Ka. Khalaf et al., Determination of the effect of lift characteristics on dynamic performanceprofiles during manual materials handling tasks, ERGONOMICS, 42(1), 1999, pp. 126-145
In any quantitative gait or occupational biomechanics investigation, the qu
antification of the different kinematic, kinetic, and electromyographic par
ameters is essential towards assessment of functional capacity and developm
ent of a biomechanical profile of the task demands. In the current study, t
he authors presented a methodology for using inferential statistics to eval
uate the effect of lift characteristics on phase-dependent and phase-indepe
ndent variability in performance. Using a database of kinematic and kinetic
profiles obtained from a manual lifting study, the phase-dependent effects
of lift characteristics: box mass (load), mode (technique of lift), and sp
eed (frequency of lift) were investigated through the use of analysis of va
riance (ANOVA) techniques, which recognize the vectorial constitution of th
e profiles. In addition, the Karhunen-Loeve Expansion (KLE) feature extract
ion method was used for representing the lifting patterns of measured joint
angular position, velocity, acceleration, and net muscular torque profiles
obtained from a 2-D biomechanical lifting model in order to study the phas
e-independent effects. In comparison to traditional descriptive statistical
analyses currently used in various occupational biomechanics experimental
investigations, this method allows the significant information content of t
he time varying signal to be captured, enhancing the sensitivity of subsequ
ent hypothesis testing procedures. The application of this technique to MMH
investigations allows identification of the lift characteristics that domi
nate the variability of task demands, hence aiding in the design and assess
ment of ergonomic solutions.