A consensus definition and rating scale for minimalist shoes

Return to Running after Knee Arthroplasty: A Case Report

Individuals who have undergone knee arthroplasty may still want to run, but no study has reported a progression to guide patients and clinicians. The objective of this case report is to document the process of returning to running after total knee arthroplasty with a 1-year follow-up. The client was a 55-year-old woman, former triathlete, who underwent unilateral knee arthroplasty 1 year prior to consultation. She alternated slow running with walking and increased based on symptoms. She also performed a lower limb exercise programme. The client was a low-impact forefoot striker, ran with a high step rate and wore minimalist shoes. During the 1-year follow-up, she reported no knee pain but experienced minor episodes of calf strains. Towards the end, her comfort level was best when alternating running and walking for 3-4 km, three to four times per week. The client reached her objective of finishing an olympic distance triathlon. The exercise programme also helped to increase lower limb strength and improve physical performance. This case report suggests that it is possible to return to running up to 1 year after total knee arthroplasty. Future research should study bigger samples and monitor implant wear to provide better guidance to patients and physiotherapists.

Acute physiological, biomechanical, and perceptual responses of runners wearing downward-curved carbon fiber insoles

In a randomized controlled cross-over study ten male runners (26.7 ± 4.9 years; recent 5-km time: 18:37 ± 1:07 min:s) performed an incremental treadmill test (ITT) and a 3-km time trial (3-km TT) on a treadmill while wearing either carbon fiber insoles with downwards curvature or insoles made of butyl rubber (control condition) in light road racing shoes (Saucony Fastwitch 9). Oxygen uptake, respiratory exchange ratio, heart rate, blood lactate concentration, stride frequency, stride length and time to exhaustion were assessed during ITT. After ITT, all runners rated their perceived exertion, perceived shoe comfort and perceived shoe performance. Running time, heart rate, blood lactate levels, stride frequency and stride length were recorded during, and shoe comfort and shoe performance after, the 3-km TT. All parameters obtained during or after the ITT did not differ between the two conditions [range: p = 0.188 to 0.948 (alpha value: 0.05); Cohen's d = 0.021 to 0.479] despite the rating of shoe comfort showing better scores for the control insoles (p = 0.001; d = -1.646). All parameters during and after the 3-km TT showed no differences (p = 0.200 to 1.000; d = 0.000 to 0.501) between both conditions except for shoe comfort showing better scores for control insoles (p = 0.017; d = -0.919). Running with carbon fiber insoles with downwards curvature did not change running performance or any submaximal or maximal physiological or biomechanical parameter and perceived exertion compared to control condition. Shoe comfort is impaired while running with carbon fiber insoles. Wearing carbon fiber insoles with downwards curvature during treadmill running is not beneficial when compared to running with control insoles.

The Immediate Biomechanical Effects of a Flat, Flexible School Shoe in Adolescents with Patellofemoral Pain

INTRODUCTION

Treatment options for adolescent patellofemoral pain (PFP) are limited. School footwear might be a suitable intervention to modulate patellofemoral joint (PFJ) loads in adolescents with PFP. This study examined the immediate effects of a flat, flexible school shoe compared with a traditional school shoe on knee joint kinematics and kinetics, and PFJ reaction force during walking and running in adolescents with PFP.

METHODS

A total of 28 adolescents (12 female, 16 male; mean ± SD age, 14.3 ± 1.7 yr) with PFP walked and ran on an instrumented treadmill in two randomly ordered conditions: (i) flat, flexible school shoe and (ii) traditional school shoe. Three-dimensional marker trajectory and ground reaction force data were sampled at 250 and 1000 Hz, respectively. Continuous ankle and knee joint angles and moments, PFJ reaction force, and ankle power were compared between conditions using one-dimensional statistical parametric mapping paired t -tests ( α < 0.05).

RESULTS

Walking in the flat, flexible school shoe resulted in a significant reduction in knee flexion (15%-35% of gait cycle, P < 0.001), knee extension moment (15%-40% of gait cycle, P < 0.001), and PFJ reaction force (15%-40% of gait cycle, P < 0.001) compared with the traditional school shoe. During running, knee flexion (10%-33% of gait cycle, P < 0.001), knee extension moment (15%-25% of gait cycle, P < 0.001), and PFJ reaction force (15%-25% of gait cycle, P < 0.001) were lower when wearing the flat, flexible school shoe compared with the traditional school shoe.

CONCLUSIONS

PFJ reaction force is reduced when adolescents walk and run in a flat, flexible school shoe compared with a traditional school shoe. Flat, flexible school shoes may be an effective intervention to modulate biomechanical factors related to PFP.

Time to stability of treadmill running kinematics in novel footwear with different midsole thickness

Running studies, particularly those examining footwear effects, commonly use warm-up or familiarization periods prior to testing. There is no consensus for how long these familiarization periods should be to ensure stable running kinematics prior to experimental testing in novel footwear. The aim of this study was to assess the time to stability of kinematic variables during treadmill running in novel compared to habitual neutral cushion footwear in distance runners. A cross-sectional analysis of 15 distance runners (seven women, eight men) during 10-minute treadmill running bouts in minimal, neutral cushion, and maximal cushioned footwear was conducted while lower extremity kinematics were recorded for 10 s at the end of each minute. Test-retest intra-class correlation coefficients (ICC, 3, k) were used to detect time to stability in cadence, vertical oscillation, peak dorsiflexion angle, peak eversion angle, and peak knee flexion angle. All kinematic variables were stabilized within two to three minutes (ICC < 0.90) and the type of novel footwear did not influence time to stability. These findings indicate that a two to three minute, ∼310-540 steps, depending on running cadence, familiarization period, regardless of footwear novelty, is sufficient for stabilization of these kinematic variables during treadmill running.

Assessing the effects of foot strike patterns and shoe types on the control of leg length and orientation in running

This research investigates the stabilization of leg length and orientation during the landing phase of running, examining the effects of different footwear and foot strike patterns. Analyzing kinematic data from twenty male long-distance runners, both rearfoot and forefoot strikers, we utilized the Uncontrolled Manifold approach to assess stability. Findings reveal that both leg length and orientation are indeed stabilized during landing, challenging the hypothesis that rearfoot strikers exhibit less variance in deviations than forefoot strikers, and that increased footwear assistance would reduce these deviations. Surprisingly, footwear with a lower minimalist index enhanced post-landing stability, suggesting that cushioning contributes to both force dissipation and leg length stability. The study indicates that both foot strike patterns are capable of effectively reducing task-relevant variance, with no inherent restriction on flexibility for rearfoot strikers. However, there is an indication of potential reliance on footwear for stability. These insights advance our understanding of the biomechanics of running, highlighting the role of footwear in stabilizing leg length and orientation, which has significant implications for running efficiency and injury prevention.

Effects of Minimalist vs. Traditional Running Shoes on Abdominal Lumbopelvic Muscle Activity in Women Running at Different Speeds: A Randomized Cross-Over Clinical Trial

This study aimed to investigate if the characteristics of different running shoes could influence intra-abdominal pressure during running. A single-centre, randomized, prospective cross-over clinical trial was performed measuring activity patterns of internal oblique (IO), lumbar erector (LE), and gluteus maximus (GM) muscles in healthy women when running with minimalist shoes (MS). Participants were randomly allocated into two-sequence (MS/TS or TS/MS) treadmill running at six, nine, and eleven km/h. The surface electromyographic activity of IO, LE, and GM muscles were recorded while running. A repeated measures ANOVA explored the interaction effects of three-muscle x three speeds x two shoes. Significance was set at p ≤ 0.05. Fifty-one healthy nulliparous women (mean age: 26.55 ± 5.11 years; body mass index: 21.29 ± 2.07 Kg/m2) were included. Our findings revealed lower activations of the LE compared to the internal oblique IO and GM, irrespective of running speed and footwear used. Electromyographic activation significantly increased with higher running speeds (p < 0.001) for all muscles, regardless of the type of footwear. Although electromyographic records with MS consistently showed higher values than those with TS, the differences were not statistically significant for all muscles at all speeds. Our results indicate that electromyographic activation patterns vary according to the muscle group, exhibiting higher values with increased running speed. No significant differences were observed between MS and TS.

Maximalist Shoes: Separating Science From Hype

One of the most discussed but misunderstood topics in foot and ankle is shoe wear choices and the purported benefits of each type of shoe versus their actual scientific advantages. All foot and ankle care providers should be familiar with the various shoe wear types available to patients to improve their overall foot health. Recently, mainstream popularity and media coverage of maximalist shoes has created increased interest in the science and potential clinical benefits of maximalist shoes. The purpose of this review is to present the current biomechanical evidence of maximalist shoes and to help inform the foot and ankle community of their potential therapeutic applications.Levels of Evidence: Level V.

The Effect of Using Marathon Shoes or Track Spikes on Neuromuscular Fatigue caused by a Long-distance Track Training Session

This study aims to compare the effect of the Nike ZoomX Dragonfly track spikes and the Nike ZoomX VaporflyNext% 2 marathon shoes on the fatigue manifestations present over and after a long-distance track training session. Thirteen highly trained athletes completed two training sessions (i. e., 9- and 3-minute time trials with complete recovery) with the aforementioned footwear models. The pace, ground contact time, and stride length were measured over the time trials, and maximal countermovement jumps were performed previously and after the training session. The results revealed that, although there was no significant interaction in the pace distribution (p≥0.072), athletes tend to be only able to increase the pace at the last lap with the marathon shoes (5.4 meters [-3.7 to 14.5 meters]) meanwhile with the track spikes it further decreased (-3.1 meters [-9.8 to 3.6 meters]). A reduced ground contact time over the session (p=0.025) and a tendency toward increasing stride length (p=0.09) in the last time trial were observed. The significant interaction on the countermovement jump height (p=0.023; Track spikes: -5.60%; Marathon shoes: 0.61%) also indicates that footwear influences the resulted allostatic load.

Effect of surface inclination on vertical loading rate and footstrike pattern in trail and road runners

Trail runners have been reported to be more injury prone than road runners. Limited past studies have examined the difference in the running biomechanics between the two groups of runners. More importantly, the effect of surface inclination has not been fully investigated. Hence, this study examined the effect of surface inclination on running biomechanics in trail and road runners. Twenty trails and 20 road runners were recruited in this study. Trail runners appeared to be more experienced and had longer training distance per week (p < 0.001) compared to road runners. All participants ran at a self-selected pace on an instrumented treadmill in three inclination conditions (i.e., level, +10% uphill and -10% downhill) in a random order. Vertical average loading rate (VALR), vertical instantaneous loading rate (VILR) and footstrike angle (FSA) were measured using established methods. Trail runners experienced greater VILR (p = 0.039, Cohen's d = 2.9) with a greater FSA (p = 0.002, Cohen's d = 1.1) during downhill running than road runners. No significant differences in VALR, VILR and FSA were found between the two groups during level and uphill running. Our findings provide potential biomechanical rationale to explain a higher injury incidence among trail runners.

Flat flexible school shoes for adolescents with patellofemoral pain: a randomised, assessor-blinded, parallel-group feasibility trial

Objectives

To determine the feasibility of conducting a large-scale randomised controlled trial on the efficacy of flat, flexible school footwear versus traditional school footwear in adolescents (aged 12-18 years) with patellofemoral pain (PFP).

Methods

Adolescents with PFP were recruited for this study. Participants were randomised to wear either a (1) flat, flexible school shoe or (2) a traditional school shoe. Participants wore the shoes as per school requirements for 12 weeks. Feasibility was assessed by (1) adherence to allocated shoe wear of ≥75% of total weekly school shoe wear time (recorded through weekly log sheets), (2) a recruitment rate of one participant per fortnight and (3) a dropout rate of ≤ 20%. Descriptive statistics were used for feasibility outcomes.

Results

24 adolescents (15 men, 9 women, mean (SD) age 14.3 (1.7) years) participated in this study. Two participants (8%) were lost to follow-up. The recruitment rate was 1.7 participants per fortnight. 11 of 12 participants (91%) in the flat flexible shoe group and 9 of 10 participants (90%) in the traditional shoe group met the minimum adherence for shoe wear. Mean weekly shoe wear was 20 (7.6) and 21 (4.5) hours per week in the flat, flexible, and traditional shoe groups, respectively.

Conclusion

Our results indicate that progression to a full-scale randomised controlled trial is feasible based on the current protocol. A full-scale randomised controlled trial powered to detect estimates of treatment efficacy using flat, flexible school shoes versus traditional school shoes is warranted and will guide evidence-based management of adolescent PFP.

Foot and Ankle Muscle Isometric Strength in Nonrearfoot Compared With Rearfoot Endurance Runners

Background

Transitioning to a forefoot strike pattern can be used to manage running-related knee injuries. However, adopting a nonrearfoot strike induces a higher load on foot and ankle structures than rearfoot strike. Sufficient foot muscle strength is also necessary to prevent excessive longitudinal arch (LA) deformation when running with nonrearfoot strike. The aim of this study was to investigate the potential differences in foot-ankle muscle strength between RF and NRF runners.

Methods

A cross-sectional study including 40 RF and 40 NRF runners was conducted. The foot posture and the maximal voluntary isometric strength (MVIS) of 6 foot-ankle muscles were measured. The footstrike pattern was determined using a 2-D camera during a self-paced run on a treadmill.

Results

NRF had higher MVIS for ankle plantar flexor (+12.5%, P = .015), ankle dorsiflexor (+17.7%, P = .01), hallux flexor (+11%, P = .04), and lesser toe flexor (+20.8%, P = .0031). We found a small positive correlation between MVIS of ankle plantar flexor with MVIS of hallux flexor (r = 0.26; P = .01) and lesser toe flexor (r = 0.28; P = .01).

Conclusion

In this cross-sectional study, we found that NRF runners on average have a higher MVIS of hallux and lesser toe flexor compared with RF runners. NRF runners also have a higher MVIS of ankle plantar flexor and dorsiflexor than RF runners. We found only a small correlation between ankle plantar flexor and foot muscle strength.

Level of Evidence

Level III, case-control study.

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.

Effect of Footwear Versus Barefoot on Double-Leg Jump-Landing and Jump Height Measures: A Randomized Cross-Over Study

Background

Assessing individuals in their own athletic footwear in clinics is common, but can affect movement, performance, and clinical measures.

Purpose

The aim was to compare overall Landing Error Scoring System (LESS) scores, injury risk categorization, specific LESS errors, and jump heights between habitual athletic footwear and barefoot conditions.

Study design

Randomized cross-over laboratory study.

Methods

Eighty healthy individuals (55% male) completed the LESS following standard procedures (i.e., land from a 30-cm box to a distance of 50% of body height and then jump upwards maximally). Participants performed the LESS three times in two randomized conditions: footwear and barefoot. LESS data were extracted from 2D videos to compare group-level mean LESS scores, group-level and individual-level injury risk categorization (5-error threshold), specific landing errors, and jump heights between conditions.

Results

LESS scores were significantly greater (0.3 errors, p=0.022) and jump heights were significantly lower (0.6 cm, p=0.029) in footwear than barefoot, but differences were trivial (d = 0.18 and -0.07, respectively) and not clinically meaningful. Although the number of high injury-risk participants was not statistically different at a group level (p=1.000); 27 individuals (33.8%) exhibited a clinically meaningful difference between conditions of one error or more in LESS score, categorization was inconsistent for 16.3% of individuals, and four of the 17 landing errors significantly differed between conditions.

Conclusion

At a group level, habitual athletic footwear does not meaningfully influence LESS scores, risk categorization, or jump height. At an individual level, footwear can meaningfully affect LESS scores, risk categorization, and alter landing strategies. Use of consistent protocol and footwear is advised for assessing movement patterns and injury risk from the LESS given the unknown predictive value of this test barefoot.

Level of Evidence

Level 3.©The Author(s).

Electromyographic Activity of the Pelvic Floor Muscles and Internal Oblique Muscles in Women during Running with Traditional and Minimalist Shoes: A Cross-Over Clinical Trial

The study aimed to investigate the effects of footwear on the electromyographic (EMG) activity of pelvic floor muscles (PFMs) and internal oblique (IO) muscles during running at different speeds. The study also aimed to explore the correlation between EMG activity of PFMs and IO muscles and participants' morphological characteristics. Ten nulliparous female runners were included in the study. The participants ran for 90 s at speeds of 9, 11, and 13 km/h wearing both traditional and minimalist shoes. EMG outcomes were presented as a percentage of maximum voluntary contraction (%MVC). Comparative analysis was conducted using the Wilcoxon rank test. Correlational analysis was performed using the Rho-Spearman correlation coefficient. The %MVC for the IO muscles was significantly lower when using minimalist shoes compared to traditional shoes (p = 0.04). No statistically significant differences were found for the PFMs (p > 0.05). The study also observed large correlations between age and %MVC of the PFMs and IO muscles (rho = -0.64; p = 0.04). Minimalist shoes decreased the activity of IO muscles in female runners. However, no significant differences in EMG activity of PFMs were found when comparing traditional and minimalist footwear. The long-term effects of minimalist footwear on EMG activity of PFMs and IO muscles, as well as their relationship to morphological characteristics, require further investigation.

Effect of Footwear Type on Biomechanical Risk Factors for Knee Osteoarthritis

BACKGROUND

Regular walking in different types of footwear may increase the mediolateral shear force, knee adduction moment, or vertical ground-reaction forces that could increase the risk of early development of knee osteoarthritis (OA).

PURPOSE

To compare kinematic and kinetic parameters that could affect the development of knee OA in 3 footwear conditions.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 40 asymptomatic participants performed walking trials in the laboratory at self-selected walking speeds under barefoot (BF), minimalistic (MF), and neutral (NF) footwear conditions. Knee joint parameters were described using discrete point values, and continuous curves were evaluated using statistical parametric mapping. A 3 × 1 repeated-measures analysis of variance was used to determine the main effect of footwear for both discrete and continuous data. To compare differences between footwear conditions, a post hoc paired t test was used.

RESULTS

Discrete point analyses showed a significantly greater knee power in NF compared with MF and BF in the weight absorption phase (P < .001 for both). Statistical parametric mapping analysis indicated a significantly greater knee angle in the sagittal plane at the end of the propulsive phase in BF compared with NF and MF (P = .043). Knee joint moment was significantly greater in the propulsive phase for the sagittal (P = .038) and frontal planes (P = .035) in BF compared with NF and MF and in the absorption phase in the sagittal plane (P = .034) in BF compared with MF and NF. A significant main effect of footwear was found for anteroposterior (propulsion, ↑MF, NF, ↓BF [P = .008]; absorption, ↑BF, MF, ↓NF [P = .001]), mediolateral (propulsion, ↑MF, NF, ↓BF [P = .005]; absorption, ↑NF, MF, ↓BF [P = .044]), and vertical (propulsion, ↑NF, BF, ↓MF [P = .001]; absorption, ↑MF, BF, ↓NF [P < .001]) ground-reaction forces. Knee power showed a significant main effect of footwear (absorption, ↑NF, MF, ↓BF [P = .015]; propulsion, ↑MF, NF, ↓BF [P = .039]).

CONCLUSION

Walking in MF without sufficient accommodation affected kinetic and kinematic parameters and could increase the risk of early development of knee OA.

[The influence of footwear on the human gait]

The development of individual gait and running patterns is influenced by internal (anatomical, anthropometric) and external (activity-related, environmental) factors. The predominantly used rearfoot running style is mainly attributed to the use of cushioned shoes, although from an anthropological perspective running barefoot, and thus running forefoot, is considered to be more natural. Numerous studies have shown a long-term influence of habitual footwear use on foot morphology, running biomechanics and basic motor skills. It has further been shown that an acute change in footwear, e.g. by running barefoot, immediately changes kinematics and vertical load parameters. However, to date, there is no strong evidence for an influence of habitual footwear use or footstrike patterns on the prevalence of injuries or physical complaints.

Effects of supportive and minimalist footwear on standing balance and walking stability in older women

BACKGROUND

Footwear has been shown to influence balance and is an important consideration in relation to the prevention of falls. However, it remains unclear as to what type of footwear is most beneficial for balance in older people: sturdy, supportive footwear, or minimalist footwear to maximise plantar sensory input. The objectives of this study were therefore to compare standing balance and walking stability in older women wearing these two footwear styles, and to investigate participants' perceptions in relation to comfort, ease of use and fit.

METHODS

Older women (n = 20) aged 66 to 82 years (mean 73.4, SD 3.9) performed a series of laboratory tests of standing balance (eyes open and closed on floor and foam rubber mat, near tandem standing) and walking stability (treadmill, level and irregular surface) using a wearable sensor motion analysis system. Participants were tested wearing supportive footwear (incorporating design features to improve balance) and minimalist footwear. Perceptions of the footwear were documented using structured questionnaires.

RESULTS

There were no statistically significant differences in balance performance between the supportive and minimalist footwear. Participants perceived the supportive footwear to be significantly more attractive to self and others, easier to put on and off but heavier compared to the minimalist footwear. Overall comfort was similar between the footwear conditions, although the supportive footwear was reported to be significantly more comfortable in the heel, arch height, heel cup, heel width and forefoot width regions. Eighteen participants (90%) reported that they felt more stable in the supportive footwear and 17 (85%) reported that they would consider wearing them to reduce their risk of falling.

CONCLUSION

Balance performance and walking stability were similar in supportive footwear designed to reduce the risk of falling and minimalist footwear, although participants preferred the supportive footwear in relation to aesthetics, ease of use, comfort and perceived stability. Prospective studies are now required to ascertain the longer-term advantages and disadvantages of these footwear styles on comfort and stability in older people.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry. ACTRN12622001257752p, 20/9/2022 (prospectively registered).

Adolescents running in conventional running shoes have lower vertical instantaneous loading rates but greater asymmetry than running barefoot or in partial-minimal shoes

Footwear may moderate the transiently heightened asymmetry in lower limb loading associated with peak growth in adolescence during running. This repeated-measures study compared the magnitude and symmetry of peak vertical ground reaction force and instantaneous loading rates (VILRs) in adolescents during barefoot and shod running. Ten adolescents (age, 10.6 ± 1.7 years) ran at self-selected speed (1.7 ± 0.3 m/s) on an instrumented treadmill under three counter-balanced conditions; barefoot and shod with partial-minimal and conventional running shoes. All participants were within one year of their estimated peak height velocity based on sex-specific regression equations. Foot-strike patterns, peak vertical ground reaction force and VILRs were recorded during 20 seconds of steady-state running. Symmetry of ground reaction forces was assessed using the symmetry index. Repeated-measures ANOVAs were used to compare conditions (α=.05). Adolescents used a rearfoot foot-strike pattern during barefoot and shod running. Use of conventional shoes resulted in a lower VILR (P < .05, dz = 0.9), but higher VILR asymmetry (P < .05) than running barefoot (dz = 1.5) or in partial-minimal shoes (dz = 1.6). Conventional running shoes result in a lower VILR than running unshod or in partial-minimal shoes but may have the unintended consequence of increasing VILR asymmetry. The findings may have implications for performance, musculoskeletal development and injury in adolescents.

Transitioning to Barefoot Running Using a Minimalist Shoe Intermediary: A Prospective Cohort Study

OBJECTIVES

The objectives of this study are, first, to investigate the probability of runners successfully transitioning from running in a traditional shoe to barefoot. Second, to identify prognostic indicators of failure of transition to barefoot running.

METHODS

Over 20 wk, 76 healthy runners (female, 40; age, 35.04 yr [SD, 8.9 yr]; body weight, 69.9 kg [SD 13.4 kg]) attempted to transition from running in traditional shoes to running barefoot. A minimalist shoe was used as an intermediary. Participants ran for 4 wk exclusively in provided traditional shoes followed by 4 wk of transitioning to minimalist shoes. This process was repeated to transition to barefoot running. Participants were followed up until they withdrew from the study or successfully transitioned to running barefoot. A survival analysis examined the weeks of successful transition. Along with sex and age, baseline measures of traditional shoe overall comfort, footstrike pattern, midfoot width mobility and plantar foot pressure pain threshold were examined as prognostic variables for failure to transition using Cox regression.

RESULTS

The cumulative probability of successful transition to running barefoot was 70.8% (95% confidence interval [CI], 61%-83%). The primary footwear-related reason for withdrawal was pain, primarily in the foot ( n = 7), two runners had confirmed injuries. Runners exhibiting a rearfoot strike pattern and higher midfoot width mobility were more likely to fail to transition (hazard ratios [HR], 4.02; 95% CI, 1.33-12.16 and HR, 1.22; 95% CI, 1.05-1.42).

CONCLUSIONS

Most runners who wish to run barefoot will be able to transition. Our study indicates that there may be biomechanical and anatomical characteristics that are prognostic of failing to transition when using a 20-wk transition period and an intermediary minimalist shoe. Whether a different transition process increases the probability of a success remains to be seen.

Do biomechanical foot-based interventions reduce patellofemoral joint loads in adults with and without patellofemoral pain or osteoarthritis? A systematic review and meta-analysis

OBJECTIVE

To evaluate the effects of biomechanical foot-based interventions (eg, footwear, insoles, taping and bracing on the foot) on patellofemoral loads during walking, running or walking and running combined in adults with and without patellofemoral pain or osteoarthritis.

DESIGN

Systematic review with meta-analysis.

DATA SOURCES

MEDLINE, CINAHL, SPORTdiscus, Embase and CENTRAL.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

English-language studies that assessed effects of biomechanical foot-based interventions on peak patellofemoral joint loads, quantified by patellofemoral joint pressure, reaction force or knee flexion moment during gait, in people with or without patellofemoral pain or osteoarthritis.

RESULTS

We identified 22 footwear and 11 insole studies (participant n=578). Pooled analyses indicated low-certainty evidence that minimalist footwear leads to a small reduction in peak patellofemoral joint loads compared with conventional footwear during running only (standardised mean difference (SMD) (95% CI) = -0.40 (-0.68 to -0.11)). Low-certainty evidence indicated that medial support insoles do not alter patellofemoral joint loads during walking (SMD (95% CI) = -0.08 (-0.42 to 0.27)) or running (SMD (95% CI) = 0.11 (-0.17 to 0.39)). Very low-certainty evidence indicated rocker-soled shoes have no effect on patellofemoral joint loads during walking and running combined (SMD (95% CI) = 0.37) (-0.06 to 0.79)).

CONCLUSION

Minimalist footwear may reduce peak patellofemoral joint loads slightly compared with conventional footwear during running only. Medial support insoles may not alter patellofemoral joint loads during walking or running and the evidence is very uncertain about the effect of rocker-soled shoes during walking and running combined. Clinicians aiming to reduce patellofemoral joint loads during running in people with patellofemoral pain or osteoarthritis may consider minimalist 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.

Effect of Running-Induced Fatigue on Tibial Acceleration and the Role of Lower Limb Muscle Strength, Power, and Endurance

BACKGROUND

High-impact loads have been linked with running injuries. Fatigue has been proposed to increase impact loads, but this relationship has not been rigorously examined, including the associated role of muscle strength, power, and endurance.

PURPOSE

This study aimed to investigate the effect of fatigue on impact loading in runners and the role of muscle function in mediating changes in impact loading with fatigue.

METHODS

Twenty-eight trained endurance runners performed a fixed-intensity time to exhaustion test at 85% of V̇O 2max . Tibial accelerations were measured using leg-mounted inertial measurement units and sampled every minute until volitional exhaustion. Tests of lower limb muscle strength, power, and endurance included maximal isometric strength (soleus, knee extensors, and knee flexors), single leg hop for distance, and the one leg rise test. Changes in peak tibial acceleration (PTA, g ) were compared between time points throughout the run (0%, 25%, 50%, 75%, and 100%). Associations between the change in PTA and lower limb muscle function tests were assessed (Spearman's rho [ rs ]).

RESULTS

PTA increased over the duration of the fatiguing run. Compared with baseline (0%) (mean ± SD, 9.1 g ± 1.6 g ), there was a significant increase at 75% (9.9 g ± 1.7 g , P = 0.001) and 100% (10.1 g ± 1.8 g , P < 0.001), with no change at 25% (9.6 g ± 1.6 g , P = 0.142) or 50% (9.7 g ± 1.7 g , P = 0.053). Relationships between change in PTA and muscle function tests were weak and not statistically significant ( rs = -0.153 to 0.142, all P > 0.05).

CONCLUSIONS

Peak axial tibial acceleration increased throughout a fixed-intensity run to exhaustion. The change in PTA was not related to performance in lower limb muscle function tests.

The influence of running shoes on familiarization time for treadmill running biomechanics evaluation

This study investigated treadmill familiarisation time in different shoe conditions by comparing lower limb consecutive kinematics waveforms using a trend symmetry method to calculate trend symmetry index, range amplitude ratio and range offset. Eighteen young adults (26.6 ± 3.3 years, 7 females) completed three 10-minute running trials at their preferred running speed (2.30 ± 0.17 m/s) on a treadmill with three shoe conditions (i.e., usual, minimalist and maximalist shoes) in a random order. Sagittal lower limb kinematic data were recorded using inertial measurement units. The results showed that sagittal-plane kinematic waveforms in the hip, knee and ankle remained consistent (trend symmetry > 0.95) without extreme excursions (range amplitude ratio ≈ 1) over 10 minutes within each testing shoe condition. Significant time × shoe interaction effect was observed in range offset (i.e., absolute differences in the average degree of kinematic waveforms between consecutive minutes) at ankle (p = 0.029, ŋ_p² = 0.096) and knee (p = 0.002, ŋ_p² = 0.126). Post-hoc analysis suggested that running with novel shoes required a shorter time to achieve stable lower limb kinematics (2 to 3 minutes) compared with usual shoes (7 minutes). In conclusion, young healthy adults need up to 3 and 7 minutes to familiarise to the treadmill when running at their preferred speed with their novel and usual running shoes.

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.

Running gait modifications can lead to immediate reductions in patellofemoral pain

Gait modifications are commonly advocated to decrease knee forces and pain in runners with patellofemoral pain (PFP). However, it remains unknown if clinicians can expect immediate effects on symptoms. Our objectives were (1) to compare the immediate effects of gait modifications on pain and kinetics of runners with PFP; (2) to compare kinetic changes in responders and non-responders; and (3) to compare the effects between rearfoot strikers (RFS) and non-RFS. Sixty-eight runners with PFP (42 women, 26 men) ran normally on a treadmill before testing six modifications: 1- increase step rate by 10%; 2- 180 steps per minute; 3- decrease step rate by 10%; 4- forefoot striking; 5- heel striking; 6- running softer. Overall, there were more responders (pain decreased ≥1/10 compared with normal gait) during forefoot striking and increasing step rate by 10% (both 35%). Responders showed greater reductions in peak patellofemoral joint force than non-responders during all conditions except heel striking. When compared with non-RFS, RFS reduced peak patellofemoral joint force in a significant manner (P < 0.001) during forefoot striking (partial η ² = 0.452) and running softer (partial η ² = 0.302). Increasing step rate by 10% reduced peak patellofemoral joint force in both RFS and non-RFS. Forty-two percent of symptomatic runners reported immediate reductions in pain during ≥1 modification, and 28% had reduced pain during ≥3 modifications. Gait modifications leading to decreased patellofemoral joint forces may be associated with immediate pain reductions in runners with PFP. Other mechanisms may be involved, given that some runners reported decreased symptoms regardless of kinetic changes.

Age differences in running biomechanics during footstrike between preschool children and adults

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.

Effects of Running in Minimal and Conventional Footwear on Medial Tibiofemoral Cartilage Failure Probability in Habitual and Non-Habitual Users

This study examined the effects of minimal and conventional running footwear on medial tibiofemoral cartilage mechanics and longitudinal failure probability. The current investigation examined twenty males who habitually ran in minimal footwear and 20 males who habitually ran in conventional footwear. Kinematic data during overground running were collected using a motion-capture system and ground reaction forces using a force plate. Medial tibiofemoral loading was examined using musculoskeletal simulation and cartilage failure probability via probabilistic modelling. In habitual minimal footwear users, peak medial tibiofemoral cartilage force, stress and strain were significantly greater in conventional (force = 7.43 BW, stress = 5.12 MPa and strain = 0.30), compared to minimal footwear (force = 7.11 BW, stress 4.65 MPa and strain = 0.28), though no significant differences in these parameters were evident in non-habitual minimal footwear users (conventional: force = 7.50 BW, stress = 5.05 MPa and strain = 0.30; minimal: force = 7.40 BW, stress = 4.77 MPa and strain = 0.29). However, in both habitual and non-habitual minimal footwear users, the probability of medial tibiofemoral cartilage failure was significantly greater in conventional (habitual = 47.19% and non-habitual = 50.00%) compared to minimal footwear (habitual = 33.18% and non-habitual = 32.81%) users. The observations from this investigation show that compared to minimal footwear, conventional footwear appears to have a negative influence on medial tibiofemoral cartilage health.

Effects of minimalist shoes on pelvic floor activity in nulliparous women during running at different velocities: a randomized cross-over clinical trial

In the last decade, minimalist shoes have gained popularity as an alternative to traditional shoes. The aim of the present study was to determine the short-term effects of minimalist shoes in femur range of motion (ROM) and cadence. The secondary objectives were the assessment of the electromyographic activity of the pelvic floor muscles (PFM) in nulliparous women. A randomized, prospective cross-over clinical trial design was used for the study. A total of 51 participants were randomly allocated into a two-sequence crossover design (AB/BA crossover design). Femur ROM, cadence and PFM activity were recorded. The femur ROM at 6 km/h was greater with the minimalist shoes by 1.62 degrees than with the traditional ones (p = 0.001). There was a main effect of the type of shoe (p = 0.015) systematically observing a higher running cadence with the minimalist shoe compared to the traditional one. Electromyographic activity of the PFM revealed significant differences for 11 km/h for the total average (p = 0.027) and the minimum peaks at 9 km/h (p = 0.011) and 11 km/h (p = 0.048) for the minimalist shoe with respect to the traditional shoes. Minimalist shoes produce immediate effects on the biomechanical variables of running. An increase was observed in the femur ROM at 6 km/h and in the cadence at 11 km/h with the use of minimalist shoes. The use of minimalist shoes increased the electromyographic activation of the PFM in the minimum peaks at speeds of 9 and 11 km/h and in the total average at speeds of 11 km/h compared to the traditional shoe.

Variations in the Thickness of the Plantar Fascia After Training Based in Training Race. A Pilot Study

Plantar fascia (PF) is a connective tissue made up of mostly type 1 collagen that is subjected to constant loads. This study evaluated the effect of continuous running on tissue stress in the PF by measuring changes in the thickness of the PF using ultrasound scans. It was a cross-sectional study involving 24 runners from the University of Valencia, recruited as volunteers between December 2018 and February 2019. A variety of data was recorded: (age, body mass index, type of footwear, number of workouts per week, KM run per week, sports injuries in the last year, pre and postrace ultrasound PF measurements). There were significant differences in the 3 postrace measurements of the left foot (<0.001). PF thicknesses were measured before and after running, with a minimal average difference of 0.4 mm in the medial and central fascicles, and 0.3 mm in the lateral fascicle. We observed PF thicknesses above 4mm in asymptomatic patients with no signs of vascularisation, proving that increased PF thickness is not the only criterion for diagnosis of plantar fasciitis.

Seven-Weeks Gait-Retraining in Minimalist Footwear Has No Effect on Dynamic Stability Compared With Conventional Footwear

Purpose: To investigate the effects of two different running footwear conditions (transition to minimalist footwear and conventional running footwear) on dynamic postural stability before and after 7 weeks of gait retraining program, and to evaluate the effect of fatigue on dynamic stability. Method: This randomized controlled clinical trial was carried out by 42 recreational male runners, who were randomly divided into two groups; Conventional Footwear Group (CFG) (n = 22) and Minimalist Footwear Group (MFG) (n = 20). Dynamic Postural Stability Index (DPSI), in a fatigued and non-fatigued state, were assessed before and after a gait retraining program. The gait retraining program consisted of three guided training sessions per week for 7 weeks. Training program was mainly focused on running technique and submaximal aerobic training with step-frequency exercises. Minimalist footwear was progressively introduced in the MFG. The CFG and MFG performed the same training exercises and a full body conditioning program. Fatigue was induced using a 30-minute running test at individual 85% of the maximal aerobic speed. Results: No differences in dynamic stability variables were found between MFG and CFG in any of the study condition. MFG and CFG showed better dynamic stability after the intervention program (CFG: 13.1% of change, DPSIpre = 0.3221 ± 0.04, DPSIpost = 0.2799 ± 0.04; p < .05; MFG: 6.7% of change, DPSIpre = 0.3117 ± 0.04, DPSIpost = 0.2907 ± 0.05). Finally, dynamic stability was significatively lower in both groups after fatigue protocol (p < .05). Conclusions: Following a 7-week gait retraining program, footwear did not affect the results, being the gait retraining program more relevant on improving dynamic stability.

Characteristics of return to running programs following an anterior cruciate ligament reconstruction: A scoping review of 64 studies with clinical perspectives

OBJECTIVE

To (1) describe return to running (RTR) programs used during rehabilitation after anterior cruciate ligament reconstruction (ACLR); and (2) provide clinical guidelines for RTR program after ACLR.

DESIGN

Scoping review.

LITERATURE SEARCH

We searched the MEDLINE (Pubmed), EMBASE, Web of Science and PEDro databases.

STUDY SELECTION CRITERIA

We included randomized controlled trial (RCT), cases series, meta-analyses, both scoping and systematic reviews including a rehabilitation program after ACLR with a specific RTR program. A "Running program checklist" (RPC) was elaborated based on the Template for Intervention Description and Replication (TIDieR), and on the Consensus on Exercise Reporting Template (CERT) checklist.

DATA SYNTHESIS

The percentage and number of studies specifying each of the running program checklist items in their RTR program were reported. Number of items reported in each study and specific analysis item-by-item were also proposed.

RESULTS

The "When (2)" item was the most frequently found (92.19%) and, conversely, the "Who (1)" item appeared only in four studies (6.2%). One-third of the studies presented only one item of the RPC, and 48 of the 64 articles discussed less than three items. Two studies described in detail their RTR program by reporting 8 and 9 items out of the 10, respectively. No study presented 10 of the PRC items.

CONCLUSION

There is a serious lack of information concerning RTR program following ACLR in the literature and further studies are needed to establish a program based on the best evidence.

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.

Immediate Effects of Manipulating Footwear or Cadence on the Lower Limb Biomechanics of Female Masters Runners

The objective of this study was to compare the immediate effects of modifications to footwear or cadence on lower limb biomechanics of female Masters runners. After analyzing habitual treadmill running biomechanics in 20 female runners (52.4 [8.3] y), we assessed the effects of 5 conditions: (1) barefoot running, (2) Merrell Vapor Glove, (3) Merrell Bare Access, (4) Brooks Pure Flow, and (5) increasing cadence by 10%. In comparison with habitual biomechanics, greater vertical loading rates of the ground reaction force were observed during running barefoot or with a Merrell Vapor Glove or Bare Access. There was high variability among participants as to changes in foot kinematics during the conditions. Running barefoot (-26.0%) and with a Merrell Vapor Glove (-12.5%) reduced sagittal plane knee moments, but increased sagittal plane ankle moments (both 6.1%). Increasing cadence by 10% resulted in a more modest decrease in knee flexion moments (-7.7%) without increasing peak external ankle dorsiflexion moments. When asked if they would prefer minimalist shoes or increasing cadence, 11 participants (55%) chose cadence and 9 (45%) chose footwear. Minimalist footwear decreased sagittal knee moments, but increased vertical loading rate and sagittal ankle moments. Increasing cadence may be useful to lower sagittal knee moments without increasing ankle moments.

Shock Acceleration and Attenuation during Running with Minimalist and Maximalist Shoes: A Time- and Frequency-Domain Analysis of Tibial Acceleration

Tibial shock attenuation is part of the mechanism that maintains human body stabilization during running. It is crucial to understand how shock characteristics transfer from the distal to proximal joint in the lower limb. This study aims to investigate the shock acceleration and attenuation among maximalist shoes (MAXs), minimalist shoes (MINs), and conventional running shoes (CONs) in time and frequency domains. Time-domain parameters included time to peak acceleration and peak resultant acceleration, and frequency-domain parameters contained lower (3−8 Hz) and higher (9−20 Hz) frequency power spectral density (PSD) and shock attenuation. Compared with CON and MAX conditions, MINs significantly increased the peak impact acceleration of the distal tibia (p = 0.01 and p < 0.01). Shock attenuation in the lower frequency depicted no difference but was greater in the MAXs in the higher frequency compared with the MIN condition (p < 0.01). MINs did not affect the tibial shock in both time and frequency domains at the proximal tibia. These findings may provide tibial shock information for choosing running shoes and preventing tibial stress injuries.

Insight into the hierarchical control governing leg stiffness during the stance phase of running

Leg stiffness plays a key role in the storage and release of elastic energy during stance. However, the extent to which a runner is able to reuse stored energy remains a limiting factor in determining their running effectiveness. In this study, ten habitual rearfoot strikers and ten habitual forefoot strikers were asked to run on a treadmill in three footwear conditions: traditional, neutral, and minimal running shoes. We examined the effect of habitual foot strike pattern and footwear on leg stiffness control within three task-relevant phases of stance (i.e. touch-down, loading, unloading). Control was quantified using stride-to-stride leg stiffness time-series and the coefficient of variability and detrended fluctuation analysis (DFA). The results are interpreted within a theoretical framework that blends dynamic systems theory and optimal feedback control. Results indicate that leg stiffness control is tightly regulated by an active control process during the loading period of stance. In contrast, the touch-down and unloading phases are driven mostly by passive allometric control mechanisms. The effect of footwear on leg stiffness control was inconclusive due to inconsistent trends across three shoe types. However, stiffness control was affected by landing technique. Habitual rearfoot strike runners have reduced DFA values during the touch-down and unloading phases. These sub-phases are associated with an allometric control process and suggests that rearfoot strike runners express a reduction in system complexity for leg stiffness control and hence, a less adaptable system.

Protocol for a randomised, assessor-blinded, parallel group feasibility trial of flat flexible school shoes for adolescents with patellofemoral pain

Background

There are limited evidence-based treatment options for adolescents with patellofemoral pain (PFP). Flat, flexible footwear have been shown to reduce patellofemoral joint loading and pain in adults with PFP. The efficacy of this intervention in adolescents with PFP is not established. The primary aim of this study is to determine the feasibility of conducting a large-scale randomised controlled trial (RCT) of the effect of flat, flexible school footwear, when compared to traditional school footwear, in adolescents with PFP. The secondary aim is to describe changes in self-reported outcome measures for adolescents with PFP while wearing flat, flexible footwear when compared to traditional school shoes.

Methods

Twenty-four adolescents with PFP will be recruited from the community. Following baseline assessment, participants will be randomly allocated to receive either (i) flat, flexible school footwear or, (ii) traditional school footwear. Participants will wear the shoe as per school requirements throughout a 12-week intervention period. Feasibility will be assessed with (i) ≥ 75% adherence to allocated shoe wear of their total weekly school wear time, (ii) a recruitment rate of one participant per fortnight, and (iii) a dropout rate of ≤ 20%. Patient reported outcome measures will describe changes in knee pain, function, quality of life and global rating of change at 6 and 12 weeks. Descriptive statistics will be used for the primary outcomes of feasibility.

Discussion

This study will determine the feasibility of conducting a large scale RCT evaluating the effect of flat, flexible school shoes for adolescents with PFP. A full-scale study will guide evidence-based management of adolescent PFP.

Trial registration

Australian New Zealand Clinical Trials Registry reference: ACTRN12621001525875, Date registered: 9th November 2021.

Kinematics of recreational male runners in "super", minimalist and habitual shoes

We conducted an exploratory analysis to compare running kinematics of 16 male recreational runners wearing Nike Vaporfly 4% (VP4), Saucony Endorphin racing flat (FLAT), and their habitual (OWN) footwear. We also explored potential relationships between kinematic and physiological changes. Runners (age: 33 ± 12 y, V˙ O_2peak: 55.2 ± 4.3 ml · kg^-1·min^-1) attended 3 sessions after completing an V˙ O_2peak test in which sagittal plane 3D kinematics at submaximal running speeds (60%, 70% and 80% ʋ V˙ O_2peak) were collected alongside economy measures. Kinematics were compared using notched boxplots, and between-shoe kinematic differences were plotted against between-shoe economy differences. Across intensities, VP4 involved longer flight times (6.7 to 10.0 ms) and lower stance hip range of motion (~3°), and greater vertical pelvis displacement than FLAT (~0.4 cm). Peak dorsiflexion angles (~2°), ankle range of motion (1.0° to 3.9°), and plantarflexion velocities (11.3 to 89.0 deg · sec^-1) were greatest in FLAT and lowest in VP4. Foot-ground angles were smaller in FLAT (2.5° to 3.6°). Select kinematic variables were moderately related to economy, with higher step frequencies and shorter step lengths in VP4 and FLAT associated with improved economy versus OWN. Footwear changes from OWN altered running kinematics. The most pronounced differences were observed in ankle, spatiotemporal, and foot-ground angle variables.

Effects of barefoot vs. shod walking during indoor and outdoor conditions in younger and older adults

BACKGROUND

Gait stability and variability measures in barefoot and shod locomotion are frequently investigated in younger but rarely in older adults. Moreover, most studies examine gait measures in laboratory settings instead of real-life settings.

RESEARCH QUESTIONS

How are gait stability and variability parameters affected by footwear compared to barefoot walking in younger and older adults as well as under indoor vs. outdoor conditions?

METHODS

Healthy younger (<35 years) and older adults (>65 years) participated in the randomised within-subject study design. Participants conducted consecutive 25 m walking trials barefoot and with standardised footwear inside and outside. Inertial measurement units were mounted on the participant's foot and used to calculate local dynamic stability (LDS), velocity and minimal toe clearance (MTC), stride length and stride time, including variabilities for these parameters. Linear mixed models were calculated.

RESULTS

Data of 32 younger (17 female, 15 male, age: 30 ± 4 years) and 42 older participants (24 female, 18 male, age: 71 ± 4 years) were analysed. MTC variability was higher in shod conditions compared to barefoot (p = 0.048) and in outdoor conditions (p < 0.001). LDS was different between age groups (p < 0.001). Gait velocity and MTC were higher in shod and outdoor conditions (both p < 0.001). Stride length and time were higher in shod conditions (both p < 0.001) and different between outdoor vs. indoor (longer stride length and shorter stride time outdoor, both (p < 0.001) as well as age groups (shorter stride length (p < 0.021) and stride time in older adults (p < 0.001).

SIGNIFICANCE

Results suggest that gait stability and variability in older and younger adults are acutely affected by footwear vs. barefoot and indoor vs. outdoor walking conditions, indicating a high adaptiveness of these parameters to different experimental conditions. Consequently, future studies should be careful with generalising results obtained under certain conditions. Findings stress the clinical potential of barefoot walking.

Reversing the Mismatch With Forefoot Striking to Reduce Running Injuries

Recent studies have suggested that 95% of modern runners land with a rearfoot strike (RFS) pattern. However, we hypothesize that running with an RFS pattern is indicative of an evolutionary mismatch that can lead to musculoskeletal injury. This perspective is predicated on the notion that our ancestors evolved to run barefoot and primarily with a forefoot strike (FFS) pattern. We contend that structures of the foot and ankle are optimized for forefoot striking which likely led to this pattern in our barefoot state. We propose that the evolutionary mismatch today has been driven by modern footwear that has altered our footstrike pattern. In this paper, we review the differences in foot and ankle function during both a RFS and FFS running pattern. This is followed by a discussion of the interaction of footstrike and footwear on running mechanics. We present evidence supporting the benefits of forefoot striking with respect to common running injuries such as anterior compartment syndrome and patellofemoral pain syndrome. We review the importance of a gradual shift to FFS running to reduce transition-related injuries. In sum, we will make an evidence-based argument for the use of minimal footwear with a FFS pattern to optimize foot strength and function, minimize ground reaction force impacts and reduce injury risk.

Metabolic and performance responses of male runners wearing 3 types of footwear: Nike Vaporfly 4%, Saucony Endorphin racing flats, and their own shoes

PURPOSE

We compared running economy (RE) and 3-km time-trial (TT) variables of runners wearing Nike Vaporfly 4% (VP4), Saucony Endorphin lightweight racing flats (FLAT), and their habitual running (OWN) footwear.

METHODS

Eighteen male recreational runners (age = 33.5 ± 11.9 year (mean ± SD), peak oxygen uptake (VO_2peak) = 55.8 ± 4.4 mL/kg·min) attended 4 sessions approximately 7 days apart. The first session consisted of a VO_2peak test to inform subsequent RE speeds set at 60%, 70%, and 80% of the speed eliciting VO_2peak. In subsequent sessions, treadmill RE and 3-km TTs were assessed in the 3 footwear conditions in a randomized, counterbalanced crossover design.

RESULTS

Oxygen consumption (mL/kg·min) was less in VP4 (from 4.3% to 4.4%, p ≤ 0.002) and FLAT (from 2.7% to 3.4%, p ≤ 0.092) vs. OWN across intensities, with a non-significant difference between VP4 and FLAT (1.0%-1.7%, p ≥ 0.292). Findings related to energy cost (W/kg) and energetics cost of transport (J/kg·m) were comparable. VP4 3-km TT performance (11:07.6 ± 0:56.6 mm:ss) was enhanced vs. OWN by 16.6 s (2.4%, p = 0.005) and vs. FLAT by 13.0 s (1.8%, p = 0.032). The 3-km times between OWN and FLAT (0.5%, p = 0.747) were similar. Most runners (n = 11, 61%) ran their fastest TT in VP4.

CONCLUSION

Overall, VP4 improved laboratory-based RE measures in male recreational runners at relative speeds compared to OWN, but the RE improvements in VP4 were not significant vs. FLAT. More runners exhibited better treadmill TT performances in VP4 (61%) vs. FLAT (22%) and OWN (17%). The variability in RE (-10.3% to 13.3%) and TT (-4.7% to 9.3%) improvements suggests that responses to different types of shoes are individualized and warrant further investigation.

Study of the kinetics of the determinants of performance during a mountain ultra marathon: Multidisciplinary protocol of the first Trail Scientifique de Clécy 2021 (Preprint)

Background

The growing interest of the scientific community in trail running has highlighted the acute effects of practice at the time of these races on isolated aspects of physiological and structural systems; biological, physiological, cognitive, and muscular functions; and the psychological state of athletes. However, no integrative study has been conducted under these conditions with so many participants and monitoring of pre-, per-, and postrace variables for up to 10 days over a distance close to 100 miles.

Objective

The aim of this study was to evaluate the kinetics of the performance parameters during a 156 km trail run and 6000 m of elevation gain in pre-, per-, and postrace conditions. The general hypothesis is based on significant alterations in the psychological, physiological, mechanical, biological, and cognitive parameters.

Methods

The Trail Scientifique de Clécy took place on November 11, 2021. This prospective experimental study provides a comprehensive exploration of the constraints and adaptations of psychophysiological and sociological variables assessed in real race conditions during a trail running of 156 km on hilly ground and 6000 m of elevation gain (D+). The study protocol allowed for repeatability of study measurements under the same experimental conditions during the race, with the race being divided into 6 identical loops of 26 km and 1000 m D+. Measurements were conducted the day before and the morning of the race, at the end of each lap, after a pit stop, and up to 10 days after the race. A total of 55 participants were included, 43 (78%) men and 12 (22%) women, who were experienced in ultra–trail-running events and with no contraindications to the practice of this sport.

Results

The launch of the study was authorized on October 26, 2021, under the trial number 21-0166 after a favorable opinion from the Comité de Protection des Personnes Ouest III (21.09.61/SIRIPH 2G 21.01586.000009). Of the 55 runners enrolled, 41 (75%) completed the race and 14 (25%) dropped out for various reasons, including gastric problems, hypothermia, fatigue, and musculoskeletal injuries. All the measurements for each team were completed in full. The race times (ie, excluding the measurements) ranged from 17.8206 hours for the first runner to 35.9225 hours for the last runner. The average time to complete all measurements for each lap was 64 (SD 3) minutes.

Conclusions

The Trail Scientifique de Clécy, by its protocol, allowed for a multidisciplinary approach to the discipline. This approach will allow for the explanation of the studied parameters in relation to each other and observation of the systems of dependence and independence. The initial results are expected in June 2022.

International Registered Report Identifier (IRRID)

RR1-10.2196/38027

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.

The long-term effects of wearing moderate minimalist shoes on a child's foot strength, muscle structure and balance: A randomised controlled trial

BACKGROUND

From retrospective research, it is believed that children who predominantly spend their time shod have poorer foot strength and performance than those who are predominantly barefoot. Children's foot motion has been shown to be adversely affected by standard school shoes; however, the long-term effect of moderate minimalist shoes on foot strength, muscle structure and balance in children is unknown.

RESEARCH QUESTION

Does wearing moderate minimalist shoes, compared to stiff shoes, benefit a child's foot strength, muscle structure and performance over time?

METHODS

Seventy healthy children (9-12 yr) were randomly assigned to wear standard (control), or minimalist shoes (experimental) at school, for nine months. Cross-sectional areas (CSA) of Abductor Hallucis (AH) and Flexor Digitorum Brevis (FDB) muscles, and toe flexor strength (TFS) of hallux and lesser toes separately, were primary outcome measures. Single leg balance (SLB), Y-balance test (YBT) and standing long jump (SLJ) were secondary outcome measures. Pre- and post-intervention measurements were analysed for between group differences with ANCOVA.

RESULTS

Minimalist shoes resulted in moderate but statistically non-significant increases in muscle CSA (AH η²_p =.04, FDB η²_p =.05) and TFS (hallux η²_p =.05, lesser toes η²_p =.04). Significant moderate to large improvements in YBT in the experimental group were found in the postero-medial (P = .04, η²_p =.07) and postero-lateral (P = .01, η²_p =.10) directions. YBT (anterior, postero-medial and postero-lateral) was correlated with hallux TFS (R =.29,.27 and.33 respectively), lesser toes TFS (R =.28,.35 and.38 respectively) and SLJ (R =.30,.39 and.57 respectively). CSA of FDB was correlated with SLJ (R =.34) and SLB (R =.42).

SIGNIFICANCE

Wearing moderate minimalist shoes long-term improves balance in children. TFS is correlated with better balance and SLJ. Moderate minimalist school shoes are recommended for children.

Acute Effects of Heel-to-Toe Drop and Speed on Running Biomechanics and Strike Pattern in Male Recreational Runners: Application of Statistical Nonparametric Mapping in Lower Limb Biomechanics

With the increased popularity of running, many studies have been conducted into footwears that are highly related to running performance and running-related injuries. Previous studies investigated different shoe types and running shoes with different heel-to-toe drops (HTDs). However, no research was found in investigating shoes with negative values with HTD. Therefore, the aim of this study was to determine the acute effect of HTD and running speed on lower limb biomechanics and strike pattern in recreational runners. Thirteen male recreational runners wearing shoes with two different HTDs (−8 and 8 mm) performed running at three different speeds (preferred speed [PS], 90% of PS, 110% of PS). Lower extremity kinematics and ground reaction forces were synchronously captured via Vicon motion analysis system and AMTI force platform. Strike index (SI), vertical average loading rate (VALR), vertical instantaneous loading rate (VILR), excursion, eversion duration, joint angles, and range of motion (ROM) of metatarsophalangeal (MTP), ankle, knee, and hip joints were calculated. Joint angles during the entire stance phase were analyzed applying the statistical nonparametric mapping (SnPM) method. SI and VILR in shoes with −8 mm HTD significantly increased by 18.99% and 31.836 BW/s compared to those with 8 mm HTD (SI: p = 0.002; VILR: p < 0.001). Significant alterations of ROM occurred in the MTP, ankle, and knee joints (p < 0.05), and HTD factor primarily accounted for these changes. Joint angles (MTP, knee, and hip) during the entire stance phase altered due to HTD and speed factors. Running speed primarily influenced the kinematics parameters of knee and hip joints, increasing knee angles in the frontal plane and hip angle in the horizontal plane at PS (p > 0.05). Compared to shoes with 8 mm HTD, shoes with −8 mm HTD may be useful to storage and return energy because of the increased ROM of MTP in the sagittal plane. Besides, forefoot strike gait retraining was recommended before transition from normal running shoes to running shoes with −8 mm HTD.

Effects of Minimalist Footwear and Foot Strike Pattern on Plantar Pressure during a Prolonged Running

The use of minimalist shoes (MS) in running involves changes in running mechanics compared to conventional shoes (CS), but there is still little research analysing the effects of this footwear on plantar pressure, which could help to understand some risk injury factors. Moreover, there are no studies examining the effects of a prolonged running and foot strike patterns on baropodometric variables in MS. Therefore, the aim of this study was to analyse the changes produced using MS on plantar pressure during a prolonged running, as well as its interaction with the time and foot strike pattern. Twenty-one experienced minimalist runners (age 38 ± 10 years, MS running experience 2 ± 1 years) ran with MS and CS for 30 min at 80% of their maximal aerobic speed, and mean pressure, peak pressure, contact time, centre of pressure velocity, relative force and contact area were analysed using a pressure platform. Foot strike pattern and time were also considered as factors. The multivariable linear regression mixed models showed that the use of MS induced, at the end of a prolonged running, higher peak pressure (p = 0.008), lower contact time (p = 0.004) and lower contact area (p < 0.001) than using CS. Also, runners with forefoot strike pattern using MS, compared to midfoot and rearfoot patterns, showed higher mean and peak pressure (p < 0.001) and lower contact time and area (p < 0.05). These results should be considered when planning training for runners using MS, as higher peak pressure values when using this type of footwear could be a risk factor for the development of some foot injuries.