ARTICLE | doi:10.20944/preprints202104.0006.v1
Subject: Physical Sciences, Acoustics Keywords: Colloids; Confinement; Ordering; Locomotion; Brownian Dynamics
Online: 1 April 2021 (10:19:02 CEST)
Confinement can induce substantial changes in the physical properties of macromolecules in suspension. Soft confinement is a particular class of restriction where the boundaries that constraint the particles in a region of the space are not well-defined. This scenario leads to a broader structural and dynamical behavior than the observed in systems enclosed between rigid walls. In this contribution, we study the ordering and diffusive properties of a two-dimensional colloidal model system subjected to a one-dimensional parabolic trap. Increasing the trap strength makes it possible to go through weak to strong confinement, allowing a dimensional transition from two- to one-dimension. The non-monotonic response of the static and dynamical properties to the gradual dimensionality change affects the system phase behavior. We find that the particle dynamics is connected with the structural transitions induced by the parabolic trap. In particular, at low and intermediate confinement regimes, complex structural and dynamical scenarios arise, where the softness of the external potential induces melting and freezing, resulting in faster and slower particle diffusion, respectively. Besides, at strong confinements, colloids move basically along one direction, and the whole system behaves structurally and dynamically similar to a one-dimensional colloidal system.
BRIEF REPORT | doi:10.20944/preprints202209.0340.v1
Subject: Medicine & Pharmacology, Sport Sciences & Therapy Keywords: Locomotion; Motor Control; Muscle Synergies; Physiology; Running
Online: 22 September 2022 (10:30:24 CEST)
Instep weights cause mechanical changes, modifying muscle activity and changing ground plantar support. 30 semi-professional sprinters, randomized in 3 groups [no-weight, Ascending (50, 100, 150 and 200g), Descending (200, 150, 100 and 50g)] run 6 consecutive 50-meter series at maximum speed (first and sixth without weights); partial, total times and speed were analyzed. Instep weights were safe and well tolerated. 6th series speed decreased except in men’s ascending group, who achieved a lower time in sixth compared to first series. Weights presented in ascending order in men during warm-up could improve running time. Instep weights neuromuscular effects could compensate men’s tiredness in last series; weights could be included in training methodologies. Men training weights presented in ascending order may provide better results.
ARTICLE | doi:10.20944/preprints202107.0168.v1
Subject: Biology, Anatomy & Morphology Keywords: lizard; autotomy; tail; locomotion; performance; temperature; predation
Online: 7 July 2021 (08:00:27 CEST)
Caudal autotomy is a dramatic adaptation used by many lizard species to evade predators. Most studies to date indicate that caudal autotomy impairs lizard locomotor performance. Surprisingly, some species bearing the longest tails show negligible impacts of caudal autotomy on sprint speed. Part of this variation has been attributed to lineage effects. For the first time, we model the effects of caudal autotomy on the locomotor performance of a gymnophthalmid lizard, Micrablepharus atticolus, characterized by a long and bright blue tail. To improve model accuracy, we incorporated the effects of several covariates. We found that body temperature, pregnancy, mass, collection site, and the length of the regenerated portion of the tail were the most important predictors of locomotor performance in Micrablepharus atticolus. However, sprint speed was unaffected by tail loss. Apparently, the long tail of M. atticolus is more useful when using undulation amidst the leaf litter and not when using quadrupedal locomotion on a flat surface. Our findings highlight the intricate relationships among physiological, morphological, and behavioral traits. We suggest that future studies about the impacts of caudal autotomy among long-tailed lizards should consider the role of different microhabitats/substrates on locomotor performance, using laboratory conditions that closely mimic their natural environments.
ARTICLE | doi:10.20944/preprints201712.0099.v1
Subject: Mathematics & Computer Science, Artificial Intelligence & Robotics Keywords: humanoid robot; bipedal locomotion; optimal control; optimization
Online: 15 December 2017 (05:02:00 CET)
Bipedal locomotion remains one of the major open challenges of humanoid robotics. The common approaches are based on simple reduced model dynamics to generate walking trajectories, often neglecting the whole-body dynamics of the robots. As motions in nature are often considered as optimal with respect to certain criteria, in this work we present an optimal control based approach that allows us to generate optimized walking motions using a precise whole-body dynamic model of the robot, in contrast with the common approaches. The optimal control problem is formulated to minimize a set of desired objective functions with respect to physical constraints of the robot and contact constraints of the walking phases. We apply the method with combinations of different objective criteria to the model of a reduced version of the iCub humanoid robot of 15 internal DOF. The obtained trajectories are executed on the real robot and we carry out a discussion on the differences between the outcomes of this approach with the classic approaches.
REVIEW | doi:10.20944/preprints202204.0174.v1
Subject: Medicine & Pharmacology, Sport Sciences & Therapy Keywords: cerebral palsy; locomotion; robotic rehabilitation; Lokomat; physiotherapy; pediatrics
Online: 19 April 2022 (04:07:24 CEST)
About 70% of children and adolescents with cerebral palsy experience gait impairments which affect their autonomy and well-being. Robotic-assisted gait training using the Lokomat is particu-larly promising for rehabilitation as it provides a standardized environment favoring the massive repetition of the movement, in which physical demands are low on the therapist and high training loads can be achieved. As no guidelines exist regarding training protocols and Lokomat settings, the goal of this study was to review the literature on Lokomat-assisted gait therapy and possibly make training recommendations. The twelve studies reviewed reported both positive and null effects of Lokomat training on gait. Half of the studies combined Lokomat with other types of training and only five used a control intervention to assess its benefit. Overall, training was administered 1-5 times per week for 20-60 minutes, over 1-12 weeks. Although Lokomat settings were not always described, progressively decreasing body-weight support and guidance, while increasing treadmill speed appear to be prioritized. The variety of training protocols and settings used did not allow pooling of the studies to assess effects of interventions on gait parameters in children and adoles-cents with cerebral palsy. This review highlights the need for homogenization of interventions so that clear guidelines can emerge and be applied in rehabilitation centers.
ARTICLE | doi:10.20944/preprints202110.0348.v1
Subject: Biology, Anatomy & Morphology Keywords: GlyT; glia; nervous system evolution; central pattern generator; locomotion; cephalochordates
Online: 25 October 2021 (12:45:26 CEST)
Glycine is an important neurotransmitter in vertebrates, performing both excitatory and inhibitory actions. Synaptic levels of glycine are tightly controlled by the action of two glycine transporters, GlyT1 and GlyT2, located on the surface of glial cells and glycinergic or glutamatergic neurons, respectively. Glycinergic neurotransmission in invertebrates has so far only been investigated in a very limited number of species, and, although it was suggested that its functions are to some extent conserved with vertebrates, the evolution of glycinergic neurotransmission remains very poorly understood. Here, by combining phylogenetic and gene expression analyses, we characterized the glycine transporter complement of amphioxus, an important invertebrate model for studying the evolution of chordates. We show that amphioxus possesses three glycine transporter genes, two of which (GlyT2.1 and GlyT2.2) are closely related to GlyT2 of vertebrates, while the other (GlyT) is a member of an ancestral clade of deuterostome glycine transporters. While expression of GlyT2.2 is predominantly non-neural, GlyT and GlyT2.1 are widely expressed in the amphioxus nervous system and are characterized by differential expression in neurons and glia, respectively. However, in vertebrates, glycinergic neurons express GlyT2 and glia GlyT1, suggesting that the evolution of the chordate glycinergic system was accompanied by complex genetic remodeling leading to the paralog-specific inversion of gene expression. Albeit this genetic divergence between amphioxus and vertebrates, we found strong evidence for a general conservation of the role of glycinergic neurotransmission during larval swimming, allowing us to hypothesize that the neural networks controlling the rhythmic movement of chordate bodies are homologous.
ARTICLE | doi:10.20944/preprints202012.0380.v1
Subject: Medicine & Pharmacology, Allergology Keywords: locomotion disorder; cadence; gait oscillation; speed of movement; neurodegenerative disease
Online: 15 December 2020 (12:39:34 CET)
Understanding the motor patterns underlying the movement of people with Parkinson's disease (PD) is fundamental to the effective targeting of non-pharmacological therapies. This study aims to analyze the gait pattern in relation to the evolutionary stage between I-II and III-IV according to the Hoehn and Yahr scale (H&Y) in people affected by PD. The study was conducted with the participation of 37 PD patients, with a mean age of 70.09±9.53 years, and of whom 48.64% were women. The inclusion criteria were: 1. To be diagnosed with PD; 2. To be in an evolutionary stage of the disease of between I and IV and; 3. To be able to walk independently and without any assistance. Kinematic and spatial-temporal parameters of the gait were analyzed. The results show differences in speed of movement, cadence, stride length, support duration, swing duration, step width, walking cycle duration and double support time between the stages analyzed. These results confirm the differences in PD gait pattern between stages I-II and III-IV. Different behaviors of the same variable were recorded depending on whether the right or left sides were affected by PD.
ARTICLE | doi:10.20944/preprints202203.0311.v1
Subject: Medicine & Pharmacology, Other Keywords: robot-assisted gait training; rehabilitation; stroke; cardiorespiratory fitness; robotics; disability; locomotion
Online: 23 March 2022 (08:40:16 CET)
Robot-assisted gait training (RAGT) is a promising treatment for stroke rehabilitation. Although the coordination between the upper and lower limbs is important for locomotor training, commercially available robotics for gait training mainly focus on the restoration of lower limb function. We aimed to evaluate the feasibility and usability of complex upper and lower limb RAGT in stroke patients using the GTR-A®, end effector-type robotic device. Patients with subacute stroke (N=9) received 30-minute RAGT thrice a week for two weeks (six sessions). Functionally, the hand grip strength (HGS), Functional Ambulatory Categories, modified Barthel Index, muscle strength test sum score, Berg Balance Scale, Timed Up and Go test, and Short Physical Performance Battery were used. The heart rate and a structured questionnaire were used to evaluate cardiorespiratory fitness and the usability of RAGT. Among the nine patients, all functional parameters between the baseline and post-training were significantly improved after RAGT, except for HGS and the muscle strength test. The questionnaire’s mean scores for each domain were as follows: safety 4.40±0.35, effects 4.23±0.31, efficiency 4.22±0.77, and satisfaction 4.41±0.25. The GTR-A® is a feasible and safe robotic device for patients with gait impairment after stroke. It showed functional improvement with endurance training effects.
ARTICLE | doi:10.20944/preprints202007.0217.v2
Subject: Engineering, Mechanical Engineering Keywords: Bio inspired robot; legged Robot; locomotion; position control; walk gait; wooden robot
Online: 20 July 2020 (04:13:18 CEST)
We present the design and overall development of an eight degrees of freedom (DOF) based Bioinspired Quadruped Robot (BiQR). The robot is designed with a skeleton made of cedar wood. The wooden skeleton is based on exploring the potential of cedar wood to be a choice for legged robots’ design. With a total weight of 1.19 kg, the robot uses eight servo motors that run the position control. Relying on the inverse kinematics, the control design enables the robot to perform the walk gait-based locomotion in a controlled environment. The robot has two main aspects: 1) the initial wooden skeleton development of the robot showing it to be an acceptable choice for robot design, 2) the robot’s applicability as a low-cost legged platform to test the locomotion in a laboratory or a classroom setting.
ARTICLE | doi:10.3390/sci2030060
Subject: Keywords: locomotion; machine learning; support vector machines; activity classification; activity of daily life (ADL)
Online: 18 July 2020 (00:00:00 CEST)
Although Support Vector Machines (SVM) are widely used for classifying human motion patterns, their application in the automatic recognition of dynamic and static activities of daily life in the healthy older adults is limited. Using a body mounted wireless inertial measurement unit (IMU), this paper explores the use of SVM approach for classifying dynamic (walking) and static (sitting, standing and lying) activities of the older adults. Specifically, data formatting and feature extraction methods associated with IMU signals are discussed. To evaluate the performance of the SVM algorithm, the effects of two parameters involved in SVM algorithm—the soft margin constant C and the kernel function parameter
—are investigated. The changes associated with adding white-noise and pink-noise on these two parameters along with adding different sources of movement variations (i.e., localized muscle fatigue and mixed activities) are further discussed. The results indicate that the SVM algorithm is capable of keeping high overall accuracy by adjusting the two parameters for dynamic as well as static activities, and may be applied as a tool for automatically identifying dynamic and static activities of daily life in the older adults.
ARTICLE | doi:10.20944/preprints202108.0023.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Nicotine toxicity; Wnt1 pathway; spinal cord injury; locomotor networks; excitotoxicity; fictive locomotion; postnatal; rat; mice
Online: 2 August 2021 (11:52:54 CEST)
The postnatal rodent spinal cord in-vitro is a useful model to investigate early pathophysiological changes after injury. While low dose nicotine (1µM) induces neuroprotection, how higher doses affect spinal networks is unknown. Using spinal preparations of postnatal wild-type Wistar rat and Wnt1Cre2:Rosa26Tom double-transgenic mouse, we studied the effect of nicotine (0.5-10µM) on locomotor networks in-vitro. Nicotine 10µM induced motoneuron depolarization, suppressed monosynaptic reflexes, and decreased fictive locomotion in rat spinal cord. Delayed fall in neuronal numbers (including motoneurons) of central and ventral regions emerged without loss of dorsal neurons. Conversely, nicotine (0.5-1µM) preserved neurons throughout the spinal cord and strongly activated the Wnt1 signaling pathway. High-dose nicotine enhanced expression of S100 and GFAP in astrocytes suggesting their response to stress. Excitotoxicity induced by kainate was contrasted by nicotine (10µM) in the dorsal area and persisted in central and ventral regions with no change basal Wnt signaling. When combining nicotine with kainate, the activation of Wnt1 was reduced compared to kainate/sham. The present results suggest that high dose nicotine was neurotoxic to central and ventral spinal neurons as the neuroprotective role of Wnt signaling became attenuated. This also corroborates the risk of cigarette smoking for the foetus/newborn since tobacco contains nicotine.