Pressure distribution beneath the human foot

A descriptive study was undertaken to establish the 95 percentile limits (proposed normal reference range) for pressure beneath the hallux, metatarsal heads, and heel in a group of healthy adult subjects. A new force plate device capable of accurately measuring discrete areas of pressure beneath the human foot with high temporal and spatial resolution was used. The system is capable of accurately measuring plantar foot pressure during dynamic and static foot function. The results of this research are in close agreement with other published studies of plantar foot pressure measurement with comparable systems.

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.

Image-based midsole insert design and the material effects on heel plantar pressure distribution during simulated walking loads

The primary objective of this paper is to study the use of medical image-based finite element (FE) modelling in subjectspecific midsole design and optimisation for heel pressure reduction using a midsole plug under the calcaneus area (UCA). Plugs with different relative dimensions to the size of the calcaneus of the subject have been incorporated in the heel region of the midsole. The FE foot model was validated by comparing the numerically predicted plantar pressure with biomechanical tests conducted on the same subject. For each UCA midsole plug design, the effect of material properties and plug thicknesses on the plantar pressure distribution and peak pressure level during the heel strike phase of normal walking was systematically studied. The results showed that the UCA midsole insert could effectively modify the pressure distribution, and its effect is directly associated with the ratio of the plug dimension to the size of the calcaneus bone of the subject. A medium hardness plug with a size of 95% of the calcaneus has achieved the best performance for relieving the peak pressure in comparison with the pressure level for a solid midsole without a plug, whereas a smaller plug with a size of 65% of the calcaneus insert with a very soft material showed minimum beneficial effect for the pressure relief.

The pressure distribution along the stone column in soft clay when subjected to consolidation and foundation loading

The mechanism whereby the foundation loading is transmitted through stone the column (included in soft clay) has received less attention from researchers. This paper reports on some interesting findings obtained from a laboratory-based model study in respect of this issue. The stone column, included in the soft clay bed was subjected to foundation loading under drained conditions. The results show, probably for the first time, how the foundation loadings are transmitted through the column and indeed the existence of “negative skin friction” (a widely accepted phenomena in solid piles) in granular columns in soft clays.

The pressure distribution along stone columns in soft clay under consolidation and foundation loading

The mechanism whereby foundation loading is transmitted through the column has received little attention from researchers. This paper reports on some interesting findings obtained from a laboratory-based model study in respect of this issue. The model tests were carried out on samples of soft clay, 300 mm in diameter and 400 mm high. The samples were reinforced with fully penetrating stone columns, of three different diameters, made of crushed basalt. Four pressure cells were located along each stone column. The 60 mm diameter footing used in the model was supported on a clay bed reinforced with a stone column and subjected to foundation loading under drained conditions. The results show that the dissipation of excess pore water pressure developed during the initial application of total stresses, when the foundation was subjected to no loading, generated considerable stresses within the column, and that this was directly attributable to the development of negative skin friction. The pressure distributions in the column during foundation loading showed some complex behaviour.

Ground reaction forces and plantar pressure distribution during occasional loaded gait

This study compared the ground reaction forces (GRF) and plantar pressures between unloaded and occasional loaded gait. The GRF and plantar pressures of 60 participants were recorded during unloaded gait and occasional loaded gait (wearing a backpack that raised their body mass index to 30); this load criterion was adopted because is considered potentially harmful in permanent loaded gait (obese people). The results indicate an overall increase (absolute values) of GRF and plantar pressures during occasional loaded gait (p < 0.05); also, higher normalized (by total weight) values in the medial midfoot and toes, and lower values in the lateral rearfoot region were observed. During loaded gait the magnitude of the vertical GRF (impact and thrust maximum) decreased and the shear forces increased more than did the proportion of the load (normalized values). These data suggest a different pattern of GRF and plantar pressure distribution during occasional loaded compared to unloaded gait.

Surrounding buildings and wind pressure distribution on a high-rise building

The effect of the surrounding lower buildings on the wind pressure distribution on a high-rise building is investigated by computational fluid dynamics (CFD). When B/H=0.1, it is found that the wind pressure on the windward side was reduced especially on the lower part, but for different layers of surrounding buildings, there was no great difference, which agrees with our previous wind tunnel experiment data. Then we changed the aspect ratio from 0.1 to 2, to represent different airflow regimes: skimming flow (SF), and wake interference (WI). It shows that the average Cp increases when B/H increases. For different air flow regimes, it is found that insignificant difference exists when the number of the building layers is more than 2. From the engineering point of view, it is sufficient to only include the first layer for natural ventilation design by using CFD simulation or wind tunnel experiment.

Pressure distribution on the frontal disk for turbulent flows in a radial diffuser

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The use of thermal manikin to evaluate interface pressure distribution

The use of a thermal buttocks manikin(1) was explored as a tool to standardize the evaluation of seat comfort. Thermal manikin buttocks were developed and calibrated thermally and anatomically to simulate the sensible heat transfer of a seated person and used to evaluate interface pressure distribution. In essence, the pressure maps of manikin buttocks with and without heating were compared to those of a seated person. The results of average pressure demonstrated that the thermal manikins have a better response in interface pressure measurement than manikins without heating.

The effect of standard and low-modulus cement augmentation on the stiffness, strength, and endplate pressure distribution in vertebroplasty

Vertebroplasty restores stiffness and strength of fractured vertebral bodies, but alters their stress transfer. This unwanted effect may be reduced by using more compliant cements. However, systematic experimental comparison of structural properties between standard and low-modulus augmentation needs to be done. This study investigated how standard and low-modulus cement augmentation affects apparent stiffness, strength, and endplate pressure distribution of vertebral body sections.