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(A) Geometric definition of shoulder and elbow angles. The range of shoulder flexion is set from 0° (fully extended) to 120° (fully flexed), and the range of elbow flexion is from 0° (fully extended) to 150° (fully flexed). Showing in the figure are a typical mono-articular muscle crossing the elbow joint, and a typical bi-articular muscle crossing both shoulder and elbow joints. The spindles are arranged in parallel with muscle fascicle fibers. We hypothesize that muscle fascicle length (Lce) and Ia afferent are related to the corresponding joint angles of span. Thus for bi-articular muscles, they are related to the sum of joint angles of span. (B) Nine sets of αstat commands (Table 1) are used to stabilize the VA model at nine equilibrium positions (1 ~ 9) in horizontal plane, respectively. At each position the spindle sensitivity control by γstat is investigated.
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Proprioceptive afferents from muscle spindles encode information about peripheral joint movements for the central nervous system (CNS). The sensitivity of muscle spindle is nonlinearly dependent on the activation of gamma (γ) motoneurons in the spinal cord that receives inputs from the motor cortex. How fusimotor control of spindle sensitivity affe...
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Exaggeration of the long-latency stretch reflex (LLSR) is a characteristic neurophysiologic feature of Parkinson's disease (PD) that contributes to parkinsonian rigidity. To explore one frequently-hypothesized mechanism, we studied the effects of fast muscle stretches on neuronal activity in the macaque primary motor cortex (M1) before and after th...
Citations
... In response to pain, the firing rates of lower-threshold (20% MVC) tibialis anterior MUs were suppressed, and firing rates of higher-threshold (70% MVC) MUs were increased (Martinez-Valdes et al., 2020), which suggests a stronger inhibitory influence on the lower-threshold MUs. Supporting this increased inhibition hypothesis from a mechanistic perspective, 2 weeks of cast immobilization in rats induced hyperalgesia (Ohmichi et al., 2012); prolonged fixed joints, such as adopted with disuse, could reasonably alter muscle spindle activity (Lan & He, 2012), and the lack of contraction-induced deformation of afferents might render them hypersensitive with reuse. Furthermore, disuse-associated inflammation might also have inhibitory effects via group III/IV inhibitory afferents (Amann, 2012;Jones et al., 2023). ...
... Of the four human cohorts covered herein in which individual MUs were sampled, 32 of the 33 combined participants were male. This limitation might be problematic given the documented differences in male and female MU function (Guo et al., 2022;Guo, Jones, Smart et al., 2024;Jenz & Pearcey, 2022;Lulic-Kuryllo & Inglis, 2022), and any further physiological constraints of including females appear minimal, given that similar methods of interrupted disuse have been used in female-only cohorts (MacLennan et al., 2021). ...
Neural conditioning to scenarios of muscle disuse is undoubtedly a cause of functional decrements that typically exceed losses of muscle size. Yet establishing the relative contribution of neural adaptation and the specific location in the motor pathway remains technically challenging. Several studies of healthy humans have targeted this system and have established that motor unit firing rate is suppressed following disuse, with a number of critical caveats. It is suppressed in the immobilized limb only, at relative and absolute force levels, and preferentially targets lower‐threshold motor units. Concomitantly, electrophysiological investigation of neuromuscular junction transmission (NMJ) stability of lower‐threshold motor units reveals minimal change following disuse. These findings contrast with numerous other methods, which show clear involvement of the NMJ but are unable to characterize the motor unit to which they belong. It is physiologically plausible that decrements observed following disuse are a result of suppressed firing rate of lower‐threshold motor units and impairment of transmission of the NMJ of higher‐threshold motor units. As such, motor units within the pool should be viewed in light of their varying susceptibility to disuse. image
... This discrepancy could be explained by variations in i) target positions, 322 with adult studies involving more end range positions (40°-70° extension) compared to the 323 midrange position (30° extension) in our study, and ii) positioningreplication procedure, 324 which was actively controlled in the adult subjects, whereas the JPR protocol in our study was 325 passive. Since joint mechanoreceptors and muscle spindles are more sensitive during end 326 range [46] and active movements [47] , respectively, it is plausible that these proprioceptors were 327 more activated, which could enhance the accuracy and reliability observed in adults. However, 328 unlike Suner-Keklik et al. (2017) (2.3°) [25] , other adult studies did not report better 329 proprioceptive knee accuracy (3.33°-4.65°) ...
Background: The Joint Position Reproduction (JPR) approach has been commonly used to assess joint position sense (JPS), however, no prior study investigated its psychometric properties in children. This study aimed to assess the reliability and precision of a newly developed multi–joint JPR protocol for assessing lower limb JPS in school-aged typically developing (TD) children.
Methods: Ankle, knee and hip JPS was assessed in TD children (aged 5–12 years), on two different days, by a single rater using a standardized JPR protocol (re–identification of a passively placed target position of the ipsilateral joint). The mean and best error(JRE,°) between target and reproduction angle were calculated from three–dimensional(3D) kinematics for each tested joint on both sides for three trials. Furthermore, total, joint– and limb–JRE scores were provided for clinical use. For JPR–reliability, the Intraclass Correlation Coefficient(ICC,2.1) was reported. For JPR–precision, the standard error of measurement (SEM) was calculated.
Results: 270 JPR trials were assessed in 15 TD children (8.6±1.2 years,8boys). The mean and best JRE, summarized for all joints for test and retest, was 3.7° and 2.5°, respectively. The ICC were poor to fair(0.01–0.44) for mean JRE, but fair to very good(0.46–0.77) for best JRE. The SEM ranged from 0.8°–1.8°, depending on the joint and side being tested.
Conclusion: Evaluating ankle, knee and hip JPS in children, using passive JPR, is more reliable and precise when using the best JRE. This study highlights the need for a multi–joint JPR approach in research and clinics, and provides joint- and limb-specific SEM values.
Keywords: Assessment; Proprioception; Joint Position Sense; Reliability; Precision
... Techniques with DS offer neurophysiological changes that correspond to a stretching using impulse in an attempt to exceed normal ROM. 41,43 Such dynamics tend to increase afferent impulses from the spindle reflex and neurons may subsequently affect performance. 43 In a pre-activity to CVJ, performance was more favorable after a maximal run than an PSS. ...
... 41,43 Such dynamics tend to increase afferent impulses from the spindle reflex and neurons may subsequently affect performance. 43 In a pre-activity to CVJ, performance was more favorable after a maximal run than an PSS. 44 Stretching was presented as a favorable prognostic factor regardless of its frequency. ...
Study design: identify a better strategy for static stretching (SS), dynamic stretching (DS), and proprioceptive neuromuscular facilitation (PNF) concerning the performance of their applications in countermovement vertical jump (CVJ). A systematic literature review was conducted in May and June 2021 in the Pubmed/MEDLINE, Scopus, LILACS, SPORTDiscus, and Embase databases. The PRISMA-2020 checklist was used. The Cochrane handbook scale and the Downs and Black scale were used for risk of bias analysis. Seventeen studies were included for qualitative analysis. Motor Unit recruitment and its stimulation frequency favor neural factors and muscle strength performance during contraction. Detailed investigations are necessary on the neural factors that modify the reflex responses and motor control, considering the biological characteristics and plastic deformations. The SS is a negative predictor of vertical jump (VJ) performance. The improvements are reduced when the stretching time is longer than 60 seconds, and when associated with PNF, did not reveal significant results. Using the SS before the DS in short periods of 20 seconds and no more than 60 seconds in the pre-activity to the VJ is suggested. In short stretches, the ROM increased both in the knee and the hip, and the hamstring muscles, when in tension, are unfavorable in sports that frequently use the VJ. Therefore, PNF using the technique that involves a process of contracting and relaxing must be investigated in an isolated and specific way, advocating the antagonist group. Thus, decreasing antagonist strength may be favorable for height gain, although contemporary studies are needed to minimize lower stability and muscle control predictors. Level of Evidence II; Systematic Review Study.
Keywords:
Amplitude; Volleyball; Muscle Stretching Exercises; Muscle Strength; Physical Functional Performance
... As técnicas com AD oferecem alterações neurofisiológicas que corresponde a um alongamento usando impulso em uma tentativa de exceder a ADM normal. 41,43 Tal dinâmica tende aumentar os impulsos aferentes do reflexo do fuso e os neurônios podem subsequentemente afetar o desempenho. 43 Numa pré-atividade ao SCM, o desempenho foi mais favorável após uma corrida máxima do que um AEP. ...
... 41,43 Tal dinâmica tende aumentar os impulsos aferentes do reflexo do fuso e os neurônios podem subsequentemente afetar o desempenho. 43 Numa pré-atividade ao SCM, o desempenho foi mais favorável após uma corrida máxima do que um AEP. 44 A realização do alongamento se apresentou com um fator prognóstico favorável independente de sua frequência. ...
Study design: identify a better strategy for static stretching (SS), dynamic stretching (DS), and proprioceptive neuromuscular facilitation (PNF) concerning the performance of their applications in countermovement vertical jump (CVJ). A systematic literature review was conducted in May and June 2021 in the Pubmed/MEDLINE, Scopus, LILACS, SPORTDiscus, and Embase databases. The PRISMA-2020 checklist was used. The Cochrane handbook scale and the Downs and Black scale were used for risk of bias analysis. Seventeen studies were included for qualitative analysis. Motor Unit recruitment and its stimulation frequency favor neural factors and muscle strength performance during contraction. Detailed investigations are necessary on the neural factors that modify the reflex responses and motor control, considering the biological characteristics and plastic deformations. The SS is a negative predictor of vertical jump (VJ) performance. The improvements are reduced when the stretching time is longer than 60 seconds, and when associated with PNF, did not reveal significant results. Using the SS before the DS in short periods of 20 seconds and no more than 60 seconds in the pre-activity to the VJ is suggested. In short stretches, the ROM increased both in the knee and the hip, and the hamstring muscles, when in tension, are unfavorable in sports that frequently use the VJ. Therefore, PNF using the technique that involves a process of contracting and relaxing must be investigated in an isolated and specific way, advocating the antagonist group. Thus, decreasing antagonist strength may be favorable for height gain, although contemporary studies are needed to minimize lower stability and muscle control predictors. Level of Evidence II; Systematic Review Study.
Keywords:
Amplitude; Volleyball; Muscle Stretching Exercises; Muscle Strength; Physical Functional Performance
... Even though our understanding of voluntary and reflexive control of movement is limited due to difficulties of neural recording in human, mammalian experiments reveal what thought to be instrumental for sensorimotor control: motor units with patterned recruitment order [8], spinal-level neural circuitry [9], dynamics of muscle spindle [10], muscle with viscoelastic properties [11]and the list goes on. Take proprioception as an example, a systematic unfolding for its understanding and application includes the following endeavors: pioneering work for spindle neurography [10], its computational modeling and continuing refinement [12]- [14], the engineering improvement for its real-time emulation and spiking behavior [15], and recently a "model-in-the-loop" application that demonstrated its feasibility for limb control [16]. On the ground of human sensorimotor control and the computational models thereof, we hypothesize that using biomimetic models for prosthetic control would enhance the overall performance. ...
... A controller with neuromorphic models, therefore, provided such a virtual environment that is compatible with the original intention of subjects before amputation. It is also noteworthy that all neuromorphic models implemented in this study are, in essence, mathematical formulations of high-order nonlinear systems [12], [14], [16]. Biomimetic models do not contradict the linear ones in principle of control, but rather they showed where the complexity should reside. ...
Prosthetic hands are frequently rejected due to frustrations in daily uses. By adopting principles of human neuromuscular control, it could potentially achieve human-like compliance in hand functions, thereby improving functionality in prosthetic hand. Previous studies have confirmed the feasibility of real-time emulation of neuromuscular reflex for prosthetic control. This study further to explore the effect of feedforward electromyograph (EMG) decoding and proprioception on the biomimetic controller. The biomimetic controller included a feedforward Bayesian model for decoding alpha motor commands from stump EMG, a muscle model, and a closed-loop component with a model of muscle spindle modified with spiking afferents. Real-time control was enabled by neuromorphic hardware to accelerate evaluation of biologically inspired models. This allows us to investigate which aspects in the controller could benefit from biological properties for improvements on force control performance. 3 able-bodied and 3 amputee subjects were recruited to conduct a “press-without-break” task, subjects were required to press a transducer till the pressure stabilized in an expected range without breaking the virtual object. We tested whether introducing more complex but biomimetic models could enhance the task performance. Data showed that when replacing proportional feedback with the neuromorphic spindle, success rates of amputees increased by 12.2% and failures due to breakage decreased by 26.3%. More prominently, success rates increased by 55.5% and failures decreased by 79.3% when replacing a linear model of EMG with the Bayesian model in the feedforward EMG processing. Results suggest that mimicking biological properties in feedback and feedforward control may improve the manipulation of objects by amputees using prosthetic hands.
... A virtual arm model with multi-joint, multi-muscles was later developed and validated for simulation studies of multi-joint arm control [204]. The model has been useful in investigating new hypotheses regarding sensorimotor control for normal movements or movement disorders [196,[212][213][214][215]. ...
Significant advances have been made to improve control and to provide sensory functions for bionic hands. However, great challenges remain, limiting wide acceptance of bionic hands due to inadequate bidirectional neural compatibility with human users. Recent research has brought to light the necessity for matching neuromechanical behaviors between the prosthesis and the sensorimotor system of amputees. A novel approach to achieving greater neural compatibility leverages the technology of biorealistic modeling with real-time computation. These studies have demonstrated a promising outlook that this unique approach may transform the performance of hand prostheses. Simultaneously, a noninvasive technique of somatotopic sensory feedback has been developed based on evoked tactile sensation (ETS) for conveying natural, intuitive, and digit-specific tactile information to users. This paper reports the recent work on these two important aspects of sensorimotor functions in prosthetic research. A background review is presented first on the state of the art of bionic hand and the various techniques to deliver tactile sensory information to users. Progress in developing the novel biorealistic hand prosthesis and the technique of noninvasive ETS feedback is then highlighted. Finally, challenges to future development of the biorealistic hand prosthesis and implementing the ETS feedback are discussed with respect to shaping a next-generation hand prosthesis.
... Ceux sont les seuls mécanorécepteurs du corps humain présentant cette singularité. Les fibres intrafusales sont ainsi innervées par des neurones moteurs gamma (γ) (Matthews 1962;Lan & He 2012;Ellaway et al. 2015). Cette innervation gamma, qui permet le contrôle fusimoteur, se divise en une composante dynamique innervant les fibres intrafusales à sac de type 1 et en une composante statique innervant les fibres intrafusales à sac de type 2 et à chaine nucléaire (Figure 4). ...
... Cette innervation gamma, qui permet le contrôle fusimoteur, se divise en une composante dynamique innervant les fibres intrafusales à sac de type 1 et en une composante statique innervant les fibres intrafusales à sac de type 2 et à chaine nucléaire (Figure 4). Le contrôle fusimoteur permet l'ajustement permanent de la longueur des fibres intrafusales au cours de contractions volontaires, et donc in fine de la sensibilité des fuseaux (Prochazka 1996; Flavio Da Silva | CADRE THÉORIQUE | 13 Prochazka & Ellaway 2012;Lan & He 2012;Ellaway et al. 2015). Pour la plupart des chercheurs, l'activation des motoneurones α et γ est réalisée de façon conjointe et d'intensité similaire. ...
Les objectifs de cette thèse étaient d’étudier i) les effets aigus et prolongés d’exercices physiques fatigants sur l’acuité kinesthésique et ii) le lien entre l’étiologie de la fatigue neuromusculaire induite et les altérations kinesthésiques.
Pour ce faire, dans chaque étude expérimentale, la fonction neuromusculaire et l’acuité kinesthésique (i.e., sens de la position ou sens du mouvement) étaient évaluées de façon concomitante avant et après la réalisation d’exercices fatigants de muscles croisant l’articulation du genou.
... Spindle model used here was constructed using data collected from animal studies [19], and was verified to generate reflex behaviors as those of human spindle [22], [60], [61], as well as those from microneurography [62], [63]. The contribution of monosynaptic reflex to enhance muscle stiffness in the model was estimated at 16.16 ± 12.33 % and 8.79 ± 9.54 % for flexor and extensor, respectively ( Fig. 3(d)), which was close to the range of measured values at 18-44 % of total stiffness in the first dorsal interosseous muscle in humans [38]. ...
italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Objective
: Human neuromuscular reflex control provides a biological model for a compliant hand prosthesis. Here we present a computational approach to understanding the emerging human-like compliance, force and position control, and stiffness adaptation in a prosthetic hand with a replica of human neuromuscular reflex model.
Methods:
A virtual twin of prosthetic hand was constructed in the MuJoCo environment with a tendon-driven anthropomorphic hand structure. Biorealistic mathematic models of muscle, spindle, spiking-neurons and monosynaptic reflex were implemented in neuromorphic chips to drive the virtual hand for real-time control.
Results:
Simulation showed that the virtual hand acquired human-like ability to control fingertip position, force and stiffness for grasp, as well as the capacity to interact with soft objects by adaptively adjusting hand stiffness.
Conclusion:
The biorealistic neuromorphic reflex model restores human-like neuromuscular properties for hand prosthesis to interact with soft objects.
... It is also noteworthy that all neuromorphic models implemented in this study are, in essence, mathematical formulations of high-order nonlinear systems. 48,56,61 Biomimetic models do not contradict the linear ones in principle of control, but rather they showed where the complexity should reside. In particular, impedance control measures position and generates force, which shares the same input-output structure as our modelbased controller, and therefore impedance control strategies are reasonable contenders when benchmarking the model-based controller. ...
Current control of prosthetic hands is ineffective when grasping deformable, irregular, or heavy objects. In humans, grasping is achieved under spinal reflexive control of the musculotendon skeletal structure, which produces a hand stiffness commensurate with the task. We hypothesize that mimicking reflex on a prosthetic hand may improve grasping performance and safety when interacting with human. Here, we present a design of compliant controller for prosthetic hand with a neuromorphic model of human reflex. The model includes 6 motoneuron pools containing 768 spiking neurons, 1 muscle spindle with 128 spiking afferents, and 1 modified Hill-type muscle. Models are implemented using neuromorphic hardware with 1 kHz real-time computing. Experimental tests showed that the prosthetic hand could sustain a 40 N load compared to 95 N for an adult. Stiffness range was adjustable from 60 to 640 N/m, about 46.6% of that of human hand. The grasping velocity could be ramped up to 14.4 cm/s, or 24% of the human peak velocity. The complaint control could switch between free movement and contact force when pressing a deformable beam. The amputee can achieve a 47% information throughput of healthy humans. Overall, the reflex-enabled prosthetic hand demonstrated the attributes of human compliant grasping with the neuromorphic model of spinal neuromuscular reflex.
... We neglect other types of proprioceptive feedback, for example from Golgi tendon organs, which may provide a link to joint-based control (Kistemaker et al., 2013). Furthermore, more detailed representations of the proprioceptors (Loeb and Mileusnic, 2015) allow for a detailed analysis of, e.g., the role of alpha-gamma co-activation (Lan and Zhu, 2007;Lan and He, 2012). ...
Human movement is generated by a dynamic interplay between the nervous system, the biomechanical structures, and the environment. To investigate this interaction, we propose a neuro-musculoskeletal model of human goal-directed arm movements. Using this model, we simulated static perturbations of the inertia and damping properties of the arm, as well as dynamic torque perturbations for one-degree-of freedom movements around the elbow joint. The controller consists of a feed-forward motor command and feedback based on muscle fiber length and contraction velocity representing short-latency (25 ms) or long-latency (50 ms) stretch reflexes as the first neuronal responses elicited by an external perturbation. To determine the open-loop control signal, we parameterized the control signal resulting in a piecewise constant stimulation over time for each muscle. Interestingly, such an intermittent open-loop signal results in a smooth movement that is close to experimental observations. So, our model can generate the unperturbed point-to-point movement solely by the feed-forward command. The feedback only contributed to the stimulation in perturbed movements. We found that the relative contribution of this feedback is small compared to the feed-forward control and that the characteristics of the musculoskeletal system create an immediate and beneficial reaction to the investigated perturbations. The novelty of these findings is (1) the reproduction of static as well as dynamic perturbation experiments in one neuro-musculoskeletal model with only one set of basic parameters. This allows to investigate the model's neuro-muscular response to the perturbations that-at least to some degree-represent stereotypical interactions with the environment; (2) the demonstration that in feed-forward driven movements the muscle characteristics generate a mechanical response with zero-time delay which helps to compensate for the perturbations; (3) that this model provides enough biomechanical detail to allow for the prediction of internal forces, including joint loads and muscle-bone contact forces which are relevant in ergonomics and for the development of assistive devices but cannot be observed in experiments.
