title: Exercise training improves heart rate variability after methamphetamine dependency.
abstract: OBJECTIVE
  Heart rate variability (HRV) reflects a healthy autonomic nervous system and is increased with physical training. Methamphetamine dependence (MD) causes autonomic dysfunction and diminished HRV. We compared recently abstinent methamphetamine-dependent participants with age-matched, drug-free controls (DF) and also investigated whether HRV can be improved with exercise training in the methamphetamine-dependent participants.
  
  
  METHODS
  In 50 participants (MD = 28; DF = 22), resting heart rate (HR; R-R intervals) was recorded over 5 min while seated using a monitor affixed to a chest strap. Previously reported time domain (SDNN, RMSSD, pNN50) and frequency domain (LFnu, HFnu, LF/HF) parameters of HRV were calculated with customized software. MD were randomized to thrice-weekly exercise training (ME = 14) or equal attention without training (MC = 14) over 8 wk. Groups were compared using paired and unpaired t-tests. Statistical significance was set at P ≤ 0.05.
  
  
  RESULTS
  Participant characteristics were matched between groups (mean ± SD): age = 33 ± 6 yr; body mass = 82.7 ± 12 kg, body mass index = 26.8 ± 4.1 kg·min. Compared with DF, the MD group had significantly higher resting HR (P < 0.05), LFnu, and LF/HF (P < 0.001) as well as lower SDNN, RMSSD, pNN50, and HFnu (all P < 0.001). At randomization, HRV indices were similar between ME and MC groups. However, after training, the ME group significantly (all P < 0.001) increased SDNN (+14.7 ± 2.0 ms, +34%), RMSSD (+19.6 ± 4.2 ms, +63%), pNN50 (+22.6% ± 2.7%, +173%), HFnu (+14.2 ± 1.9, +60%), and decreased HR (-5.2 ± 1.1 bpm, -7%), LFnu (-9.6 ± 1.5, -16%), and LF/HF (-0.7 ± 0.3, -19%). These measures did not change from baseline in the MC group.
  
  
  CONCLUSIONS
  HRV, based on several conventional indices, was diminished in recently abstinent, methamphetamine-dependent individuals. Moreover, physical training yielded a marked increase in HRV, representing increased vagal modulation or improved autonomic balance.
authors.affiliation: 1Exercise Physiology Research Laboratory, Departments of Medicine and Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CA; 2Integrated Substance Abuse Programs, Semel Institute, David Geffen School of Medicine, UCLA, Los Angeles, CA; and 3Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA.
authors.forename: Brett Andrew
authors.initials: BA
authors.lastname: Dolezal
authors.forename: Joy
authors.initials: J
authors.lastname: Chudzynski
authors.forename: Daniel
authors.initials: D
authors.lastname: Dickerson
authors.forename: Larissa
authors.initials: L
authors.lastname: Mooney
authors.forename: Richard A
authors.initials: RA
authors.lastname: Rawson
authors.forename: Alan
authors.initials: A
authors.lastname: Garfinkel
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Cooper
mesh_terms: D000328:Adult; D019969:Amphetamine-Related Disorders / Q000503:physiopathology*; D000886:Anthropometry; D001341:Autonomic Nervous System / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008694:Methamphetamine; D053580:Muscle Strength / Q000502:physiology; D010349:Patient Compliance; D010806:Physical Education and Training; D010807:Physical Endurance / Q000502:physiology; D055070:Resistance Training
chemical_list: D008694:Methamphetamine