Examining injury risk and pain perception in runners using minimalist footwear

An Investigation Into the Measurement of Injury Severity in Running-Related Injury Research: A Scoping Review

Understanding injury severity is essential to inform injury prevention practice. The aims of this scoping review were to investigate how running-related injury (RRI) severity is measured, compare how it differs across studies, and examine whether it influences study outcomes (i.e., injury rates and risk factor identification). This scoping review was prospectively registered with Open Science Framework. A systematic electronic search was conducted using PubMed, Scopus, SPORTDiscuss, MEDLINE, and Web of Science databases. Included studies were published in English between January 1980 and December 2023, investigated RRIs in adult running populations, and included a measure of injury severity. Results were extracted and collated. Sixty-six studies were included. Two predominant primary criteria are used to define injury severity: the extent of the effect on running and/or the extent of the physical description. When secondary definition criteria are considered, 13 variations of injury severity measurement are used. Two approaches are used to grade injury severity: a categorization approach or a continuous numerical scale. Overall, the measurement of RRI severity is relatively inconsistent across studies. Less than half of studies report incidence rates per level of injury severity, while none report specific risk factors across levels, making it difficult to determine if the approach to measuring injury severity influences these study outcomes. This lack of information is possibly contributing to inconsistent rates of RRIs reported, and the lack of clarity on risk factors.

Prevalence, diagnosis and management of musculoskeletal disorders in elite athletes: A mini-review

Musculoskeletal injuries in elite sports are ones of the most impact issue because their remarkable impact on performance caused by drastic absence of training and competition and a progressive deterioration in physical health, emotional and social athletes' dimensions. Also, the prevalence of epidemiologic research found an incidence of musculoskeletal disorders vary within sports and in elite athletes which is even higher as a consequence of higher demand physical performance. This way, the loss of physical performance due to an sport injury impacts not only the individual economic sphere of the professional but also that ofsports entities, reaching, according to some studies, a loss estimated in the range of 74.7 million pounds. Thus, the purpose of this article is to review and to provide an overview of the most common musculoskeletal injuries in elite sports precipitating factors, clinical presentation, evidence-based diagnostic evaluation, and treatment recommendations with a view to preventing medical conditions or musculoskeletal injuries that may alter performance and general health in the elite athletes.

Biomechanics and Injury Prevention for Barefoot/Minimalist Running

» Biomechanical studies indicate that barefoot/minimalist running coincides with a transition to an anterior foot strike, lower vertical loading rates, higher cadences, less energy absorption at the knee joint, and higher energy absorption at the ankle joint.» The clinical outcome studies indicate improvement of previous injuries and equivocal injury rates in the barefoot/minimal-style running groups.» Foot strike pattern is more important than footwear regarding injury prevention and vertical loading rate.» Minimalist footwear places higher degrees of stress on the ankle joints and an increased injury rate when abruptly transitioning to barefoot running. Runners must weigh the risks and benefits and take caution to properly strengthen their feet and safely transition to minimalist running.

Foot Pronation Prediction with Inertial Sensors during Running: A Preliminary Application of Data-Driven Approaches

Abnormal foot postures may affect foot movement and joint loading during locomotion. Investigating foot posture alternation during running could contribute to injury prevention and foot mechanism study. This study aimed to develop feature-based and deep learning algorithms to predict foot pronation during prolonged running. Thirty-two recreational runners have been recruited for this study. Nine-axial inertial sensors were attached to the right dorsum of the foot and the vertical axis of the distal anteromedial tibia. This study employed feature-based machine learning algorithms, including support vector machine (SVM), extreme gradient boosting (XGBoost), random forest, and deep learning, i.e., one-dimensional convolutional neural networks (CNN1D), to predict foot pronation. A custom nested k-fold cross-validation was designed for hyper-parameter tuning and validating the model's performance. The XGBoot classifier achieved the best accuracy using acceleration and angular velocity data from the foot dorsum as input. Accuracy and the area under curve (AUC) were 74.7 ± 5.2% and 0.82 ± 0.07 for the subject-independent model and 98 ± 0.4% and 0.99 ± 0 for the record-wise method. The test accuracy of the CNN1D model with sensor data at the foot dorsum was 74 ± 3.8% for the subject-wise approach with an AUC of 0.8 ± 0.05. This study found that these algorithms, specifically for the CNN1D and XGBoost model with inertial sensor data collected from the foot dorsum, could be implemented into wearable devices, such as a smartwatch, for monitoring a runner's foot pronation during long-distance running. It has the potential for running shoe matching and reducing or preventing foot posture-induced injuries.

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.

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.

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.

Adolescent Running Biomechanics - Implications for Injury Prevention and Rehabilitation

Global participation in running continues to increase, especially amongst adolescents. Consequently, the number of running-related injuries (RRI) in adolescents is rising. Emerging evidence now suggests that overuse type injuries involving growing bone (e.g., bone stress injuries) and soft tissues (e.g., tendinopathies) predominate in adolescents that participate in running-related sports. Associations between running biomechanics and overuse injuries have been widely studied in adults, however, relatively little research has comparatively targeted running biomechanics in adolescents. Moreover, available literature on injury prevention and rehabilitation for adolescent runners is limited, and there is a tendency to generalize adult literature to adolescent populations despite pertinent considerations regarding growth-related changes unique to these athletes. This perspective article provides commentary and expert opinion surrounding the state of knowledge and future directions for research in adolescent running biomechanics, injury prevention and supplemental training.

Can the "Appropriate" Footwear Prevent Injury in Leisure-Time Running? Evidence Versus Beliefs

Leisure-time running is one of the most popular forms of physical activity around the world. It can be practiced almost everywhere and requires mainly a pair of "appropriate" running shoes. However, the term appropriate is ambiguous, and the properties of running footwear have always generated hot debates among clinicians, coaches, and athletes, whatever the level of practice. As the main interface between the runner's foot and the ground, the shoe potentially plays an important role in managing repetitive external mechanical loads applied to the musculoskeletal system and, thus, in injury prevention. Consequently, over the last decades, running shoes have been prescribed based on matching shoe features to foot morphology. This strategy aligns with the popular belief that footwear is one of the main extrinsic factors influencing running-related injury risk. Despite a seemingly sound strategy for shoe prescription and constant progress in running-footwear technology, the injury rate remains high. Therefore, our aim in this narrative literature review is to clarify whether the prescription of appropriate footwear to prevent injury in running is evidence based, the result of logical fallacy, or just a myth. The literature presented in this review is based on a nonsystematic search of the MEDLINE database and focuses on work investigating the effect of shoe features on injury risk in runners. In addition, key elements for a proper understanding of the literature on running footwear and injury risk are addressed. In this literature review, we outline (1) the main risk factors and the mechanisms underlying the occurrence of running-related injury, (2) important methodologic considerations for generating high-level evidence, (3) the evidence regarding the influence of running-shoe features on injury risk, (4) future directions for research, and (5) final general recommendations.

What are the Benefits and Risks Associated with Changing Foot Strike Pattern During Running? A Systematic Review and Meta-analysis of Injury, Running Economy, and Biomechanics

BACKGROUND

Running participation continues to increase. The ideal strike pattern during running is a controversial topic. Many coaches and therapists promote non-rearfoot strike (NRFS) running with a belief that it can treat and prevent injury, and improve running economy.

OBJECTIVE

The aims of this review were to synthesise the evidence comparing NRFS with rearfoot strike (RFS) running patterns in relation to injury and running economy (primary aim), and biomechanics (secondary aim).

DESIGN

Systematic review and meta-analysis. Consideration was given to within participant, between participant, retrospective, and prospective study designs.

DATA SOURCES

MEDLINE, EMBASE, CINAHL, and SPORTDiscus.

RESULTS

Fifty-three studies were included. Limited evidence indicated that NRFS running is retrospectively associated with lower reported rates of mild (standard mean difference (SMD), 95% CI 3.25, 2.37-4.12), moderate (3.65, 2.71-4.59) and severe (0.93, 0.32-1.55) repetitive stress injury. Studies prospectively comparing injury risk between strike patterns are lacking. Limited evidence indicated that running economy did not differ between habitual RFS and habitual NRFS runners at slow (10.8-11.0 km/h), moderate (12.6-13.5 km/h), and fast (14.0-15.0 km/h) speeds, and was reduced in the immediate term when an NRFS-running pattern was imposed on habitual RFS runners at slow (10.8 km/h; SMD = - 1.67, - 2.82 to - 0.52) and moderate (12.6 km/h; - 1.26, - 2.42 to - 0.10) speeds. Key biomechanical findings, consistently including both comparison between habitual strike patterns and following immediate transition from RFS to NRFS running, indicated that NRFS running was associated with lower average and peak vertical loading rate (limited-moderate evidence; SMDs = 0.72-2.15); lower knee flexion range of motion (moderate-strong evidence; SMDs = 0.76-0.88); reduced patellofemoral joint stress (limited evidence; SMDs = 0.63-0.68); and greater peak internal ankle plantar flexor moment (limited evidence; SMDs = 0.73-1.33).

CONCLUSION

The relationship between strike pattern and injury risk could not be determined, as current evidence is limited to retrospective findings. Considering the lack of evidence to support any improvements in running economy, combined with the associated shift in loading profile (i.e., greater ankle and plantarflexor loading) found in this review, changing strike pattern cannot be recommended for an uninjured RFS runner.

PROSPERO REGISTRATION

CRD42015024523.

Impact Acceleration During Prolonged Running While Wearing Conventional Versus Minimalist Shoes

Purpose: In recent years a sub-group of minimalist runners have emerged who aim to perform physical exercise more naturally in an attempt to reduce running-related injuries. Here we aimed to determine the effect that running with minimalist footwear in a prolonged run has on foot-impact accelerations. Method: Seventeen runners ran with minimalist and conventional shoes (MS and CS, respectively) in two separate sessions; the participants had experience with both footwear types. We measured the length and frequency of each stride, as well as the tibial and head impact acceleration every 5 minutes during a prolonged run (30 minutes at 80% of each individual's maximum aerobic speed). Results: There were significant differences in the acceleration rate in the tibia (CS: 516.1 ± 238.47 G/s and MS: 786.6 ± 238.45 G/s; p = .009) and head (CS: 73.3 ± 23.65 G/s and MS: 120.7 ± 44.13 G/s; p = .000). Our data indicate that the type of footwear increased the stride frequency and decreased length and that the impact acceleration is increased with MS compared to CS (p < .05 in both cases). However, the effect of prolonged run was not significantly different between CS and MS (p < .05). Conclusions: The peak tibia acceleration and headtibia acceleration rate indicate that the use of MS may be related to a higher risk of injury. These differences remained independently of the runners' fatigue state.

One in four trail running race entrants sustained an injury in the 12 months training preceding the 2019 SkyRun race

OBJECTIVE

To determine the epidemiology and clinical characteristics of RRIs among trail runners who entered the 2019 SkyRun races.

DESIGN

Descriptive cross-sectional study.

SETTING

2019 SkyRun races.

PARTICIPANTS

Consent for data analysis was given by 305 of 412 (74%) race entrants.

MAIN OUTCOME MEASURES

Retrospective annual incidence (RRIs/1000 h), point prevalence (%), frequency (%), characteristics (anatomical region, body area, tissue type, pathology type) and injury severity (mean severity score; 95% CI) of RRIs.

RESULTS

28.2% of participants reported at least one RRI. The retrospective annual incidence was 49.5 RRIs per 1000h and the point prevalence was 1.3%. Most injuries occurred in the lower limb (87.3%), with the knee (26.5%), ankle (21.6%), and foot (16.7%) reported as the most frequently injured body areas. Muscle/tendon accounted for 44.1% of tissue type injuries. Tendinopathy (27.5%), joint sprain (19.6%), and muscle injury (15.7%) were the most common pathology types reported. The mean injury severity score was 31.6.

CONCLUSIONS

One in 4 trail runners reported at least one RRI in the 12 months leading up to a race. RRIs mostly affected the lower limb specifically the knee, ankle and foot. Future research should establish injury risk factors to ultimately develop specific injury prevention strategies.

Muscle Activity of the Triceps Surae With Novel Propulsion Heel-Lift Orthotics in Recreational Runners

Background:

The triceps surae muscle has been identified with propulsion during running gait, and typical heel-lift orthotics (THOs) have been used to treat some sports injuries of this structural-biomechanical unit. The effects of a novel propulsion heel-lift orthotic (PHO) on surface electromyography (EMG) activity of the gastrocnemius during a full cycle of running have yet to be tested.

Purpose/Hypothesis:

We aimed to assess EMG changes in gastrocnemius medialis and lateralis muscle activity when wearing THOs, PHOs, or neutral sports shoes only (SO) during running. We hypothesized that EMG activity of the triceps surae muscle would be lower for PHOs than THOs or SO during running.

Study Design:

Controlled laboratory study.

Methods:

A total of 26 healthy, regular recreational runners of both sexes (mean age, 33.58 ± 6.02 years) with a neutral Foot Posture Index and rearfoot strike pattern were recruited to run on a treadmill at 9 km/h using aleatory THOs of 6 and 9 mm, PHOs, and SO while EMG activity of the gastrocnemius medialis and lateralis muscles was recorded over a 30-second period. Intraclass correlation coefficients were calculated to assess reliability.

Results:

The intraclass correlation coefficient values indicated near perfect reliability, ranging from 0.801 for 6-mm THOs to 0.959 for SO in the gastrocnemius lateralis muscle. EMG activity of the gastrocnemius lateralis muscle was greater for PHOs (25.516 ± 4.780 mV) than for SO (23.140 ± 4.150 mV) (P < .05), but EMG activity of the gastrocnemius medialis muscle did not show any statistically significant difference between conditions (23.130 ± 2.980 mV vs 26.315 ± 2.930 mV, respectively) (P = .3).

Conclusion:

A novel PHO may increase muscle activity of the gastrocnemius lateralis during a full cycle of running gait; consequently, its prescription to treat triceps surae muscle injuries is cautioned.

Clinical Relevance:

The prescription of novel PHOs could increase EMG activity, which has not been previously described.

PREVALENCE AND FACTORS ASSOCIATED WITH INJURIES IN RECREATIONAL RUNNERS: A CROSS-SECTIONAL STUDY

ABSTRACT Introduction The increased number of people who choose running as a form of exercise has been associated with a higher prevalence of musculoskeletal injuries. Objectives To determine the prevalence and the factors that could be correlated with injuries among amateur runners in Recife, in the State of Pernambuco (PE), Brazil. Methods An observational, cross-sectional study, in which 300 (three hundred) amateur runners answered a social demographic questionnaire, as well as questions about training characteristics, footstrike and landing pattern, and history of running injuries. The data were analyzed by descriptive statistics, the student-t test to compare means, and the Chi-squared to compare prevalences. Results The prevalence of injuries amongst runners in Recife-PE was 58.5% (n= 175), the knee being the most commonly injured site (37.3%). In both groups - runners with and without injuries – there was a higher number of male runners, with 72.4% and 72.6% respectively. There was no difference in relation to the weekly frequency of running between the groups (p<0.63). However, runners with a history of injuries ran around 7 kmh a week more than the runners without injuries (p<0.03). A neutral footstrike (F=0.87; p=0.99) and hindfoot landing (F=4.13; p=0.90) were the most reported running patterns in both groups. It was found that wear was the main criterion used for changing running shoes in both groups (F = 8.35, p = 0.4). Conclusion There was a high prevalence of musculoskeletal injuries among amateur runners in Recife-PE. Among the factors associated with the injuries, one variable was significant: a higher weekly volume of training. Level of evidence II; Study type: Cross-sectional study.

Review of Terms and Definitions Used in Descriptions of Running Shoes

OBJECTIVE

Our study aim is to identify and describe the definitions used for different types of running shoes. In addition, we highlight the existence of gaps in these concepts and propose possible new approaches. Methods: This review was undertaken in line with the guidelines proposed by Green et al., based on a literature search (until December 2019) of the PubMed, Web of Science, Scopus, SPORTDiscus and Google Scholar databases. A total of 23 papers met the inclusion criteria applied to identify the definition of running shoes.

RESULTS

Although there is a certain consensus on the characteristics of minimalist footwear, it is also described by other terms, such as barefoot-style or barefoot-simulating. Diverse terms are also used to describe other types of footwear, and in these cases, there is little or no consensus regarding their characteristics.

CONCLUSIONS

The terms barefoot-simulated footwear, barefoot-style footwear, lightweight shoes and full minimalist shoes are all used to describe minimalist footwear. The expressions partial minimalist, uncushioned minimalist and transition shoes are used to describe footwear with non-consensual characteristics. Finally, labels such as shod shoes, standard cushioned running shoes, modern shoes, neutral protective running shoes, conventional, standardised, stability style or motion control shoes span a large group of footwear styles presenting different properties.

Transition to forefoot strike reduces load rates more effectively than altered cadence

BACKGROUND

Excessive vertical impacts at landing are associated with common running injuries. Two primary gait-retraining interventions aimed at reducing impact forces are transition to forefoot strike and increasing cadence. The objective of this study was to compare the short- and long-term effects of 2 gait-retraining interventions aimed at reducing landing impacts.

METHODS

A total of 39 healthy recreational runners using a rearfoot strike and a cadence of ≤170 steps/min were randomized into cadence (CAD) or forefoot strike (FFS) groups. All participants performed 4 weeks of strengthening followed by 8 sessions of gait-retraining using auditory feedback. Vertical average load rates (VALR) and vertical instantaneous load rates (VILR) were calculated from the vertical ground reaction force curve. Both cadence and foot strike angle were measured using 3D motion analysis and an instrumented treadmill at baseline and at 1 week, 1 month, and 6 months post retraining.

RESULTS

ANOVA revealed that the FFS group had significant reductions in VALR (49.7%) and VILR (41.7%), and changes were maintained long term. Foot strike angle in the FFS group changed from 14.2° dorsiflexion at baseline to 3.4° plantarflexion, with changes maintained long term. The CAD group exhibited significant reduction only in VALR (16%) and only at 6 months. Both groups had significant and similar increases in cadence at all follow-ups (CAD, +7.2% to 173 steps/min; and FFS, +6.1% to 172 steps/min).

CONCLUSION

Forefoot strike gait-retraining resulted in significantly greater reductions in VALR and similar increases in cadence compared to cadence gait-retraining in the short and long term. Cadence gait-retraining resulted in small reductions in VALR at only the 6-month follow-up.

Measurement of intrinsic foot stiffness in minimally and traditionally shod runners using ultrasound elastography: A pilot study

Running is an activity with a consistently high injury rate. Running footwear design that mimics barefoot running has been proposed to reduce injury rate by increasing the strength of foot structures. However, there is little evidence to support this. The purpose of the current study is to use shear wave ultrasound elastography to examine material properties (shear modulus) of intrinsic foot structures in experienced minimally and traditionally shod runners. It is hypothesized that minimalist runners will exhibit increased stiffness compared to controls demonstrating the strengthening of these structures. Eighteen healthy runners (8 minimalist and 10 traditionalist), running a minimum of 10 mi · wk^-1, participated. Elastography scans were performed on the left foot of each participant. There is no apparent stiffening of foot structures associated with wearing minimalist shoes. Only the FHB tendon is different between shoe types and, contrary to the hypothesis, was stiffer in traditionalist compared to minimalist runners (257.26 ± 51.64 kPa vs 160.88 ± 27.79 kPa, respectively). A moderate positive (r = 0.7) relationship between training load and tendon stiffness suggests strengthening of tendon when running in traditional shoes. If running in minimalist shoes increases loading on these structures without resulting in stronger tissues, it is possible that minimalist footwear may increase injury risk.

Analysis of Running-Related Injuries: The Vienna Study

Background: This study aimed to provide an extensive and up-to-date analysis of running-related injuries (RRI) and analyze a broad range of contributing factors for a large heterogeneous and non-selected running population from Central Europe. Methods: Anthropometric, training, footwear, anatomic malalignment, and injury data from 196 injured runners were assessed case-controlled and retrospectively. Univariate and multivariate regression models were developed to identify associated factors for specific injury locations and diagnoses. Results: The majority of patients were female (56%). Three most frequently observed malalignments included varus knee alignment, pelvic obliquity, and patellar squinting. The most common injuries were the patellofemoral pain syndrome (PFPS), the iliotibial band friction syndrome (ITBFS), patellar tendinopathy, spinal overload, and ankle instability. A number of contributing factors were identified. Previous injury history was a contributing factor for knee injuries and ITBFS. Lower training load was reported with a higher incidence of PFPS, while a higher training load was positively associated with injuries of the lower leg. Runners with a higher body mass index (BMI) were at a significantly higher risk for lower back injuries. Conclusions: Running-related injuries are multifactorial associated with a combination of variables including personal data, training load, anatomic malalignments, and injury history. They can furthermore result from a lack of experience/training as well as from overuse. Suffering a specific RRI of high risk could be defined based on individual predispositions and help to induce appropriate training balance.

Alterations in Running Biomechanics after 12 Week Gait Retraining with Minimalist Shoes

Purpose: The intervention of 12 week gait retraining with minimalist shoes was established to examine its effect on impact forces, joint mechanics, and vertical stiffness during running. Methods: Thirty male recreational runners were randomly assigned to the gait retraining + minimalist shoe (n = 15, GR) and minimalist shoe (n = 15, MIN) groups. The ground reaction force and marker trajectories were collected before and after intervention at a speed of 3.33 ± 5% m/s. Results: A total of 17 participants (9 in the GR group and 8 in the MIN group) completed the training. After training, (1) the loading rate of both groups decreased significantly, and the loading rate of the GR group was lower than that of the MIN group. (2) The foot strike angle of the GR group decreased significantly after training, and the plantarflexion angle and hip joint angular extension velocity increased in both groups. (3) The moment of ankle joint increased in the GR group, and the stiffness of lower limbs was significantly improved in both groups. Conclusion: The 12 week gait retraining with minimalist shoes converted rearfoot strikers into forefoot strikers with a rate of 78% (7/9). More importantly, such a combined program, compared to the training with only minimalist shoes, can avoid the peak impact force and decrease the loading rate more effectively, thus providing a potential means of reducing risk of running injury caused by impact forces. Moreover, the increased vertical stiffness of lower extremity after gait retraining may improve running economy and corresponding energy utilization. However, these observations also suggest that the sole use of minimalist footwear may have limited effects on reducing running-related impacts.

Association Between Running Shoe Characteristics and Lower Extremity Injuries in United States Military Academy Cadets

BACKGROUND

Running-related overuse injuries are very common among recreational runners, with the reported annual injury rates ranging from 39% to 85%. Relatively few large prospective cohort studies have been conducted to investigate injury risk associated with different running shoe characteristics, and the results of the existing studies are often contradictory.

PURPOSE/HYPOTHESIS

The purpose was to investigate the relationship between running shoe characteristics and lower extremity musculoskeletal injury. It was hypothesized that the risk of injury would be increased in individuals wearing shoes with minimal torsional stiffness and heel height compared with those wearing shoes with greater levels of torsional stiffness and heel height.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

The study included 1025 incoming cadets. Shoe torsional stiffness and heel height were calculated and recorded. Demographic data were recorded and analyzed as potential covariates. Lower extremity injuries sustained over 9 weeks during cadet basic training were documented by use of the Armed Forces Health Longitudinal Technology Application and the Cadet Illness and Injury Tracking System. Kaplan-Meier survival curves were estimated, with time to incident lower extremity injury as the primary outcome by level of the independent predictor variables. Risk factors or potential covariates were carried forward into multivariable Cox proportional hazards regression models. Absolute and relative risk reduction and numbers needed to treat were calculated.

RESULTS

Approximately 18.1% of participants incurred a lower extremity injury. Cadets wearing shoes with moderate lateral torsional stiffness were 49% less likely to incur any type of lower extremity injury and 52% less likely to incur an overuse lower extremity injury than cadets wearing shoes with minimal lateral torsional stiffness, both of which were statistically significant observations. Injury risk was similar among cadets wearing shoes with minimal and extreme lateral torsional stiffness.

CONCLUSION

Shoes with mild to moderate lateral torsional stiffness may be appropriate in reducing risk of lower extremity injury in cadets. Shoes with minimal lateral torsional stiffness should be discouraged in this population.

"How are running shoes assessed? A systematic review of characteristics and measurement tools used to describe running footwear"

Background: Many footwear characteristics are argued as risk factors for running related injuries (RRI). Several footwear assessment tools are available; however, their use in studies of RRI is unknown. Objective: This systematic review evaluated the characteristics and methods of assessing footwear in studies of RRI. Design: Five online databases were searched for studies on adult runners, in running style footwear, who experienced running-related pain or injury. The methodological quality of included articles was independently assessed by two raters using a modified Downs and Black checklist. Study and participant characteristics, footwear assessment tools used, and footwear characteristics reported were extracted for qualitative synthesis. Results: Twenty-four articles were included in the review. Low risk of bias was determined for 11 (44%) of the included studies. Twenty-eight different footwear characteristics were grouped into four categories: nomenclature, measurements, qualitative features, and subjective features. Fifteen different methods for assessing the 28 footwear characteristics were reported among the included studies. Only three methods were described previously, as valid and reliable. Conclusion: Differences in assessing footwear may mask the link between footwear characteristics and injury risk. Systematic footwear assessments and nomenclature are needed to evaluate the effects of footwear characteristics on RRI.

Perception of impact is affected by stimulus intensity

Perception of external loads may be a central topic to understand adjustments to the mechanical demands during movement. Nevertheless, the association between the perceived and the real load received is still controversial. This study aimed to correlate vertical ground reaction force (vGRF) to the perception of impact in different regimens of stimulus application. Ten physically active men performed drop jumps from four different heights (0.20, 0.40, 0.60 and 0.80 m). A force plate measured the vGRF, while perception of impact was evaluated through Borg's Ratings of Perceived Exertion. Higher values of maximum vGRF (Fy_max) and impulse of the first 50 ms (I_50), and reduced time to reach Fy_max indicate increased external forces as drop jump height raised. Perception of impact increased gradually with increasing jump height for I_50. Fy_max and I_50 showed moderate to strong correlations to perceived load for 70% and 90% of participants, respectively. Higher and different intensity of stimulus facilitated the perception of impact, presenting moderate to strong correlations to kinetic parameters related to external load during landing from drop jump. Perception of higher impacts could be used as a surrogate to monitor 'real' impacts and possibly also for managing impact-related injury risk.

Risk and Protective Factors for Middle- and Long-Distance Running-Related Injury

BACKGROUND

Despite a rapidly growing body of research, a systematic evidence compilation of the risk and protective factors for middle- and long-distance running-related injury (RRI) was lacking.

OBJECTIVES

Our objective was to compile the evidence about modifiable and non-modifiable training-related and behavioral risk and protective factors for middle- and long-distance RRI.

METHODS

We searched five databases (PubMed, CINAHL, MEDLINE, SPORTDiscus, and PsycINFO) for the dates 1 January 1970 to 31 December 2015, inclusive, for original peer-reviewed articles. The eligible designs were cross-sectional, case-control, longitudinal observational studies, and randomized controlled trials involving runners competing at distances from ≥800 m to ≤42.2 km. Outcomes were any specific and/or general RRI, and exposures included training-related and behavioral factors. We extracted authors and date, study design, injury type(s), descriptors and comparators for each exposure, and results and measures of association from the selected studies. Methodological quality was independently appraised using two separate checklists: a modified checklist for observational study designs and the Physiotherapy Evidence Database (PEDro) scale for randomized controlled trials.

RESULTS

Among 73 articles eligible for inclusion, 19 (26.0%) and 30 (41.0%) were of high or satisfactory methodological quality, respectively. As a non-modifiable exposure, a history of previous injury was found to be associated with an increased risk of both general and specific RRI. In terms of modifiable exposures, irregular and/or absent menstruation was found to be associated with an increased risk of stress fracture development, whereas the use of oral contraceptives was found to be associated with a decreased risk. High clinical, methodological, and statistical heterogeneity meant it was not feasible to estimate a pooled effect size across similar studies.

CONCLUSIONS

A history of previous injury was associated with an increased risk of both general and specific RRI. The use of oral contraceptives was found to be associated with a decreased risk of skeletal stress fracture. Conversely, irregular and/or absent menstruation was associated with an increased risk. The varied effect directions and/or a number of statistically insignificant results associated with the majority of factors hindered our ability to draw any definitive conclusions about their relationship to RRI risk.

Modulations of Foot and Ankle Frontal Kinematics for Breaking and Propulsive Movement Characteristics during Side-Step Cutting with Varying Midsole Thicknesses

This study is aimed at determining the effects of midsole thickness on movement characteristic during side cutting movement. Fifteen athletes performed side-step cutting while wearing shoes with varying midsole thicknesses. Temporal-spatial and ground reaction force variables as well as foot and ankle frontal kinematics were used to describe breaking and propulsive movement characteristics and modulation strategies. Regardless of midsole thickness, temporal-spatial variables and breaking and propulsive force during side cutting were statistically unchanged. Significantly greater peaks of ankle inversion and plantarflexion with a thicker sole and greater midtarsal pronation with a thinner sole were observed. Current results demonstrated that hypotheses formed solely based on material testing were insufficient to understand the adaptations in human movement because of the redundancy of the neuromusculoskeletal system. Participants were able to maintain temporal-spatial performance during side cutting while wearing shoes with midsoles of varying thicknesses. Increased pronation for a thinner sole might help reduce the force of impact but might be associated with an increased risk of excessive stress on soft tissue. Increased peak of ankle inversion and plantarflexion for a thicker sole may be unfavorable for the stability of ankle joint. Information provided in human movement testing is crucial for understanding factors associated with movement characteristics and injury and should be considered in the future development of shoe design.

Current Soccer Footwear, Its Role in Injuries and Potential for Improvement

Soccer is the most popular sport in the world and generates great financial revenue. It is also a sport whose practice has evolved considerably in terms of intensity and commitment, and in which the intrinsic risk of injury (not directly related to an interaction with the environment) is particularly high. In this context, the cleated shoe as a major component of soccer equipment may play a key role in the overexposure to injury. Soccer shoe evolution is all the more challenging, because design and mechanical structure differ in many points compared to other modern shoes developed for sports such as running, tennis and basketball. This critical review aims to elucidate the characteristics of modern soccer footwear and their possible link to soccer-specific injuries, focusing on the following areas: (1) ergonomics, comfort and proprioception; (2) shoe mechanical characteristics; (3) field surfaces and shoe design.

Full Step Cycle Kinematic and Kinetic Comparison of Barefoot Walking and a Traditional Shoe Walking in Healthy Youth: Insights for Barefoot Technology

Objective

Barefoot technology shoes are becoming increasingly popular, yet modifications are still needed. The present study aims to gain valuable insights by comparing barefoot walking to neutral shoe walking in a healthy youth population.

Methods

28 healthy university students (22 females and 6 males) were recruited to walk on a 10-meter walkway both barefoot and in neutral running shoes at their comfortable walking speed. Full step cycle kinematic and kinetic data were collected using an 8-camera motion capture system.

Results

In the early stance phase, the knee extension moment (MK1), the first peak absorbed joint power at the knee joint (PK1), and the flexion angle of knee/dorsiflexion angle of the ankle were significantly reduced when walking in neutral running shoes. However, in the late stance, barefoot walking resulted in decreased hip joint flexion moment (MH2), second peak extension knee moment (MK3), hip flexors absorbed power (PH2), hip flexors generated power (PH3), second peak absorbed power by knee flexors (PK2), and second peak anterior-posterior component of joint force at the hip (APFH2), knee (APFK2), and ankle (APFA2).

Conclusions

These results indicate that it should be cautious to discard conventional elements from future running shoe designs and rush to embrace the barefoot technology fashion.

Transitioning to Minimal Footwear: a Systematic Review of Methods and Future Clinical Recommendations

BACKGROUND

Recent interest in barefoot running has led to the development of minimalist running shoes that are popular in distance runners. A careful transition to these shoes has been suggested and examined in the literature. However, no guidelines based on systematic evidence have been presented. The purpose of this review is to systematically examine the methods employed in the literature to transition to minimal footwear (MFW), as well as the outcomes to these studies in distance runners. In addition, MFW transition guidelines for future clinical practice will be presented based on observations from this review.

METHODS

A systematic database search was employed using PubMed online as the primary database. Twenty papers were included in the final review.

RESULTS

All studies implemented a prospective transition design to MFW with a detail of this transition provided, which increased MFW exposure up to an average of 60% (30-100%) at completion. Only 8/20 studies included injury prevention exercises, and 9/20 included gait retraining. The main outcomes of this transition included limited positive evidence of transitioning into MFW for running economy (n = 4 studies) and muscle development (n = 5). The injury incidence comparing running during the MFW transition (17.9 injuries per 100 participants) to matched participants in conventional running shoes (13.4 injuries per 100) appears equivocal (p = 0.219; effect size phi (φ) = 0.06 [very small]). Finally, several important recommendations for clinical practice and future research have been presented.

CONCLUSIONS

It is hoped that this paper will present important first steps in unifying the process of transitioning to MFW, both for academic and clinical use.

Effects of Footwear and Fatigue on Running Economy and Biomechanics in Trail Runners

PURPOSE

This study aimed to examine the effects of footwear and neuromuscular fatigue induced by short distance trail running (TR) on running economy (RE) and biomechanics in well-trained and traditionally shod runners.

METHODS

RE, vertical and leg stiffness (Kvert and Kleg), as well as foot strike angle were measured from two 5-min treadmill running stages performed at a speed of 2.5 (with 10% grade, uphill running) and 2.77 m·s (level running) before and after an 18.4-km TR exercise (approximately 90% of maximal heart rate) in runners wearing minimalist shoes (MS), MS plus added mass (MSm), or traditional shoes (TS). Maximal voluntary contraction torque of knee extensors and perceived muscle pain were also evaluated before and after TR.

RESULTS

Maximal voluntary contraction values decreased after TR in all footwear conditions (P < 0.001), indicating the occurrence of neuromuscular fatigue. In the nonfatigued condition, runners exhibited a better RE only during level running in MS and MSm (i.e., combined effects of shoe mass and midsole geometry), in association with significant decreases in foot strike angle (P < 0.05). However, no significant difference in RE was observed between shod conditions after TR during either uphill or level running. Decreases in both Kvert/Kleg and foot strike angle were more pronounced during running in MS and MSm (P < 0.05) compared with TS, whatever the period. Calf pain increased after TR when wearing MS and MSm compared with TS (P < 0.05).

CONCLUSIONS

These findings indicated specific alterations in RE and biomechanics over time during the MS and MSm conditions compared with the TS condition. Future studies are warranted to evaluate the relationship between RE and footwear with fatigue in experienced minimally shod runners.

Preventing running-related injuries using evidence-based online advice: the design of a randomised-controlled trial

Introduction

Running-related injuries (RRIs) are frequent and can lead to cessation of health promoting activities. Several risk factors for RRIs have been identified. However, no successful injury prevention programme has been developed so far. Therefore, the aim of the present study is to investigate the effect of an evidence-based online injury prevention programme on the number of RRIs.

Methods and analysis

The INSPIRE trial is a randomised-controlled trial with a 3-month follow-up. Both novice and more experienced runners, aged 18 years and older, who register for a running event (distances 5 km up to 42.195 km) will be asked to participate in this study. After completing the baseline questionnaire, participants will be randomised into either the intervention group or control group. Participants in the intervention group will get access to the online injury prevention programme. This prevention programme consists of information on evidence-based risk factors and advices to reduce the injury risk. The primary outcome measure is the number of self-reported RRIs in the time frame between registration for a running event and 1 month after the running event. Secondary outcome measures include the running days missed due to injuries, absence of work or school due to injuries, and the injury location.

Ethics and dissemination

An exemption for a comprehensive application is obtained by the Medical Ethical Committee of the Erasmus University Medical Centre Rotterdam, Netherlands. The results of the study will be published in peer-reviewed journals and presented on international congresses.

Trial registration number

NTR5998. Pre-results

Six-week transition to minimalist shoes improves running economy and time-trial performance

OBJECTIVES

This study investigated if gradually introducing runners to minimalist shoes during training improved running economy and time-trial performance compared to training in conventional shoes. Changes in stride rate, stride length, footfall pattern and ankle plantar-flexor strength were also investigated.

DESIGN

Randomised parallel intervention trial.

METHODS

61 trained runners gradually increased the amount of running performed in either minimalist (n=31) or conventional (n=30) shoes during a six-week standardised training program. 5-km time-trial performance, running economy, ankle plantar-flexor strength, footfall pattern, stride rate and length were assessed in the allocated shoes at baseline and after training. Footfall pattern was determined from the time differential between rearfoot and forefoot (TD_R-F) pressure sensors.

RESULTS

The minimalist shoe group improved time-trial performance (effect size (ES): 0.24; 95% confidence interval (CI): 0.01, 0.48; p=0.046) and running economy (ES 0.48; 95%CI: 0.22, 0.74; p<0.001) more than the conventional shoe group. There were no minimalist shoe training effects on ankle plantar-flexor concentric (ES: 0.11; 95%CI: -0.18, 0.41; p=0.45), isometric (ES: 0.23; 95%CI: -0.17, 0.64; p=0.25), or eccentric strength (ES: 0.24; 95%CI: -0.17, 0.65; p=0.24). Minimalist shoes caused large reductions in TD_R-F (ES: 1.03; 95%CI: 0.65, 1.40; p<0.001) but only two runners changed to a forefoot footfall. Minimalist shoes had no effect on stride rate (ES: 0.04; 95%CI: -0.08, 0.16; p=0.53) or length (ES: 0.06; 95%CI: -0.06, 0.18; p=0.35).

CONCLUSIONS

Gradually introducing minimalist shoes over a six-week training block is an effective method for improving running economy and performance in trained runners.

A framework for the etiology of running-related injuries

The etiology of running-related injury is important to consider as the effectiveness of a given running-related injury prevention intervention is dependent on whether etiologic factors are readily modifiable and consistent with a biologically plausible causal mechanism. Therefore, the purpose of the present article was to present an evidence-informed conceptual framework outlining the multifactorial nature of running-related injury etiology. In the framework, four mutually exclusive parts are presented: (a) Structure-specific capacity when entering a running session; (b) structure-specific cumulative load per running session; (c) reduction in the structure-specific capacity during a running session; and (d) exceeding the structure-specific capacity. The framework can then be used to inform the design of future running-related injury prevention studies, including the formation of research questions and hypotheses, as well as the monitoring of participation-related and non-participation-related exposures. In addition, future research applications should focus on addressing how changes in one or more exposures influence the risk of running-related injury. This necessitates the investigation of how different factors affect the structure-specific load and/or the load capacity, and the dose-response relationship between running participation and injury risk. Ultimately, this direction allows researchers to move beyond traditional risk factor identification to produce research findings that are not only reliably reported in terms of the observed cause-effect association, but also translatable in practice.

Body Mass and Weekly Training Distance Influence the Pain and Injuries Experienced by Runners Using Minimalist Shoes: A Randomized Controlled Trial

BACKGROUND

Minimalist shoes have been popularized as a safe alternative to conventional running shoes. However, a paucity of research is available investigating the longer-term safety of minimalist shoes.

PURPOSE

To compare running-related pain and injury between minimalist and conventional shoes in trained runners and to investigate interactions between shoe type, body mass, and weekly training distance.

STUDY DESIGN

Randomized clinical trial; Level of evidence, 2.

METHODS

Sixty-one trained, habitual rearfoot footfall runners (mean ± SD: body mass, 74.6 ± 9.3 kg; weekly training distance, 25 ± 14 km) were randomly allocated to either minimalist or conventional shoes. Runners gradually increased the time spent running in their allocated shoes over 26 weeks. Running-related pain intensity was measured weekly by use of 100-mm visual analog scales. Time to first running-related injury was also assessed.

RESULTS

Interactions were found between shoe type and weekly training distance for weekly running-related pain; greater pain was experienced with minimalist shoes ( P < .05), and clinically meaningful increases (>10 mm) were noted when the weekly training distance was more than 35 km/wk. Eleven of 30 runners sustained an injury in conventional shoes compared with 16 of 31 runners in minimalist shoes (hazard ratio, 1.64; 95% confidence interval, 0.63-4.27; P = .31). A shoe × body mass interaction was found for time to first running-related injury ( P = .01). For runners using minimalist shoes, relative to runners using conventional shoes, the risk of sustaining an injury became more likely with increasing body mass above 71.4 kg, and the risk was moderately increased (hazard ratio, 2.00; 95% confidence interval, 1.10-3.66; P = .02) for runners using minimalist shoes who had a body mass of 85.7 kg.

CONCLUSIONS

Runners should limit weekly training distance in minimalist shoes to avoid running-related pain. Heavier runners are at greater risk of injury when running in minimalist shoes. Registration: Australian New Zealand Clinical Trials Registry (ACTRN12613000642785).

16 Weeks of Progressive Barefoot Running Training Changes Impact Force and Muscle Activation in Habitual Shod Runners

Short-term effects of barefoot and simulated barefoot running have been widely discussed in recent years. Consequences of adopting barefoot running for a long period, including as a training approach, still remain unknown. The present study evaluated the influence of 16 weeks of progressive barefoot running training on impact force and muscle activation in habitual shod runners. Six habitual shod runners (3 men and 3 women, 29.5 ± 7.3 years) were tested barefoot (BF) and shod (SH), before and after 16 weeks of progressive barefoot running training. Tests consisted of running on instrumented treadmill at 9 km/h, for 10 minutes in each experimental condition. Nine data acquisitions (10 s) of vertical ground reaction force (VGRF) and electromyographic (EMG) signal were conducted in each experimental condition for each test. BF training was effective to alter VGRF and EMG parameters of running in habitual shod runners, regardless of footwear condition (SH or BF). The magnitude of first peak of VGRF (Fy1) and the impulse of the first 50 ms decreased after training for BF and SH (p<0.01). The activation reduced from PRE to POST training for four muscles in BF running (p<0.001), whereas only muscle gastrocnemius lateralis decreased significantly its activation (p<0.01) in SH running. A 16-week progressive barefoot running training seems to be an effective training strategy to reduce impact force, improve shock attenuation and to decrease muscle activation intensity, not only in BF running, but also in SH running, although BF condition seems to be more influenced by BF training.

Redistribution of Mechanical Work at the Knee and Ankle Joints During Fast Running in Minimalist Shoes

CONTEXT

Minimalist shoes have been suggested as a way to alter running biomechanics to improve running performance and reduce injuries. However, to date, researchers have only considered the effect of minimalist shoes at slow running speeds.

OBJECTIVE

To determine if runners change foot-strike pattern and alter the distribution of mechanical work at the knee and ankle joints when running at a fast speed in minimalist shoes compared with conventional running shoes.

DESIGN

Crossover study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty-six trained runners (age = 30.0 ± 7.9 years [age range, 18-40 years], height = 1.79 ± 0.06 m, mass = 75.3 ± 8.2 kg, weekly training distance = 27 ± 15 km) who ran with a habitual rearfoot foot-strike pattern and had no experience running in minimalist shoes.

INTERVENTION(S)

Participants completed overground running trials at 18 km/h in minimalist and conventional shoes.

MAIN OUTCOME MEASURE(S)

Sagittal-plane kinematics and joint work at the knee and ankle joints were computed using 3-dimensional kinematic and ground reaction force data. Foot-strike pattern was classified as rearfoot, midfoot, or forefoot strike based on strike index and ankle angle at initial contact.

RESULTS

We observed no difference in foot-strike classification between shoes (χ²₁ = 2.29, P = .13). Ankle angle at initial contact was less (2.46° versus 7.43°; t₂₅ = 3.34, P = .003) and strike index was greater (35.97% versus 29.04%; t₂₅ = 2.38, P = .03) when running in minimalist shoes compared with conventional shoes. We observed greater negative (52.87 J versus 42.46 J; t₂₄ = 2.29, P = .03) and positive work (68.91 J versus 59.08 J; t₂₄ = 2.65, P = .01) at the ankle but less negative (59.01 J versus 67.02 J; t₂₄ = 2.25, P = .03) and positive work (40.37 J versus 47.09 J; t₂₄ = 2.11, P = .046) at the knee with minimalist shoes compared with conventional shoes.

CONCLUSIONS

Running in minimalist shoes at a fast speed caused a redistribution of work from the knee to the ankle joint. This finding suggests that runners changing from conventional to minimalist shoes for short-distance races could be at an increased risk of ankle and calf injuries but a reduced risk of knee injuries.

Influence of the Heel-to-Toe Drop of Standard Cushioned Running Shoes on Injury Risk in Leisure-Time Runners: A Randomized Controlled Trial With 6-Month Follow-up

BACKGROUND

Modern running shoes are available in a wide range of heel-to-toe drops (ie, the height difference between the forward and rear parts of the inside of the shoe). While shoe drop has been shown to influence strike pattern, its effect on injury risk has never been investigated. Therefore, the reasons for such variety in this parameter are unclear.

PURPOSE

The first aim of this study was to determine whether the drop of standard cushioned running shoes influences running injury risk. The secondary aim was to investigate whether recent running regularity modifies the relationship between shoe drop and injury risk.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

Leisure-time runners (N = 553) were observed for 6 months after having received a pair of shoes with a heel-to-toe drop of 10 mm (D10), 6 mm (D6), or 0 mm (D0). All participants reported their running activities and injuries (time-loss definition, at least 1 day) in an electronic system. Cox regression analyses were used to compare injury risk between the 3 groups based on hazard rate ratios (HRs) and their 95% CIs. A stratified analysis was conducted to evaluate the effect of shoe drop in occasional runners (<6 months of weekly practice over the previous 12 months) versus regular runners (≥6 months).

RESULTS

The overall injury risk was not different among the participants who had received the D6 (HR, 1.30; 95% CI, 0.86-1.98) or D0 (HR, 1.17; 95% CI, 0.76-1.80) versions compared with the D10 shoes. After stratification according to running regularity, low-drop shoes (D6 and D0) were found to be associated with a lower injury risk in occasional runners (HR, 0.48; 95% CI, 0.23-0.98), whereas these shoes were associated with a higher injury risk in regular runners (HR, 1.67; 95% CI, 1.07-2.62).

CONCLUSION

Overall, injury risk was not modified by the drop of standard cushioned running shoes. However, low-drop shoes could be more hazardous for regular runners, while these shoes seem to be preferable for occasional runners to limit injury risk.

Injuries observed in a prospective transition from traditional to minimalist footwear: correlation of high impact transient forces and lower injury severity

OBJECTIVES

Minimalist running is increasing in popularity based upon a concept that it can reduce impact forces and decrease injury rates. The purpose of this investigation is to identify the rate and severity of injuries in runners transitioning from traditional to minimalist footwear. The secondary aims were to identify factors correlated with injuries.

METHODS

Fourteen habitually shod (traditional running shoes) participants were enrolled for this prospective study investigating injury prevalence during transition from traditional running shoes to 5-toed minimalist shoes. Participants were uninjured, aged between 22-41 years, and ran at least twenty kilometers per week in traditional running shoes. Participants were given industry recommended guidelines for transition to minimalist footwear and fit with a 5-toed minimalist running shoe. They completed weekly logs for identification of injury, pain using Visual Analogue Scale (VAS), injury location, and severity. Foot strike pattern and impact forces were collected using 3D motion analysis at baseline, 4 weeks, and 12 weeks. Injuries were scored according to a modified Running Injury Severity Score (RISS).

RESULTS

Fourteen runners completed weekly training and injury logs over an average of 30 weeks. Twelve of 14 (86%) runners sustained injuries. Average injury onset was 6 weeks (range 1-27 weeks). Average weekly mileage of 23.9 miles/week prior to transition declined to 18.3 miles/week after the transition. The magnitude of the baseline impact transient peak in traditional shoes and in minimalist shoes negatively correlated with RISS scores (r = -0.45, p = 0.055 and r = -0.53, p = 0.026, respectively).

CONCLUSION

High injury rates occurred during the transition from traditional to minimalist footwear. Non-compliance to transition guidelines and high injury rates suggest the need for improved education. High impact transient forces unexpectedly predicted lower modified RISS scores in this population.

Relationship between foot strike pattern, running speed, and footwear condition in recreational distance runners

Compared to competitive runners, recreational runners appear to be more prone to injuries, which have been associated with foot strike patterns. Surprisingly, only few studies had examined the foot strike patterns outside laboratories. Therefore, this study compared the foot strike patterns in recreational runners at outdoor tracks with previously reported data. We also investigated the relationship between foot strike pattern, speed, and footwear in this cohort. Among 434 recreational runners analysed, 89.6% of them landed with rearfoot strike (RFS). Only 6.9 and 3.5% landed with midfoot and forefoot, respectively. A significant shift towards non-RFS was observed in our cohort, when compared with previously reported data. When speed increased by 1 m/s, the odds of having forefoot strike and midfoot strike relative to RFS increased by 2.3 times and 2.6 times, respectively. Runners were 9.2 times more likely to run with a forefoot strike in minimalists compared to regular running shoes, although 70% of runners in minimalists continued to use a RFS. These findings suggest that foot strike pattern may differ across running conditions and runners should consider these factors in order to mitigate potential injury.

Self-Reported Minimalist Running Injury Incidence and Severity: A Pilot Study

INTRODUCTION

Minimalist running entails using shoes with a flexible thin sole and is popular in the United States. Existing literature disagrees over whether minimalist running shoes (MRS) improve perceived severity of injuries associated with running in traditional running shoes (TRS). Additionally, the perceived injury patterns associated with MRS are relatively unknown.

OBJECTIVES

To examine whether injury incidence and severity (ie, degree of pain) by body region change after switching to MRS, and to determine if transition times affect injury incidences or severity with MRS.

METHODS

Runners who were either current or previous users of MRS were recruited to complete an Internet-based survey regarding self-reported injury before switching to MRS and whether self-reported pain from that injury decreased after switching. Questions regarding whether new injuries developed in respondents after switching to MRS were also included. Analyses were calculated using t tests, Wilcoxon signed rank tests, and Fischer exact tests.

RESULTS

Forty-seven runners completed the survey, and 16 respondents reported injuries before switching to MRS. Among these respondents, pain resulting from injuries of the feet (P=.03) and knees (P=.01) decreased. Eighteen respondents (38.3%) indicated they sustained new injuries after switching to MRS, but the severity of these did not differ significantly from no injury. Neither time allowed for transition to MRS nor use or disuse of a stretching routine during this period was correlated with an increase in the incidence or severity of injuries.

CONCLUSION

After switching to MRS, respondents perceived an improvement in foot and knee injuries. Additionally, respondents using MRS reported an injury rate of 38.3%, compared with the approximately 64% that the literature reports among TRS users. Future studies should be expanded to determine the full extent of the differences in injury patterns between MRS and TRS.