title: Refining the deceleration capacity index in phase-rectified signal averaging to assess physical conditioning level.
abstract: BACKGROUND
  Deceleration capacity (DC) of heart rate is a measure of cardiac vagal modulation. This study introduced a DC adaptation (Modified Index) that measured the velocity of change in the phase-rectified signal averaging curve, and assessed its ability to discriminate athletes from controls.
  
  
  METHODS
  The Modified Index was compared to Standard DC approach in a prospective case-control study. Subjects were classified according to maximal metabolic equivalents as the control group (CG) and athlete group (AG). The Modified Index was compared to Standard DC and classical approaches (RMSSD and HF) by the area under receiver operating characteristic curve (AUC) using 10,000 bootstraps.
  
  
  RESULTS
  In Standard DC and Modified Index bootstrap median values were (ms), respectively, 11.80 and 17.94 (p<0.01) in CG, and 25.98 and 45.62 in AG (p<0.01). AUC (mean±SD) was 0.70±0.12 for Standard DC and 0.96±0.04 for Modified Index (p<0.01).
  
  
  CONCLUSIONS
  Modified Index appropriately discriminates athletes from healthy sedentary subjects.
authors.affiliation: Programa de Engenharia Biomédica, COPPE, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Olivassé
authors.initials: O
authors.lastname: Nasario-Junior
authors.affiliation: Hospital Universitário Pedro Ernesto, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brazil. Electronic address: ecgar@yahoo.com.
authors.forename: Paulo Roberto
authors.initials: PR
authors.lastname: Benchimol-Barbosa
authors.affiliation: Programa de Engenharia Biomédica, COPPE, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Jurandir
authors.initials: J
authors.lastname: Nadal
mesh_terms: D000328:Adult; D000465:Algorithms; D003654:Deceleration; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D004562:Electrocardiography / Q000379:methods*; D005080:Exercise Test / Q000379:methods; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D064797:Physical Conditioning, Human; D010809:Physical Fitness / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013177:Sports / Q000502:physiology*
keywords: Cardiac vagal modulation; Deceleration capacity index; HR variability; Phase-rectified signal averaged; Physical conditioning