title: The Beneficial Effect of Parasympathetic Reactivation on Sympathetic Drive During Simulated Rugby Sevens.
abstract: OBJECTIVE
  To determine whether a facilitated recovery via cold-water immersion (CWI) after simulated rugby sevens would influence parasympathetic reactivation and repeated-sprint (RS) performance across 6 matches in a 2-d tournament.
  
  
  METHODS
  Ten male team-sport athletes completed 6 rugby sevens match simulations over 2 d with either postmatch passive recovery (PAS) or CWI in a randomized crossover design. Parasympathetic reactivation was determined via the natural logarithm of the square root of the mean of the sum of the squares of differences between adjacent R-R intervals (ln rMSSD). RS performance was calculated as time taken (s) to complete 6 × 30-m sprints within the first half of each match.
  
  
  RESULTS
  There were large increases in postintervention ln rMSSD between CWI and PAS after all matches (ES 90% CL: +1.13; ±0.21). Average heart rate (HR) during the RS performance task (HRAverage RS) was impaired from baseline from match 3 onward for both conditions. However, HRAverage RS was higher with CWI than with PAS (ES 90% CL: 0.58; ±0.58). Peak HR during the RS performance task (HRPeak RS) was similarly impaired from baseline for match 3 onward during PAS and for match 4 onward with CWI. HRPeak RS was very likely higher with CWI than with PAS (ES 90% CL: +0.80; ±0.56). No effects of match or condition were observed for RS performance, although there were moderate correlations between the changes in HRAverage RS (r 90% CL: -0.33; ±0.14), HRPeak RS (r 90% CL: -0.38; ±0.13), and RS performance.
  
  
  CONCLUSIONS
  CWI facilitated cardiac parasympathetic reactivation after a simulated rugby sevens match. The decline in average and peak HR across matches was partially attenuated by CWI. This decline was moderately correlated with a reduction in RS performance.
authors.affiliation: School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand.
authors.forename: Jamie
authors.initials: J
authors.lastname: Douglas
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Plews
authors.forename: Phil J
authors.initials: PJ
authors.lastname: Handcock
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Rehrer
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D018592:Cross-Over Studies; D005538:Football / Q000502:physiology*; D006321:Heart / Q000294:innervation*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007101:Immersion; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010275:Parasympathetic Nervous System / Q000502:physiology*; D014867:Water
chemical_list: D014867:Water; D019344:Lactic Acid