Search results for "electromyography"
showing 10 items of 672 documents
Force and EMG power spectrum during and after eccentric and concentric fatigue.
2000
Eccentric and concentric force and median frequency of the EMG power spectrum were measured during and immediately after maximal eccentric (EE) and concentric (CE) exercise and during the recovery period of 1 week. Eight male subjects performed EE and CE consisting of 100 maximal eccentric and concentric actions with elbow flexors during two separate exercise sessions. When comparing maximal eccentric and concentric actions before the exercises, the average force was higher (P<0.001) in eccentric than in concentric but the average rectified EMG (aEMG) values were the same with the two types of action. The average eccentric force decreased 53.3% after EE and 30.6% after CE, while the average…
Effects of power training on muscle structure and neuromuscular performance
2005
The present study examines changes in muscle structure and neuromuscular performance induced by 15 weeks of power training with explosive muscle actions. Twenty-three subjects, including 10 controls, volunteered for the study. Muscle biopsies were obtained from the gastrocnemius muscle before and after the training period, while maximal voluntary isometric contractions (MVC) and drop jump tests were performed once every fifth week. No statistically significant improvements in MVC of the knee extensor (KE) and plantarflexor muscles were observed during the training period. However, the maximal rate of force development (RFD) of KE increased from 18,836+/-4282 to 25,443+/-8897 N (P0.05) durin…
Electrophysiological Investigations of Shape and Reproducibility of Oropharyngeal Swallowing: Interaction with Bolus Volume and Age
2015
Electrophysiological assessment provides valuable information on physiological and pathophysiological characteristics of human swallowing. Here, new electrophysiological measures for the evaluation of oropharyngeal swallowing were assessed: (1) the activation pattern of the submental/suprahyoid EMG activity (SHEMG); (2) the reproducibility of the oral and pharyngeal phases of swallowing, by calculating the similarity index (SI) of the SHEMG (SI-SHEMG) and of the laryngeal-pharyngeal mechanogram (SI-LPM) during repeated swallows; and (3) kinesiological measures related to the LPM. An electrophysiological-mechanical method for measuring the activation pattern of the SHEMG, the SI-SHEMG, and t…
Brain Function and Upper Limb Outcome in Stroke: A Cross-Sectional fMRI Study
2015
Objective The nature of changes in brain activation related to good recovery of arm function after stroke is still unclear. While the notion that this is a reflection of neuronal plasticity has gained much support, confounding by compensatory strategies cannot be ruled out. We address this issue by comparing brain activity in recovered patients 6 months after stroke with healthy controls. Methods We included 20 patients with upper limb paresis due to ischemic stroke and 15 controls. We measured brain activation during a finger flexion-extension task with functional MRI, and the relationship between brain activation and hand function. Patients exhibited various levels of recovery, but all we…
Gait-dependent motor memory facilitation in covert movement execution
2004
In the current study, we examined whether sensorimotor information stored in short-term memory may influence the temporal features between overt and covert execution of human locomotor movements and, furthermore, to examine to what extent such influence may depend on the ongoing gait activity. The subjects (n=20) who participated in the experiment were separated in two groups and instructed to walk (overt execution) or imagine walking (covert execution) along three locomotor paths: horizontal, uphill and downhill. The subjects of the first group, labeled in block, performed all the covert trials before executing the corresponding overt trials, while the subjects of the second group, labeled…
Motor Unit Firing Behaviour of Soleus Muscle in Isometric and Dynamic Contractions
2012
Introduction. Understanding the detailed control of human locomotion and balance can be improved, when individual motor units can be isolated and their firing rates followed in natural movement of large, fuctionally important muscles. For this reason the present study investigated the motor unit discharge rate (MUDR) in isometric and dynamic contractions of the soleus muscle. Methods: Eleven males performed isometric (10–100% MVC) and dynamic (10–40% MVC) plantar flexions. Intramuscular EMG was measured from Soleus with bipolar wire-electrodes and decomposed with custom built “Daisy” software. Results. The Soleus MUDR was significantly higher in concentric compared to isometric or eccentric…
Multi-channel electromyography during maximal isometric and dynamic contractions.
2013
Motor unit behavior differs between contraction types at submaximal contraction levels, however is challenging to study during maximal voluntary contractions (MVCs). With multi-channel surface electromyography (sEMG), mean physiological characteristics of the active motor units can be extracted. Two 8-electrode sEMG arrays were attached on biceps brachii muscle (one on each head) to examine behavior of sEMG variables during isometric, eccentric and concentric MVCs of elbow flexors in 36 volunteers. On average, isometric (364 ± 88N) and eccentric (353 ± 74N) MVCs were higher than concentric (290 ± 73N) MVC (p0.001). Mean muscle fiber conduction velocity (CV) was highest during eccentric MVC …
Neuromuscular Fatigue Following Isometric Contractions with Similar Torque Time Integral
2014
International audience; Torque time integral (TTI) is the combination of intensity and duration of a contraction. The aim of this study was to compare neuromuscular alterations following different isometric sub-maximal contractions of the knee extensor muscles but with similar TTI. Sixteen participants performed 3 sustained contractions at different intensities (25 %, 50 %, and 75 % of Maximal Voluntary Contraction (MVC) torque) with different durations (68.5 +/- 33.4 s, 35.1 +/- 16.8 s and 24.8 +/- 12.9 s, respectively) but similar TTI value. MVC torque, maximal voluntary activation level (VAL), M-wave characteristics and potentiated doublet amplitude were assessed before and immediately a…
Impaired action potential conduction at high force levels after eccentric exercise
2010
High-density surface electromyography was used to examine whether gross sarcolemmal function is impaired in m. biceps brachii after intensive eccentric elbow flexor exercise, when measured at wide range of isometric contraction levels. Root mean square (RMS), mean power frequency (MNF) and mean muscle fibre conduction velocity (CV) were calculated before and up to four days post-exercise. Maximal isometric voluntary (MVC) force decreased by 21.3+/-5.6% two hours after exercise, and by 12.6+/-11.1% two days post-exercise. CV and MNF decreased both during MVC (CV from 4.1+/-0.3m/s to 3.8+/-0.4m/s and MNF from 92.6+/-10 Hz to 85.2+/-11 Hz) and during electrically evoked maximal M-wave (CV from…
Progressive versus rapid rate of contraction during 7 wk of isometric resistance training.
2001
The aim of this study was to compare the effects of isometric training performed with progressive versus rapid rate of contraction on the knee extensor neuromuscular properties over a 7-wk period.Sixteen healthy male subjects trained quadriceps femoris muscle in a leg extension machine three times a week during 7 wk. The training sessions consisted of six sets of six maximal isometric contractions. A first group trained by performing progressive contractions lasting 4 s, whereas a second group performed contractions with a rapid rate of contraction (i.e., ballistic contractions) lasting about 1 s.Both groups significantly increased the isometric and isokinetic voluntary torque, and the resp…