title: The biophysical effects of ultrasound on median nerve distal latencies.
abstract: OBJECTIVE
  Previous studies have documented the lack of ultrasound's non-thermal effects on nerve conduction using frequencies of 1 MHz and 870 kHz. The analyses and conclusions were reached, despite only one study incorporating pulsed ultrasound. The purpose of this study was to determine the biophysical effects of continuous wave (CW) and pulsed wave (PW) ultrasound on median nerve motor and sensory latencies using common frequencies of 1.0 and 3.0 MHz.
  
  
  METHODS
  Fifteen healthy subjects (8 males, 7 females, age = 23.5 + 4.44 yrs, height = 171.2 + 10.7 cm, weight = 67.5 + 7.9 kg) without a history of neurological or musculoskeletal injury to their non-dominant arm volunteered for testing.
  
  
  METHODS
  Subjects were exposed in counterbalanced order to five ultrasound treatment conditions: (1) 1 MHz, 1.0 W/cm2, 8 min., (2) 1 MHz, 1.0 W/cm2, 50% PW, 8 min., (3) 3.0 MHz, 1.0 W/cm2, CW, 8 min., (4) 3.0 MHz, 1.0 W/cm2, 50% PW, 8 min., (5) placebo, 0.0 W/cm2, 8 min. Dependent measures for motor and sensory latencies, and subcutaneous temperatures were taken pretreatment, at 2, 4 and 6 minutes during treatment, and immediately post-treatment. Separate two within repeated measures ANOVA were used for each dependent measure.
  
  
  RESULTS
  Analysis revealed significant interactions for motor latencies [F (16,224) = 52.77, p < .001], sensory latencies [F (16,224) = 41.10, p < .001], and subcutaneous temperatures [F (16,224) = 52.77, p < .001]. Tukey's HSD post hoc analyses confirmed that nerve latencies responded similarly to subcutaneous temperature changes during and after ultrasound treatment.
  
  
  CONCLUSIONS
  Alterations in nerve latencies from ultrasound on healthy nerves appeared to be related to temperature changes induced by ultrasound's thermal effects, and not by non-thermal or mechanical effects.
authors.affiliation: University of Virginia, Charlottesville, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Moore
authors.forename: J H
authors.initials: JH
authors.lastname: Gieck
authors.forename: E N
authors.initials: EN
authors.lastname: Saliba
authors.forename: D H
authors.initials: DH
authors.lastname: Perrin
authors.forename: D W
authors.initials: DW
authors.lastname: Ball
authors.forename: F C
authors.initials: FC
authors.lastname: McCue
mesh_terms: D000328:Adult; D055592:Biophysical Phenomena; D001703:Biophysics; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology; D009431:Neural Conduction / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D011984:Sensory Receptor Cells / Q000502:physiology; D012881:Skin Temperature / Q000502:physiology; D014464:Ultrasonic Therapy