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In this paper, we propose a general controller for complex tasks such as coordination or manipulation for grasping systems or dynamic gaits for legged robots. Moreover, this controller is adapted to pneumatic actuated structures. The aim is then to ensure a dynamic tracking of position and force for systems which may interact with the environment or cooperate with each other. For that, we propose a nonlinear controller based on a computed torque method taking into account the actuator and the mechanical models. The originality lays in the consideration of impedance behaviour at each joint during free and constrained tasks. It leads to continuous control laws between contact and non-contact phases. The asymptotic stability is ensured using Popov criteria. The application proposed is the control of one pneumatic leg of a biped robot. We present a dynamic model of the leg and chosen trajectories. Simulation results of this new controller are presented, leading to a good behaviour of the leg during a whole walking cycle at relatively high velocities.

An original structure to simulate the vertical dynamic jump of one leg is proposed in this paper. The aim is to reproduce a motion composed of an upward propulsion, a flying and a landing phase. The leg is modeled as a three rigid body moved by three pneumatic actuators. A dynamic model of the structure is first presented and the design of the impedance controller is developed based on the nonlinear control theory. The originality of the controller lays in the consideration of impedance behavior at each joint during free and constrained phases. The asymptotic stability is ensured using Popov criteria. The simulations proposed are based on physiological data coming from experiments of a human performing a jump. This specific motion will show the performances of the controller especially during the propulsion and the landing phases because of their high acceleration characteristics. [DOI: 10.1115/1.1371773]

Describes the different strategies developed when a step is needed in a forward trunk bending movement in a modelling purpose. Kinds of perturbation that may occur in a postural control field; Division of the bipedal stance phase; Study findings.

Background: Functional correlates of spastic myopathy, the muscle disorder of spastic paresis, are unknown., Objective: To explore reciprocal relationships between clinical and structural parameters of plantar flexors with i) ambulation speed, ii) dorsiflexion and plantarflexion torques in chronic hemiparesis., Methods: Cross-sectional trial in chronic stroke-induced hemiparesis (>6 months). Plantar flexors were quantified through i) the Five Step Assessment: maximal extensibility (XV1), active range of dorsiflexion (XA); ii) ultrasonography: fascicle length (Lf) and thickness (Th) of medial gastrocnemius (GAS) and soleus (SOL), knee extended in an isokinetic ergometer, ankle at 80% XV1-GAS. Maximal isometric torques in plantar flexion (PF) and dorsiflexion (DF) and maximal barefoot 10-meter ambulation speed were collected. Relationships between structural, biomechanical, clinical and functional parameters were explored using non-parametric testing (Spearman)., Results: Twenty-one subjects (age 58.0±8.4, mean±SD, time since lesion 7.8±5.7 years) were recruited, with the following characteristics: ambulation speed, 0.77±0.37m/sec; XV1-SOL 92.7±10.3°; XV1-GAS 91.3±9.6°; XA-SOL 86.9±10.0°; XA-GAS 7676±14.2°; LfGAS, 58.2±18.3mm; ThGAS, 17.1±3.6 mm; LfSOL, 36.0±9.6 mm; ThSOL, 13.8±3.3mm; PF peak-torque 46.5±34.1Nm, DF peak-torque, 20.1±19.1Nm. XA-SOL and XA-GAS strongly correlated with XV1-SOL and XV1-GAS respectively (ρ = 0.74, p = 4E-04; resp ρ = 0.60, p = 0.0052). Ambulation speed moderately correlated with LfGAS (ρ = 0.51, p = 0.054), ThGAS (ρ = 0.58, p = 0.02) and LfSOL (ρ = 0.63, p = 0.009). DF and PF peak-torques both correlated with LfGAS (ρ = 0.53, p = 0.04) a; resp. ρ = 0.71, p = 0.0015)., Conclusion: In chronic hemiparesis, active dorsiflexion is mostly determined by plantar flexor extensibility. Plantar flexor fascicle shortening is associated with reduced ambulation speed and ankle torques. Attempts to restore plantar flexor extensibility might be important objectives for gait rehabilitation in chronic hemiparesis., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Pradines et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Objective: This study aimed: (i) to investigate the impact of fatigue, triggered by maximal isometric contraction exercises, on the active and passive stiffness of plantar flexors (PF), and (ii) to examine the relationship between changes in mechanical parameters and neuromuscular alterations after fatigue., Methods: A healthy cohort (n = 12; age = 27.3 ± 5.5 y; BMI = 24.4 ± 2.35 kg/m²) was instructed to perform 60 isometric contractions, each lasting 4 s with a 1-s rest interval, using an ergometer. Several measures were taken before and after the fatigue protocol. First, the stiffness of the PF-tendon complex (PFC) was quantified during passive ankle mobilization both during and after the fatigue protocol using the ergometer. Additionally, from shear wave elastography, the active and passive stiffness of the gastrocnemius medialis (GM) were measured during passive ankle mobilization and isometric maximal voluntary contraction (MVC), respectively. Finally, the peak torque and the rate of torque development (RFD) of PF were assessed during the MVC using the ergometer. Ankle muscle activities (surface electromyograph [SEMG]) were recorded during all evaluations using electromyography., Results: After the fatigue protocol, the results revealed a decline in active stiffness, peak torque of PF, RFD and SEMG activity of the GM (p < 0.001). Furthermore, significant correlation was identified between the decrease of the peak torque of PF and the active stiffness of the GM (r = 0.6; p < 0.05). A decrease in the PFC stiffness (p < 0.001) and a decrease in the shear modulus of the GM at 20° (p < 0.001) were also observed., Conclusion: Isometric fatiguing exercises modify the mechanical properties of both the contractile and elastic components. Notably, decreases in both passive and active stiffness may be critical for athletes, as these changes could potentially increase the risk of injury., Competing Interests: Conflict of interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

Background: One year after persistent peripheral facial paresis (PFP), prescriptions of conventional rehabilitation are often downgraded into maintenance rehabilitation or discontinued, the patient entering what is seen as a chronic stage. This therapeutic choice is not consistent with current knowledge about behavior-induced plasticity, which is available all life long and may allow intense sensorimotor rehabilitation to remain effective. This prospective, randomized, multicenter single-blind study in subjects with chronic unilateral PFP evaluates changes in facial motor function with a Guided Self-rehabilitation Contract (GSC) vs. conventional therapy alone, carried out for six months., Methods: Eighty-two adult subjects with chronic unilateral PFP (> 1 year since facial nerve injury) will be included in four tertiary, maxillofacial surgery (2), otolaryngology (1) and rehabilitation (1) centers to be randomized into two rehabilitation groups. In the experimental group, the PM&R specialist will implement the GSC method, which for PFP involves intensive series of motor strengthening performed daily on three facial key muscle groups, i.e. Frontalis, Orbicularis oculi and Zygomatici. The GSC strategy involves: i) prescription of a daily self-rehabilitation program, ii) teaching of the techniques involved in the program, iii) encouragement and guidance of the patient over time, in particular by requesting a quantified diary of the work achieved to be returned by the patient at each visit. In the control group, participants will benefit from community-based conventional therapy only, according to their physician's prescription. The primary outcome measure is the composite score of Sunnybrook Facial Grading System. Secondary outcome measures include clinical and biomechanical facial motor function quantifications (Créteil Scale and 3D facial motion analysis through the Cara system), quality of life (Facial Clinimetric Evaluation and Short-Form 12), aesthetic considerations (FACE-Q scale) and mood representations (Hospital Anxiety and Depression scale). Participants will be evaluated every three months by a blinded investigator, in addition to four phone calls (D30/D60/D120/D150) to monitor compliance and tolerance to treatment., Discussion: This study will increase the level of knowledge on the effects of intense facial motor streng-          Facial paralysisthening prescribed through a GSC in patients with chronic peripheral facial paresis., Trial Registration: ClinicalTrials.gov, NCT04074018 . Registered 29 August 2019., Protocol Version: Version N°4.0-04/02/2021., (© 2023. The Author(s).)

This work proposes a 3D normative database of facial ranges of motion in adults free from facial disorders. Ten facial movements were analyzed, each targeting the activity of specific muscle groups innervated by the facial nerve. The experimental protocol included a test-retest reliability positioning procedure of 25 skin markers based on clinical expertise in facial morphology. Three maximal voluntary contractions were recorded for each facial movement studied, using a 3D facial motion capture helmet. We included 53 adults free from facial disorders (26 men; age 43 ± 14), evaluated twice one week apart. The reliability of marker positioning was expressed as absolute measurement errors. The range of motion vectors of all markers from the best rest to the maximal voluntary contraction was calculated for each muscle group. Primary, secondary, and tertiary markers were extracted for each facial movement. 3D Procruste and asymmetry indices were developed. This allowed the identification of common thresholds of 10% for the asymmetry index and of 6 mm for the Procruste index, beyond which facial motions would be considered abnormally asymmetric. The normative database quantifies facial motions and allows assessment of the degree of clinical disorders by comparison. This protocol is currently being investigated in patients with chronic unilateral peripheral facial paresis., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2022 Marina Guihard et al.)

We study ion-damaged crystalline silicon by combining nanocalorimetric experiments with an off-lattice kinetic Monte Carlo simulation to identify the atomistic mechanisms responsible for the structural relaxation over long time scales. We relate the logarithmic relaxation, observed in a number of disordered systems, with heat-release measurements. The microscopic mechanism associated with this logarithmic relaxation can be described as a two-step replenish and relax process. As the system relaxes, it reaches deeper energy states with logarithmically growing barriers that need to be unlocked to replenish the heat-releasing events leading to lower-energy configurations.