Figure 1.

Standing protocol and feet and electrode positioning. (A) Schematic illustration showing the procedure considered to measure feet length. The midpoint between the tip of left and right calcaneus bones was considered as the origin of the reference system for center of pressure (CoP) and foot length measurements. The target value, corresponding to 65% of the foot length projected on the anterior-posterior axis (AP_axis), was calculated and then considered for the normalization task shown in (B). In such task, participants were asked to keep their CoP position in the AP_axis (black line) within 10% (±5%) of the target value (thick, gray line). (C) The positioning of electrode arrays is shown for the tibialis anterior muscle (left), for the medial and lateral gastrocnemius heads and for the soleus medial and lateral portions (right).