J. S. Li

Computer simulation of stress distribution in the metatarsals at different inversion landing angles using the finite element method

Metatarsal fracture is one of the most common foot injuries, particularly in athletes and soldiers, and is often associated with landing in inversion. An improved understanding of deformation of the metatarsals under inversion landing conditions is essential in the diagnosis and prevention of metatarsal injuries. In this work, a detailed three-dimensional (3D) finite element foot model was developed to investigate the effect of inversion positions on stress distribution and concentration within the metatarsals. The predicted plantar pressure distribution showed good agreement with data from controlled biomechanical tests. The deformation and stresses of the metatarsals during landing at different inversion angles (normal landing, 10 degree inversion and 20 degree inversion angles) were comparatively studied. The results showed that in the lateral metatarsals stress increased while in the medial metatarsals stress decreased with the angle of inversion. The peak stress point was found to be near the proximal part of the fifth metatarsal, which corresponds with reported clinical observations of metatarsal injuries.

Heel skin stiffness effect on the hind foot biomechanics during heel strike

Background: The human heel pad is a complex biological structure consisting of the fat pad and the skin. The mechanical properties of the skin layer are of significant importance to the load‐bearing function of the heel pad and human locomotion. The condition of the heel skin is also directly associated with some medical conditions such as heel ulcers that may become a site for the skin breakdown, which is the most common precursor to lower extremity amputation among persons with diabetes. It is essential to develop a detailed understanding of the properties of the heel skin layer and its effect on hind foot biomechanics during heel strike.

BIOMECHANICAL EFFECTS OF FOAM INSERTS ON FOREFOOT LOAD DURING THE HIGH-HEELED GAIT: A PILOT STUDY

This pilot study analyzed the loading on the medial forefoot (MF) region during walking in high-heel shoes. Eight healthy female volunteers have participated in this study with the heel height varied from 0 cm (flat), 4.5 cm (low), and 8.5 cm (high). The results showed that the load on MF increased with the heel height and the magnitude of the load could be effectively reduced by using foam inserts. Comparative studies of foams with different hardness and thicknesses showed that thicker soft foams had a significant advantage over thiner hard foams (P < 0.05) in reducing the peak pressures. An optimum condition with a thick soft insert could reduce MF pressure by 26%, impact force by 27%, and force time integral by 20% when compared to the condition without insert.

Effects of different unstable sole construction on kinematics and muscle activity of lower limb

Unstable sole construction can change biomechanics of lower extremity as highlighted by some previous studies, which could potentially help developing special training or rehabilitation schemes. In this study, unstable elements are fixed in heel and forefoot zone to exert unstable perturbations, and the position changes (medial, neutral and lateral) of unstable elements in forefoot coronal plane are adjusted to analyze changes of lower extremity kinematics and muscle activities. Twenty-two healthy male subjects participated in the test, walking with control shoes and experimental shoes randomly under self-selected speed. Kinematics and surface electromyography measurements were carried out simultaneously. It is found that experimental shoes can lead to the reduction of knee abduction and internal rotation and hip internal rotation, with p<.05. Ankle inversion and internal rotation amplitude were also reduced, which are associated with significantly increased activation levels of muscles (TA-tibialis anterior, PL-peroneus longus, LG-lateral gastrocnemius) in order to compensate perturbations. It is suggested that a training equipment incorporating unstable elements would enhance postural control by adjusting lower extremity kinematics and reorganizing muscle activity. More research can be conducted to testify the feasibility of unstable shoes construction on human postural control and gait, even guide training regime design, injury prevention and rehabilitation.

PLANTAR PRESSURE DISTRIBUTION CHARACTER IN YOUNG FEMALE WITH MILD HALLUX VALGUS WEARING HIGH-HEELED SHOES

Young females with mild hallux valgus (HV) have been identified as having an increased risk of first ray deformation. Little is known, however, about the biomechanical changes that might contribute to this increased risk. The purpose of this study was to compare kinetics changes during walking for mild HV subjects with high-heel-height shoes. Twelve female subjects (six with mild HV and six controls) participated in this study with heel height varying from 0 cm (barefoot) to 4.5 cm. Compared to healthy controls, patients had significantly higher peak pressure on the big toe area during barefoot walking. When the heel height increased, loading was transferred to medial side of the forefoot, and the big toe area suffered more impact compared to barefoot in mild HV. This study also demonstrated that the center of pressure (COP) inclines to medial side alteration after high-heeled shoes wearing. These findings indicate that mild HV people should be discouraged from wearing high-heeled shoes.

Plantar pressure variation during jogging with different heel height

This paper presents the key testing and analysis results of an investigation on the effect of heel height on the plantar pressure over different foot areas in jogging. It is important in improving the understanding of jogging with high heels and damage/injury prevention. It can also potentially guide the development of suitable/adaptive exercise schemes in between daily activities with high heels. In this work, plantar pressure data were collected from 10 habituated healthy female subjects aged 21--25 years at their natural jogging speed with three different conditions: flat heeled shoes 0.8 cm, low heeled shoes 4.0 cm, and high heeled shoes 6.6 cm. Data analysis showed significantly differences in plantar pressure distribution associated with the heel heights with increased pressure in the first metatarsal region and decreased pressure in the lateral metatarsal and midfoot sections. However, there is no significant alteration of plantar pressure in the central area of the forefoot with jogging gait.

Plantar pressure distribution during high-heeled Latin dancing

The impact of high-heeled shoes on the human gait kinetic is an important research field. Most published studies have been focused on the effects of high-heeled shoes on normal walking, while works on more intensive locomotion such as dancing is very limited. The purpose of this work was to investigate the foot pressure distribution, impact force and impulse during Latin dancing with different heel heights. Biomechanical measurements were performed for typical dance steps on six professional dance athletes. The load of each sole zone was calculated and the significance of the heel height effect was determined with statistical analysis. The results indicate that increasing heel height could cause an increase of impact forces in the forefoot and a reduction in the heel region. The effect of the heel height in dancing is different from normal gait and the lateral metatarsal region was identified as the most intensely affected zone in dancing.

Characteristics of the Skeletal System of Bound Foot: A Case Study

The purpose of this study was to establish the character of skeletal system of bound foot with binding deformity. Medical images were taken with a slice distance of 1mm from CT equipment. 3D models of bound foot were developed using density segmentation techniques through Mimics software. The talocalcaneal angle, calcaneal-first metatarsal angle, talo-first metatarsal angle, hallux valgus angle, I-II inter-metatarsal angle, I-V inter-metatarsal angle, first cuneiform-metatarsal angle, the horizontal metatarsal angle and the length of five metatarsals were evaluated on the lateral and antero posterior view. The results showed that bound foot have great deformation on the second to fifth toe, forming the abnormal higher foot longitudinal arch. The potential formation process of foot deformity associated with the binding process and its influence on the daily life of the foot binding subjects is discussed.

A PILOT STUDY IN DIFFERENT UNSTABLE DESIGNS ON THE BIOMECHANICAL EFFECT OF GAIT CHARACTERISTICS

The purpose of this study was to compare kinematics and kinetics during walking for healthy subjects using unstable shoes with different designs. Ten subjects participated in this study, and foot biomechanical data during walking were quantified using motion analysis system and a force plate. Data were collected for unstable shoes condition after accommodation period of one week. With soft material added in the heel region, the peak impact force was effectively reduced when compared among similar shapes. In addition, the soft material added in the rocker bottom showed more to be in dorsiflexed position during the initial stance. The shoe with three rocker curves design reduced the contact area in the heel strike, which may result in increasing human body forward speed. Further studies shall be carried out after adapting to long periods of wearing unstable shoes.

Lower Limb Muscles SEMG Activity during High-Heeled Latin Dancing

aim of this study is to provide information about surface electromyography (SEMG) activity pattern in lower limb muscles during Latin dancing with different heel height shoes. SEMG signals from tibialis anterior, medial and lateral sides of gastrocnemius, soleus and biceps femoris of ten professional female dancers were recorded. All the muscles average EMG (aEMG) values except biceps femoris were significantly increased in heightened heel shoes comparing to wearing the flat heel height dancing (p<0.05). Differences were not found in both sides of gastrocnemius and soleus among low, medium and high heel. Tibialis anterior muscle was the most vulnerable part to the heel height increasing. While the heel height increased to 10cm, the aEMG data of tibialis anterior significantly higher than both 4.5cm and 7.5cm heel heights. The muscle activity variety induced by high-heeled shoes in specific dancing movement would be further clarified involving more kinetics and kinematic data of lower limb.