**3.3. EMG electrode placement**

The application of EMG electrodes requires adequate know how of the skeletal muscles. The EMG electrode placement will be discussed in detail under this section.

In most cases, two detecting surfaces (or EMG electrodes) are placed on the skin in bipolar configuration [14, 15]. In order to acquire the best possible signal, the EMG electrode should be placed at a proper location and its orientation across the muscle is important. The surface EMG electrodes should be placed between the motor unit and the tendinous insertion of the muscle, along the longitudinal midline of the muscle [15]. The distance between the center of the electrodes or detecting surfaces should only be 1-2 cm. The longitudinal axis of the electrodes (which passes through both detecting surfaces) should be parallel to the length of the muscle fibers.

As mentioned previously, the EMG detecting surfaces should be placed in between the motor unit and the tendon insertion of the muscle. Detecting surfaces placed on the belly of the muscle has proved to be a more than acceptable location. Here, the target muscle fiber density is the highest [15]. Figure 9 shows the proper EMG electrode placement. When the electrodes are arranged in this way, the detecting surfaces intersect most of the same muscle fibers, and as a result, an improved superimposed signal is observed.

The electrodes should not be placed elsewhere. In the past, a misconception prevailed that the EMG detecting surfaces should be placed on the motor unit. But, as a matter of fact, the electrode location on the motor point serves as the worst location for signal detection [15]. Similarly, the electrodes should neither be placed at or near the tendon nor at the edge of the muscle. The muscle fibers become thinner and smaller in number when they approach the tendon of the muscle resulting in a weak EMG signal, proving the fact that electrode placement near the tendon is not feasible. If the electrode is placed at the edge of the muscle, the chances of crosstalk from other muscles will considerably increase, and the resultant signal will be disturbed by those of other muscles [15].

**Figure 9.** The ideal position of the electrode (two detecting surfaces) is between the innervation zone (or motor unit) and the tendinous insertion (or belly of the muscle) [15]
