Forefoot Bending Stiffness Research Articles

The interdependence of functional properties of a football boot outsole during the shape optimisation process

The aim of this study was to investigate the relationship and interdependence of functional properties of the football boot outsole during the shape optimisation process. Sensitivity-based shape optimisation technique was applied to a football boot outsole to modify its thickness to have various functional properties. Three functional properties of the outsole, which are the midfoot and forefoot bending stiffness and torsional stiffness, were investigated. The midfoot and forefoot bending stiffness were measured via a three-point bending test. Torsional stiffness was measured via a bespoken mechanical test. The functional properties were evaluated by finite element models, representing the developed mechanical tests. Through the optimisation tasks, it was explored how much each functional property could be changed individually and also while minimising the influence of the other two functional properties. With the modification of the regions of the outsole to optimise for various individual target functional property values, the changes in the other two functional properties were observed. Lastly, the optimised outsoles from the finite element models were 3D printed and tested to determine the accuracy of the process. Within a permitted thickness limit, modifying the region associated with the torsional stiffness measurement influenced the other two functional properties the most. Especially, the midfoot bending stiffness was influenced more than the forefoot bending stiffness. On the other hand, the areas involved in the midfoot and forefoot bending stiffness measurements were independent of each other. The conclusions drawn in this study are limited to the particular outsole design, single outsole component and mechanical test utilised.

Individual physiological responses to changes in shoe bending stiffness: a cluster analysis study on 96 runners.

Shoe longitudinal bending stiffness is known to influence running economy (RE). Recent studies showed divergent results ranging from 3% deterioration to 3% improvement in RE when bending stiffness increases. The variability of these results highlights inter-individual differences. Thus, our purpose was to study the runner-specific metabolic responses to changes in shoe bending stiffness. After assessing their maximal oxygen consumption ([Formula: see text] max) and aerobic speed (MAS) during a first visit, 96 heterogeneous runners performed two treadmill 5min runs at 75% [Formula: see text] max with two different prototypes of shoes on a second day. Prototypes differed only by their forefoot bending stiffness (17N/mm vs. 10.4N/mm). RE and stride kinematics were recorded during each trial. A clustering analysis was computed by comparing the measured RE and the technical measurement error of our gas exchange analyzer to identify functional groups of runners, i.e., responding similarly to footwear interventions. ANOVAs were then computed on biomechanical and morphological variables to compare the functional groups. Considering the whole sample (n = 96), there was no significant difference in RE between the two conditions. Cluster 1 (n = 29) improves RE in the stiffest condition (2.7 ± 2.1%). Cluster 2 (n = 26) impairs RE in the stiffest condition (2.7 ± 1.3%). Cluster 3 (n = 41) demonstrated no change in RE (0.28 ± 0.65%). Cluster 1 demonstrated 1.7km·h-1 greater MAS compared to cluster 2 (p = 0.014). The present study highlights that the effect of shoe bending stiffness on RE is runner-specific. High-level runners took advantage of increased bending stiffness, whereas medium-level runners did not. Finally, this study emphasizes the importance of individual response examination to understand the effect of footwear on runner's performance.

The Influence of Forefoot Bending Stiffness of Futsal Shoes on Multiple V-Cut Run Performance.

A forefoot bending stiffness (FBS) property of footwear is known to benefit athletes in running performance. To date, the efficacy of bending stiffness on performance is rather unknown from the perspective of futsal shoes. This study investigates the influence of bending stiffness property of three commercial futsal shoes on change of direction run resultant performance. Nineteen university level athletes participated in the human performance test (multiple V-cut change of direction run) on a hardwood flooring facility using three pairs of futsal shoes (i.e., S1, S2, and S3) with different models but similar in outsole material (S1—mass: 311 g, heel-to-toe drop: 10 mm, friction coefficient, 1.25; S2—mass: 232 g, heel-to-toe drop: 8 mm, friction coefficient: 1.34; and S3—mass: 276 g, heel-to-toe drop: 7 mm, friction coefficient: 1.30). The FBS properties for each shoe were mechanically measured. Results from the analysis of variance indicated that there was a significant difference of FBS value among the three shoes (S1: 0.32 Nm/deg., S2: 0.26 Nm/deg., and S3: 0.36 Nm/deg.) [F(2,8) = 28.50 (p < 0.001)]. Shoes with relatively higher shoe-playing surface friction coefficient (S2 and S3) had significant impact on the V-cut performance (p < 0.05) when compared with the shoe with lower friction coefficient (S1). In contrast to the literature, the shoe with the lowest FBS (S2) did not suffer any detriments on the resultant performance in the test conducted. These findings suggested that there could be other performance limiting factors, such as the friction coefficient, rather than FBS that have greater influence on the test outcomes.

Shoe feature recommendations for different running levels: A Delphi study.

Providing runners with footwear that match their functional needs has the potential to improve footwear comfort, enhance running performance and reduce the risk of overuse injuries. It is currently not known how footwear experts make decisions about different shoe features and their properties for runners of different levels. We performed a Delphi study in order to understand: 1) definitions of different runner levels, 2) which footwear features are considered important and 3) how these features should be prescribed for runners of different levels. Experienced academics, journalists, coaches, bloggers and physicians that examine the effects of footwear on running were recruited to participate in three rounds of a Delphi study. Three runner level definitions were refined throughout this study based on expert feedback. Experts were also provided a list of 20 different footwear features. They were asked which features were important and what the properties of those features should be. Twenty-four experts, most with 10+ years of experience, completed all three rounds of this study. These experts came to a consensus for the characteristics of three different running levels. They indicated that 12 of the 20 footwear features initially proposed were important for footwear design. Of these 12 features, experts came to a consensus on how to apply five footwear feature properties for all three different running levels. These features were: upper breathability, forefoot bending stiffness, heel-to-toe drop, torsional bending stiffness and crash pad. Interestingly, the experts were not able to come to a consensus on one of the most researched footwear features, rearfoot midsole hardness. These recommendations can provide a starting point for further biomechanical studies, especially for features that are considered as important, but have not yet been examined experimentally.

Influence of forefoot bending stiffness on American football performance and metatarsophalangeal joint bending angle

ABSTRACT Changes in forefoot bending stiffness have been shown to affect metatarsophalangeal peak bending angles as well as athletic performance. Increasing bending stiffness tends to reduce peak bending angles, which could potentially reduce hyperextension injuries such as turf toe. Limited information is available, however, on the efficacy of increasing forefoot bending stiffness on large-sized athletes such as those that participate in American Football, with prior studies being conducted on smaller athlete populations. Therefore, the purpose of this study was to determine the influence of increased forefoot bending stiffness on metatarsophalangeal joint extension and athletic performance of grid-iron football players. Ten varsity grid-iron football players performed four National Football League combine movements in a motion capture laboratory in three footwear conditions of varying bending stiffness: Soft (12.7 N/mm), Control (23.8 N/mm), Stiff (42.2 N/mm). None of the footwear conditions significantly altered the maximum metatarsophalangeal bending. Therefore, to reduce metatarsophalangeal hyperextension injuries in American football players a greater amount of forefoot bending stiffness may be required. Performance differences were present only during the five-metre sprint acceleration, with athletes having an improved performance in the Control and Stiff conditions. This improved performance was due to an increased horizontal impulse and improvements in power generation at the ankle joint.

Effect of shoe modifications on biomechanical changes in basketball: A systematic review

ABSTRACT Shoe modifications are suggested to reduce the risks of injuries and improve sports performance in basketball. This review aimed to critically evaluate the effect of different basketball shoe modifications on biomechanical changes in basketball movements. Searches of four major databases for biomechanics studies which evaluated footwear construction/material in basketball yielded 442 records. After duplicates were removed and exclusion/inclusion criteria applied to the titles and abstracts, 20 articles remained for further quality assessment. Two reviewers independently confirmed 17 articles (n = 340 participants), with 95.5% of agreement between judgements, which were included for review. The results were categorised based on the following shoe modifications: (a) cushioning, (b) midsole hardness, (c) collar height, (d) outsole traction component, (e) forefoot bending stiffness and (f) shoe mass that influence lower limb biomechanics. The included articles revealed that 1) better shoe cushioning or softer midsole is related to better impact attenuation in passive/unanticipated situations, 2) high shoe collars are effective to improve ankle stability in jumping and cutting tasks, 3) increased shoe traction and forefoot bending stiffness can improve basketball jump, sprint and/or cut performances and 4) lighter shoe mass results in better jump and/or cut performances when the shoe mass is known.

Development of a Bendable Outsole Biaxial Ground Reaction Force Measurement System.

Wearable ground reaction force (GRF) measurement systems make it possible to measure the GRF in any environment, unlike a commercial force plate. When performing kinetic analysis with the GRF, measurement of multiaxial GRF is important for evaluating forward and lateral motion during natural gait. In this paper, we propose a bendable GRF measurement system that can measure biaxial (vertical and anterior-posterior) GRF without interrupting the natural gait. Eight custom small biaxial force sensors based on an optical sensing mechanism were installed in the proposed system. The interference between two axes on the custom sensor was minimized by the independent application of a cantilever structure for the two axes, and the hysteresis and repeatability of the custom sensor were investigated. After developing the system by the installation of force sensors, we found that the degree of flexibility of the developed system was comparable to that of regular shoes by investigating the forefoot bending stiffness. Finally, we compared vertical GRF (vGRF) and anterior-posterior GRF (apGRF) measured from the developed system and force plate at the same time when the six subjects walked, ran, and jumped on the force plate to evaluate the performance of the GRF measurement system.

The influence of gearing footwear on running biomechanics

The influence of nonlinear bending stiffness footwear, which alters the metatarsophalangeal (MTP) joint bending as a function of forefoot bending stiffness, has been postulated to improve athletic performance and reduce injury risk during many sports. As the shoe moves through greater amounts of bending, forefoot stiffness should increase nonlinearly, to shift the centre of pressure forward (improving performance), while restricting forefoot bending in regions where turf toe injury may result. Recently, materials which allow for stiffness modifications as a function of forefoot flexion angle have been developed; however, the efficacy of this technology is unknown. Therefore, the purpose of this project was to evaluate the influence of gearing technology (a variable bending stiffness shoe) on biomechanics during running and sprinting. Ten male recreational athletes performed running and sprinting in two footwear conditions consisting of an altered US 10 adidas 16.4 FXG cleat. The footwear was altered by placing carbon fibre insoles with variable (nonlinear stiffness) into the shoes creating two different conditions: Control (no insole) and the variable stiffness (varStiff) shoe (gearing insoles). Kinematic (joint angles) and kinetic (ground reaction force and 3D joint moments) data of the lower extremity were recorded during each movement. The results of the study indicate that the variable stiffness insoles did positively influence athlete lower extremity biomechanics. At the MTP joint, as running speed increased (and normal MTP bending range of motion increased), the variable stiffness insoles reduced the amount of MTP bending of the shoes and reduced the medial–lateral movement of the point of force application. Additionally, the variable stiffness insoles reduced key biomechanical injury risk variables, such as non-sagittal plane joint loading at the knee and ankle joint.

Effects of forefoot bending stiffness of badminton shoes on agility, comfort perception and lower leg kinematics during typical badminton movements

This study investigated whether an increase in the forefoot bending stiffness of a badminton shoe would positively affect agility, comfort and biomechanical variables during badminton-specific movements. Three shoe conditions with identical shoe upper and sole designs with different bending stiffness (Flexible, Regular and Stiff) were used. Elite male badminton players completed an agility test on a standard badminton court involving consecutive lunges in six directions, a comfort test performed by a pair of participants conducting a game-like practice trial and a biomechanics test involving a random assignment of consecutive right forward lunges. No significant differences were found in agility time and biomechanical variables among the three shoes. The players wearing the shoe with a flexible forefoot outsole demonstrated a decreased perception of comfort in the forefoot cushion compared to regular and stiffer conditions during the comfort test (p < 0.05). The results suggested that the modification of forefoot bending stiffness would influence individual perception of comfort but would not influence performance and lower extremity kinematics during the tested badminton-specific tasks. It was concluded that an optimisation of forefoot structure and materials in badminton shoes should consider the individual’s perception to maximise footwear comfort in performance.

Forefoot bending stiffness, running economy and kinematics during overground running

Previous research has shown that altering forefoot (FF) bending stiffness can enhance running economy; however, the mechanism behind the changes in running economy remains unknown. Therefore, the purpose of this study was to investigate the relationship between forefoot bending stiffness, running economy, and lower limb kinematics during overground running. Eighteen aerobically fit recreational male athletes performed overground running using a portable metabolic analysis system to measure oxygen consumption in two footwear conditions with different forefoot bending stiffness. Sagittal plane kinematic data of the metatarsophalangeal, ankle, and knee joints were recorded using a high-speed camera. On average, there was no difference in running economy when running in the Stiff shoe (O2 = 38.1 ± 5.4 mL/kg/min) compared to the Control shoe (O2 = 37.7 ± 5.8 mL/kg/min, p = 0.11). On an individual basis, 10 athletes (Responders) improved their running economy with increased FF bending stiffness (∆O2 = −2.9%), while eight athletes (Non-Responders) worsened or did not improve their running economy in a stiff shoe (∆O2 = +1.0%). In stiff footwear, Responders experienced kinematic changes at the ankle joint (decreased angular velocity) that likely resulted in decreased energy requirement for muscular contractions due to a presumed shift on their individual force–velocity relationship. The lack of improvement in running economy by the Non-Responders may be attributed to a presumed lack of a shift in the force–velocity relationship of the calf musculature. Instead, Non-Responders experienced kinematic changes (increased ankle plantarflexion during push phase with stiff footwear) that likely hindered their moment-generating capability potentially due to a shift on their individual force–length relationship. These findings represent important progress towards explaining inter-individual changes in running economy with different footwear bending stiffness.

Soccer shoe bending stiffness significantly alters game-specific physiology in a 25-minute continuous field-based protocol

The purpose of this study was to investigate the effects of soccer shoes with differing bending stiffness on physiological and performance variables in a game-like situation. A sample of 13 male soccer players was recruited to complete this study. Three soccer shoes with different forefoot bending stiffness (low, medium, high) were compared using a continuous field-based work protocol (the Soccer-25). Participants performed the Soccer-25 while the physiological (rate of oxygen consumption, heart rate, ventilation, and rate of energy expenditure) and performance variables (drill completion times) were recorded. The Soccer-25 consists of seven phases, Drills 1–3 and Shuttle Runs 1–4. A one-way repeated measures ANOVA was used to determine whether there were any significant effects for soccer shoe condition for each of the physiological and performance variables. The medium-stiffness shoe was significantly lower than the high-stiffness shoe for a number of physiological variables, including global oxygen consumption (p = 0.044), heart rate during Drills 2 (p = 0.043), ventilation during Shuttle Run 4 (p = 0.016), global energy expenditure (p = 0.043), and rate of energy expenditure during Drills 1 (p = 0.044). The low stiffness shoe was not significantly different from the medium- or high-stiffness shoes. No significant differences were found for any of the performance variables. Soccer shoe forefoot bending stiffness significantly affects the physiological variables in a game-like situation.

Quantifying the forefoot bending stiffness of cleated American football shoes using the Football American Shoe Tester (FAST)

In American football, hyper-dorsiflexion of the first metatarsophalangeal (first MTP) joint is the predominant mechanism of first MTP joint sprains (turf toe). The risk of acute first MTP joint sprain has been found to increase as first MTP joint angle increases. The bending resistance of the shoe dictates the proportion of an externally applied load that can be passed into the shoe (i.e. not through the first MTP joint) and thus may influence the magnitude of flexion imparted to the first MTP joint and hence the risk of injury. The current study introduces the Football American Shoe Tester (FAST), a flexion apparatus designed to measure the bending resistance of American football shoes at angles of forefoot dorsiflexion from 15° to 75°. The FAST was used to quantify the forefoot bending behaviour of a range of American football shoes. Thirty different models of US size 12 shoes were tested. Linearized bending stiffness ranged from 0.27 to 0.8 Nm/deg, while peak torque ranged from 11.8 to 25.5 N m. The testing revealed characteristic differences in torque-angle response across shoe models and quantified the extent of shoe stiffening at angles of dorsiflexion beyond those studied in the past.

Biomechanics research and sport equipment development

Advances in sport equipment have revolutionized athletic competition with engineers developing equipment that can enhance performance. However, not all athletes are able to benefit from the new, ideal equipment, with some athletes performing worse. Although the engineering may be sound, the interaction between the piece of equipment, the athlete, and the action is missing. The purely mechanical system of the piece of equipment becomes a biomechanical system once it is interacting with the athlete. Research into the underlying mechanisms of performance in sport has relied heavily on biomechanical studies. The review of these studies has identified important performance and injury variables that can be influenced by sport equipment. This baseline information helps provide a fundamental understanding of human performance that guide equipment designers and developers. A flawlessly engineered mechanical piece of sport equipment can still fail if the athlete–equipment interaction is not properly addressed in the design process. How an athlete uses a piece of equipment and furthermore how an athlete may change or adapt to changes in properties of a piece of equipment must be taken into consideration. Using properties of footwear as an example, research has provided understanding of the biomechanical limiting factors regarding the influence of footwear traction on athletic performance. Data on other footwear properties such as cushioning and forefoot bending stiffness are limited. Intrinsic musculoskeletal properties, such as the force–length and force–velocity relationships of skeletal muscle, can be exploited through equipment design, as has been shown during cycling. Modifications to equipment parameters can shift the operating range of an athlete within these relationships to maximize force or power output, which was shown during the development of the clap skate. Additionally, these properties vary slightly from athlete to athlete and minor adjustments to a piece of sporting equipment can help optimize individual athletes according to their specific biomechanical characteristics.

Influence of basketball shoe mass, outsole traction, and forefoot bending stiffness on three athletic movements

Prior research has shown that footwear can enhance athletic performance. However, public information is not available on what basketball shoe properties should be selected to maximise movement performance. Therefore, the purpose of the study was to investigate the influence of basketball shoe mass, outsole traction, and forefoot bending stiffness on sprinting, jumping, and cutting performance. Each of these three basketball shoe properties was systematically varied by ±20% to produce three shoe conditions of varying mass, three conditions of varying traction, and three conditions of varying bending stiffness. Each shoe was tested by 20 recreational basketball players completing maximal effort sprints, vertical jumps, and a cutting drill. Outsole traction had the largest influence on performance, as the participants performed significantly worse in all tests when traction was decreased by 20% (p < 0.001), and performed significantly better in the cutting drill when traction was increased by 20% (p = 0.005). Forefoot bending stiffness had a moderate effect on sprint and cutting performance (p = 0.013 and p = 0.016 respectively) and shoe mass was found to have no effect on performance. Therefore, choosing a shoe with relatively high outsole traction and forefoot bending stiffness should be prioritised, and less concern should be focused on selecting the lightest shoe.

Forefoot bending stiffness of cleated American football shoes

In American football, hyper-dorsiflexion of the first metatarsophalangeal (1 MTP) joint is the predominant mechanism of 1 MTP sprains (turf toe). The risk of acute 1 MTP sprain has been found to increase as 1 MTP angle increases. The bending resistance of the shoe dictates the proportion of an externally applied load that can be passed into the shoe (i.e., not through the 1 MTP joint) and thus influences the magnitude of flexion imparted to the 1 MTP joint. This study quantified the forefoot bending resistance of a range of cleated American football shoes. A total of 21 pairs of size 12 shoes were dynamically tested over flexion angles from 30° to 90°. Bending stiffness ranged from 0.10 to 0.35 Nm/deg, while peak torque ranged from 5.1 to 16.6 Nm. The relationship between torque and flexion angle was nearly linear for all of the shoes tested and the peak torque values were substantially lower than 1 MTP joint moments that have been measured in the human foot during athletic activities. These results suggest that an opportunity exists to better balance athletic performance and acute 1 MTP joint injury risk by incorporating non-linearity into the torque-angle characteristic of football cleats, such that the proportion of external load borne by the shoe increases at flexion angles above 60°.

Forefoot bending stiffness, running economy and kinematics during overground running

Forefoot bending stiffness, running economy and kinematics during overground running

Apparatus for measuring the forefoot bending stiffness of cleated American football shoes

Apparatus for measuring the forefoot bending stiffness of cleated American football shoes

Influence of forefoot bending stiffness on American football performance

A common injury in American football is strain and rupture of the plantar capsule ligament crossing the metatarsophalangeal (MTP) joint caused by hyperextension, commonly termed turf-toe (Rodeo, O'...

Influence of basketball shoe mass, traction and bending stiffness on athletic performance

Footwear properties such as shoe mass, outsole traction and forefoot bending stiffness can enhance athletic performance (Frederick 1984, Stefanyshyn and Nigg 2000, Muller 2010). However, the practi...

Effect of forefoot bending stiffness of badminton shoe sole on lower leg kinematics during match-like situations

A badminton shoe with greater shoe sole or bending stiffness may influence foot kinematics such that it reduces torsion and bending of the forefoot (Park et al. 2011). Stiffening the shoe sole has ...