Electrical somatosensory and motor thresholds across pulse duration: characterizing strength-duration properties and nerve excitability.

Abstract Quantitative assessment of peripheral sensorimotor function via surface electrical stimulation provides essential insights into neural responses; however, standardized stimulation parameters remain poorly defined. This study aimed to characterize the strength-duration (S-D) relationship of electrical sensory, motor, and pain thresholds (EST, EMT, and EPT) across a wide range of pulse durations to identify physiological stabilization plateaus and determine the pulse durations that maximize the discrimination between threshold types. Thirty healthy volunteers underwent electrical threshold testing (ETT) on the forearm using a symmetrical biphasic current (100 Hz). Eleven randomized pulse durations (0.02–0.65 ms) were evaluated. S‑D was analysed following Weiss’s model, and discriminative capacity was assessed using effect-size analysis. All thresholds exhibited the characteristic hyperbolic decay of the S‑D curve, although stabilization dynamics could not be determined within the pulse duration range evaluated. Thresholds were well fitted by Weiss’s linear model (R 2 > 0.902), and the estimated rheobase resulted ∼0.7 mA for EST, ∼2 mA for EMT, and ∼3.7 mA for EPT. The corresponding chronaxie values were 1.09 ms for EST, 0.57 ms for EMT, and 0.41 ms for EPT. Extreme pulse durations (0.02 and 0.65 ms) demonstrated the highest discriminative capacity between thresholds (η 2 p = 0.936 and 0.921), although all pulse durations obtained large effect sizes (η 2 p > 0.869). These findings demonstrate that electrical thresholds follow a predictable neurophysiological pattern across pulse durations and suggest that pulse duration selection may be important for achieving target threshold responses, providing a reference framework for standardizing ETT protocols in both research and clinical diagnosis.