title: Modeling the association between HR variability and illness in elite swimmers.
abstract: OBJECTIVE
  To determine whether HR variability (HRV), an indirect measure of autonomic control, is associated with upper respiratory tract and pulmonary infections, muscular affections, and all-type pathologies in elite swimmers.
  
  
  METHODS
  For this study, 7 elite international and 11 national swimmers were observed weekly for 2 yr. The indexes of cardiac autonomic regulation in supine and orthostatic position were assessed as explanatory variables by time domain (SD1, SD2) and spectral analyses (high frequency [HF] = 0.15-0.40 Hz, low frequency [LF] = 0.04-0.15 Hz, and HF/LF ratio) of HRV. Logistic mixed models described the relationship between the explanatory variables and the risk of upper respiratory tract and pulmonary infections, muscular affections, and all-type pathologies.
  
  
  RESULTS
  The risk of all-type pathologies was higher for national swimmers and in winter (P < 0.01). An increase in the parasympathetic indexes (HF, SD1) in the supine position assessed 1 wk earlier was linked to a higher risk of upper respiratory tract and pulmonary infections (P < 0.05) and to a higher risk of muscular affections (increase in HF, P < 0.05). Multivariate analyses showed (1) a higher all-type pathologies risk in winter and for an increase in the total power of HRV associated with a decline SD1 in supine position, (2) a higher all-type pathologies risk in winter associated with a decline in HF assessed 1 wk earlier in orthostatic position, and (3) a higher risk of muscular affections in winter associated with a decrease SD1 and an increase LF in orthostatic position.
  
  
  CONCLUSIONS
  Swimmers' health maintenance requires particular attention when autonomic balance shows a sudden increase in parasympathetic indices in the supine position assessed 1 wk earlier evolving toward sympathetic predominance in supine and orthostatic positions.
authors.affiliation: Research Service, French Swimming Federation, Paris, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Hellard
authors.forename: Fanny
authors.initials: F
authors.lastname: Guimaraes
authors.forename: Marta
authors.initials: M
authors.lastname: Avalos
authors.forename: Nicolas
authors.initials: N
authors.lastname: Houel
authors.forename: Christophe
authors.initials: C
authors.lastname: Hausswirth
authors.forename: Jean François
authors.initials: JF
authors.lastname: Toussaint
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D018482:Muscle, Skeletal / Q000293:injuries / Q000503:physiopathology*; D011187:Posture / Q000502:physiology; D012141:Respiratory Tract Infections / Q000503:physiopathology*; D012621:Seasons; D013550:Swimming / Q000502:physiology*; D055815:Young Adult