Background and Research

Research:

• muscle tissue at rest is normally electrically inactive or electrically silent
• skin needs to be rubbed clean, preferably with alcohol pads
• removes oil, sweat, dead skin - improves readings
• when the muscle is voluntarily contracted, action potentials begin to appear
• increasing strength of contraction, increase of action potentials
• spontaneous spikes (action potentials) during contractions
• full contraction will cause rapid firing
• Reference point needed 

Research Article Links: 

https://www.dropbox.com/l/SvHR2fEnilbxEA16Onw69c 

https://www.dropbox.com/s/zlq2g1i7llfe7hz/J%20Neurol%20Neurosurg%20Psychiatry-1975-Hallett-1154-62.pdf 

Artifacts: 

• Line Interference: the most common artifact, produced by 50/60 Hz noise from the power line and is transmitted by electrical devices near the data acquisition device. This can be removed by applying a filter to the signal. It is possible that some filters will not be able to filter out signals from the radio transmitting devices or other electronic devices. 
• EKG/ECG Artifacts: Electrical signals from the heart can be very difficult to filter, but the placement of the sensors are key because avoiding the areas that are not aligned with the axis of the heart activity is imperative and should be placed on the same side of the body to reduce these signals. 
• DC offset artifacts: Created between the skin and the electrodes but can be avoided with proper preparation of the skin. 
• Muscle crosstalk: when using more than one muscle, the signals form other muscles being monitered interfer with the desired muscle activity. However, this is avoided by choosing the appropriate inter-electrode distance (around 2 centimeters) and by placing electrodes at the middle of the muscle belly. Furthermore, this project will only focus on one muscle. 
• Movement artifacts: During patient movements, the electrodes can be moved or the cables could be pulled, which creates an artificial small signal. This can be avoided by using tape or an elastic band to fasten the cable 

Link of general EMG information, artifacts, and how to avoid them: http://www.thoughttechnology.com/pdf/manuals/MAR900-01%20SEMG%20applied%20to%20psychophysiology.pdf

Placement of EMG link:

http://gasstationwithoutpumps.wordpress.com/2012/07/14/emg-and-ekg-works/