Sensory and motor nerve conduction velocities following therapeutic ultrasound.

Nineteen healthy volunteers each received six, five-minute ultrasound treatments at sonation intensities of 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 W/cm(2), applied along the proximal forearm segment of the ulnar nerve, over an area of approximately 4.5 times the area of the ultasound application head. Sensory and motor nerve conduction velocities responded similarly, but not identically to ultrasound. All clinical intensities, with the exception of 0.5 W/cm(2) (p <0.10), were associated with significantly increased velocities. Subcutaneous tissue temperatures were directly related to sonation intensity, although significantly increased temperatures were not observed until 1.5 W/cm(2) intensity was used. The effectiveness of clinical applications of ultrasound in pain relief cannot be attributed to a decrease in nerve conduction velocity of the faster conducting A-fibers, which are evaluated using standard nerve conduction techniques.