The effects of systematically altered footwear features on biomechanics, injury, performance, and preference in runners of different skill level: a systematic review

Does policy that provides choice in athletic footwear affect musculoskeletal injury risk in US Coast Guard recruits?

INTRODUCTION

Musculoskeletal injuries (MSKIs) are ubiquitous during initial entry military training, with overuse injuries the most common. A common injury mechanism is running, an activity that is integral to US Coast Guard (USCG) training and a requirement for graduation. The purpose of this study was to assess the effects of a policy that allowed for athletic footwear choice on risk of lower quarter MSKI in USCG recruits.

METHODS

A retrospective cohort study was performed that included 1230 recruits (1040 men, 190 women) who trained under a policy that allowed self-selection of athletic footwear and 2951 recruits (2329 men, 622 women) who trained under a policy that mandated use of prescribed uniform athletic shoes and served as controls. Demographic data and physical performance were derived from administrative records. Injury data were abstracted from a medical tracking database. Unadjusted risk calculations and multivariable logistic regression assessing the effects of group, age, sex, height, body mass and 2.4 km run times on MSKI were performed.

RESULTS

Ankle-foot, leg, knee and lumbopelvic-hip complex injuries were ubiquitous in both groups (experimental: 13.13 per 1000 person-weeks; control: 11.69 per 1000 person-weeks). Group was not a significant factor for any of the injuries assessed in either the unadjusted or adjusted analysis, despite widespread reports of pain (58.6%), perceived injury attribution (15.7%), perceived deleterious effect on performance (25.3%), general dissatisfaction (46.3%) and intended discontinuance of use following graduation (87.7%).

CONCLUSION

MSKI continues to be a major source of morbidity in the recruit training population. The policy that allowed USCG recruits to self-select athletic footwear did not decrease or increase the risk of MSKI. While regulations pertaining to footwear choice did not influence injury outcomes, there was general dissatisfaction with the prescribed uniform athletic footwear conveyed by the recruits and widespread reports of discomfort, perceived deleterious effects from wear and intended discontinued use following training completion.

Influence of Torsional Stiffness in Badminton Footwear on Lower Limb Biomechanics

Torsional stiffness of athletic footwear plays a crucial role in preventing injury and improving sports performance. Yet, there is a lack of research focused on the biomechanical effect of torsional stiffness in badminton shoes. This study aimed to comprehensively investigate the influence of three different levels of torsional stiffness in badminton shoes on biomechanical characteristics, sports performance, and injury risk in badminton players. Fifteen male players, aged 22.8 ± 1.96 years, participated in the study, performing badminton-specific tasks, including forehand clear stroke [left foot (FCL) and right foot (FCR)], 45-degree sidestep cutting (45C), and consecutive vertical jumps (CVJ). The tasks were conducted wearing badminton shoes of torsional stiffness measured with Shore D hardness 50, 60, and 70 (referred to as 50D, 60D, and 70D, respectively). The primary biomechanical parameters included ankle, knee, and MTP joint kinematics, ankle and knee joint moments, peak ground reaction forces, joint range of motion (ROM), and stance time. A one-way repeated measures ANOVA was employed for normally distributed data and Friedman tests for non-normally distributed data. The 70D shoe exhibited the highest ankle dorsiflexion and lowest ankle inversion peak angles during 45C task. The 60D shoe showed significantly lower knee abduction angle and coronal motions compared to the 50D and 70D shoes. Increased torsional stiffness reduced stance time in the FCR task. No significant differences were observed in anterior-posterior and medial-lateral ground reaction forces (GRF). However, the 70D shoe demonstrated higher vertical GRF than the 50D shoe while performing the FCR task, particularly during 70% - 75% of stance. Findings from this study revealed the significant role of torsional stiffness in reducing injury risk and optimizing performance during badminton tasks, indicating that shoes with an intermediate level of stiffness (60D) could provide a beneficial balance between flexibility and stability. These findings may provide practical references in guiding future badminton shoe research and development. Further research is necessary to explore the long-term effects of altering stiffness, considering factors such as athletic levels and foot morphology, to understand of the influence of torsional stiffness on motion biomechanics and injury prevalence in badminton-specific tasks.

Biomechanical effects of foot orthoses on jump landing performance: A systematic review

Jumping is involved in a wide range of sports and activities, and foot orthoses (FO) are suggested to enhance performance and prevent injury. The aim of this systematic review was to investigate whether using FO with different modifications affects jump landing biomechanics and improves performance in healthy individuals. The search strategy included 7 databases that identified 19 studies. The study quality was evaluated using a modified Downs and Black index. The primary outcome measures were joint kinematics, kinetics, muscle activity, vertical jump height, and horizontal jump distance. Our findings indicated that incorporating arch support with a rearfoot post and softer forefoot region into FO may improve several biomechanical variables during jump landing activities. Improvements in vertical ground reaction force loading rates, knee and ankle kinematics, and muscle cocontraction during jumping with FO could enhance jumping performance. In addition, improvements in hip, knee, ankle, and tibial kinematics and vertical ground reaction force loading rates during landing could reduce impact forces and related injuries. Although a limited number of studies have addressed the effects of FO on vertical jump height and horizontal jump distance, inserting such FO inside shoes with optimum bending stiffness could facilitate jumping performance. A rigorous exploration of the effect and mechanism of FO designs on jumping performance could benefit jumping-related activities and prevent ankle and knee injuries.

Biomechanical Tradeoffs in Foot Function From Variations in Shoe Design

There is debate and confusion over how to evaluate the biomechanical effects of running shoe design. Here, we use an evolutionary perspective to analyze how key design features of running shoes alter the evolved biomechanics of the foot, creating a range of tradeoffs in force production and transmission that may affect performance and vulnerability to injury.

Identification of subject-specific responses to footwear during running

Placing a stronger focus on subject-specific responses to footwear may lead to a better functional understanding of footwear's effect on running and its influence on comfort perception, performance, and pathogenesis of injuries. We investigated subject-specific responses to different footwear conditions within ground reaction force (GRF) data during running using a machine learning-based approach. We conducted our investigation in three steps, guided by the following hypotheses: (I) For each subject x footwear combination, unique GRF patterns can be identified. (II) For each subject, unique GRF characteristics can be identified across footwear conditions. (III) For each footwear condition, unique GRF characteristics can be identified across subjects. Thirty male subjects ran ten times at their preferred (self-selected) speed on a level and approximately 15 m long runway in four footwear conditions (barefoot and three standardised running shoes). We recorded three-dimensional GRFs for one right-foot stance phase per running trial and classified the GRFs using support vector machines. The highest median prediction accuracy of 96.2% was found for the subject x footwear classification (hypothesis I). Across footwear conditions, subjects could be discriminated with a median prediction accuracy of 80.0%. Across subjects, footwear conditions could be discriminated with a median prediction accuracy of 87.8%. Our results suggest that, during running, responses to footwear are unique to each subject and footwear design. As a result, considering subject-specific responses can contribute to a more differentiated functional understanding of footwear effects. Incorporating holistic analyses of biomechanical data is auspicious for the evaluation of (subject-specific) footwear effects, as unique interactions between subjects and footwear manifest in versatile ways. The applied machine learning methods have demonstrated their great potential to fathom subject-specific responses when evaluating and recommending footwear.

Measurement and reporting of footwear characteristics in running biomechanics: A systematic search and narrative synthesis of contemporary research methods

This review aimed to synthesise the methods for assessing and reporting footwear characteristics among studies evaluating the effect of footwear on running biomechanics. Electronic searches of Scopus®, EBSCO, PubMed®, ScienceDirect®, and Web of Science® were performed to identify original research articles of the effect of running footwear on running biomechanics published from 1^st January 2015 to 7^th October 2020. Risk of bias among included studies was not assessed. Results were presented via narrative synthesis. Eligible studies compared the effect of two or more footwear conditions in adult runners on a biomechanical parameter. Eighty-seven articles were included and data from 242 individual footwear were extracted. Predominantly, studies reported footwear taxonomy (i.e., classification) and manufacturer information, however omitted detail regarding the technical specifications of running footwear and did not use validated footwear reporting tools. There is inconsistency among contemporary studies in the methods by which footwear characteristics are assessed and reported. These findings point towards a need for consensus regarding the reporting of these characteristics within biomechanical studies to facilitate the conduct of systematic reviews and meta-analyses pertaining to the effect of running footwear on running biomechanics.

A systematic review of the effect of running shoes on running economy, performance and biomechanics: analysis by brand and model

This systematic review aims to synthesise the effects of current shoe models in each shoe category and their specific features on running economy, performance and biomechanics. Electronic databases such as Web of Science, SPORTDiscuss, PubMed and Scopus were used to identify studies from 2015 to date. Due to the existing lack of consensus to define running shoes, only studies that specified the shoe brand and models used to assess their effect over runners with a certain level of fitness and training routine were included. Quality assessment of cross-sectional and intervention studies was conducted by three independent raters using a modified version of the Quality Index and the PEDro scale, respectively. A total of 36 articles were finally included, involving the analysis of 61 different shoe models over 10 different topics (i.e., running economy, running performance, spatiotemporal parameters, ground reaction forces, joint stiffness, achilles tendon, plantar pressure, tibiofemoral load, foot strike pattern and joint coordination). With this review, runners and practitioners in the field that are concerned about selecting a suitable shoe for performance, training, or injury prevention functionality have clear information about the effects of the current shoe models and their specific features.

Effects of Footwear Selection on Plantar Pressure and Neuromuscular Characteristics during Jump Rope Training

This study examined what footwear type influenced plantar pressure and lower extremity muscle activations in jump rope training. Ten healthy physical-education graduate students participated in this study. The biomechanical parameters during the jump rope training were collected by an AMTI force platform, a Novel Pedar-X insole and a wireless electromyography (EMG) system. The results of the force platform indicate that vertical ground reaction force (vGRF) and contact time were much higher in the one-leg landing (both p = 0.001). The GRF, GRF (BW) and Lat MF pressure were significantly greater in the one-leg landing (p = 0.018, 0.013 and 0.027); the pressure of the Lat MF and H area were significantly greater in the volleyball shoe (p = 0.025, 0.031); the pressure of the Mid FF and Lat FF area were significantly greater in the jumping shoe (p = 0.005, 0.042). No significant difference in EMG was found between footwear and landing conditions. In summary, the running shoe and jumping shoe might be a better choice for people who exercise. However, the running shoe is recommended for people when both jumping and running are required.

Evaluating footwear "in the wild": Examining wrap and lace trail shoe closures during trail running

Trail running participation has grown over the last two decades. As a result, there have been an increasing number of studies examining the sport. Despite these increases, there is a lack of understanding regarding the effects of footwear on trail running biomechanics in ecologically valid conditions. The purpose of our study was to evaluate how a Wrap vs. Lace closure (on the same shoe) impacts running biomechanics on a trail. Thirty subjects ran a trail loop in each shoe while wearing a global positioning system (GPS) watch, heart rate monitor, inertial measurement units (IMUs), and plantar pressure insoles. The Wrap closure reduced peak foot eversion velocity (measured via IMU), which has been associated with fit. The Wrap closure also increased heel contact area, which is also associated with fit. This increase may be associated with the subjective preference for the Wrap. Lastly, runners had a small but significant increase in running speed in the Wrap shoe with no differences in heart rate nor subjective exertion. In total, the Wrap closure fit better than the Lace closure on a variety of terrain. This study demonstrates the feasibility of detecting meaningful biomechanical differences between footwear features in the wild using statistical tools and study design. Evaluating footwear in ecologically valid environments often creates additional variance in the data. This variance should not be treated as noise; instead, it is critical to capture this additional variance and challenges of ecologically valid terrain if we hope to use biomechanics to impact the development of new products.

Finite element modelling for footwear design and evaluation: A systematic scoping review

Finite element modelling has become an efficient tool for an in-depth understanding of the foot, footwear biomechanics and footwear optimization. The aim of this paper was to provide an updated overview in relation to the footwear finite element (FE) analysis published since 2000. The paper will attempt to outline the main challenges and research gaps that need confronting in the further development of realistic and accurate models for clinical and industrial applications. English databases of the Web of Science and PubMed were used to search (‘finite element’ OR ‘FEA’ OR ‘computational model’) AND (‘shoe’ OR ‘footwear’) until 16 December 2021. Articles that conducted FE analyses on the whole foot and footwear structures were included in this review. Twelve articles met the eligibility criteria, and were grouped into three categories for further analysis, (1) finite element modelling of the foot and high-heeled shoes; (2) finite element modelling of the foot and boot; (3) finite element modelling of the foot and sports shoe. Even though most of the existing foot-shoe FE analyses were performed under certain simplifications and assumptions, they have provided essential contributions in identifying the mechanical response of the foot in casual or athletic footwear. Further to this, the results have provided information in relation to optimizing footwear design to enhance functional performance. Nevertheless, further simulations still present several challenges, including reliable data information for geometry reconstruction, the balance between accurate details and computational cost, accurate representations of material properties, realistic boundary and loading conditions, and thorough model validation. In addition, some research gaps in terms of the coverage of footwear design, the consideration of insole/orthosis and socks, and the internal and external validity of the FE design should be fully covered.

Effects of Shoe Midfoot Bending Stiffness on Multi-Segment Foot Kinematics and Ground Reaction Force during Heel-Toe Running

We investigated how midfoot stiffness of running shoes influences foot segment kinematics and ground reaction force (GRF) during heel-toe running. Nineteen male rearfoot strike runners performed overground heel-toe running at 3.3 m/s when wearing shoes with different midfoot bending stiffnesses (low, medium, and high) in a randomized order. A synchronized motion capture system (200 Hz) and force plate (1000 Hz) were used to collect the foot-marker trajectories and GRF data. Foot kinematics, including rearfoot-lab, midfoot-rearfoot, forefoot-rearfoot, and forefoot-midfoot interactions, and kinetics, including GRF characteristics, were analyzed. Our results indicated that high midfoot stiffness shoes reduced the forefoot-rearfoot range of motion (mean ± SD; high stiffness, 7.8 ± 2.0°, low stiffness, 8.7 ± 2.1°; p < 0.05) and forefoot-midfoot range of motion (mean ± SD; high stiffness, 4.2 ± 1.1°, medium stiffness, 4.6 ± 0.9°; p < 0.05) in the frontal plane. No differences were found in the GRF characteristics among the shoe conditions. These findings suggest that an increase in midsole stiffness only in the midfoot region can reduce intersegmental foot medial-lateral movements during the stance phase of running. This may further decrease the tension of the foot muscles and tendons during prolonged exercises.

Running shoes for preventing lower limb running injuries in adults

BACKGROUND

Lower-limb running injuries are common. Running shoes have been proposed as one means of reducing injury risk. However, there is uncertainty as to how effective running shoes are for the prevention of injury. It is also unclear how the effects of different characteristics of running shoes prevent injury.

OBJECTIVES

To assess the effects (benefits and harms) of running shoes for preventing lower-limb running injuries in adult runners.

SEARCH METHODS

We searched the following databases: CENTRAL, MEDLINE, Embase, AMED, CINAHL Plus and SPORTDiscus plus trial registers WHO ICTRP and ClinicalTrials.gov. We also searched additional sources for published and unpublished trials. The date of the search was June 2021.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs involving runners or military personnel in basic training that either compared a) a running shoe with a non-running shoe; b) different types of running shoes (minimalist, neutral/cushioned, motion control, stability, soft midsole, hard midsole); or c) footwear recommended and selected on foot posture versus footwear not recommended and not selected on foot posture for preventing lower-limb running injuries. Our primary outcomes were number of people sustaining a lower-limb running injury and number of lower-limb running injuries. Our secondary outcomes were number of runners who failed to return to running or their previous level of running, runner satisfaction with footwear, adverse events other than musculoskeletal injuries, and number of runners requiring hospital admission or surgery, or both, for musculoskeletal injury or adverse event.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility and performed data extraction and risk of bias assessment. The certainty of the included evidence was assessed using GRADE methodology.

MAIN RESULTS

We included 12 trials in the analysis which included a total of 11,240 participants, in trials that lasted from 6 to 26 weeks and were carried out in North America, Europe, Australia and South Africa. Most of the evidence was low or very low certainty as it was not possible to blind runners to their allocated running shoe, there was variation in the definition of an injury and characteristics of footwear, and there were too few studies for most comparisons. We did not find any trials that compared running shoes with non-running shoes. Neutral/cushioned versus minimalist (5 studies, 766 participants) Neutral/cushioned shoes may make little or no difference to the number of runners sustaining a lower-limb running injuries when compared with minimalist shoes (low-certainty evidence) (risk ratio (RR) 0.77, 95% confidence interval (CI) 0.59 to 1.01). One trial reported that 67% and 92% of runners were satisfied with their neutral/cushioned or minimalist running shoes, respectively (RR 0.73, 95% CI 0.47 to 1.12). Another trial reported mean satisfaction scores ranged from 4.0 to 4.3 in the neutral/ cushioned group and 3.6 to 3.9 in the minimalist running shoe group out of a total of 5. Hence neutral/cushioned running shoes may make little or no difference to runner satisfaction with footwear (low-certainty evidence). Motion control versus neutral / cushioned (2 studies, 421 participants) It is uncertain whether or not motion control shoes reduce the number of runners sustaining a lower-limb running injuries when compared with neutral / cushioned shoes because the quality of the evidence has been assessed as very low certainty (RR 0.92, 95% CI 0.30 to 2.81). Soft midsole versus hard midsole (2 studies, 1095 participants) Soft midsole shoes may make little or no difference to the number of runners sustaining a lower-limb running injuries when compared with hard midsole shoes (low-certainty of evidence) (RR 0.82, 95% CI 0.61 to 1.10). Stability versus neutral / cushioned (1 study, 57 participants) It is uncertain whether or not stability shoes reduce the number of runners sustaining a lower-limb running injuries when compared with neutral/cushioned shoes because the quality of the evidence has been assessed as very low certainty (RR 0.49, 95% CI 0.18 to 1.31). Motion control versus stability (1 study, 56 participants) It is uncertain whether or not motion control shoes reduce the number of runners sustaining a lower-limb running injuries when compared with stability shoes because the quality of the evidence has been assessed as very low certainty (RR 3.47, 95% CI 1.43 to 8.40). Running shoes prescribed and selected on foot posture (3 studies, 7203 participants) There was no evidence that running shoes prescribed based on static foot posture reduced the number of injuries compared with those who received a shoe not prescribed based on foot posture in military recruits (Rate Ratio 1.03, 95% CI 0.94 to 1.13). Subgroup analysis confirmed these findings were consistent between males and females. Therefore, prescribing running shoes and selecting on foot posture probably makes little or no difference to lower-limb running injuries (moderate-certainty evidence). Data were not available for all other review outcomes.

AUTHORS' CONCLUSIONS

Most evidence demonstrates no reduction in lower-limb running injuries in adults when comparing different types of running shoes. Overall, the certainty of the evidence determining whether different types of running shoes influence running injury rates was very low to low, and as such we are uncertain as to the true effects of different types of running shoes upon injury rates. There is no evidence that prescribing footwear based on foot type reduces running-related lower-limb injures in adults. The evidence for this comparison was rated as moderate and as such we can have more certainty when interpreting these findings. However, all three trials included in this comparison used military populations and as such the findings may differ in recreational runners.  Future researchers should develop a consensus definition of running shoe design to help standardise classification. The definition of a running injury should also be used consistently and confirmed via health practitioners. More researchers should consider a RCT design to increase the evidence in this area. Lastly, future work should look to explore the influence of different types or running shoes upon injury rates in specific subgroups.

Validation of the RunScribe inertial measurement unit for walking gait measurement

Introduction

The use of portable gait measurement systems in research is appealing to collect real-world data at low-cost, low participant burden, and without requirement for dedicated lab space. Most commercially available inertial measurement units (IMU’s) designed for running only capture temporospatial data, the ability to capture biomechanics data such as shock and motion metrics with the RunScribe IMU makes it the closest to a lab alternative. The RunScribe system has been validated in running, however, is yet to be validated for walking.

Method

Qualisys motion capture, AMTI force plates, and Delsys Trigno accelerometers were used as gold standard lab measures for comparison against the RunScribe IMU. Twenty participants completed 10 footsteps per foot (20 total) measured by both systems simultaneously. Variables for validation included: Vertical Ground reaction force (GRF), instantaneous GRF rate, pronation excursion, pronation velocity, total shock, impact force, braking force. Interclass correlation (ICC) was used to determine agreement between the measurement systems, mean differences were used to evaluate group level accuracy.

Results

ICC results showed moderate agreement between measurement systems when both limbs were averaged. The greatest agreement was seen for GRF rate, pronation excursion, and pronation velocity (ICC = 0.627, 0.616, 0.539), low agreement was seen for GRF, total shock, impact shock, braking shock (ICC = 0.269, 0.351, 0.244, 0.180). However mean differences show the greatest level of accuracy for GRF, GRF rate, and impact shock.

Discussion

Results show mixed agreement between the RunScribe and gold standard lab measures, and varied agreement across left and right limbs. Kinematic variables showed the greatest agreement, however GRF had the lowest relative mean difference for group results. The results show acceptable levels of agreement for most variables, however further work must be done to assess the repeatability and sensitivity of the RunScribe to be applied within areas such as footwear testing and gait retraining protocols.

2021 ISB World Athletics Award for Biomechanics: The Subtalar Joint Maintains "Spring-Like" Function While Running in Footwear That Perturbs Foot Pronation

Humans have the remarkable ability to run over variable terrains. During locomotion, however, humans are unstable in the mediolateral direction and this instability must be controlled actively-a goal that could be achieved in more ways than one. Walking research indicates that the subtalar joint absorbs energy in early stance and returns it in late stance, an attribute that is credited to the tibialis posterior muscle-tendon unit. The purpose of this study was to determine how humans (n = 11) adapt to mediolateral perturbations induced by custom-made 3D-printed "footwear" that either enhanced or reduced pronation of the subtalar joint (modeled as motion in 3 planes) while running (3 m/s). In all conditions, the subtalar joint absorbed energy (ie, negative mechanical work) in early stance followed by an immediate return of energy (ie, positive mechanical work) in late stance, demonstrating a "spring-like" behavior. These effects increased and decreased in footwear conditions that enhanced or reduced pronation (P ≤ .05), respectively. Of the recorded muscles, the tibialis posterior (P ≤ .05) appeared to actively change its activation in concert with the changes in joint energetics. We suggest that the "spring-like" behavior of the subtalar joint may be an inherent function that enables the lower limb to respond to mediolateral instabilities during running.

Gender and leg-dominance differences in shoe properties and foot injuries in badminton: a cross-sectional survey

Background

While the roles of injury prevention and performance enhancement have increasingly been investigated for badminton footwear, there is a lack of research on gender-specific badminton footwear. The purpose of this study was to examine the gender differences in footwear demands and foot injuries in badminton.

Methods

The study was a cross-sectional survey, in which 326 recreational badminton players were recruited. The questionnaire was divided into four sections enquiring about the characteristics of (1) participant profiles, (2) importance of shoe properties (3) shoe complaints (4) and pain or discomfort in different foot regions. The Mann-Whitney U test and Wilcoxon Signed Ranks test were performed to determine the differences between genders and the differences between leg dominance, respectively. The significance level was set at 0.05.

Results

Both males and females rated shoe fit as the most important features, followed by the overall comfort and injury protection. Females considered the shoe forefoot cushioning, comfort, breathability and colour as more important compared with the other properties, which showed distinct pattern differences from males. The shoe problem results indicated that plantar pain of the non-dominant foot was considered the most commonly reported footwear problem by both males and females. The problem of excessive arch-support on the dominant and non-dominant sides of male participants was significantly higher than females (p < 0.05). Occasional pain or frequent pain were mainly distributed in the forefoot, followed by the rearfoot and midfoot regions.

Conclusion

There were small differences in footwear demand between the dominant and non-dominant sides, but several differences existed between females and males. The results from gender differences suggested that female shoes prefer a specific shoe last for better fit, rather than a modified version of male shoes. In the future, the design of badminton shoes should consider footwear demands and foot discomfort profiles in respective male and female badminton players.

Running Injury Paradigms and Their Influence on Footwear Design Features and Runner Assessment Methods: A Focused Review to Advance Evidence-Based Practice for Running Medicine Clinicians

Many runners seek health professional advice regarding footwear recommendations to reduce injury risk. Unfortunately, many clinicians, as well as runners, have ideas about how to select running footwear that are not scientifically supported. This is likely because much of the research on running footwear has not been highly accessible outside of the technical footwear research circle. Therefore, the purpose of this narrative review is to update clinical readers on the state of the science for assessing runners and recommending running footwear that facilitate the goals of the runner. We begin with a review of basic footwear construction and the features thought to influence biomechanics relevant to the running medicine practitioner. Subsequently, we review the four main paradigms that have driven footwear design and recommendation with respect to injury risk reduction: Pronation Control, Impact Force Modification, Habitual Joint (Motion) Path, and Comfort Filter. We find that evidence in support of any paradigm is generally limited. In the absence of a clearly supported paradigm, we propose that in general clinicians should recommend footwear that is lightweight, comfortable, and has minimal pronation control technology. We further encourage clinicians to arm themselves with the basic understanding of the known effects of specific footwear features on biomechanics in order to better recommend footwear on a patient-by-patient basis.

Footwear comfort: a systematic search and narrative synthesis of the literature

OBJECTIVE

To provide a narrative synthesis of the research literature pertaining to footwear comfort, including definitions, measurement scales, footwear design features, and physiological and psychological factors.

METHODS

A systematic search was conducted which yielded 101 manuscripts. The most relevant manuscripts were selected based on the predetermined subheadings of the review (definitions, measurement scales, footwear design features, and physiological and psychological factors). A narrative synthesis of the findings of the included studies was undertaken.

RESULTS

The available evidence is highly fragmented and incorporates a wide range of study designs, participants, and assessment approaches, making it challenging to draw strong conclusions or implications for clinical practice. However, it can be broadly concluded that (i) simple visual analog scales may provide a reliable overall assessment of comfort, (ii) well-fitted, lightweight shoes with soft midsoles and curved rocker-soles are generally perceived to be most comfortable, and (iii) the influence of sole flexibility, shoe microclimate and insoles is less clear and likely to be more specific to the population, setting and task being performed.

CONCLUSION

Footwear comfort is a complex and multifaceted concept that is influenced not only by structural and functional aspects of shoe design, but also task requirements and anatomical and physiological differences between individuals. Further research is required to delineate the contribution of specific shoe features more clearly, and to better understand the interaction between footwear features and individual physiological attributes.

Current application of continuous relative phase in running and jumping studies: A systematic review

BACKGROUND

Continuous relative phase (CRP) has gained popularity to assess movement performances in recent decades.

RESEARCH QUESTION

The application and interpretation of CRP in common movements such as running and jumping are still unclear.

METHODS

This systematic review summarized the current applications, methodology, parameters of interest, and interpretations of CRP variables in running and jumping. Reviewed articles were found in five databases from January 1999 to December 2020, and 1613 records were obtained. After applying selection criteria and analysis of study quality to titles, abstracts, and full texts, 38 articles were identified for subsequent review.

RESULTS

Twenty-eight reviewed articles relating to running were found to compare the coordination among pathological gait, footwear designs, running speed, gender, age, running level, fatigue state, and treadmill effect. In addition, ten reviewed articles relating to jumping were found to compare the coordination among different types of jump (e.g., squat jump coordination, countermovement jump, single leg jump) and insole effect.

SIGNIFICANCE

The CRP and its variability (CRPv) are two common variables to describe the changes and differences of coordination patterns, respectively. These reviewed articles suggest that CRP tools are effective to assess the coordination and performances in running and jumping, as these values are related to external (environment/equipment) and internal (self-biological) changes. In the future, studying higher-order analysis of movement patterns using CRP tools can provide meaningful interpretation of movement behavior.

Sex-Specific Hip Movement Is Correlated With Pelvis and Upper Body Rotation During Running

There is a sex bias for common overuse running injuries that are associated with sex-specific hip kinematics. Gait retraining programs aimed at altering hip kinematics may be more efficient if they incorporated an understanding of how hip kinematics are correlated with the movement of the remaining body segments. We applied a principal component analysis to structure the whole-body running kinematics of 23 runners (12 ♀) into k = 12 principal movements (PM_k), describing correlated patterns of upper and lower body movements. We compared the time-dependent movement amplitudes with respect to each PM_k between males and females using a waveform analysis and interpreted our findings according to stick figure animations. The movement amplitudes of two PMs (PM₆ and PM₈) showed statistically significant effects of "sex," which were independent of running speed. According to PM₈, females showed more hip adduction, which correlated with increased transverse rotation of the pelvis and upper body compared to men. We propose that increased hip adduction and upper body rotation in female runners may be a strategy to compensate for a less efficient arm and upper body swing compared to men. Gait interventions aimed at reducing hip adduction and running-related injuries in female runners should consider instructions for both upper and lower body to maximize training efficacy.

Shoe feature recommendations for different running levels: A Delphi study

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