Despite its use in biomechanics research, there exists no standardized method for implementing a residual analysis to define the optimum cutoff frequency (OCF) of low-pass digital filters. Given the potential for this processing to have an impact on results, an objective routine is necessary for consistent data treatment between investigations and laboratories. Therefore, the goal of this study was to formalize an objective routine to implement a residual analysis, and examine whether it could be applied to kinetic signals. METHODS - Part I: The following parameters were hypothesized to effect the OCF determined through residual analysis: (i) linearity criterion magnitude, (ii) frequency axis resolution and (iii) range of cutoff frequencies included in the analysis. Part II: Two existing datasets were used to evaluate the objective routine that was developed. For each study, four dependent measures were calculated from ground reaction force data, including: (i) peak force, (ii) time to peak force, (iii) rate of force development and (iv) impulse. To examine the influence of using a digital Butterworth filter with OCF, each measure was compared to both the raw signal and a commonly applied cutoff frequency of 20 Hz. RESULTS - The objective routine developed was found to be most sensitive to the range of frequencies included in the analysis. In Part II, both the F-20 and OCF filtering conditions had minimal impact on all force-time dependent measures, except for rate of force development. IMPLICATIONS - Residual analysis may not be appropriate for selecting an OCF when filtering kinetic signals.
Listed In: Biomechanical Engineering, Biomechanics, Gait, Orthopedic Research, Sports Science