The 'impact' of force filtering cut-off frequency on the peak knee abduction moment during landing: artefact or 'artifiction'?
BACKGROUND
Joint moments computed using inverse dynamic techniques are important estimators of net joint loads. Joints moments computed from marker position and ground reaction force data filtered using different cut-off frequencies may capture changes in moment magnitudes at a single joint that exceed normal physiological response. Peak external knee abduction moment (KAM) generated during landing (ie, the drop vertical jump, DVJ) predicts anterior cruciate ligament injury risk using marker and force data filtered at different cut-off frequencies. The purpose of the current investigation was to determine the effects of using the same low cut-off frequencies versus different cut-off frequencies on joint moment magnitudes to evaluate if artificial smoothing attenuates actual resultant joint loads related to injury risk.


METHODS
Twenty-two female, high school volleyball players performed three maximum DVJs in a laboratory setting. The average peak KAM was computed for each knee using marker and force data filtered with the same low cut-off frequencies and different cut-off frequencies.


RESULTS
Peak KAMs were significantly larger using different cut-off frequencies. The order of athletes ranked based on the magnitude of their peak KAMs did not significantly change across all filtering cut-off frequencies.


CONCLUSIONS
The magnitude of peak KAM may differ when the same low or different higher cut-off frequencies are used to filter marker and ground reaction forces (GRF) data collected using standard motion capture equipment. It is not clear to what extent the decrease in peak KAM reported when the same low cut-off frequencies were used was solely due to attenuation of the GRF signal.
Sports Health and Performance Institute, The Ohio State University, Columbus, Ohio, USA.
Benjamin D
BD
Roewer
Kevin R
KR
Ford
Gregory D
GD
Myer
Timothy E
TE
Hewett
D000293:Adolescent; D000704:Analysis of Variance; D016477:Artifacts; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D054798:Volleyball / Q000502:physiology*