Lowering of sensory, motor, and pain-tolerance thresholds with burst duration using kilohertz-frequency alternating current electric stimulation.
OBJECTIVE
To determine the optimum burst duration for discrimination between sensory, motor, and pain-tolerance thresholds using 50-Hz bursts of kilohertz-frequency sinusoidal alternating current (AC) applied transcutaneously to human subjects.


METHODS
A repeated-measures randomized controlled trial.


METHODS
A research laboratory.


METHODS
Twenty-six healthy young adults.


METHODS
Bursts of AC electric stimulation at frequencies of 1 and 4kHz. Burst durations ranged from 250micros (for 1 cycle of 4kHz AC, ie, a single biphasic pulse) to 20ms (continuous AC).


METHODS
We measured sensory, motor, and pain-tolerance thresholds at frequencies of 1 and 4kHz.


RESULTS
We found that threshold voltages decreased to a minimum with increasing burst duration. The minimum threshold identified the "utilization time" over which summation of subthreshold stimuli occurs. Above the utilization time, thresholds increased. Estimated utilization times differed for sensory ( approximately 7ms), motor (>10ms), and pain-tolerance (>or=20ms). As a consequence, relative thresholds varied with burst duration. A maximum separation between sensory, motor, and pain-tolerance thresholds was found to occur with bursts in the range 1 to 4ms.


CONCLUSIONS
Short-duration kilohertz-frequency AC bursts might have a more useful role in rehabilitation than either pulsed current or the long duration bursts that characterize Russian and interferential currents. Further clinical studies are needed.
Department of Human Physiology and Anatomy, La Trobe University, Victoria, Australia. a.ward@latrobe.edu.au
Alex R
AR
Ward
Stacey
S
Lucas-Toumbourou
D000293:Adolescent; D000328:Adult; D004599:Electric Stimulation Therapy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D010146:Pain / Q000503:physiopathology / Q000534:rehabilitation*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology*; D012677:Sensation / Q000502:physiology*; D012678:Sensation Disorders / Q000503:physiopathology / Q000534:rehabilitation*; D016896:Treatment Outcome