The internal stress of the human foot enables efficient parametric evaluation of structural and functional impairments associated with foot deformities, such as hallux valgus (HV). However, the status of the internal stress of such a deformed foot remains insufficiently addressed due to the difficulties and limitations of experimental approaches. This study, using finite element (FE) methodology, investigated the influence of severe HV deformity on the metatarsal stress and the metatarsophalangeal (MTP) joint loading during balanced standing. FE models of a normal foot and a severe HV were constructed and validated. Each FE model involves 28 bones and various cartilaginous structures, ligaments, and plantar fascia, as well as encapsulated soft tissue. All the materials except for the encapsulated soft tissue were considered isotropic and linearly elastic, while the encapsulated soft tissue was set as nonlinear hyperelastic. Hexahedral elements were assigned to the solid parts of bones, cartilage, and the encapsulated soft tissue. Link elements were assigned to ligaments and plantar fascia. A plate was created for simulating ground support. A vertical force of a half-body weight was applied on the bottom of the plate for simulating balanced standing loading. The superior surfaces of the encapsulated soft tissue, distal tibia, and distal fibula were fixed. Stress distribution in the metatarsals, contact pressure, and force at the MTP joints were comparatively analysed. Compared to the normal foot, the HV foot showed higher stress concentration in the metatarsals but lower magnitude of MTP joint loading. In addition, the region with high contact pressure at the first MTP joint shifted medially in the HV foot. Knowledge of this study indicates that patients with severe HV deformity are at higher risk of metatarsal injuries and functional impairment of the MTP joints while weight bearing.

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BACKGROUND AND OBJECTIVE: The aim of this study was to explore the effectiveness of arch support functional insoles to prevent metatarsalgia. METHOD: Twenty-five healthy females participated in the study. A Vicon motion capture system was used to collect kinematics data of the lower limb. An AMTI force plate was used to record the vertical ground reaction force (GRF), and the Novel Pedar-X System was used to measure foot pressure while subjects wore normal insoles or functional insoles with an arch support during walking and jogging. RESULTS: With the arch support functional insoles, the first metatarsal (FM) region's contact area was increased and the peak pressure and time-pressure integral of the FM and second and third metatarsal (SATM) were areas decreased. This suggests a lower risk of longitude stress injuries in these areas. The ankle dorsiflexion angle of jogging with the 'arch support functional insoles' (RF) and walking with the 'arch support functional insoles' (WF) were significantly increased at initial contact and the knee and hip flexion angle of RF and WF were reduced. The peak hip extension angle of WF and RF also declined. The vertical loading rate of RF was lower, which would be beneficial in reducing the risk of lower limb injuries during jogging. CONCLUSIONS: The results demonstrate that arch support functional insoles can be used effectively to prevent and decrease pain and promote a suitable weight-bearing pattern in the foot for promoting the health of young females.

Most of the previous studies have been focused on the upper limb biomechanical characteristic in the clear stroke among different level badminton players, but research on the lower limb is limited. The aim of this study is to explore the lower limb kinematics and foot pressure in the backcourt forehand clear stroke among badminton players to give theoretical reference in teaching and answer the questions occurring in the process of learning the actions. Ten professional badminton players (PP) and ten amateur players (AP) were recruited in this study. Plantar pressure analyses indicated that both the PP and the AP were in contact with the ground over the forefoot without the midfoot and heel. The work suggests that when designing professional badminton sports shoes, the designers should focus on strengthening footwear resistance in the metatarsal and forefoot area, especially the first metatarsal area, to meet the requirement of the movement demand and take the badminton movement characteristics in different regions of the design. The peak ankle dorsiflexion, eversion, and internal rotation angle levels of the AP are lower than those of the PP. It is important for the AP group to enhance their ankle strength to prevent injury and improve performance.

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