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\"Kicksology is your all-access pass into every runner's favorite obsession: shoes. Author Brian Metzler, a longtime sports journalist and veteran running shoe wear- tester, reviewer and connoisseur, takes readers deep inside the $10 billion dollar running shoe industry, with a behind-the-curtain look at what makes iconic running shoe brands tick; a shoe's birth from inspiration to innovation to shelf; how small, innovative ideas have evolved into mega-trends; inside domestic and overseas shoe factories where products are built; alongside scientists in the lab who test shoe science; and, of course, a discussion of the controversial relationship between running shoes and injury\"-- Provided by publisher.

Objective: Our study aim is to identify and describe the definitions used for different types of running shoes. In addition, we highlight the existence of gaps in these concepts and propose possible new approaches. Methods: This review was undertaken in line with the guidelines proposed by Green et al., based on a literature search (until December 2019) of the PubMed, Web of Science, Scopus, SPORTDiscus and Google Scholar databases. A total of 23 papers met the inclusion criteria applied to identify the definition of running shoes. Results: Although there is a certain consensus on the characteristics of minimalist footwear, it is also described by other terms, such as barefoot-style or barefoot-simulating. Diverse terms are also used to describe other types of footwear, and in these cases, there is little or no consensus regarding their characteristics. Conclusions: The terms barefoot-simulated footwear, barefoot-style footwear, lightweight shoes and full minimalist shoes are all used to describe minimalist footwear. The expressions partial minimalist, uncushioned minimalist and transition shoes are used to describe footwear with non-consensual characteristics. Finally, labels such as shod shoes, standard cushioned running shoes, modern shoes, neutral protective running shoes, conventional, standardised, stability style or motion control shoes span a large group of footwear styles presenting different properties.

Introduction: Running long distances results in transient flattening of the medial foot arch with the navicular bone moving medially and distally. This could be part of the explanation for the increased injury risk in running long distances. We hypothesized that stability running shoes would result in lesser navicular displacement compared to carbon shoes after running 90 min on hard surface. Methods: Twenty healthy male recreational runners with normal feet assessed with foot posture index score 0–5 were recruited. We performed cone beam CT (CBCT) scanning non‐weight bearing (NWB) and weight bearing (WB) before running 90 min and WB immediately after the run. Participants performed one run in stability shoes and repeated the run in carbon shoes on the exact same route maintaining the same speed 1–4 weeks apart. Results: The navicular height changed significantly from NWB 33.3 mm (SD 3.6) to WB 30.7 mm (SD 4.1, p < 0.001), and from WB before the run 30.7 mm (SD 4.1) to WB after the run 30.1 mm (SD 4.0, p = 0.02). No measurable differences were observed between shoe types. A majority of the runners claimed less perceived exertion and more comfort in the carbon shoes. Conclusion: Deformation of the medial plantar arch is measurable after a 90 min run assessed by navicular displacement on CBCT. Novel carbon shoes seem to support the medial foot arch as much as stability shoes.

According to standards, the heel soles of running shoes are currently tested with an energy absorption of 5 J. This study offers an alternative method to improve the measurement of cushioning properties. The new method uses the ratio of absorbed energy to applied force and determines the maximum of this ratio (optimum or shoulder point) and the associated optimal force, energy, and displacement. This method was applied to 112 shoe models using compression testing. The method was found to be insensitive to strain rates and identified shoes that were over-, well-, or under-designed (running before, at, or after the shoulder point, respectively) relative to the range of the first ground reaction force peak (0.700–2 kN). The optimum ratio was between 0.6 J/kN (barefoot shoes) and 11.2 J/kN (Puma RuleBreaker), the optimal energy was between 0.5 and 40.6 J, the optimal force was between 0.1 and 4.6 kN, and the optimal displacement was between 3 and 23 mm. Participants ran at or near the shoulder point (within the design forgiveness range) unless they were too heavy and ran at their preferred running speed. This study proposes replacing current standards with the new method, allowing consumers to make informed decisions regarding injury prevention while running.

The carbon-plated midsole in running shoes plays a pivotal role in enhancing the runner's performance by storing and releasing energy. A key factor in running shoes is the Longitudinal Bending Stiffness (LBS), where higher LBS usually improves energy efficiency by enhancing energy return during a running cycle. However, a critical trade-off exists: excessive LBS can diminish performance and may increase the risk of injury. To this end, this study aims to model and optimize the balance between energy efficiency and stability through finite element analysis (FEA). Specifically, the LBS was systematically adjusted by varying midsole foam materials and carbon plate thicknesses. A total of two FEA models were employed: a three-point bending simulation accessing LBS, and a lateral loading model accessing rearfoot stability. Boundary conditions for both models were defined through preliminary simulations. A parametric analysis was conducted by varying the midsole foam material and carbon plate thickness to identify optimal configurations. Preliminary results indicate that EVA midsoles exhibited the greatest LBS and stability, followed by PEBA, both outperforming TPU. Furthermore, thicker carbon plates showed a higher value of LBS but had little effect on stability. This research provides a novel standard of LBS testing and a novel FEA modeling framework for designing carbon-plated running shoes that enhance performance while reducing injury risks.

Background: Although numerous studies have been conducted to investigate the acute effects of shoe drops on running kinematics and kinetic variables, their effects on muscle forces remain unknown. Thus, the primary aim of this study was to compare the muscle force, kinematics, and kinetic variables of habitually rearfoot runners with heel-to-toe drops of negative 8 mm shoes (minimalist shoes) and positive 9 mm shoes (normal shoes) during the running stance phase by using musculoskeletal modeling and simulation techniques. Methods: Experimental data of lower limb kinematics, ground reaction force, and muscle activation from 16 healthy runners with rearfoot strike patterns were collected and analyzed in OpenSim. Using Matlab, the statistical parameter mapping paired t-test was used to compare the joint angle, moment, and muscle force waveform. Results: The results revealed differences in the sagittal ankle and hip angles and sagittal knee moments between the different heel-to-toe drops of running shoes. Specifically, it showed that the negative 8 mm running shoes led to significantly smaller values than the positive 9 mm running shoes in terms of the angle of ankle dorsiflexion, ankle eversion, knee flexion, hip flexion, and hip internal and hip external rotation. The peak ankle dorsiflexion moment, ankle plantarflexion moment, ankle eversion moment, knee flexion moment, knee abduction moment, and knee internal rotation also decreased obviously with the minimalist running shoes, while the lateral gastrocnemius, Achilleas tendon, and extensor hallucis longus muscles were obviously greater in the minimalist shoes compared to normal shoes. The vastus medialis, vastus lateralis and extensor digitorum longus muscles force were smaller in the minimalist shoes. Conclusions: Runners may shift to a midfoot strike pattern when wearing negative running shoes. High muscle forces in the gastrocnemius lateral, Achilleas tendon, and flexor hallucis longus muscles may also indicate an increased risk of Achilleas tendonitis and ankle flexor injuries.

Correspondence to Dr Benno M Nigg, Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB T2L 1N4, Canada; nigg@ucalgary.ca The effect of shoe mid-sole construction on running performance was discussed with reference to the Nike Vaporfly 4%.1 Drs Burns and Tam described the mid-sole thickness as the major running shoe characteristic that contributes to changes in performance. [...]the results of the leg model (representative of average-level runners) correlated with the results of the field tests. [...]it appears inappropriate to regulate one specific footwear feature before understanding where these performance advantages originated from.7 However, our current knowledge suggests that, compared with the teeter-totter effect, all other shoe characteristic contributions to performance are small and negligible.

When Nike compared its energetic cost (running economy) to contemporary elite racing shoes, the Vaporfly provided a 4% improvement in economy (hence the shoe’s moniker) and an estimated 3.4% increase in running speed.1 Subsequent independent laboratory testing2 and big-data performance analyses3 have corroborated the benefit. Schematic of the Nike Vaporfly 4% (images adapted from Nike.com) Carbon-fibre plate The full-length embedded carbon-fibre plate increases the longitudinal bending stiffness of the shoe, reducing running economy by 1%.5 While widely used in sprinting spikes, it was an uncommon addition to long-distance racing shoes. The Vaporfly has a 31 mm heel-height, and weighs 184 g, whereas the Streak has a 23 mm heel-height and weighs 181 g. This provides the energetic benefit of increased cushioning without incurring the energetic penalty of added weight.7 8 Moreover, the thicker midsole extends the effective leg length of the runner. [...]selecting parameters for shoe regulation would be troublesome up front and operationally burdensome over time for the IAAF. [...]a precedent exists: IAAF Rule 143.5 stipulates a sole and heel thickness for shoes used in high jump and long jump competitions.

The biomechanics of barefoot running Before the introduction of modern padded running shoes in the 1970s, and for most of human evolutionary history, humans ran either barefoot or in minimal shoes. A comparison by Daniel Lieberman and colleagues of the biomechanics of habitually shod versus habitually barefoot runners now suggests that the collision-free way that barefoot runners typically land is not only comfortable but may also help avoid some impact-related repetitive stress injuries. Kinematic and kinetic analyses show that modern shoes allow runners to land on the heel, as they do when they walk. Runners who don't wear shoes land more often on the ball of the foot or with a flat foot. This means that they often flex their ankles as they strike the ground and generate smaller impact forces than shod, rear-foot, strikers — compare the impact generated by landing from a jump on your heel versus your toes. Although humans have engaged in long-distance running either barefoot or with minimal footwear for most of human evolutionary history, the modern running shoe was not invented until the 1970s. Here, runners who habitually run in sports shoes are shown to run differently to those who habitually run barefoot, with the latter often landing on the fore-foot rather than the rear-foot. This strike pattern may have evolved to protect from some of the impact-related injuries now experienced by runners. Humans have engaged in endurance running for millions of years 1 , but the modern running shoe was not invented until the 1970s. For most of human evolutionary history, runners were either barefoot or wore minimal footwear such as sandals or moccasins with smaller heels and little cushioning relative to modern running shoes. We wondered how runners coped with the impact caused by the foot colliding with the ground before the invention of the modern shoe. Here we show that habitually barefoot endurance runners often land on the fore-foot (fore-foot strike) before bringing down the heel, but they sometimes land with a flat foot (mid-foot strike) or, less often, on the heel (rear-foot strike). In contrast, habitually shod runners mostly rear-foot strike, facilitated by the elevated and cushioned heel of the modern running shoe. Kinematic and kinetic analyses show that even on hard surfaces, barefoot runners who fore-foot strike generate smaller collision forces than shod rear-foot strikers. This difference results primarily from a more plantarflexed foot at landing and more ankle compliance during impact, decreasing the effective mass of the body that collides with the ground. Fore-foot- and mid-foot-strike gaits were probably more common when humans ran barefoot or in minimal shoes, and may protect the feet and lower limbs from some of the impact-related injuries now experienced by a high percentage of runners.

Although the role of shoe constructions on running injury and performance has been widely investigated, systematic reviews on the shoe construction effects on running biomechanics were rarely reported. Therefore, this review focuses on the relevant research studies examining the biomechanical effect of running shoe constructions on reducing running-related injury and optimising performance. Searches of five databases and Footwear Science from January 1994 to September 2018 for related biomechanical studies which investigated running footwear constructions yielded a total of 1260 articles. After duplications were removed and exclusion criteria applied to the titles, abstracts and full text, 63 studies remained and categorised into following constructions: (a) shoe lace, (b) midsole, (c) heel flare, (d) heel-toe drop, (e) minimalist shoes, (f) Masai Barefoot Technologies, (g) heel cup, (h) upper, and (i) bending stiffness. Some running shoe constructions positively affect athletic performance-related and injury-related variables: 1) increasing the stiffness of running shoes at the optimal range can benefit performance-related variables; 2) softer midsoles can reduce impact forces and loading rates; 3) thicker midsoles can provide better cushioning effects and attenuate shock during impacts but may also decrease plantar sensations of a foot; 4) minimalist shoes can improve running economy and increase the cross-sectional area and stiffness of Achilles tendon but it would increase the metatarsophalangeal and ankle joint loading compared to the conventional shoes. While shoe constructions can effectively influence running biomechanics, research on some constructions including shoe lace, heel flare, heel-toe drop, Masai Barefoot Technologies, heel cup, and upper requires further investigation before a viable scientific guideline can be made. Future research is also needed to develop standard testing protocols to determine the optimal stiffness, thickness, and heel-toe drop of running shoes to optimise performance-related variables and prevent running-related injuries.