What electrode size recruits more current under stimulation?

• A. Smaller
• B. Bigger
• C. Same size
• D. Very small

Answer: (B)

Electrode size shapes how the current travels through tissue. A bigger contact presents a larger surface area to the skin and underlying tissues, which lowers the impedance at the skin–electrode interface and allows more current to flow from the stimulator into the body. With the current able to pass more readily and the electric field spreading over a wider area, a larger electrode tends to recruit more tissue during stimulation. In contrast, smaller electrodes concentrate the current into a smaller area, increasing current density but activating a smaller region. So, when thinking about how much tissue is engaged under stimulation, a larger electrode will recruit more current.