The influence of footwear on foot motion during walking and running

There are evidences to suggest that wearing footwear constrains the natural barefoot motion during locomotion. Unlike prior studies that deduced foot motions from shoe sole displacement parameters, the aim of this study was to examine the effect of footwear motion on forefoot to rearfoot relative motion during walking and running. The use of a multi-segment foot model allowed accurate both shoe sole and foot motions (barefoot and shod) to be quantified. Two pairs of identical sandals with different midsole hardness were used. Ten healthy male subjects walked and ran in each of the shod condition.The results showed that for barefoot locomotion there was more eversion of the forefoot and it occurred faster than for shod locomotion. In this later condition, the range of eversion was reduced by 20% and the rate of eversion in late stance by 60% in comparison to the barefoot condition. The sole constrained both the torsional (eversion/inversion) and adduction range of motion of the foot. Interestingly, during the push-off phase of barefoot locomotion the rate and direction of forefoot torsion varied between individuals. However, most subjects displayed a forefoot inversion direction of motion while shod. Therefore, this experiment showed that the shoes not only restricted the natural motion of the barefoot but also appeared to impose a specific foot motion pattern on individuals during the push-off phase. These findings have implications for the matching of footwear design characteristics to individual natural foot function.     

Estimation of sex from the dimensions of foot, footprints, and shoe

This study intends to determine if the sex of an individual can be identified by foot lengths, shoe lengths, and/or footprints. For this purpose, foot length, foot breadth, and foot heel breadth of 506 subjects, comprising 253 females and 253 males ranging from 17.56 to 82.92 years of age, were taken. In addition, the footprints (length, breadth, and heel breadth) and footwear (length and breadth) of the same subjects were measured. Finally, the shoe size of the subjects was recorded. Univariate and multivariate discriminant function models were developed for sex allocations. Statistical analyses indicated that univariate models correctly assign approximately 67-94% of individuals to their correct sex groups. Among univariate models the most reliable measurement was shoe length. The results of multivariate models were better than those of univariate ones, with an approximately 82-96% correct assignment. The best multivariate model was comprised of four variables: foot length, shoe length, shoe breadth and shoe size. It could be suggested that these discriminant functions can provide useful clues to establish personal identity whenever complete or partial feet, footprints, or footwear are recovered.     

The structure of body measurements for the determination of shoe sizing for young Croatian men

The determination and promotion of the system of shoe sizing requires accurate knowledge of morphological properties of the foot and lower leg of the tested population. Similarly it is necessary to establish the occurrence and regional distribution of definite sizes in the tested population. Possible regional differences in morphological properties must not be ignored because it has been established by means of anthropological measuring that both foot dimensions and foot shapes differ between populations and within the same population. This has been proven by the investigation of body measures, carried out for the purpose of establishing a system of footwear sizes, which was executed on a randomly selected sample of 4,268 healthy and normally developed males aged 18-22. The investigation was carried out in 1993 on five locations each of which representing a definite region of the Republic of Croatia: Jastrebarsko (central), Koprivnica (northwestern), Pula (southwestern), Sinj (southern) and Pozega (northeastern). The measuring instrument was 31 foot and lower-leg sizes according to the existing ISO standards for footwear. Interregional differences are significant in all body measures. The role and the contribution of individual measures to these differences has been established by means of discriminatory analysis with regions as a priori defined samples. In order to constitute a convenient and purposeful standard for the footwear size system it is necessary to work out a database with referent values for the same system.     

Pain-related somatosensory evoked potentials following CO2 laser stimulation of foot in man

Since our previous study of pain somatosensory evoked potentials (SEPs) following CO₂ laser stimulation of the hand dorsum could not clarify whether the early cortical component NI was generated from the primary somatosensory cortex (SI) or the secondary somatosensory cortex (SII) or both, the scalp topography of SEPs following CO₂ laser stimulation of the foot dorsum was studied in 10 normal subjects and was compared with that of the hand pain SEPs and the conventional SEPs following electrical stimulation of the posterior tibial nerve recorded in 8 and 6 of the 10 subjects, respectively. Three components (N1, N2 and P2) were recorded for both foot and hand pain SEPs. N1 of the foot pain SEPs was maximal at the midline electrodes (Cz or CPz) in all data where that potential was recognized, but the potential field distribution was variable among subjects and even between two sides within the same subject. N1 of the hand pain SEPs was maximal at the contralateral central or midtemporal electrode. The scalp distribution of N2 and P2, however, was not different between the foot and hand pain SEPs. The mean peak latency of N1 following stimulation of foot and hand was found to be 191 msec and 150 msec, respectively, but there was no significant difference in the interpeak latency of Nl-N2 between foot and hand stimulation. It is therefore concluded that NI of the foot pain SEPs is generated mainly from the foot area of SI. The variable scalp distribution of the N7 component of the foot pain SEPs is likely due to an anatomical variability among subjects and even between sides.     

Comparison of hexahedral and tetrahedral elements in finite element analysis of the foot and footwear

Finite element analysis has been widely used in the field of foot and footwear biomechanics to determine plantar pressures as well as stresses and strains within soft tissue and footwear materials. When dealing with anatomical structures such as the foot, hexahedral mesh generation accounts for most of the model development time due to geometric complexities imposed by branching and embedded structures. Tetrahedral meshing, which can be more easily automated, has been the approach of choice to date in foot and footwear biomechanics. Here we use the nonlinear finite element program Abaqus (Simulia, Providence, RI) to examine the advantages and disadvantages of tetrahedral and hexahedral elements under compression and shear loading, material incompressibility, and frictional contact conditions, which are commonly seen in foot and footwear biomechanics. This study demonstrated that for a range of simulation conditions, hybrid hexahedral elements (Abaqus C3D8H) consistently performed well while hybrid linear tetrahedral elements (Abaqus C3D4H) performed poorly. On the other hand, enhanced quadratic tetrahedral elements with improved stress visualization (Abaqus C3D10I) performed as well as the hybrid hexahedral elements in terms of contact pressure and contact shear stress predictions. Although the enhanced quadratic tetrahedral element simulations were computationally expensive compared to hexahedral element simulations in both barefoot and footwear conditions, the enhanced quadratic tetrahedral element formulation seems to be very promising for foot and footwear applications as a result of decreased labor and expedited model development, all related to facilitated mesh generation.     

Finite element modeling of the first ray of the foot: a tool for the design of interventions

Disorders of the first ray of the foot (defined as the hard and soft tissues of the first metatarsal, the sesamoids, and the phalanges of the great toe) are common, and therapeutic interventions to address these problems range from alterations in footwear to orthopedic surgery. Experimental verification of these procedures is often lacking, and thus, a computational modeling approach could provide a means to explore different interventional strategies. A three-dimensional finite element model of the first ray was developed for this purpose. A hexahedral mesh was constructed from magnetic resonance images of the right foot of a male subject. The soft tissue was assumed to be incompressible and hyperelastic, and the bones were modeled as rigid. Contact with friction between the foot and the floor or footwear was defined, and forces were applied to the base of the first metatarsal. Vertical force was extracted from experimental data, and a posterior force of 0.18 times the vertical force was assumed to represent loading at peak forefoot force in the late-stance phase of walking. The orientation of the model and joint configuration at that instant were obtained by minimizing the difference between model predicted and experimentally measured barefoot plantar pressures. The model were then oriented in a series of postures representative of push-off, and forces and joint moments were decreased to zero simultaneously. The pressure distribution underneath the first ray was obtained for each posture to illustrate changes under three case studies representing hallux limitus, surgical arthrodesis of the first ray, and a footwear intervention. Hallux limitus simulations showed that restriction of metatarsophalangeal joint dorsiflexion was directly related to increase and early occurrence of hallux pressures with severe immobility increasing the hallux pressures by as much as 223%. Modeling arthrodesis illustrated elevated hallux pressures when compared to barefoot and was dependent on fixation angles. One degree change in dorsiflexion and valgus fixation angles introduced approximate changes in peak hallux pressure by 95 and 22 kPa, respectively. Footwear simulations using flat insoles showed that using the given set of materials, reductions of at least 18% and 43% under metatarsal head and hallux, respectively, were possible.     

Effects of alcohol and coca on foot temperature responses of highland Peruvians during a localized cold exposure

Two groups of highland Quechua Indian males were tested under conditions of local foot exposure to cold air (0°C). Foot temperatures were monitored throughout the hour cold test and for 16 minutes recovery at room temperature (24°C). In the first group (age range 14–20 years), 29 subjects were tested while chewing coca leaves and while under control conditions. The second group (age range 20–50 years) of 25 subjects was tested while consuming 1.1 gm of ethyl alcohol per kilogram of body weight and again under control conditions. Both drugs (coca and alcohol) are habitually consumed by members of the native population. The mastication of coca leaves had no effect on foot skin temperatures. Alcohol consumption, however, elevated foot temperatures to between 4 and 6°C higher than control values at the end of 60 minutes of cold exposure. It is suggested that alcohol consumption gives the Indian a slight thermal advantage and increases levels of comfort during natural cold exposure.     

A study of the viability of obtaining a generic animation of the foot while walking for the virtual testing of footwear using dorsal pressures

Establishing the appropriate pressure exerted by the shoe upper over the foot surface is fundamental for the design of specific footwear, although measuring the dorsal pressures can also provide important additional information. In previous works, a virtual simulator to perform studies of comfort and functionality in CAD footwear design was presented. This paper describes the procedure carried out to obtain the foot animations used in this simulator. The virtual feet used in the simulator are feet without a standard form scanned in a static way. Their movements are rebuilt from the register of movements of several foot anatomical points during a complete step. The dorsal pressures exerted by some shoe uppers on these anatomical points were measured for several subjects and used to establish the viability of the use of these animations in a virtual simulator for footwear.     

Effects of leg activity and ambient barometric pressure on foot swelling and lower-limb skin temperature during 8 h of sitting

Prolonged immobilization in an upright position often leads to discomfort and oedema in the feet of otherwise healthy subjects. To determine the significance of leg activity and ambient pressure on oedema formation, skin temperature (Tsk) and discomfort, 6 volunteers sat for 8 h with one leg immobilized and the other spontaneously active; one day at "sea level" (750 mmHg) and one day at reduced barometric pressure (540 mmHg). Foot swelling was measured by water plethysmography. Leg movements were continuously monitored by a Vitalog computer, and foot discomfort was estimated by analog-visual scales. The 8 hour swelling averaged 5.7% in the inactive foot, and 2.7% in the active foot (p less than 0.001). Tsk of the inactive foot levelled off towards ambient temperature (21 degrees C) within 4 h. For the active foot this fall was reduced by 2-3 degrees C (p less than 0.025). The increase in foot discomfort during the day was lowest in the active foot (p less than 0.005). High foot Tsk was associated with a high foot swelling rate. Reduced ambient barometric pressure had no effects on foot swelling or Tsk. It is concluded that modest leg activity during 8 h of sitting has several effects on the circulation in the feet: some effects promote and some prevent oedema formation. However, the net result is a reduction in foot swelling.     

Towards an efficient and robust foot classification from pedobarographic images

This paper presents a new computational framework for automatic foot classification from digital plantar pressure images. It classifies the foot as left or right and simultaneously calculates two well-known footprint indices: the Cavanagh's arch index (AI) and the modified AI. The accuracy of the framework was evaluated using a set of plantar pressure images from two common pedobarographic devices. The results were outstanding, as all feet under analysis were correctly classified as left or right and no significant differences were observed between the footprint indices calculated using the computational solution and the traditional manual method. The robustness of the proposed framework to arbitrary foot orientations and to the acquisition device was also tested and confirmed.     

Towards an efficient and robust foot classification from pedobarographic images

This paper presents a new computational framework for automatic foot classification from digital plantar pressure images. It classifies the foot as left or right and simultaneously calculates two well-known footprint indices: the Cavanagh's arch index (AI) and the modified AI. The accuracy of the framework was evaluated using a set of plantar pressure images from two common pedobarographic devices. The results were outstanding, as all feet under analysis were correctly classified as left or right and no significant differences were observed between the footprint indices calculated using the computational solution and the traditional manual method. The robustness of the proposed framework to arbitrary foot orientations and to the acquisition device was also tested and confirmed.     

Dimensions of a comparative biology of primate groups

The eruption time of deciduous teeth of the Bengalee children was noted and compared with the published material from other countries. It has been seen that the onset of eruption in the Bengalee children is appreciably late compared with the others (Japanese, Korean, American and Whites).     

The dynamics of the subtalar joint in sudden inversion of the foot

The human subtalar joint was modelled as a quasi-linear second-order underdamped system to simulate sudden inversion motion of the foot relative to the shank. The model was fed with experimental data obtained from six subjects on a specially constructed apparatus. A total of 35 deg inversion was produced on the tested leg rapidly enough (lasting less than 40 ms) in order to ensure that the protective muscles are not activated. The parameters of the joint were evaluated and the following ranges were obtained at 35 deg inversion: elastic stiffness 14-52 Nm rad-1, damping coefficient 1.4-2.9 Nms rad-1, and natural frequency 78-125 Hz. The effects on the test parameters of weight bearing amount, foot dominance, and protective footwear were studied on one subject.     

Age-related,interindividual, and right/left differences in anterior-posterior foot pressure ratio in preschool children

Background

This study aimed to examine age-related, interindividual, and right/left differences in anterior-posterior foot pressure ratio in 764 preschool children (364 boys and 400 girls) aged 3.5-6.5 years.

Methods

Subjects maintained an upright standing posture for 10 seconds on the Footview Clinic, an instrument designed to calculate the anterior-posterior foot pressure ratio. The ratio of anterior foot pressure in each subject’s right and left feet was selected as a variable, and the mean of a 10 s measurement was used for analysis.

Results

The ratio of anterior foot pressure was significantly larger in the right foot than in the left foot. With regard to age, the ratio of anterior foot pressure was significantly larger in children aged over 4.5 years than in children aged 3.5 years. It was also larger in children aged 6 and 6.5 years than in children aged 4 years. Interindividual differences in variables were large, and coefficients of variance were highest in children aged 3.5 years and lowest in children aged 6.5 years.

Conclusions

In conclusion, anterior foot pressure increases with age in preschool children. Interindividual differences in anterior foot pressure are large and tend to decrease with age. Furthermore, the anterior foot pressure is slightly higher in the right foot than in the left foot. These results will be useful for various studies, such as examining relationships between the anterior-posterior foot pressure ratio and factors, such as untouched toes, physical fitness, and level of exercise.     

Trunk kinematic,kinetic, and neuro-muscular response to foot center of pressure translation along the medio-lateral foot axis during gait

Footwear devices that shift foot center of pressure (COP), thereby impacting lower-limb biomechanics to produce clinical benefit, have been studied regarding degenerative diseases of knee and hip joints, exhibiting evidence of clinical success. Ability to purposefully affect trunk biomechanics has not been investigated for this type of footwear. Fifteen healthy young male subjects underwent gait and electromyography analysis using a biomechanical device that shifts COP via moveable convex elements attached to the shoe sole. Analyses were performed in three COP configurations for pairwise comparison: (1) neutral (control) (2) laterally deviated, and (3) medially deviated. Sagittal and frontal-plane pelvis and spine kinematics, external oblique activity, and frontal and transverse-plane lumbar moments were affected by medio-lateral COP shift. Transverse-plane trunk kinematics, activity of the lumbar longissimus, latissimus dorsi, rectus abdominus, and quadratus lumborum, and sagittal-plane lumbar moment, were not significantly impacted. Two linear mixed effects models assessed predictive impact of (I) COP location, and (II) trunk kinematics and neuromuscular activity, on the significant lumbar moment parameters. The COP was a significant predictor of all modeled frontal and transverse-plane lumbar moment parameters, while pelvic and spine rotation, and lumbar longissimus activity were significant predictors of one frontal-plane lumbar moment parameter. Model results suggest that, although trunk biomechanics and muscle activity were altered by COP shift, COP offset influences lumbar kinetics directly, or via lower-limb changes not assessed in this study, but not by means of alteration of trunk kinematics or muscle activity. Further study may reveal implications in treatment of low back pain.     

Musculoskeletal discomfort and feeling of fatigue among female professional workers: the need for ergonomics consideration.

Subjective feeling of general fatigue and physiological strain were studied in one hundred female professional employees of industrial worker and full-time nurses. Using an interview questionnaire the feeling of fatigue were studied. The subjects were asked to indicate on the body diagram all the areas of musculoskeletal pain from which they perceived discomfort. Furthermore physical strength test consisting of grip test, back and leg strength test were carried out before and after work on all subjects. The results indicated that the two groups of employees showed different symptoms of "pain" and/or "fatigue," with regard to the different parts of body. It was also noted that the physical strength after work was lower for both groups as compared to before work and even lower for the industrial workers than the nurses. The feeling of fatigue between the two investigated groups was not significantly different, but for the musculoskeletal pain was highly significantly different. The worker group used also more pain-killing drugs for releasing the muscle pain. It was evident that ergonomics intervention for female professional workers was of great importance and urgency, particularly for making the workplace more human. Improvement of the working conditions, better organization of work, and ergonomics interventions are suggested as necessary measures for reduction of pain and feeling of discomfort.     

Predicting changes in knee adduction moment due to load-altering interventions from pressure distribution at the foot in healthy subjects

The purpose of this pilot study of healthy subjects was to determine if changes in foot pressure patterns associated with a lateral wedge can predict the changes in the knee adduction moment. We tested two hypotheses: (1) increases or decreases in the knee adduction moment and ankle eversion moment due to load-altering footwear interventions can be predicted from foot pressure distribution and (2) changes in magnitude of the knee adduction moment and ankle eversion moment due to lateral wedges can be predicted from pressure distribution at the foot during walking. Fifteen healthy adults performed walking trials in three shoes: 0 degrees , 4 degrees , and 8 degrees laterally wedged. Maximum heel pressure ratio, first peak knee adduction moment, and peak ankle eversion moment were assessed using a pressure mat, motion capture system, and force plate. Increases or decreases in the knee adduction moment and ankle eversion moment were predicted well from foot pressure distribution. However, the magnitude of the pressure change did not predict the magnitude of the peak knee adduction moment change or peak ankle eversion moment change. Factors such as limb alignment or trunk motion may affect the knee adduction moment and override a direct relationship between the pressure distribution at the shoe-ground interface and the load distribution at the knee. However, changes (increases or decreases) in the peak knee adduction moment due to load-altering footwear interventions predicted from pressure distribution during walking can be important when evaluating these types of interventions from a clinical perspective.     

Off-loading the diabetic foot for ulcer prevention and healing

Retrospective and prospective studies have shown that elevated plantar pressure is a causative factor in the development of many plantar ulcers in diabetic patients and that ulceration is often a precursor of lower-extremity amputation. Herein, we review the evidence that relieving areas of elevated plantar pressure (off-loading) can prevent and heal plantar ulceration.There is no consensus in the literature concerning the role of off-loading through footwear in the primary or secondary prevention of ulcers. This is likely due to the diversity of intervention and control conditions tested, the lack of information about off-loading efficacy of the footwear used, and the absence of a target pressure threshold for off-loading. Uncomplicated plantar ulcers should heal in 6 to 8 weeks with adequate off-loading. Total-contact casts and other nonremovable devices are most effective because they eliminate the problem of nonadherence to recommendations for using a removable device. Conventional or standard therapeutic footwear is not effective in ulcer healing. Recent US and European surveys show that there is a large discrepancy between guidelines and clinical practice in off-loading diabetic foot ulcers. Many clinics continue to use methods that are known to be ineffective or that have not been proved to be effective while ignoring methods that have demonstrated efficacy.A variety of strategies are proposed to address this situation, notably the adoption and implementation of recently established international guidelines, which are evidence based and specific, by professional societies in the United States and Europe. Such an approach would improve the often poor current expectations for healing diabetic plantar ulcers.     

A simple field method to identify foot strike pattern during running

Identifying foot strike patterns in running is an important issue for sport clinicians, coaches and footwear industrials. Current methods allow the monitoring of either many steps in laboratory conditions or only a few steps in the field. Because measuring running biomechanics during actual practice is critical, our purpose is to validate a method aiming at identifying foot strike patterns during continuous field measurements. Based on heel and metatarsal accelerations, this method requires two uniaxial accelerometers. The time between heel and metatarsal acceleration peaks (THM) was compared to the foot strike angle in the sagittal plane (α_foot) obtained by 2D video analysis for various conditions of speed, slope, footwear, foot strike and state of fatigue. Acceleration and kinematic measurements were performed at 1000 Hz and 120 Hz, respectively, during 2-min treadmill running bouts. Significant correlations were observed between THM and α_foot for 14 out of 15 conditions. The overall correlation coefficient was r=0.916 (P<0.0001, n=288). The THM method is thus highly reliable for a wide range of speeds and slopes, and for all types of foot strike except for extreme forefoot strike during which the heel rarely or never strikes the ground, and for different footwears and states of fatigue. We proposed a classification based on THM: FFS<−5.49 ms<MFS<15.2 ms<RFS. With only a few precautions being necessary to ensure appropriate use of this method, it is reliable for distinguishing rearfoot and non-rearfoot strikers in situ.     

Kinematic analysis of a multi-segment foot model for research and clinical applications: a repeatability analysis

An unbiased understanding of foot kinematics has been difficult to achieve due to the complexity of foot structure and motion. We have developed a protocol for evaluation of foot kinematics during barefoot walking based on a multi-segment foot model. Stereophotogrammetry was used to measure retroreflective markers on three segments of the foot plus the tibia. Repeatability was evaluated between-trial, between-day and between-tester using two subjects and two testers. Subtle patterns and ranges of motion between segments of the foot were consistently detected. We found that repeatability between different days or different testers is primarily subject to variability of marker placement more than inter-tester variability or skin movement. Differences between inter-segment angle curves primarily represent a shift in the absolute value of joint angles from one set of trials to another. In the hallux, variability was greater than desired due to vibration of the marker array used. The method permits objective foot measurement in gait analysis using skin-mounted markers. Quantitative and objective characterisation of the kinematics of the foot during activity is an important area of clinical and research evaluation. With this work we hope to have provided a firm basis for a common protocol for in vivo foot study.