Intermuscular Coordination Research Articles

Optimizing Resistance Training for Sprint and Endurance Athletes: Balancing Positive and Negative Adaptations.

Resistance training (RT) triggers diverse morphological and physiological adaptations that are broadly considered beneficial for performance enhancement as well as injury risk reduction. Some athletes and coaches therefore engage in, or prescribe, substantial amounts of RT under the assumption that continued increments in maximal strength capacity and/or muscle mass will lead to improved sports performance. In contrast, others employ minimal or no RT under the assumption that RT may impair endurance or sprint performances. However, the morphological and physiological adaptations by which RT might impair physical performance, the likelihood of these being evoked, and the training program specifications that might promote such impairments, remain largely undefined. Here, we discuss how selected adaptations to RT may enhance or impair speed and endurance performances while also addressing the RT program variables under which these adaptations are likely to occur. Specifically, we argue that while some myofibrillar (muscle) hypertrophy can be beneficial for increasing maximum strength, substantial hypertrophy can lead to macro- and microscopic adaptations such as increases in body (or limb) mass and internal moment arms that might, under some conditions, impair both sprint and endurance performances. Further, we discuss how changes in muscle architecture, fiber typology, microscopic muscle structure, and intra- and intermuscular coordination with RT may maximize speed at the expense of endurance, or maximize strength at the expense of speed. The beneficial effect of RT for sprint and endurance sports can be further improved by considering the adaptive trade-offs and practical implications discussed in this review.

Age-related breakdown in networks of inter-muscular coordination.

Assessing inter-muscular coordination in older adults is crucial, as it directly impacts an individual's ability for independent functioning, injury prevention, and active engagement in daily activities. However, the precise mechanisms by which distinct muscle fiber types synchronize their activity across muscles to generate coordinated movements in older adults remain unknown. Our objective is to investigate how distinct muscle groups dynamically synchronize with each other in young and older adults during exercise. Thirty-five young adults and nine older adults performed one bodyweight squat set until exhaustion. Simultaneous surface electromyography (sEMG) recordings were taken from the left and right vastus lateralis, and left and right erector spinae. To quantify inter-muscular coordination, we first obtained ten time series of sEMG band power for each muscle, representing the dynamics of different muscle fiber types. Next, we calculated the bivariate equal-time Pearson's cross-correlation for each pair of sEMG band power time series across all leg and back muscles. The main results show (i) an overall reduction in the degree of inter-muscular coordination, and (ii) increased stratification of the inter-muscular network in older adults compared to young adults. These findings suggest that as individuals age, the global inter-muscular network becomes less flexible and adaptable, hindering its ability to reorganize effectively in response to fatigue or other stimuli. This network approach opens new avenues for developing novel network-based markers to characterize multilevel inter-muscular interactions, which can help target functional deficits and potentially reduce the risk of falls and neuro-muscular injuries in older adults.

Wavelet Coherence Analysis of Post-Stroke Intermuscular Coupling Modulated by Myoelectric-Controlled Interfaces.

Intermuscular coupling reflects the corticospinal interaction associated with the control of muscles. Nevertheless, the deterioration of intermuscular coupling caused by stroke has not received much attention. The purpose of this study was to investigate the effect of myoelectric-controlled interface (MCI) dimensionality on the intermuscular coupling after stroke. In total, ten age-matched controls and eight stroke patients were recruited and executed elbow tracking tasks within 1D or 2D MCI. Movement performance was quantified using the root mean square error (RMSE). Wavelet coherence was used to analyze the intermuscular coupling in alpha band (8-12 Hz) and beta band (15-35 Hz). The results found that smaller RMSE of antagonist muscles was observed in both groups within 2D MCI compared to 1D MCI. The alpha-band wavelet coherence was significantly lower in the patients compared to the controls during elbow extension. Furthermore, a decreased alpha-band and beta-band wavelet coherence was observed in the controls and stroke patients, as the dimensionality of MCI increased. These results may suggest that stroke-related neural impairments deteriorate the motor performance and intermuscular coordination pattern, and, further, that MCI holds promise as a novel effective tool for rehabilitation through the direct modulation of muscle activation pattern.

Strength Simulator Codes for Different Age Groups Considering Physiological Processes of Adaptation in Conditions of Strength Fitness

Topicality. Determination of optimal load parameters in fitness, based on age-related physiological features and adaptive changes of the neuromuscular system, is one of the most debated issues among leading scientists in this field. The research purpose was to develop models of code combinations for strength training of different age groups, considering physiological processes of human body adaptation to a stressful physical stimulus in the conditions of strength fitness. Methods. A comparative analysis of the research results on the effectiveness of using the optimal combination between the parameters of an external physical stimulus and the physiological features of the human body adaptive reactions has been used over the research. The results. It was established that in the process of developing code combinations for different age groups` strength training, the nature of the physiological reactions of their neuromuscular system to a stressful stimulus depend on the features of the load regime and the structure of the exercise program. For adolescence, considering the peculiarities of the physiological process of adaptation, it is used of moderate-intensity activity in combination with a complex of isolation exercises that promotes the processes of intra-muscular and inter-muscular coordination. For youth, in the process of developing code combinations aimed at the development of the main types of strength, the entire range of load modes is actively used. Particular attention is paid to stimuli that contribute to increasing the number of active (FF) motor units. In adulthood, especially in the second period, the content of code combinations to increase strength capabilities changes significantly. In the vast majority, this applies to the parameters of the intensity of load modes, the use of which will selectively affect the hypertrophy of a certain type of muscle fibers within intermuscular coordination. For the elderly, in the process of developing code combinations for strength training, priority is given to the selective activity of agonists during moderate-intensity isolated exercises. Findings. Strength Simulator codes considering physiological processes of the neuromuscular system adaptation to a stressful physical stimulus, is one of the innovative mechanisms for improving the training program of different age groups in the conditions of strength fitness.

Physiology and biomechanics researches of the special preparedness and contention activity of highly skilled kayakers

Purpose — development of methodology for individual evaluating special fitness and competitive activity of highly skilled kayakers.
 The rationality of the rower’s movement structure is largely determined by the character of work and interaction of the posterior and anterior bundles of the deltoid muscle, which perform the rower’s arm movements during applying both “pulling” and “pushing” efforts. The following causes of individual rowing technique errors significantly affecting sports result were identified: general muscle rigidity, lack of sufficiently complete and timely muscle relaxation; untimely involvement of muscles in work (appearance of mutual activity zones of antagonist muscles); late start of muscle activity (inertial moments of movement of rower's body biolinks are not provided before water entrapment); protracted, too long muscle activity (movement is performed entirely at the expense of muscular activity, without the use of inertial and propelling forces); low speed of muscle engagement in work leading, as a rule, to the “drop” of efforts on the oar. Two groups of athletes with diametrically opposite levels of physical capacity development and one group, which was characterized by their uniform development, were distinguished. The first group was distinguished by the high indices of power and efficiency of the work performed while covering the competitive distance. Such athletes showed higher sports results on short distances. The second group was distinguished by high indices of the efficiency of applying efforts, symmetry of movements, and successful performances on long competitive distances. Such rowers were classified as athletes with predominant development of special endurance quality. The rowers of the third group differed in the average values of the above mentioned indices and demonstrated equal success on both short and long competitive distances. Athletes with preferential development of speed-strength qualities and rowers with an advantageous development of special endurance have no significant difference in speed of covering 500 m distance and heart rate. However, there are significant differences in other indices of special fitness. Rowers with even development of physical qualities have differences in all recorded indices compared to those of the first two groups.
 The individual peculiarities of rowers’ movement coordination during covering a competitive distance of 500 m were determined. All rowers are divided into two groups. The first group is characterized by rational coordination of movements at the beginning of the distance covering and pronounced disturbances in the work dynamics of the muscles of the body turn and the nature of effort applied to the oar at the end of the distance. In the second group, we encounter the opposite phenomenon: with an irrational movement structure at the beginning of the distance, there is a transition of work to a more correct character at the end of its covering. The most preferable option for increasing the efficiency of athletes’ technical preparation is the use of the methodology for designing generalized and individual models of motor action structure. Preparation of rowers with account for their predisposition to the formation of the most important components of sportsmanship is the most preferable option. When drawing up individual plans for the preparation of athletes, the coaches should take into account these practical recommendations and adhere to the recommended directions of training. Repeated examinations (four months later) revealed the effectiveness of managing the process of technical preparation of kayakers based on the correction of intermuscular coordination.

Дослідження взаємозв’язків між психофізіологічними здібностями та спритністю каратистів-новачків

Purpose: to determine the correlation between psychophysiological abilities and agility in novice karate practitioners. Material and methods. In this study, the following research methods were employed: theoretical analysis and synthesis of scientific and methodological literature; pedagogical observation; pedagogical research; psychophysiological measurements and mathematical-statistical research methods. The study involved 20 athletes (14 males, 6 females) with an average age of 10,8±1,1 years (Mean±SD) who practiced karate. To assess agility, participants were required to perform a special relay race. The relay race, with a length of 15 meters, included the following exercises: ball translation, jumping, crawling, and running. To determine the speed component, athletes were instructed to run the distance of the relay race. Psychophysiological characteristics were assessed using tests such as reaction to a moving object, choice reaction, short-term visual memory, and the tapping test (duration 1 minute). Results: according to the results of cluster analysis, it is noted that classes were formed based on the age of the athletes. Thus, younger karate practitioners (9-10 years old), including participants 6, 7, 1, 9, belonged to the first class, while older karate practitioners (12 years old), including participants 17, 19, 20, 14, 18, primarily comprised the second class. The third class mainly included karate practitioners aged 10-11. Correlation analysis of the obtained data, specifically determining the relationships between agility and psychophysiological indicators, indicates statistically significant connections. Notably, there are correlations between relay race results and tapping test results at 5s (r=0,69), 10 s (r=0,55), 1 min (r=0,69). There are also correlations regarding choice reaction at the 2nd (r=0,65), 3rd (r=0,51), 4th (r=0,58) stages and overall test (r=0,60). A statistically significant correlation between the age of athletes and results, practically demonstrated in all tests (on average r=0,67), is also observed. The presence of these correlations can be explained by the fact that agility is a complex quality influenced by various factors such as age, neural process mobility, intermuscular coordination, reaction time, and others. The results of 11-12-year-old athletes surpass those of 9-10-year-olds in all tests. Statistically significant differences (p<0,05) were recorded in tests such as running, relay race, tapping test (5 s, 1 min), short-term visual memory coefficient, and choice reaction. A comparison of the results of the investigated groups of karate practitioners indicates that statistically significant improvement in short-term visual memory and choice reaction is the result not only of an increase in the athletes' age but also the influence of specific training tasks on the functional state of the athletes. Conclusions. Agility, based on motor reactions and spatial-temporal anticipations, underlies the activities of martial artists in unpredictable and rapidly changing situations. The study results indicate that psychophysiological parameters and agility performance are age-dependent, with older athletes demonstrating statistically better results in various agility tests. The significant improvement in short-term visual memory and choice reaction in 11-12-year-old karate practitioners is attributed not only to their age but also to the influence of specific training tasks incorporating martial arts elements. Keywords: sensorimotor skills, psychophysiology, coordination, agility, novice, karate, study.

БИОМЕХАНИЧЕСКИЕ ХАРАКТЕРИСТИКИ ЦИКЛИЧЕСКИХ ЛОКОМОЦИЙ ЧЕЛОВЕКА В ИССЛЕДОВАНИЯХ С РАЗЛИЧНЫМИ НАЗЕМНЫМИ МОДЕЛЯМИ АНТИ- И ОРТОСТАТИЧЕСКОЙ ГИПОКИНЕЗИИ

The paper reports the results of comparative analysis of the kinematic and electromyographic data about human locomotions before and after head-down and orthostatic bed rest of varying length, and successive exposure. We analyzed 3 experimental series, i.e. 21-d head-down bed rest at –6˚(HDBR) reproducing the physiological effects of microgravity, 14-d orthostatic bed rest at +9.6˚ (OBR) reproducing the lunar gravity effects and sequential exposure to 3-d HDBR and 7-d OBR reproducing a mission to the Moon. Locomotions consisted of walking at 60 steps/min and running at the 10 km/h along the horizontal plane, and walking at 3.5 km/h along an inclined plane. All hyporkinesia models unfailingly caused marked changes in kinematics and motor movements. Both types of hypokinesia affected intramuscular and intermuscular coordination as in the gravity-dependent, so flexor muscles of the ankle and knee joint. OBR had a more distinct effect on locomotion biomechanics in comparison with the baseline data. Walking along the inclined plane was characterized by significant changes equally in kinematics and EMG. In addition to changes of the external walking structure, the sequence of 3-d HDBR and 7-d OBR also redistributed the specific input to locomotion of the leg, thigh and specific muscles.

Alterations in the preferred direction of individual arm muscle activation after stroke.

Stroke survivors have challenges appropriately coordinating the multiple muscles, resulting in a deficit in motor control. Therefore, comprehending the mechanism underlying abnormal intermuscular coordination becomes crucial in developing effective rehabilitation strategies. Quantitative analyses have been employed at pairwise or multi-dimensional levels to understand the underlying mechanism of abnormal intermuscular coordination and its relationship to motor impairment. However, how alterations in individual muscle activation contribute to abnormal intermuscular coordination, motor impairment, and motor performance remains unclear. Thus, we investigated the alterations in the preferred direction of individual muscles after stroke and their relationship with stroke-induced changes in intermuscular coordination, clinical motor impairment, and qualities of motor performance during isometric force generation in the upper extremity. Twenty-four stroke survivors and six age-matched controls were recruited and performed isometric force target matches while recording electromyographic signals from eight upper limb muscles. We determined the preferred activation direction of each muscle, evaluated abnormal intermuscular coordination through a muscle synergy analysis, assessed motor impairment using upper extremity Fugl-Meyer Assessment scores, and examined motor performance characteristics defined by force trajectory features. The post-stroke alterations in the preferred direction of the brachioradialis, anterior, middle, and posterior deltoid were correlated with the motor impairment level and attributed to the changes in muscle synergy characteristics. Only alterations in the preferred direction of the brachioradialis and posterior deltoid activation in forward-backward and upward-downward axes were associated with the qualities of isometric force generation, respectively. These findings imply that alterations in the preferred direction of individual muscle activation contribute to various aspects of motor deficit following stroke. This insight may serve as a foundation for the development of innovative stroke neurorehabilitation approaches that take into account specific attributes of individual muscle activation, including their preferred activation direction.

Developing new intermuscular coordination patterns through an electromyographic signal-guided training in the upper extremity

BackgroundMuscle synergies, computationally identified intermuscular coordination patterns, have been utilized to characterize neuromuscular control and learning in humans. However, it is unclear whether it is possible to alter the existing muscle synergies or develop new ones in an intended way through a relatively short-term motor exercise in adulthood. This study aimed to test the feasibility of expanding the repertoire of intermuscular coordination patterns through an isometric, electromyographic (EMG) signal-guided exercise in the upper extremity (UE) of neurologically intact individuals.Methods10 participants were trained for six weeks to induce independent control of activating a pair of elbow flexor muscles that tended to be naturally co-activated in force generation. An untrained isometric force generation task was performed to assess the effect of the training on the intermuscular coordination of the trained UE. We applied a non-negative matrix factorization on the EMG signals recorded from 12 major UE muscles during the assessment to identify the muscle synergies. In addition, the performance of training tasks and the characteristics of individual muscles’ activity in both time and frequency domains were quantified as the training outcomes.ResultsTypically, in two weeks of the training, participants could use newly developed muscle synergies when requested to perform new, untrained motor tasks by activating their UE muscles in the trained way. Meanwhile, their habitually expressed muscle synergies, the synergistic muscle activation groups that were used before the training, were conserved throughout the entire training period. The number of muscle synergies activated for the task performance remained the same. As the new muscle synergies were developed, the neuromotor control of the trained muscles reflected in the metrics, such as the ratio between the targeted muscles, number of matched targets, and task completion time, was improved.ConclusionThese findings suggest that our protocol can increase the repertoire of readily available muscle synergies and improve motor control by developing the activation of new muscle coordination patterns in healthy adults within a relatively short period. Furthermore, the study shows the potential of the isometric EMG-guided protocol as a neurorehabilitation tool for aiming motor deficits induced by abnormal intermuscular coordination after neurological disorders.Trial registrationThis study was registered at the Clinical Research Information Service (CRiS) of the Korea National Institute of Health (KCT0005803) on 1/22/2021.

Network of muscle fibers activation facilitates inter-muscular coordination, adapts to fatigue and reflects muscle function

Fundamental movement patterns require continuous skeletal muscle coordination, where muscle fibers with different timing of activation synchronize their dynamics across muscles with distinct functions. It is unknown how muscle fibers integrate as a network to generate and fine tune movements. We investigate how distinct muscle fiber types synchronize across arm and chest muscles, and respond to fatigue during maximal push-up exercise. We uncover that a complex inter-muscular network of muscle fiber cross-frequency interactions underlies push-up movements. The network exhibits hierarchical organization (sub-networks/modules) with specific links strength stratification profile, reflecting distinct functions of muscles involved in push-up movements. We find network reorganization with fatigue where network modules follow distinct phase-space trajectories reflecting their functional role and adaptation to fatigue. Consistent with earlier observations for squat movements under same protocol, our findings point to general principles of inter-muscular coordination for fundamental movements, and open a new area of research, Network Physiology of Exercise.

Comparative analysis of motor functional asymmetry indicators in athletes of cyclic sports, martial arts, and esports

Background and Study Aim. Understanding and assessing functional asymmetry among athletes is pivotal, as it has the potential to reveal hidden strengths and weaknesses that can profoundly influence competitive performance. Study Aim: to perform a comparative analysis of functional asymmetry indicators among athletes in cyclic sports (short track), martial arts (karate, taekwondo), and esports (CS:GO). Material and Methods. The study involved athletes of martial arts (n=10, age 18.9±0.12, experienced athletes), elite players of semi-professional CS:GO teams (n=10, age 19.2±0.50), and short track athletes (n=10, age 19±0.09, experienced athletes). The functional asymmetry was determined using a specialized program for iOS tablets. Results. Esports athletes a higher number of taps during the test within a given unit of time. They also exhibit shorter reaction times and have briefer tap durations using both their right and left hands, in comparison to athletes specializing in other disciplines. Across all three specializations, athletes display minimal disparities between their right and left hands regarding tap count, reaction time, and tap duration at each of the six test stages. The variance in tap count ranges from 0 to 1.40 times, while reaction time differs by 0 to 2.33 milliseconds, and tap duration varies between 1.53 to 8.69 milliseconds. Conclusions. The exploration of motor functional asymmetry holds significant importance in analyzing the motor skills and perceptual-motor capabilities of athletes across diverse sports and proficiency levels. A comparison of functional asymmetry metrics among athletes from three distinct specializations affirmed the similarity in outcomes across all measures. This suggests that elite athletes possess a heightened level of movement coordination and symmetry in their execution between their right and left hands. The advanced level of sports training contributes to the balanced enhancement of intermuscular coordination, further positively impacting visual-motor reaction times.

Expanding the repertoire of intermuscular coordination patterns and modulating intermuscular connectivity in stroke-affected upper extremity through electromyogram-guided training: a pilot study.

Abnormal intermuscular coordination is a major stroke-induced functional motor impairment in the upper extremity (UE). Previous studies have computationally identified the abnormalities in the intermuscular coordination in the stroke-affected UE and their negative impacts on motor outputs. Therefore, targeting the aberrant muscle synergies has the potential as an effective approach for stroke rehabilitation. Recently, we verified the modifiability of the naturally expressed muscle synergies of young able-bodied adults in UE through an electromyographic (EMG) signal-guided exercise protocol. This study tested if an EMG-guided exercise will induce new muscle synergies, alter the associated intermuscular connectivity, and improve UE motor outcome in stroke-affected UE with moderate-to-severe motor impairment. The study used the six-week isometric EMG signal-guided exercise protocol that focused on independently activating two specific muscles, the biceps and brachioradialis, to develop new muscle activation groups. The study found that both the stroke and age-matched, able-bodied groups were able to develop new muscle coordination patterns through the exercise while habitual muscle activation was still available, which led to improvements in the motor control of the trained arm. In addition, the results provided preliminary evidence of increased intermuscular connectivity between targeted muscles in the beta-band frequencies for stroke patients after training, suggesting a modulation of the common neural drive. These findings suggest that our isometric exercise protocol has the potential to improve stroke survivors' performance of UE in their activities in daily lives (ADLs) and, ultimately, their quality of life through expanding their repertoire of intermuscular coordination.Clinical Relevance- This study shows the feasibility of expanding the intermuscular coordination pattern in stroke-affected UE through an isometric EMG-guided exercise which positively affects task performance and intermuscular connectivity.

Comparative Analysis of Muscle Synergy between Patients with Shoulder Impingement Syndrome and Healthy Controls: A Preliminary Study.

Shoulder impingement syndrome can be caused by a muscle imbalance around the shoulder joint. It would be beneficial for therapy to implement rehabilitation exercises based on intermuscular coordination in order to achieve muscle balance. This study presents the muscle synergy characteristics of patients with shoulder impingement syndrome, which can be used to develop rehabilitation exercises. During pick and place task, the muscle synergy obtained from eight shoulder muscles in patients and healthy subjects was compared. The experimental results revealed that patients have low contributed muscle synergy structures for the serratus anterior and infraspinatus.Clinical relevance- This proposes that patients with shoulder impingement syndrome may have abnormal muscle synergy structure which can be used for assessment.

Long-Term Neurophysiological Adaptations to Strength Training: A Systematic Review With Cross-Sectional Studies.

Santos, PDG, Vaz, JR, Correia, J, Neto, T, and Pezarat-Correia, P. Long-term neurophysiological adaptations to strength training: a systematic review with cross-sectional studies. J Strength Cond Res XX(X): 000-000, 2023-Neuromuscular adaptations to strength training are an extensively studied topic in sports sciences. However, there is scarce information about how neural mechanisms during force production differ between trained and untrained individuals. The purpose of this systematic review is to better understand the differences between highly trained and untrained individuals to establish the long-term neural adaptations to strength training. Three databases were used for the article search (PubMed, Web of Science, and Scopus). Studies were included if they compared groups of resistance-trained with untrained people, aged 18-40 year, and acquired electromyography (EMG) signals during strength tasks. Twenty articles met the eligibility criteria. Generally, strength-trained individuals produced greater maximal voluntary activation, while reducing muscle activity in submaximal tasks, which may affect the acute response to strength training. These individuals also presented lower co-contraction of the antagonist muscles, although it depends on the specific training background. Global intermuscular coordination may be another important mechanism of adaptation in response to long-term strength training; however, further research is necessary to understand how it develops over time. Although these results should be carefully interpreted because of the great disparity of analyzed variables and methods of EMG processing, chronic neural adaptations seem to be decisive to greater force production. It is crucial to know the timings at which these adaptations stagnate and need to be stimulated with advanced training methods. Thus, training programs should be adapted to training status because the same stimulus in different training stages will lead to different responses.

Effects of Law Enforcement Load Carriage Systems on Muscle Activity and Coordination during Walking: An Exploratory Study.

Law enforcement officers (LEOs) commonly wear a duty belt (DB) or tactical vest (TV) and from prior findings, these forms of load carriage (LC) likely alter muscular activity. However, studies on the effects of LEO LC on muscular activity and coordination are limited in the current literature. The present study examined the effects of LEO load carriage on muscular activity and coordination. Twenty-four volunteers participated in the study (male = 13, age = 24.5 ± 6.0 years). Surface electromyography (sEMG) sensors were placed on the vastus lateralis, biceps femoris, multifidus, and lower rectus abdominus. Participants completed treadmill walking for two load carriage conditions (duty belt and tactical vest) and a control condition. Mean activity, sample entropy and Pearson correlation coefficients were computed for each muscle pair during the trials. The duty belt and tactical vest resulted in an increase in muscle activity in several muscles; however, no differences between the duty belt and tactical vest were found. Consistently across the conditions, the largest correlations were observed between the left and right multifidus (r = 0.33-0.68) and rectus abdominus muscles (0.34-0.55). There were statistically small effects (p < 0.05, η2 = 0.031 to 0.076) of the LC on intermuscular coordination. No effect (p > 0.05) of the LC on sample entropy was found for any muscle. The findings indicate that LEO LC causes small differences in muscular activity and coordination during walking. Future research should incorporate heavier loads and longer durations.

The Effects of Kinesio Taping® on Muscle Interplay within the Lumbo–Pelvic–Hip Complex: A Randomized Placebo-Controlled Trial

Coordination of muscle activity is determined by the recruitment order of agonists and synergists that results from their onset times. Motor recruitment deficits are possible. This study examined the acute and prolonged effects of three different techniques of the kinesio taping method in optimizing the intermuscular coordination within the lumbo-pelvic-hip complex. The sample consisted of 56 healthy participants of both genders, randomly divided into equal groups by kinesio taping muscle facilitation, muscle inhibition and functional correction technique, and placebo kinesio taping condition. The onsets of the ipsilateral and contralateral erector spinae muscles, in relation to the semitendinosus muscle of the tested leg, were measured using the surface electromyography, during the active performance of the prone hip extension test. Time span was also determined. Measurements were performed at baseline, 60 min, and 48 h post-intervention. For the control group, we did not find statistically significant differences in the onset between the measurement points (p > 0.05), while in the experimental groups, there was a significant delay in the onset of the contralateral erector spinae (p < 0.001) in the second and third measurement points. These results indicate that the kinesio taping method can optimize the intermuscular coordination, with the potential for primary injury prevention.

Adapting the pantograph limb: Differential robustness of fore- and hindlimb kinematics against genetically induced perturbation in the neural control networks and its evolutionary implications

The evolutionary transformation of limb morphology to the four-segmented pantograph of therians is among the milestones of mammalian evolution. But, it is still unknown if changes of the mechanical limb function were accompanied by corresponding changes in development and sensorimotor control. The impressive locomotor performance of mammals leaves no doubt about the high integration of pattern formation, neural control and mechanics. But, deviations from normal intra- and interlimb coordination (spatial and temporal) become evident in the presence of perturbations. We induced a perturbation in the development of the neural circuits of the spinal cord of mice (Mus musculus) using a deletion of the Wilms tumor suppressor gene Wt1 in a subpopulation of dI6 interneurons. These interneurons are assumed to participate in the intermuscular coordination within the limb and in left-right-coordination between the limbs. We describe the locomotor kinematics in mice with conditional Wt1 knockout and compare them to mice without Wt1 deletion. Unlike knockout neonates, knockout adult mice do not display severe deviations from normal (=control group) interlimb coordination, but the coordinated protraction and retraction of the limbs is altered. The forelimbs are more affected by deviations from the control than the hindlimbs. This observation appears to reflect a different degree of integration and resistance against the induced perturbation between the limbs. Interestingly, the observed effects are similar to locomotor deficits reported to arise when sensory feedback from proprioceptors or cutaneous receptors is impaired. A putative participation of Wt1 positive dI6 interneurons in sensorimotor integration is therefore considered.

Кореляційні взаємозв’язки спеціальної фізичної та технічної підготовленості тхеквондистів

Purpose: to experimentally determine the correlational relationships between the physical and technical preparation of taekwondo players 12–14 years old. Material and methods. During the work, the following research methods were used: theoretical analysis and generalization of scientific and methodological literature and the Internet, pedagogical observation, pedagogical testing, pedagogical research, methods of mathematical statistics. 30 athletes specializing in taekwondo, age 12–14 years old, athlete qualification 1–2 grade, took part in the study. Results: at the beginning of the stage of basic training, statistically significant correlations were found between: speed-power index and the frequency of execution of side kicks to the torso after 10 seconds with the left leg r=0,50; a swing with the left leg forward in 15 s has a high degree of correlation with the frequency of lateral kicks to the torso in 10 s alternately with both legs r=0,54, the frequency of lateral kicks to the torso in 10 s with the left leg – r = 0,63 and the right – r=0,50 and the inverse relationship with a side impact with deployment in opposite directions in 15 seconds to the upper level – r=-0,53; squat on one leg in 30 s on the left leg – from fencing in 10 s to the upper level with the left leg r=0,62 and right leg with a side kick with a 360° rotation in 15 s with the right leg r=0,63; indicators of longitudinal and transverse splits have inverse relationships with fencing in 10 seconds to the upper level with the left leg – r=-0,67, r=-0,56, respectively. Correlation analysis of relationships of the level of manifestation of indicators of special physical and technical preparation at the end and at the beginning of the stage of basic training is marked by an increase in the number of high degrees of correlation relationships from 9 to 21. It was found that the speed-strength index has the largest number of high relationships – 6 (r=0,50–0,72), this is due to the fact that at the end of the stage of basic training, the improvement of technical fitness indicators occurs due to the improvement of special physical fitness, in particular, due to the manifestation of speed and strength abilities and intermuscular coordination, which is reflected in the ability of athletes to control their movements. Conclusions. The research established that at the beginning of the stage of basic training and technique formation, the manifestation of flexibility affects 10 medium-level correlations (r=0,31–0,46) and 2 high inverse correlations (r=-0,67, -0,56), and at the end of the stage, the manifestation of speed-power abilities and intermuscular coordination is of crucial importance. Taekwondo athletes require training that improves aerobic capacity, resulting in the development of oxygen systems in order to perform as efficiently as possible during a bout consisting of 3 rounds of 2 minutes with only 1 minute of rest for partial recovery, energy resources. However, work under significant hypoxia, that is, in anaerobic conditions, also plays a large role in a sports match.

Relevance of Upper Limb Muscle Synergies to Dynamic Force Generation: Perspectives on Rehabilitation of Impaired Intermuscular Coordination in Stroke.

This study investigated the impact of stroke on the control of upper limb endpoint force during isokinetic exercise, a dynamic force-generating task, and its association with stroke-affected muscle synergies. Three-dimensional upper limb endpoint force and electromyography of shoulder and elbow muscles were collected from sixteen chronic stroke survivors and eight neurologically intact adults. Participants were instructed to control the endpoint force direction during three-dimensional isokinetic upper limb movements. The endpoint force control performance was quantitatively evaluated in terms of the coupling between forces in orthogonal directions and the complexity of the endpoint force. Upper limb muscle synergies were compared between participants with varying levels of endpoint force coupling. The stroke survivors generating greater force abnormality than the others exhibited interdependent activation profiles of shoulder- and elbow-related muscle synergies to a greater extent. Based on the relevance of synergy activation to endpoint force control, this study proposes isokinetic training to correct the abnormal synergy activation patterns post-stroke. Several ideas for implementing effective training for stroke-affected synergy activation are discussed.

Detection of intermuscular coordination based on the causality of empirical mode decomposition.

Considering the stochastic nature of electromyographic (EMG) signals, nonlinear methods may be a more accurate approach to study intermuscular coordination than the linear approach. The aims of this study were to assess the coordination between two ankle plantar flexors using EMG by applying the causal decomposition approach and assessing whether the intermuscular coordination is affected by the slope of the treadmill. The medial gastrocnemius (MG) and soleus muscles (SOL) were analyzed during the treadmill walking at inclinations of 0°, 5°, and 10°. The coordination was evaluated using ensemble empirical mode decomposition, and the causal interaction was encoded by the instantaneous phase dependence of time series bi-directional causality. To estimate the mutual predictability between MG and SOL, the cross-approximate entropy (XApEn) was assessed. The maximal causal interaction was observed between 40 and 75Hz independent of inclination. XApEn showed a significant decrease between 0° and 5° (p = 0.028), between 5° and 10° (p = 0.038), and between 0° and 10° (p = 0.014), indicating an increase in coordination. Thus, causal decomposition is an appropriate methodology to study intermuscular coordination. These results indicate that the variation of loading through the change in treadmill inclination increases the interaction of the shared input between MG and SOL, suggesting increased intermuscular coordination.