This tutorial intends to provide insight, instructions and “best practices” for those who are novices—including clinicians, engineers and non-engineers—in extracting electromyogram (EMG) amplitude ...from the bipolar surface EMG (sEMG) signal of voluntary contractions. A brief discussion of sEMG amplitude extraction from high density sEMG (HDsEMG) arrays and feature extraction from electrically elicited contractions is also provided.
This tutorial attempts to present its main concepts in a straightforward manner that is accessible to novices in the field not possessing a wide range of technical background (if any) in this area. Surface EMG amplitude, also referred to as the sEMG envelope often implemented as root mean square (RMS) sEMG or average rectified value (ARV) sEMG, quantifies the voltage variation of the sEMG signal and is grossly related to the overall neural excitation of the muscle and to peripheral parameters.
The tutorial briefly reviews the physiological origin of the voluntary sEMG signal and sEMG recording, including electrode configurations, sEMG signal transduction, electronic conditioning and conversion by an analog-to-digital converter. These topics have been covered in greater detail in prior tutorials in this series. In depth descriptions of state-of-the-art methods for computing sEMG amplitude are then provided, including guidance on signal pre-conditioning, absolute value vs. square-law detection, selection of appropriate sEMG amplitude smoothing filters and attenuation of measurement noise. The tutorial provides a detailed list of best practices for sEMG amplitude estimation.
In this paper, Dr. Joan Stevenson's work on assessment of the effects of lifting, supporting and transporting loads is reviewed. A defining attribute of this work is the use of objective, ...biomechanical measures as the basis from which a fuller understanding of all factors affecting worker performance can be obtained, and how such performance should be measured and evaluated.
The central objectives and conclusions of Dr. Stevenson's research programs spanning the years from 1985 through 2012 are summarized and discussed in terms of an overall research trajectory.
The guiding principle of Dr. Stevenson's work is to reduce the potential harm to which workers are exposed through the development of bona fide occupational standards, a better understanding of risk factors leading to low back pain, and the establishment of an enhanced objective design process for functional load-bearing clothing and equipment.
The Defence Research and Development Canada-Toronto managed a collaborative team of designers, biomechanists, ergonomists and military stakeholders in the development of a new personal load carriage ...(LC) system for the Canadian Forces. Ergonomics design principles using objective measurement tools and user-centred feedback from soldiers were considered essential to system development. The purpose of this study was to provide a detailed report of contributions by biomechanical testing to the final design of the final Canadian LC system. The Load Carriage Simulator and Compliance Tester were used to test design iterations of: three fragmentation vests, seven tactical vests and three iterations of the backpack. Test data were compared to a data pool of seventeen previously tested systems. Results indicated that the objective measures helped the design team by: (1) quantifying and understanding the consequences of various design changes; (2) predicting soldiers' responses to design changes in skin contact pressure, force and relative motion; (3) objectively comparing design iterations to other systems; and (4) providing information quickly so that ideas and recommendations could be incorporated into the next design iteration. It was concluded that objective assessments added valuable information not easily interpreted from human trials. However, objective assessments cannot replace human trials for feedback on functionality and features.
It has recently been shown that it is possible to discriminate accurately among myoelectric signals underlying different muscle contraction types, specifically elbow flexion and extension and forearm ...pronation and supination. It was reported that once a number of distinctive features had been extracted from the myoelectric signals, a neural network could be trained to distinguish the contraction types with an impressively high accuracy. In the present paper, we show that a technique known as parallel cascade identification can be used to construct classifiers that can also accurately differentiate the contraction types. The use of parallel cascades has the benefit of dispensing with the need for feature extraction, so that raw myoelectric signal data can be used directly. In addition, very little data are required to train the parallel cascades to distinguish accurately novel incoming myoelectric signals. Results of using parallel cascades to distinguish forearm pronation, supination, and elbow flexion are presented.
Cross-correlation is often used as the primary technique to compare two biological signals. Cross-correlation is an effective means to measure the synchronization of two signals assuming the relative ...phases of all frequencies are distributed linearly, that is, a group delay. The group delay assumption imposes an unfavorable restriction on signals with varying relative phase correlation at different frequencies. The traditional Fourier technique provides phase information for each frequency component, but it is not suitable for biological signals with non-stationary statistics. The application of a wavelet based phase analysis technique is discussed in this study. The frequency decomposition and temporally localized nature of the wavelet transform provides localized phase-frequency information for two signals. The merits and weaknesses of using the wavelet relative phase pattern for determining the synchronization of surface electromyographic signals from two muscle sites is discussed.
We propose a methodology to estimate subject-specific physiological parameters of Hill-based models of upper arm muscles. The methodology uses Hill-type candidate functions in the Fast Orthogonal ...Search (FOS) method to predict force at the wrist during elbow flexion and extension. To this end, surface EMG data from three muscles of the upper arm were recorded from 5 subjects as they performed isometric contractions at different elbow joint angles. Estimated muscle activation level and joint angle were utilized as inputs to the FOS model to obtain subject-specific estimates of optimal joint angle the Gaussian shape parameter for the force-length relationship for each muscle.
A computer program, which was developed to train and assess child upper limb amputees in the use of myoelectric control, is described. The program permits a user to open and close a graphic hand ...using myoelectric control and automatically saves assessment results. The program was designed to be entertaining for children and easy to use for therapists. Preliminary testing of the program was done with 15 nonamputee adult volunteers. The results indicate that the program is a useful tool for myoelectric training and assessment. All subjects improved at myoelectric control, the improvement being greater at the beginning of a 10 day training period than at the end of it. The use of the dominant versus nondominant arm for control did not have any effect, and the error most commonly produced was undershooting.< >
Myoelectric signal (MES) data were obtained from remnant muscles in residual upper limbs and analogous intact muscles of thirty-two upper-limb deficient subjects. Spectral parameters (mean frequency, ...median frequency, and equivalent statistical bandwidth) of the MES were calculated and examined for significant differences between the remnant muscle data and intact muscle data. Other factors were examined for possible significant effect on the spectral content of the MES. Although no pattern of spectral difference between the MES of residual versus intact limb muscles was found, spectral differences were apparent by visual inspection in most cases. Level of amputation (above elbow or below elbow) was the sole factor found to have a significant effect on the MES spectral content. Data were separated based on level of amputation; no statistically significant difference between the spectral parameters of residual versus intact muscle MES was found. However, greater variation in the spectral parameters of the remnant muscle data was observed. The results of this study add to one's knowledge of the MES characteristics of remnant muscles, with implications for the design of myoelectric controllers.< >
In an HL-60 cell subline (PR-17) which was greater than 100-fold resistant to the differentiating and cytostatic activities
of phorbol 12-myristate 13-acetate (PMA), the protein kinase C phenotype ...was found to be nearly identical to that of wild-type
HL-60 cells. A measurable decrease (30%) in the specific activities of crude preparations of PR-17 cell protein kinase C was
observed when the enzyme was measured with histone as the phosphate acceptor substrate, but other aspects of the protein kinase
C phenotype (intracellular concentrations and binding affinities of phorbol diester receptors, translocation of activated
enzyme from cytosolic to particulate subcellular fractions, relative expression of the alpha and beta isozyme proteins) were
equivalent in both PMA-resistant PR-17 cells and in wild-type HL-60 cells. Direct analysis of the behavior of the alpha and
beta isozymes after the exposure of each cell type to 100 nM PMA for 12 h revealed that the activities and intracellular concentrations
of both isozymes were downregulated to an equivalent extent in both wild-type and PMA-resistant cells. These results suggest
that the cellular basis for the resistance to the effects of PMA was present "down-stream" from the activation and down-regulation
of protein kinase C and was perhaps a nuclear component. Among the genes which were likely to be differentially regulated
when each of the two cell lines were treated with PMA were those for the protein kinase C isozymes themselves. In wild-type
HL-60 cells, the intracellular concentrations of type HL-60 cells, the intracellular concentrations of mRNA for each of the
beta isozymes were increased (up to 5-fold) 48 h after the initiation of PMA treatment; further studies indicate that an activator
of protein kinase C could influence the expression of HL-60 cell protein kinase C genes in an isozyme-specific manner. Comparable
PMA-induced alterations in mRNA levels were not observed in PMA-resistant cells, even under conditions of significant activation
and subsequent down-regulation of protein kinase C protein. Taken together, these data suggest that activation and down-regulation
of the isozymes of protein kinase C may not represent absolute determinants of the PMA-induced differentiation of HL-60 cells,
but that specific alterations in the levels of the mRNA for the beta isozymes of protein kinase C, or of other genes which
may be regulated by the activated kinase isozymes, are important to the induction of leukemia cell differentiation by PMA.
The myoelectric signal has played a major role in the development of prosthesis control technology. A myoelectric classification system has the ability to determine a prosthesis user's intent based ...solely on his or her muscle activity, thereby allowing for more intuitive prosthetic control. Much work has been done on the recognition of upper arm and gross hand movement tasks, but it was not until accuracy levels approached 100% 3 that more attention was given to specific finger movements. In this study, the effect of electrode array size and arrangement on classification accuracy is investigated for a four-finger typing task. This follows from previous work 1 in which the classification system itself was optimized. Unique advantages were found using array sizes of three and seven electrodes; classification accuracy of 92.7plusmn3.9% was found in the latter case across twelve subjects.
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