Shoe Outsole Research Articles

A Systematic Review of Effects on ACL Injury of Soccer Shoe Outsoles, Soccer Playing Field Surfaces, and Outsole–Surface Interface

Soccer is a sport with a high incidence of injuries. The most common injury occurs when the anterior cruciate ligament of the knee has undergone a sprain, strain, or partial or total rupture. Besides fitness factors (e.g., proprioception, balance and strength capabilities), a principal cause of ACL injuries is sport shoes and playing surfaces. Especially with the emergence of artificial surfaces (rubbers, turfs, concrete, asphalt, red turf), the ACL injuries dramatically increase. The cost of ACL injuries is high both in terms of career termination and in social and economic costs. Thus, it is necessary to understand the impact of sport shoes and playing surfaces on the ACL and how it can be mitigated. The present literature review followed the PRISMA methodology to identify the major biomechanical factors influencing the behavior of surfaces and shoes in relation to the ACL damage. Fifty-eight papers were identified. After reviewing the mechanism of injuries, we identified several distinct factors: type of outsole and mechanical arrangement of the outsoles; shear forces; characteristics of artificial turf surfaces; effect of weather on artificial surface aging and change in mechanical characteristics; outsole/ground interface; and the frictional, tractional and rotational forces in the pathogenesis of ACL injuries in soccer.

Unveiling the Biomechanical Insights: Motor Control Shifts Induced by Shoe Friction Adjustments and Their Impact on Defensive Slide, Crossover Dribbling, and Full Approach Jump in Basketball

This study endeavors to explore the intricate interplay between the fundamental skills of basketball—defensive slide, crossover dribbling, and full approach jump—and the shoe outsole friction coefficient, with the overarching goal of advancing our comprehension regarding the pivotal role of footwear in athlete performance. Employing a comprehensive methodology that integrates 3D motion capture, force platform dynamometry, and biomechanical modeling, the study seeks to quantify the inherent motor control intricacies associated with these fundamental skills. Data collection involved 12 varsity players, and the research systematically assesses the influence of the shoe friction coefficient on both skill quality and injury risk, utilizing a set of 13 parameters for evaluation. The findings unveil that, with an increased friction coefficient, the following changes occur: for the defensive slide, we observed decreased contact time (p < 0.05), boosted medio–lateral impulse (p < 0.05), and lowered ankle torque (p < 0.01); for crossover dribbling, we observed increased anterior–posterior impulse (p < 0.05) and ankle torque (p < 0.05); for the full approach jump, we observed decreased contact time (p < 0.05) and increased jump height (p < 0.05). Generally, the equal increment in the shoe outsole friction coefficient did not result in equal changes in the selected parameters of motor skill control, indicating a non-linear relationship between the performance quality of essential basketball skills and the shoe friction coefficient. The results suggest the potential existence of an optimal value for skill execution. Notably, the study identifies that, while an augmentation in the friction coefficient enhances specific skill aspects, there is a discernible saturation point, signifying diminishing returns. This investigation makes a substantial contribution to our understanding of the precise impacts of shoe friction coefficients on basketball skills, thereby prompting considerations for the judicious selection of optimal friction coefficients and advocating for possible personalized footwear recommendations based on individual biomechanical profiles.

Slip Risk Prediction Using Intelligent Insoles and a Slip Simulator

Slip and fall accidents are the leading cause of injuries for all ages, and for fatal injuries in adults over 65 years. Various factors, such as floor surface conditions and contaminants, shoe tread patterns, and gait behavior, affect the slip risk. Moreover, the friction between the shoe outsoles and the floor continuously changes as their surfaces undergo normal wear over time. However, continuous assessment of slip resistance is very challenging with conventional measurement techniques. This study addresses this challenge by introducing a novel approach that combines sensor fusion technology and machine learning techniques to create intelligent insoles designed for fall risk prediction. In addition, a state-of-the-art slip simulator, capable of mimicking the foot’s motion during a slip, was developed and utilized for the assessment of slipperiness between various shoes and floor surfaces. Data acquisition involved the collection of pressure data and three-axial accelerations using instrumented shoe insoles, complemented by friction coefficient measurements via the slip simulator. The collected dataset includes four types of shoes, three floor surfaces, and four surface conditions, including dry, wet, soapy, and oily. After preprocessing of the collected dataset, the simulator was used to train five different machine learning algorithms for slip risk classification. The trained algorithms provided promising results for slip risk prediction for different conditions, offering the potential to be employed in real-time slip risk prediction and safety enhancement.

Penurunan Lead Time Manufacturing Dengan Pendekatan Lean Manufacturing Studi Kasus Di PT. MKM

In the industrial world, it is very important to pay attention to the efficiency of production capacity where the manufacturing lead time for making shoe outsole is influenced by activities that are not value-added (Non Value Added) and activities that are not value-added but necessary (Necessary Non Value Added) in which there is some extravagance that occurs. These activities are in the form of temporary storage in the cooling room and the process of reworking defective products. The method used is Lean Manufacturing, the tools used are Value Stream Mapping (VSM) and Process Activity Mapping (PAM). VSM is used to identify activities that have cycle times exceeding takt time, followed by mapping the Activity Mapping process to analyze activities that are not Value Added. Based on the results of research from 4110 seconds, the process lead time of 3600 seconds is a non-value added activity. The rework process and material storage in the cooling room were identified as having the largest value contributing to lead time, so rework must be eliminated. the percentage of Process Cycle Efficiency (PCE) has increased. The reduction of the finished sheet material process is cooled to the cooling room and the rework process can save about 60 minutes of working time. Saving working hours can increase outsole production capacity so that productivity increases and targets are achieved.Keywords: Lead Time Manufacture, Lean Manufacturing, Value Stream Mapping, Prose Activity Mapping. Process Cycle Activity.

Prospective validity assessment of a friction prediction model based on tread outsole features of slip-resistant shoes

Shoe outsole design strongly influences slip and fall risk. Certain tread features that can be readily measured have been shown to predict friction performance. This research aimed to replicate those findings and quantify their ability to predict slipping. Participants (n = 34) were exposed to a low friction oil-coated floor surface, while wearing slip-resistant shoes. The coefficient of friction (COF) of each shoe were predicted based on tread surface area, the presence of a bevel, and hardness. The COF was measured, and the slip outcome was determined. Predicted and measured COF were correlated, and measured COF was a sensitive predictor of slip outcome. The relationship of predicted COF on slip outcome was weaker than anticipated and was not statistically significant. This study partially confirmed the ability of previous regression equations to predict COF. However, the effect size was weaker than previously reported and predicted COF was not sensitive for predicting slips.

Variation of Muscle Activity and Balance of the Lower Extremity by Deformed in Shoe Out-soles during One-leg Stance

Variation of Muscle Activity and Balance of the Lower Extremity by Deformed in Shoe Out-soles during One-leg Stance

Validation of a portable shoe tread scanner to predict slip risk

Problem: Worn shoes are an important contributor to occupational slip and fall injuries. Tools to assess worn tread are emerging; imaging tools offer the potential to assist. The aim of this study was to develop a shoe tread scanner and evaluate its effectiveness to predict slip risk. Methods: This study analyzed data from two previous studies in which worn or new slip-resistant shoes were donned during an unexpected slip condition. The shoe tread for each shoe was scanned using a portable scanner that utilized frustrated total internal reflection (FTIR) technology. The shoe tread parameters of the worn region size (WRS) for worn shoes and total contact area for new shoes were measured. These parameters were then used to predict slip risk from the unexpected slip conditions. Results: The WRS was able to accurately predict slip risk, but the contact area was not. Discussion: These findings support that increased WRS on the shoe outsole is associated with worse slip outcomes. Furthermore, the tool was able to offer robust feedback across a wide range of tread designs, but the results of this study show that the tool may be more applicable for slip-resistant shoes that are worn compared to their new counterparts. Summary: This study shows that FTIR technology utilized in this tool may be a useful and portable method for determining slip risk for worn shoes. Practical Applications: This tool has the potential to be an efficient, objective, end-user tool that improves timely replacement of shoes and prevention of injuries.

Study on the Change in the Mechanical Properties of Leather Solid Waste-based Shoe Outsoles according to the Leather Solid Waste Content and Binder Mixing

Study on the Change in the Mechanical Properties of Leather Solid Waste-based Shoe Outsoles according to the Leather Solid Waste Content and Binder Mixing

Effect of the end-face corner radius of a rubber block on the friction coefficient and fluid-free gap under glycerin lubrication

The friction and area of the fluid-free gap between a glass plate and rubber blocks with different end-face corner radii were investigated under glycerin lubrication. Decreasing the end-face corner radius increased both the friction coefficient and area of the fluid-free gap, which indicates that the area and friction coefficient have a positive correlation. The fluid-free gap may be caused by negative fluid pressure associated with rubber block deformation, which increases the contact pressure on the front side of the rubber block. Our findings may contribute to the development of rubber products such as shoe outsoles that provide high friction under lubrication.

Effect of Shoe Outsole Wear on Friction during Dry and Wet Slips: A Multiscale Experimental and Computational Study

Effect of Shoe Outsole Wear on Friction during Dry and Wet Slips: A Multiscale Experimental and Computational Study

Trail running events contribute microplastic pollution to conservation and wilderness areas

Clothing and footwear designed for trail running shed microplastics (MPs) during use. Trail running events may therefore present a significant source of MP pollution in conservation and wilderness areas. Microplastics may present long-term risks to biodiversity and endemic plant and animal species in such areas. In this study, we used a before-after-control-impact approach to quantify and characterise MP emissions from clothing and shoe outsoles during trail running events. Microplastic deposition on trail surfaces was assessed using both a controlled study and during two public trail running events in New South Wales, Australia (the Duval Dam Buster and the Washpool World Heritage Trail Race). Microplastics were present on trails after all events and included fibres and rubber fragments. Microplastic counts varied considerably depending on trail surface hardness and gradient, and clothing and footwear properties. The controlled study showed running tights (leggings) and shoes with soft rubber outsoles produced more MPs than shirts and hard rubbers. In the trail running events, abrasive wear to shoe outsoles produced an average of 0.3 ± 0.1 to 0.9 ± 0.2 MPs/linear metre/runner, and clothing produced 0.7 ± 0.3 to 2.0 ± 0.3 fibres/linear metre/runner, with fibres accounting for 63–69% of MPs. Microplastic deposition from both footwear and clothing was higher on sloped and rock trail surfaces than flat and soil surfaces. Laser Direct Infrared (LDIR) Imaging indicated the main types of MPs present on trails were polyurethane, polyethylene terephthalate and polyamide. Trail running is increasing in popularity and large-scale events may cause a rapid and significant input of MPs in protected areas. Land managers, event coordinators and outdoor apparel manufacturers could mitigate MP impacts however, by diverting foot traffic around ecologically sensitive areas, capping participant numbers, and developing abrasion resistant clothing and footwear.

Fast and accurate centerline extraction algorithm for a laser stripe applied for shoe outsole inspection.

Line laser 3D reconstruction technology is widely used in industrial applications. As a key step of this technology, line laser midline extraction directly affects the accuracy of the 3D reconstructed model. In reconstructing the shoe outsole, the traditional algorithm based on the threshold method to determine the laser position may result in a large amount of information loss and miscellaneous point misjudgment owing to the irregularity of the shoe outsole surface, which critically affects the laser imaging quality. To address this problem, an algorithm based on the QQ plot inspection of the laser has been proposed. The QQ plot is a scatter plot, the abscissa is usually the quantile of the standard normal distribution, and the ordinate is the quantile of the data to be tested. If the points on the scatter plot tend to be straight lines, the data to be tested is in a normal distribution. Based on this property, the proposed algorithm aims to check whether the pixels of the image column tend to be normally distributed, rather than using traditional thresholding methods to locate the laser. The objective is to examine whether the image column pixel distribution is normal, instead of using the traditional threshold method to locate the laser. However, the calculation speed of this method is extremely low. To enhance the efficiency of testing the normality of the QQ plot, a quantile-repetition (Q-R) test method is proposed. In this approach, the degree of repetition of quantiles and the position of Q-R values are used to replace the QQ plot based evaluation of the points being on a straight line, and the exact center position is determined by the GGM. The experimental results show that the proposed algorithm can extract more effective points and fewer invalid points of the laser compared to those obtained using the traditional approach, in a rapid, stable, and accurate manner.

Are male netball players satisfied with the shoes that they wear for netball?

Despite the recent growth of men participating in netball, the footwear needs of male netball players have been largely neglected by researchers and shoe manufacturers. This study aimed to determine whether male netball players were satisfied with the shoes they currently wore for netball and explore the reasons why many men do not wear netball-specific shoes. 279 amateur, sub-elite and elite male netball players completed a 38-question online survey about their footwear habits and foot-related problems. A mixed-methods approach was used to analyse the quantitative and qualitative survey data. Irrespective of shoe type worn, men were dissatisfied with the width fit, durability and breathability of the shoes they currently wore for netball activity. The participants desired to modify the outsole, insole and toe box of the current shoes they wore for netball. Men also identified a diverse range of non-shoe design and shoe design factors related to fit and functionality that deterred them from wearing netball-specific footwear. It is recommended that the fit and functionality of shoes designed for male netball players are improved to better cater for the foot dimensions and netball performance demands of men.

Traction Performance of Common Formal Footwear on Slippery Surfaces

Traumatic injuries caused due to slipping and falling are prevalent in India and across the globe. These injuries not only hamper quality of life but are also responsible for huge economic and compensation burdens. Unintentional slips usually occur due to inadequate traction between the shoe and floor. Due to the economic conditions in low and middle-income countries, the public tends to buy low-cost footwear as an alternative to costly slip-resistant shoes. In this study, ten high-selling formal shoes under $25 were considered. These shoes were tested on three commonly available dry floorings and across contaminated common floor surfaces (i.e., water and floor cleaners). The traction performance of the shoes was quantified by using a biofidelic slip tester. The majority of formal shoes were not found to produce the slip-resistant performance across common slippery surfaces. Shoes with softer outsoles exhibited increased slip-resistant performance (R2 = 0.91). Shoe outsoles with less-to-no treads at the heel region showed poor traction performance as compared to other shoes. The apparent contact area was found as an important metric influencing the slip risks in dry and wet slipping conditions (R2 = 0.88). This research is anticipated to help the public and footwear manufacturers select safer shoes to reduce slip-and-fall incidents.

Medio-lateral and lateral edge friction in indoor sports shoes

It has previously been speculated that the occurrence and severity of lateral ankle sprain injuries is linked to excessive shoe–surface friction. Especially, the lateral parts of the shoe outsole are suggested to play an important role in such scenarios but have never been quantified in a systematic manner. Therefore, the purpose of this study was to investigate the variation of friction of indoor sport shoes with foot orientation and compare it to the traditional industry forefoot friction test standard. We modified the ISO:13287:2019 test for footwear slip resistance and positioned the shoe on its forefoot and lateral edge while replicating medio-lateral movements similar to previously reported ankle sprain incidents. All tests were conducted on an indoor vinyl/sport surface. The results from the modified setups were compared to those following the anterior-posterior orientated ISO standard. Medio-lateral friction was on average 17% lower and lateral edge friction 24% lower than anterior-posterior forefoot friction (p < .001). However, linear regression showed that the forefoot test could only explain 36% and 35% of the variation in medio-lateral and edge friction. This suggests that motion-specific tests are necessary to determine footwear friction properties meaningfully. These findings could have important implications for future research and product testing in the field of footwear friction, safety and injury prevention.

Using Gas Counter Pressure and Combined Technologies for Microcellular Injection Molding of Thermoplastic Polyurethane to Achieve High Foaming Qualities and Weight Reduction.

Microcellular injection molding technology (MuCell®) using supercritical fluid (SCF) as a foaming agent offers many advantages, such as material and energy savings, low cycle time, cost-effectiveness, and the dimensional stability of products. MuCell® has attracted great attention for applications in the automotive, packaging, sporting goods, and electrical parts industries. In view of the environmental issues, the shoe industry, particularly for midsole parts, is also seriously considering using physical foaming to replace the chemical foaming process. MuCell® is thus becoming one potential processing candidate. Thermoplastic polyurethane (TPU) is a common material for molding the outsole of shoes because of its outstanding properties such as hardness, abrasion resistance, and elasticity. Although many shoe manufacturers have tried applying Mucell® processes to TPU midsoles, the main problem remaining to be overcome is the non-uniformity of the foaming cell size in the molded midsole. In this study, the MuCell® process combined with gas counter pressure (GCP) technology and dynamic mold temperature control (DMTC) were carried out for TPU molding. The influence of various molding parameters including SCF dosage, injection speed, mold temperature, gas counter pressure, and gas holding time on the foaming cell size and the associated size distribution under a target weight reduction of 60% were investigated in detail. Compared with the conventional MuCell® process, the implementation of GCP technology or DMTC led to significant improvement in foaming cell size reduction and size uniformity. Further improvement could be achieved by the simultaneous combination of GCP with DMT, and the resulting cell density was about fifty times higher. The successful possibility for the microcellular injection molding of TPU shoe midsoles is greatly enhanced.

Rotational traction of soccer football shoes on a hybrid reinforced turf system and natural grass

Traction between a football shoe and the playing surface influences a players’ ability to perform football-specific movements. Too little traction means a player might slip. Too much traction is thought to increase the risk of injury due to foot fixation on the turf. Rotational traction is linked to increased injury risk in football. Elite football is increasingly played on hybrid reinforced natural grass playing surfaces. Our aim is to assess the magnitude of rotational traction of one new hybrid turf system and compare that to a natural grass (control) surface. Nine different Football shoes from three outsole groups (artificial grass, firm ground, soft ground) were loaded onto a portable shoe-surface traction machine to collect rotational traction data on two different playing surfaces (1. Natural Rye grass, 2. A hybrid reinforced turf system) at a single testing session. Peak rotational traction was significantly different across different shoe models (F = 379.8, df = 8, p < 0.0001) and shoe outsole groups (F = 387.4, df = 2, p < .0001). No significant difference was found between the natural grass surface and the hybrid reinforced turf system after considering the minimal detectable change (MDC) of the traction device. Wide-ranging differences in peak rotational traction were found across different individual soccer shoes and outsole groups. The Adidas Nemesis (AG) showed the lowest traction and the Nike Vision (SG) shoe had the highest traction (MD 28.7 N.m; 95% CIs 26.4–30.9; p < 0.0001). The artificial grass (AG) group showed the lowest traction values while the soft ground (SG) group the highest. This objective shoe-surface traction data can help with more informed footwear choices for football played on this type of hybrid playing surface to minimize the risk of lower extremity injury.

Effect of a carbon reinforcement for maximizing shoe outsole bending stiffness on plantar pressure and walking comfort in people with diabetes at high risk of foot ulceration

BackgroundDifferent shoe design features can reduce peak plantar pressure to help prevent foot ulcers in people with diabetes. A carbon reinforcement of the shoe outsole to maximize bending stiffness is commonly applied in footwear practice, but its effect has not been studied to date. Research questionWhat is the effect of a carbon shoe-outsole reinforcement on peak plantar pressure and walking comfort in people with diabetes at high risk of foot ulceration? MethodsIn 24 high-risk people with diabetes, in-shoe regional peak pressures were measured during walking at a comfortable speed in two different shoe conditions: an extra-depth diabetes-specific shoe with a non-reinforced outsole and the same type of shoe with a 3-mm-thick full-length carbon reinforcement of the outsole. The same custom-made insole was worn in both shoe conditions. Walking comfort was assessed using a Visual Analogue Scale (0–10, 10 being highest possible comfort). ResultsSignificantly lower metatarsal head peak pressures (by a median 10–22 kPa) were found with the reinforced shoe compared to the non-reinforced shoe (p < .001). In >83% of cases with the reinforced shoe and >71% with the non-reinforced shoe metatarsal head peak pressures were <200 kPa. At the hindfoot, peak pressures were significantly higher (by a median 24 kPa) with the reinforced shoe (p = .001). No significant shoe effects were found for the toes. No significant shoe effects were found for walking comfort: median 6.1 for the reinforced shoe versus 5.6 for the non-reinforced shoe. SignificanceAdding a full-length carbon reinforcement to the outsole of a diabetes-specific shoe significantly reduces peak pressures at the metatarsal heads, where ulcers often occur, in high-risk people with diabetes, and this does not occur at the expense of patient-perceived walking comfort.

Gait kinetics impact shoe tread wear rate

BackgroundAdequate footwear is an important factor for reducing the risk of slipping; as shoe outsoles wear down, friction decreases, and slip and fall risk increases. Wear theory suggests that gait kinetics may influence rate of tread wear. Research questionDo the kinetics of walking (i.e., the shoe-floor force interactions) affect wear rate? MethodsFourteen participants completed dry walking trials during which ground reaction forces were recorded across different types of shoes. The peak normal force, shear force, and required coefficient of friction (RCOF) were calculated. Participants then wore alternating pairs of shoes in the workplace each month for up to 24 months. A pedometer was used to track the distance each pair of shoes was worn and tread loss was measured. The wear rate was calculated as the volumetric tread loss divided by the distance walked in the shoes. Three, mixed linear regression models were used to assess the impact of peak normal force, shear force, and RCOF on wear rate. ResultsWear rate was positively associated with peak RCOF and with peak shear force, but was not significantly related to peak normal forces. SignificanceThe finding that shear forces and particularly the peak RCOF are related to wear suggests that a person’s gait characteristics can influence wear. Therefore, individual gait kinetics may be used to predict wear rate based on the fatigue failure shoe wear mechanism.

Tread Patterns and the Effect on Basketball Player Slippage

The focus of this study was to investigate the effects that different basketball shoe outsole tread patterns have on the amount of slip and therefore the performance of the individual while undergoing normal basketball transitions. Tread grooves and patterns must exist on the outsole of a basketball shoe to account for the chances of contamination and for the practical durability of the shoes. With the existence of so many basketball shoes with varying tread patterns and characteristics it presents the question of whether or not varying patterns affect traction, slip, and athletic performance. This study evaluated the amount of slips of two pairs of basketball shoes with human participants running basketball drills on a hardwood basketball floor at Wartburg College. The results indicated that one shoe with a more unique tread pattern exhibited fewer slips and severe slips, especially when considering lateral movements, than the shoe with a tread pattern seen more often in shoes available on the market today.