Relationship between foot placement and mediolateral ground reaction forces during running.

This study investigated the relationship between foot placement relative to midline and mediolateral ground reaction forces during running. Data from 40 runners seen over a period of 2 years in a running injury clinic were analysed. A linear regression analysis revealed no significant relationship between foot placement and peak mediolateral values. Significance was found between foot placement and impulse, indicating that as the foot became more crossed over the lateral contribution to the total impulse increased (and vice versa). However, only 15% of the total variance in this model was accounted for. Despite these weak findings, subjects in the extreme range of foot placement (both wide-base and cross-over) appeared to exhibit stronger influences on mediolateral impulses. Therefore in the second phase of this study a symptom-free runner was tested while running with a 5-cm cross-over and wide-base gait, along with a neutral gait pattern. In the cross-over gait the contribution of the lateral impulse to the total impulse was 97%. Similar findings were noted with the medial contribution in the wide-based gait. Finally, the cross-over gait resembled the mediolateral force pattern observed during a 45-degree cut to the right (but exhibited lesser magnitudes), while the wide-base gait was similar to a cut to the left.