Fig 2. Illustration of the process of detecting MTC.

MTC is obtained from the trajectory of the reflective marker attached to the first metatarsal in the vertical direction (MT1_Z). The average MT1_Z during the three-second standing is set as the baseline position of the toe. This average value is subtracted from the entire original MT1_Z profile and the resulting profile is labeled as MT1_Znorm. Each gait cycle of one leg is defined as the period from a heel-strike (HS) to the subsequent HS of the other leg. (The figure shows the example of one gait cycle defined to calculate MTC of the dominant foot.) The MT1_Znorm during one gait cycle exhibits two peaks (green circles). MTC is defined as the lowest MT1_Znorm between these two peaks (red circle).