Author(s): HOSONO, S., KEIJI, K., Institution: TOIN UNIVERSITY OF YOKOHAMA, Country: JAPAN, Abstract-ID: 1324

INTRODUCTION:
The structure and function of the human foot are critical for maintaining balance and generating propulsion during physical activities. Therefore, improving foot structure and function is essential for injury prevention and the enhancement of athletic performance. Several studies have investigated the effects of training on enhancing foot structure and function. For example, foot exercise training has been reported to alter arch morphology (Holowka et al. 2018) and enhance force-generating capacity (Koyama & Yamauchi, 2023) as well as sensory function (Maemichi et al. 2024). However, evidence suggests that these training effects may be influenced by footwear use. Specifically, individuals who habitually wear footwear that closely mimics barefoot conditions exhibit higher and stiffer foot arches and larger cross-sectional areas of the intrinsic foot muscles compared to those who habitually wear conventional shoes (Holowka et al. 2018). Therefore, differences in training outcomes may arise depending on whether foot-strengthening exercises are performed barefoot or while wearing shoes. Nevertheless, no studies have directly compared the effects of foot training on muscle strength under barefoot and shod conditions. This study investigated how footwear use during training influences foot structure, muscle strength, and sensory function.
METHODS:
Healthy adults (20–50 years) participated. Foot length, arch height, toe flexor strength, and sensory perception were measured. Subjects were assigned to a barefoot training group (BARE), a shod training group (SHOD), or a control group (CON), matched for age, height, weight, and measurement variables. Training groups followed a foot and lower limb strengthening program (Koyama & Yamauchi, 2023) for 60 minutes, twice a week, for eight weeks. Measurements were taken once every two weeks. Foot dimensions were measured with a ruler in sitting and standing positions. Toe flexor strength was assessed with a dynamometer, and sensory perception with a Semmes–Weinstein monofilament at seven plantar and two dorsal sites. To control for body composition, arch height was normalized by foot length and toe flexor strength by body weight. Data were expressed as percentage changes from baseline.
RESULTS:
After eight weeks, no significant differences were found between BARE and SHOD in most variables, except seated arch parameters. Neither group showed significant changes in arch-related variables or sensory perception. However, BARE significantly increased toe flexor strength at weeks 4, 6, and 8 from baseline and at weeks 6 and 8 from week 2. SHOD showed significant increases at weeks 4, 6, and 8 from baseline. In the CON, no significant changes were observed in any of the measured variables during the training period.
CONCLUSION:
Training effects were similar between conditions, but barefoot training appeared more effective for enhancing toe flexor strength.