title: Do physical capacity and interchange rest periods influence match exercise-intensity profile in Australian football?
abstract: OBJECTIVE
  The purpose of this study was to determine if Yo-Yo Intermittent Recovery level 2 (Yo-Yo IR2) and the number of interchange rotations affected the match activity profile of elite Australian footballers.
  
  
  METHODS
  Fifteen elite Australian footballers completed the Yo-Yo IR2 before the beginning of the season and played across 22 matches in which match activity profiles were measured via microtechnology devices containing a global positioning system (GPS) and accelerometer. An interchange rotation was counted when a player left the field and was replaced with another player. Yo-Yo IR2 results were further split into high and low groups.
  
  
  RESULTS
  Players match speed decreased from 1st to 4th quarter, while average-speed (m/min: P = .05) and low-speed activity (LSA, <15 km/h) per minute (LSA m/min; P = .06) significantly decreased in the 2nd half. Yo-Yo IR2 influenced the amount of m/min, high-speed running (HSR, >15 km/h) per minute (HSR m/min) and accelerometer load/min throughout the entire match. The number of interchanges significantly influenced the HSR m/min and m/min throughout the match except in the 2nd quarter. Furthermore, the low Yo-Yo IR2 group had significantly less LSA m/min in the 4th quarter than the high Yo-Yo IR2 group (92.2 vs 96.7 m/min, P = .06).
  
  
  CONCLUSIONS
  Both the Yo-Yo IR2 and number of interchanges contribute to m/min and HSR m/min produced by elite Australian footballers, affecting their match activity. However, while it appears that improved Yo-Yo IR2 performance prevents reductions in LSA m/min during a match, higher-speed activities (HSR m/min) and overall physical activity (m/min and load/min) are still reduced in the 4th quarter compared with the 1st quarter.
authors: Movement Sciences, Australian Institute of Sport, Bruce, ACT, Australia.
authors: Mitchell
authors: M
authors: Mooney
authors: Stuart
authors: S
authors: Cormack
authors: Brendan
authors: B
authors: O'Brien
authors: Aaron J
authors: AJ
authors: Coutts
mesh_terms: D000704:Analysis of Variance; D054874:Athletic Performance / Q000502:physiology*; D001315:Australia; D005538:Football / Q000502:physiology*; D040362:Geographic Information Systems; D006801:Humans; D016014:Linear Models; D008297:Male; D010807:Physical Endurance / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology; D012146:Rest; D013647:Task Performance and Analysis; D055815:Young Adult