title: Assessing Shortened Field-Based Heart-Rate-Variability-Data Acquisition in Team-Sport Athletes.
abstract: OBJECTIVE
  To compare the LnRMSSD and the LnRMSSD:RR values obtained during a 5-min stabilization period with the subsequent 5-min criterion period and to determine the time course for LnRMSSD and LnRMSSD:RR stabilization at 1-min analysis in elite team-sport athletes.
  
  
  METHODS
  35 elite futsal players (23.9 ± 4.5 y, 174.2 ± 4.0 cm, 74.0 ± 7.5 kg, 1576.2 ± 396.3 m in the Yo-Yo test level 1).
  
  
  METHODS
  The RR-interval recordings were obtained using a portable heart-rate monitor continuously for 10 min in the seated position. The 2 dependent variables analyzed were LnRMSSD and LnRMSSD:RR. To calculate the magnitude of the differences between time periods, effect-size (ES) analysis was conducted. To assess the levels of agreement, intraclass correlation coefficients (ICC) and Bland-Altman plots were used.
  
  
  RESULTS
  The LnRMSSD and LnRMSSD:RR values obtained during the stabilization period (0-5 min) presented very large to nearly perfect ICCs with the values obtained during the criterion period (5-10 min), with trivial ESs. In the ultra-short-term analysis (ie, 1-min segments) the data showed slightly less accurate results, but only trivial to small differences with very large to nearly perfect ICCs were found.
  
  
  CONCLUSIONS
  LnRMSSD and LnRMSSD:RR can be recorded in 5 min without traditional stabilization periods under resting conditions in team-sport athletes. The ultra-short-term analysis (1 min) also revealed acceptable levels of agreement with the criterion.
authors.affiliation: NAR - Nucleus of High Performance in Sport, São Paulo, Brazil.
authors.forename: Lucas A
authors.initials: LA
authors.lastname: Pereira
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Flatt
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Ramirez-Campillo
authors.forename: Irineu
authors.initials: I
authors.lastname: Loturco
authors.forename: Fabio Y
authors.initials: FY
authors.lastname: Nakamura
mesh_terms: D000328:Adult; D056352:Athletes; D005080:Exercise Test; D006339:Heart Rate; D006801:Humans; D008991:Monitoring, Physiologic / Q000379:methods*; D013177:Sports; D013995:Time; D055815:Young Adult