Which biofeedback instrument is commonly used for measuring muscle activity?

Electromyography (EMG) is specifically designed to measure muscle activity by detecting electrical signals generated by muscle fibers when they contract. This technology is particularly valuable in biofeedback applications, as it allows practitioners to assess and give feedback on muscle tension and relaxation in real-time.

EMG sensors are placed on the skin over the muscles of interest and they capture the electrical potentials that muscles produce. The data can then be used to help individuals learn how to control their muscle tension, which can be beneficial for managing stress, pain, or improving physical performance.

In contrast, other instruments listed serve different purposes: an electroencephalogram (EEG) measures brain wave activity, an electrocardiogram (ECG) tracks heart activity, and functional MRI (fMRI) assesses brain activity by detecting changes associated with blood flow. Each of these tools has its unique applications but none directly measures muscle activity in the way EMG does.