Determining the protective function of sports footwear

To reduce the risk of injury associated with foot-ground interaction during sporting activities, there is a need for adequate assessment of the protective function of sports footwear. The present objectives are to review the typical biomechanical approaches used to identify protection offered by sports footwear during dynamic activities and to outline some of the recent methodological approaches aimed at improving this characterization. Attention is focused on biomechanical techniques that have been shown to best differentiate safety features of footwear. It was determined that subject tests would be used in combination with standard mechanical techniques to evaluate footwear protection. Impact attenuation characteristics of footwear during sporting activities were most distinguished by analysis of tibial shock signals in the frequency and joint time-frequency domains. It has been argued that lateral stability and traction properties of footwear are better assessed using game-like manoeuvres of subjects on the actual sporting surface. Furthermore, the ability of such tests to discriminate between shoes has been improved through methods aimed at reducing or accounting for variability in individual execution of dynamic manoeuvres. Advances in tools allowing measurement of dynamic foot function inside the shoe also aid our assessment of shoe protective performance. In combination, these newer approaches should provide more information for the design of safer sports footwear.     

The role of athlete response tests in the biomechanical evaluation of running shoes

Abstract

The protection that the running shoe can offer against shock forces has been investigated by standard mechanical tests of individual materials or of a combination of materials used in running shoe manufacture, and by testing the athlete's response to a shoe by measuring the ground reaction forces produced by the runner while running in the shoes. The latter approach to the evaluation of running shoes has some considerable attraction because it purports to represent a more direct evaluation of the shoes' performance and accounts for the interaction that the athlete has with the shoe.

Measurements made on running shoes in this way have yielded some useful data on, for example, the effect of barefoot and shod-foot running, the effect of running speed and the effect of body weight on the magnitude of ground reaction forces. There have also been some anomalous results reported which indicate that the athlete's interaction with his running shoe is not as predictable or as consistent as was first thought. This has made detailed investigations of running shoe properties difficult.

This paper presents data from a series of studies which have attempted to uncover the nature of the inconsistency in the athlete's interaction with his running shoes. The results lead to the hypothesis that during the evaluation of various running shoe conditions, the athlete adopts a ‘movement pattern fixation’ which produces a consistent interaction with a particular shoe, but this fixation may change when the shoe or other conditions change. The implication of this hypothesis is that in the testing of running footwear using the athlete's responses, methods should be employed to establish the limits within which any movement pattern fixation may occur as a precursor to evaluating the footwear itself.     

Simulation of the behavior of the calfskin used as shoe upper material in footwear CAD

The aim of this work is to propound a mechanical behavior model for simulating the deformation of the shoe upper material in gait for footwear CAD applications. The chosen material is calfskin. The proposed material behavior for the working range is a linear elastic orthotropic model which considers large deformation and membrane and bending loading. The model was obtained from tensile tests and validated with two experiments: a test to measure the leather resistance to damage on lasting and a test that models the shoe forming process using lasts. The framework of this work is the simulation of the footwear deformation while walking for footwear computer-aided design, and these tests have been chosen because, in them, the shoe upper material is deformed in a similar way to those deformations that occur during a complete step. The tests have been simulated using the Finite Element Method. The results of this simulation show that, in most of the cases, the orthotropic model closely represents the real behavior of the leathers analyzed in this work.     

Use of pressure insoles to compare in-shoe loading for modern running shoes

The primary objective of this paper was to compare in-shoe loading for different models of running shoe using measurements of force distribution. It was hypothesised that a shoe designed with minimal focus on cushioning would demonstrate significantly higher peak forces and rates of loading than running shoes designed with cushioning midsoles. Loading was compared using in-shoe peak forces for six footwear conditions. It was found that peak rate of loading at the heel provided clear distinctions between shoes. In support of the study hypothesis, the shoe with minimal focus on cushioning had a significantly higher rate of loading than all but one of the other test shoes. Data collected for midfoot and forefoot areas of the foot highlighted the importance of considering loading across the foot surface. The results of the present study demonstrate that pressure insoles provide a useful tool for the assessment of loading across the foot plantar surface for different footwear conditions. There are numerous models of running shoe for individuals to select from, with limited information available regarding the performance of the shoes during running. The current study demonstrates differences in loads across the foot plantar surface during running, indicating differences in performance for different footwear models.     

Use of pressure insoles to compare in-shoe loading for modern running shoes

The primary objective of this paper was to compare in-shoe loading for different models of running shoe using measurements of force distribution. It was hypothesised that a shoe designed with minimal focus on cushioning would demonstrate significantly higher peak forces and rates of loading than running shoes designed with cushioning midsoles. Loading was compared using in-shoe peak forces for six footwear conditions. It was found that peak rate of loading at the heel provided clear distinctions between shoes. In support of the study hypothesis, the shoe with minimal focus on cushioning had a significantly higher rate of loading than all but one of the other test shoes. Data collected for midfoot and forefoot areas of the foot highlighted the importance of considering loading across the foot surface. The results of the present study demonstrate that pressure insoles provide a useful tool for the assessment of loading across the foot plantar surface for different footwear conditions. There are numerous models of running shoe for individuals to select from, with limited information available regarding the performance of the shoes during running. The current study demonstrates differences in loads across the foot plantar surface during running, indicating differences in performance for different footwear models.     

Modulation of mechanical and muscular load by footwear during catering

The BGN (Berufsgenossenschaft Nahrungsmithl und Gastst?tten) reports 70% of job induced days off work to be connected with traumas of the ankle joint or overloading of the leg, knee and lower back, with an increased incidence in service areas outdoors (R. Grieshaber, personal communication). Workspace environments usually contain narrow passages, slopes or stairs and sudden changes between different surfaces. The aim of this study was to investigate the biomechanical load on the lower extremity and the low back during catering service when wearing different types of footwear. Thus, the potential for altering mechanical stress experienced during catering by variations in footwear was explored. Sixteen experienced waiters followed a course typical for a combined indoor-outdoor service area. Three different types of footwear were investigated using pressure distribution measurements, rearfoot goniometry and electromyography. A discriminant analysis revealed that the factors subject, shoe and surface affect rear foot movement or pressure distribution in different ways. A MANOVA demonstrated significant differences in loading parameters between footwear types. In general, these differences increased in magnitude in critical situations, such as climbing stairs or crossing slippery surfaces. The results of this study demonstrate that manipulations to footwear offer a great potential for modulating loads experienced during catering. Based on the results, the effects of constructional features are discussed. The method proposed can be applied to evaluate shoe modifications under realistic workplace conditions.     

Modulation of mechanical and muscular load by footwear during catering

The BGN (Berufsgenossenschaft Nahrungsmithl und Gaststätten) reports 70% of job induced days off work to be connected with traumas of the ankle joint or overloading of the leg, knee and lower back, with an increased incidence in service areas outdoors (R. Grieshaber, personal communication). Workspace environments usually contain narrow passages, slopes or stairs and sudden changes between different surfaces. The aim of this study was to investigate the biomechanical load on the lower extremity and the low back during catering service when wearing different types of footwear. Thus, the potential for altering mechanical stress experienced during catering by variations in footwear was explored. Sixteen experienced waiters followed a course typical for a combined indoor?–?outdoor service area. Three different types of footwear were investigated using pressure distribution measurements, rearfoot goniometry and electromyography. A discriminant analysis revealed that the factors subject, shoe and surface affect rear foot movement or pressure distribution in different ways. A MANOVA demonstrated significant differences in loading parameters between footwear types. In general, these differences increased in magnitude in critical situations, such as climbing stairs or crossing slippery surfaces. The results of this study demonstrate that manipulations to footwear offer a great potential for modulating loads experienced during catering. Based on the results, the effects of constructional features are discussed. The method proposed can be applied to evaluate shoe modifications under realistic workplace conditions.     

The role of friction in the measurement of slipperiness,Part 1: Friction mechanisms and definition of test conditions

Friction has been widely used as a measure of slipperiness. However, controversies around friction measurements remain. The purposes of this paper are to summarize understanding about friction measurement related to slipperiness assessment of shoe and floor interface and to define test conditions based on biomechanical observations. In addition, friction mechanisms at shoe and floor interface on dry, liquid and solid contaminated, and on icy surfaces are discussed. It is concluded that static friction measurement, by the traditional use of a drag-type device, is only suitable for dry and clean surfaces, and dynamic and transition friction methods are needed to properly estimate the potential risk on contaminated surfaces. Furthermore, at least some of the conditions at the shoe/floor interface during actual slip accidents should be replicated as test conditions for friction measurements, such as sliding speed, contact pressure and normal force build-up rate.     

The role of friction in the measurement of slipperiness, Part 1: friction mechanisms and definition of test conditions.

Friction has been widely used as a measure of slipperiness. However, controversies around friction measurements remain. The purposes of this paper are to summarize understanding about friction measurement related to slipperiness assessment of shoe and floor interface and to define test conditions based on biomechanical observations. In addition, friction mechanisms at shoe and floor interface on dry, liquid and solid contaminated, and on icy surfaces are discussed. It is concluded that static friction measurement, by the traditional use of a drag-type device, is only suitable for dry and clean surfaces, and dynamic and transition friction methods are needed to properly estimate the potential risk on contaminated surfaces. Furthermore, at least some of the conditions at the shoe/floor interface during actual slip accidents should be replicated as test conditions for friction measurements, such as sliding speed, contact pressure and normal force build-up rate.     

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.     

A method for dynamic measurement of the resistance to dry heat exchange by footwear

Five different types of cold protective footwear have been tested with regard to their resistance to dry heat loss (i.e. the insulation) with a new electrically heated foot model. The model is able to simulate ‘walking’ movements in order to provide a more realistic simulation of wear conditions. Thermal insulation of shoes with and without a steel toe cap was the same. The insulating properties during simulated walking movements were 10–25% lower compared with static conditions. For two of the shoe models a significantly lower insulation value for the sole area was obtained when adding a weight of 30 kg. A significant difference could also be found between the insulation values of two different sizes of one of the models. Measurements with the standard method (EN 344) correlated well with the local insulation value of the sole part of the thermal foot. Correlation with the insulation value for the whole shoe was much less, variation was bigger and ranking in terms of cold protection differed between methods. The electrically heated foot model appears to provide a reproducible, accurate and more realistic method for measuring the insulation properties of shoes than EN 344.     

Effects of semi-rigid arch-support orthotics: an investigation with potential ergonomic implications

For many years, arch-support orthotics have been prescribed for individuals with discomfort and/or abnormal skeletal alignments in the structures of the lower extremity. Recently there has been an increased interest in promoting semi-rigid orthotics as an ergonomic aid for asymptomatic workers who must stand all day at their workplace. A laboratory study was performed to assess the biomechanical impact of prefabricated semi-rigid orthotics on asymptomatic individuals. Ten subjects wore semi-rigid arch-support orthotics (experimental condition) for two months and flexible polyurethane/Sorbothane shoe inserts (control condition) for two months. Throughout this 18-week testing period, the subjects returned to the lab to perform a battery of assessment tests at regularly scheduled intervals. These tests examined subject strength, standing posture, stability, fatigue effects, and body part discomfort. The results of this study showed no significant changes in the strength, posture, or stability as a function of insert type. The subjects reported a reduction in low-back discomfort along with an increase in foot discomfort during a fatiguing exertion task while wearing the semi-rigid orthotics as compared to the control condition.     

Design of experiments for the qualification of EVA expansion characteristics

Ethylene vinyl acetate (EVA) is a highly utilised material for the manufacture of shoe soles and mid-soles due to its comfort, durability and UV stability. It is also used extensively for exercise mats, wall insulation and sports protection padding. The material can be manufactured into sheets by compression moulding or injection-moulding processes. This paper is concerned with research to gain knowledge of the behaviour of EVA during the injection moulding of shoe soles and shoe mid-soles. Though there is significant experience with the general use of EVA during the injection-moulding process this knowledge has been gained through years of experience and moulds are designed by a combination of the producer's knowledge and trial and error. With the increase in demand for customisation of mass-produced products a method for automating the design of moulds for expanding EVA products is highly desirable. When mixed with a suitable blowing agent, EVA has the remarkable ability to expand between 30% and 90% compared to the injection mould size, depending on the amount of blowing agent added. However, EVA does not expand uniformly and currently there is no precise method of predicting the expansion of components with variable thickness. This paper presents a methodology for determining the expansion characteristics of EVA coupled with results relating to the initial findings for material expansion to enable the design of a method for automatically generating mould cavity geometry.     

Automatic shoe-pattern boundary extraction by image-processing techniques

A footwear designer digitizes shoe patterns to extract their boundaries, once he finishes 3D shoe-model design, last-bottom flattening, and shoe-pattern making. Shoe-pattern boundaries are then imported to cutting machines to cut material into shoe-pattern shapes. In the shoe-pattern making process, a footwear designer may draw many arcs, lines and pigments on a shoe pattern. Therefore, a shoe pattern has smudges, stains, and marker pen drawings on its surface. It results in the difficulty of automatically digitizing and extracting a shoe-pattern boundary. This study aims to develop an effective image-processing method to automatically extract the boundary of a shoe pattern. In the study, we first use a histogram thresholding technique to segment out a shoe pattern from the scanned input image. Then boundary extraction is applied on the segmented image to detect and smooth the shoe-pattern boundary. Finally, the proposed method is tested and its performance is evaluated. Experimental results indicate that the proposed method is good for automatic shoe-pattern boundary extraction.     

Subjective evaluation of running footwear depends on country and assessment method: a bi-national study

This study examined (1) the perception of running shoes between China (Beijing) and Singapore and (2) whether running shoe preference depended on assessment methods. One hundred (n = 50 each country) Chinese males subjectively evaluated four shoe models during running by using two assessment procedures. Procedure 1 used a visual analogue scale (VAS) to assess five perception variables. Procedure 2 was a ‘head-to-head’ comparison of two shoes simultaneously (e.g. left foot: A and right foot: B) to decide which model was preferred. VAS scores were consistently higher in Beijing participants (p < .001), indicating a higher degree of liking. Singapore participants used the lower end but a wider range of the 15 cm scale for shoe discrimination. Moderate agreement was seen between the VAS and ‘head-to-head’ procedures, with only 14 out of 100 participants matched all 6 pairwise comparisons (median = 4 matches). Footwear companies and researchers should be aware that subjective shoe preference may vary with assessment methods.

Practitioner Summary: Footwear preference depends on country and assessment methods. Running shoe perception differed between Beijing and Singapore Chinese, suggesting that footwear recommendation should be country-specific. Individuals' shoe preference measured by visual analogue scale when wearing complete pairs may not reflect that when directly comparing different models in left and right feet.     

Case study of the impact of toecap type on the microclimate in protective footwear

Protective footwear plays a critical role in work effectiveness and personal safety. It exhibits special properties due to the use of protective elements and materials, but these components may deteriorate its hygienic characteristics. This paper presents a study on the influence of toecap type on the microclimate in protective footwear (ankle boots). Toecaps made of metal and of a composite polymer material were evaluated. Changes in the footwear microclimate were monitored using a thermal foot model at a perspiration rate of about 5 g/h with and without the simulated movement function. The influence of the toecap material on the microclimate in the footwear was analyzed statistically. Under conditions of simulated movement, higher temperature and relative humidity values (about 32 °C and 90%) were recorded in the toe region of ankle boots with metal toecaps as compared to composite polymer toecaps (about 29 °C and 53%, respectively). These results suggest that protective footwear with composite toecaps ensures better ventilation of the foot during work.     

Exercise and sports equipment: some ergonomics aspects

Sports equipment encompasses a gamut of devices used in laboratory, training and competitive contexts and these form the content of this paper. Ergometers range in sophistication from friction braked stationary bicycles to computer controlled simulators which incorporate exercise modes specific to the athletic user. These are now used in training, as experimental devices and in some instances for competition purposes. Training equipment exhibits a similar emphasis on exercise specificity, safety being an important aspect of its use. Design of projectiles for sporting activities has mainly reflected their traditional modes of use, the introduction of synthetic materials having some ergonomics implications. Similarly, materials science and design technology have contributed innovations in equipment for racquet sports and hitting implements. The changes have tended to be associated with availability of new materials for product construction and have implications for safety and skill in the transition to using the new products. Ski equipment design illustrates ergonomics factors in interfacing the performer with the sporting environment and how equipment has progressed by regenerative design processes. Enhancement of performance in some sports must be accompanied by an awareness of safety requirements: where appropriate, risks to participants should be reduced by use of protective clothing and equipment. Enforced validation of protective equipment is recommended to raise safety levels in certain sports and the safety of spectators must not be neglected. Human factors criteria can then be applied in monitoring, officiating and spectating at sporting events.     

Biomechanically determined hand force limits protecting the low back during occupational pushing and pulling tasks

Though biomechanically determined guidelines exist for lifting, existing recommendations for pushing and pulling were developed using a psychophysical approach. The current study aimed to establish objective hand force limits based on the results of a biomechanical assessment of the forces on the lumbar spine during occupational pushing and pulling activities. Sixty-two subjects performed pushing and pulling tasks in a laboratory setting. An electromyography-assisted biomechanical model estimated spinal loads, while hand force and turning torque were measured via hand transducers. Mixed modelling techniques correlated spinal load with hand force or torque throughout a wide range of exposures in order to develop biomechanically determined hand force and torque limits. Exertion type, exertion direction, handle height and their interactions significantly influenced dependent measures of spinal load, hand force and turning torque. The biomechanically determined guidelines presented herein are up to 30% lower than comparable psychophysically derived limits and particularly more protective for straight pushing.

Practitioner Summary: This study utilises a biomechanical model to develop objective biomechanically determined push/pull risk limits assessed via hand forces and turning torque. These limits can be up to 30% lower than existing psychophysically determined pushing and pulling recommendations. Practitioners should consider implementing these guidelines in both risk assessment and workplace design moving forward.     

Image processing techniques for leather hide ranking in the footwear industry

The subjective assessment of finished leather hide has resulted in much argument, wasted costs and disruption of production schedules in both the tannery and leather footwear industry. Leather has attracted much research work worldwide; however, to date no objective quality assessment methodology is available, let alone an automatic assessment system. In this project, a machine-vision-based approach to grading leather hide has been developed. The image of a given castle hide was acquired using the developed machine vision system. A map of the different types of defect contours contained in the hide was extracted. Algorithms were then formulated enabling the computerization of the quarter rule, a standard method for grading leather hide in the footwear industry. Typical results from the developed grading process include the leather cuttable areas within a given hide, taking into account various types of defects, and the contour map of defects, which in fact is a vital input to any computerized shoe-part nesting system. The success of automatically grading leather hide in this project will not only provide the tanner with a means of accurately defining the price of a leather hide but also greatly assist the footwear manufacturer in the optimal nesting of irregular shoe parts within a given hide.