Towards electrodeless EMG linear envelope signal recording for myo-activated prostheses control

After amputation, the residual muscles of the limb may function in a normal way, enabling the electromyogram (EMG) signals recorded from them to be used to drive a replacement limb. These replacement limbs are called myoelectric prosthesis. The prostheses that use EMG have always been the first choice for both clinicians and engineers. Unfortunately, due to the many drawbacks of EMG (e.g. skin preparation, electromagnetic interferences, high sample rate, etc.); researchers have aspired to find suitable alternatives. One proposes the dry-contact, low-cost sensor based on a force-sensitive resistor (FSR) as a valid alternative which instead of detecting electrical events, detects mechanical events of muscle. FSR sensor is placed on the skin through a hard, circular base to sense the muscle contraction and to acquire the signal. Similarly, to reduce the output drift (resistance) caused by FSR edges (creep) and to maintain the FSR sensitivity over a wide input force range, signal conditioning (Voltage output proportional to force) is implemented. This FSR signal acquired using FSR sensor can be used directly to replace the EMG linear envelope (an important control signal in prosthetics applications). To find the best FSR position(s) to replace a single EMG lead, the simultaneous recording of EMG and FSR output is performed. Three FSRs are placed directly over the EMG electrodes, in the middle of the targeted muscle and then the individual (FSR1, FSR2 and FSR3) and combination of FSR (e.g. FSR1+FSR2, FSR2-FSR3) is evaluated. The experiment is performed on a small sample of five volunteer subjects. The result shows a high correlation (up to 0.94) between FSR output and EMG linear envelope. Consequently, the usage of the best FSR sensor position shows the ability of electrode less FSR-LE to proportionally control the prosthesis (3-D claw). Furthermore, FSR can be used to develop a universal programmable muscle signal sensor that can be suitable to control the myo-activated prosthesis

Recent Advances in Motion Analysis

The advances in the technology and methodology for human movement capture and analysis over the last decade have been remarkable. Besides acknowledged approaches for kinematic, dynamic, and electromyographic (EMG) analysis carried out in the laboratory, more recently developed devices, such as wearables, inertial measurement units, ambient sensors, and cameras or depth sensors, have been adopted on a wide scale. Furthermore, computational intelligence (CI) methods, such as artificial neural networks, have recently emerged as promising tools for the development and application of intelligent systems in motion analysis. Thus, the synergy of classic instrumentation and novel smart devices and techniques has created unique capabilities in the continuous monitoring of motor behaviors in different fields, such as clinics, sports, and ergonomics. However, real-time sensing, signal processing, human activity recognition, and characterization and interpretation of motion metrics and behaviors from sensor data still representing a challenging problem not only in laboratories but also at home and in the community. This book addresses open research issues related to the improvement of classic approaches and the development of novel technologies and techniques in the domain of motion analysis in all the various fields of application

Applications of EMG in Clinical and Sports Medicine

This second of two volumes on EMG (Electromyography) covers a wide range of clinical applications, as a complement to the methods discussed in volume 1. Topics range from gait and vibration analysis, through posture and falls prevention, to biofeedback in the treatment of neurologic swallowing impairment. The volume includes sections on back care, sports and performance medicine, gynecology/urology and orofacial function. Authors describe the procedures for their experimental studies with detailed and clear illustrations and references to the literature. The limitations of SEMG measures and methods for careful analysis are discussed. This broad compilation of articles discussing the use of EMG in both clinical and research applications demonstrates the utility of the method as a tool in a wide variety of disciplines and clinical fields

Computational Intelligence in Electromyography Analysis

Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG may be used clinically for the diagnosis of neuromuscular problems and for assessing biomechanical and motor control deficits and other functional disorders. Furthermore, it can be used as a control signal for interfacing with orthotic and/or prosthetic devices or other rehabilitation assists. This book presents an updated overview of signal processing applications and recent developments in EMG from a number of diverse aspects and various applications in clinical and experimental research. It will provide readers with a detailed introduction to EMG signal processing techniques and applications, while presenting several new results and explanation of existing algorithms. This book is organized into 18 chapters, covering the current theoretical and practical approaches of EMG research

Optimizing physical and psychosocial assessment in patients with non-specific chronic low back pain

NS-LBP is defined as pain and discomfort, localized below the costal margin and above the inferior gluteal folds, with or without referred leg pain, that is not attributable to a recognizable, known specific pathology. NS-CLBP involves NS-LBP persisting for at least 12 weeks. In the civilian as well as in the military population NS-CLBP is a common problem with an important impact on the patient’s functioning and on the society. Previous research demonstrated that NS-CLBP is not only caused by physical factors, but the psychosocial factors also play an important role in the onset and perpetuation of NS-CLBP. It is commonly accepted that these patients should be assessed biopsychosocialy. The planetary model is therefore an adequate coat rack in the management of NS-CLBP. To ensure a good outcome, it is primordial to tailor the therapy in function of the patient’s needs. This is only possible after a detailed physical and psychosocial assessment of the patient. Different tools and concepts were proposed to sustain this assessment, but some pitfalls exist. The aim of this doctoral dissertation was to optimize some aspects of the assessment of patients with NS-CLBP, to objectify the patient’s complaints and the associated influencing factors. The project was subdivided in three parts. In the first part trunk muscle recruitment patterns were investigated with sEMG. Literature often described altered trunk recruitment patterns in patients with NS-CLBP. Trunk muscle recruitment patterns were analyzed in terms of ratios of deep stabilizing muscle groups to global torque producing muscles. In Chapter 1 de influence of velocity of isokinetic movement on trunk muscle recruitment patterns was investigated. Fifty-three healthy subjects (26 men and 27 women) performed flexion-extension movements on a Cybex isokinetic dynamometer at different velocities (30°/s, 60°/s, 90°/s, 120°/s). The activity of two deep stabilizing muscle groups (m. obliquus internus abdominis (IO) and the lumbar m. multifidus (LMF)) and two superficial torque producing muscles (m. obliquus externus abdominis (EO) and the m. iliocostalis lumborum pars thoracis (ICLT)) were recorded simultaneously. The relative muscle activity as well the ratios LMF/ICLT and IO/EO were analyzed. Results demonstrated that the relative muscle activity of the different back muscles decreased with increasing velocity, but the LMF was less influenced by velocity than the ICLT, resulting in an increased ratio LMF/ICLT at high velocity. This study did not demonstrate an influence of velocity on the abdominal muscle groups. In Chapter 2 the same ratios were analyzed during 6 sensorimotor control exercises. Sixty-three healthy men and 36 patients with NS-CLBP participated in this study. All patients demonstrated a flexion-related MCI. Based on the trunk muscle recruitment patterns during the 6 exercises a statistical model was developed to discriminate between patients and healthy subjects. This part of the project led to the adjustment of several physical tests of the clinical pathway for NS-CLB at the MHQA. Chapter 1 underlined the importance of the use of different velocities in isokinetic evaluation and treatment of these patients. Chapter 2 provided evidence that trunk muscle recruitment patterns can be measured objectively in patients with flexion-related MCI. This is not only relevant in the clinical practice, but also in research as on objective variable in for example studies investigating the influence of therapy. The second part of the project focused on the improvement of psychosocial evaluation in patients with NS-CLBP. The aim was to optimize the use of self-report questionnaires. Therefore cross-cultural adaptation to Dutch and French was performed for the following questionnaires (Chapter 3): TSK, PHQ-15, QBPDI, OMPQ and the MPIpart1. Based on these and other questionnaires (PCS, DRAM, HADS, SF-36) a battery of self-report questionnaires was developed and long-term test-retest reliability was investigated. Test-retest reliability was analyzed on 48 French-speaking and 43 Dutch-speaking patients with NS-CLBP. Results indicated that scores on most of the questionnaires remained stable over time (> 1 month), except for the SF-36. In Chapter 4, the clinical interpretation of the scores on the questionnaires was facilitated by determining cut-off scores for screening questionnaires (TSK, PHQ-15, OMPQ) on198 patients with NS-CLBP, as well as determining MCIC for evaluative questionnaires (TSK, QBPDI, OMPQ, MPIpart1, SF-36) on 70 patients with NS-CLBP. This part of the study allowed the use of these questionnaires in a French and Dutch-speaking population. Although some waiting time exists between the moment the questionnaire is filled in and the start of the therapy, the clinician may be confident that the scores of the questionnaire are stable over a long period of time (> 1 month), if the patient’s status remains stable. The cut-off scores and the MCIC led to an easy interpretation of the scores and the change in scores. These results are also important in further research. Results of the questionnaires could for example be used as outcome variable in the evaluation of different therapies. The third part of this doctoral project underlined the link between psychosocial and physical evaluation, in the line of existing literature. Chapter 5 gave on example of this. Research was done on the influence of psychosocial factors on performance during two endurance tests for the abdominal and back muscles. Three hundred thirty two patients with NS-CLBP filled in a series of questionnaires. Then they effectuated the Biering-Sorensen back muscle endurance tests (B-S test) and an abdominal endurance test. Simultaneously the muscle activity of the LMF and the ICLT during the B-S test and the IO and the EO during the abdominal endurance test were recorded by sEMG. The time to exhaustion was also recorded. Based on the intrinsic muscle fatigue (normalized slope) the predicted time to exhaustion was calculated for both tests separately. By comparing the real time to exhaustion by the predicted time patients were divided in a performance and an underperformance group. Questionnaire results were compared for both groups. Regression analyses were performed to examine the predictive value of the questionnaires on the time to exhaustion. Results demonstrated that for the B-S test scores on the physical subscales of the SF-36 were lower in the underperformance groups. A higher BMI and low scores on the SF-36PF were significant predictors of low performance on the B-S test (R²=0.10). Concerning the abdominal endurance test, the group patients with low performance had significantly higher scores on the DRAMMZDI and the PCS, and lower scores on the SF-36. A higher BMI and lower scores on the SF-36MCS were significant predictors of lower scores on this test (R³=0.04). The results demonstrated that both tests were influenced differently. The B-S test seemed more influenced by physical factors and the abdominal endurance test were influenced by mental components. Why this difference exists is not clear, but this demonstrates again that in the interpretations of physical tests, psychosocial influences should be considered. Psychosocial influences are not equal for each physical test; therefore a complete psychosocial evaluation is needed. The overall aim of this doctoral dissertation was to contribute to the assessment of NS-CLBP, by improving the use of some instruments and tools. The results of these studies are not only interesting for the clinical practice, but are also useful in further research

Wearable sensor technologies applied for post-stroke rehabilitation

Stroke is a common cerebrovascular disease that is recognized as one of the leading causes of death and ongoing disability around the globe. Stroke can lead to losses of various body functions depending on the affected area of the brain and leave significant impacts to the victim’s daily life. Post-stroke rehabilitation plays an important role in improving the life quality of stroke survivors. Properly designed rehabilitation training programs can not only prevent further functional deterioration, but also helps patients gradually regain their body functionalities. However, the delivery of rehabilitation service can be a complex and labour intensive task. In conventional rehabilitation systems, the chart-based ordinal scales are considered the dominant tools for impairment assessment and the administration of the scales primarily relies on the doctor’s manual observation. Measuring instruments such as strain gauge and force platforms can sometimes be used to collect quantitative evidence for some of the body functions such as grip strength and balance. However, the evaluation of the patients’ impairment level using ordinal scales still depend on the human interpretation of the data which can be both subjective and inefficient. The preferred scale and evaluation standard also vary among institutions across different regions which make the comparison of data difficult and sometimes unreliable. Furthermore, the intensive manual supervision and support required in rehabilitation training session limits the accessibility of the service as the regular visit to qualified hospital can be onerous for many patients and the associated cost can impose an enormous financial burden on both the government and the households. The situation can be even more challenging in developing countries due to higher growing rate of stroke population and more limited medical resources. The works presented in this thesis are focused on exploring the possibilities of integrating wearable sensor and pattern recognition techniques to improve the efficiency and the effectiveness of post-stroke rehabilitation by addressing the abovementioned issues. The study was initiated by a comprehensive literature review on the latest motion tracking technologies and non-visual based Inertia Measurement Unit (IMU) had been selected as the most suitable candidate for motion sensing in unsupervised training environment due to its low-cost and easy-to-operate characteristics. Following the design and construction of the 6-axis IMU based Body Area Network (BAN), a series of stroke patient motion data collection experiments had been conducted in conjunction with the Jiaxing 2nd Hospital Rehabilitation Centre in Zhejiang province, China. The collected motion samples were then investigated using various signal processing algorithms and pattern recognition techniques to achieve the three major objectives: automatic impairment level classification for reducing human effort involved in regular clinical assessment, single-index based limb mobility evaluation for providing objective evidence to support unified body function assessment standards, and training motion classification for enabling home or community based rehabilitation training with reduced supervision. At last, the study has been further expanded by incorporating surface Electromyography (sEMG) signal sampled during rehabilitation exercises as an alternative input to enhance accurate impairment level classification. The outcome of the investigations demonstrate that the wearable technology can play an important role within a tele-rehabilitation system by providing objective, accurate and often realtime indications of the recovery process as well as the assistance for training management

Relationships between lumbar inter-vertebral kinematics and paraspinal myoelectric activity during sagittal flexion: a quantitative fluoroscopy and surface electromyography study

Introduction. Previous investigations that have attempted to relate mechanical parameters to NSLBP groups are often contradictory of each other, and currently clear mechanical markers for LBP remain elusive. In order to move forward in this area, it may be necessary to take a step back, and improve understanding of ‘normal’ spinal biomechanics (i.e. in low back pain free populations). Indeed, Peach et al. (1998) stated “By knowing what is “normal” and what is “abnormal” it may be possible to provide objective evaluation of rehabilitation protocols, and possibly classify different low back pathologies” (Peach et al. 1998). Therefore, an improved understanding of biomechanical behaviours in groups of back pain free people is desirable, particularly at an inter-vertebral level, an area where clear knowledge gaps still exist. Control of the spine during voluntary movement requires finely-tuned coordination of numerous trunk muscles. This dynamic control is believed to be achieved via communication between three sub-systems, the passive (vertebrae, discs and ligaments), the active (muscles and tendons) and the control (central and peripheral nervous system) systems. Investigating the interplay between these sub-systems however is difficult, as the spine is a complex structure with a hidden kinematic chain. Quantitative fluoroscopy (QF) is an imaging technology capable of measuring continuous spinal kinematics at the inter-vertebral level, and surface electromyography (sEMG) provides a non-invasive means of objectively quantifying muscle activity. This study used QF and sEMG technologies concurrently to investigate relationships between and amongst lumbar kinematic (QF determined) and muscle activity (sEMG determined) variables, during weight-bearing active forward flexion. This was the first time such technologies have been combined to investigate the biomechanics of the lumbar spine in vivo. An improved understanding of normal lumbar kinematic and myoelectric behaviour, will assist in the interpretation of what is abnormal in terms of inter-vertebral spinal mechanics. Methods. Contemporaneous lumbar sEMG and QF motion sequences were recorded during controlled active flexion of 60° in 20 males with no history of low back pain in the previous year. Electrodes were placed adjacent to the spinous processes of T9, L2 and L5 bilaterally, to record the myoelectric activity of the thoracic and lumbar erector spinae (TES and LES) and lumbar multifidus (LMU) respectively. QF was used concurrently to measure the maximum inter-vertebral rotation during flexion (IV-RoMmax) and initial attainment rate for the inter-vertebral levels between L2 and S1, as well as each participant’s lordotic angle. The sEMG amplitude data were expressed as a percentage of a sub-maximal voluntary contraction (sMVC). Ratios were calculated between the mean sEMG amplitudes of all three muscles examined. Each flexion cycle was also divided into five epochs, and the changes in mean sEMG amplitude between epochs were calculated. This was repeated to determine changes between all epochs for each muscle group. Relationships between IV-RoMmax and all other kinematic, morphological (i.e. lordosis) and muscle activity variables were determined using correlation coefficients, and simple linear regression was used to determine the effects of any significant relationships. The reliability and agreement of the IV-RoMmax, initial attainment rate, and normalised RMS sEMG measurements were also assessed. Results. The reliability and agreement of IV-RoMmax, initial attainment rate and sEMG amplitude measurements were high. There were significant correlations between the IV-RoMmax at specific levels and the IV-RoMmax at other lumbar motion segments (r = -0.64 to 0.65), lordosis (r = -0.52 to 0.54), initial attainment rate (-0.64 to 0.73), sEMG amplitude ratios (r = -0.53) and sEMG amplitude changes (r = -0.48 to 0.59). Simple linear regression analysis of all significant relationships showed that these variables predict between 18% and 42% of the variance in IV-RoMmax. Conclusion. The study found moderately strong relationships between kinematic, morphological and muscle activity amplitude variables and the IV-RoMmax of lumbar motion segments. The effects of individual parameters, when combined, may be important when such inter-vertebral levels are considered to be sources of pain generation or targets for therapy. This is an important consideration for future non-specific low back pain (NSLBP) research, as any attempts to associate these parameters with low back pain (LBP), should also now take in to account the normal biomechanical behaviour of an individual’s lumbar spine. Indeed, consideration should be given to the interactions that exists between such parameters, and they should not be considered in isolation. Multivariate investigations in larger samples are warranted to determine the relative independent contribution of these variables to the IV-RoMmax

Motor patterns evaluation of people with neuromuscular disorders for biomechanical risk management and job integration/reintegration

Neurological diseases are now the most common pathological condition and the leading cause of disability, progressively worsening the quality of life of those affected. Because of their high prevalence, they are also a social issue, burdening both the national health service and the working environment. It is therefore crucial to be able to characterize altered motor patterns in order to develop appropriate rehabilitation treatments with the primary goal of restoring patients' daily lives and optimizing their working abilities. In this thesis, I present a collection of published scientific articles I co-authored as well as two in progress in which we looked for appropriate indices for characterizing motor patterns of people with neuromuscular disorders that could be used to plan rehabilitation and job accommodation programs. We used instrumentation for motion analysis and wearable inertial sensors to compute kinematic, kinetic and electromyographic indices. These indices proved to be a useful tool for not only developing and validating a clinical and ergonomic rehabilitation pathway, but also for designing more ergonomic prosthetic and orthotic devices and controlling collaborative robots

座位中の圧力中心変化の動的時系列信号解析を通じたモチーフ認識による腰痛増悪の予測

Tohoku University永富良一課