Introduction to Sports Biomechanics: Analysing Human Movement ...

Figure 4.9 Residual analysis of filtered data.
It is often necessary to use a different smoothing parameter or cut-off frequency for
the coordinates of the different points recorded. This is particularly necessary when
the frequency spectra for the various points are different.
Finally, you should note that no automatic noise-removal algorithm will always be
successful, and that the smoothness of the processed data should always be checked.
Body segment inertia parameters
QUANTITATIVE ANALYSIS OF MOVEMENT
Various body segment inertia parameters are used in movement analysis. The mass of
each body segment and the segment centre of mass position are used in calculating the
position of the whole body centre of mass (see Chapter 5). These values, and segment
moments of inertia, are used in calculations of net joint forces and moments using the
method of inverse dynamics. The most accurate and valid values available for these
inertia parameters should obviously be used. Ideally, they should be obtained from, or
scaled to, the sports performer being studied. The values of body segment parameters
used in sports biomechanics have been obtained from cadavers and from living persons,
including measurements of the performers being filmed.
Cadaver studies have provided very accurate segmental data. However, limited sample
sizes throw doubt on the extrapolation of these data to a general sports population.
They are also highly questionable because of the unrepresentative samples in respect of
sex, age and morphology. Problems also arise from the use of different dissection techniques
by different researchers, losses in tissue and body fluid during dissection and
degeneration associated with the state of health preceding death. Segment mass may be
expressed as a simple fraction of total body mass or, more accurately, in the form of a
137