Search results for " Muscle"
showing 10 items of 1495 documents
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.
Influence of a Crosslinker Containing an Azo Group on the Actuation Properties of a Photoactuating LCE System
2016
Photoactuating liquid crystalline elastomers (LCE) are promising candidates for an application as artificial muscles in microdevices. In this work, we demonstrate that by optimizing (1) the illumination conditions and (2) the mixture of azo monomer and azo crosslinker, thick films of an all-azo LCE can be prepared, which show a strong length change without bending during photoactuation. This becomes possible by working with white light (about 440 nm), whose absorption is low, leading to a large penetration depth. By adding an azo crosslinker to a previously prepared system, several improvements of the actuation properties—like a stronger photoactuation at lower operational temperatures—coul…
Behaviour of vastus lateralis muscle-tendon during high intensity SSC exercises in vivo
2003
Aims: The interaction between fascicle and tendinous tissue of human vastus lateralis muscle was investigated during varying intensity stretch–shortening cycle (SSC) jumps performed on a sledge apparatus. Methods: Eight subjects performed single leg squat (SJ) and drop jumps (DJ) from a constant dropping height but to different rebound heights. The fascicle length of the vastus lateralis muscle (VL) was determined from real-time ultrasonography during the movement. Tendon length changes were calculated by subtracting the horizontal part of the fascicle length from the muscle–tendon unit (MTU) length. Simultaneously, kinematic, kinetic and electromyographic data were recorded from leg musc…
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…
Neuromuscular and Chest Wall Diseases in Pregnancy
2009
Patients with severe respiratory muscle impairment, in particular when vital capa-city is below 60% of the predicted normal values, are often discouraged frombecoming pregnant for fear of respiratory complications and the need for tra-cheostomy and invasive mechanical ventilation (1). A growing fetus can impairthe functioning of weak diaphragms resulting in lower vital capacity and respira-tory reserve and impair cough function. In addition, there is increased oxygenconsumption and ventilation requirement. Complications in pregnancy and theneed for analgesics and anesthesia during labor and delivery can also cause orexacerbate ventilatory failure.Neuromuscular DiseasesNeuromuscular diseases…
Bullying victimization and muscle dysmorphic disorder in Italian adolescents: The mediating role of attachment to peers
2021
Abstract Bullying victimization has a negative impact on the psychological health of individuals, including in cases of muscle dysmorphic disorder (MD). However, research into possible mediation factors is sparse. The present study aimed to investigate the role of attachment to peers in the association between bullying victimization and MD. This study included 1,062 participants with an average age of 17.44 years (range 15–21 years; SD = 1.14) from four high schools in northwestern Italy. The hypothesized relationships among the variables were tested through structural equation model. Path analysis modeling yielded significant results showing an indirect path from bullying victimization to …
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…
Transversus abdominis and multifidus asymmetry in runners measured by MRI: a cross-sectional study
2019
ObjectiveThe transversus abdominis muscle (TrA) is active during running as a secondary respiratory muscle and acts, together with the multifidus, as trunk stabiliser. The purpose of this study was to determine size and symmetry of TrA and multifidus muscles at rest and with contraction in endurance runners without low back pain.DesignCross-sectional study.SettingA medical imaging centre in Melbourne, Australia.ParticipantsThirty middle-aged (43years±7) endurance-trained male (n=18) and female (n=12) runners without current or history of low back pain.Outcome measuresMRI at rest and with the core engaged. The TrA and multifidus muscles were measured for thickness and length (TrA) and antero…
Does Function Determine the Structure? Changes in Flexor Hallucis Longus Muscle and the Associated Performance Related to Dance Modality: A Cross-Sec…
2020
Background and Objectives: Flexor hallucis longus pathology is one of the most common conditions of the ankle and foot in dancers, due to the high demand of dance movements performed in an extreme plantar flexion and dorsiflexion range of motion. The objectives of this study were to determine the bilateral differences between the thickness and cross-sectional area of the flexor hallucis longus muscle in dancers, to establish possible differences between dance modalities, and to analyze whether there is a correlation between ultrasonographic parameters or performance variables and the dance modality. Material and Methods: A sample of 50 (29 classical and 21 contemporary) full-time pre-profes…