Gait data processing

Temporal and spatial gait parameters were obtained. To reduce the inter-individual variation due to body size, the speed (m/s), stride length (cm), and step width (cm) were divided by height (cm) and designated as n speed, n stride length, and n step width, respectively [26].

For the kinematic data analysis, three representative strides from five separate trials were selected based on the waveforms of the range of motion curve, excluding the maximum and minimum curves. Plantar pressure variables of the dominant foot matching the three representative strides were analyzed. To assess the intersegmental foot position (hindfoot relative to the tibia, forefoot to the hindfoot, and hallux to the forefoot) during the gait cycle, we divided the entire gait cycle into 100 points with a 1% interval and collected the intersegmental angles (ISAs) at each time point. The calculated parameters were as follows: (1) hindfoot relative to the tibia: dorsiflexion/plantarflexion (sagittal plane), pronation/supination (coronal plane), and internal/external rotation (transverse plane); (2) forefoot relative to the hindfoot: dorsiflexion/plantarflexion (sagittal plane), pronation/supination (coronal plane), and abduction/adduction (transverse plane); and (3) hallux relative to the forefoot: dorsiflexion/plantarflexion (sagittal plane) and valgus/varus (transverse plane). The data of the intersegmental positions of the first and fifth rays were recorded, but are not reported in the present study.

To compare the position of the foot and ankle segments between groups or states, the ISAs (position) in the middle of eight phases of gait (initial contact (IC) [0–2%], load response (LR) [6–8%], mid-stance (MS) [21–23%], terminal stance (TS) [40–42%], pre-swing (PSw) [55–57%], initial swing (ISw) [67–69%], mid-swing (MSw) [80–82%], and terminal-swing (TSw) [93–95%]) were measured, and the change in intersegmental angle (motion) between phases was calculated as previously described [24, 27, 28].