Optimization of pulse duration and pulse charge during transcutaneous electrical nerve stimulation.

The main effects and interaction of pulse duration and pulse charge on sensory, motor and painful stimulation were examined on six male subjects. Surface electrodes were placed over the triceps brachii muscle. Pulse duration was varied between 5 and 1000 µs. Peak current, muscle torque and four excitatory responses were determined. Sequential order of sensory, motor and painful stimulation was evidenced. Selective excitation of these different physiological responses was easier and required less charge as pulse duration became shorter. The greatest non-painful torque was reached at 100 µs pulse duration. The most suitable range for motor stimulation was 20 to 200 µs. For painful stimulation, a 5 to 10 µs duration was favoured. A range of 20 to 100 µs was recommended for sensory stimulation.