title: Validity and reliability of a novel iPhone app for the measurement of barbell velocity and 1RM on the bench-press exercise.
abstract: The purpose of this study was to analyse the validity and reliability of a novel iPhone app (named: PowerLift) for the measurement of mean velocity on the bench-press exercise. Additionally, the accuracy of the estimation of the 1-Repetition maximum (1RM) using the load-velocity relationship was tested. To do this, 10 powerlifters (Mean (SD): age = 26.5 ± 6.5 years; bench press 1RM · kg-1= 1.34 ± 0.25) completed an incremental test on the bench-press exercise with 5 different loads (75-100% 1RM), while the mean velocity of the barbell was registered using a linear transducer (LT) and Powerlift. Results showed a very high correlation between the LT and the app (r = 0.94, SEE = 0.028 m · s-1) for the measurement of mean velocity. Bland-Altman plots (R2= 0.011) and intraclass correlation coefficient (ICC = 0.965) revealed a very high agreement between both devices. A systematic bias by which the app registered slightly higher values than the LT (P < 0.05; mean difference (SD) between instruments = 0.008 ± 0.03 m · s-1). Finally, actual and estimated 1RM using the app were highly correlated (r = 0.98, mean difference (SD) = 5.5 ± 9.6 kg, P < 0.05). The app was found to be highly valid and reliable in comparison with a LT. These findings could have valuable practical applications for strength and conditioning coaches who wish to measure barbell velocity in the bench-press exercise.
authors.affiliation: a Department of Sport Sciences , Universidad Europea de Madrid , Madrid , Spain.
authors.forename: Carlos
authors.identifier: http://orcid.org/0000-0002-8329-1581
authors.initials: C
authors.lastname: Balsalobre-Fernández
authors.affiliation: b Department of Research & Development , Powerexplosive Center , Madrid , Spain.
authors.forename: David
authors.initials: D
authors.lastname: Marchante
authors.affiliation: b Department of Research & Development , Powerexplosive Center , Madrid , Spain.
authors.forename: Mario
authors.initials: M
authors.lastname: Muñoz-López
authors.affiliation: a Department of Sport Sciences , Universidad Europea de Madrid , Madrid , Spain.
authors.forename: Sergio L
authors.initials: SL
authors.lastname: Jiménez
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D006801:Humans; D008297:Male; D063731:Mobile Applications; D053580:Muscle Strength / Q000502:physiology; D015588:Observer Variation; D015203:Reproducibility of Results; D055070:Resistance Training / Q000379:methods; D000068997:Smartphone; D014891:Weight Lifting / Q000502:physiology*
keywords: Biomechanics; performance; resistance training; smartphone