SPD 686_Bianca Rescalvo

Design Challenge: 

We aim to optimize between performance and perceptions of comfort and stability of the cleated foot during football-specific tasks. Range of motion and shoe weight are key elements of perceived elements of comfort and heavily influence football cleat selection, and arguably performance,  in elite football players. The hybrid (skill/power) positions of running back (RB), tight end (TE), and defensive end (DE), experience the unique challenge of managing agility and stability in high-speed play near the line of scrimmage. New understandings of ankle kinematics and loading patterns, as well as the kinesthetic, rather than structural, properties of ankle taping can be successfully integrated into football cleat design to optimize for improved perceptions of both stability and comfort with positive outcomes of range of motion and performance

Running backs, tight ends, and  defensive ends experience conditions of both a crowded line of scrimmage, high speeds of play, and sharp changes of direction. Unfortunately, these athletes’ unique role on the field puts them at high risk for ankle injuries. A 6-year study examining the epidemiology of ankle injuries at the NFL Combine found that the highest rates of ankle injuries occurred in running backs, offensive linemen, and tight ends, all of which had injury rates of approximately 60% (Mulcahey et al., 2018). Through research, it has become clear that increased range of motion is positively correlated to perceived comfort and perceived performance, and negatively correlated to stability.  Innovative solutions including the proprioceptive benefits of tactile stimulation of the ankle and plantar aspect of the foot may aid in designing a solution that balances both aspects and marginally decreases rates of ankle injury. 

Understanding Kinematics:

Dorsiflexion and plantarflexion, the primary motions of the ankle joint, occur within the sagittal plane. During the gait cycle of running,  a “normal” ankle allows about 10° of active dorsiflexion and 14° of active plantarflexion, though during the passive ranges of motion are notedly greater (15-20° and 45-55° degrees, respectively). The “normal” ranges for subtalar inversion are approximately 20-30° (Norkus et al., 2001). Due to the complex architecture of the foot and ankle, the movements of pronation and supination, key aspects of agility and athletic performance, involve triaxial movement of the ankle. Supination, for example, involves calcaneal inversion, foot adduction, and plantarflexion, while pronation involves eversion, foot abduction, and dorsiflexion (Norkus et al., 2001). It is important to consider the complexity of these movements during the design process so as not to overcorrect or impede on the natural and necessary ranges of motion required to perform football-specific tasks.

Looking deeper into the kinematics of elite football players, we can more closely assess the forces and vectors exerted onto the foot and ankle during common football movements. A series of tests conducted on professional football players examined loading patterns and kinematics of the foot and ankle. This study found that during cutting and direction changes, the ankle experienced near maximal subtalar inversion mean values of 20.6-30.1°  for agility-oriented players, coupled with peak talocural (dorsi/plantarflexion) mean values of 40-45.6 °, with peak dorsiflexion exceeding 30° (Riley et al., 2013). In lateral cuts and direction changes, the study observed medial force peaks between 84.3% and 112.7% of body weight, vertical force peaks of over 250% BW and anterior force peaks of approximately 93% BW. These data points gathered in the study support the research hypothesis that subtalar and talocural range of motion, as well as GRFs in various force vectors, approached or exceeded predefined physiological limits of “normal”  (Riley et al., 2013). It is without question that these athletes endure and subject their bodies to intense amounts of force and power to compete at the elite level, the majority of which is transferred through their feet and ankles into the ground. As we embark on the design process, we must keep in mind the importance of these ranges of motion for the athletic performance and success of these athletes. 

Various “solutions” exist with regards to managing ankle range of motion and stability for these athletes. Many of them present tradeoffs and adverse effects, or conflicting evidence regarding the efficacy of the claimed technique in improving performance outcomes. 

1. Cleat Height

Upper height is a common way to limit lateral motion of the ankle and control subtalar eversion. Football cleats are available in low-top, mid-top, and high-top configurations, which athletes typically select based on preference. A study by Drake University examined performance outcomes, range of motion, and perceived comfort of various styles of football cleat to better understand players’ footwear choices. They conducted various field drills typical to football-specific tasks in subjects wearing low-top, mid-top, and high-top cleats. Their findings concluded that the high-top cleats notably limited ankle dorsiflexion and inversion but not plantarflexion or eversion, and were overwhelmingly perceived as heavier and less comfortable than both the mid-top and low-top cleats (Daack et al., 2014). Mid-top and high-top cleats were rated similarly with regard to stability, while low-top cleats were perceived as less stable.  Although “no significant difference was found in performance outcomes”, I believe it is important to note that in the 60-yd sprint, recorded times increased by 0.12 seconds in the high-top vs. low-top cleat, a potential difference-maker in elite competition (Daack et al., 2014). Furthermore, the shoes were all constructed from a combination of synthetic leather, TPU, and mesh, with the following weights: high-top = 546g, mid-top = 502g, low-top = 457g. 

2. Taping / Prophylactics

Spatting, or taping over the cleat and ankle, is a widely used technique for increasing perceived ankle support for football players. This prophylactic bracing of the ankle limits range of motion upon initial taping, but quickly loses integrity upon the start of exercise. A study, also conducted by Drake University, examined the effects of spatting on perceived stability and comfort, as well as ankle ROM. Spatting significantly reduced inversion, plantarflexion, and dorsiflexion in both mid-top and low-top cleat scenarios and improved the perception of stability in both cleats.  Perceptions of comfort were lower in the mid-top than the low-top during cutting and sprinting scenarios. The study infers that cleat height and spatting have no significant performance impact and may provide more placebo effects of perceived stability than actual benefits, and presents the argument that the integrity of ankle taping deteriorates and loosens as quickly as 15 minutes post-application (Fanagel et al., 2013)

Another study examined the effects of various prophylactics on ROM and movement performance in vertical jump and agility testing. The study found that all varieties of prophylactics including taping reduced overall ankle ROM but also reduced agility in the time immediately after application, noting specifically that “taping application significantly reduced performance where plantar flexion of the ankle was required” (Metcalfe et al., 1997) They also noted that all ankle prophylactics lost their restrictive properties over time, which corresponds to findings from other studies and confirms the placebo effect mentioned previously by the study conducted at Drake University. Other studies mention ankle prophylactics decrease vertical jump height ranging from 3-5%, while others note no performance benefits or detriments (Metcalfe et al., 1997). 

Overall, the benefits of ankle taping may not lie in the reduction of ROM  but in the proprioceptive benefits it provides. This is a key consideration in designing a cleat optimized for range of motion, comfort, and perceived stability as we begin to uncover the functionality of various cleat attributes.

Proprioception:

A study from the University of Tennessee suggests that “the effects of ankle taping and bracing on proprioceptive input to the central nervous system (and) peroneal muscle activity…may be as important as restriction of the range of ankle inversion” (Wilkerson, 2002).  It cites various studies that confirm that cutaneous mechanoreceptors in the skin aid in perception of joint positioning when activated by tactile contact (through taping, ankle sleeves, etc.), and further suggest that joint position awareness before ground contact is an essential aspect in limiting lateral ankle injuries (Feuerbach et al., 1994). (BIO NEURO). It also explores the relationship between peroneal muscle activation and proprioceptive taping (Wilkerson, 2002). The peroneal muscles aid in postural stability during landing, correcting the position of the foot and ankle upon impact. Findings from various studies suggest that tape on the skin of the ankle increases peroneal muscle activation (assessed through electromyography), improving the reaction speed of these muscles by 8 – 13% when responding to sudden weight-bearing inversion (Lohrer et al., 1999). Furthermore, studies show that elastic tape, while providing minimal decrease in range of motion, is as effective as inelastic tape in preventing injury. This notion of “proprioceptive amplification” through stimulation of mechanoreceptors in the skin can successfully be exploited to enhance optimal joint positioning without reducing ROM. 

Further study of foot position awareness provides insight on the importance of plantar foot skin receptors for balance and ankle support, specifically in locomotion and jumping. A study from McGill University notes that “taping does not stabilize the ankle significantly (but)… helps by partly correcting loss of position awareness” (Robbins & Waked, 1997). They argue that neurophysiologic investigations indicate that precise kinesthetic awareness is derived almost entirely from tactile and muscle receptors, namely SAII mechanoreceptors, but athletic footwear attenuates stimuli for these receptors and thus decrease foot position awareness (Robbins & Waked, 1997).   

These studies point to a possible solution beyond the concept of movement restriction as the best preventative measure for injury mitigation and optimization of performance in agility sports. Evidence shows that restricting ankle ROM can have detrimental effects on speed, vertical and long jump performance, and is regarded as uncomfortable and undesirable as a footwear attribute for hybrid (speed/power) players in elite level football. Rather than restriction of the ankle through rigid spatting, bracing, and footwear construction, enhancement of the kinesthetic awareness of the foot and ankle, while maintaining comfort and ROM, will likely enhance both perceived and actual performance in elite football players. 

Prior Art / Patent Search:

1. Proprioceptive / Kinesthetic Elements 

US20130312159A1 : Articles of apparel providing enhanced body position feedback

By Nike Inc; Matthew D. Nordstrom, Richard W. Fox 

Attributes: 

• a garment structure having one or more fabric elements structured and arranged to provide a close fit to at least one predetermined portion of a body (e.g., area(s) of the body for which enhanced position sensing and/or feedback are desired, such as the lower back, the arch of the foot, etc.
• The body position feedback system may apply higher tensile or constricting (compressive) forces to selected portions of the wearer’s body, which can help stimulate or interact with nerves and deep tissue receptors located in various portions of the body. 
• The increased forces at selected locations of the body give the wearer sensory feedback regarding the position or orientation of these parts of the body and can improve or accelerate development of “muscle memory.”
• a foot position feedback system engaged with the garment structure at the arch portion, wherein the foot position feedback system includes a first region in the arch portion having a higher compressive force application capability than a compressive force application capability of the fabric element making up a largest proportion of the garment structure.

JP2017197870A: Sock

By Shimano Inc; 修平 邑本, Shuhei Muramoto, 修平 邑本, 務 味戸, Tsutomu Ajito, 務 味戸

Attributes: 

• PROBLEM TO BE SOLVED: To provide socks which can reliably suppress a positional deviation with respect to both of feet and bicycle shoes.
• The leg part comprises an Achilles tendon covering the Achilles tendon, The sock characterized in that the Achilles tendon is configured as a knitting knitting or a rib knitting in a lateral direction at a portion facing a mouth of a bicycle shoe.
• The sock according to claim 1, further comprising a belt-like ankle support portion that is a region corresponding to an outer side in the left-right direction of the foot and the outer heel and extends over a partial region of the foot portion and the leg portion.

DE202018006115U1: With near-surface nerves interacting foot and / or ankle bandage

By Fxf GmbH

Attributes: 

• An area of a human foot (10) and / or ankle (12) and under elastic pretensioning during wear bandage (14) on an inner surface (18) facing inside with at least one profiling (20), nubs and / or line-like and / or at least partially curved and / or meandering elevation (22), which is associated with near-surface nerve areas in the areas of the foot (10) and / or ankle (12) covered by the bandage (14); 
• produces an interaction and / or acts on these nerve areas by mechanical pressure effects, wherein a plurality of knob-like profilings (20, 22) are provided on their inner surface facing the skin surface (18), characterized in that the knob-like profilings (20, 22) overlap one another Extend area, which is supported with the bandage worn (14) the narrower ankle area (12) and at least partially runs around it.
• It is a primary object of the present invention to provide an improved system for alleviating polyneuropathic phenomena and / or diminishing self-awareness which is intended, in particular, to facilitate improvements in human motor skills during walking and running.

US8051582B2: Medially or laterally textured footbed

By Nike; Matthew Anthony Nurse, Mario A. Lafortune

Attributes: 

• Footbeds (e.g., in footwear, socks, etc.) for engaging a plantar surface of a wearer’s foot include one of the lateral or medial sides having a smooth or substantially smooth feel or surface while the opposite side has a textured feel or surface, e.g., by providing plural raised areas that define the textured feel or surface
• Depending on the location of the texturing (lateral side or medial side) and/or the type of ambulatory activity (e.g., running or walking), lower extremity movement during the activity may be affected, e.g., to reduce pronation, reduce maximum eversion, reduce rearfoot range of motion, reduce eversion velocity, reduce plantarflexion when pushing off during a step, reduce inversion at heel strike, reduce eversion range of motion, reduce maximum internal tibial rotation, to increase stability during cutting motions, etc.
• The footbed may be provided in a variety of different ways without departing from this invention. For example, the footbed may be integrally formed as part of the foot-covering member and/or the foot-supporting member structure(s) (e.g., integrally formed as part of the upper member and/or sole structure of an article of footwear).As another example, the footbed may be provided as a separate structure engaged with one or more of the foot-covering member and/or the foot-supporting member (e.g., as part of an insole member, as part of a sock liner, as a separate insert member, etc.)

US20180235307A1: Article of footwear incorporating a knitted component with an integral knit ankle cuff

By Nike Inc; Denis Dekovic, John Droege, Windra Fahmi, Jeongwoo Lee, Daniel A. Podhajny, Karl Seamarks, Doug D. Wilken

Attributes: 

• An article of footwear with a knitted component including an upper and an integral knit ankle cuff is provided.
• The upper and the ankle cuff are formed as a one-piece knit element. The knit element forms a portion of an exterior surface of the upper and an opposite interior surface of the upper, with the interior surface forming a void for receiving a foot. The ankle cuff is formed of unitary knit construction with the upper as a one-piece knit element and extends above a throat area of the upper
• The ankle cuff includes malleolus zones on medial and lateral sides to correspond with the ankle bones of a wearer. The knit component further incorporates features to assist with providing entry for a foot of a wear, providing comfort to a wearer, and to assist with orientation of the upper of the article of footwear when being worn.

2. Lacing Systems 

US7562470B2: Shoe with wraparound lacing

By Timberland Company; Martin Keen

Attributes: 

• The present invention provides a wraparound lacing system for use in all manner of footwear. The lacing system includes a lace which encircles the upper and midsole of the article of footwear in a spiral, helical, coiled or similar wound wraparound pattern.
• The upper includes finger members which independently adjust to the contours of the wearer’s foot while providing a snug and secure fit.
• The upper and midsole are integrally formed as a unitary structure. The housing of the upper and the midsole includes channels therein which receive the wraparound lace. 

US20110308115A1: Dynamic fit sleeve and independent lacing support cage for running footwear

 By K2 Corp; Tuan Le, Aaron Azevedo, David A. Jewell

Attributes: 

• A footwear and footwear construction method that creates the footwear upper sleeve (shoe upper) using at least two overlapping, layered panels of fabric oriented 90 degrees with respect to each other.
• A lacing system creates a support cage for the foot, which is independent from the footwear upper. The lacing support cage can be asymmetrical in several respects to accommodate the physically asymmetrical shape of the foot.
• The lacing system includes fingers independent from the footwear upper. The fingers then end in lace eyelets.

US6449879B1: Sports shoe with integral tongue and lacing system

By Nike Inc; Kevin Fallon, Michael A. Aveni

Attributes: 

• A sports shoe with an integral tongue and lacing system. The shoe includes an upper which is formed of a lateral portion and a medial portion. The medial portion extends across into the lateral side of the shoe and is configured to be placed beneath a longitudinal edge of the lateral portion. 
• A lining is placed on the interior surface of the medial portion such that the first and second rows of apertures are not exposed to the interior of the shoe.

US9414645B2: Shoe, in particular sports shoe

By Puma SE; Thomas Krueger

Attributes: 

• shoe upper part having two tensioning sections which are arranged adjacently in a tensioning region and are separated by a gap, wherein a fastening system is arranged by which the shoe can be fastened to the foot of the wearer of the shoe by a fastening lace as a result of the adjacently arranged tensioning sections being drawn towards one another.
• In order to improve the tension of the shoe on the foot of the wearer, the fastening system includes, in addition to the fastening lace, at least one tie element which has two ends, and wherein a loop of the at least one tie element formed in the region of the tensioning section being enlaced by the fastening lace.

US20140173943A1: Article of Footwear for Soccer

By Nike Inc; John Droege, Paul Hooper, Tetsuya T. Minami, Morgan Stauffer

Attributes: 

• An article of footwear has a sole including a toe portion and a heel portion, a toe bumper disposed on the toe portion, the toe bumper being configured to contact a ball, and a heel bumper disposed on the heel portion, the heel bumper being configured to contact the ball, wherein at least one of the toe bumper and the heel bumper has an asymmetric shape.
•  the sole system is associated with an upper that comprises an asymmetric lacing portion.
• the lacing portion including a first end portion disposed adjacent to an entry hole of the upper; the lacing portion including a second end portion disposed adjacent to a toe portion of the upper; and where the first end portion is disposed in the intermediate portion and where the second end portion is disposed in the medial portion.

EP0734662A1: Lacing System for Footwear

By Adidas AG; Guy A. Marshall

Attributes: 

• A footwear lacing system having a detachable tongue that is attached to shoe-mounted rings and splayed by a shoelace is disclosed. 
• The tongue includes a main body and radially extending fingers that form loops for receiving a shoelace. Rings, attached to the shoe, are configured to receive the fingers. Thus, the tongue is attached to the shoe by placing it over a throat of the shoe and placing the fingers through appropriately located rings. The fingers are thereafter double-backed toward a proximal midline of the shoe, and the shoelace is threaded through the fingers and tightened, causing the tongue to splay, thereby securing the shoe on a wearer’s foot.
• Alternatives are disclosed including asymmetrical tongues, collar straps, and wherein the shoelace is threaded through a combination of fingers and conventional eyelets.

Design Inspirations:

Scales and armor systems derived from nature are primary sources of inspiration for the design of the upper component of the football cleat. Articulation and mobility in conjunction with structure and protection using seamless and scalable geometry has been perfected by nature. The armadillo provides specific inspiration with regard to directional flexibility that can be oriented in the transverse plane to allow for optimal plantar- and dorsiflexion of the ankle, while fish scales and chiton mollusk armor provide form studies of armor with greater flexion. These organic forms can be further adapted for kinesthetic purposes such as tactile stimulation of the plantar aspect of the foot, such as is depicted in patent US8051582B2. The forms of these bio-derived armors are organic, keeping with the notion of enhancing natural movement and perceptions of comfort and stability. By uniting these forms with the aforementioned research, we can successfully design a running back-specific cleat that ensures comfort, mobility, and enhanced perceptions of stability without reduced ankle ROM 

Sources:

Daack, C., & Senchina, D. (2014). A Field Study of Low-Top vs. Mid-Top vs. High-Top American Football Cleats. Sports, 2(4), 85–98. doi: 10.3390/sports2040085

Fanagel, P. P., Drake, T. C., Dahl-Miller, A. R., & Senchina, D. S. (2013). Height variations in football shoes (cleats) may not alter ankle spatting effects in football field drills. Journal of Undergraduate Research & Scholarly Excellence, 4.

Feuerbach, J. W., Grabiner, M. D., Koh, T. J., & Weiker, G. G. (1994). Effect of an Ankle Orthosis and Ankle Ligament Anesthesia on Ankle Joint Proprioception. The American Journal of Sports Medicine, 22(2), 223–229. doi: 10.1177/036354659402200212

Karlsson, J., & Andreasson, G. O. (1992). The effect of external ankle support in chronic lateral ankle joint instability. Clinical Journal of Sport Medicine, 2(4), 291. doi: 10.1097/00042752-199210000-00017

Lohrer, H., Alt, W., & Gollhofer, A. (1999). Neuromuscular Properties and Functional Aspects of Taped Ankles. The American Journal of Sports Medicine, 27(1), 69–75. doi: 10.1177/03635465990270012001

Metcalfe, R. C., Schlabach, G. A., Looney, M. A., & Renehan, E. J. (1997). A comparison of moleskin tape, linen tape, and lace-up brace on joint restriction and movement performance. Journal of Athletic Training, 32(2).

Mulcahey, M. K., Bernhardson, A. S., Murphy, C. P., Chang, A., Zajac, T., Sanchez, G., … Provencher, M. T. (2018). The Epidemiology of Ankle Injuries Identified at the National Football League Combine, 2009-2015. Orthopaedic Journal of Sports Medicine, 6(7). doi: 10.1177/2325967118786227

Norkus, S. A., & Floyd, R. T. (2001). The Anatomy and Mechanisms of Syndesmotic Ankle Sprains. Journal of Athletic Training, 36(1), 68–73.

Riley, P. O., Kent, R. W., Dierks, T. A., Lievers, W. B., Frimenko, R. E., & Crandall, J. R. (2013). Foot kinematics and loading of professional athletes in American football-specific tasks. Gait & Posture, 38(4), 563–569. doi: 10.1016/j.gaitpost.2012.03.034

Robbins, S., & Waked, E. (1997). Foot Position Awareness: The Effect of Footwear on Instability, Excessive Impact, and Ankle Spraining. Critical Reviews in Physical and Rehabilitation Medicine, 9(1), 53–74. doi: 10.1615/critrevphysrehabilmed.v9.i1.30

Wilkerson, G. B. (2002). Biomechanical and Neuromuscular Effects of Ankle Taping and Bracing. Journal of Athletic Training, 37(4), 436–445.

Check out my cushioning project in the link below! Hit that fullscreen button

[embeddoc url=”https://blogs.uoregon.edu/spd686biancarescalvo/files/2020/04/BR_SPD686_CushioningDeck.pdf” download=”logged” viewer=”google” ]

Figures 1-4: Design and Assembly of SPEEDWEB System

Figures 5-7: Supplementary Construction Diagrams

Design Challenge: 

Encourage forefoot/midfoot strike pattern change while distributing load to aid in injury mitigation. A novel structure “SPEEDWEB” serves as a responsive cushioning element located at the forefoot (anterior to transverse arch) with high energy return as well as longevity. Introducing this into the footbed at the forefoot, coupled with traditional foam at the rearfoot, provides incentive for runners to strike at the forefoot. The biomimetic “SPEEDWEB” structure distributes load more efficiently than traditional foams due to its hierarchical structure, which is further parametrized based on optimal strike patterns. This works to create “the ultimate ride” to encourage runners to alter their strike pattern from rearfoot to forefoot striking, while minimizing overload of impact stress.

Background: 

Strike pattern in recreational and competitive running has endured controversy among athletes, biomechanists, and footwear companies alike. Effects on running economy, joint contact forces, and injury prevention have been explored through clinical studies, revealing tradeoffs between improving efficiency and adaptation limitations. Concerns over abrupt changes in strike pattern without proper adaptation and strengthening raise concern for those considering a switch from rearfoot strike to forefoot strike, despite substantial evidence on the benefits of forefoot-striking on performance and economy. A dramatic or unforgiving shift in running mechanics heavily strains untrained muscles, possibly leading to overuse injuries.

Biomechanical Findings: 

Evidence suggests a forefoot-strike pattern improves economy through enhanced storage of elastic energy in the foot and ankle as a result of longer and earlier plantarflexion activation during the stance phase of gait. 

A cross-disciplinary study conducted by the Claremont Colleges assessed the muscle activity and kinematics of forefoot and rearfoot strike runners, gathering evidence on timing of muscle activation and joint loading patterns. The study revealed that forefoot strikers activated the plantarflexor muscles 11% earlier and 10% longer than rearfoot strikers, and landed with more vertical shin angles at beginning of stance.  These findings indicate a shift of joint loading from the patellofemoral joint to the ankle, increasing load on the gastrocnemius and Achilles tendon and decreasing load on the patella and quadriceps. The study inferred this to be desirable as the Achilles is better equipped to store and translate elastic energy through the foot and ankle, thus improving economy.

These findings are significant not only from the standpoint of running economy but from the perspective of injury etiology and prevention. Patellofemoral knee pain, often dubbed “runner’s knee” is one of the leading injuries in recreational and dedicated runners. Several studies on prevalence and epidemiological trends of patellofemoral pain cite the syndrome as having an incidence rate of 22 – 25% annually.  A study conducted by The International Journal of Sports Physical Therapy compiled data from 10 studies previously conducted, finding patellofemoral pain to be the most prevalent pathology at sports medicine clinics, accounting for ⅕ to ⅓ of all recorded pathologies. 

These findings showcase a pervasiveness of a syndrome closely correlated to rearfoot strike patterns, despite advances in cushioning systems and running shoe design. This suggests that some improvement can be made with regard to strike pattern adaptation with the intention of reducing patellofemoral pain syndrome through a shift to forefoot- and midfoot-strike pattern. Encouraging a strike pattern change through sensory queuing can be achieved through materials selection, specifically with midsole and footbed cushioning. Differentiation of materials in the desired “strikezone” provides a form of feedback for the runner to begin to make the shift to a forefoot or midfoot strike. 

 With this intention comes the challenge of properly protecting the Achilles tendon and gastrocnemius during the adaptation phase to reduce the risk of overload injury. A possible solution to this challenge of proper adaptation and mitigation of injury is impact diffusion. The “strikezone” cushioning system, constructed using the biomimetic principles of the spiderweb (described below) can successfully diffuse the force of a forefoot strike into the larger surface area of the strikezone itself to aid in the strike pattern adaptation process of the runner, freeing them of stress overload. 

Structural Inspiration: 

As mentioned above, the mitigation of stress concentration can be achieved through a latticework structure derived from the construction of spiders’ webs. This biomimetic inspiration is grounded in the research and analysis of web structures as meticulous engineering achievements of nature. 

The 2-dimensional orb web is the structure many of us envision when thinking of spider webs. Though the properties of spider silk itself are quite impressive, the architecture of orb webs (as well as  3-dimensional funnel and cob webs) is an exceptional feat of structural engineering. The structure has evolved over millions of years to optimize the spider’s strict criteria. The ability of the web to withstand impact (generated by prey, wind, etc.) with minimum damage and at the lowest manufacturing cost showcases the opportunity for a biomimetic solution.

Looking deeper, the web possesses several characteristics and structural elements that can be replicated in a cushioning unit to yield the desired results. The hierarchy of threads used in the construction of a web, and the different properties of these threads creates a structure that is not only extremely efficient, but has a very high damage tolerance.  In other words, when threads on the web are damaged and break, force distribution remains unchanged throughout the web, ensuring its structural integrity. The remarkable force distribution of the web structure provides a design opportunity for a lightweight latticework system that properly distributes force throughout the cushioning unit. This can be applied to our challenge of encouraging a change to forefoot striking without increasing risk of injury.

Closer examination of the web structure reveals how this can be achieved. In a study conducted at the University of Madrid, scientists noted an overlooked aspect of the web: the secondary frame. This feature, highlighted and analysed by the study, found that it allowed the web to successfully dissipate impact force through “load paths” in the web from a variety of impact points mapped out on the web itself.  They further experimented with the length of the secondary frame radials to better understand the optimal radial length for maximum load distribution within the structure.

These findings are significant in designing a cushioning system that is not only lightweight and structurally sound, but offers an opportunity to explore load distribution in a forefoot cushioning unit that is forgiving enough to encourage training adaptations to forefoot strike patterns.

Prior Art: 

Lattice systems are not necessarily novel in midsole design, but have come to the fore in recent years. Lattice systems provide structure similar to that of a foam midsole, but often with reduced weight and an eye-catching design. Functionality of this system depends on the architecture of the lattice and mechanical properties of the materials used in the system. 

Perhaps the most notable existing lattice midsole system is Adidas’s Futurecraft 4D. Developed in collaboration with Carbon 3D, the liquid resin framework offers variable densities throughout the system. The patent for this technology was filed in 2018 under US20180271211A1. Key characteristics noted in the patent include the following: 

“The interconnected unit cells are connected at nodes having a valence number defined by the number of struts connected at that node. The valence number of the nodes may vary to provide customized characteristics to zones or portions of the midsole. The plurality of interconnected unit cells may be organized in a warped cubic lattice structure. The warped cubic lattice structure and the size/shape of interconnected unit cells may vary to provide customized characteristics to zones or portions of the midsole.”

Nike, however, patented a lattice structure in 2002 under US6763611B1 that describes a “sole including a three-dimensional, polymer lattice structure formed of a plurality of connectors that extend between a plurality of masses” and  “at least a portion of said connectors having a length extending in a direction that corresponds with a longitudinal length of said footwear, and at least another portion of said connectors having a length extending in a direction that corresponds with a lateral width of said footwear.”

Under Armour boasts three patents related to lattice structures in the midsole. The first, filed in 2016, US20160219976A1,describes a:  

“Midsole that includes a platform extending along a perimeter portion of the midsole and a lattice structure integrally formed with the platform, the lattice structure including a network of laths. The platform is molded to the user’s foot then integrated with the lattice below it to provide the cushion system.”

The second patent, US10010134B2, a renewal of a previous version, references that the midsole includes a lattice network of laths and nodes with a recess formed within the structure. A resilient foam insert is positioned in the recess of the lattice structure. The third patent US20160324260A1 describes a sole member connected to the upper, the sole member including a plurality of tubular structures, the plurality of tubular structures at least partially filled with a loose granular material.

Its important to note that these existing patents are characterized by a lattice structure rather than a pre-tensioned web system. They offer insight on manufacturing processes and open-structure midsole designs but support a different mechanism than the proposed SPEEDWEB design. More akin to the SPEEDWEB proposal is three-dimensional weaving systems such as those developed and patented by Three-D Composites Research Corp. These systems use multi-axial groups of rods oriented to develop 3D woven structures that can withstand impact forces from many directions. Related patents include US5076330A (expired in 2009) and US5348056A, which describes : 

“The present inventors proposed in their previous patent application, Japanese Laid-Open Patent Application H2-259148, a technology of weaving three-dimensional 4- or 5-axis woven fabrics with various fiber orientation angles in a facilitated manner by the use of a rotor-carrier type three-dimensional fabric weaving machine (hereinafter referred to simply as a “3D weaving machine” for brevity).” 

Looking forward: 

The proposed solution serves as an intermediary for runners seeking to transition from rearfoot-striking to forefoot-striking in a comfortable and safe fashion. It is important to understand the body’s ability to adapt requires time and training to influence these outcomes. Looking forward, individuals and institutions alike may strive to contradict the notion that forefoot striking is no more desirable than rearfoot striking. In understanding the evolution of bipedal locomotion and foot architecture, science arrives at the conclusion that humans were meant to run barefoot and with a forefoot strike pattern, but modern footwear has impeded our intrinsic foot strength abilities. Key evidence of this conclusion can be found in a valuable study from the Journal of Sport and Health Science. The study examined ground reaction forces in shod rearfoot strikers, shod forefoot strikers, and barefoot/minimalist forefoot strikers. Both the shod rearfoot- and forefoot-strikers bore similar ground reaction forces, while the minimalist forefoot strikers showed a markedly lower GRF than the other groups.  The study suggests that any type of cushioning influences running mechanics, but acknowledges the dangers of abrupt transition from rearfoot to forefoot strike patterns. It is this grey zone that we can hope to tackle, with the goal of reducing anterior knee pain, regaining intrinsic foot strength, and improving running economy.

Citations:

We revisited the Egg Drop Challenge that many of us did in middle school when learning about physics and inertia. This time around, the challenge was within the context of cushioning systems for midsole design. With that in mind, I started eggsperimenting…

V1: The Egg Cradle Sandwich

My first prototype took inspiration from hammocks and trampolines. I aimed to create a cradle zone using rubber bands that, upon impact, would slow the jolt and thus cushion the egg. I cut out a square in the center of two plastic cartons that would house the rubber band suspension system and egg. In this version, I chose to “suspend” the egg over one carton while the other served as a cradle (shown with the cardboard cylinder) as I was worried about it moving around too much.

This concept results in having one side of the sandwich that is designed for impact reduction and the other side is designed for stabilizing the egg so that it remains in the impact reduction zone. Unfortunately, the result is that there is a lack of cushioning on one of the sides, and upon impact the egg bounces off the suspension system and hits the stabilized side…. 🙁

Watch it in action: V1 Egg Drop Test

Results:

The cradle sandwich did not hold up, as I mentioned. While inside the sandwich, the egg bounced off the suspension system and smashed into the shell of the cradle. He never stood a chance. These results got me thinking about how to reduce or avoid the surfaces that my egg could potentially crash into. I realized that it needed to be suspended in multiple directions. This helped me begin prototyping V2….

V2: The Egg Roll

Lets eggsplore a different version of this concept! Taking what I learned from V1 and my main realizations, I began to develop V2.

My thinking during developing this version was that the roll of tape, upon impact, would roll along its edge and diffuse some of that force. I then wanted to suspend the egg without having it touch any surfaces, so I threaded rubber bands through two halves of a paper cup to create a suspended cradle for my egg. The rubber bands, wrapped around the roll of tape, create enough tension to suspend the egg and keep the halves together.

During the prototyping process, I switched to a wider roll of tape, figuring it would be more resilient and perhaps roll better, as well as create more tension for the rubber band suspension.  I realized the bottom surfaces of the paper cups were sticking out of the sides regardless of the width of the roll of tape, and prayed that V2 would land on the tape roll and not the paper cup. Coming to terms with this, I realized this version would only work in that scenario, eliminating vertical displacement in only that axis. Omelet you see how it went….

Check it out: IMG_1795

Results:

Bummerrrr….

My egg suspension system failed! The egg ended up popping out of its cradle and didn’t make it. I realized (aside from the issue with the single-axis impact protection) that the wider roll of tape resulted in insecurity of the cup system, as the cup halves were moved further away from each other, creating a “looser” cradle for my egg. Maybe I should have gone with the thinner tape. I would also be interested in how this works in a “toss” scenario rather than a drop. Its possible that it functions better with oblique impacts rather than straight-on drops.

Long story short, the cradle didn’t work because it was too loose, and the suspension only worked in one direction. My lessons from V1 and this new revelation in V2 helped me eggstrapolate what I needed to change for V3

V3: The GalEggxy

I defined two objeggtives from V1 and V2 that needed to be achieved in V3

1. Ensure the egg is in a tight cradle
2. Suspend the egg in all directions

Creating a cradle:

I chose to use a tennis ball and a napkin to create a tight cradle for my egg, which would then be suspended in all directions. I cut the tennis ball open (about 2/3 around), wrapped the egg in the napkin, and shoved it in there. There was no room for the egg to move within the tennis ball.

Before doing this, I punctured the tennis ball and threaded rubber hair bands through it, using the metal piece to anchor the bands on the interior of the tennis ball. This would be for suspension in the x-axis.

Suspending in all directions:

I hooked the rubber bands threaded in the tennis ball to nails on the far ends of the plastic container to successfully suspend the cradle in the x direction, adjusting the tension by wrapping the rubber band around the nail head multiple times. I then created another paper cup cradle (similar to V2) suspended from the lid of the container to ensure the tennis ball would slow down in the vertical direction upon impact.

The whole thing:

By far my most meticulous and egghaustive prototype, I felt confident in this suspension system. Wanna see how it went?

The Final Test: IMG_1811 2

The Results: IMG_1811 copy

He survived (twice)!!!! By addressing and fine tuning the issues I found with the earlier versions, I was able to create something that worked. 🙂

Hope you enjoyed this eggperience!

-Bianca