Abstract
Electrograph is a device that is used to evaluate and record different patterns that result from a body’s skeletal muscle. The actual activity of utilizing the device is referred to as electromyography and the details reviewed from the result of the experiment known as electromyogram. The purpose of the electromyograph is to identify electrical impulses generated by the body muscles cells when they are put to task. Recording of the data obtained mostly helps in the medical field where the observations help in identifying body impairments, body responses and the biomechanics involved in the movement of a humans or animals body.
Introduction
Physique found in the human body by default generates electrical current even without them being in application to perform a task. This fact plays a vital role to the application of an electromyography since it is possible to measure the electrical impulses in the body through recording of current flow in muscles. Data records of the electrical current include those when the muscles are in application and when they are at rest. The distinction between the two periods of electrical current in the muscles helps in the identification of muscles point of weaknesses and a variety of other muscle problems (Herrel et al, 2012, p 261-271). Electrograph collaborates most of its findings by concentrating on the nerves that connect the muscles to the body.
Nerves are responsible for actions performed by body muscles by being primarily subjective to the direction that muscles react to in accordance to relayed instruction. If the nerves of the muscles get affected in any kind of way, muscles are inevitably affected by taking a response to the change in the stature of the nerves. This dictates that patient’s electromyogram following with a test of the body nerves this to show the frequency to which the nerves are sending impulses. With the obtained data, then the attending practitioner can identify the synopsis of the problem, its status with respect to its severity and counter a remedy to the problem (ROSENBAUM, 2009, p 64). The application of the device occurs in two ways one of which involves the insertion of electrodes into the skin of the patient referred to as invasive. The other method, which is in application in most medical institution at present, is non-invasive. The method is popular for its lack of the piercing factor as with the prior method where in this case electrodes are placed on the surface of the patient’s skin (DANION, F & LATASH, 2011, p 354). For an accurate measure of data collected in the factors such as the time of muscle retraction, distance of the electrodes from the muscles being tested, skin covering the muscle being tested, and the firmness of the electrode connected to the skin. The nature of the electrodes that are used in the implementation of electromyograph also play a vital role in determining the result of the test.
Electrodes used vary in reference to their size, their shape and the material used in their construction. The two classifications of electrodes in existence are the dry and the gelled electrode. Dry electrodes as the name suggests do not use gel due to the nature of their size while gelled electrodes use gel that is an electrolyte in nature. It is in use to present for an easier connectivity between the skin and the surface of the electrode that is in contact to the skin (LATASH, 2012, 299). The two electrodes vary in weight with the dry electrodes being heavier from the use of more electrical integrations such the presence of an amplifier. They present a further disadvantage In comparison to gelled electrodes since they produce more electrical noise. The continuous improvement in technology has ensured efficiency in the application of the device by making it possible to measure the electromyogram impulses at reduced levels of noise achieved by the application of differential amplification since the integrity of the signal basis a core of its authenticity to the quality o amplification.
Material and Technique
Five snaps electrodes from the BioRadio Lab Kit with assured fixation of their surfaces to the skin in the proper method guarantee quality results. Of the five electrodes, two of them need to be fixed an inch apart from the other both above the biceps and another two an inch apart on the wrist extensors located on the upper side of the forearm at the centre of the wrist and the elbow. The last electrode location is at a pivotal position that is the bony part of the elbow used as the reference point and the earth electrode (LATASH, 2012, 301). This illustration shows how the electrodes should be placed.
An important point to consider is that the electrodes need to be placed in direct contact to the skin in order to assure integral results. The electrodes need also be sanitized with alcohol as a precaution to reduce resistance that may occur from the presence of impurities between the contacts of the electrode to the skin. After the electrodes are connected correctly to the arm and are counter checked, then the snap leads are connected to their respective channels on the harness as shown in the diagram above (ROSENBAUM, 2009, p 67). The channels positioning is stackable hence one channel is placed over the other in that order.
The next step involves the running of the software ClevLabs activated from the button begin. When the EMG data tab is activated to show a dialogue of the EMG data on the screen, the patient places the arm in both an upward and downward position by moving his palm. To produce a counter argument, a person holds the subjects arm at the elbow and moves it in a way that counters the resistance. The difference in the bicep EMG is recorded with additional screen shots captured.
The next step involves the application of a robotic arm. When the robotic arm is activated the subject was required to relax their arm and consequently was asked to strain their bicep to the maximum. The filter parameters are adjusted in accordance to the result (Herrel et al, 2012, p 261-271). Data is saved as recorded and applied to formulate coinciding levels of the angle of the elbow. This is through the application of diverse filtering parameters as acquired in the activity. Reference of the data is then changed and new data is obtained in reference to the robotic arm and the way to control it.
Results
Figure 1: The figure illustrates on the effect of increasing the EMG signal on the wrist muscles. The result is taken when the subject is in the process of lengthening his wrist in presence while receiving opposition from another individual’s arm (the subject had his palms facing down when carrying his arm).
Figure 2: The diagram shows the climb exhibited by the EMG signal of the biceps muscle representing the black plot. Here, the subject is in the process of flexing the elbow in presence of resistance from a third party’s hands. (The subject had his palm facing up while carrying his arm)
Figure 3: The diagram illustrates the reaction of the EMG signal associated with flexing and extending elbow. The subject was in the process of moving his wrist to yield electrical activity associated with the extensor and flexor muscles in the wrist. There was turning on of high pass filter and high pass cutoff which were all set at 50 Hz. The filtering switch was also turned on.
Figure 4: The diagram illustrates the EMG effect related to the robotic arm. The robotic arm is moving together with the movement of the subject’s arm. There was choosing of the high pass filter mode with the cutoff set at 0.03 Hz to deliver viable results
Figure 5: The diagram illustrates the EMG effect of the robotic arm, which moves while the subject also moves his arm. In this step, the high pass cutoff was set at 0.63 Hz with the high pass filter being chosen.
Figure 6: The figure shows an EMG signal associated with quicker elbow flexing and extension movement. The subject was asked to move his wrist to generate electrical activity on the extensor and flexor muscles of the wrist. High pass filter was turned on and high pass cutoff was set at 50 Hz together with the filtering switch put on.
Figure 7: The figure shows an EMG signal associated with slow elbow flexing and extension movement. The subject was asked to move his wrist to generate electrical activity on the extensor and flexor muscles of the wrist. Low pass filter was turned on and low pass cutoff was set at 20 Hz together with the filtering switch put on.
Discussion
Figure 1 and 2 shows that the black signal activity had no effect on the red signal and vice versa with the activity of the red signal (Steeve & Moore, 2009, p 1530-155). This is because the black channel is on the flexor muscles when the red channel is in the process of gaining electrical activity of the extensor muscles. Figure 3 shows that the signal increased with the subject immediately flexing and extending his arms with the increase being at peak in the course of movement. This happened because the muscles are always at its highest contraction while in the middle of the movement (Woodford, 2008, P 5). In figures 4, 5 and 6 the difference in EMG signal is due to the different modes of filters used with the exhibition of diverse values of frequency (Steeve & Price, 2010, p 485-501). This shows that the setting of the low pass filter and the high pass filter have varying effects on the EMG signal movement. The frequencies of the high cutoff and low cutoff also have different effect on the signal exhibited by the EMG. Consequently, this shows that the combination of the different frequencies will be suitable for controlling the ball in question. There is need for selection of the best combination of the frequencies. The low pass filter can also be used in combination of high value of the cutoff and the same applies to the high pass filter in combination with the low value frequency of the latter. As shown in the EMG signal, it is true the low pass filter yields a even control indifferent to the high pass which yields lengthens the time for response (Steeve & Price, 2010, p 485-501). After the calculation of the RMS for the combination of high pass filter, low pass and band pass, the smallest resultant value is considered best for controlling the movement exhibited by the ball.
Answers to the discussion questions
The EMG signal yielded by the subject helps in manages the virtual arm of the robot. However, problem arises when there is need for normalizing the maximum and the minimum value within the range 0 to 1(Herrel et al, 2012, p 261-271). For instance, when the subject is tired the normalization value will change in the course of controlling the virtual arm thereby resulting in the decrease of the frequency while the amplitude will be increasing. Subsequently, the previous calculation will not be consistent to the results. Therefore, the subject should not be exposed to the system for a longer time in order to avoid fatigue.
Both high pass and low pass filters effects the process of generating EMG signals by the subject in controlling the virtual arm (Herrel et al, 2012, p 261-271). The low pass helps in eliminating the noise caused by the high frequency while the high pass helps in eliminating low frequency noise hence giving rise to smooth control and response time extension respectively.
EMG signals tends to fluctuate in its movements hence to correct this situation there is need for high pass filter set at 20Hz, which will only have influence on the appearance of data.
Although the activity of the hand is passive during the extension of the when the palm is facing downwards, the tendencies grasp is always weaker when compared to the normal personalities.
Bibliography
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