title: Effect of Sampling Frequency on Isometric Midthigh-Pull Kinetics.
abstract: OBJECTIVE
  Skeletal-muscle function can be evaluated using force-times curves generated via the isometric midthigh pull (IMTP). Various sampling frequencies (500-1000 Hz) have been used for IMTP assessments; however, no research has investigated the influence of sampling frequency on IMTP kinetics. Therefore, the purpose of this study was to investigate the influence of sampling frequency on kinetic variables during the IMTP, including peak force, time-specific force values (100, 150, and 200 ms), and rate of force development (RFD) at 3 time bands (0-100, 0-150, 0-200 ms).
  
  
  METHODS
  Academy rugby league players (n = 30, age 17.5 ± 1.1 y, height 1.80 ± 0.06 m, mass 85.4 ± 10.3 kg) performed 3 IMTP trials on a force platform sampling at 2000 Hz, which was subsequently down-sampled to 1500, 1000, and 500 Hz for analysis.
  
  
  RESULTS
  Intraclass correlation coefficients (ICC) and coefficients of variation (CV) demonstrated high within-session reliability for all force and RFD variables across all sampling frequencies (ICC ≥ .80, CV ≤ 10.1%). Repeated-measures analysis of variance revealed no significant differences (P > .05, Cohen d ≤ 0.009) in kinetic variables between sampling frequencies. Overall, high reliability was observed across all sampling frequencies for all kinetic variables, with no significant differences (P > .05) for each kinetic variable across sampling frequencies.
  
  
  CONCLUSIONS
  Practitioners and scientists may consider sampling as low as 500 Hz when measuring peak force, time-specific force values, and RFD at predetermined time bands during the IMTP for accurate and reliable data.
authors.affiliation: Human Performance Laboratory, University of Salford, Greater Manchester, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dos'Santos
authors.forename: Paul A
authors.initials: PA
authors.lastname: Jones
authors.forename: Jonathan
authors.initials: J
authors.lastname: Kelly
authors.forename: John J
authors.initials: JJ
authors.lastname: McMahon
authors.forename: Paul
authors.initials: P
authors.lastname: Comfort
authors.forename: Christopher
authors.initials: C
authors.lastname: Thomas
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D056352:Athletes; D001696:Biomechanical Phenomena; D005080:Exercise Test / Q000379:methods*; D005538:Football; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D015203:Reproducibility of Results; D013848:Thigh / Q000502:physiology*