title: May a unitary autonomic index help assess autonomic cardiac regulation in elite athletes? Preliminary observations on the national Italian Olympic committee team.
abstract: BACKGROUND
  Long term endurance training, as occurring in elite athletes, is associated to cardiac neural remodeling in favor of cardioprotective vagal mechanisms, resulting in resting bradycardia and augmented contribution of cardiac parasympathetic nerve activity. Autonomic assessment can be performed by way of heart rate variability. This technique however provides multiple indices, and there is not yet complete agreement on their specific significance. Purpose of the study was to assess whether a rank transformation and radar plot could provide a unitary autonomic index, capable to show a correlation between intensity of individual work and quality of autonomic regulation.
  
  
  METHODS
  We studied 711 (23.6±6.2 years) elite athletes that took part in the selection procedure for the 2016 Rio Olympic Games for the National Italian Olympic Committee (CONI). Indices from Heart Rate Variability HRV obtained at rest, during standing up and during recovery from an exercise test were used to compute a percent ranked unitary autonomic index for sport (ANSIs), taken as proxy of quality of autonomic regulation.
  
  
  RESULTS
  Within the observed wide range of energy expenditure, the unitary autonomic index ANSIs appears significantly correlated to individual and discipline specific training workloads (r=0.25, P<0.001 and r=0.78, P<0.001, respectively), correcting for possible age and gender bias. ANSIs also positively correlates to lipid profile.
  
  
  CONCLUSIONS
  Estimated intensity of physical activity correlates with quality of cardiac autonomic regulation, as expressed by a novel unitary index of cardiac autonomic regulation. ANSIs could provide a novel and convenient approach to individual autonomic evaluation in athletes.
authors.affiliation: Department of Medical Biotechnology and Translational Medicine (BIOMETRA), University of Milan, Milan, Italy.|Section of Exercise Medicine and Functional Conditions, Humanitas Clinical and Research Center, Rozzano, Milan, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Sala
authors.affiliation: Department of Medical Biotechnology and Translational Medicine (BIOMETRA), University of Milan, Milan, Italy.|Section of Exercise Medicine and Functional Conditions, Humanitas Clinical and Research Center, Rozzano, Milan, Italy.
authors.forename: Mara
authors.initials: M
authors.lastname: Malacarne
authors.affiliation: Department of Medical Biotechnology and Translational Medicine (BIOMETRA), University of Milan, Milan, Italy.|Section of Exercise Medicine and Functional Conditions, Humanitas Clinical and Research Center, Rozzano, Milan, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Tosi
authors.affiliation: Sports Medicine Institute CONI, Rome, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Benzi
authors.affiliation: Department of Statistics and Quantitative Methods, University of Milano-Bicocca, Milan, Italy.
authors.forename: Nadia
authors.initials: N
authors.lastname: Solaro
authors.affiliation: Sports Medicine Institute CONI, Rome, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Tamorri
authors.affiliation: Sports Medicine Institute CONI, Rome, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Spataro
authors.affiliation: Department of Medical Biotechnology and Translational Medicine (BIOMETRA), University of Milan, Milan, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Pagani
authors.affiliation: Department of Medical Biotechnology and Translational Medicine (BIOMETRA), University of Milan, Milan, Italy - daniela.lucini@unimi.it.|Section of Exercise Medicine and Functional Conditions, Humanitas Clinical and Research Center, Rozzano, Milan, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Lucini
mesh_terms: D000293:Adolescent; D000328:Adult; D056352:Athletes; D001341:Autonomic Nervous System / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007558:Italy; D008297:Male; D013177:Sports / Q000502:physiology*; D055815:Young Adult