title: Heart rate variability assessment of the effect of physical training on autonomic cardiac control.
abstract: BACKGROUND
  The effect of exercise interventions on autonomic nervous system (ANS) control of the heart by heart rate variability (HRV) is often investigated in just one position. It was hypothesized that results of exercise-induced changes on ANS are dependent on body position and that it is possible to distinguish between exercise induced changes in vagal and sympathetic influence by taking measurements in different body positions.
  
  
  METHODS
  One hundred eighty-three (male = 100, female = 83) healthy volunteers, between 18 and 22 years, participated in a prospective twelve week medium to high intensity exercise intervention study with a self-control design. The influence of the exercise intervention was investigated on supine, rising, and standing as well as on the orthostatic response. Time domain, frequency domain and nonlinear (Poincaré) HRV analysis were performed.
  
  
  RESULTS
  The exercise intervention lead to a significant increase (P < 0.05) in vagal influence during supine, rising, and standing. Sympathetic control in the supine position was decreased and increased during rising and standing. In the initial orthostatic response to rising from the supine position, the exercise intervention lead to increased (P < 0.05) vagal withdrawal as well as increased sympathetic control. The orthostatic response measured as the difference between standing and supine indicated only an exercise induced increase in sympathetic control.
  
  
  CONCLUSIONS
  Exercise-induced changes in sympathetic and parasympathetic ANS control differ, depending on posture and period of measurement. Exercise induced changes in parasympathetic and sympathetic outflow, respectively, can be extracted from measurements from supine, through the orthostatic response, to standing, thereby detecting changes in ANS that are otherwise obscured.
authors: Section Sports Medicine, Faculty of Health Sciences, University of Pretoria, South Africa. Rina.Grant@up.ac.za
authors: Catharina C
authors: CC
authors: Grant
authors: Margaretha
authors: M
authors: Viljoen
authors: Dina C
authors: DC
authors: Janse van Rensburg
authors: Paola S
authors: PS
authors: Wood
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000293:Adolescent; D000367:Age Factors; D000886:Anthropometry; D001341:Autonomic Nervous System / Q000502:physiology*; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010275:Parasympathetic Nervous System / Q000502:physiology; D010806:Physical Education and Training / Q000379:methods; D011187:Posture / Q000502:physiology*; D011446:Prospective Studies; D018709:Statistics, Nonparametric; D016683:Supine Position / Q000502:physiology; D055815:Young Adult