132 research outputs found

    The effect of accelerometer location on the classification of single-site forearm mechanomyograms

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    <p>Abstract</p> <p>Background</p> <p>Recently, pattern recognition methods have been deployed in the classification of multiple activation states from mechanomyogram (MMG) signals for the purpose of controlling switching interfaces. Given the propagative properties of MMG signals, it has been suggested that MMG classification should be robust to changes in sensor placement. Nonetheless, this purported robustness remains speculative to date. This study sought to quantify the change in classification accuracy, if any, when a classifier trained with MMG signals from the muscle belly, is subsequently tested with MMG signals from a nearby location.</p> <p>Methods</p> <p>An arrangement of 5 accelerometers was attached to the flexor carpi radialis muscle of 12 able-bodied participants; a reference accelerometer was located over the muscle belly, two peripheral accelerometers were positioned along the muscle's transverse axis and two more were aligned to the muscle's longitudinal axis. Participants performed three classes of muscle activity: wrist flexion, wrist extension and semi-pronation. A collection of time, frequency and time-frequency features were considered and reduced by genetic feature selection. The classifier, trained using features from the reference accelerometer, was tested with signals from the longitudinally and transversally displaced accelerometers.</p> <p>Results</p> <p>Classification degradation due to accelerometer displacement was significant for all participants, and showed no consistent trend with the direction of displacement. Further, the displaced accelerometer signals showed task-dependent de-correlations with respect to the reference accelerometer.</p> <p>Conclusions</p> <p>These results indicate that MMG signal features vary with spatial location and that accelerometer displacements of only 1-2 cm cause sufficient feature drift to significantly diminish classification accuracy. This finding emphasizes the importance of consistent sensor placement between MMG classifier training and deployment for accurate control of switching interfaces.</p

    Reliability and measurement error of tensiomyography to assess mechanical muscle function: A systematic review

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    Interest in studying mechanical skeletal muscle function through tensiomyography (TMG) has increased in recent years. This systematic review aimed to (a) report the reliability and measurement error of all TMG parameters [i.e., maximum radial displacement of the muscle belly (Dm), contraction time (Tc), delay time (Td), half-relaxation time (1/2 Tr), and sustained contraction time (Ts)] and (b) to provide critical reflection on how to perform accurate and appropriate measurements for informing clinicians, exercise professionals, and researchers. A comprehensive literature search was performed of the Pubmed, Scopus, Science Direct and Cochrane databases up to July 2017. Eight studies were included in this systematic review. Meta-analysis could not be carried out due to the low quality of the evidence of some studies evaluated. Overall, the review of the nine studies involving 158 participants revealed high relative reliability [intra-class correlation (ICC)] for Dm (0.91-0.99); moderate to high ICC for Ts (0.80-0.96), Tc (0.70-0.98), and 1/2 Tr (0.77-0.93); and low to high ICC for Td (0.60-0.98), independently of the evaluated muscles. Additionally, absolute reliability [coefficient of variation (CV)] was low for all TMG parameters except for 1/2 Tr (CV = >20%) while measurement error indexes were high for this parameter. In conclusion, this study indicates that three of the TMG parameters (Dm, Td and Tc) are highly reliable, whereas 1/2 Tr demonstrate insufficient reliability, and thus should not be used in future studies

    Assessment of Skeletal Muscle Contractile Properties by Radial Displacement: The Case for Tensiomyography

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    Skeletal muscle operates as a near-constant volume system; as such muscle shortening during contraction is transversely linked to radial deformation. Therefore, to assess contractile properties of skeletal muscle, radial displacement can be evoked and measured. Mechanomyography measures muscle radial displacement and during the last 20 years, tensiomyography has become the most commonly used and widely reported technique among the various methodologies of mechanomyography. Tensiomyography has been demonstrated to reliably measure peak radial displacement during evoked muscle twitch, as well as muscle twitch speed. A number of parameters can be extracted from the tensiomyography displacement/time curve and the most commonly used and reliable appear to be peak radial displacement and contraction time. The latter has been described as a valid non-invasive means of characterising skeletal muscle, based on fibre-type composition. Over recent years, applications of tensiomyography measurement within sport and exercise have appeared, with applications relating to injury, recovery and performance. Within the present review, we evaluate the perceived strengths and weaknesses of tensiomyography with regard to its efficacy within applied sports medicine settings. We also highlight future tensiomyography areas that require further investigation. Therefore, the purpose of this review is to critically examine the existing evidence surrounding tensiomyography as a tool within the field of sports medicine

    RELATIONSHIP BETWEEN RUNNING ECONOMY AND MECHANICAL CHARACTERISTICS OF TRICEPS SURAE ASSESSED WITH TENSIOMYOGRAPHY: A PILOT STUDY

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    Tensiomyography (TMG) is a non-invasive technique commonly used for evaluating muscle properties in highly trained athletes. The aim of our study was to evaluate the mechanical characteristics of m. triceps surae in competitive runners through TMG measurement and analyze if there was a relationship with running economy (RE). Nine male runners completed the study (mean±SD: age 40.4±9.0 years, body height 176.2±4.9 cm, body mass 70.7±9.4 kg, 10-km time 39.8±5.9 min, VO2peak 56.9 ± 6.5 mL kg-1 min-1). Each subject visited the lab on two occasions with 72h of rest between the trials. On the first day, an incremental test was performed to determine their ventilatory thresholds and peak oxygen consumption. On the second day, RE was evaluated on a treadmill at the velocity of their first ventilatory threshold (VT1), and mechanical characteristics of the soleus and gastrocnemius muscles were analyzed with TMG. Significant differences were found between the economic and non-economic runners in m. soleus in delayed time (Td), contraction time (Tc), and maximal radial displacement of the muscle belly (Dm). Also, significant differences were found in contraction time (Tc) in medium calf (MC) and in half relaxation time (Tr) in lateral twin (LT). The main finding of our study was that the runners with better RE showed greater stiffness in the triceps surae muscles, an aspect that seems to be associated with better performance in athlete runners.Key words: running economy (RE), tensiomyography (TMG), m. triceps surae, m. gastrocnemius, m. soleus</p

    A Piezoresistive Sensor to Measure Muscle Contraction and Mechanomyography

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    Measurement of muscle contraction is mainly achieved through electromyography (EMG) and is an area of interest for many biomedical applications, including prosthesis control and human machine interface. However, EMG has some drawbacks, and there are also alternative methods for measuring muscle activity, such as by monitoring the mechanical variations that occur during contraction. In this study, a new, simple, non-invasive sensor based on a force-sensitive resistor (FSR) which is able to measure muscle contraction is presented. The sensor, applied on the skin through a rigid dome, senses the mechanical force exerted by the underlying contracting muscles. Although FSR creep causes output drift, it was found that appropriate FSR conditioning reduces the drift by fixing the voltage across the FSR and provides voltage output proportional to force. In addition to the larger contraction signal, the sensor was able to detect the mechanomyogram (MMG), i.e., the little vibrations which occur during muscle contraction. The frequency response of the FSR sensor was found to be large enough to correctly measure the MMG. Simultaneous recordings from flexor carpi ulnaris showed a high correlation (Pearson's r > 0.9) between the FSR output and the EMG linear envelope. Preliminary validation tests on healthy subjects showed the ability of the FSR sensor, used instead of the EMG, to proportionally control a hand prosthesis, achieving comparable performances

    Aplicación de la teoría generalizabilidad a un análisis de tensiomiografía en ciclistas profesionales de ruta

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    El objetivo del trabajo es determinar la fiabilidad y generalizabilidad de la estructura de datos procedentes de la evaluación, a través de tensiomiografía (TMG), de los parámetros tiempo de contracción muscular (TC) y máximo desplazamiento radial del vientre muscular (DM) de los músculos vastus medialis, vastus lateralis, rectus femoris y bíceps femoris de 10 ciclistas profesionales de fondo en carretera. Las mediciones de TMG tuvieron lugar durante el periodo preparatorio y el periodo competitivo. Se realizó un análisis de componentes de varianza por procedimiento de mínimos cuadrados y de máxima verosimilitud (<.0001), y un análisis de generalizabilidad. Los resultados indican que los valores de error del análisis de componentes de varianza por procedimiento de mínimos cuadrados y de máxima verosimilitud son idénticos para las variables TC y DM, lo que permite considerar la muestra como normal, lineal y homocedástica. El modelo de precisión de la variable TC presenta un adecuado nivel de fiabilidad y de generalizabilidad (e2 = 0.890 Φ = 0.831). El modelo con la variable DM presenta un adecuado nivel de fiabilidad y una generalizabilidad cercana a la adecuada (e2 = 0.826 Φ = 0.785). La optimización de la estructura de diseño con la variable TC consiguió unos excelentes niveles de fiabilidad (e2 = 0.939) y de generalizabilidad (Φ = 0.903), al igual que la variable DM (e2 = 0.922 Φ = 0.901). La importancia de este trabajo radica en la utilización de la TMG como técnica de intervención primaria en la prevención de lesiones musculares a través del cálculo de simetrías y su compensación con garantías de fiabilidad, precisión y validez.The aim of this study is to determine the reliability and generalizability of the data structure from the assessment, through tensiomyography (TMG), the parameters of muscle time contraction (TC) and maximum radial displacement of the muscle belly (DM) of the vastus medialis, vastus lateralis, rectus femoris and biceps femoris muscles of 10 professional road cyclists. TMG measurements took place during the preparatory period and the competitive period. An analysis of variance components by least-squares procedure and maximum likelihood (<.0001), and an analysis of generalizability was performed. The results indicate that the values of error of the variance components analysis by least-squares procedure and maximum likelihood are identical for TC and DM variables, which enables us to consider the sample as normal, linear and homoscedastic. The precision model of the TC variable shows a suitable level of reliability and generalizability (e2 = .89 F = .83). The model of DM variable shows a suitable level of reliability and a generalizability close to the proper one (e2 = .826 F = .785). The optimization of the design with the variable TC achieved excellent levels of reliability e2 = .94) and generalizability (F = .90), as well as the variable DM (e2 = .92 F = .90). The importance of this work lies in the use of TMG as a primary intervention technique in the prevention of muscle injuries through the calculation of symmetries and their compensation with guaranteed reliability, accuracy and validity

    The "Federica" hand: a simple, very efficient prothesis

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    Hand prostheses partially restore hand appearance and functionalities. Not everyone can afford expensive prostheses and many low-cost prostheses have been proposed. In particular, 3D printers have provided great opportunities by simplifying the manufacturing process and reducing costs. Generally, active prostheses use multiple motors for fingers movement and are controlled by electromyographic (EMG) signals. The "Federica" hand is a single motor prosthesis, equipped with an adaptive grasp and controlled by a force-myographic signal. The "Federica" hand is 3D printed and has an anthropomorphic morphology with five fingers, each consisting of three phalanges. The movement generated by a single servomotor is transmitted to the fingers by inextensible tendons that form a closed chain; practically, no springs are used for passive hand opening. A differential mechanical system simultaneously distributes the motor force in predefined portions on each finger, regardless of their actual positions. Proportional control of hand closure is achieved by measuring the contraction of residual limb muscles by means of a force sensor, replacing the EMG. The electrical current of the servomotor is monitored to provide the user with a sensory feedback of the grip force, through a small vibration motor. A simple Arduino board was adopted as processing unit. The differential mechanism guarantees an efficient transfer of mechanical energy from the motor to the fingers and a secure grasp of any object, regardless of its shape and deformability. The force sensor, being extremely thin, can be easily embedded into the prosthesis socket and positioned on both muscles and tendons; it offers some advantages over the EMG as it does not require any electrical contact or signal processing to extract information about the muscle contraction intensity. The grip speed is high enough to allow the user to grab objects on the fly: from the muscle trigger until to the complete hand closure, "Federica" takes about half a second. The cost of the device is about 100 US$. Preliminary tests carried out on a patient with transcarpal amputation, showed high performances in controlling the prosthesis, after a very rapid training session. The "Federica" hand turned out to be a lightweight, low-cost and extremely efficient prosthesis. The project is intended to be open-source: all the information needed to produce the prosthesis (e.g. CAD files, circuit schematics, software) can be downloaded from a public repository. Thus, allowing everyone to use the "Federica" hand and customize or improve it

    Neuromuscular Markers of High Performance Sport Preparation: Muscle Contractile Mechanics

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    Assessments of skeletal muscle functional capacity or bilateral muscular asymmetry often necessitate maximal contractile effort, which exacerbates muscle fatigue or injury. Tensiomyography (TMG) has been investigated in laboratory settings, as a means to assess muscle contractile function following fatigue; however observations have not been contextualised by concurrent physiological measures. TMG has more sparingly been applied in the field, with elite athletes. The aim of this thesis was to examine acute alterations and underlying variations in muscle contractile mechanics, through the application of TMG, contextualised with established physiological measures; and to apply TMG within high performance sports programmes. TMG successfully detected fatigue, evident from reduced strength, by displaying impaired muscle displacement, accompanied by elevated resting muscle tension. Greater asymmetry was detected in individuals with asymmetric strength; however, symmetry was masked during more complex tasks. Increased day-to-day variability was detected among highly trained athletes compared to recreationally active individuals. Acute training adaptations were detected, in contractile mechanics, in individual muscles. TMG could be useful in establishing fatigue status of skeletal muscle without exacerbating the functional decrements of the muscle, whilst also providing useful screening information for detecting asymmetry which may not be apparent during functional actions

    A Biomechanical and Physiological Signal Monitoring System for Four Degrees of Upper Limb Movement

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    A lack of adherence to prescribed physical therapy regimens in improper healing results in poor outcomes for those affected by musculoskeletal disorders (MSDs) of the upper limb. Societal and psychological barriers to proper adherence can be addressed through the system presented in this work consisting of the following components: an ambulatory biosignal acquisition sleeve, an electromyography (EMG) based motion repetition detection algorithm, and the design of a compatible capacitive EMG acquisition module. The biosignal acquisition sleeve was untethered, unobtrusive to motion, contained only modular components, and collected biomechanical and physiological sensor data to form full motion profiles of the following four degrees of freedom: elbow flexion—extension, forearm pronation—supination, wrist flexion—extension, and ulnar--radial deviation. The piloted sleeve simultaneously collected data from four inertial sensors, two electromyography (EMG) sensors and a flex-bend sensor. A visualization application was developed to present the information in a manner meaningful to the user. As well, an EMG based motion repetition detector was developed for use within the system. It was validated using an existing database of 23 subjects with varying musculoskeletal health, achieving a success rate of 95.43%. This algorithm was modified for use with the sleeve, resulting in a 95% success rate. An electrode and analog front end module was proposed, relying on unique material structures and low-noise, precision sensing techniques. The system prototype presented a resource-conscious tool for multi-modality tracking of elbow, forearm, and wrist motion, which could eventually be integrated into upper limb MSD rehabilitation
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