A model for the perception of surface pressure on human foot

The psychophysical relationship between the magnitude of pressure on thirteen test locations of twenty healthy subjects' feet with four probe areas at three indentation speeds and the corresponding perceived sensations were analyzed. The dependency of pressure pain thresholds (PPT) on area, A, and speed, v, can be mathematically modeled in the form, PPT(i)?=?[a(i)?+?bLn(v)]A(β)i?=?1,2…13 where β and b are constants and are dependent on location and gender, and a(i) is a constant highly correlated with foot tissue stiffness. The relationship between the sensory intensity to pressure magnitude appears to follow a modified Stevens' power law with power exponents less than 1.0 and consistent across the 13 test locations with a mean of 0.82 and a range from 0.67 to 0.98. This particular model helps to understand the sensation of pressure threshold and its impact in the design of consumer products.     

Pressure thresholds and stiffness on the plantar surface of the human foot

Abstract

A methodology to assess Pressure Discomfort Thresholds (PDT), Pressure Pain Thresholds (PPT) and tissue stiffness on the plantar surface of the foot was developed. Ten male and 10 female participants volunteered for the study. Foot landmarks were used to create a standardised grid-type template of 95 points. For each test point, PPT and PDT values were obtained, and stiffness was calculated for each of the 20 participants. Cluster analyses were performed to determine the regions of similarity for the three dependent variables, PPT, PDT and stiffness. Moran’s-I-index was used to determine the spatial auto correlations. The use of k-means clustering showed five distinct clusters while the three dependent variables showed strong correlations to each other. Morisita’s similarity index was used to check the similarity of the grid among all participants. Both male and female participants showed a Morisita’s index greater than 0.7 confirming the reliability of the foot template.

Practitioner Summary: Pressure Discomfort thresholds (PPT), Pressure pain thresholds (PPT) and tissue stiffness were evaluated at 95 points on the plantar surface of the foot. The PPT and related PDT map are useful to design the footbeds of shoes. Based on the data collected, five distinct clusters of locations were identified.     

Load distribution to minimise pressure-related pain on foot: a model

The optimal force distribution to minimise pain or discomfort at the foot–shoe interface is still not known. Most shoe-related products attempt to distribute the load uniformly without much consideration to the bony and soft tissue regions. An experiment was conducted to first determine the pressure pain threshold (PPT) and tissue deformation on the plantar surface of the foot. Circular probes of areas 0.5, 1.0 and 2.0 cm² at indentation speeds of 0.5, 1 and 2 mm/s showed that PPT depends on the location stimulated, area of stimulation and the indentation speed. The results also showed that tissue stiffness is quite low for small deformations ( < 4 mm), but significantly higher at large deformations (>4 mm). The stiffness at the larger deformation region was positively correlated with PPT (r = 0.63, p < 0.001). The data were further used to develop a model with PPT, deformation and stimulated area.

Practitioner Summary: Pressure at which there is an onset of pain is higher when a larger area of soft tissue is stimulated. Bony areas may be better suited to bear load on smaller areas to minimise pressure-related pain. Thus, manipulating supporting surface stiffness and surface contours can help minimise pain.     

Professional footwear evaluation for clinical nurses

Epidemiological investigations indicate that nursing professionals experience a higher prevalence of musculoskeletal disorders (MSDs) than most other occupational groups. Most nursing activities require standing and walking for prolonged periods. Such job requirements may contribute to MSD problems in the lower extremities. Thus, wearing comfortable nursing shoes is essential to reduce the lower-extremity discomfort for clinical nurses. The objectives of this study are: (1) to evaluate three brands of commercially available nursing footwear and identify the important shoe features for adequate shoe support during nursing activities, and (2) to assess the effect of wearing compression hosiery by measuring the biomechanical, physiological, and psychophysical responses of test participants. The method of this study involved two phases. First, field observations were conducted to collect job demand data, including walking speed, and the ratios of walking, standing, and sitting. Second, an experiment was conducted to evaluate the functions of professional nursing footwear and examine the influence of compression hosiery on lower extremity discomfort relief. Measurements included electromyography (EMG) of the lower leg, joint range of motion (ROM) in the lower extremity, foot pressure, ground reaction force (GRF), and subjective discomfort ratings for the lower body and feet. Summarizing the findings of this study, comfortable footwear for nursing professionals should emphasize a footbed with arch support outside with 1.5 cm thickness of EVA materials in the metatarsal zone and heel height between 1.8 and 3.6 cm; this can minimize foot pressure distribution, impact force, and increase shin and ankle comfort. In addition, wearing compression hosiery is recommended to alleviate lower body and foot discomfort for clinical nurses.     

Musculoskeletal disorders,foot health and footwear choice in occupations involving prolonged standing

Occupations that involve prolonged periods of standing and maintaining an upright posture are associated with an increased risk of work-related musculoskeletal disorders (WMSD), particularly of the lower back and lower extremities. Identifying factors that impact WMSD is therefore important, but the foot and footwear have been largely ignored to date. Therefore, this study aimed to assess the prevalence of WMSD of the lower back and lower extremity with emphasis on foot health and the impact of footwear. A cross-sectional questionnaire was completed by 147 surgical workers who were standing for long periods in their working day. It assessed job demands, individual characteristics, WMSD prevalence, psychosocial factors and footwear, with a multivariate analysis to identify relationships between variables. Results found the low back was the most predominant area of WMSD (71%), but the foot had the second highest prevalence (55%). The plantar foot surface was the main region of foot pain with everyone that experienced foot pain reporting it under the heel, ball of foot or arch region. Footwear was recognised as an influencing factor on WMSD by the participants as well as by the multivariate analysis, highlighting the importance of exploring footwear to reduce WMSD. Footwear comfort, footwear fit, footwear choice and the provision of footwear by employers were all identified as important factors to consider in relation to WMSD and foot health.Relevance to industryFootwear is related to WMSD which are seen in the majority of workers undertaking prolonged standing. Employers of these workers and footwear suppliers should consider footwear comfort, particularly its fit and individual preference for footwear characteristics including underfoot cushioning and support. This should also include consideration of the range of footwear available and how it is selected by workers.     

Association between objective and subjective measurements of comfort and discomfort in hand tools

In the current study, the relationship between objective measurements and subjective experienced comfort and discomfort in using handsaws was examined. Twelve carpenters evaluated five different handsaws. Objective measures of contact pressure (average pressure, pressure area and pressure-time (P-t) integral) in static and dynamic conditions, muscle activity (electromyography) of five muscles of the upper extremity, and productivity were obtained during a sawing task. Subjective comfort and discomfort were assessed using the comfort questionnaire for hand tools and a scale for local perceived discomfort (LPD). We did not find any relationship between muscle activity and comfort or discomfort. The P-t integral during the static measurement (beta=-0.24, p<0.01) was the best predictor of comfort and the pressure area during static measurement was the best predictor of LPD (beta=0.45, p<0.01). Additionally, productivity was highly correlated to comfort (beta=0.31, p<0.01) and discomfort (beta=-0.49, p<0.01).     

Effects of shoe inserts and heel height on foot pressure, impact force, and perceived comfort during walking

Studying the impact of high-heeled shoes on kinetic changes and perceived discomfort provides a basis to advance the design and minimize the adverse effects on the human musculoskeletal system. Previous studies demonstrated the effects of inserts on kinetics and perceived comfort in flat or running shoes. No study attempted to investigate the effectiveness of inserts in high heel shoes. The purpose of this study was to determine whether increasing heel height and the use of shoe inserts change foot pressure distribution, impact force, and perceived comfort during walking. Ten healthy females volunteered for the study. The heel heights were 1.0cm (flat), 5.1cm (low), and 7.6cm (high). The heel height effects were examined across five shoe-insert conditions of shoe only; heel cup, arch support, metatarsal pad, and total contact insert (TCI). The results indicated that increasing heel height increases impact force (p<0.01), medial forefoot pressure (p<0.01), and perceived discomfort (p<0.01) during walking. A heel cup insert for high-heeled shoes effectively reduced the heel pressure and impact force (p<0.01), an arch support insert reduced the medial forefoot pressure, and both improved footwear comfort (p<0.01). In particular, a TCI reduced heel pressure by 25% and medial forefoot pressure by 24%, attenuate the impact force by 33.2%, and offered higher perceived comfort when compared to the non-insert condition.     

3D foot prediction method for low cost scanning

With the rapid development of CAD/CAM technology and information technology, it is becoming possible to satisfy the quality, fit and comfort requirements of footwear design and manufacturing. In the footwear industry, although there are availability of design and manufacture technologies to fulfill the desired requirements, the current methods are very expensive. Cheap and accurate scanners are needed at the retail shop to acquire 3D foot shape information. This paper proposes a prediction method to model foot shapes through scaling a standard foot by using limited parameters. The accuracy of different number of parameters have been evaluated. Given that commercial expensive scanner accuracy range from 0.5 to 1 mm, in order to predict 3D foot shape to an accuracy of around 0.75 mm, foot outline, foot profile, two foot sections and standard foot model were required. The mean modeling errors were 0.76 mm and 0.75 mm of the right foot and left foot respectively. Results indicate that if more sections are used the modeling error decreases but this will increase the cost of the scanner and the computational complexity. This method provides a cost effective method to substitute expensive 3D foot scanners that usually use laser-based technology.Relevance to industry: This method provides the core algorithm for the development of low cost 3D foot scanners for footwear mass-customization. CCD cameras can be used to capture foot profile and outline, while fixed line laser can be used to obtain two key sections. This method reduces the need for expensive linear gears and optical systems.     

How do we fit underground coal mining work boots?

Abstract

Acceptable footwear fit, particularly width, is subjective and vaguely quantified. Proper shoe fit is important because it affects both comfort and the potential to prevent injury. Although mismatches between the feet of underground coal miners and their internal boot dimensions are known, no research has been undertaken to determine the impact of these mismatches on worker perceptions of fit, comfort and pain. This study aimed to quantitatively assess mining work boot fit relative to underground coal miners’ subjectively rated work boot fit and comfort, reported foot problems, lower limb pain and lower back pain in order to develop evidence-based work boot fit recommendations. Traditional footwear fitting methods based predominantly on foot length are insufficient for underground coal mining-specific footwear. Instead, fit at the heel, instep and forefoot must be considered when fitting underground coal mining work boots, in conjunction with the traditional length measurement.Practitioner summary: Underground coal miners report their work boots fit but are uncomfortable. This study assessed actual fit relative to perceived fit, comfort, foot problems, lower limb pain and lower back pain of 197 miners. Fit at the heel, instep and forefoot must be considered when fitting mining work boots.     

A reliable measure of footwear upper comfort enabled by an innovative sock equipped with textile pressure sensors

Footwear comfort is essential and pressure distribution on the foot was shown as a relevant objective measurement to assess it. However, asperities on the foot sides, especially the metatarsals and the instep, make its evaluation difficult with available equipment. Thus, a sock equipped with textile pressure sensors was designed. Results from the mechanical tests showed a high linearity of the sensor response under incremental loadings and allowed to determine the regression equation to convert voltage values into pressure measurements. The sensor response was also highly repeatable and the creep under constant loading was low. Pressure measurements on human feet associated with a perception questionnaire exhibited that significant relationships existed between pressure and comfort perceived on the first, the third and the fifth metatarsals and top of the instep.

Practitioner Summary: A sock equipped with textile sensors was validated for measuring the pressure on the foot top, medial and lateral sides to evaluate footwear comfort. This device may be relevant to help individuals with low sensitivity, such as children, elderly or neuropathic, to choose the shoes that fit the best.     

Human foot modeling towards footwear design

Comfort test of footwear is mainly based on subjective perception of the wearer and a large number of subjects are required to obtain a reliable result. Therefore, the subjective comfort test is expensive and time consuming. Although the foot size and shape of a subject can be obtained by using a three-dimensional (3D) foot scanner, it is still difficult to create foot motion animations of each subject suitable for computer simulation.In this paper, we propose a fast approach to model foot deformation and present its application in simulating interaction with footwear towards footwear design. The simulation determines deformation of foot and footwear models. It can also determine stress distribution in the footwear. Given an initial foot model and a captured foot motion, human foot animation is created first. Then, the footwear model is fitted to the foot to compute the deformation and stress in the footwear. In this article, the boundary element method (BEM) is adopted. We demonstrate the results by conducting simulation of a captured gait motion. Experimental results showed that the method can be used to simulate human gait motion, and can determine deformation of footwear.     

Effects of surface characteristics on the plantar shape of feet and subjects' perceived sensations

Orthotics and other types of shoe inserts are primarily designed to reduce injury and improve comfort. The interaction between the plantar surface of the foot and the load-bearing surface contributes to foot and surface deformations and hence to perceived comfort, discomfort or pain. The plantar shapes of 16 participants’ feet were captured when standing on three support surfaces that had different cushioning properties in the mid-foot region. Foot shape deformations were quantified using 3D laser scans. A questionnaire was used to evaluate the participant's perceptions of perceived shape and perceived feeling. The results showed that the structure in the mid-foot could change shape, independent of the rear-foot and forefoot regions. Participants were capable of identifying the shape changes with distinct preferences towards certain shapes. The cushioning properties of the mid-foot materials also have a direct influence on perceived feelings. This research has strong implications for the design and material selection of orthotics, insoles and footwear.     

The vibration of inclined backrests: perception and discomfort of vibration applied parallel to the back in the z-axis of the body

This study determined how backrest inclination and the frequency of vibration influence the perception and discomfort of vibration applied parallel to the back (vertical vibration when sitting upright, horizontal vibration when recumbent). Subjects experienced backrest vibration at frequencies in the range 2.5 to 25 Hz at vibration magnitudes up to 24 dB above threshold. Absolute thresholds, equivalent comfort contours, and the principal locations for feeling vibration were determined with four backrest inclinations: 0° (upright), 30°, 60° and 90° (recumbent). With all backrest inclinations, acceleration thresholds and equivalent comfort contours were similar and increased with increasing frequency at 6 dB per octave (i.e. velocity constant). It is concluded that backrest inclination has little effect on the frequency dependence of thresholds and equivalent comfort contours for vibration applied along the back, and that the W (d) frequency weighting in current standards is appropriate for evaluating z-axis vibration of the back at all backrest inclinations. STATEMENT OF RELEVANCE: To minimise the vibration discomfort of seated people, it is necessary to understand how discomfort varies with backrest inclination. It is concluded that the vibration on backrests can be measured using a pad between the backrest and the back, so that it reclines with the backrest, and the measured vibration evaluated without correcting for the backrest inclination.     

Shoe-last design innovation for better shoe fitting

Shoe-last, a 3D mould used for making footwear, influence the shape, size and fitting of footwear. Current shoe-last design software has focused mainly on reverse engineering of existing shoe-last and modification. Shoe-last designers have generally preferred to design the shoe-last manually due to limitations of design software. In order to solve these problems, a new software based on CATIA platform was developed. The shoe-last model is based on foot shape measurement data and foot biomechanics. Using the existing shoe-last design standards and the sections from existing shoe-lasts, design tables and relationship equations enables the design of shoe-last with different toe type, heel height and custom shoe-last. The design includes comfort and fit aspects as well as design aspect, therefore enables design of aesthetical comfortable shoes. Since the design can be modified instantaneously, the designers could visualize design changes leading to a reduction in shoe-last design cycle.     

Footwear bio-modelling: An industrial approach

There is a growing need within the footwear sector to customise the design of the last from which a specific footwear style is to be produced. This customisation is necessary for user comfort and health reasons, as the user needs to wear a suitable shoe. For this purpose, a relationship must be established between the user foot and the last with which the style will be made; up until now, no model has existed that integrates both elements. On the one hand, traditional customised footwear manufacturing techniques are based on purely artisanal procedures which make the process arduous and complex; on the other hand, geometric models proposed by different authors present the impossibility of implementing them in an industrial environment with limited resources for the acquisition of morphometric and structural data for the foot, apart from the fact that they do not prove to be sufficiently accurate given the non-similarity of the foot and last. In this paper, two interrelated geometric models are defined, the first, a bio-deformable foot model and the second, a deformable last model. The experiments completed show the goodness of the model, with it obtaining satisfactory results in terms of comfort, efficiency and precision, which make it viable for use in the sector.     

The vibration of inclined backrests: perception and discomfort of vibration applied parallel to the back in the z-axis of the body

This study determined how backrest inclination and the frequency of vibration influence the perception and discomfort of vibration applied parallel to the back (vertical vibration when sitting upright, horizontal vibration when recumbent). Subjects experienced backrest vibration at frequencies in the range 2.5 to 25 Hz at vibration magnitudes up to 24 dB above threshold. Absolute thresholds, equivalent comfort contours, and the principal locations for feeling vibration were determined with four backrest inclinations: 0° (upright), 30°, 60° and 90° (recumbent). With all backrest inclinations, acceleration thresholds and equivalent comfort contours were similar and increased with increasing frequency at 6 dB per octave (i.e. velocity constant). It is concluded that backrest inclination has little effect on the frequency dependence of thresholds and equivalent comfort contours for vibration applied along the back, and that the W _d frequency weighting in current standards is appropriate for evaluating z-axis vibration of the back at all backrest inclinations.

Statement of Relevance: To minimise the vibration discomfort of seated people, it is necessary to understand how discomfort varies with backrest inclination. It is concluded that the vibration on backrests can be measured using a pad between the backrest and the back, so that it reclines with the backrest, and the measured vibration evaluated without correcting for the backrest inclination.     

Use of SOMs for footwear comfort evaluation

Neural Computing and Applications - The comfort in footwear is essential because the foot is one of the structures of the human body that supports more weight. Moreover, consumers are demanding...     

基于Qt的鞋底摩擦力测控软件的设计

鞋底的止滑性直接影响着鞋子穿用时的舒适性和安全性,止滑性主要由摩擦系数来表示,在一定范围内,摩擦系数越大,止滑性越好。系统通过测量作用于鞋底的拉力和压力,求得摩擦系数,从而来判断各种鞋子的安全性能,因此对拉力和压力的测量显得十分重要。软件的设计基于Qt开发环境,在这个环境下开发的软件有很好的移植性,根据鞋底拉力测控系统的要求,将通过串行通信实时接收、处理、控制、显示、绘图、保存采集到的拉力和压力数据。最后在系统测试的基础上,验证了软件的正确性且测量精度高。     

Sizing and grading methods with consideration of footwear styles

Sizing and grading are very important in footwear production, directly influencing the fit and comfort of footwear. Currently, the footwear industry relies on traditional sizing and grading systems, which vary around the world. Modern measuring technologies, such as 3D scanning and modeling, are starting to be used in footwear mass production. Sizing and grading of footwear is closely related to the sizing and grading of foot. This study investigates the application of principal component analysis (PCA) in sizing and grading methods and the influence of footwear styles based on 3D foot shapes. Three sizing and grading methods were simulated and evaluated. Results show that, compared to the traditional method, the sizing and grading using PCA method provides less modeling error, hence will result in better fit. Furthermore, the prediction error for various footwear styles are significantly different and the footwear fit near the sole could be achieved easier than instep and ankle region. This indicates that various sizing and grading rules can be applied focusing on different footwear styles in order to develop optimal sizes.Relevance to industryThe proposed new sizing and grading method could benefit the footwear industry since it provides a better fit comparing to the traditional method. The influence of footwear styles on prediction error gives more detailed insights for manufacturers to further understand the fitting result when applying the different sizing and grading methods.     

Are arch‐conforming insoles a good fit for diabetic foot? Insole customized design by using finite element analysis

Plantar ulceration is one of the leading complications for diabetic patients. To reduce the risk of plantar ulceration, people with diabetic neuropathy often used custom insoles to offload high pressures from the metatarsal. However, the current custom arch‐conforming insoles, totally contact with the foot, could affect the flow of blood and produce adverse effects on foot ulcers. This study is aimed to propose novel custom insoles for diabetic foot and to make a comparison between the traditional insoles and the proposed one. The novel pressure‐relieving insole is a layered modular insole that includes eight layers of small cushions. The results showed that the current custom insoles would increase the insole volume and squeeze the space available for the foot, and then the constrictive box of the footwear could deteriorate the blood flow of the foot and produce adverse effects on foot ulcers. The novel insoles were found to reduce the peak pressure from 208.86 to 160.02 kPa. High pressure was not observed in the sensitive locations of diabetic foot in this study, and the novel insoles fit diabetic foot better.