Assessment of common electrode placement methods for surface electromyography recordings of the triceps surae muscles

In surface electromyography, optimal electrode placement is critical. Various techniques are available for placing the electrodes appropriately, yet these are rarely assessed for accuracy, especially for electrode placement away from neighboring muscles considering the large variation in individual muscle morphology. This study evaluated triceps surae electrode placement using SENIAM recommendations and expert palpation, relative to anatomical muscle boundaries.

Electrodes were placed on the medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus of twenty-four participants following SENIAM guidelines and expert muscle palpation. Ultrasound was used to calculate the distances between electrodes and muscle boundaries at rest and during fixed-end plantar flexion at two intensities, in both plantar flexion and dorsiflexion positions.

SENIAM placed the electrodes laterally (electrode-boundary distance: 0.7 ± 0.9 cm) and the expert more centrally (distance to lateral boundary: 4.1 ± 0.9 cm; medial boundary: 3.0 ± 0.9 cm) on the LG. In four participants, SENIAM placements were positioned outside the LG muscle boundary. In soleus, SENIAM placements were close to the tibial border (0.7 ± 0.4 cm). For MG, both methods performed well.

This study highlights limitations of the SENIAM placement protocol for the LG and soleus, and supports the use of individualized approaches to improve electrode accuracy and enhance the validity of EMG recordings.