the most prevalent psychiatric disorder in the world, affecting 4.4% of the global population. Despite an array of treatment modalities, depressive disorders remain difficult to manage due to many factors. Beginning with the introduction of fluoxetine to the United States in 1988, selective serotonin reuptake inhibitors (SSRIs) quickly became a mainstay of treatment for a variety of psychiatric disorders. The primary mechanism of action of SSRIs is to inhibit presynaptic reuptake of serotonin at the serotonin transporter, subsequently increasing serotonin at the postsynaptic membrane in the serotonergic synapse. The six major SSRIs that are marketed in the USA today, fluoxetine, citalopram, escitalopram, paroxetine, sertraline, and fluvoxamine, are a group of structurally unrelated molecules that share a similar mechanism of action. While their primary mechanism of action is similar, each SSRI has unique pharmacokinetics, pharmacodynamics, and side effect profile. One of the more controversial adverse effects of SSRIs is the black box warning for increased risk of suicidality in children and young adults aged 18–24. There is a lack of understanding of the complexities and interactions between SSRIs in the developing brain of a young person with depression. Adults, who do not have certain risk factors, which could be confounding factors, do not seem to carry this increased risk of suicidality. Ultimately, when prescribing SSRIs to any patient, a risk–benefit analysis must factor in the potential treatment effects, adverse effects, and dangers of the illness to be treated. The aim of this review is to educate clinicians on potential adverse effects of SSRIs.