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°.