Antagonist Muscles Research Articles

Combining transcutaneous interferential-current for nerve inhibition with a robotic assistant device for increasing ankle dorsiflexion in walking

BackgroundA kilohertz-frequency alternating current transcutaneously applied was introduced as a novel neuromodulation technology for nerve inhibition innervating antagonist muscles. Combining this electrical nerve inhibition with a robotic assistance device has been proposed but not investigated. Research questionThis study aimed to demonstrate the effect of combining electrical nerve inhibition with a wearable robotic device on increasing ankle dorsiflexion during walking. We hypothesized that the wearable robotic device would elicit a greater ankle dorsiflexion angle with the same force in walking by applying the transcutaneous interferential-current nerve inhibition (TINI) technique to the tibial nerve. MethodsEleven healthy young adults performed three experimental conditions. The ankle assistance (AA) condition was walking while wearing an ankle device with operating dorsiflexion assistance during pre-swing and swing phases. For the ankle assistance with electrical stimulation (AE) condition, TINI on the tibial nerve was additionally applied from the AA condition. In the ankle non-assistance (AN) condition, participants wore the device, but assistance was not provided. The joint angles during walking were measured and digitized through a motion analysis system. ResultsDuring a gait cycle, immediate changes in ankle joint motions were observed in the sagittal plane. In the pre-swing phase, ankle dorsiflexion angle was significantly greater in AE condition than AA and AN. There was no significant difference in joint angle between AA and AN. SignificanceThis study demonstrates the effectiveness of combining TINI with a wearable robotic ankle device in increasing dorsiflexion angle during the pre-swing phase. This finding provides the feasibility of using TINI as a neuromodulation technique for assisting functional movement in human walking.

Is There a Standard Rehabilitation Procedure in Cervical Dystonia?

Introduction: Idiopathic cervical dystonia, also known as spasmodic torticollis, is the most common form of focal dystonia in adults. Cervical dystonia usually appears between the ages of 30 and 50, twice as often in women, and is characterised by uncontrollable painful contractions of the sternocleidomastoid muscle, which results in misalignment of the head and shoulder. Over time, the disease becomes very burdensome for the patient and reduces his/her independence and quality of life; falls happen.Aim: The aim of the article is to present the current state of knowledge on comprehensive rehabilitation in cervical dystonia. Data on the prevalence, symptoms, diagnosis, clinical assessment, pharmacological treatment (including the most commonly used botulinum toxin), neurosurgical treatment and comprehensive rehabilitation are presented.Methods: The applied methods was a narrative critical review of scientific reports.Results: Out of several hundred publications, works worthy of particular attention were selected. In them, are described of conducting exercises, the main goal of which is to stretch and relax the dystonic muscles while strengthening the antagonistic muscles and correcting the position of the head. The selected authors used manual therapy, exercises at the patient's home, EMG biofeedback, magnetic stimulation of the cerebellum, vibration of the neck muscles, functional electrostimulation (FES) of antagonistic muscles, mobilisation of the cervical spine, postural exercises, isometric exercises, muscle relaxation, the PNF method, relaxation training, balance exercises, coordination, corrective exercises, massage, relaxation exercises, stretching and kinesiotaping.Conclusions: The variety of disease forms (10 head positioning patterns are described) and different severity of symptoms make it impossible to draw up a scheme of rehabilitation. In each case, rehabilitation must be tailored individually, and the physiotherapist taking care of the patient should have extensive experience. Physiotherapy can alleviate the disability caused by dystonia, however, due to the many non-motor symptoms, a holistic approach to the patient should also be kept in mind.

Intramuscle Synergies: Their Place in the Neural Control Hierarchy.

We accept a definition of synergy introduced by Nikolai Bernstein and develop it for various actions, from those involving the whole body to those involving a single muscle. Furthermore, we use two major theoretical developments in the field of motor control-the idea of hierarchical control with spatial referent coordinates and the uncontrolled manifold hypothesis-to discuss recent studies of synergies within spaces of individual motor units (MUs) recorded within a single muscle. During the accurate finger force production tasks, MUs within hand extrinsic muscles form robust groups, with parallel scaling of the firing frequencies. The loading factors at individual MUs within each of the two main groups link them to the reciprocal and coactivation commands. Furthermore, groups are recruited in a task-specific way with gains that covary to stabilize muscle force. Such force-stabilizing synergies are seen in MUs recorded in the agonist and antagonist muscles but not in the spaces of MUs combined over the two muscles. These observations reflect inherent trade-offs between synergies at different levels of a control hierarchy. MU-based synergies do not show effects of hand dominance, whereas such effects are seen in multifinger synergies. Involuntary, reflex-based, force changes are stabilized by intramuscle synergies but not by multifinger synergies. These observations suggest that multifinger (multimuscle synergies) are based primarily on supraspinal circuitry, whereas intramuscle synergies reflect spinal circuitry. Studies of intra- and multimuscle synergies promise a powerful tool for exploring changes in spinal and supraspinal circuitry across patient populations.

External Focus Reduces Accuracy and Increases Antagonist Muscle Activation in Novice Adolescent Soccer Players.

Instep kick is one of the most effective kicking techniques in soccer. Lower extremity muscles and joints play a crucial role during instep kick. However, external (EF) and internal focus and their effect on the muscles are still ambiguous. In this study, 13 male adolescent soccer players were included and aimed to hit the targets in internal and EF conditions. Lower extremity muscle activations were measured with surface electromyography, and kinematics were measured with a high-speed video camera. Muscle activations and movement latencies were analyzed in four different phases (backswing, leg cocking, acceleration, and follow-through) of kicking. While 10 out of 13 participants kicked accurately in internal focus, only five out of 13 in EF kicked accurately. Gastrocnemius muscle activations increased significantly in EF in all phases except acceleration. Movement latencies were found 0.07 ± 0.002s for accurate and 0.05 ± 0.004s for inaccurate kicks in EF. A correlation has been found between accuracy and movement latency in EF (R = .67). Our results suggest that novices cannot yet coordinate their muscles in EF, cocontraction ratio increases. Therefore, training strategies that aim to reduce the cocontraction ratio can help the athlete increase performance through better motor coordination. Moreover, better motor coordination may be beneficial in preventing injuries (joint stiffness, etc.) caused by increased cocontraction ratio.

Functional electrical stimulation therapy for upper extremity rehabilitation following spinal cord injury: a pilot study.

Pilot study. To examine if functional electrical stimulation therapy (FEST) improves neuromuscular factors underlying upper limb function in individuals with SCI. A tertiary spinal cord rehabilitation center specialized in spinal cord injury care in Canada. We examined 29 muscles from 4 individuals living with chronic, cervical, and incomplete SCI. The analysis was focused on the changes in muscle activation, as well as on how the treatment could change the ability to control a given muscle or on how multiple muscles would be coordinated during volitional efforts. There was evidence of gains in muscle strength, activation, and median frequency after the FEST. Gains in muscle activation indicated the activation of a greater number of motor units and gains in muscle median frequency the involvement of higher threshold, faster motor units. In some individuals, these changes were smaller but accompanied by increased control over muscle contraction, evident in a greater ability to sustain a volitional contraction, reduce the co-contraction of antagonist muscles, and provide cortical drive. FEST increases muscle strength and activation. Enhanced control of muscle contraction, reduced co-contraction of antagonist muscles, and a greater presence of cortical drive were some of the findings supporting the effects of FEST at the sensory-motor integration level.

Design of a soft bionic elbow exoskeleton based on shape memory alloy spring actuators

Abstract. Shape memory alloy (SMA) is a kind of active deformation material with a self-sensing and driving ability. It is very similar to the performance of human muscles, and through temperature changes to produce phase changes to output force and displacement, it has the ability to restore the initial shape and size. The combination of SMA and wearable robotic technology has the advantages of being light weight, energy-saving, and having great human–exoskeleton interaction. However, the existing flexible exoskeletons driven by SMA are only designed with bionic primary muscles, ignoring the role of antagonistic muscles. This study presents a novel soft bionic elbow exoskeleton based on SMA spring actuators (Sobee-SMA). The exoskeleton adopts a bionic design, combining active deformation material SMA and a high-elastic-material rubber band to simulate the contraction and relaxation of elbow skeletal muscles. Through a pulse width modulation (PWM) experiment, the driving voltage is selected as 12 V, the PWM duty cycle is 90 % during heating, and the PWM duty cycle is 18 % during heat preservation. In a relaxed state of healthy subjects, the range of motion of the elbow is about 0–80∘, and the maximum temperature is about 60–70 ∘C. During the circular movement of the elbow, the maximum temperature can be maintained within the SMA operating temperature without a high temperature. In conclusion, the exoskeleton provides elbow-assisted motion and ensures the safety of the heating process.

Neurointerface with oscillator motifs for inhibitory effect over antagonist muscles.

The effect of inhibitory management is usually underestimated in artificial control systems, using biological analogy. According to our hypothesis, the muscle hypertonus could be effectively compensated via stimulation by bio-plausible patterns. We proposed an approach for the compensatory stimulation device as implementation of previously presented architecture of the neurointerface, where (1) the neuroport is implemented as a DAC and stimulator, (2) neuroterminal is used for neurosimulation of a set of oscillator motifs on one-board computer. In the set of experiments with five volunteers, we measured the efficacy of motor neuron inhibition via the antagonist muscle or nerve stimulation registering muscle force with and without antagonist stimulation. For the agonist activation, we used both voluntary activity and electrical stimulation. In the case of stimulation of both the agonist and the antagonist muscles and nerves, we experimented with delays between muscle stimulation in the range of 0-20 ms. We registered the subjective discomfort rate. We did not identify any significant difference between the antagonist muscle and nerve stimulation in both voluntary activity and electrical stimulation of cases showing agonist activity. We determined the most effective delay between the stimulation of the agonist and the antagonist muscles and nerves as 10-20 ms.

Spectrum of motor responses elicited by electrical stimulation of primary motor cortex: A polygraphic study in patients with epilepsy

ObjectiveTo study the neurophysiology of motor responses elicited by electrical stimulation of the primary motor cortex. MethodsWe studied motor responses in four patients undergoing invasive epilepsy monitoring and functional cortical mapping via electrical cortical stimulation using surface EMG electrodes. In addition, polygraphic analysis of intracranial EEG and EMG during bilateral tonic-clonic seizures, induced by cortical stimulation, was performed in two patients. Results(a) Electrical cortical stimulation: The motor responses were classified as clonic, jittery, and tonic. The clonic responses were characterized by synchronous EMG bursts of agonist and antagonistic muscles, alternating with silent periods. At stimulation frequencies of <20 Hz, EMG bursts were of ≤50 ms duration (Type I clonic). At stimulation frequencies of 20–50 Hz, EMG bursts were of >50 ms duration and had a complex morphology (Type II clonic). Increasing the current intensity at a constant frequency converted clonic responses into jittery and tonic contractions.(b) Bilateral tonic-clonic seizures: The intracranial EEG showed continuous fast spiking activity during the tonic phase along with interference pattern on surface EMG. The clonic phase was characterized by a polyspike-and-slow wave pattern. The polyspikes were time-locked with the synchronous EMG bursts of agonists and antagonists and the slow waves were time-locked with silent periods. InterpretationThese results suggest that epileptic activity involving the primary motor cortex can produce a continuum of motor responses ranging from type I clonic, type II clonic, and tonic responses to bilateral tonic-clonic seizures. This continuum is related to the frequency and intensity of the epileptiform discharges with tonic seizures representing the highest end of the spectrum.

Increased muscle responses to balance perturbations in children with cerebral palsy can be explained by increased sensitivity to center of mass movement

BackgroundBalance impairments are common in children with cerebral palsy (CP). Muscle activity during perturbed standing is higher in children with CP than in typically developing (TD) children, but we know surprisingly little about how sensorimotor processes for balance control are altered in CP. Sensorimotor processing refers to how the nervous system translates incoming sensory information about body motion into motor commands to activate muscles. In healthy adults, muscle activity in response to backward support-surface translations during standing can be reconstructed by center of mass (CoM) feedback, i.e., by a linear combination of delayed (due to neural transmission times) CoM displacement, velocity, and acceleration. The level of muscle activity in relation to changes in CoM kinematics, i.e., the feedback gains, provides a metric of the sensitivity of the muscle response to CoM perturbations. Research questionCan CoM feedback explain reactive muscle activity in children with CP, yet with higher feedback gains than in TD children? MethodsWe perturbed standing balance by backward support-surface translations of different magnitudes in 20 children with CP and 20 age-matched TD children and investigated CoM feedback pathways underlying reactive muscle activity in the triceps surae and tibialis anterior. ResultsReactive muscle activity could be reconstructed by delayed feedback of CoM kinematics and hence similar sensorimotor pathways might underlie balance control in children with CP and TD children. However, sensitivities of both agonistic and antagonistic muscle activity to CoM displacement and velocity were higher in children with CP than in TD children. The increased sensitivity of balance correcting responses to CoM movement might explain the stiffer kinematic response, i.e., smaller CoM movement, observed in children with CP. SignificanceThe sensorimotor model used here provided unique insights into how CP affects neural processing underlying balance control. Sensorimotor sensitivities might be a useful metric to diagnose balance impairments.

Mechanical disturbances applied by motorized ankle foot orthosis to adapt ankle muscles activation-A validation study.

Background: Reduced function of ankle muscles usually leads to impaired gait. Motorized ankle foot orthoses (MAFOs) have shown potential to improve neuromuscular control and increase volitional engagement of ankle muscles. In this study, we hypothesize that specific disturbances (adaptive resistance-based perturbations to the planned trajectory) applied by a MAFO can be used to adapt the activity of ankle muscles. The first goal of this exploratory study was to test and validate two different ankle disturbances based on plantarflexion and dorsiflexion resistance while training in standing still position. The second goal was to assess neuromuscular adaptation to these approaches, namely, in terms of individual muscle activation and co-activation of antagonists. Methods: Two ankle disturbances were tested in ten healthy subjects. For each subject, the dominant ankle followed a target trajectory while the contralateral leg was standing still: a) dorsiflexion torque during the first part of the trajectory (Stance Correlate disturbance-StC), and b) plantarflexion torque during the second part of the trajectory (Swing Correlate disturbance-SwC). Electromyography was recorded from the tibialis anterior (TAnt) and gastrocnemius medialis (GMed) during MAFO and treadmill (baseline) trials. Results: GMed (plantarflexor muscle) activation decreased in all subjects during the application of StC, indicating that dorsiflexion torque did not enhance GMed activity. On the other hand, TAnt (dorsiflexor muscle) activation increased when SwC was applied, indicating that plantarflexion torque succeeded in enhancing TAnt activation. For each disturbance paradigm, there was no antagonist muscle co-activation accompanying agonist muscle activity changes. Conclusion: We successfully tested novel ankle disturbance approaches that can be explored as potential resistance strategies in MAFO training. Results from SwC training warrant further investigation to promote specific motor recovery and learning of dorsiflexion in neural-impaired patients. This training can potentially be beneficial during intermediate phases of rehabilitation prior to overground exoskeleton-assisted walking. Decreased activation of GMed during StC might be attributed to the unloaded body weight in the ipsilateral side, which typically decreases activation of anti-gravity muscles. Neural adaptation to StC needs to be studied thoroughly in different postures in futures studies.

Effects of modified hybrid resistance training on concentric quadriceps femoris peak torque and eccentric hamstring peak torque in untrained healthy subjects

Background: Leg muscular strength may decline as a result of decreased mechanical stress on the muscles brought on by the COVID-19 pandemic's physical inactivity. The hybrid training method uses the force generated by an electrically stimulated antagonist muscle to resist a voluntarily contracting agonist muscle. Due to the lack of external resistance or stability equipment, this exercise may be a good option for strengthening workouts during a pandemic. Modifications were made using conventional stimulation tools because the hybrid training system was difficult to replicate. The study's objective was to analyze the effect of modified hybrid resistance training on concentric quadriceps femoris peak torque (QCON) and eccentric hamstring peak torque (HECC). Methods: The study was conducted at the Medical Rehabilitation Installation of Dr. Soetomo General Academic Hospital Surabaya. The subjects were 30 untrained healthy men aged 18-40 years divided into the treatment group, which received modified hybrid resistance training and the control group, which received Russian protocol neuromuscular electrical stimulation 3 times per week for 4 weeks. Due to COVID-19 infection, four participants couldn’t continue in intervention. Statistical tests were carried out on subjects that were able to complete the study (treatment: 13, control:13). Results: There were increases in 60o/sec QCON (p-value 0.005) and 120o/sec QCON (p-value 0.001) in the non-dominant leg in the treatment group. There were increases in 60o/sec QCON (p-value 0.043), 120o/sec QCON (p-value 0.014), and 120o/sec HECC (p-value 0.043) in the non-dominant leg in the control group. There is a significant difference in non-dominant 120o/sec ΔQCON between the two groups (p-value 0.036). Conclusion: There was a more significant increase in QCON in the modified hybrid training exercises group compared to the Russian stimulation group in untrained healthy subjects.

Effects of Paired Associative Stimulation on Cortical Plasticity in Agonist–Antagonist Muscle Representations

Paired associative stimulation (PAS) increases and decreases cortical excitability in primary motor cortex (M1) neurons, depending on the spike timing-dependent plasticity, i.e., long-term potentiation (LTP)- and long-term depression (LTD)-like plasticity, respectively. However, how PAS affects the cortical circuits for the agonist and antagonist muscles of M1 is unclear. Here, we investigated the changes in the LTP- and LTD-like plasticity for agonist and antagonist muscles during PAS: 200 pairs of 0.25-Hz peripheral electric stimulation of the right median nerve at the wrist, followed by a transcranial magnetic stimulation of the left M1 with an interstimulus interval of 25 ms (PAS-25 ms) and 10 ms (PAS-10 ms). The unconditioned motor evoked potential amplitudes of the agonist muscles were larger after PAS-25 ms than after PAS-10 ms, while those of the antagonist muscles were smaller after PAS-25 ms than after PAS-10 ms. The γ-aminobutyric acid A (GABAA)- and GABAB-mediated cortical inhibition for the agonist and antagonist muscles were higher after PAS-25 ms than after PAS-10 ms. The cortical excitability for the agonist and antagonist muscles reciprocally and topographically increased and decreased after PAS, respectively; however, GABAA and GABAB-mediated cortical inhibitory functions for the agonist and antagonist muscles were less topographically decreased after PAS-10 ms. Thus, PAS-25 ms and PAS-10 ms differentially affect the LTP- and LTD-like plasticity in agonist and antagonist muscles.

Anticipatory Postural Adjustments and Compensatory Postural Responses to Multidirectional Perturbations—Effects of Medication and Subthalamic Nucleus Deep Brain Stimulation in Parkinson’s Disease

Postural instability is one of the most restricting motor symptoms for patients with Parkinson's disease (PD). While medication therapy only shows minor effects, it is still unclear whether medication in conjunction with deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves postural stability. Hence, the aim of this study was to investigate whether PD patients treated with medication in conjunction with STN-DBS have superior postural control compared to patients treated with medication alone. Three study groups were tested: PD patients on medication (PD-MED), PD patients on medication and on STN-DBS (PD-MED-DBS), and healthy elderly subjects (HS) as a reference. Postural performance, including anticipatory postural adjustments (APA) prior to perturbation onset and compensatory postural responses (CPR) following multidirectional horizontal perturbations, was analyzed using force plate and electromyography data. Regardless of the treatment condition, both patient groups showed inadequate APA and CPR with early and pronounced antagonistic muscle co-contractions compared to healthy elderly subjects. Comparing the treatment conditions, study group PD-MED-DBS only showed minor advantages over group PD-MED. In particular, group PD-MED-DBS showed faster postural reflexes and tended to have more physiological co-contraction ratios. medication in conjunction with STN-DBS may have positive effects on the timing and amplitude of postural control.

Effectiveness of Home Based Telerehabilitation for Forward Versus Backward Stepping Strategy in Ground Walking Training on Functional Mobility and Balance Among Spastic Diplegic Cerebral Palsy-- A Simple Experimental Study

Background: The primary focus of physiotherapy interventions for children with CP is to improve locomotor function and functional activities. It is suggested that walking training activates neural circuits that mediate central pattern generators to activate limb muscles repetitively and produced rhythmic movements. Additionally, it adjusts control between agonist and antagonist muscles, leading to enhanced walking speed, and static and functional balance. The purpose of the study is to find out the effectiveness of home based telerehabilitation for forward stepping vs backward stepping strategy in ground walking training on functional mobility and balance among spastic diplegic cerebral palsy. Methodology: A simple experimental study was conducted on 24 spastic diplegic cerebral palsy who fulfill the selection criteria were selected for this study at the telerehabilitation Unit. A clear explanation was given to every subject and parents/guardian about the procedures and a written consent was obtained from them. Twenty spastic diplegic children were evaluated in person in the department for pre-training and post-training were used as a study design with total study duration was six weeks. (from April 2021 to May 2021). The subjects in group A&amp;B were consisting of 12 subjects and they were treated with home based telerehabilitation for forward and backward ground walking training. Along with that both the group children received routine physiotherapy. Both the groups were received intervention for 15-30 minutes per session, 5 days in a week for a period of 6 weeks. The pre and post score values of balance and functional mobility were measured by using, GMFM walking dimension, modified timed get up and go test and Pediatric Berg balance scale. The values were recorded and documented. Result: In the statistical analysis of pretest values of both group A and group B were calculated. The pre mean values of PBS for both groups were 33.33 and 33.38. The T-value was 0.3721 the obtained t-value is lesser than the table value and the P-value showed there were no significant in pretest comparison. The posttest mean values of PBS for both groups were 46.08 and 46.33.The T-value was 2.38967,the obtained t-value is greater than the table value. and the P-value showed there were significant in posttest comparison. Alternative hypothesis was accepted. Hence the statistical report states that there were statistically significant differences in posttest comparison. The post score values of the Gross Motor Function Meaure-88, Pediatric Berg Balance Scale and TUG test score in all the variables showed significant difference. Conclusion: The study concluded that the 6 weeks of backward stepping strategy in ground walking home based telerehabilitation training program along with regular physiotherapy treatment showed statistically significant improvement in balance and functional mobility among spastic diplegic children when compared to forward stepping strategy in ground walking home based telerehabilitation training program.

繰り返し学習制御と機能的電気刺激によるペダリング運動

This paper deals with repetitive learning control for functional electrical stimulation (FES) pedaling exploiting pedal force direction with antagonistic biarticular muscles . FES pedaling motion with muscle contraction is expressed as an Euler Lagrange system. Asymptotic tracking for the closed-loop system by the proposed controller is analyzed through Lyapunov-based methods. Experiments were conducted in three healthy individuals to show the validity of the proposed method from a practical point of view.

The use of blood flow restriction does not enhance adaptations of corticospinal excitability or intracortical inhibition after acute resistance training

Resistance exercise with blood flow restriction (BFR) is considered a safe and powerful training tool. Low-load (LL) resistance training with BFR results in comparable hypertrophy compared to conventional heavy-load (HL) resistance training (Centner et al., 2019). Additionally, LL training with BFR (LL-BFR) induces comparable (Grønfeldt et al., 2020) or slightly lower (Centner et al., 2019) effects on muscle strength than HL training. It is generally accepted that increases in maximum strength are mediated by muscular hypertrophy and/or neural adaptations. However, the effect of BFR on neural adaptations is scarcely investigated. The aim of this study was therefore to investigate the effects of BFR on acute neural adaptations following a single bout of resistance training.&#x0D; Fifteen male participants (21-35 years) volunteered to participate in this study. On three separate days, participants performed a strength training session of the right elbow flexors with either LL, LL-BFR or HL. Neuromuscular adaptations were investigated before and after each resistance training session by means of transcranial magnetic stimulation (single- and paired-pulse TMS) and peripheral nerve stimulation (Mmax). Data were acquired during submaximal sustained isometric contractions. During LL-BFR, the cuff was inflated to 50% of the individual arterial occlusion pressure to restrict venous outflow in the working musculature during exercise.&#x0D; The preliminary data analysis with mixed linear models revealed that, compared to baseline values, normalized MEPs (% of Mmax) from the trained biceps brachii were enhanced for HL (Cohen’s d = 0.51) but not LL-BFR (Cohen’s d = 0.03) when compared to LL. None of the groups showed relevant changes in short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). The size of Mmax decreased slightly for HL (Cohen’s d = -0.18) but not LL-BFR (Cohen’s d = 0.06) when compared to LL.&#x0D; This is the first study that investigated acute neural adaptations in response to resistance training with and without BFR. We observed increased MEP amplitudes after HL but not LL what is in line with previous evidence (Mason et al., 2019). Since training with BFR results in a rapid increase in motoneuronal excitability (Copithorne et al., 2020), the increased MEP are less likely caused by changes at the cortical site.&#x0D; Centner, C., Wiegel, P., Gollhofer, A., &amp; König, D. (2019). Effects of blood flow restriction training on muscular strength and hypertrophy in older individuals: A systematic review and meta-analysis. Sports Medicine, 49, 95-108. https://doi.org/10.1007/s40279-018-0994-1&#x0D; Copithorne, D. B., Rice, C. L., &amp; McNeil, C. J. (2020). Effect of blood flow occlusion on corticospinal excitability during sustained low-intensity isometric elbow flexion. Journal of Neurophysiology, 123(3), 1113-1119. https://doi.org/10.1152/jn.00644.2019&#x0D; Grønfeldt, B. M., Lindberg Nielsen, J., Mieritz, R. M., Lund, H., &amp; Aagaard, P. (2020). Effect of blood-flow restricted vs heavy-load strength training on muscle strength: Systematic review and meta-analysis. Scandinavian Journal of Medicine &amp; Science in Sports, 30(5), 837-848. https://doi.org/10.1111/sms.13632&#x0D; Mason, J., Howatson, G., Frazer, A. K., Pearce, A. J., Jaberzadeh, S., Avela, J., &amp; Kidgell, D. J. (2019). Modulation of intracortical inhibition and excitation in agonist and antagonist muscles following acute strength training. European Journal of Applied Physiology, 119, 2185-2199. https://doi.org/10.1007/s00421-019-04203-9

Treatment of writer’s cramp based on current pathophysiological concepts

Task specific dystonia belongs to the group of focal dystonias. They are debilitating movement disorders that present with co-contraction of antagonist muscles during a specific task. The most common one is writer’s cramp. Botulinum toxin is the symptomatic standard treatment. Its response rate is 50% after 1 year, and the overall efficacy limited due to unwanted weakness in not injected muscles. The pathophysiology of writer’s cramp remains unclear, but genetic and additional environmental causes have been proposed. A possible underlying mechanism may be maladaptive reorganization in the sensorimotor cortex. Based on this background alternative treatment strategies were developed such as several different sensory and motor training programs that have been applied to reverse these brain abnormalities. In some studies, sensory and motor training were combined and adjunct with fitness exercises. They were conducted either as an outpatient setting or were established home based. Clinical outcome was measured with different clinical scales such as the writer’s cramp rating scale, the arm dystonia rating scale or the Burke, Fahn Marsden Scale. For objective assessment, kinematic handwriting parameters were analyzed. Functional or structural changes of the sensorimotor cortex were estimated using functional magnetic tomography, magnetencephalography and voxel-based morphometry. The results of these training programs were promising; however, one drawback is that the number of patients studied were small and the programs were not controlled since it is difficult to establish a control training to conduct a randomized controlled study.

Elbow Joint Stiffness Functional Scales Based on Hill's Muscle Model and Genetic Optimization.

The ultimate goal of rehabilitation engineering is to provide objective assessment tools for the level of injury and/or the degree of neurorehabilitation recovery based on a combination of different sensing technologies that enable the monitoring of relevant measurable variables, as well as the assessment of non-measurable variables (such as muscle effort/force and joint mechanical stiffness). This paper aims to present a feasibility study for a general assessment methodology for subject-specific non-measurable elbow model parameter prediction and elbow joint stiffness estimation. Ten participants without sensorimotor disorders performed a modified "Reach and retrieve" task of the Wolf Motor Function Test while electromyography (EMG) data of an antagonistic muscle pair (the triceps brachii long head and biceps brachii long head muscle) and elbow angle were simultaneously acquired. A complete list of the Hill's muscle model and passive joint structure model parameters was generated using a genetic algorithm (GA) on the acquired training dataset with a maximum deviation of 6.1% of the full elbow angle range values during the modified task 8 of the Wolf Motor Function Test, and it was also verified using two experimental test scenarios (a task tempo variation scenario and a load variation scenario with a maximum deviation of 8.1%). The recursive least square (RLS) algorithm was used to estimate elbow joint stiffness (Stiffness) based on the estimated joint torque and the estimated elbow angle. Finally, novel Stiffness scales (general patterns) for upper limb functional assessment in the two performed test scenarios were proposed. The stiffness scales showed an exponentially increasing trend with increasing movement tempo, as well as with increasing weights. The obtained general Stiffness patterns from the group of participants without sensorimotor disorders could significantly contribute to the further monitoring of motor recovery in patients with sensorimotor disorders.

Dystonias: Clinical Recognition and the Role of Additional Diagnostic Testing.

Dystonia is the third most common movement disorder, characterized by abnormal, frequently twisting postures related to co-contraction of agonist and antagonist muscles. Diagnosis is challenging. We provide a comprehensive appraisal of the epidemiology and an approach to the phenomenology and classification of dystonia, based on the clinical characteristics and underlying etiology of dystonia syndromes. We discuss the features of common idiopathic and genetic forms of dystonia, diagnostic challenges, and dystonia mimics. Appropriate workup is based on the age of symptom onset, rate of progression, whether dystonia is isolated or combined with another movement disorder or complex neurological and other organ system features. Based on these features, we discuss when imaging and genetic should be considered. We discuss the multidisciplinary treatment of dystonia, including rehabilitation and treatment principles according to the etiology, including when pathogenesis-direct treatment is available, oral pharmacological therapy, chemodenervation with botulinum toxin injections, deep brain stimulation and other surgical therapies, and future directions.

Child-Adult differences in antagonist muscle coactivation: A systematic review.

Antagonist coactivation is the simultaneous activation of agonist and antagonist muscles during a motor task. Age-related changes in coactivation may contribute to observed differences in muscle performance between children and adults. Our aim was to systematically summarize age-related differences in antagonist muscle coactivation during multi-joint dynamic and single-joint isometric and isokinetic contractions. Electronic databases were searched for peer-reviewed studies comparing coactivation in upper or lower extremity muscles between healthy children and adolescents/young adults. Of the 1083 studies initially identified, 25 met eligibility criteria. Thirteen studies examined multi-joint dynamic movements, 10 single-joint isometric contractions, and 2 single-joint isokinetic contractions. Of the studies investigating multi-joint dynamic contractions, 83% (11/13 studies) reported at least one significant age-related difference: In 84% (9/11 studies) coactivation was higher in children, whereas 16% (2/11 studies) reported higher coactivation in adults. Among single-joint contractions, only 25% (3/12 studies) reported significantly higher coactivation in children. Fifty six percent of studies examined females, with no clear sex-related differences. Child-adult differences in coactivation appear to be more prevalent during multi-joint dynamic contractions, where generally, coactivation is higher in children. When examining child-adult differences in muscle function, it is important to consider potential age-related differences in coactivation, specifically during multi-joint dynamic contractions.