EMG Flash Lab

An EMG stands for Electromyogram. Electromyography is a technique for measuring the skeletal muscles response or electrical activity in response to a nerve's stimulation of the muscle which as a result produces an electromyogram. It can be used to assess along with diagnose the health of muscles and the nerve cells that control them (motor neurons). Furthermore, an EMG can reveal nerve dysfunction, muscle dysfunction, or problems with nerves communicating to muscles indicating signal transmission failures.

Below are graphs of EMG force signals that have been processed in MATLAB, on the left is EMGforce.txt and right is EMGforce2.txt. Looking at these graphs it appears that the EMG amplitude (mV) will show spikes for a short duration above zero likely when the subject contracts their muscle with stronger force than at rest. The magnitude of their strength will show a higher EMG amplitude as they put more force into the contraction of their muscles within the short amount of time. At the points of release, it can be seen the EMG amplitude is close to zero as their is no force placed on the EMG device implying no contraction of the muscles has occurred. Looking at the Force (%MVC) graph, it can be seen at the times when a quick force was applied by the muscles to the EMG device their is a very short pulse which curves upward and back down roughly in the shape of a palabra. The first subject appeared to apply force at 6 different times with increasing MVC % from one curve to the next, it appears to have lasted for roughly 3 second intervals. From 5 sec to 8 sec, from 10 sec to 13 sec, from 18 sec to 21 sec, from 26 sec to 31 sec, from 34 sec to 37 sec, from 42 sec to 46 sec. The second subject appeared to apply force at 5 different times with increasing MVC % from one curve to the next, it appears to have lasted for 3 second intervals. From 2 sec to 5 sec, from 6 sec to 9 sec, from 11 sec to 14 sec, from 16 sec to 20 sec, from 22 sec to 26 sec. The two EMG force subjects data appear to be almost identical with the only difference being the number of force applications and the duration in which time samples were collected. Subject 1 was 45 seconds and subject 2 was 30 seconds. The Force MVC % was strongest between the 4th interval which is between 40 to 45 seconds for subject 1 and between 22 to 26 seconds for subject 2. The force EMC increases for both subject from 20 % to 100% in 20% increases from one force interval to the next for subject 1 with 100% force being recorded twice and for subject 2 it goes from 20% to 55%, to 70%, to 90%, to 100%., one recording for each. Both amplitude mV have the highest peak seen at 2 mV and as spikes are seen for a short duration in the graph it can be observed the the amplitude peaks higher and higher in mV until the threshold of 2 mV is reached on the graph for the maximum MVC % force exerted.

Below are graphs of EMG squeeze force signals that have been processed in MATLAB, on the left is EM_EMG_SQUUEZE1.txt and right is EM_EMG_SQUUEZE2.txt. Looking at these graphs it appears that the EMG amplitude (mV) will show spikes for a short plateau duration above zero likely when the subject contracts their muscle with stronger controlled squeezing force than at rest. The magnitude of their strength will show a higher EMG amplitude as they put more force into the contraction of their muscles within the short amount of time. At the points of release, it can be seen the EMG amplitude is close to zero as their is no force placed on the EMG device implying no contraction of the muscles has occurred and the squeezing has stopped. Looking at the Force (%MVC) graph, it can be seen at the times when a short squeezing force was applied by the muscles to the EMG device their is a very short pulse which curves upward and plateau's at a consistent force MVC % and back down roughly in the shape of a small plateau. The level of the plateau depends how strong the force was when they squeezed to increase the force MVC %. The first subject appeared to apply force at 5 different times with increasing MVC % from one curve to the next, it appears to have lasted for 5 second intervals. From 2 sec to 6 sec, from 8 sec to 12 sec, from 15 sec to 19 sec, from 22 sec to 26 sec, from 30 sec to 35 sec. The second subject appeared to apply force at 5 different times with increasing MVC % from one curve to the next, it appears to have lasted for 5 second intervals. From 2 sec to 6 sec, from 8 sec to 12 sec, from 18 sec to 22 sec, from 26 sec to 32 sec, from 35 sec to 40 sec. The two EMG squeeze force subjects data appear to be almost identical with the only difference being the the duration in which time samples were collected. Subject 1 was 35 seconds and subject 2 was 40 seconds. The Force MVC % was strongest between the 4th interval which is between 30 to 35 seconds for subject 1 and between 35 to 40 seconds for subject 2. The force EMC increases for both subject from 20% to 30% to 35% to 45% to 100% for subject 1 and for subject 2 it goes from 20% to 35% to 50% to 65%, to 70% to 100% with one recording for each. Both amplitude mV have the highest peak seen at 1.5 mV and as spikes are seen for a short duration in the graph it can be observed the the amplitude peaks higher and higher in mV until the threshold of 1.5 mV is reached on the graph for the maximum MVC % force exerted. Comparing these results to the EMG force graphs above, it appears that they differ in the shape of their curvature of force MVC % time. The squeeze results show plateau's of force as the user squeezes for a short equal amount of force period of time while the force results show a short and quick spike of maximum peak force reached within the short force MVC % curvature duration. The max EMG amplitude mV is 2 mV for the force and only 1.5 mV for the squeeze force.

Below are graphs of EMG signals from a dog that have been processed in MATLAB, figure 1 is the original EMG displaying the microvolts observed over the 5 second time period. Figure 2 is the envelope of EMG obtained using a full-wave rectifier and a modified Bessel filter as the Filtered EMF envelope is measured over the 5 second time period. Figure 3 is the inspiratory airflow measured with a pneumo-tachograph, in liters/second where the airflow is measured in liters/second over the 5 second time period. Figure 4 is a plot with all the signal graphs from figures 1-3 observed; moreover, the top one is the EMG, the second is the Env graph, and the third is the Flow graph. Looking at the first graph their appears to be two spike duration in the mV data, one which is between 1 to 2 seconds and another between 3.5 to 4.5 seconds during the entire 5 second recording interval. The signal is then filtered using a modified Bessel filter in the second graph which shows the data starting at -4 filtered EMG envelope and during the time spike durations it rises to -1; moreover, the signal is a more clear curve with small curves for roughly .25 increases before, between, and after the two larger palabra looking spikes were observed. for the same 5 second time duration In the third graph, it shows the data starting at 0 and increasing to 0.7 liters/second of air flow during the time spike durations; moreover, the signal is a clear smooth curve with only two palabra looking increases in the data. The final graph shows all of the signal graphs together and the data looks to line up in terms of the time points of the spikes observed and the amplitude of the peaks despite being unit less, they share the same level. The data is showing that the dog is breathing twice within 5 seconds for a one second time period and this can be observed via the EMG recording which shows the strength of the muscle contraction and by looking at the amount of air flow into the dog which appears to be equal in power despite different units.