title: Comparative effect of positive and negative static magnetic fields on heart rate and blood pressure in healthy adults.
abstract: OBJECTIVE
  To compare changes in heart rate (HR) and blood pressure (BP) associated with short-term exposure to static magnetic fields (SMFs) of positive versus negative polarity.
  
  
  METHODS
  A double-blind, randomized controlled trial using a time series design.
  
  
  METHODS
  Physical therapy laboratory in a university setting.
  
  
  METHODS
  Seventy-five adults with a mean age of 30.6 years were assigned to one of three treatment groups. No subjects had any symptoms of cardiovascular disease or cardiac irregularity.
  
  
  METHODS
  Fifteen-minute exposure to an SMF by lying on a mattress pad containing magnets of positive polarity, negative polarity, or none (placebo).
  
  
  METHODS
  HR and BP were monitored prior to exposure, at 1-minute, 5-minute, 10-minute and 15-minute intervals following exposure, and again 5 minutes after exposure.
  
  
  RESULTS
  Subjects in all groups demonstrated slight decreases in HR and BP, but none of these changes were associated with the intervention (p = 0.170).
  
  
  CONCLUSIONS
  Short-term exposure to an SMF of either positive or negative polarity does not appear to cause any clinically meaningful changes in HR or BP among asymptomatic subjects. This finding supports the safe use of unipolar SMFs that contain low-intensity magnets (< 1000 gauss) relative to the cardiovascular system.
authors.affiliation: Department of Physical Therapy, School of Allied Health Sciences, University of Texas Medical Branch, Galveston 77555-1144, USA. mhinman@utmb.edu
authors.forename: Martha R
authors.initials: MR
authors.lastname: Hinman
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology / Q000528:radiation effects*; D002320:Cardiovascular Physiological Phenomena / Q000528:radiation effects; D004311:Double-Blind Method; D004574:Electromagnetic Fields; D005260:Female; D006339:Heart Rate / Q000502:physiology / Q000528:radiation effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology; D012016:Reference Values; D013997:Time Factors