Abstract: BACKGROUND: Human plantar pressure can reflect the health status of the lower limbs and even the whole body, which is an important basis for gait analysis, and body mass index is an important influencing factor.
OBJECTIVE: To investigate the effect of body mass index on plantar pressure.
METHODS: Twenty young college students from Xuzhou Medical University, including 10 males and 10 females aged 19-21 years, were selected as test subjects and divided into three groups according to the body mass index value: overweight group (body mass index > 25 kg/m2, n=3), lean group (body mass index < 18 kg/m2, n=4), and normal group (body mass index 18-25 kg/m2, n=13). A natural walking gait test was carried out on the three groups of subjects with a Zebris pressure distribution measurement plate to obtain the complete gait cycle parameters. The time proportion of support time phase, peak pressure, time to peak force, peak force and impulse volume were analyzed and the correlation between each parameter and the body mass index was analyzed by Person analysis.
RESULTS AND CONCLUSION: (1) Compared with the other two groups, the time proportion of support time phase of subjects in the overweight group was relatively small, while the time proportion in the foot heel contact period and forefoot extension period was relatively large. There was a positive correlation of the time proportion of the foot heel contact period and forefoot extension period with body mass index, while there was a negative correlation between the time proportion of the arch support period and body mass index. (2) The peak pressure of the left arch and palm of the foot of the subjects of the overweight group was higher than that of the normal group, and the peak pressure of the left and right palm of the foot of the lean group was lower than that of the normal group. The peak pressure was positively correlated with the body mass index during the foot heel contact period. There was a significant positive correlation between the peak pressure of the left foot and body mass index during the arch support period as well as the peak pressure of both feet and body mass index during the forefoot extension period. (3) Plantar peak force time in the order of the gait cycle in increasing order: heel < arch < metatarsal < toe. In the foot heel contact period, the time of peak force was negatively correlated with body mass index, but they were positively correlated with each other in the forefoot extension period. In the arch support period, the time of peak force of the left arch was significantly positively correlated with body mass index. (4) Plantar peak force was mainly expressed as medial heel > toe/middle 2-4 metatarsal > lateral heel > medial and lateral metatarsal > arch; medial heel peak force was the largest, and the arch peak force was the smallest. Except for the toe of the left foot, there was a significant positive correlation between peak force and body mass index. (5) The maximum ground impulse of the lean group and the overweight group was in the foot heel contact stage, the minimum ground impulse was in the forefoot extension period, and the minimum ground impulse of the arch was in the normal group. There was a significant positive correlation between ground impulse and body mass index at different periods. (6) The results show that young people should control their body mass index, wear appropriate shoes, protect their feet and ankles, and prevent the occurrence of flat feet.

Key words: plantar pressure, body mass index, gait analysis, significance of differences, peak force, impulse, pressure