抄録
Objective: This study aimed to examine sex-specific immediate effects of localized plantar stimulation delivered through socks （pad thickness 1–3 mm） on spatiotemporal gait parameters and sagittal-plane ankle-related foot angles during level walking at a self-selected comfortable speed.
Methods: Twenty-six healthy adults （15 men, 11 women; age 21.4 ± 0.9 years） participated in a within-subject, randomized-condition study. Participants performed 5-m straight level walking at a comfortable speed while wearing a wearable gait analysis system（Physilog6S ®,Gait Up, Switzerland; 128 Hz） secured on the dorsum of both feet. Four conditions were tested: socks only（ baseline）, socks + 1-mm pad,socks + 2-mm pad, and socks + 3-mm pad. Pads（PORON; Shore A 50） were standardized and attached externally at three sites: proximal to the fourth metatarsal head, under the medial cuneiform, and proximal to the fifth metatarsal head. Condition order was randomized. After 5-min familiarization, three trials were recorded and averaged. Outcomes were gait speed, stride length, strike angle（ foot-to-floor angle at heel strike）, and lift-off angle（foot-to-floor angle at toe-off）; analyses used left-foot values. Within each sex, all pairwise comparisons were performed using paired t-tests with Holm correction; baseline sex differences were assessed using Welch’s t-tests（ p < 0.05）.
Results: No significant differences were found between conditions in gait speed or stride length in either sex. For men, neither strike angle（socks: 17.1 ± 2.6°, 1 mm: 17.3 ± 2.6°, 2 mm: 16.8 ± 3.2°, 3 mm: 17.0 ± 2.9°） nor lift-off angle（ socks: −63.3 ± 7.6°, 1 mm: −62.6 ±7.4°, 2 mm: −64.1 ± 7.1°, 3 mm: −64.5 ± 6.4°） differed significantly across conditions. For women, strike angle differed only between the 1-mm and 2-mm conditions（ p = 0.042, Cohen’s dz = 1.02）, with a larger angle in the 2-mm condition（ socks: 17.0 ± 3.3°, 1 mm: 16.2 ± 2.1°,2 mm: 17.4 ± 2.6°, 3 mm: 16.3 ± 3.7°）. Lift-off angle did not differ across conditions in women（ socks: −67.3 ± 4.4°, 1 mm: −66.8 ± 3.7°,2 mm: −67.0 ± 5.3°, 3 mm: −65.1 ± 3.3°）. No significant sex differences were observed for any outcome in the baseline condition.
Conclusions: Localized plantar stimulation through socks using 1–3 mm pads produced no immediate changes in gait speed or stride length during comfortable-speed level walking in healthy young adults. A condition-specific effect was observed only for women’s strike angle between the 1-mm and 2-mm pads, indicating that the overall impact of this intervention was limited and outcome-specific. Further studies incorporating plantar-pressure assessment and three-dimensional kinematics with larger sample sizes are warranted to clarify sex-dependent gait adaptations to subtle plantar stimulation.
https://ror.org/01rkrzs64 
