Average torsion axis location of athletic movements: subject specific or movement specific?

Foot torsion angles have previously been studied for different athletic movements. Sport shoes often contain a torsion element even though the location of the rotation axis of the foot is unknown. Therefore, the purpose of this study was to quantify the torsion axis location and determine if the location is influenced by the movement or the subject. The torsion axis location was calculated using a modified finite helical axis approach, which allowed the calculation of the rotation axis between the forefoot and the rearfoot without the influence of forefoot flexion. The torsion axis location during the lateral jab was 9.72 mm below and 26.96 mm lateral to a marker located at the posterior, central heel, whereas the shuffle cut resulted in an axis location of 9.59 mm below and 26.19 mm lateral to the reference marker. There was no significant difference for the average axis location between movements. There was, however, a significant difference for the location between subjects, indicating a subject specificity of the torsion axis. The results of the current study are the first to quantify the torsion axis location of the human foot during athletic movements.