title: Concurrent validity of the Gyko inertial sensor system for the assessment of vertical jump height in female sub-elite youth soccer players.
abstract: BACKGROUND
  The aim of the present study was to verify concurrent validity of the Gyko inertial sensor system for the assessment of vertical jump height.
  
  
  METHODS
  Nineteen female sub-elite youth soccer players (mean age: 14.7 ± 0.6 years) performed three trials of countermovement (CMJ) and squat jumps (SJ), respectively. Maximal vertical jump height was simultaneously quantified with the Gyko system, a Kistler force-plate (i.e., gold standard), and another criterion device that is frequently used in the field, the Optojump system.
  
  
  RESULTS
  Compared to the force-plate, the Gyko system determined significant systematic bias for mean CMJ (-0.66 cm,p< 0.01,d= 1.41) and mean SJ (-0.91 cm,p< 0.01,d= 1.69) height. Random bias was ± 3.2 cm for CMJ and ± 4.0 cm for SJ height and intraclass correlation coefficients (ICCs) were "excellent" (ICC = 0.87 for CMJ and 0.81 for SJ). Compared to the Optojump device, the Gyko system detected a significant systematic bias for mean CMJ (0.55 cm,p< 0.05,d= 0.94) but not for mean SJ (0.39 cm) height. Random bias was ± 3.3 cm for CMJ and ± 4.2 cm for SJ height and ICC values were "excellent" (ICC = 0.86 for CMJ and 0.82 for SJ).
  
  
  CONCLUSIONS
  Consequently, apparatus specific regression equations were provided to estimate true vertical jump height for the Kistler force-plate and the Optojump device from Gyko-derived data. Our findings indicate that the Gyko system cannot be used interchangeably with a Kistler force-plate and the Optojump device in trained individuals. It is suggested that practitioners apply the correction equations to estimate vertical jump height for the force-plate and the Optojump system from Gyko-derived data.
authors.affiliation: Division of Training and Movement Science, Research Focus Cognition Sciences, University of Potsdam, Am Neuen Palais 10 (Bldg. 12), 14469 Potsdam, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Lesinski
authors.affiliation: Division of Training and Movement Science, Research Focus Cognition Sciences, University of Potsdam, Am Neuen Palais 10 (Bldg. 12), 14469 Potsdam, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Muehlbauer
authors.affiliation: Division of Training and Movement Science, Research Focus Cognition Sciences, University of Potsdam, Am Neuen Palais 10 (Bldg. 12), 14469 Potsdam, Germany.
authors.forename: Urs
authors.initials: U
authors.lastname: Granacher
keywords: Accelerometer; Athlete testing; Countermovement jump; Field test; Lower-extremity muscle power; Squat jump