title: The reliability of MinimaxX accelerometers for measuring physical activity in Australian football.
abstract: OBJECTIVE
  To assess the reliability of triaxial accelerometers as a measure of physical activity in team sports.
  
  
  METHODS
  Eight accelerometers (MinimaxX 2.0, Catapult, Australia) were attached to a hydraulic universal testing machine (Instron 8501) and oscillated over two protocols (0.5 g and 3.0 g) to assess within- and between device reliability. A static assessment was also conducted. Secondly, 10 players were instrumented with two accelerometers during Australian football matches. The vector magnitude was calculated, expressed as Player load and assessed for reliability using typical error (TE) ± 90% confidence intervals (CI), and expressed as a coefficient of variation (CV%). The smallest worthwhile difference (SWD) in Player load was calculated to determine if the device was capable of detecting differences in physical activity.
  
  
  RESULTS
  Laboratory: Within- (Dynamic: CV 0.91 to 1.05%; Static: CV 1.01%) and between-device (Dynamic: CV 1.02 to 1.04%; Static: CV 1.10%) reliability was acceptable across each test. Field: The between-device reliability of accelerometers during Australian football matches was also acceptable (CV 1.9%). The SWD was 5.88%.
  
  
  CONCLUSIONS
  The reliability of the MinimaxX accelerometer is acceptable both within and between devices under controlled laboratory conditions, and between devices during field testing. MinimaxX accelerometers can be confidently utilized as a reliable tool to measure physical activity in team sports across multiple players and repeated bouts of activity. The noise (CV%) of Player load was lower than the signal (SWD), suggesting that accelerometers can detect changes or differences in physical activity during Australian football.
authors.affiliation: School of Sport and Exercise Science, Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia.
authors.forename: Luke J
authors.initials: LJ
authors.lastname: Boyd
authors.forename: Kevin
authors.initials: K
authors.lastname: Ball
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Aughey
mesh_terms: D056044:Actigraphy / Q000295:instrumentation*; D000328:Adult; D054874:Athletic Performance; D001315:Australia; D001696:Biomechanical Phenomena; D004867:Equipment Design; D005538:Football; D006801:Humans; D008297:Male; D008422:Materials Testing; D008904:Miniaturization; D009043:Motor Activity; D015203:Reproducibility of Results; D013647:Task Performance and Analysis; D055815:Young Adult