Article

Inverse dynamics analyses are commonly used to understand movement patterns in
all forms of gait. The aim of this study was to determine the effect of digital
filtering procedures on the knee joint moments calculated during sprinting as an
example of the possible influence of data analysis processes on interpretation of
movement patterns. Data were obtained from three highly trained sprinters who
completed a series of 30 m sprints. Ten different combinations of cut-off
frequency were applied to the two-dimensional kinematic and kinetic input data
with the kinetic cut-off frequency set equal to or higher than the kinematic
cut-off frequency. When using the commonly adopted practice of filtering the
kinetic data with a higher cut-off frequency than the kinematic data, exaggerated
fluctuations in the knee joint moment existed soon after contact. In extreme
cases, the knee moved between flexor, extensor and flexor dominance in less than
33 ms and through ranges exceeding 500 Nm. During an inverse dynamics analysis of
locomotion, mismatched cut-off frequencies will likely affect the calculated
joint moments if the cut-off frequency applied to the kinematic data is less than
the true frequency content, particularly during impact phases. In the example of
sprinting, exaggerated fluctuations in the knee joint moment appear to be data
processing artefact rather than genuine characteristics of the joint kinetics.
When the cut-off frequencies, and thus the frequency content of all input data,
are matched, the fluctuations after contact are minimal and such a procedure is
suggested for inverse dynamics analyses of gait.
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Langue : ANGLAIS