Where should I place my Electromyography (EMG) electrodes?

EMG signals are usually measured using a bipolar setup which means that two measuring electrodes with a positive (IN+) and a negative (IN-) lead are placed on the muscle of interest to measure the voltage imbalances with respect to a baseline. Therefore, another electrode is placed in a neutral area (Basmajian & Luca, 1985). With this bipolar setup, noise sources that occur only in the measuring and not in the reference electrode can be cancelled out by the second measuring electrode. Read more about “Why is my EMG signal so noisy?” and our BITalino Lab Guides (Home Guides).

Figure 1: Placement of EMG Electrodes on the Biceps (left) and reference on the elbow (right).

Figure 2: BITalino assembled EMG sensor connected to Biceps Brachii: muscle relaxation (left),muscle activation (rigth).

You can measure the EMG in the different muscle groups. In this article we’ll show some examples of the different muscles where you can place your sensor. We used a BITalino EMG Sensor (Assembled version) to show you the different positions.

Flexor carpi radialis (forearm)
The functionality of the flexor carpi radialis can be tested with EMG sensors for example for the purpose of rehabilitation. To measure muscular activity of the muscle flexor carpi radialis, the two measuring electrodes must be placed along the muscle fiber, see Figure 3 (left) and on the muscle belly . The placement of the assembled EMG sensor is illustrated in Figure 3 (right) in which the reference electrode is positioned on the elbow.

Figure 3: *EMG electrode positioning for flexor carpi radialis (left, marked in red) and positioning of the assembled EMG sensor plus reference electrode (right).*

Abductor pollicis brevis (thumb)
The next muscle we want to examine is the abductor pollicis brevis which is located at the thumb of the hand. It is a muscle to perform abduction of the thumb. The functionality of this muscle can be examined using EMG electrodes for example for rehabilitation purposes. The two measuring electrodes are positioned along the muscle fiber as illustrated in Figure 4.

*Figure 4: Electrode placement for the abductor pollicis brevis (left, marked in red)* and positioning of assembled EMG sensor plus reference electrode (right)

Trapezius Descendens (upper)
The upper muscle trapezius descendens is examined for clinical cases such as headaches, shoulder pain or strain injuries. For these purposes, the functionality of the muscle can be tested, or specific exercises performed with the help of the EMG signals. The general electrode placement for measuring muscular contractions of the upper trapezius are illustrated in Figure 5 (left) in which both measuring electrodes are positioned along the muscle fiber. The positioning of the assembled EMG sensor as well as the reference electrode are shown in Figure 5 (right).

*Figure 5: Electrode position for upper trapezius (marked in red) and assembled EMG sensor position with reference electrode (right).*

Zygomaticus major (happiness)
The functionality of the zygomaticus major can be tested with EMG sensors for example for rehabilitation of facial muscles or for psychophysiological studies. The electrode placement for this muscle is shown in Figure 4. Activating the muscle zygomaticus major can be performed by retracting and elevating the lips (e.g. smiling). The placement of the assembled EMG as well as the reference electrode are shown in Figure 6 (middle).