Antagonist Muscles Research Articles

Surface Electromyography for the Diagnosis of Tremor Syndrome: A Study of 97 Patients

Abstract Background and Objectives: Tremor is one of the most frequent movement disorders encountered in clinical practice with heterogeneous phenomenology and etiology. Surface electromyography (SEMG) is a noninvasive and reproducible test that can diagnose tremor syndromes. Methods: In this retrospective study, the clinical and electrophysiologic records of 97 consecutive patients with tremor syndromes who visited our movement disorder clinic between January 2023 and March 2024 were examined. Results: In our study, 28.8% (n = 28) of patients were of essential tremor (ET) syndrome. SEMG of ET syndrome patients showed synchronous bursts in 71.4% (n = 20), alternating bursts in 10.7% (n = 3), synchronous bursts with co-contraction of agonist and antagonist muscles in 10.7% (n = 3), and both synchronous and alternating bursts in 3.6% (n = 1) of patients. Tremor–ataxia syndrome formed 21.6% (n = 21) of our study population, with 71.4% (n = 15) of patients showing synchronous bursts and co-contraction and 28.6% (n = 6) patients having alternating bursts. Moreover, 12.3% (n = 12) patients were of parkinsonian tremor, of whom alternating bursts were present in 75% (n = 9) and synchronous bursts with co-contraction were present in 25% (n = 3) of patients. In addition, 11.3% (n = 11) of patients had dystonic tremor (DT), of whom 81.8% (n = 9) had synchronous bursts and co-contraction and 18.2% (n = 2) had alternating bursts. Conclusions: Synchronous bursts with co-contraction suggestive of DT were observed in most patients with tremor–ataxia syndrome and a small number of patients with ET syndrome. Our data suggests that SEMG helps differentiate these two clinical syndromes, which is difficult in a clinical setting.

Supraspinal contributions to defective antagonistic inhibition and freezing of gait in Parkinson's disease.

The neuromuscular circuit mechanisms of freezing of gait in Parkinson's disease have received little study. Technological progress enables researchers chronically to sense local field potential activity of the basal ganglia in patients while walking. To study subthalamic activity and the circuit processes of supraspinal contributions to spinal motor integration, we recorded local field potentials, surface EMG of antagonistic leg muscles and gait kinematics in patients while walking and freezing. To evaluate the specificity of our findings, we controlled our findings to internally generated volitional stops. We found specific activation-deactivation abnormalities of oscillatory activity of the subthalamic nucleus both before and during a freeze. Furthermore, we were able to show with synchronization analyses that subthalamo-spinal circuits entrain the spinal motor neurons to a defective timing and activation pattern. The main neuromuscular correlates when turning into freezing were as follows: (i) disturbed reciprocity between antagonistic muscles; (ii) increased co-contraction of the antagonists; (iii) defective activation and time pattern of the gastrocnemius muscle; and (iv) increased subthalamo-muscular coherence with the gastrocnemius muscles before the freeze. Beyond the pathophysiological insights into the supraspinal mechanisms contributing to freezing of gait, our findings have potential to inform the conceptualization of future neurorestorative therapies.

Deciphering the Refined Musculature of the Brow Area in Asians by Micro-Computed Tomography.

The brow area is an important aesthetic unit. Accurate anatomical understanding of the brow is important for clinical treatments related to this region. Due to the complexity of the brow area and limitations of methods, there are still some controversies regarding its musculature description. This article aims to reveal the detailed musculature using micro-computed tomography (micro-CT) combined with histological staining. Eight fresh cadaver (16 hemifaces) were obtained. Eight hemifaces were processed with phospho-tungstic acid contrast staining for micro-CT scanning and reconstruction. The other corresponding 8 hemifaces were prepared with Masson staining. The orbicularis oculi muscle (OOM), frontalis muscle (FM), depressor supercilii (DS) and procerus muscle (PM) were situated superficially. The FM terminated and connected with its antagonistic muscles at 2-5 mm above the brow but the fusion line descended in lateral third. The corrugator supercilii muscle (CSM) originated from the periosteum, extending laterally and superficially. During its course, it mainly penetrated the FM. CSM had broad subcutaneous insertion, covering about 77.9% ± 7.5% of the hairy brow. CSM fibers connected to the subcutaneous fiber septa to directly transmit contraction force. The soft tissue on the lateral side of the brow was looser than that on the medial side. Our study deepens the understanding of the precise anatomy of the brow area and helps guide clinical practice.

Effects of Different Stretching Modalities on the Antagonist and Agonist Muscles on Isokinetic Strength and Vertical Jump Performance in Young Men.

Montalvo, S, Gonzalez, MP, Dietze-Hermosa, MS, Martinez, A, Rodriguez, S, Gomez, M, Ibarra-Mejia, G, Tan, E, and Dorgo, S. Effects of different stretching modalities on the antagonist and agonist muscles on isokinetic strength and vertical jump performance in young men. J Strength Cond Res XX(X): 000-000, 2024-Exercise warm-up may include static or dynamic stretching, impacting performance differently. This study investigated the effects of various stretching protocols on isokinetic strength, muscular activity, and vertical jump performance. Sixteen subjects, divided evenly between trained and untrained groups, underwent 8 distinct stretching conditions in random order. Outcomes measured included isokinetic knee extension and flexion torque and power, muscular activity (vastus lateralis, vastus medialis, and biceps femoris), and jump performance (jump height and modified reactive strength index [RSImod]). Responses to the stretching conditions were analyzed using a mixed-methods approach. For isokinetic knee extension, dynamic stretching of both agonist and antagonist (DY-AG-ANT) and combined dynamic agonist with static antagonist stretching (DY-AG ST-ANT) produced significant improvements. Dynamic stretching of both agonist and antagonist increased peak torque by 12.72% and average torque by 30.80%, while DY-AG ST-ANT increased peak torque by 15.61% and average torque by 41.06%. Muscular activity also improved significantly; DY-AG ST-ANT increased EMG activity of the vastus lateralis by 29.43% and vastus medialis by 70.75%. Biceps femoris saw a 33.18% increase with DY-AG and a 22.15% increase with ST-AG. Countermovement jump height improved with DY-AG-ANT (12.6%) and static antagonist (ST-ANT) conditions (11.3%) ( p < 0.05). Dynamic stretching of both agonist and antagonist also enhanced average power knee extension by 32.41%, while ST-AG DY-ANT improved it by 31.09% ( p < 0.05). Dynamic stretching, especially when combined with static stretching, optimizes isokinetic strength, muscular activity, and jump height. Coaches should incorporate dynamic stretching, alone or with static antagonist stretching, to maximize performance.

Intermittent hypoxia enhances voluntary activation and reduces performance fatigability during repeated lower limb contractions.

Prior research has highlighted the therapeutic benefits of acute intermittent hypoxia (AIH) in enhancing motor performance after motor incomplete spinal cord injury and in able-bodied individuals. While studies in rodents and humans indicate that AIH may facilitate motor excitability, the relationship between excitability changes and functional performance remains unclear. Additionally, discrepancies in the effects of AIH on excitability in able-bodied individuals merit further investigation. Understanding the concurrent impact of repetitive AIH on voluntary activation and spinal reflex excitability may clarify the functional implications of AIH for muscle force production. High voluntary activation is vital for sustaining torque production during activities that require repeated muscle contractions. We hypothesized that repetitive AIH would attenuate declines in both voluntary activation and maximum torque production typically observed during fatiguing contractions. To test this hypothesis, we examined the effects of four consecutive days of AIH on voluntary activation and torque generation during repeated maximal plantar flexion contractions. We assessed changes in voluntary activation using the central activation ratio (CAR) by calculating the ratio of voluntary torque to the torque produced with supramaximal electrical stimulation. Consistent with our hypothesis, we show that repetitive AIH significantly increases both CAR and peak torque during fatiguing contractions. We did not observe any changes in resting spinal reflex excitability or antagonist muscle coactivation during the fatiguing contractions post-AIH. Together, these findings suggest that repetitive AIH reduces performance fatigability through enhanced descending neural drive. Optimizing voluntary activation is critical for facilitating the recovery of functional walking skills after neurological injury.

Effect of fatigue on intermuscular EMG-EMG coupling during bench press exercise at 60% 1RM workload in males.

To explore the neuromuscular control mechanism and quantifying the fatigue response during bench press exercise is important references to prescribe an appropriate exercise program. However, current literature struggles to provide a concrete conclusion on the changes of intermuscular EMG-EMG coupling between synergistic and antagonist muscles during the exercise. Thus, the current study was designed to reveal fatigue-related changes of intermuscular EMG-EMG coupling during bench press exercise. Thirty-one healthy male participants performed a bench press exercise on the Smith machine at 60% One Repetition Maximum (1RM) workload to exhaustion, while surface electromyographic signals (sEMG) were collected from triceps brachii (TB), biceps brachii (BB), anterior deltoid (AD), posterior deltoid (PD), and pectoralis major (PM). Surface EMG signals were divided into the first half and second half of the bench press exercise. Phase synchronization index (PSI) was calculated between sEMG of synergistic muscle pairs AD-TB, AD-PM and antagonist muscle pairs BB-TB, AD-PD. EMG power of TB, AD, PD, PM muscles in alpha (8-12 Hz) frequency band and EMG power of each muscle in beta (15-35 Hz), and gamma (35-60 Hz) frequency bands were all increased during the second half of contraction compared with the first half of contraction. PSI of gamma frequency band was significantly decreased in BB-TB muscle pair while EMG-EMG coupling of AD-TB in gamma frequency band was significantly increased during the second half of contraction compared to the first half of contraction. The results indicated a decrease of interconnection between synchronized cortical neurons and the motoneuron pool of BB and TB, and an increase of interconnection between AD-TB muscles during fatiguing bench press exercise at 60% 1RM workload. The changes of intermuscular coupling may be related to the supraspinal modulations to compensate for the decrease of muscle force as well as a result of unbalanced changes of agonist and antagonist muscle contractility.

Physical therapy in a patient with viral -encephalitis hemi-paresis: A Case report

The purpose of the rehabilitation program is to improve motor skills, coordination, sensory system, mobilization and other existing disorders to achieve activity of daily living (ADL). Physical therapy as part of the multidisciplinary approach can provide core stability exercises, muscular facilitation and stimulation of motion of the upper and lower extremities, balance exercises and mobility exercises, as well as strengthening exercises with PNF facilitation and active stimulation techniques and using the patient's body weight as a training burden. Bobath approach and facilitation exercise can reduce spasticity by strengthening the antagonist muscles. MMT right upper extremity 3/5, left upper extremity 4/5, right lower extremity 2/5, and left lower extremity 3/5. Ashworth scale right upper extremity 1/4, right lower extremity 2/4, and left lower extremity 1/4. Clonus is reduced, the patient can stand with maximum support without clonus for 10 minutes. Trunk impairment scale 12/23 and Barthel index 65/100. Anthropometric examination showed differences in the circumference of the lower extremities, namely the right patella circumference 34-32 cm left, right upper leg 39 cm-left 37 cm, and left lower leg 29-24 cm. Mobilize the patient to a laying position with minimal assistance. Mobilization of the patient is being able to sit with minimal assistance, namely stabilization in the pelvis, sitting to standing with moderate support, which is supported at the knee bilaterally, and standing with support at the knee and pelvic for 10 minutes. This case report concludes that although physiotherapy is done late with strengthening exercise and core stability strengthening techniques, lying down strengthening exercise, it can improve motor skills, coordination, which in turn will increase the patient's independence in carrying out functional activities and ADLs.

Rehabilitation technique of proprioceptive neuromuscular facilitation applied to volleyball vertical jump: A randomized double blinded cross-over clinical trial

Objectivecompare the acute effect of lower limb stretching exercises with proprioceptive neuromuscular facilitation (PNF) on the antagonist and agonist muscle groups in the execution of a vertical jump (VJ). Methoda randomized, double-blind, crossover clinical trial was conducted involving 30 male volleyball athletes. Group A engaged in PNF on the antagonist muscles, while Group B applied the same method to the agonist muscles. Following a 48-h washout period, the interventions were swapped between the respective groups. Both groups underwent assessments averaging three countermovement vertical jumps (CVJ) with hands on hips and three VJ with arms free. Measurement was taken using the Encoder – Ergonauta I, with over 1500 jumps recorded. The participants were evaluated for their level of flexibility and VJ performance using the Jump Sigma Index application. Resultsan acute decrease in average performance was identified, amounting to 3.86 % for the CMJ with hands on hips and 3.06% for the CVJ with free hands, following PNF in the agonists. Conclusionthere was no statistical difference between the means before and after the intervention when PNF was applied to the antagonistic hamstring muscles. The CVJ modalities with hands on hips and with free hands presented statistically similar indices. The study suggests that there is no impediment to the implementation of warm-up or training protocols that involve stretching in the antagonistic muscles. Further research will be relevant to better clarify the relationship between the effects of stretching on antagonistic muscle groups and to formalize future protocols.

A rare presentation of stiff-person syndrome with a nonspecific focal myositis: A case report

Introduction. The stiff-person syndrome (SPS) is a rare disease whose incidence is estimated at approximately 1 in a million individuals in the general population. Diagnosis relies on a combination of clinical, immunological, and electromyographic items. We present the case of a patient diagnosed with the idiopathic SPS, initially misdiagnosed as focal paravertebral myositis. Case presentation. A 36-year-old patient was referred to us for the investigation of subacute dorsal myalgias. The patient reported a severe torticollis seven months ago, which resolved spontaneously after one month, and some episodes of back stiffness. On examination, the patient was afebrile, had hyperlordosis with a paravertebral contracture and tenderness. Neurological and cognitive examinations were normal. C-reactive Protein was at 137 mg/l. The rest of laboratory investigations, including creatine phosphokinase (CPK), were within normal range. Spinal MRI revealed T2 hyperintensity in the semispinalis muscle, erector spinae muscle, trapezius muscle, as well as the intervertebral muscles. Therefore, focal paravertebral myositis was suspected. The electromyogram (EMG) revealed the presence of a continuous motor unit activity in agonist and antagonist muscles, suggestive of stiff-person syndrome. Antinuclear antibodies, anti-glutamic acid decarboxylase 65 and onconeuronal antibodies were negative. Analysis of the cerebrospinal fluid, including anti-glutamic acid decarboxylase 65 test, was normal. We noticed that the paravertebral contracture became less noticeable when the patient was commenced on diazepam. Diagnosis of SPS was established according to Dalakas criteria. Investigations for an underlying neoplasm, were normal. Associated autoimmune disorders have been ruled out. The MRI description was rather explained by the continuous contraction of the affected muscles. Treatment included diazepam, baclofen, intravenous immunoglobulin and corticosteroids. The patient showed important signs of improvement. Conclusion. SPS is a rare condition whose diagnosis can be delayed. Recognizing and managing SPS as early as possible is crucial. It is based on clinical reasoning, imaging, biological features and EMG.

Analysis of Wavelet Coherence in Calf Agonist-Antagonist Muscles during Dynamic Fatigue.

Dynamic muscle fatigue during repetitive movements can lead to changes in communication between the central nervous system and peripheral muscles. This study investigated these changes by examining electromyogram (EMG) characteristics from agonist and antagonist muscles during a fatiguing task. Twenty-two healthy male university students (age: 22.92 ± 2.19 years) performed heel raises until fatigue. EMG signals from lateral gastrocnemius (GL) and tibialis anterior (TA) muscles were processed using synchrosqueezed wavelet transform (SST). Root mean square (RMS), mean frequency (MF), power across frequency ranges, wavelet coherence, and co-activation ratio were computed. During the initial 80% of the task, RMS and EMG power increased for both muscles, while MF declined. In the final 20%, GL parameters stabilized, but TA showed significant decreases. Beta and gamma intermuscular coherence increased upon reaching 60% of the task. Alpha coherence and co-activation ratio remained constant. Results suggest that the central nervous system adopts a differentiated control strategy for agonist and antagonist muscles during fatigue progression. Initially, a coordinated "common drive" mechanism enhances both muscle groups' activity. Later, despite continued increases in muscle activity, neural-muscular coupling remains stable. This asynchronous, differentiated control mechanism enhances our understanding of neuromuscular adaptations during fatigue, potentially contributing to the development of more targeted fatigue assessment and management strategies.

Voluntary co-contraction of ankle muscles alters motor unit discharge characteristics and reduces estimates of persistent inward currents.

Motoneuronal persistent inward currents (PICs) are facilitated by neuromodulatory inputs but are highly sensitive to local inhibitory circuits. Estimates of PICs are reduced by group Ia reciprocal inhibition, and increased with the diffuse actions of neuromodulators released during remote muscle contraction. However, it remains unknown how motoneurons function in the presence of simultaneous excitatory and inhibitory commands. To probe this topic, we investigated motor unit discharge patterns and estimated PICs during voluntary co-contraction of ankle muscles, which simultaneously demands the contraction of agonist-antagonist pairs. Twenty participants performed triangular ramps of both co-contraction (simultaneous dorsiflexion and plantar flexion) and isometric dorsiflexion to a peak of 30% of their maximum muscle activity from a maximal voluntary contraction. Motor unit spike trains were decomposed from high-density surface EMG activity recorded from tibialis anterior using blind source separation algorithms. Voluntary co-contraction altered motor unit discharge rate characteristics. Discharge rate at recruitment and peak discharge rate were modestly reduced (∼6% change; P<0.001; d=0.22) and increased (∼2% change; P=0.001, d=-0.19), respectively, in the entire dataset but no changes were observed when motor units were tracked across conditions. The largest effects during co-contraction were that estimates of PICs (ΔF) were reduced by ∼20% (4.47 vs. 5.57 pulses per second during isometric dorsiflexion; P<0.001, d=0.641). These findings suggest that, during voluntary co-contraction, the inhibitory input from the antagonist muscle overcomes the additional excitatory and neuromodulatory drive that may occur due to the co-contraction of the antagonist muscle, which constrains PIC behaviour. KEY POINTS: Voluntary co-contraction is a unique motor behaviour that concurrently provides excitatory and inhibitory synaptic input to motoneurons. Co-contraction of agonist-antagonist pairs alters agonist motor unit discharge characteristics, consistent with reductions in persistent inward current magnitude.

Altered muscle fibre activation in an antagonistic muscle pair due to perturbed afferent feedback caused by blood flow restriction

PurposeThis study aimed to better understand the coping strategy of the neuromuscular system under perturbed afferent feedback. To this end, the neuromechanical effects of transient blood flow restriction (BFR) compared to atmospheric pressure were investigated in an antagonistic muscle pair. MethodsPerceived discomfort and neuromechanical parameters (torque and high-density electromyography) were recorded during submaximal isometric ankle dorsiflexion before, during and after BFR. The tibialis anterior and gastrocnemius lateralis muscles were studied in 14 healthy young adults. ResultsDiscomfort increased during BFR and decreased to baseline level afterwards. The exerted torque and the co-activation index remained constant, whereas the EMG signal energy increased significantly during BFR. Coherence analysis of the delta band remained constant, whereas the alpha band shows an increase during BFR. Median frequency and muscle fibre conduction velocity showed a positive trend during the first minutes of BFR before significantly decreasing. Both parameters exceeded baseline values after cuff deflation. ConclusionPerturbed afferent feedback leads to altered neuromechanical parameters. We assume that increased central drive is required to maintain force output, resulting in changed muscle fibre activity. Glycolytic fast-switch fibres are only active for a short time due to oxygen deprivation and hyperacidity, but fatigue effects predominate in the long term.

Muscle short-range stiffness behaves like a maxwell element, not a spring: Implications for joint stability.

Muscles play a critical role in supporting joints during activities of daily living, owing, in part, to the phenomenon of short-range stiffness. Briefly, when an active muscle is lengthened, bound cross-bridges are stretched, yielding forces greater than what is predicted from the force length relationship. For this reason, short-range stiffness has been proposed as an attractive mechanism for providing joint stability. However, there has yet to be a forward dynamic simulation employing a cross-bridge model, that demonstrates this stabilizing role. Therefore, the purpose of this investigation was to test whether Huxley-type muscle elements, which exhibit short-range stiffness, can stabilize a joint while at constant activation. We analyzed the stability of an inverted pendulum (moment of inertia: 2.7 kg m2) supported by Huxley-type muscle models that reproduce the short-range stiffness phenomenon. We calculated the muscle forces that would provide sufficient short-range stiffness to stabilize the system based in minimizing the potential energy. Simulations consisted of a 50 ms long, 5 Nm square-wave perturbation, with numerical simulations carried out in ArtiSynth. Despite the initial analysis predicting shared activity of antagonist and agonist muscles to maintain stable equilibrium, the inverted pendulum model was not stable, and did not maintain an upright posture even with fully activated muscles. Our simulations suggested that short-range stiffness cannot be solely responsible for joint stability, even for modest perturbations. We argue that short-range stiffness cannot achieve stability because its dynamics do not behave like a typical spring. Instead, an alternative conceptual model for short-range stiffness is that of a Maxwell element (spring and damper in series), which can be obtained as a first-order approximation to the Huxley model. We postulate that the damping that results from short-range stiffness slows down the mechanical response and allows the central nervous system time to react and stabilize the joint. We speculate that other mechanisms, like reflexes or residual force enhancement/depression, may also play a role in joint stability. Joint stability is due to a combination of factors, and further research is needed to fully understand this complex system.

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.

Immediate effect of local vibration on motor unit firing behavior and muscle strength in healthy young adult males.

The aim of this study was to examine the effect of vibration on motor unit (MU) firing behavior and physical performance of antagonist muscles in healthy young adult males. Fourteen males (age = 24.3 ± 3.6years) were included in this study. There were two conditions, one in which participants received 80Hz vibration in the distal tendon of the hamstring for 30s and the control condition (no vibration). High-density surface electromyography (HD-SEMG) signals and maximal voluntary contraction (MVC) of knee extensor muscles were evaluated before and after the respective conditions and recorded from the vastus lateralis muscle during submaximal ramp-up and sustained contractions at 30% MVC. Convolution blind source separation was used to decompose the HD-SEMG signals into individual MU firing behaviors. In total, 739 MUs were detected (control; 360 MUs and vibration; 379 MUs), and a total of 312 matched MUs were identified across both submaximal contraction conditions (control: 150 MUs; vibration: 162 MUs). Vibration significantly increased the discharge rate (p = 0.047) and decreased the recruitment threshold before and after intervention (p = 0.001) but not in the control condition. Furthermore, the recruitment threshold is a factor that influences discharge rate. Significant correlations were observed between the recruitment threshold and both the ∆ discharge rate and the ∆ recruitment threshold under the vibration condition (p < 0.001). Vibration increased in the discharge rate and decreased the recruitment threshold of the antagonist muscle. These findings suggested that vibration contributes to immediate changes in the neural control of antagonist muscles.

Identifying alterations in hand movement coordination from chronic stroke survivors using a wearable high-density EMG sleeve

Objective.Non-invasive, high-density electromyography (HD-EMG) has emerged as a useful tool to collect a range of neurophysiological motor information. Recent studies have demonstrated changes in EMG features that occur after stroke, which correlate with functional ability, highlighting their potential use as biomarkers. However, previous studies have largely explored these EMG features in isolation with individual electrodes to assess gross movements, limiting their potential clinical utility. This study aims to predict hand function of stroke survivors by combining interpretable features extracted from a wearable HD-EMG forearm sleeve.Approach.Here, able-bodied (N= 7) and chronic stroke subjects (N= 7) performed 12 functional hand and wrist movements while HD-EMG was recorded using a wearable sleeve. A variety of HD-EMG features, or views, were decomposed to assess alterations in motor coordination.Main Results.Stroke subjects, on average, had higher co-contraction and reduced muscle coupling when attempting to open their hand and actuate their thumb. Additionally, muscle synergies decomposed in the stroke population were relatively preserved, with a large spatial overlap in composition of matched synergies. Alterations in synergy composition demonstrated reduced coupling between digit extensors and muscles that actuate the thumb, as well as an increase in flexor activity in the stroke group. Average synergy activations during movements revealed differences in coordination, highlighting overactivation of antagonist muscles and compensatory strategies. When combining co-contraction and muscle synergy features, the first principal component was strongly correlated with upper-extremity Fugl Meyer hand sub-score of stroke participants (R2= 0.86). Principal component embeddings of individual features revealed interpretable measures of motor coordination and muscle coupling alterations.Significance.These results demonstrate the feasibility of predicting motor function through features decomposed from a wearable HD-EMG sleeve, which could be leveraged to improve stroke research and clinical care.

The functions of leg muscles, structures and mechanisms in running.

The actions of the major human leg muscles are well established; however, the functions of these muscle actions during steady running remain unclear. Here, leg structures and mechanisms are considered in terms of their functions in meeting the task of a vehicle acting as an effective machine, supporting body weight during translation with low mechanical work demand and in supplying mechanical work economically. Legs are modelled as a sequence of linkages that predict muscle actions and reveal the varying muscle functions within the integrated leg. Work avoidance is achieved with isometric muscles and linkages that promote a sliding of the hip over the ground contact, resulting in an approximately horizontal path of the centre of mass. Economical work supply requires, for muscle with constrained power, shortening over the entire stance duration; this function is achieved by the hamstrings without disrupting the linkages resulting in work avoidance. In late stance, the two functions occur through coactivation of antagonistic muscles, providing one answer to Lombard's paradox. Quadriceps and hamstring tensions result in opposing moments about both hip and knee joints, but by doing so perform the independent yet complementary roles of work avoidance during translating weight support and economical work supply.

A coactivation strategy in anticipatory postural adjustments during voluntary unilateral arm movement while standing in individuals with bilateral spastic cerebral palsy

Individuals with bilateral spastic cerebral palsy (BSCP) reportedly has problems with anticipatory postural adjustments (APAs) while standing. However, the use of coactivation strategy in APAs in individuals with BSCP has conflicting evidence. Hence, this study aimed to investigate postural muscle activities in BSCP during unilateral arm flexion task in which postural perturbations occur in the sagittal, frontal, and horizontal planes. We included 10 individuals with BSCP with level II on the Gross Motor Function Classification System (BSCP group) and 10 individuals without disability (control group). The participants stood on a force platform and rapidly flexed a shoulder from 0° to 90° at their own timing. Surface electromyograms were recorded from the rectus femoris, medial hamstring, tibialis anterior, and medial gastrocnemius. The control group showed a mixture of anticipatory activation and inhibition of postural muscles, whereas the BSCP group predominantly exhibited anticipatory activation with slight anticipatory inhibition. Compared with the control group, the BSCP group tended to activate the ipsilateral and contralateral postural muscles and the agonist–antagonist muscle pairs. The BSCP group had a larger disturbance in postural equilibrium, quantified by the peak displacement of center of pressure during the unilateral arm flexion, than those without disability. Individuals with BSCP may use coactivation strategy, mainly the anticipatory activation of postural muscle activity, during a task that requires a selective postural muscle activity to maintain stable posture.

Sensory-motor circuit is a therapeutic target for dystonia musculorum mice, a model of hereditary sensory and autonomic neuropathy 6.

Mutations in Dystonin (DST), which encodes cytoskeletal linker proteins, cause hereditary sensory and autonomic neuropathy 6 (HSAN-VI) in humans and the dystonia musculorum (dt) phenotype in mice; however, the neuronal circuit underlying the HSAN-VI and dt phenotype is unresolved. dt mice exhibit dystonic movements accompanied by the simultaneous contraction of agonist and antagonist muscles and postnatal lethality. Here, we identified the sensory-motor circuit as a major causative neural circuit using a gene trap system that enables neural circuit-selective inactivation and restoration of Dst by Cre-mediated recombination. Sensory neuron-selective Dst deletion led to motor impairment, degeneration of proprioceptive sensory neurons, and disruption of the sensory-motor circuit. Restoration of Dst expression in sensory neurons using Cre driver mice or a single postnatal injection of Cre-expressing adeno-associated virus ameliorated sensory degeneration and improved abnormal movements. These findings demonstrate that the sensory-motor circuit is involved in the movement disorders in dt mice and that the sensory circuit is a therapeutic target for HSAN-VI.

An Assessment of the Ratio between Upper Body Push and Pull Strength in Female and Male Elite Swedish Track and Field Throwers.

Data on the strength ratio between agonist and antagonist muscles are frequently examined in sports testing, given its correlation with athletic performance. The purpose of this study was to determine the agonist-to-antagonist ratio of upper body strength in female and male elite Swedish track and field throwers using a new push (bench press) and pull (supine bench row) test device, and to determine its reliability. The study involved eight female and nine male athletes, aged 19-29 years, engaging, respectively, in discus, hammer, and shot put competitions at both national and international levels. The athletes' maximum isometric force was assessed during the bench press (push) and supine bench row (pull) exercises, respectively, using a custom-built test device. The test-retest reliability of the device was also examined. The total push-to-pull strength ratio for the female throwers was 1.15, whereas male throwers demonstrated a ratio of 1.22. Total push and pull force for the female throwers was significantly less than for the male throwers (5511 N vs. 8970 N, p < 0.001). Intraclass correlation coefficients ranged from 0.93 to 0.96 for the bench press and supine bench row exercise, indicating that the push and pull test device was highly reliable. The main findings of this study were that elite female and male discus, hammer, and shot put throwers exhibited 15% and 22% more pushing (bench press) than pulling (supine bench row) strength. Push and pull strength in the female throwers ranged from 47% to 71% of that of the male throwers. The push and pull test device is a reliable tool in establishing the agonist-to-antagonist ratio of upper body strength of athletes. Coaches and athletes may benefit from examining upper body push and pull strength ratios for training planning and prescription.