Power spectral analysis of surface EMG in stroke: A preliminary study (original) (raw)
Related papers
Journal of Electromyography and Kinesiology, 2018
After a stroke, motor units stop working properly and large, fast-twitch units are more frequently affected. Their impaired functions can be investigated during dynamic tasks using electromyographic (EMG) signal analysis. The aim of this paper is to investigate changes in the parameters of the power/frequency function during elbow flexion between affected, nonaffected, and healthy muscles. Fifteen healthy subjects and ten stroke survivors participated in the experiments. Electromyographic data from 6 muscles of the upper limbs during elbow flexion were filtered and normalized to the amplitudes of EMG signals during maximal isometric tasks. The moments when motion started and when the flexion angle reached its maximal value were found. Equal intervals of 0.3407 s were defined between these two moments and one additional interval before the start of the flexion (first one) was supplemented. For each of these intervals the power/frequency function of EMG signals was calculated. The mean 2 (MNF) and median frequencies (MDF), the maximal power (MPw) and the area under the power function (APw) were calculated. MNF was always higher than MDF. A significant decrease in these frequencies was found in only three post-stroke survivors. The frequencies in the first time interval were nearly always the highest among all intervals. The maximal power was nearly zero during first time interval and increased during the next ones. The largest values of MPw and APw were found for the flexor muscles and they increased for the muscles of the affected arm compared to the non-affected one of stroke survivors.
Clinical Neurophysiology, 2014
Muscle fatigue in the anterior temporal and masseter muscles of 13 normal subjects was induced by maximum clench in intercuspal position. Frequency analysis using a fast Fourier transform algorithm to obtain the power-spectral density function and the power spectrum of the electromyogram signal indicated that the power spectra obtained during fatigue were statistically significantly shifted to lower frequencies and narrower than those obtained at the beginning of the clench. The shift was due to a significant increase of the power in the lowfrequency range and a significant decrease of that in the high-frequency range. The powerspectrum shift to lower frequencies had an exponential time course. The most pronounced shift occurred in the first 25 per cent of the total clenching time. Decrease of the conduction velocity of the action potential along the muscle fibre seems to be the main cause of the shift.
Intramuscular and surface EMG power spectrum from dynamic and static contractions
Journal of Electromyography and Kinesiology, 1995
During sustained static contractions an increase in the root mean square (rms) amplitude and a decrease in mean power frequency (MPF), or median power frequency (MF) of the electromyographic (EMG) signal are indicators for the development of muscle fatigue. However, when studying dynamic contractions the interpretation of these variables has been questioned. Therefore, the purpose was to compare the EMG variables recorded from a non-fatigued muscle during a slow low level dynamic contraction to those during a static contraction of similar force level. Surface and intramuscular EMG registrations were obtained from the brachial biceps muscle during: (a) a static isotonic contraction, (b) a dynamic contraction and (c) a static anisotonic contraction. During contractions (a) and (b) the recruitment pattern was analysed using the precision decomposition method. No differences in rms, MPF or MF between the dynamic and static contractions or between the concentric and eccentric phase of the dynamic contraction were found. Furthermore 60% of the identified motor units were active both in the concentric and the eccentric phase. This indicates that motor control during a slow dynamic contraction at low force level does not influence the power spectrum. We suggest that in occupational studies a possible muscle fatigue development with time can be estimated using EMG recordings from the work tasks.
Re-evaluation of EMG-torque relation in chronic stroke using linear electrode array EMG recordings
Scientific reports, 2016
The objective was to re-evaluate the controversial reports of EMG-torque relation between impaired and non-impaired sides using linear electrode array EMG recordings. Ten subjects with chronic stroke performed a series of submaximal isometric elbow flexion tasks. A 20-channel linear array was used to record surface EMG of the biceps brachii muscles from both impaired and non-impaired sides. M-wave recordings for bilateral biceps brachii muscles were also made. Distribution of the slope of the EMG-torque relations for the individual channels showed a quasi-symmetrical "M" shaped pattern. The lowest value corresponded to the innervation zone (IZ) location. The highest value from the slope curve for each side was selected for comparison to minimize the effect of electrode placement and IZ asymmetry. The slope was greater on the impaired side in 4 of 10 subjects. There were a weak correlation between slope ratio and strength ratio and a moderate to high correlation between slo...
Study of electromyographic signal in stroke patients
2014
With the rapid development of mathematical tools related to research on human behavior, more and more new discoveries are appeared in domestic and foreign. Surface EMG is a complex biological electrical signals and carrying a large body of information. In this paper, we found that the electromyographic signal is controlled by the brain signals and superposition of limb muscle action potential signal. The focus of this paper is to use mathematical analysis tools and MATLAB software to analyze the performance characteristics of EMG. Through the analysis of the electromyographic signal, we can quickly identify a breakdown of the patients with cerebral apoplexy, and it is cerebral infarction or cerebral hemorrhage, greatly improve the cure rate and reduce mortality. We have gathered upper limb muscle electrical signals of healthy people, patients with cerebral infarction and cerebral hemorrhage patients. By using Fourier transform and AR model to analyze electromyographic signal, we can easily find the difference between the patients with cerebral infarction and cerebral hemorrhage patients.
Muscle & Nerve, 2009
Motor unit (MU) properties of the biceps brachii and Fugl-Meyer score were assessed in stroke patients and healthy controls during passive and active elbow flexion and extension contractions. The level of motor recovery as assessed with the Fugl-Meyer score was correlated with the ratio of the size of the motor unit action potentials (MUAPs) at the affected side and the unaffected side. This ratio may reflect the extent to which reinnervation has occurred on the affected side. The RMS value of the MUAPs recruited during the stretch phase of the passive contractions was lower than the RMS value of MUAPs recruited during active contractions. This may indicate that only smaller MUs are affected by increased sensitivity to muscle stretch while a larger part of the MU pool can be recruited voluntarily.
Journal of Neural Engineering, 2015
Objective. The advancement of surface electromyogram (sEMG) recording and signal processing techniques has allowed us to characterize the recruitment properties of a substantial population of motor units (MUs) non-invasively. Here we seek to determine whether MU recruitment properties are modified in paretic muscles of hemispheric stroke survivors. Approach. Using an advanced EMG sensor array, we recorded sEMG during isometric contractions of the first dorsal interosseous muscle over a range of contraction levels, from 20% to 60% of maximum, in both paretic and contralateral muscles of stroke survivors. Using MU decomposition techniques, MU action potential amplitudes and recruitment thresholds were derived for simultaneously activated MUs in each isometric contraction. Main results. Our results show a significant disruption of recruitment organization in paretic muscles, in that the size principle describing recruitment rank order was materially distorted. MUs were recruited over a very narrow force range with increasing force output, generating a strong clustering effect, when referenced to recruitment force magnitude. Such disturbances in MU properties also correlated well with the impairment of voluntary force generation. Significance. Our findings provide direct evidence regarding MU recruitment modifications in paretic muscles of stroke survivors, and suggest that these modifications may contribute to weakness for voluntary contractions.
IEEE transactions on bio-medical engineering, 2014
Recent advances in high density surface electromyogram (EMG) decomposition have made it a feasible task to discriminate single motor unit activity from surface EMG interference patterns, thus providing a noninvasive approach for examination of motor unit control properties. In the current study we applied high density surface EMG recording and decomposition techniques to assess motor unit firing behavior alterations post-stroke. Surface EMG signals were collected using a 64-channel 2-dimensional electrode array from the paretic and contralateral first dorsal interosseous (FDI) muscles of nine hemiparetic stroke subjects at different isometric discrete contraction levels between 2 N to 10 N with a 2 N increment step. Motor unit firing rates were extracted through decomposition of the high density surface EMG signals, and compared between paretic and contralateral muscles. Across the nine tested subjects, paretic FDI muscles showed decreased motor unit firing rates compared with contr...
Motor unit structural change post stroke examined via surface electromyography: A preliminary report
2013 6th International IEEE/EMBS Conference on Neural Engineering (NER), 2013
Muscular weakness is one of the major impairments limiting motor function following a hemispheric stroke. The objective of this preliminary study was to examine possible motor unit (MU) structural changes in paretic muscle post-stroke as a measure by which to assess neural and/or biomechanical mechanisms of paresis. A surface electromyogram (sEMG) recording and decomposition system was used to record sEMG signals and extract single MU activities from the first dorsal interosseous muscle (FDI) of three hemiparetic stroke survivors. To characterize potential MU structural changes, an estimate of the motor unit action potential (MUAP) amplitude and duration was derived using the spike triggered averaging of the sEMG signal. Our preliminary results reveal MUAPs with systematically smaller amplitude and longer duration in the paretic muscle compared with the contralateral muscle of three tested stroke subjects with varying degrees of motor impairment. The changes in MU properties such as reduced MU size and a reduction in the muscle fiber conduction velocity could contribute at least in part, to muscle weakness post-stroke. The sEMG recording and decomposition system combined with our spike triggered averaging technique has the potential to provide an assessment tool for muscular weakness post-stroke. I. INTRODUCTION Cerebral stroke is a leading cause of disability in the United States [1]. After a stroke injury, muscular weakness is one of the major impairments limiting motor function in stroke survivors [2-4]. Possible mechanisms of weakness include reduced excitatory descending drive, muscle atrophy, and disturbance in the control of the MU pool [5-9]. However, the choice as to which mechanisms should be targeted during therapeutic intervention is still unclear, partly due to the insufficient understanding of relative impact of these particular mechanisms [10-12]. Only a few studies have investigated disturbances of MU structural properties, using parameters such as MU size and muscle fiber conduction velocity in paretic muscles of stroke survivors [5, 13, 14] as a means by which to understand the underlying mechanism of weakness. A reduction in MU size
Surface EMG analysis on normal subjects based on isometric voluntary contraction
Journal of Electromyography and Kinesiology, 2009
The objective of this study was to compute reference SEMG values for normal subjects of 13 parameters extracted in the time, frequency and bispectrum domain, from the Biceps Brachii (BB) muscle generated under isometric voluntary contraction (IVC). SEMG signals were recorded from 94 subjects for 5 s at 10, 30, 50, 70 and 100% of maximum voluntary contraction (MVC). The Wilcoxon signed rank test was applied to detect significant differences or not at p < 0.05 between force levels for each of the 13 parameters. The main findings of this study can be summarized as follows: (i) The time domain parameters turns per second and number of zero crossings per second increase significantly with force level. (ii) The power spectrum median frequency parameter decreases significantly with force level, whereas maximum power and total power increase significantly with force level. (iii) The bispectrum parameter, maximum amplitude, increases significantly with force level with the exception the transition from 30% to 50% MVC. Although, the tests for Gaussianity and linearity show no significant difference with force level, the SEMG signal exhibits a more Gaussian distribution with increase of force up to 70% MVC. The SEMG linearity test, which is a measure of how constant the bicoherence index is in the bi-frequency domain, shows that the signal's bicoherence index is less constant (hence, the signal is less linear) at 70% of MVC compared to 10, 30, 50 and 100% MVC. (iv) The time domain parameters have good correlation between them as well as, between each one of them and maximum and total power. The median frequency has a good (negative) correlation with the bispectrum peak amplitude. (v) No significant differences exist between values based on gender or age. The findings of this study can further be used for the assessment of subjects suffering with neuromuscular disorders, or in the rehabilitation laboratory for monitoring the elderly or the disabled, or in the occupational medicine laboratory.