Search results for "Myograph"
showing 10 items of 689 documents
The effects of muscle history on short latency stretch reflex response of soleus muscle
2003
Abstract The purpose of the present study was to investigate the combined effects of muscle history, activation and stretching velocity on short latency stretch response (SLR). Stretches (70, 120 and 200 deg s-1) were elicited to both passive and active (10–25% MVC) triceps surae muscle with constant (ISO), lengthened (LEN) or shortened (SHO) muscle length. Under the passive SHO pre-condition both SLR amplitude and reflex torque (RT) decreased where as latency increased compared with the passive ISO pre-condition. Such observations were absent in active trials. Stretches applied to a lengthening passive muscle (LEN) resulted in smaller SLR amplitude and RT compared with passive ISO. In acti…
Effects of differently induced stretch loads on neuromuscular control in drop jump exercise
1996
The neuromuscular characteristics of the triceps surae and vastus lateralis muscles and interactions between the pre-activation of these muscles and the muscle output itself during ground contact were investigated during various types of stretch-shortening cycle muscle loading. The loading of the muscles was effected by using three different types of drop jump exercise. These jumps allowed separate modifications of the loading of the leg extensor muscles by changing the velocity of the centre of gravity (CG) or by changing directly the body mass, which was also affected by changing artificially the acceleration of the CG. It was found that the eccentric peak angular velocity of the ankle jo…
Neuromuscular changes after long-lasting mechanically and electrically elicited fatigue
2001
Central fatigue was investigated under an isolated active condition whereby the possible effects of supraspinal fatigue were minimized. Therefore, ten subjects were fatigued by simultaneously and repeatedly mechanically stretching and electrically stimulating their calf muscles for 1 h. This was performed using an ankle ergometer. The active fatigue task included a total of 2400 muscle stretches with an intensity of 10% of the maximal voluntary contraction (MVC). This protocol clearly impaired neuromuscular function, as revealed by a significant reduction in MVC (P < 0.01) and the neural input to the muscle (average EMG) (P < 0.01-0.001). The interpolated nerve stimulation compensated for t…
Reduced stretch reflex sensitivity and muscle stiffness after long-lasting stretch-shortening cycle exercise in humans
1998
It has been suggested that during repeated long-term stretch-shortening cycle (SSC) exercise the decreased neuromuscular function may result partly from alterations in stiffness regulation. Therefore, interaction between the short latency stretch-reflex component (M1) and muscle stiffness and their influences on muscle performance were investigated before and after long lasting SSC exercise. The test protocol included various jumps on a sledge ergometer. The interpretation of the sensitivity of the reflex was based on the measurements of the patellar reflexes and the M1 reflex components. The peak muscle stiffness was measured indirectly and calculated as a coefficient of the changes in the…
Neuromuscular control in landing from supra-maximal dropping height.
2009
International audience; The present study utilized high-impact supra-maximal landings to examine the influence of the pre-impact force level on the post-impact electromyographic (EMG) activity and, in particular, on the short latency EMG reflex (SLR) component. Unilateral-leg landings were performed in a sitting position on a sledge apparatus after release from high, but individually constant dropping height. A lower limb guiding device fixed to the front of the sledge seat allowed the subjects to sustain a given pre-set force level up to impact. This force level was either freely chosen or set at 20, 35, and 50% of maximal isometric plantarflexion force. EMG activity was recorded from eigh…
Reduced stretch-reflex sensitivity after exhausting stretch-shortening cycle exercise.
1996
The stretch-shortening cycle (SSC) is an effective and natural form of muscle function but, when repeated with sufficient intensity or duration, it may lead to muscle damage and functional defects. A reduced tolerance to impact has been reported, which may be partly attributed to a reduced stretch-reflex potentiation. The aim of the present study was to examine the influence of SSC-induced metabolic fatigue and muscle damage on the efficacy of stretch reflexes, as judged by the electromyograph (EMG) response of two shank muscles (lateral gastrocnemius LG, soleus SOL) to controlled ramp stretches. These EMG responses were recorded before and immediately after exhausting SSC-type leg exercise…
Analysis of F response in upper motoneurone lesions
2009
The F response can provide a measure of motoneurone excitability (MNE) and so it may be used to investigate upper motoneurone disorders. This report studies the F-wave configuration in patients with stroke to evaluate the changes of the central excitability of the motoneurones at different times after an acute cerebral insult. Various parameters of the F response, including amplitude (absolute and F%/M), duration, and persistence have been determined in 26 patients with unilateral hemiplegia and in 32 healthy subjects of both sexes in the same age range. The investigation was carried out applying a series of 20 supramaximal stimuli at 0.5 Hz on tibial and ulnar nerves bilaterally. In all pa…
Subthreshold low frequency repetitive transcranial magnetic stimulation selectively decreases facilitation in the motor cortex
2002
Objective: To investigate the modulatory effect of a subthreshold low frequency repetitive transcranial magnetic stimulation (rTMS) train on motor cortex excitability. Methods: The study consisted of two separate experiments. Subjects received a 10 min long subthreshold 1Hz rTMS train. In the first experiment, (single pulse paradigm), cortical excitability was assessed by measuring the amplitude of motor evoked potentials (MEPs) before and after the rTMS train. In the second experiment, a paired pulse paradigm was employed. Results: Corticospinal excitability, as measured by the MEP amplitude, was reduced by the rTMS train (experiment 1), with a significant effect lasting for about 10 min a…
Modulation of input–output curves by low and high frequency repetitive transcranial magnetic stimulation of the motor cortex
2002
Objectives: Exploring the modulatory effects of different frequencies of repetitive transcranial magnetic stimulation (rTMS) on the excitability of the motor cortex as measured by the input-output curve technique (I-O curve). Methods: Sixteen healthy subjects participated in this experiment. On two different sessions, conducted 1 week apart, rTMS was applied either at a frequency of 20 or 1Hz at 90% of individual motor threshold (MT) for a total of 1600 pulses each. Before and after rTMS, the cortical excitability was assessed by measuring MT and the size of motor evoked potentials (MEPs) collected at different intensities of stimulation. Results: The analysis on the whole population showed…
Reanimation of the Paralyzed Human Larynx With an Implantable Electrical Stimulation Device
2003
Objectives/Hypothesis Electrical stimulation of the posterior cricoarytenoid muscle, when paced with inspiration, offers a physiological approach to restore ventilation in bilateral laryngeal paralysis without any of the disadvantages associated with conventional treatment. Study Design A prospective study of six patients. Methods The patients were successfully implanted with an Itrel II stimulator (Medtronic, Inc). In postoperative sessions, stimulated vocal fold abduction, patient ventilation, and voice were assessed and compared with preoperative values. Results The optimum stimulus paradigm was a 1- to 2-second train of 1-millisecond pulses delivered at a frequency of 30 to 40 Hz and am…