Search results for "Muscles"
showing 10 items of 616 documents
Dynamical behaviour of pneumatic artificial muscles
2014
The mechanical response of pneumatic artificial muscles is analyzed in transient and periodic conditions, assuming the inextensibility of the sheathing fibres and considering the influence of the texture geometry, of the dissipation due to the mutual sliding between the braids and of the stress field inside the bladder thickness, where the constituent elastomer is regarded as a two-parameter Mooney–Rivlin material. The polytropic exponent of the thermodynamic air evolution inside the muscle during the charging and discharging phases may be properly chosen depending on the working frequency. The muscle end shape is taken into account profiling the meridian section by a simple m-degree parabo…
A theoretical approach to pneumatic muscle mechanics
2013
The mechanical response of pneumatic artificial muscles is analyzed assuming the inextensibility of the sheathing braids and taking into account the stress field inside the rubber bladder, which is regarded as a Mooney-Rivlin hyperelastic material. The end effects are simulated by heuristically profiling the meridian section. After estimating the constitutive parameters by traction tests on rubber specimens, the theoretical results are compared with experiments and a satisfactory accordance may be detected.
Reversible stress softening of collagen based networks from the jumbo squid mantle (Dosidicus gigas).
2014
Dosidicus gigas is the largest and one of the most abundant jumbo squids in the eastern Pacific Ocean. In this paper we have studied the muscle of the mantle of D. gigas (DGM). Morphological, thermal and rheological properties were assessed by means of atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, differential scanning calorimetry, thermogravimetry and oscillatory rheometry. This study allowed us to assess the morphological and rheological properties of a collagen based network occurring in nature. The results showed that the DGM network displays a nonlinear effect called reversible stress softening (RSS) that has been previously described for …
Changes in trunk posture and muscle responses in standing during pregnancy and postpartum
2018
Este artículo se encuentra disponible en la página web de la revista en la siguiente URL: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0194853 The aim of this study was to analyze the position of the lumbopelvic region and the muscle activation of erector spinae and biceps femoris muscles in a group of pregnant women in the third trimester. The hypothesis was that pregnancy-related biomechanical and morphological changes modify the position of the lumbopelvic region and the activation of extensor muscles. The position of the lumbar spine and pelvis in the sagittal plane, and the EMG activity of the erector spinae and biceps femoris muscles, were recorded during standing…
Effects of different recovery parameters during resistance training exercices
2012
The high frequency of resistance training sessions induces heavy strain and fatigue phenomenon, which could be prejudicial for subsequent performance. In this context, it appears necessary to apply proper recovery strategies in order to improve the athlete’s ability to regain an adequate working state for subsequent training.Active recovery is widely described in the literature as the most efficient method for this purpose. It consists in low-intensity exercises, which could improve metabolites washout by increasing peripheral blood flow. To our knowledge, active recovery is usually applied globally, with exercises involving the whole body (light pedalling or running) but little is known re…
Dynamics of Quadriceps Muscles during Isometric Contractions : Velocity-Encoded Phase Contrast MRI Study
2021
Objective: To quantify the spatial heterogeneity of displacement during voluntary isometric contraction within and between the different compartments of the quadriceps. Methods: The thigh muscles of seven subjects were imaged on an MRI scanner while performing isometric knee extensions at 40% maximal voluntary contraction. A gated velocity-encoded phase contrast MRI sequence in axial orientations yielded tissue velocity-encoded dynamic images of the four different compartments of the thigh muscles (vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI), and rectus femoris (RF)) at three longitudinal locations of the proximal–distal length: 17.5% (proximal), 50% (middle), and 7…
Spinocerebellar ataxia: functional analysis of the stomatognathic system
2019
Background Neurodegenerative diseases that affect the cerebellum, especially in elderly individuals, cause impairment of motor coordination and quality of life. The presente study evaluated the electromyographic activity and thickness of the right and left masseter and temporal muscles, and the maximum molar bite force of individuals with spinocerebellar ataxia. Material and Methods Twenty-eight individuals were divided into two groups: those with (n=14) and without (n=14) spinocerebellar ataxia. Data on the masticatory muscles obtained from the electromyographic activity (resting, right and left laterality and protrusion), muscle thickness (maximal voluntary contraction and tensile strengt…
The Origin, Location, and Projections of the Embryonic Abdominal Motorneurons ofDrosophila
1997
We have used a retrograde labeling technique to identify motorneurons for each of the 30 body wall muscles of an abdominal hemisegment in the late stage 16Drosophilaembryo. Each motorneuron has a characteristic cell body position, dendritic arborization, and axonal projection. In addition, we have determined the neuroblasts of origin for most of the motorneurons we describe. Some organizational principles for the neuromuscular system have become apparent: (1) There is no obvious topographic relationship between the cell body positions of motorneurons and the position or orientation of the muscles they innervate; (2) motorneurons that innervate muscles of similar position and orientation are…
Revealing the unique features of each individual's muscle activation signatures
2021
International audience; There is growing evidence that each individual has unique movement patterns, or signatures. The exact origin of these movement signatures, however, remains unknown. We developed an approach that can identify individual muscle activation signatures during two locomotor tasks (walking and pedalling). A linear support vector machine was used to classify 78 participants based on their electromyographic (EMG) patterns measured on eight lower limb muscles. To provide insight into decision-making by the machine learning classification model, a layer-wise relevance propagation (LRP) approach was implemented. This enabled the model predictions to be decomposed into relevance …
Ultrasound imaging assessment of the diaphragm and abdominal muscles in people with a recent history of moderate Covid-19 infection and healthy parti…
2023
Coronavirus disease (Covid-19) is a highly infectious disease caused by the SARS-CoV-2 virus and is associated with a decrease of respiratory, physical, and psychological function, subsequently affecting quality of life. The aim of the present pilot study was to use ultrasound imaging (USI) to evaluate and compare the thickness of the diaphragm and abdominal muscles between individuals recently diagnosed with moderate Covid-19 infection and healthy individuals. Methods: A cross-sectional observational pilot study was performed. A total sample of 24 participants were recruited from a private medical center (Madrid, Spain): Covid-19 (n = 12) and healthy controls (n = 12). The external oblique…