title: Validity and intra-rater reliability of MyJump app on iPhone 6s in jump performance.
abstract: OBJECTIVE
  Smartphone applications are increasingly used by researchers, coaches, athletes and clinicians. The aim of this study was to examine the concurrent validity and intra-rater reliability of the smartphone-based application, MyJump, against laboratory-based force plate measurements.
  
  
  METHODS
  Cross sectional study.
  
  
  METHODS
  Participants completed counter-movement jumps (CMJ) (n=29) and 30cm drop jumps (DJ) (n=27) on a force plate which were simultaneously recorded using MyJump. To assess concurrent validity, jump height, derived from flight time acquired from each device, was compared for each jump type. Intra-rater reliability was determined by replicating data analysis of MyJump recordings on two occasions separated by seven days.
  
  
  RESULTS
  CMJ and DJ heights derived from MyJump showed excellent agreement with the force plate (ICC values range from 0.991 for CMJ to 0.993) However mean DJ height from the force plate was significantly higher than MyJump (mean difference: 0.87cm, 95% CI: 0.69-1.04cm). Intra-rater reliability of MyJump for both CMJ and DJ was almost perfect (ICC values range from 0.997 for CMJ to 0.998 for DJ); however, mean CMJ and DJ jump height for Day 1 was significantly higher than Day 2 (CMJ: 0.43cm, 95% CI: 0.23-0.62cm); (DJ: 0.38cm, 95% CI: 0.23-0.53cm).
  
  
  CONCLUSIONS
  The present study finds MyJump to be a valid and highly reliable tool for researchers, coaches, athletes and clinicians; however, systematic bias should be considered when comparing MyJump outputs to other testing devices.
authors.affiliation: School of Medical and Applied Sciences, Central Queensland University, Australia. Electronic address: r.stanton@cqu.edu.au.
authors.forename: Robert
authors.initials: R
authors.lastname: Stanton
authors.affiliation: School of Medical and Applied Sciences, Central Queensland University, Australia.
authors.forename: Sally-Anne
authors.initials: SA
authors.lastname: Wintour
authors.affiliation: School of Medical and Applied Sciences, Central Queensland University, Australia.
authors.forename: Crystal O
authors.initials: CO
authors.lastname: Kean
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D003430:Cross-Sectional Studies; D005080:Exercise Test / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008297:Male; D063731:Mobile Applications; D015203:Reproducibility of Results; D000068997:Smartphone; D055815:Young Adult
keywords: Jump height; Muscle power; Physical performance; Skill development; Strength