Search results for "electromyography"
showing 10 items of 672 documents
Brainstem reflex circuits revisited
2004
Our current understanding of brainstem reflex physiology comes chiefly from the classic anatomical-functional correlation studies that traced the central circuits underlying brainstem reflexes and establishing reflex abnormalities as markers for specific areas of lesion. These studies nevertheless had the disadvantage of deriving from post-mortem findings in only a few patients. We developed a voxel-based model of the human brainstem designed to import and normalize MRIs, select groups of patients with or without a given dysfunction, compare their MRIs statistically, and construct three-plane maps showing the statistical probability of lesion. Using this method, we studied 180 patients with…
Universal spectral profile and dynamic evolution of muscle activation: A hallmark of muscle type and physiological state
2020
The skeletal muscle is an integrated multicomponent system with complex dynamics of continuous myoelectrical activation of various muscle types across time scales to facilitate muscle coordination among units and adaptation to physiological states. To understand the multiscale dynamics of neuromuscular activity, we investigated spectral characteristics of different muscle types across time scales and their evolution with physiological states. We hypothesized that each muscle type is characterized by a specific spectral profile, reflecting muscle composition and function, that remains invariant over time scales and is universal across subjects. Furthermore, we hypothesized that the myoelectr…
The involvement of ankle muscles in maintaining balance in the upright posture is higher in elderly fallers
2016
International audience; The purpose of this study was to determine whether the mechanical contribution of ankle muscles in the upright stance differed among young adults (YA) (n = 10, age: similar to 24.3), elderly non-fallers (ENF) (n = 12, age: similar to 77.3) and elderly fallers (EF) (n = 20, age: similar to 80.7). Torque and electromyographic (EMG) activity were recorded on the triceps surae and tibialis anterior during maximum and submaximum contractions in the seated position. EMG activity was also recorded in subjects standing still. Plantar flexor (PF) and dorsal flexor (DF) torques generated in the upright posture were estimated from the torque-EMG relationship obtained during sub…
Velocity-specific training in elbow flexors.
1999
The purpose of this study was to show that velocity-specific training may be implicated in modifications in the level of coactivation of agonist and antagonist muscles. Healthy males (n = 20) were randomly placed in to two groups: one group trained using concentric contractions (n = 12), the other was an untrained control group (n = 8). The training group underwent unilateral resistance training at a level of 35 (5)% of a one-repetition maximal contraction of the elbow flexors, executed at maximal angular velocity. Training sessions consisted of six sets of eight consecutive elbow flexions, three times per weak for a total of seven weeks. The velocity of the ballistic movements executed dur…
Changes in agonist-antagonist EMG, muscle CSA, and force during strength training in middle-aged and older people
1998
Effects of 6 mo of heavy-resistance training combined with explosive exercises on neural activation of the agonist and antagonist leg extensors, muscle cross-sectional area (CSA) of the quadriceps femoris, as well as maximal and explosive strength were examined in 10 middle-aged men (M40; 42 ± 2 yr), 11 middle-aged women (W40; 39 ± 3 yr), 11 elderly men (M70; 72 ± 3 yr) and 10 elderly women (W70; 67 ± 3 yr). Maximal and explosive strength remained unaltered during a 1-mo control period with no strength training. After the 6 mo of training, maximal isometric and dynamic leg-extension strength increased by 36 ± 4 and 22 ± 2% ( P < 0.001) in M40, by 36 ± 3 and 21 ± 3% ( P < 0.001) in M7…
Coactivation at the ankle joint is not sufficient to estimate agonist and antagonist mechanical contribution
2009
The aim of this study was to assess, via an elec- tromyographic (EMG) biofeedback method, the mechanical con- tribution of both agonist and antagonist muscles during maximal voluntary contraction (MVC). We compared this original method with the MVC-EMGmax ratio and the torque/EMG relationship method, both of which are commonly used to estimate antago- nist torque. The plantarflexion (PF) and dorsiflexion (DF) MVCs were measured simultaneously with EMG activity of triceps surae (TS) and tibialis anterior in 15 young adults (mean age 23 years). Antagonist torques obtained from the torque/EMG relationship and EMG biofeedback methods appeared to be similar. TS antagonist torque had a major mech…
Effect of different ergonomic supports on muscle activity of dentists during posterior composite restoration
2019
BackgroundThe aim of this study was to evaluate the effect of different ergonomic supports on the muscle activity of two trunk muscles while a group of dentists performed a common dental procedure on a phantom head, divided into three tasks.MethodsA one-way repeated measures study (ANOVA) was conducted on a group of 36 dentists. The middle trapezius and lumbar erector spinae muscles were measured with and without the use of different ergonomic supports (ergonomic stool, magnification lenses and both) using a portable surface electromyography (sEMG) device. Intraclass correlation coefficients (ICCs) and the absolute standard error of measurement (SEM) were used to establish the reliability o…
EMG activity of pigeon oesophagus in vivo.
1982
At rest, the pigeon cervical oesophagus, which is entirely smooth muscle, shows electric activity. This activity consists of bursts of spikes with frequency increasing in the oral-aboral direction. The bursts are un-phase locked, and there are no slow waves (E.C.A.). The surgical transection of the oesophageal muscular wall does not affect the electric activity even in a disconnected segment. After asphyxia electric activity persists, whereas the aboral gradient of frequency disappears. Therefore, the electric activity is thought to be myogenic in origin, and the frequency gradient nervous in origin. Atropine and neostigmine administration suggests that the cholinergic system modulates the …
Electrical stimulation of glossopharyngeal nerve and oesophageal EMG response in the pigeon
1985
The effects of the efferent glossopharyngeal nerve stimulation, on EMG activity of the pigeon cervical oesophagus, were studied. In control animals, stimulation caused a biphasic response characterized by an intra-stimulus excitatory component followed by a post-stimulus inhibitory one. The EMG response to glossopharyngeal stimulation appeared simultaneously throughout the cervical oesophagus. A bell-shaped mechanical wave was detected relating to the electrical excitatory component. Atropine administration antagonized the excitatory component, while the inhibitory one persisted. It occurs intra-stimulus, and its duration is increased, compared to control ones. A reduction in the oesophagea…
Primary peristalsis in pigeon cervical oesophagus: two EMG patterns.
1984
Swallowing elicits two propagated EMG peristaltic patterns in pigeon cervical oesophagus: i) "simple" peristaltic pattern and ii) "complex" peristaltic pattern. "Simple" peristaltic pattern is characterized by an intense, long-lasting burst of spikes, high in amplitude with an aboral increasing delay in onset. "Complex" peristaltic pattern presents an early short period of reduction in spontaneous electrical activity, followed by an excitatory period similar to that of "simple" pattern. The early inhibitory component has a very short delay in onset increasing aborally. Atropine abolishes the EMG excitatory component of both patterns, while the inhibitory period persists, showing increased d…