title: Match play performance characteristics that predict post-match creatine kinase responses in professional rugby union players.
abstract: BACKGROUND
  Rugby union players can take several days to fully recover from competition. Muscle damage induced during the match has a major role in player recovery; however the specific characteristics of match play that predict post-match muscle damage remains unclear. We examined the relationships between a marker of muscle damage and performance characteristics associated with physical contacts and high-speed movement in professional rugby union players.
  
  
  METHODS
  Twenty-eight professional rugby union players (15 forwards, 13 backs) participated in this study. Data were obtained from 4 European Cup games, with blood samples collected 2 h pre, and 16 and 40 h post-match, and were subsequently analysed for creatine kinase (CK). Relationships between changes in CK concentrations and number of physical contacts and high-speed running markers, derived from performance analysis and global positioning system (GPS) data, were assessed.
  
  
  RESULTS
  Moderate and moderate-large effect-size correlations were identified between contact statistics from performance analysis and changes in CK at 16 and 40 h post-match in forwards and backs, respectively (e.g. backs; total impacts vs. ΔCK (r = 0.638, p < 0.01) and Δ% CK (r = 0.454, p < 0.05) 40 h post-match). Furthermore, moderate effect-size correlations were found between measures of high-speed running and sprinting, and changes in CK at 16 and 40 h post-match within the backs (e.g. high-speed running distance vs. ΔCK (r = 0.434, p = 0.056) and Δ% CK (r = 0.437, p = 0.054) 40 hrs post-match).
  
  
  CONCLUSIONS
  Our data demonstrate that muscle damage induced by professional rugby union match play is to some extent predicted by the number of physical contacts induced during performance. Furthermore, we show for the first time that muscle damage in backs players is predicted by high-speed running measures derived from GPS. These data increase the understanding of the causes of muscle damage in rugby union; performance markers could potentially be used to tailor individual recovery strategies and subsequent training following rugby union competition.
authors.affiliation: Applied Sports Technology Exercise and Medicine Research Centre (A-STEM), Health and Sport Portfolio, Talbot Building, College of Engineering, Swansea University, Singleton Park, Wales, SA2 8PP UK ; Scarlets Rugby, Llanelli, SA14 9UZ UK.
authors.forename: Marc R
authors.initials: MR
authors.lastname: Jones
authors.affiliation: Department of Sport, Exercise & Rehabilitation, Faculty of Health and Life Science, Northumbria University, Northumberland Building, Newcastle upon Tyne, NE1 8ST UK.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: West
authors.affiliation: Scarlets Rugby, Llanelli, SA14 9UZ UK.
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Harrington
authors.affiliation: School of Sport, Health and Exercise Science Bangor University, Bangor, Gwynedd, LL572PZ Wales.
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Cook
authors.affiliation: Applied Sports Technology Exercise and Medicine Research Centre (A-STEM), Health and Sport Portfolio, Talbot Building, College of Engineering, Swansea University, Singleton Park, Wales, SA2 8PP UK.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Bracken
authors.affiliation: Faculty of Life Sciences and Education, University of South Wales, Swansea, CF37 1DL Wales.
authors.forename: David A
authors.initials: DA
authors.lastname: Shearer
authors.affiliation: Applied Sports Technology Exercise and Medicine Research Centre (A-STEM), Health and Sport Portfolio, Talbot Building, College of Engineering, Swansea University, Singleton Park, Wales, SA2 8PP UK.
authors.forename: Liam P
authors.initials: LP
authors.lastname: Kilduff
keywords: Athlete management; Muscle damage; Performance analysis