COMPARISON OF sEMG SIGNAL OF CTS SUFFERERS AND NON CTS SUFFERERS

Md. Sarfaraz Alam 1 , Dr. Urmi Ravindra Salve 1 , Naresh Kumar 2 , Dr.Zulquernain Mallick 3 and Dr. Manoj Kumar 2 .  1. Department of Design, Indian Institute of Technology Guwahati,Guwahati, India. 2. Department of ME, Sant Longowal Institute of Engineering & Technology, Sangrur, Punjab, India. 3. Department of ME, Faculty of Engineering & Technology Jamia Millia Islamia, New Delhi, India. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

595 symptoms may only occur when the individual is doing the repetitive task -they will slowly go away when the person rests. Eventually, though, symptoms may be present all the time, if left untreated. The most common RSI signs and symptoms include: Tenderness in the affectedmuscle or joint, Pain in the affected muscleor joint, A throbbing (pulsating) sensationin the affected area, Pins and needles (tingling)in the affected area, especiallythe hand or arm, Loss of sensation in thehand, Loss of strength in the hand, Weakness, lack of endurance (Gagne et al., 2010).RSI is caused, by continuous repetitive and forceful work, hand or arm movements, i.e. hammering pushing, pulling, lifting or reaching movements, too fast or extreme workloads, long hours, lack of variety or breaks, awkward grips or positions, imperfectly designed equipment and/or poor working environments. Other synonyms for RSI include: Cumulative Trauma Disorder (CTD), Occupational Overuse Syndrome (OOS) and Repetitive Motion Syndrome (RMS).The more specific disorders are CTS, Tendonitis, and Tenosynovitis,Dupuytren's contracture,Epicondylitisor ‗tennis elbow',Bursitis and a host of others. Of course, CTS is the most common problem brought on by repetitive hand motion.

Experimentation:-
The study subjects were recruited from connecting rod manufacturing unit of a manufacturing industry. The population included all the unit workers irrespective of age, gender or ethnic group. All full-time workers with at least 6 months on the job were invited to participate in the study. Of the 113 eligible workers, 103 agreed to participate (91%) in the study. So a sample size of 103 workers was used (N = 103).

Surface electromyography:-
The terms carpal tunnel syndrome, cumulative trauma disorders, ergonomic disorders, repetitive strain injuries and repetitive motion injuries all refer to the same disorder of the wrist and hand (Kumar et al., 2010). CTS is brought on by over-worked, over-strained muscles of arms and hands, resulting in a loss of nerve conductivity and possibly leading to muscle strength problems (Montgomery, 1995). Human skeletal muscle consists of hundreds of individual cylindrically shaped cells (called fibers) bounded together by connective tissue. In the body, skeletal muscles are stimulated to approach motor nerves that carry signals in the form of nerve impulses from the brain. The combination of a single motor neuron and all of the muscle fibers it controls is called a motor unit. When an increase in the strength of a muscle's contraction is necessary to perform a task, the brain increases the number of active motor units within the muscle (Okada et al., 2000).
Although the electrical impulse generated and conducted by each fiber is very weak (less than 100 micro volts), many fibers conducting simultaneously induce voltage differences in the overlying skin that are large enough to be detected by surface electrodes. The detection, amplification and recording of changes in skin voltage produced by underlying skeletal muscle contraction are called electromyography. The recording thus obtained is called Electromyogram. The APB (Abductor PollicisBrevis) is a member of the thenar muscles and is often affected by muscle antropy associated with CTS (Wunderlich, 1993). EMG signal means a collective electrical signal from musculoskeletal system, skeletal muscles which represent the electrical activity of muscles during contraction. In recent years, there has been a tremendous interest in introducing intuitive interfaces that can recognize the user's body movements and translate them in to machine commands. The EMG signal is stochastic in nature and it becomes difficult to quantify and interpret the processed signal. Nerves and muscles create electrical signals that deliver messages to and from the brain. Injuries and diseases can affect nerves and muscles, which can slow down the movements of these electrical signals. The two tests that are done more often to measure the speed and degree of electrical activity in muscles and nerves are EMG and Nerve Conduction Study (NCS). NCS is often done along with EMG. In NCS electrodes are taped to the skin along the nerve pathway. Then the nerve is stimulated with electric current. The electrodes will record how fast the signal is travelling. This test helps to determine the specific site of the injury to the nerves.

Analysis based on EMG signal:-
Myoelectric signal represents the electrical activity of muscles and signal value is represented in micro volts obtained by surface electromyography (sEMG) technique. sEMG signals have been taken by BIOPAC MP-45 data acquisition unit. The MP unit is an electrically isolated data acquisition unit, designed for biophysical measurements. The MP45 receives power from the computer (USB port).The MP Unit has an internal microprocessor to control data acquisition and communication with the computer. The MP Unit takes incoming signals and converts them into digital signals that can be processed with the computer. There are analog input channels (two on MP45), one of which can be used as a trigger input.

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In the present study, workers have been examined by the BIOPAC MP45 instrument. To take readings from the muscles of a subject three electrodes are used. Positions of three electrodes during sEMG data collection are shown in the Figure 1 and Figure 2. The negative electrode (white) is placed on APB muscle and positive electrode (red) is placed 6 to 10 cm away from negative electrode. The third electrode (black) is grounded. An EMG reading of APB muscle of dominant hand is recorded for 3 minutes (180 sec.) for a series of clenching first as hard as possible, and then followed by release. For analysis, the sEMG signals readings are taken from 140 seconds to 160 seconds from each worker.From the EMG data the values of Raw-EMG, Integrated-EMG and Root-mean square EMG are obtained. Raw-EMG i.e. the unprocessed signal of amplitude between 0-6 mV is measured from peak to peak and represents the amount of muscle energy measured. Raw-EMG signal i.e. the signals which is unprocessed form of the sEMG signals helps mostly in qualitative analysis.Integrated-EMG is calculation of area under the rectified signal. Values are summed over the specified time then divided by the total number of values. Values will increase continuously over time. It quantifies the muscle activity means it tells about the movement of hand through the electrical signal by which one can identify how well the APB muscle is working. Root-mean square EMG (EMG-RMS) values are calculated by squaring each data point, summing the squares, dividing the sum of squares by number of observations, and taking the square root and it represent the quantification of muscle activity.
The abductorpollicisbrevis (APB) is a member of the thenar muscles and is often affected by muscle atrophy associated with carpal tunnel syndrome (CTS). The electrophysiological properties of the APB muscle are still not well understood. Reliable information about the physiological fatigue behavior of the APB muscle could be valuable to recognize changes in a pathologically altered muscle, as for instance in the case of CTS. However, to apply this information in a clinical setting it is essential to work with non-invasive diagnostic techniques whenever possible. Fortunately, considerable progress has been made in the past decades to develop non-invasive techniques to evaluate the performance of a muscle by recording and processing surface electromyograms (sEMG).
Based on literature it is clear that sEMG is a technique, which is used to check the performance of the APB muscle with the help of electrical signals. In this study, a comparison was done with the help of mean of sEMG signals between the CTS sufferers and non CTS sufferer workers in the manufacturing industry. The average root mean square values of the electromyogram signals were taken (Appendix 1).
The independent two samplet-test is used is used to check the statistical significance. The independent sample t-test is used because there are two separate samples of people which are to be compared. First sample is people who don't have CTS and second is who have CTS. There is no overlapping between the two samples.
The total number of workers is divided into two groups depending on the presence of CTS. Those who don't have CTS symptoms are assigned label ‗0' and those who have CTS symptoms are assigned label ‗1'. Group 1 (‗0' in the datasheet) has NO CTS. Group 2 (‗1' in the datasheet) has CTS.

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The hypothesis assumed in the analysis is as follows:  Null Hypothesis H 0 : Mean RMS sEMG value for Group1 = Mean RMS sEMG value for Group 2.  Alternative Hypothesis H A : Mean RMS sEMG value for Group1 ≠ Mean RMS sEMG value for Group 2.
In the analysis, CTS is grouping variable and sEMG value is test variable. The group statistics for CTS sufferers and non CTS sufferers is shown in the Table 1. It can be concluded from Table 1 that mean RMS sEMG value for non CTS sufferers is more than mean RMS sEMG value for CTS sufferers. Now, it has to be checked whether there is any significant difference between the two values. Final results for independent sample test are shown in the Table 2.

Result:-
From the result of F-test, it is clear that sig. (p-value) is found to be 0.08 which is less than 0.05. So the variances are not assumed to be equal and bottom row of the t-test will be used for analysis. As p-value (0.46) is less than 0.05, null hypothesis can be rejected and alternative hypothesis can be accepted.
Therefore it can be concluded that there is significant difference between the sEMG values of two groups of workers. Accepting alternative hypothesis means having CTS does affect the sEMG value of the workers. So Healthy workers have better sEMG signal and are less prone to carpal tunnel syndrome.

Conclusion:-
In the present analysis it has been demonstrated that the people with a particular occupations, can identify their problem of CTS, deciphered by sEMG signals analysis. Comparison of sEMGsignals (during expansion and contraction of APB muscle of different subjects) give indication of changes, not well understood so far. sEMG signals seem to have good repeatability but average validity in the analysis of some concrete relationships, due to lack of availability of standard data. So, this analysis it has been found thatindependent two sample t-test was used to analyze the sEMG signals of APB muscle which shows that non CTS sufferers have better sEMG signal than that of CTS sufferers and are more prone to potential CTS symptoms. Further there is scope of extending the work in different occupation, age groups, environmental conditions, and postures to analyze muscles conditions and identify the problems related to that.