title: Penetration and spread of interferential current in cutaneous, subcutaneous and muscle tissues.
abstract: OBJECTIVE
  To investigate the penetration depth of interferential current (IFC) through soft tissue and the area over which it spreads during clinical application.
  
  
  METHODS
  A laboratory-based study of healthy participants.
  
  
  METHODS
  A university research laboratory.
  
  
  METHODS
  Twelve healthy subjects.
  
  
  METHODS
  Premodulated IFC at 90 Hz and 'true' IFC at frequencies of 4, 40 and 90 Hz were applied via four electrodes, in a quadrant setting, to the distal medial thigh of each participant on separate occasions.
  
  
  METHODS
  Voltage induced by tested currents was measured at three locations (middle of the four electrodes, in line with one circuit and outside the four electrodes) and three depths (skin, subcutaneous and muscle tissues) using three Teflon-coated needle electrodes connected to a Cambridge Electronic Design data acquisition system.
  
  
  RESULTS
  All voltages were greater at all depths and locations compared with baseline (P<0.001): premodulated IFC [mean difference 0.112, 95% confidence interval (CI) 0.065 to 0.160], 4 Hz (mean difference 0.168, 95% CI 0.106 to 0.229), 40 Hz (mean difference 0.165, 95% CI 0.107 to 0.223) and 90 Hz (mean difference 0.162, 95% CI 0.102 to 0.221). Voltages decreased with depth. Lower voltages of all currents were recorded in the middle of the four electrodes, with the highest voltage for 'true' IFC being recorded outside the four electrodes (mean difference 0.04, 95% CI 0.01 to 0.029; P=0.011). The premodulated IFC had the highest voltage in line with one circuit.
  
  
  CONCLUSIONS
  IFC passed through soft tissues, with the highest voltages recorded in superficial tissue and the lowest voltages recorded in muscle. For 'true' IFC, the current spread outside the electrodes at higher voltages compared with the intersection of the four electrodes. The premodulated IFC had the highest voltage in line with one circuit. In terms of higher recorded voltages, 'true' IFCs were more efficient than the premodulated IFC when targeting deeper tissues. However, further studies with larger samples are required to confirm the results of this study.
authors: Division of Physiotherapy, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors: Abulkhair
authors: A
authors: Beatti
authors: Anton
authors: A
authors: Rayner
authors: Lucy
authors: L
authors: Chipchase
authors: Tina
authors: T
authors: Souvlis
mesh_terms: D000328:Adult; D004599:Electric Stimulation Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D012879:Skin Physiological Phenomena; D013848:Thigh