title: Circulatory responses to voluntary and electrically induced muscle contractions in humans.
abstract: OBJECTIVE
  Transcutaneous electrical nerve stimulation (TENS) increases regional blood flow when applied at intensities sufficient to cause skeletal muscle contraction. It is not known whether increases in blood flow elicited by TENS differ from those caused by voluntary muscle contraction. The purpose of this study, therefore, was to compare the hemodynamic effects of these 2 types of muscle contraction.
  
  
  METHODS
  Fourteen people with no known pathology, aged 18 to 49 years (mean=28, SD=8), served as subjects. Calf blood flow (venous occlusion plethysmography), heart rate (electrocardiogram), blood pressure (automated sphygmomanometry), and force (footplate transducer) were measured during electrically induced and voluntary contractions.
  
  
  RESULTS
  Both modes of exercise caused rapid, but short-lived vasodilation (calf vascular resistance [mean(SEM]: (53%(3% for voluntary contractions versus (57%(4% for electrically induced contractions). The vasodilation caused by electrically induced contractions persisted for at least 15 seconds in the postexercise period, whereas the vasodilation elicited by voluntary contractions had resolved by this time point.
  
  
  CONCLUSIONS
  The hemodynamic changes elicited by voluntary and electrically induced muscle contractions are similar in magnitude but different in duration.
authors.affiliation: University of California-Berkeley, Berkeley, CA, USA.
authors.forename: B F
authors.initials: BF
authors.lastname: Miller
authors.forename: K G
authors.initials: KG
authors.lastname: Gruben
authors.forename: B J
authors.initials: BJ
authors.lastname: Morgan
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007866:Leg / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D012039:Regional Blood Flow; D013997:Time Factors; D004561:Transcutaneous Electric Nerve Stimulation