title: Variability of force magnitude and force duration in manual and instrument-based manipulation techniques.
abstract: OBJECTIVE
  The goal of this study was to compare the variation of manipulative forces produced by instruments and a manual technique.
  
  
  METHODS
  Four operators (2 experts and 2 novices) used 4 different mechanical instruments to apply force to a uniaxial load cell. A different group of 2 expert and 2 novice operators used a traditional manual technique to apply force to a sensor mat. Two primary outcome variables were obtained from each sensor system: peak-to-peak force magnitude (N) and peak-to-peak force duration (millisecond). Multiple analyses were performed to determine the absolute differences and variation in each variable.
  
  
  RESULTS
  Force-producing instrumentation exhibited less variation in absolute force and force duration compared to manual techniques. However, the same instrument in the hands of different operators often produced significantly different values of absolute force and force duration. Although absolute values of force magnitude generally differed between operators, intraoperator variation was equal for instruments and the manual technique. Conversely, for force duration, significant differences in interoperator variability were observed for the manual technique and for one of the instruments.
  
  
  CONCLUSIONS
  Force-producing instruments reduce absolute variation in force magnitude and duration. However, this reduction does not eliminate significant differences in absolute force parameters observed to occur between some operators using the same instrument. Given these observations, claims of instrument superiority that do not account for interoperator variability should be considered with caution.
authors.affiliation: University of Alberta, Edmonton, Canada. greg.kawchuk@ualberta.ca
authors.forename: Gregory N
authors.initials: GN
authors.lastname: Kawchuk
authors.forename: Narasimha G
authors.initials: NG
authors.lastname: Prasad
authors.forename: Randall C
authors.initials: RC
authors.lastname: McLeod
authors.forename: Tasha
authors.initials: T
authors.lastname: Liddle
authors.forename: Tianye
authors.initials: T
authors.lastname: Li
authors.forename: Qiaohao
authors.initials: Q
authors.lastname: Zhu
mesh_terms: D006801:Humans; D026201:Musculoskeletal Manipulations / Q000295:instrumentation* / Q000379:methods*; D013997:Time Factors; D016474:Weight-Bearing