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Running footwear is continuously being modified and improved; however, running-related overuse injury rates remain high. Nevertheless, novel manufacturing processes enable the production of individualized running shoes that can fit the individual needs of runners, with the potential to reduce injury risk. For this reason, it is essential to investigate functional groups of runners, a collective of runners who respond similarly to a footwear intervention. Therefore, the objective of this study was to develop a framework to identify functional groups based on their individual footwear response regarding injury-specific running-related risk factors for Achilles tendinopathy, Tibial stress fractures, Medial tibial stress syndrome, and Patellofemoral pain syndrome. In this work, we quantified the footwear response patterns of 73 female and male participants when running in three different footwear conditions using unsupervised learning (k -means clustering). For each functional group, we identified the footwear conditions minimizing the injury-specific risk factors. We described differences in the functional groups regarding their running style, anthropometric, footwear perception, and demographics. The results implied that m ost functional groups showed a tendency for a single footwear condition to reduce most biomechanical risk factors for a specific overuse injury. Functional groups often differed in their hip and pelvis kinematics as well as their subjective rating of the footwear conditions. The footwear intervention only partially affected biomechanical risk factors attributed to more proximal joints. Due to its adaptive nature, the framework could be applied to other footwear interventions or performance-related biomechanical variables. [ABSTRACT FROM AUTHOR]

Injury prevention is essential in running due to the risk of overuse injury development. Tailoring running shoes to individual needs may be a promising strategy to reduce this risk. Novel manufacturing processes allow the production of individualised running shoes that incorporate features that meet individual biomechanical and experiential needs. However, specific ways to individualise footwear to reduce injury risk are poorly understood. Therefore, this scoping review provides an overview of (1) footwear design features that have the potential for individualisation; and (2) the literature on the differential responses to footwear design features between selected groups of individuals. These purposes focus exclusively on reducing the risk of overuse injuries. We included studies in the English language on adults that analysed: (1) potential interaction effects between footwear design features and subgroups of runners or covariates (e.g., age, sex) for running-related biomechanical risk factors or injury incidences; (2) footwear comfort perception for a systematically modified footwear design feature. Most of the included articles (n = 107) analysed male runners. Female runners may be more susceptible to footwear-induced changes and overuse injury development; future research should target more heterogonous sampling. Several footwear design features (e.g., midsole characteristics, upper, outsole profile) show potential for individualisation. However, the literature addressing individualised footwear solutions and the potential to reduce biomechanical risk factors is limited. Future studies should leverage more extensive data collections considering relevant covariates and subgroups while systematically modifying isolated footwear design features to inform footwear individualisation. Key points: Individualised footwear bears the potential to alter biomechanics and, subsequently, the individual injury risk profile. Since different footwear modifications modulate risk factors for specific overuse injuries diffently, individualised footwear solutions must be designed for specific overuse injuries by targeting injury-specific biomechanical risk factors. The influence of various footwear modifications on biomechanical risk factors concerning environmental constraints, athlete anthropometry, and experience level has been documented only to a limited extent and requires further research. In addition to minimising biomechanical risk factors, the comfort and fit of the shoe should be considered to design an individually optimal shoe. [ABSTRACT FROM AUTHOR]

While a substantial amount of research concerning footwear for many sports activities has been published, the research on running and distance running has dominated the footwear related literature. The purpose of this review was to describe the origins of footwear research in biomechanics and the relationship of biomechanics to footwear research and design beginning with research conducted in the 1970s up to the year 2000. As a result of the interest in running in the 1960s and 70s, the biomechanics of running shoes became an important consideration for footwear manufacturers and for biomechanics researchers. While some footwear manufacturers developed their own laboratories for research, they also began supporting research in university laboratories. In this review, the technology used for footwear research in the 1970s and 80s is discussed, and how this technology somewhat limited the research capabilities of footwear researchers. These limitations were mainly a result of the data reduction and analysis process. The major foci of footwear research in the early days were: (1) running-related injuries (pronation and impact loading); and (2) running performance. Running-related injuries became an important emphasis as a result of epidemiological studies showing that up to 50% of runners became injured per year and that footwear may be designed to prevent/mitigate these injuries. The effect of running shoes on improving running performance did not garner the same interest as did running-related injuries but certainly, footwear research showed that shoes could be an important factor influencing performance. While the concepts developed in this era have been found to be somewhat controversial, the fact that running shoes were improved with this research during this period is beyond doubt. [ABSTRACT FROM AUTHOR]

This study aimed to compare impact loading between two age groups of preschool children (3–4 and 5–6 years old) and one group of young adults representing mature level of running skill (n = 15 per group). Three-dimensional biomechanical data were collected during running barefoot, in minimalist and running shoes. A two-way mixed ANOVA was performed to assess age and footwear differences in vertical instantaneous loading rate (VILR). An interaction was found in VILR. Older (5–6) preschoolers had 30–31% lower VILR than younger (3–4) (p = 0.012, d = 1.02; p = 0.001, d = 1.18) and adults had 51–77% lower VILR than younger preschoolers (p = 0.001, d = 1.85; p = 0.001, d = 2.82) in minimalist and running shoes, respectively. Additionally, adults had lower VILR than older preschoolers in running shoes (p = 0.001, d = 2.68). No differences were found between older children and adults in barefoot and minimalist shoes. Loading decreased with increasing age, particularly in minimalist and running shoes. Unchanged cadence and running speed did not explain the decrease of VILR during preschool age. The explanation likely underlies in lower limb alignment during footstrike and developmental ontogenetic changes. [ABSTRACT FROM AUTHOR]

For many years, running-related injuries have been studied on surfaces that are flat, smooth and predictable but there are few studies that have reported on injuries in trail running. Therefore, the purpose of this paper was to report on the prevalence of injuries incurred during trail running, the anatomical location most affected by injury, the type of trails and terrains on which injuries most occurred and the type of footwear associated with trail running injuries. A large sample (n = 1016) responded to an online retrospective questionnaire on trail running injuries, the types of trails and terrains on which they ran and the footwear that they used. The sample was determined to represent a range of ages and geographical regions in the United States. We found that 359 respondents reported a trail running injury with 872 injury occurrences with injuries having different frequencies of occurrence. The most commonly reported injury was a rolled or sprained ankle. A significant association was found between runners that sustained a given injury and their preferred trail and terrain types. A large majority (75%) of trail runners wore running footwear specifically designed for trail running. These results suggest that injuries in trail running are different than observed in road running where traumatic injuries to the ankle are more prevalent in trail running and where chronic injuries to the knee prevail in road running. We also noted that trail running injuries were only marginally the result of the type of trails and terrains on which runners most often ran. We did not find any association between the use of footwear specifically designed for trail running and injury risk. [ABSTRACT FROM AUTHOR]

Minimalistic footwear provides adequate toe space, tripod function, improving foot function, muscle activation and stability during walking similarly to barefoot walking. Due to the increasing popularity of this specific footwear, there is a lack of research focusing on general users of minimalistic footwear. Does annual walking in minimalistic footwear affect gait biomechanics? Cross-sectional study involving twenty participants in a minimalistic footwear group with both experience (MFE) and no experience (NMFE). Participants walked in three different conditions (barefoot, minimalistic, and neutral footwear) in the laboratory at normal human walking speed. A significant main effect of groups regardless of footwear conditions show significantly greater values during walking in minimalistic footwear and barefoot in the stride length (p=0.035, p=0.003, respectively), and stride width (p=0.047, p=0.028, respectively) in the NMFE group compared to MFE group. The significant differences in the main effects of footwear regardless of experience were found in stance time (p<0.001), steps per minute (p<0.001), stride length (<0.001), foot adduction in TO (p<0.001), foot eversion angle in IC and TO (p<0.001, p<0.001, respectively), foot progression angle (p<0.001), ankle dorsiflexion angle in IC and TO (p<0.001, p<0.001, respectively), in ankle eversion angle in IC and TO (p<0.001, p<0.001, respectively), knee flexion angle in IC and TO (p<0.001; p<0.001, respectively), and in knee flexion range of motion (p<0.001). Based on our findings, barefoot walking should be used primarily during daily activities if the environment is conducive. Only one year of experience with minimalistic footwear seems insufficient and an intervention should be incorporated to change the gait pattern when transitioning to full minimalistic footwear walking. • Barefoot walking should be used primarily during daily activities when the environment is suitable. • One year of experience with minimalistic footwear seems insufficient to change the gait pattern. • An intervention should be incorporated to full minimalistic footwear walking transitioning. [ABSTRACT FROM AUTHOR]

Quantifying the midsole material characteristics of athletic footwear is a standard task in footwear research and development. Current material testing protocols primarily focus on the determination of cushioning properties of the heel region or the quantification of the midsole properties as one assembly. However, midsoles possess different spatial material properties that have not been quantified from previous methodologies. Therefore, new material testing methods are required to quantify the local material response of athletic footwear. We developed a cyclical force-controlled material testing protocol for the determination of non-homogeneously distributed material stiffness with a high spatial resolution. In five prototype shoes varying in their stiffness distribution, we found that the material properties can be reliably measured across the midsole. Furthermore, we observed a characteristic non-linear material response regardless of the midsole location. We found that the material stiffness increased with an increase of the applied force and that this effect is further intensified by higher testing cycles. Additionally, the obtained midsole stiffness depends on the geometry of the midsole. We explored different approaches to reduce the measurement time of the testing protocol and found that the number of measurements can be reduced by 70% using 2 D-interpolation procedures. Determining the spatial material properties of midsoles needs to be considered to understand foot-shoe interactions. Furthermore, this measurement protocol can be used for quality control within the footwear and can be adapted for considering the effects of different running styles or speeds on ground force application characteristics. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate knee intra‐articular cartilage volume changes after a prolonged running bout in three footwear conditions. Twelve participants performed 75‐minute running bouts in the three footwear conditions. Before and after each running bout, magnetic resonance imaging (MRI) scans were obtained using a high‐resolution 3.0 Tesla MRI. Three‐dimensional reconstruction of the cartilage plates of the patella, the femur, and the tibia was created to quantify cartilage volume change due to the 75‐minute running bout. Three‐dimensional biomechanical data were also collected using an integrated motion capture and force treadmill system. There were no statistically significant differences among shoe conditions for all anatomical regions. However, significant cartilage volume reductions at all anatomical sites were observed after the 75‐minute running bout in each footwear condition. These data suggest that the intra‐articular knee cartilage undergoes a significant reduction in cartilage volume during a prolonged run that may indicate an increase in joint loading. There was a considerable variation in cartilage volume between participants across footwear conditions indicating an individual cartilage volume response to footwear. An individualistic approach to footwear recommendations may help in minimizing this change in cartilage. [ABSTRACT FROM AUTHOR]

The current literature on footwear cushioning and pronation has suggested that there may not be a relationship between chronic injury risk and these parameters based on mixed findings and lack of evidence of an association with prospective injury rates. Since footwear has been designed and developed based on cushioning and pronation, we suggest that we have possibly been on a misguided path in footwear design for the last few decades. Current thought thus implies that a new method of footwear prescription is necessary if we are to guide runners toward appropriate footwear that accommodates their individual biomechanical patterns during running. Based on a series of studies investigating the response of the leg to movement and loading patterns, we developed a novel paradigm based on Nigg's 'preferred movement path'. The assumptions of the 'preferred motion path' were modified in the new method and refined as the 'habitual motion path'. We focused on knee motion in addition to foot and ankle motion since the greatest number of injuries to runners is at the knee. We utilized a kinematic method for developing a calculation to determine the deviation of a runner's joint motion path during running from their habitual motion path. We used this deviation as an index for the individual prescription of an appropriate running shoe. While this new method matches a runner based only on their biomechanics, there are other factors that need to be considered. For example, in footwear selection, the individual's training and injury history in addition to the experience that the runner is seeking from their run must also be considered. [ABSTRACT FROM AUTHOR]

This study investigated whether male runners improve running performance, running economy, ankle plantar flexor strength, and alter running biomechanics and lower limb bone mineral density when gradually transitioning to using minimalist shoes for 100% of weekly running. The study was a planned follow-up of runners (n = 50) who transitioned to minimalist or conventional shoes for 35% of weekly structured training in a previous 6-week randomised controlled trial. In that trial, running performance and economy improved more with minimalist shoes than conventional shoes. Runners in each group were instructed to continue running in their allocated shoe during their own preferred training programme for a further 20 weeks while increasing allocated shoe use to 100% of weekly training. At the 20-week follow-up, minimalist shoes did not affect performance (effect size: 0.19; p = 0.218), running economy (effect size: ≤ 0.24; p ≥ 0.388), stride rate or length (effect size: ≤ 0.12; p ≥ 0.550), foot strike (effect size: ≤ 0.25; p ≥ 0.366), or bone mineral density (effect size: ≤ 0.40; p ≥ 0.319). Minimalist shoes increased plantar flexor strength more than conventional shoes when runners trained with greater mean weekly training distances (shoe*distance interaction: p = 0.036). After greater improvements with minimalist shoes during the initial six weeks of a structured training programme, increasing minimalist shoe use from 35% to 100% over 20 weeks, when runners use their own preferred training programme, did not further improve performance, running economy or alter running biomechanics and lower limb bone mineral density. Minimalist shoes improved plantar flexor strength more than conventional shoes in runners with greater weekly training distances. [ABSTRACT FROM AUTHOR]

Only a few studies have measured the movement of the calcaneus inside the shoe during running, and those that have done so have focused on the frontal plane of motion. This study's objective was to determine the three-dimensional (3D) movement of the calcaneus inside the shoe during running. A secondary objective was to determine if calcaneus movement differs between neutral and support shoes. Ten participants ran at 3.5 m/s in two shoes: a neutral and a support shoe. Right rearfoot kinematics were measured using reflective markers affixed to the shoe heel counter and to the skin of the rearfoot inside the shoe. 3D segment angle ranges of motion were calculated and compared across the shoe heel and calcaneus conditions, and across the two shoe conditions. The movement of the calcaneus compared to the shoe heel was not different in the frontal plane, but was significantly different in the transverse plane, with the calcaneus adducting by 4° more than the shoe heel. The calcaneus also moved significantly more than the shoe in the sagittal plane. Results were similar across the shoe conditions except in the frontal plane where less rearfoot eversion was measured in the support compared to the neutral shoe. The results from this study highlight an opportunity for the development of footwear technologies that can guide calcaneal adduction. Additionally, markers on the shoe heel counter may be appropriate for measuring motion of the foot inside the shoe in the frontal plane, but not the transverse plane. [ABSTRACT FROM PUBLISHER]

Background: Minimalist shoes have been popularized as a safe alternative to conventional running shoes. However, a paucity of research is available investigating the longer-term safety of minimalist shoes. Purpose: To compare running-related pain and injury between minimalist and conventional shoes in trained runners and to investigate interactions between shoe type, body mass, and weekly training distance. Study Design: Randomized clinical trial; Level of evidence, 2. Methods: Sixty-one trained, habitual rearfoot footfall runners (mean ± SD: body mass, 74.6 ± 9.3 kg; weekly training distance, 25 ± 14 km) were randomly allocated to either minimalist or conventional shoes. Runners gradually increased the time spent running in their allocated shoes over 26 weeks. Running-related pain intensity was measured weekly by use of 100-mm visual analog scales. Time to first running-related injury was also assessed. Results: Interactions were found between shoe type and weekly training distance for weekly running-related pain; greater pain was experienced with minimalist shoes (P < .05), and clinically meaningful increases (>10 mm) were noted when the weekly training distance was more than 35 km/wk. Eleven of 30 runners sustained an injury in conventional shoes compared with 16 of 31 runners in minimalist shoes (hazard ratio, 1.64; 95% confidence interval, 0.63-4.27; P = .31). A shoe × body mass interaction was found for time to first running-related injury (P = .01). For runners using minimalist shoes, relative to runners using conventional shoes, the risk of sustaining an injury became more likely with increasing body mass above 71.4 kg, and the risk was moderately increased (hazard ratio, 2.00; 95% confidence interval, 1.10-3.66; P = .02) for runners using minimalist shoes who had a body mass of 85.7 kg. Conclusions: Runners should limit weekly training distance in minimalist shoes to avoid running-related pain. Heavier runners are at greater risk of injury when running in minimalist shoes. [ABSTRACT FROM AUTHOR]

The manner of adapting one's running biomechanics when wearing different footwear designs appears to be individual-specific. Applying the preferred movement path theorem, wearing less than optimal running shoes bears the risk of forcing the joints to leave their preferred path and load unadapted joint areas that might be overused during sport activities. The goal of this article is to introduce a method quantifying a person's biomechanical responsiveness towards footwear, the so-called ‘footwear-related variability’, and to explore corresponding determinants. Eighty-nine participants were tested wearing six different running shoe conditions. They performed isometric strength tests for knee and ankle extensor muscles. Further, anthropometrics, as well as lower extremity kinematics and kinetics during linear running at 3.5 m/s were recorded. Their stance phase normalized waveform patterns of running biomechanical data were analysed by means of the ‘adjusted coefficient of multiple determination’, quantifying how much footwear-induced biomechanical response occurred. The results showed that knee joint-specific footwear-related variability was higher in female participants than in male participants. Strength-generating capacity correlated with some footwear-related variability measures and men were found to be stronger than women. Footwear-related variability appeared to be influenced by the extent of knee adduction, hip inward rotation and ankle outward rotation moment, which are characteristic to distinguish between men's and women's running styles. Anatomical and anthropometric differences between men and women as well as strength capacity disadvantages might make women more susceptible to footwear-induced running biomechanical alterations. Future studies should investigate the relationship between footwear-related variability and overuse injuries, in order to find critical thresholds of footwear-related variability and identify groups of runners that need to be specifically targeted with injury preventing measures. [ABSTRACT FROM AUTHOR]

Introduction: Research on minimal footwear hasn’t utilised runners who habitually wear typical training footwear and therefore what adjustments to running patterns are made and how quickly they occur is unknown. Purpose: The purposes of this study were: 1) to investigate how kinematic patterns are adjusted while running barefoot and in footwear with systematic changes in shock attenuating material; and 2) to determine the time it takes for adjustments to occur when little is known about the footwear condition before running commences. Methods: Ten male heel-toe runners performed treadmill runs of 6 minutes in thin, medium, and thick footwear and barefoot. Participants ran immediately after putting shoes on to limit information about each footwear condition. Standard kinematics and acceleration signals were captured. Repeated measures analysis of variance (ANOVA) was utilised (p < 0.05) to determine differences across footwear conditions and time. Results: The foot was flatter at touchdown (due to a more vertical leg segment and more plantar flexion), the knee had reduced excursion, and stance times, eversion and tibial rotation excursions were greater in the thin footwear or when barefoot. Several variables were adjusted from the initial steps to later in the run. Acceleration standard deviations had more variability during initial steps than immediately following. Discussion: Many kinematic adjustments agreed with previous works though participants did not adopt a midfoot or forefoot strike pattern. Experimental design and participant knowledge and experiences may be contributing to discrepancies in footstrike patterns. Runners sensitive to eversion and tibial internal rotation should use caution when barefoot or in minimal footwear. Finally, the greatest kinematic changes occurred within the first six to eight steps, however more subtle changes continued throughout the six minute run. [ABSTRACT FROM AUTHOR]

The role of the extrinsic foot muscles in controlling the foot during the period of eversion is not well understood. The major extrinsic muscles are: tibialis anterior, tibialis posterior, gastrocnemius, peroneals, soleus and extensor digitorum longus. The purpose of this study was to investigate the role of the extrinsic foot muscles in running in response to perturbations caused by neutral, varus and valgus wedged footwear. Twelve healthy, college aged males ran with a heel-toe footfall pattern at 3.6 m s-1± 5% in the specially constructed footwear. Three-dimensional kinematic and kinetic data were collected and used in a Newton-Euler inverse dynamics calculation to determine 3D joint moments. We used a static optimization approach which employed the ankle joint moments and a minimization cost function to determine the individual muscle forces. Of the six extrinsic foot muscles, only the extensor digitorum longus (dorsiflexor) and the peroneals (evertor) resulted in force differences among footwear conditions. Neither of these muscles act to resist the eversion action. There were differences in the muscle force between wedge conditions in the extensor digitorum longus, peroneals and the tibialis anterior and posterior. Again, none of these muscles resist eversion. These results indicate that the extrinsic foot muscles experience small alterations as a result of the wedged footwear during the support phase of running. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Running shoes are designed specifically for different foot types in order to reduce injuries. Running in the correct footwear matched for foot type may have a greater influence on mechanics when runners become exerted. Therefore, the purpose of this study was to evaluate changes in kinematics and kinetics over the course of a prolonged run when low (LA) and high (HA) arched runners wear motion control and cushioning shoes. Methods: Twelve HA and 12 LA recreational runners were recruited for this study. Subjects ran in a motion control (MC) and cushion trainer (CT) shoe. Lower extremity kinematics and tibial accelerometry were collected while the runners ran at a self-selected training pace. The data were analyzed using a two-way (footwear×time) repeated measures ANOVA (p =0.05) for each arch type. Results: Low arched runners: Peak tibial internal rotation decreased in the MC shoe and was increased in the CT over the course of the prolonged run. However, no interactions or main effects were noted for peak eversion or eversion excursion. High arched runners: No shoe by time interaction was observed for tibial shock. However, there was a main effect for shoe, with lower tibial shock associated with the CT shoe. Conclusion: In LA runners, MC shoes decreased tibial internal rotation compared to CT shoes over the course of a prolonged run. In HA runners, running in the CT shoes reduced tibial shock compared to the MC shoes. [Copyright &y& Elsevier]

Background: Running shoes are designed to accommodate various arch types to reduce the risk of lower extremity injuries sustained during running. Yet little is known about the biomechanical changes of running in the recommended footwear that may allow for a reduction in injuries. Purpose: To evaluate the effects of motion control and cushion trainer shoes on running mechanics in low- and high-arched runners. Study Design: Controlled laboratory study. Methods: Twenty high-arched and 20 low-arched recreational runners (>10 miles per week) were recruited for the study. Three-dimensional kinematic and kinetics were collected as subjects ran at 3.5 ms-1 ± 5% along a 25-m runway. The motion control shoe evaluated was the New Balance 1122, and the cushioning shoe evaluated was the New Balance 1022. Repeated-measures analyses of variance were used to determine if low- and high-arched runners responded differently to motion control and cushion trainer shoes. Results: A significant interaction was observed in the instantaneous loading rate such that the low-arched runners had a lower instantaneous loading rate in the motion control condition, and the high-arched runners had a lower instantaneous loading rate in the cushion trainer condition. Significant main effects for shoe were observed for peak positive tibial acceleration, peak-to-peak tibial acceleration, mean loading rate, peak eversion, and eversion excursion. Conclusion: These results suggest that motion control shoes control rearfoot motion better than do cushion trainer shoes. In addition, cushion trainer shoes attenuate shock better than motion control shoes do. However, with the exception of instantaneous loading rate, these benefits do not differ between arch type. Clinical Relevance: Running footwear recommendations should be based on an individual's running mechanics. If a mechanical analysis is not available, footwear recommendations can be based empirically on the individual's arch type. [ABSTRACT FROM AUTHOR]

Supplemental digital content is available in the text. Introduction: The purpose of this study was to compare leg, sagittal plane knee and ankle, and frontal plane ankle stiffness over the course of a prolonged treadmill run in neutral and stability footwear. Methods: Thirteen male habitual rearfoot runners completed two biomechanical testing sessions in which they ran for 21 min at their preferred running speed in a neutral shoe, then changed either into the same neutral shoe or a stability shoe and ran a further 21 min on a force-instrumented treadmill. Three-dimensional kinematics and kinetics were recorded at the beginning and end of each 21-min interval. Results: No differences were observed in leg stiffness between footwear conditions throughout the run (P > 0.05). Knee stiffness increased during the first 21 min (P = 0.009), whereas ankle stiffness reduced at minute 21 (P = 0.004) and minute 44 (P = 0.006). These changes were modulated by an increase in ankle joint compliance and knee joint moments. No differences were observed between footwear conditions for leg and sagittal plane lower extremity joint stiffness (P > 0.05). During the second half of the run, frontal plane ankle stiffness increased in the stability shoe but decreased in the neutral shoe (P = 0.019), attributed to reduced eversion range of motion caused by the added medial post. Conclusions: These results suggest that over the course of a prolonged treadmill run, shock attenuation strategies change, which may affect the knee joint. [ABSTRACT FROM AUTHOR]

This study investigated whether male runners improve running performance, running economy, ankle plantar flexor strength, and alter running biomechanics and lower limb bone mineral density when gradually transitioning to using minimalist shoes for 100% of weekly running. The study was a planned follow-up of runners (n = 50) who transitioned to minimalist or conventional shoes for 35% of weekly structured training in a previous 6-week randomised controlled trial. In that trial, running performance and economy improved more with minimalist shoes than conventional shoes. Runners in each group were instructed to continue running in their allocated shoe during their own preferred training programme for a further 20 weeks while increasing allocated shoe use to 100% of weekly training. At the 20-week follow-up, minimalist shoes did not affect performance (effect size: 0.19; p = 0.218), running economy (effect size: ≤ 0.24; p ≥ 0.388), stride rate or length (effect size: ≤ 0.12; p ≥ 0.550), foot strike (effect size: ≤ 0.25; p ≥ 0.366), or bone mineral density (effect size: ≤ 0.40; p ≥ 0.319). Minimalist shoes increased plantar flexor strength more than conventional shoes when runners trained with greater mean weekly training distances (shoe*distance interaction: p = 0.036). After greater improvements with minimalist shoes during the initial six weeks of a structured training programme, increasing minimalist shoe use from 35% to 100% over 20 weeks, when runners use their own preferred training programme, did not further improve performance, running economy or alter running biomechanics and lower limb bone mineral density. Minimalist shoes improved plantar flexor strength more than conventional shoes in runners with greater weekly training distances. [ABSTRACT FROM AUTHOR]

The presence of long-range correlations (self-similarity) in the stride-to-stride fluctuations in running stride interval has been used as an indicator of a healthy adaptable system. Changes to footfall patterns when running with minimalist shoes could cause a less adaptable running gait. The purpose of this study was to investigate stride interval variability and the degree of self-similarity of stride interval in runners wearing minimalist and conventional footwear. Twenty-six trained habitual rearfoot footfall runners, unaccustomed to running in minimalist footwear, performed 6-min sub-maximal treadmill running bouts at 11, 13 and 15 km·h(-1) in minimalist and conventional shoes. Force sensitive resistors were placed in the shoes to quantify stride interval (time between successive foot contacts). Footfall position, stride interval mean and coefficient of variation (CV), were used to assess performance as a function of shoe type. Long-range correlations of stride interval were assessed using detrended fluctuation analysis (α). Mean stride interval was 1-1.3% shorter (P=0.02) and 27% of runners adopted a midfoot footfall (MFF) in the minimalist shoe. There was a significant shoe effect on α and shoe*speed*footfall interaction effect on CV (P<0.05). Runners that adopted a MFF in minimalist shoes, displayed reduced long-range correlations (P<0.05) and CV (P<0.06) in their running stride interval at the 15 km·h(-1) speed. The reduced variability and self-similarity observed for runners that changed to a MFF in the minimalist shoe may be suggestive of a system that is less flexible and more prone to injury. [ABSTRACT FROM AUTHOR]