Which technique is considered invasive due to the necessity of inserting wires into muscle fibers?

Intramuscular EMG is considered invasive because it involves the insertion of fine wires or needles directly into muscle fibers to record electrical activity. This method allows for a more accurate and detailed measurement of muscle activation patterns, as it can capture signals from specific muscles at a higher resolution than non-invasive techniques. The direct placement of electrodes into the muscle is what makes this procedure invasive, requiring precautions to minimize discomfort and complications.

In contrast, surface EMG utilizes electrodes placed on the skin's surface, making it a non-invasive technique to measure muscle activity. Electropalatography (EPG) employs an artificial palate with electrodes to provide real-time information about tongue placement during speech without penetrating the body, and functional MRI is a non-invasive imaging method that measures brain activity through blood flow changes.