*3.2.1. Skin preparation*

Preparation of the skin is essential to avoid artifacts and receive an appropriate signal. Before placing the electrodes on skin, it must be ensured that the skin is clean and dry. The skin must be cleaned by using gel, cream or alcohol and then it should be dried [61,62,25]. If necessary, shave excess body hair. Cleansing of the skin is useful to provide EMG recordings with low noise levels. Appropriate preparation of the skin assures the removal of body hair, oils and flaky skin layers and, consequently, reduces the impedance in the electrode-gel-skin interface. Shaving, wetting and rubbing with alcohol, acetone or ether, are often considered for the cleansing of the skin [25].

Proper skin preparation and electrode positioning are essential elements in acquiring EMG measurements of high quality. Two key strategies govern electrode preparations (1) electrode contact must be stable (2) skin impedance must be minimized. While there are no general rules for skin preparations, the type of application and signal quality sought usually determines the extent of the skin preparation [43]. For example, given a targeted test condition if the movement is somewhat static or slow moving and only qualitative reading are desired, a simple alcohol swab around the area of interest is sufficient [43]. However, if dynamic conditions present risk of the introduction of movement artifacts like in walking, running or other planned accelerated movements, a thorough preparation is required. Some EMG systems have built in impedance checking circuit that sends an imperceptible burst of current through the electrodes and controlled measurements are correlated to a known impedance level to indicate the quality of the electrode contacts [43].
