Relationship between the surface e.m.g. and muscular force

A novel sEMG-based force estimation method using deep-learning algorithm

This paper discusses the problem of force estimation represented by surface electromyography (sEMG) signals collected from an armband-like collection device. The scheme is proposed for the sake of two dimensions of sEMG signals: spatial and temporal information. From the point of space, first, appropriate channel number across all subjects is investigated. During this progress, an electrode channel selection method based on Spearman’s rank order correlation coefficient is utilized to detect signals from active muscle. Then, to reduce the computation and highlight the channel information, linear regression (LR) algorithm is conducted to weight each channel. Besides, the recurrent neural network (RNN) is used to capture the temporal information and model the relation between sEMG and output force. Experiments conducted on four subjects demonstrate that six channels are enough to characterize the muscle activity. By combining the selected channels with different weight coefficients, LR algorithm can fit the output force better than simply averaging them. Furthermore, RNN with long short-term memory cell shows the superiority in time series modeling, which can improve our results to a greater degree. Experimental results prove the feasibility of the proposed method.

Study of issues in the development of surface EMG controlled human hand

In the process of improvement of prosthetic devices, there have been efforts to develop satisfactorily working artificial hands but still lots of work is to be done to meet the accuracy and requirements of the human hand movement. The EMG signal has been most promising signal in development of artificial limbs. The present review paper gives the historical developments in three main sections. First part describes the EMG signal properties. Second part deals with the mathematical models developed till now for EMG signal analysis. In the third part different design approaches have been reviewed for artificial hand. First approach discussed here is on the body-powered terminal devices which are controlled by the user's pull on the control cable to open the hand or hook and for the grip strength. Other being myoelectric controls type, an externally-powered system which uses electrical impulses, generated by contraction of the amputees own remaining muscles to operate a motor in a mechanical hand, hook or elbow. This paper presents a brief overview of above mentioned issues with regard to artificial hands.

The relationship between the electromyogram-amplitude and isometric extension torques of neck muscles at different positions of the cervical spine

A group of 12 healthy men volunteered for the experiment. Electromyograms (EMG) were obtained from semispinalis capitis, splenius capitis, levator scapulae, and trapezius muscles. The flexion angle of the cervical spine was precisely adjusted to 0 degrees, 10 degrees, 20 degrees, and 30 degrees relative to the horizontal, with a constant angle of the atlanto-occipital joint. The subjects made eight short (about 2 s) vertical extension forces (6%, 12%, 18%, 24%, 30%, 36%, 42%, and 48% of maximal voluntary peak contraction force). For each position, the centre of pressure under the head was determined as the basis for the calculation of the external lever arm. The presence of motor endplate regions was ascertained by multiple surface electrodes. The slopes of individual linear regression lines for the root mean square (rms)-values were dependent on the existence of endplates in the area of the electrodes - endplates caused smaller rms values per Newton metres of external torque. Significant intersubject differences between regression equations could not be eliminated by the normalization of EMG-parameters and/or torques. The elimination of gravity, the continuous monitoring of positions, and the consideration of localization of motor endplate regions were essential prerequisites for the acquisition of reliable relationships between EMG of different neck muscles and external torques. Two important conclusions were derived for the prediction of torques from EMG measurements: firstly, individual regression equations which take into account the position of the head and neck should be used; secondly, normalization procedures do not justify the application of average regressions to a group of subjects.

Behavioral medicine treatment in chronic constipation with paradoxical anal sphincter contraction

Nine women and five children with severe chronic constipation received behavioral medicine therapy. Before treatment, all patients had a paradoxical contraction of the external anal sphincter at defecation attempts as demonstrated with electromyography and/or anorectal manometry. An electromyographic biofeedback device connected to an anal probe was used for the training that was performed on a regular toilet seat during five 1-hour sessions. Thirteen of the patients improved considerably and could learn to defecate spontaneously, and the use of laxatives ceased or diminished. Simultaneously with improvement, the paradoxical anal contraction disappeared. The results remained after 6 months, although two of the patients had received booster sessions of biofeedback training during follow-up.

Relation between electromyogram and torque of isometric reflex contractions in man

Human subjects maintained isometric plantar or dorsal flexions of the ankle in a matching task. H-reflexes of different sizes were superimposed on the steady activity. The peak-to-peak amplitude of the reflexes was measured on the electromyogram (EMG) of the soleus muscle. The size of the corresponding muscle contractions was determined on the isometric torque signal in relation to the maintained flexion force. The EMG-torque relation which was defined as the reflex muscle contraction as a function of the EMG reflex signal approximated a square root function for a given steady contraction level. It was not modulated by steady dorsal flexions, but it decreased continuously with stronger plantar steady torques. This dependence was caused by the silent period following the reflex discharge. Since the reflex discharge and the silent period were near in time to the duration of the contraction, the silent period had a direct effect on the reflex contraction amplitude.

Comparison of acoustic and electrical signals from erectores spinae muscles

Comparison was made between simultaneous recordings of the electromyogram (EMG) and acoustic myogram (AMG) signals and the torque produced by the lumbar erectores spinae muscles of three healthy subjects while they performed isometric contractions. Repeatability of each signal was studied. The AMG had a relationship to the torque which was more quadratic than linear, whereas that of the EMG was more linear. The coefficient of variability of residuals about a "best-fit" line was 8.55% for torque-increasing EMG recordings and 19.2% for torque-increasing AMG recordings. At the same torque, the EMG was on average about 10% greater for increasing-torque recordings than for decreasing-torque parts of the recordings, but the magnitude of the AMG signal was about 10% less. With repeated testing on the same day, the coefficient of variability of the signal/torque relationship (torque-increasing) was 9% for EMG and 23% for AMG signals. With long-term testing over 2 weeks these coefficients were 23 and 39%, respectively. Correlation analysis showed that the two signal/torque relationships varied independently of each other.