title: Repeated Acceleration Ability (RAA): A New Concept with Reference to Top-Level Field and Assistant Soccer Referees.
abstract: OBJECTIVE
  To perform an exploratory characterization of repeated sprint sequences (RSS) and repeated acceleration sequences (RAS) in top level soccer referees.
  
  
  METHODS
  7 field and 7 assistant referees were monitored during 2007 America's Soccer Cup with GPS technology. Sprints of >18 km·h(-1) and accelerations of >1.5 m·s(-2) were considered as high intensity activities. RSS and RAS were defined as a minimum of 3 consecutive bouts interspersed with a maximum of 45 s.
  
  
  RESULTS
  Field and assistant referees performed substantially more accelerations than sprints. Neither field nor assistant referees recorded any RSS. In contrast, total distance performing RAS amounted to ∼37% and ∼20% of the total distance covered by accelerations during the entire match for field and assistant referees, respectively. Only field referees exhibited fatigue-related reductions in RAS characteristics between halves.
  
  
  CONCLUSIONS
  The results of the present study would appear to support the appropriateness of a repeated acceleration ability (RAA) concept, instead of the repeated sprint ability (RSA) concept, in soccer referees. Further studies should assess RAS in referees and athletes of different team sports for designing better training exercises and physiological testing.
authors.affiliation: Department of Physical Education and Sport, University of Granada, Spain.
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Barberó-Álvarez
authors.affiliation: Post-Graduate Program in Physical Education, Catholic University of Brasilia, Brasilia, Brazil.
authors.forename: Daniel
authors.initials: D
authors.lastname: Boullosa
authors.affiliation: Department of Physical Education, State University of Londrina, Londrina, Brazil.
authors.forename: Fábio Yuzo
authors.initials: FY
authors.lastname: Nakamura
authors.affiliation: Carabobo FC, Valencia, Venezuela.
authors.forename: Germán
authors.initials: G
authors.lastname: Andrín
authors.affiliation: Department of Sport and Exercise Sciences, School of Social Sciences and Law, Teesside University, Middlesbrough, United Kingdom.
authors.forename: Matthew
authors.initials: M
authors.lastname: Weston
keywords: Fatigue; Global Positioning System; Intermittent Sports; Performance; Time Motion