title: Cardiac autonomic modulation during recovery from acute endurance versus resistance exercise.
abstract: BACKGROUND
  The kinetics of parasympathetic reactivation after dynamic endurance exercise have been well elucidated. However, autonomic recovery of cardiac function after resistance exercise is not known.
  
  
  OBJECTIVE
  The purpose of this study was to assess cardiac autonomic modulations during recovery from acute resistance exercise versus acute endurance exercise.
  
  
  METHODS
  Electrocardiogram readings were collected before and 30 min after a single bout of endurance or resistance exercise in 14 male participants (aged 25.3+/-2.5 years). Heart rate (HR) variability was spectrally decomposed using an autoregressive approach. High frequency (HF) power was considered representative of vagal modulation. All values were expressed in both absolute and normalized units (normalized for change in total power).
  
  
  RESULTS
  A mode-by-time interaction (P<0.05) was detected for HR, which remained elevated to a greater extent after resistance exercise. Total power was significantly reduced after resistance exercise (P<0.05) but not endurance exercise. An interaction (P<0.05) was also detected for both a change in absolute natural log function HF power and natural log function low frequency (LF) power (P<0.05), as both variables decreased more after resistance exercise. When normalized for changes in total power, interactions in LF and HF power were lost. The LF/HF ratio was significantly increased after both resistance and endurance exercise (P<0.05).
  
  
  CONCLUSIONS
  Greater elevations in HR after acute resistance exercise versus acute endurance exercise may be related to greater reductions in cardiac parasympathetic tone.
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Exercise and Cardiovascular Research Laboratory, Champaign, IL 61820, USA. kheffer2@uiuc.edu
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Heffernan
authors.forename: Erin E
authors.initials: EE
authors.lastname: Kelly
authors.forename: Scott R
authors.initials: SR
authors.lastname: Collier
authors.forename: Bo
authors.initials: B
authors.lastname: Fernhall
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D002320:Cardiovascular Physiological Phenomena; D004562:Electrocardiography / Q000379:methods; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D014630:Vagus Nerve / Q000502:physiology