A wireless, minaturized multi-channel sEMG acquisition system for use in dynamic tasks

Nowadays, the detection of surface EMG (sEMG) signals is almost exclusively based on a single or a few electrode pairs. However, in the last two decades limitations of bipolar sEMG signals emerged. To increase the amount and reliability of information extracted from sEMG, linear electrode arrays and two-dimensional detection systems have been proposed. The aim of this work was the development of a wearable wireless, 32- channels sEMG acquisition system. The developed system performs the conditioning, sampling and wireless transmission of 32 monopolar sEMG channels and 3 auxiliary signals, sampled at 2.048ksps with 16 bit resolution. The system wirelessly transmits the acquired signals to either a mobile device (smartphone or tablet with Wi-Fi connectivity) or a personal computer for real time visualization and storage. The developed system has been tested in clinical and sport scenarios showing good performances in wearability and movement artefact robustness

On the Detection of High-Quality, High-Density Electromyograms During 80m Sprints: a Case Study

Surface electromyograms (EMGs) have been often used to study muscle function in locomotor activities. Typically, EMGs are sampled with a single pair of electrodes, providing information on the timing and degree of muscle excitation. Additional information may be obtained when sampling EMGs with multiple electrodes from the same, target muscles. Studies using high-density EMGs (HD-EMGs) in locomotor activities are limited to laboratory settings and low speed tasks, likely due to the technical shortcomings in the commercially available systems for high-density recordings. This issue is further aggravated when kinematics data are necessary for associating EMGs with events of interest during the movement cycle. By combining two systems, ad hoc developed for the on-field recording of kinematics data and HD-EMGs, here we present single-case results during extreme-speed locomotion-the 80 m sprint on an official, athletic track. Our aim was to verify whether descriptors of quality documented in the EMG literature during well-controlled, isometric contractions, apply to the HD-EMGs we detected and segmented with respect to the running cycles. From a single, elite sprinter, we were able to obtain HD-EMGs with negligible movement artifacts and with temporal profiles typically characterizing action potentials of single motor units. Our results would seem to advocate the possibility of using HD-EMG to study muscle function during highly dynamic contractions outside the laboratory settings

Design and Test of a Biomechanical Model for the Estimation of Knee Joint Angle During Indoor Rowing: Implications for FES-Rowing Protocols in Paraplegia

Functional electrical stimulation of lower limb muscles during rowing provides a means for the cardiovascular conditioning in paraplegia. The possibility of shaping stimulation profiles according to changes in knee angle, so far conceived as changes in seat position, may help circumventing open issues associated with muscle fatigue and movement coordination.Here we present a subject-specific biomechanical model for the estimation of knee joint angle during indoor rowing. Anthropometric measurements and foot and seat position are inputs to the model. We tested our model on two samples of elite rowers; 15 able-bodied and 11 participants in the Rio 2016 Paralympic games. Paralympic rowers presented minor physical disabilities (LTA-PD classification), enabling them to perform the full rowing cycle (with legs, trunks and arms). Knee angle was estimated from the rowing machine seat position, measured with a linear encoder and transmitted wirelessly to a computer. Key results indicate the root mean square error (RMSE) between estimated and measured angles did not depend on group and stroke rate (p>0.267). Significantly greater RMSE values were observed however within the rowing cycle (p<0.001), reaching on average 8deg in the mid-recovery phase. Differences between estimated and measured knee angle values resulted in slightly earlier (5%) detection of knee flexion, regardless of the group and stroke rate considered. Offset of knee extension, knee angle at catch and range of knee motion were identified equally well with our model and with inertial sensors. These results suggest our model describes accurately the movement of knee joint during indoor rowing

Electrodes' Configuration Influences the Agreement Between Surface EMG and B-Mode Ultrasound Detection of Motor Unit Fasciculation

Muscle fasciculations, resulting from the spontaneous activation of motor neurons, may be associated with neurological disorders, and are often assessed with intramuscular electromyography (EMG). Recently, however, both ultrasound (US) imaging and multichannel surface EMG have been shown to be more sensitive to fasciculations. In this study we combined these two techniques to compare their detection sensitivity to fasciculations occurring in different muscle regions and to investigate the effect of EMG electrodes' configuration on their agreement. Monopolar surface EMGs were collected from medial gastrocnemius and soleus with an array of 32 electrodes (10 mm Inter-Electrode Distance, IED) simultaneously with b-mode US images detected alongside either proximal, central or distal electrodes groups. Fasciculation potentials (FP) were identified from single differential EMGs with 10 mm (SD1), 20 mm (SD2) and 30 mm (SD3) IEDs, and fasciculation events (FE) from US image sequences. The number, location, and size of FEs and FPs in 10 healthy participants were analyzed. Overall, the two techniques showed similar sensitivities to muscle fasciculations. US was equally sensitive to FE occurring in the proximal and distal calf regions, while the number of FP revealed by EMG increased significantly with the IED and was larger distally, where the depth of FE decreased. The agreement between the two techniques was relatively low, with a percentage of fasciculation classified as common ranging from 22% for the smallest IED to 68% for the largest IED. The relevant number of events uniquely detected by the two techniques is discussed in terms of different spatial sensitivities of EMG and US, which suggest that a combination of US-EMG is likely to maximise the sensitivity to muscle fasciculations

Are the forearm muscles excited equally in different, professional piano players?

Background and objectives Professional pianists tend to develop playing-related musculoskeletal disorders mostly in the forearm. These injuries are often due to overuse, suggesting the existence of a common forearm region where muscles are often excited during piano playing across subjects. Here we use a grid of electrodes to test this hypothesis, assessing where EMGs with greatest amplitude are more likely to be detected when expert pianists perform different excerpts. Methods Tasks were separated into two groups: classical excerpts and octaves, performed by eight, healthy, professional pianists. Monopolar electromyograms (EMGs) were sampled with a grid of 96 electrodes, covering the forearm region where hand and wrist muscles reside. Regions providing consistently high EMG amplitude across subjects were assessed with a non-parametric permutation test, designed for the statistical analysis of neuroimaging experiments. Spatial consistency across trials was assessed with the Binomial test. Results Spatial consistency of muscle excitation was found across subjects but not across tasks, confining at most 20% of the electrodes in the grid. These local groups of electrodes providing high EMG amplitude were found at the ventral forearm region during classical excerpts and at the dorsal region during octaves, when performed both at preferred and at high, playing speeds. Discussion Our results revealed that professional pianists consistently load a specific forearm region, depending on whether performing octaves or classical excerpts. This spatial consistency may help furthering our understanding on the incidence of playing-related muscular disorders and provide an anatomical reference for the study of active muscle loading in piano players using surface EMG

A high-performance 8 nV/root Hz 8-channel wearable and wireless system for real-time monitoring of bioelectrical signals

Background: It is widely accepted by the scientific community that bioelectrical signals, which can be used for the identification of neurophysiological biomarkers indicative of a diseased or pathological state, could direct patient treatment towards more effective therapeutic strategies. However, the design and realisation of an instrument that can precisely record weak bioelectrical signals in the presence of strong interference stemming from a noisy clinical environment is one of the most difficult challenges associated with the strategy of monitoring bioelectrical signals for diagnostic purposes. Moreover, since patients often have to cope with the problem of limited mobility being connected to bulky and mains-powered instruments, there is a growing demand for small-sized, high-performance and ambulatory biopotential acquisition systems in the Intensive Care Unit (ICU) and in High-dependency wards. Finally, to the best of our knowledge, there are no commercial, small, battery-powered, wearable and wireless recording-only instruments that claim the capability of recording electrocorticographic (ECoG) signals. Methods: To address this problem, we designed and developed a low-noise (8 nV/√Hz), eight-channel, battery-powered, wearable and wireless instrument (55 × 80 mm2). The performance of the realised instrument was assessed by conducting both ex vivo and in vivo experiments. Results: To provide ex vivo proof-of-function, a wide variety of high-quality bioelectrical signal recordings are reported, including electroencephalographic (EEG), electromyographic (EMG), electrocardiographic (ECG), acceleration signals, and muscle fasciculations. Low-noise in vivo recordings of weak local field potentials (LFPs), which were wirelessly acquired in real time using segmented deep brain stimulation (DBS) electrodes implanted in the thalamus of a non-human primate, are also presented. Conclusions: The combination of desirable features and capabilities of this instrument, namely its small size (~one business card), its enhanced recording capabilities, its increased processing capabilities, its manufacturability (since it was designed using discrete off-the-shelf components), the wide bandwidth it offers (0.5 – 500 Hz) and the plurality of bioelectrical signals it can precisely record, render it a versatile and reliable tool to be utilized in a wide range of applications and environments

A Wearable and Modular System for Neuromuscular System Assessment and Motor Rehabilitation

L'abstract è presente nell'allegato / the abstract is in the attachmen

Development of a wireless system for the remote monitoring of muscular activity

INTRODUCTION The study and the analysis of the human movements require the acquisition of kinematic, dynamics and electrophysiological variables. Among them, the electromyographic signal (EMG) plays a fundamental role to monitor the muscular activity. In the last years, EMG devices composed by a set of wireless modules allowing the detection and transmission of one or more EMG signals to a mobile device, such a tablet or smartphone, have been developed and are now commercially available. The aim of this works is the development of a telemetry wireless system for the detection and real-time monitoring of EMG signals using a wireless body area network (WBAN). METHODS The system architecture (Figure 1) consists of one or more modules, each one detecting two bipolar EMG signals sampled at 2.048kHz with 16 bit resolution. The sampled signals are sent to a mobile device acting as a receiver through a Bluetooth 4.0 link. A web client mobile application, written using the C++ programming language, acquires the data, calculates the EMG envelope and send it to a remote web server using a TCP-IP socket. The web server, written in Python using the Heroku PaaS (Platform as a Service) service, has a permanently opened TCP-IP socket in order to maximize the Internet data throughput. The signals received on the web server, can be displayed in real-time on a website (http://lisinsite.herokuapp.com/) designed using the HTML language and the Highcharts javascript library. RESULTS The system has been successfully tested on two subjects during a marathon organized for the “Just the Woman I Am” event held in Turin on March 2017. The Figure 1.b shows the EMG envelope detected on the medial gastrocnemius muscle of two subjects participating to the marathon. The signals are plotted in a web browser. The mean data throughput observed during the event was 100 kbps. DISCUSSION The main innovation introduced by this system is the ability to real-time monitoring the muscular activity of subjects without constraints on the maximum transmission distance of the detection system worn by the subject. The modular architecture of the system permits the simultaneous use of many detection probes on different subjects. Finally, the system is easy to use and requires only a smartphone and a web browser

Augmented reality system for muscle activity biofeedback

Introduction/Background Augmented Reality (AR) has been proved successful in several applications from surgical training to balance rehabilitation. This work aims to develop an AR system for real-time visualization of an index of muscle activity superimposed to the investigated muscle. Material and method The system includes: (1) a video camera, (2) one or more surface EMG (sEMG) detection/acquisition systems, (3) one processing and visualization unit (Fig. 1). The system integrates the information from the video camera and from the sEMG systems (the ARV of the sEMG signal epoch corresponding to the current video frame) and creates an “augmented video frame” by coloring the detection systems, identified within the video frame, with a color representative of the muscle activity (blue for low and red for high sEMG activity). The patient or the clinical operator can see the real-time augmented video on a display. Results The software can run (1) on a PC using a webcam for video capture and showing the augmented video on a monitor, (2) on a tablet using the integrated camera or (3) on the Epson Moverio BT-300 smartglasses using the see-through modality. Fig. 2 shows the AR feedback during a leg extension exercise; vastus medialis, vastus lateralis and rectus femoralis muscles are monitored using a sEMG bipolar system (Due, OTBioelettronica and LISiN). Fig. 3 shows the AR system used for the monitoring of sEMG activity distribution in the lumbar muscles using a multi-channel sEMG systems (32 channel amplifier by LISiN). Conclusion An AR system for the visualization of sEMG activity over the muscles has been developed. The system is currently under validation for augmented biofeedback in sport and rehabilitation in order to verify advantages with respect to standard biofeedback

Towards the Design of an Impedance-Controlled HD-sEMG Amplifier: A Feasibility Study

The use of multiple surface EMG electrodes (High-Density surface EMG – HD-sEMG) allows the extraction of anatomical and physiological information either at the muscle or at the motor unit level with applications in several fields ranging from clinical neurophysiology to the control of prosthetic devices. These applications need to acquire monopolar sEMG signals free from power line interference arising from the capacitive coupling between the subject, the acquisition system and the power line. The aim of this work is to provide a common mode analysis of the detection system used to collect monopolar sEMG signals, characterizing different configuration of the reference electrodes leading to different behaviors in terms of immunity to the power line interference. Based on the experimental results, a new impedance-controlled HD-sEMG signal amplifier is proposed and discussed