title: Reliability and validity of sports accelerometers during static and dynamic testing.
abstract: OBJECTIVE
  To investigate the validity and reliability of accelerometry of the SPI-ProX II dual data logger (GPSports, Canberra, Australia).
  
  
  METHODS
  Controlled laboratory assessments determined the accuracy and reproducibility of raw accelerometer data. Intra- and interdevice reliability assessed the ability of the SPI-ProX II accelerometers to repeatedly measure peak gravitational accelerations (g) during impact-based testing. Static and dynamic validity testing assessed the accuracy of SPI-ProX II accelerometers against a criterion-referenced accelerometer. Dynamic validity was assessed over a range of frequencies from 5 to 15 Hz.
  
  
  RESULTS
  Intradevice reliability found no differences (P < .05) between 4 SPI-ProX II accelerometers, with a low coefficient of variation (1.87-2.21%). SPI-ProX II accelerometers demonstrated small to medium effect-size (ES) differences (0.10-0.44) between groups and excellent interdevice reliability, with no difference found between units (F = 0.826, P = .484). Validity testing revealed significant differences between devices (P = .001), with high percentage differences (27.5-30.5%) and a large ES (>3.44).
  
  
  CONCLUSIONS
  SPI-ProX II accelerometers demonstrated excellent intra- and interaccelerometer reliability. However, static and dynamic validity were poor, and caution is recommended when measuring the absolute magnitude of acceleration, particularly for high-frequency movements. Regular assessment of individual devices is advised, particularly for mechanical damage and signal-drift errors. It is recommended that guidelines be provided by the manufacturer on measuring shifts in the base accelerometer signal, including time frames for assessing accelerometer axis, magnitude of errors, and calibration of accelerometers from a stable reference point.
authors.affiliation: Faculty of Health, University of Technology Sydney, Sydney, NSW, Australia.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Kelly
authors.forename: Aron J
authors.initials: AJ
authors.lastname: Murphy
authors.forename: Mark L
authors.initials: ML
authors.lastname: Watsford
authors.forename: Damien
authors.initials: D
authors.lastname: Austin
authors.forename: Michael
authors.initials: M
authors.lastname: Rennie
mesh_terms: D000054:Acceleration; D061725:Accelerometry / Q000295:instrumentation*; D040362:Geographic Information Systems; D006112:Gravitation; D006801:Humans; D015203:Reproducibility of Results; D013177:Sports