title: [Spectrum analysis of the variability of heart rate in athletes].
abstract: OBJECTIVE
  Characterize power spectrum pattern of the heart rate variability and assessment of the relative contributions of sympathetic and parasympathetic cardiac nervous system control in athletes.
  
  
  METHODS
  Prospective study of athletes and sedentary healthy control group sex and age matched.
  
  
  METHODS
  8 athletes, 3 female and 5 male, swimming (4), canoeing (2) and cycling (2), aged 17.4 +/- 3.6 years, and 8 sedentary healthy controls. ECG signals were recorded after a period of 15 minutes in supine rest with controlled breathing at 15 cycles/min. Signal acquisition was done at 300 samples/sec. From 512 consecutive heart beats, we calculated the average, the standard deviation, the maximum and the minimum values and the rate between the longest and the shortest R-R interval (E/I). We also calculated, after computing the fast Fourier transform, the total spectrum power, the low frequency component (LF, from 0.01 to 0.15 Hz) and the high frequency component (HF, greater than 0.15 Hz) and its ratio (LF/HF).
  
  
  RESULTS
  The average R-R interval was 921 +/- 154.2 msecs and 673.2 +/- 98 msecs, the standard deviation was 72.5 and 29.4 msecs and the ratio E/I 1.63 +/- 0.14 and 1.28 +/- 0.08, respectively for athletes and control group. Differences between groups were significant (p less than 0.01) for all parameters, with higher variability in the athletes. Both spectral bands (LF and HF) and higher power in athletes (LF = 0.54 +/- 0.23 and HF = 0.76 +/- 0.14) than in the control group (LF = 0.14 +/- 0.10 and HF = 0.18 +/- 0.15) (p less than 0.001). There were no significant differences for LF/HF ratio, or normalized LF (LF%) or normalized HF (HF%) between groups.
  
  
  CONCLUSIONS
  The present results indicates higher power of both spectral bands (LF and HF) and higher amplitude of the respective peaks in athletes when compared with healthy sedentary, with a clear predominance of the HF band in the total spectral power density, which suggest that the higher heart rate variability observed in athletes reveals the predominance of parasympathetic activity, without reduction of the sympathetic tone.
authors.affiliation: Servico de Terapêutica Médica da F. M. do Porto.
authors.forename: O
authors.initials: O
authors.lastname: Costa
authors.forename: J
authors.initials: J
authors.lastname: Freitas
authors.forename: J
authors.initials: J
authors.lastname: Puig
authors.forename: M J
authors.initials: MJ
authors.lastname: Carvalho
authors.forename: A
authors.initials: A
authors.lastname: Freitas
authors.forename: J
authors.initials: J
authors.lastname: Ramos
authors.forename: N
authors.initials: N
authors.lastname: Puga
authors.forename: I
authors.initials: I
authors.lastname: Lomba
authors.forename: P
authors.initials: P
authors.lastname: Fernandes
authors.forename: F
authors.initials: F
authors.lastname: de Freitas
mesh_terms: D000293:Adolescent; D000328:Adult; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D013177:Sports
vernacular_title: Análise espectral da variabilidade da frequência cardíaca em atletas.