In EMG (electromyography) setups, the negative electrode is typically referred to as the "reference" or "ground" electrode.
The reference electrode in EMG is essential for reducing noise and ensuring accurate readings. It is usually placed on a bony prominence away from the muscle being tested, such as the elbow or the shoulder for upper limb muscles, or the knee for lower limb muscles. The choice of placement helps create a stable baseline for the electrical signals from the muscle of interest.
For upper limb EMG, common reference electrode placements include the lateral epicondyle for forearm muscles and the acromion process for shoulder muscles. For lower limb EMG, the tibial tuberosity or the lateral malleolus are often used. The reference electrode should always be placed on a site that minimizes interference from nearby muscles.