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Figure 4. Calculation
of stride length, stride offset, and lead foot angle at the moment
of stride foot contact. Distance 'A' measures the length from centre
of the trailing ankle to the centre of the lead ankle. Distance 'B'
measures the distance from the leading edge of the pitching rubber
to the centre of the lead ankle. Distance 'C' measures the offset
of the centre of the lead ankle from a line drawn from the centre
of the trailing ankle through to the centre of the target (home plate).
Positive values being on the non-throwing arm, or 'open' side with
our example showing a positive value. Angle Theta (Ө)
measures the angle made between the long axis of the leading foot
and a parallel line drawn from the centre of the trailing ankle to
the centre of the pitching rubber. In this case Theta measures approximately
9° toward the 'open' side. Fleisig's (1994) PhD thesis gave normative
values for each of these variables as follows: A: 75% of height, ±
SD: 4%; B: 87% ± 5%; C: 0.4cm ± 8.3cm; Theta: 15° ± 10°. |