title: Intense endurance training on heart rate and blood pressure variability in runners.
abstract: Physical training with incomplete recovery times can produce significant fatigue. A study of cardiovascular responses showed that there is a sympathetic and a parasympathetic form of fatigue.
  
  
  OBJECTIVE
  The purpose of this experimentation was to measure the effects of intense endurance training on autonomic balance through a spectral analysis study of the heart rate (HR) and systolic blood pressure (SBP).
  
  
  METHODS
  Eight elite runners were tested twice: after a relative rest period (RRP) of 3 wk and after an 12-wk intense training period (ITP) for endurance. At the end of each phase, the subjects were tested by means of a VO2max test and a tilt-table test.
  
  
  RESULTS
  The resting heart rate (HR) variability was lower (P < 0.001) in the intensive training phase. Likewise, there were differences in the low-frequency (0.04-0.150 Hz; LF) and high-frequency (0.150-0.500 Hz; HF) components and the LF/HF ratio of the HR spectral analysis. The LF spectral power was significantly lower in the supine position (P < 0.05) during ITP. Upright tilting was accompanied by a 22.6% reduction in HF values during the rest period, whereas in ITP the HF spectral power rose by 31.2% (P < 0.01) during tilt, characterizing a greater parasympathetic system control. Sympathetic control represented by the LF/HF ratio regressed markedly (P < 0.01) in response to the tilt test in ITP.
  
  
  CONCLUSIONS
  The spectral analysis of SBP in the high frequencies shows that the changes in cardiac parameters are coupled with a decrease in sympathetic vasomotor control (-18%) and a reduction in diastolic pressure (-3.2%) in the response to the tilt test at the end of ITP. Spectral analysis could be a means of demonstrating impairment of autonomic balance for the purpose of detecting a state of fatigue that could result in overtraining.
authors.affiliation: Department of Physiology, Institut de Medecine Aérospatiale du Service de Santé des Armées, Bretigny sur Orge, France. huguesportier@wanadoo.fr
authors.forename: H
authors.initials: H
authors.lastname: Portier
authors.forename: F
authors.initials: F
authors.lastname: Louisy
authors.forename: D
authors.initials: D
authors.lastname: Laude
authors.forename: M
authors.initials: M
authors.lastname: Berthelot
authors.forename: C Y
authors.initials: CY
authors.lastname: Guézennec
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D015331:Cohort Studies; D005221:Fatigue / Q000503:physiopathology; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D012146:Rest / Q000502:physiology; D012420:Running / Q000502:physiology*; D013057:Spectrum Analysis; D018667:Tilt-Table Test