15 research outputs found

    Estudio de modelos propuestos para el nervio mediano sano y con síndrome de túnel carpiano : Study of proposed models for the healthy median nerve and with carpal tunnel syndrome

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    En este documento se muestra de forma detallada la revisión de modelos teóricos  para el nervio mediano, observando el estado de un nervio con mielina y  sin mielina, con las variables que cada autor genera para profundizar en los análisis que exponen, para de esta forma entrar a detallar los parámetros más relevantes que se observan en la literatura con las causas probables de la generación del síndrome del túnel carpiano en la sociedad laboral, de igual forma se muestra de forma resumida la parte anatómica que recorre el nervio mediano, para finalmente concluir que los parámetros de mayor relevancia son la frecuencia por los efectos capacitivos, la intensidad de corriente, la duración, latencia y velocidad de conducción. Trabajo realizado en el grupo de investigación LIDER de la Universidad Distrital Francisco José de Caldas. &nbsp

    Tendon transfers to restore opposition of the thumb

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    In man and some of the apes, the thumb has the function of a contrafinger. This function is made possible by a great freedom of movement of the first metacarpal and a highly developed and differentiated thumb musculature. The grasp function of the hand is dependent on the oppositional capacity and adductive power of the thumb, and is severely limited by a paralysis or dysfunction of the intrinsic thumb muscles. Whereas loss of the function of the adductor pollicis can be partially compensated for by the adductive action of the extensor pollicis longus, in paralysis or dysfunction of the radial thenar muscles compensation can only be provided by surgery. Since 1918, many methods of tendon transfer have been described for the restoration of thumb opposition, all of which bring about an improvement of the grasp function, albeit to different degrees. These methods vary in the selection of the motor, the direction of pull of the tendon, the use of a fulcrum, and the mode of insertion. The highly effective method of Bunnell (1938) is often used as the standard procedure. With this method, the flexor superficialis tendon of the ring finger is looped around the tendon of the flexor carpi ulnaris and passed subcutaneously across the thenar eminence, after which it is fixed on the thumb at the level of the metacarpo-phalangeal joint. In the reconstruction of the thumb opposition, however, a standard procedure often cannot be applied, because the muscle-tendon unit usually used for this purpose has been damaged or because the transfer route is blocked by scar tissue

    A multi finger electromagnetic actuator apparatus for biomechanical studies on the hand

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    Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (leaves 77-80).The focus of this thesis was on the design and construction of a multi-finger haptic device powered by electromechanical voice-coil actuators. Five actuators were designed and constructed and a position and force feedback control system was implemented for each. The maximum continuous force output for each actuator ranged from 12-16 N, which is about 15%-30% of the maximum force that can be exerted by an individual finger. The bandwidth of the controlled actuators ranged from 0.7 Hz to 1.7 Hz, the steady-state error was zero, and the overshoot ranged from 3.5% to 7.7%. Four actuators were constructed into an array, with finger contact points 23 mm apart. Additional structures, such as finger holders and a wrist rest, were developed to complete the human interface. With further modifications, the multi-finger apparatus can be used to conduct biomechanical and perceptual studies of the human hand.by Kathleen L. DobsonS.M

    Evaluating footwear “in the wild”: Examining wrap and lace trail shoe closures during trail running

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    Trail running participation has grown over the last two decades. As a result, there have been an increasing number of studies examining the sport. Despite these increases, there is a lack of understanding regarding the effects of footwear on trail running biomechanics in ecologically valid conditions. The purpose of our study was to evaluate how a Wrap vs. Lace closure (on the same shoe) impacts running biomechanics on a trail. Thirty subjects ran a trail loop in each shoe while wearing a global positioning system (GPS) watch, heart rate monitor, inertial measurement units (IMUs), and plantar pressure insoles. The Wrap closure reduced peak foot eversion velocity (measured via IMU), which has been associated with fit. The Wrap closure also increased heel contact area, which is also associated with fit. This increase may be associated with the subjective preference for the Wrap. Lastly, runners had a small but significant increase in running speed in the Wrap shoe with no differences in heart rate nor subjective exertion. In total, the Wrap closure fit better than the Lace closure on a variety of terrain. This study demonstrates the feasibility of detecting meaningful biomechanical differences between footwear features in the wild using statistical tools and study design. Evaluating footwear in ecologically valid environments often creates additional variance in the data. This variance should not be treated as noise; instead, it is critical to capture this additional variance and challenges of ecologically valid terrain if we hope to use biomechanics to impact the development of new products

    Estimation of load sharing among muscles acting on the same joint and Applications of surface electromyography

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    The force produced by a specific muscle cannot be measured and what is measured is the total force provided by all the active muscles acting on a joint, including agonists and antagonists. The first part of this work (chapter 3) addresses the issue of load sharing by proposing two possible approaches and testing them. The second part (chapter 4 and 5) addresses two applications of surface EMG focusing on the study of a) muscle relaxation associated to Yoga sessions and b) the activation of muscle of the back and shoulder of musicians playing string instruments (violin, viola and cello). In both parts the element of innovation is the use of two dimensional electrode arrays and of techniques based on EMG Imaging. The objectives of this work are presented and explained in chapter 1 while the basic concepts of surface EMG are summarized in chapter 2. Different EMG-based muscle force models found in the literature are explained and discussed. Two renowned amplitude indicators in surface EMG (sEMG) studies are the average rectified value (ARV) and the root mean square (RMS). These two amplitude indicators are computed over a defined time window of the recorded signals to represent the muscle activity. The advantages and disadvantages of RMS and ARV are compared and discussed for a simple sinusoid as well as for more complex signals (simulated motor unit action potential detected by high density electrode grid). The results show that RMS is more robust to the sampling frequency than ARV. In this thesis, starting from the simulation of a single fiber and of a group of fibers (motor unit), it is shown that inter electrode distance (IED) greater than10 mm causes aliasing. Aliasing is a source of error in sEMG map interpretation or decisions that are made by automatic algorithms such as those providing image segmentation for the identifications of regions of interest. Chapter 2 discusses three segmentation algorithms (K-means, h-dome, watershed) and compares them in order to find the most suitable method. Results reveal that among the three mentioned algorithms, watershed provides most accurate segmentation for the simulated ARV maps. Chapter 3 presents a mathematical model that is associated to the monotonic Force-EMG relation. A possible non-linear relationship between the EMG and force or torque is presented. A system of "M" equations is obtained by performing "M" measurements at "M" different force levels in isometric conditions. The solutions of such system of equations are the values for each muscles. Two different approaches were investigated for finding the solutions of the system, which are: a) Analytical-Graphical Approach (AGA) and b) Numerical Approach (NA) consisting of error minimization (between the total estimated and measured force) applying optimization algorithms. The AGA was used to find the model parameters of each muscle contributing to the force production on a joint by finding the intersection of those surfaces that can be obtained from sequential substitutions of the model parameters in the equations corresponding to each contraction level. In simulation studies, the AGA graphically shows that there is more than one solution to the load sharing problem even for the simplest theoretical case (i.e. a joint spanned by only two muscles). The second approach, based on minimization of the mean square error between the measured and the total estimated force or torque (with "N" muscles involved) provides an estimate of the model parameters that in turn provides the force contributions of the individual muscles. The optimization algorithms can find the solutions of our system made of non-linear equations (see chapter 3). Starting from different point (initial conditions), different solutions can be found, as predicted by the AGA approach for the two-muscle case. The main conclusion of this study is that the load sharing strategy is not unique. Chapter 4 discusses the application of surface electromyography to a single case study of Yoga relaxation to show the feasibility of measurements. The effect of yoga relaxation on muscle activity (sEMG amplitude), as well as on mean and median frequencies and muscle fiber's conduction Velocity, is discussed in this chapter. No changes in the sEMG activity pattern distribution were found for the same task performed before and after applying yoga relaxation technique. However, myoelectric manifestations of fatigue were smaller after relaxation and returned to the normal pattern after the recovery phase from relaxation. Further studies are justified. Chapter 5 describes results and discusses the spatial distribution of muscle activity over the Trapezius and Erector Spinae muscles of musicians playing string instruments. In chapter 5, the effect of backrest support in sitting position during playing cello, viola, and violin on the muscle activity index of upper and lower Trapezius muscle of the bowing arm, upper Trapezius muscle of non-bowing arm, left and right Erector Spinae muscles is investigated. Two professional players (one cello and one viola) and five student players (one cello, three violin and one viola) participated in this study. The muscle activity index (MAI) was defined as the spatial average of RMS values of the muscle active region detected by watershed segmentation for Trapezius muscles (left and right), and thresholding technique (70% of the maximum value) for left and right Erector Spinae muscles. It was found that the MAI is string (note) dependent. Statistical difference (p < 0:05) between the MAIs of left Erector Spinae muscle during playing with and without backrest support was observed in four (out of five) student players. No statistical differences were observed on the muscle activity of Trapezius (bowing and no-bowing arms) during playing with and without backrest support in different types of bowing for all musicians. In conclusion, this work addresses a) the issue of spatial sampling and segmentation of sEMG using 2D electrode arrays, b) two possible approaches to the load-sharing issue, c) a single-case study of Yoga relaxation and d) the distribution of muscle activity above the Trapezius and Erector Spinae muscles of musicians playing string instruments. Previously unavailable knowledge has been achieved in all these four studies
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