A prospective comparison of lower extremity kinematics and kinetics between injured and non-injured collegiate cross country runners

Relationship between ankle dorsiflexion range of motion and sprinting and jumping ability in young athletes

OBJECTIVES

To investigate the relationship between predicted risk of injury based on the dichotomous classification of the weight-bearing lunge (WBL) test scores and variables related to jumping and sprinting ability in young athletes. Furthermore, to compare the impact of the classical dichotomous classification versus a more specific quartile subdivision of the WBL test scores on the explored variables.

DESIGN

Cross-sectional study.

PARTICIPANTS

125 healthy athletes (mean age 10.38 (SD = 2.28) years) were recruited.

MAIN OUTCOME MEASURES

Ankle dorsiflexion was evaluated with the WBL test, jumping distance with the standing long jump (SLJ) test, and maximal running speed with the 14-m and 28-m sprint test.

RESULTS

Athletes with WBL test scores lower than 10 cm exhibited significantly poorer results for the SLJ test as well as lower 14-m and 28-m sprint times than those with WBL test scores higher than 10 cm (p < 0.05). Likewise, when WBL test scores were subdivided by quartiles, a positive trend between range of motion and improved performance was shown.

CONCLUSIONS

Reduced ankle dorsiflexion mobility may affect sprinting and jumping ability in young athletes. In addition, a more detailed classification of ankle restriction by quartiles is proposed in this study in order to prevent injury and enhance athletic performance.

Neuromuscular and trunk control mediate factors associated with injury in fatigued runners

This study aimed to determine how fatigue affects factors associated with injury, neuromuscular activity, and control in recreational runners. Previously identified injury risk factors were defined as peak vertical instantaneous loading rates (pVILR) for tibial stress fracture (TSF) and peak hip adduction (pHADD) for patellofemoral pain syndrome and iliotibial band syndrome. Kinematics, kinetics, and electromyography data were collected from 11 recreational runners throughout a fatiguing run. Three trials were collected in the first and final minutes of the run. Coactivation was quantified about the knee and ankle for the entire stance phase and anticipatory, weight acceptance (WA), and propulsion sub-phases of stance. Trunk control was quantified by the peak mediolateral lean, peak forward lean, and flexion range of motion (ROM). There were significant increases in pHADD and pVILR when fatigued. Significant decreases in coactivation around the knee were found over the entire stance phase, in the anticipatory phase, and WA phase. Coactivation decreased about the ankle during WA. Lateral trunk lean significantly increased when fatigued, but no significant changes were found in flexion ROM or lean. Mediation analyses showed changes in ankle coactivation during WA, and lateral trunk lean are significant influences on pVILR, a measure associated with TSF. Fatigue-induced adaptations of decreasing ankle coactivation during WA and increased lateral trunk lean may increase the likelihood of TSF. In this study, a fatiguing run influenced changes in control in recreational runners. Further investigation of causal fatigue-induced injuries is necessary to better understand the effects of coactivation and trunk control.

Preseason Vertical Center of Mass Displacement During Running and Bone Mineral Density Z-Score Are Risk Factors for Bone Stress Injury Risk in Collegiate Cross-country Runners

OBJECTIVES: To (1) assess relationships between running biomechanics, bone health, and bone stress injuries (BSIs), and (2) determine which variables constitute the most parsimonious BSI risk model among collegiate cross-country runners. DESIGN: Prospective, observational cohort study. METHODS: Running gait and bone mineral density (BMD) data from healthy collegiate cross-country runners were collected at preseason over 6 seasons. A generalized estimating equation model with backward selection was used to develop the most parsimonious model for estimating BSI risk, controlling for sex, running speed, and prior BSI. The variables assessed were spatiotemporal, ground reaction force, and joint kinematics, based on previous literature. Quasi-likelihood under the independence model criterion values and R2 values were used to select the best-fitting model. RESULTS: Data from 103 runners were included in the analysis. The best-fitting model included vertical center of mass (COM) displacement and BMD z-score. Injury risk increased with greater vertical COM displacement (unit = 0.5 cm; relative risk [RR] = 1.14; 95% confidence interval [CI]: 1.01, 1.29; P = .04) and decreased with greater BMD z-score (unit = 0.5; RR = 0.83; 95% CI: 0.72, 0.95; P = .007). The model performed similarly when step rate was included instead of vertical COM displacement. CONCLUSION: Vertical COM displacement and BMD z-score contributed to the best model for estimating risk the risk of bone stress injury in cross-country runners. Step rate was also an important variable for assessing injury risk. J Orthop Sports Phys Ther 2023;53(12):1-8. Epub 20 October 2023. doi:10.2519/jospt.2023.11860.

Running towards injury? A prospective investigation of factors associated with running injuries

BACKGROUND

Given the high incidence and heavy burden of running related injuries, large-scale, prospective multifactorial investigations examining potential risk factors are warranted. This study aimed to identify factors associated with running related injuries and to evaluate their potential in injury screening.

STUDY DESIGN

Prospective cohort study.

MATERIALS AND METHODS

Two hundred and seventy-four recreational runners were recruited. Clinical measures (strength, range of motion, foot position), injury and training history (via questionnaire), impact loading (via accelerometery) and running technique measures were collected at baseline. Runners were tracked for injury for one year via fortnightly check-ins. A binary logistic regression, (injury versus no injury), was performed for each variable univariably, and then adjusting for age, sex and mileage. A multivariable regression was also performed to evaluate the model's discriminative ability.

RESULTS

Of the 225 runners included in the final analysis 52% experienced a running related injury. Injury history in the past year, less navicular drop, and measures of running technique (knee, hip, and pelvis kinematics) were associated with increased odds of injury (p < .05). The multivariable logistic regression model was statistically significant, χ2(11) = 56.45, p < .001, correctly classifying 74% of cases with a sensitivity and specificity of 72% and 76%, respectively. The area under the receiver operating characteristic curve was 0.79 (CI95% = 0.73-0.85), demonstrating acceptable discriminative ability.

CONCLUSIONS

This study found a number of clinical and running technique factors to be associated with prospective running related injuries among recreational runners. With the exception of injury history, the factors identified as being significantly associated with injury may be modifiable and therefore, could form the basis of interventions. Range of motion, spatiotemporal parameters and strength measures were not associated with injury and thus their utilisation in injury prevention practices should be reconsidered.

Are alterations in running biomechanics associated with running injuries? A systematic review with meta-analysis

BACKGROUND

No systematic review has investigated the main biomechanical variables as predictors of running-related injuries.

OBJECTIVE

To investigate the main biomechanical variables associated with running-related injuries.

METHODS

Medline via PubMed, EMBASE, SPORTDiscus, Web of Science, and CINAHL were searched from inception until 1 November 2021. Each study included must have investigated the association of at least one biomechanical variable (kinetics, kinematics, electromyography, or pressure distribution) with running injuries. The meta-analysis was conducted, and a modified version of the Downs and Black Quality Index was used for methodological quality evaluation.

RESULTS

Across the 82 studies included, 5465 runners were investigated. The meta-analysis was conducted with 11 biomechanical variables from 51 articles (n=2395). The peak hip adduction angle was the sole biomechanical variable associated with running injury and was found to be higher in injured runners (0.57, 95% CI 0.21, 0.94) compared to uninjured runners. However, this result was highly influenced by two studies (out of five studies) conducted by the same group of authors.

CONCLUSION

Clinicians, coaches, and runners should be aware that minimal evidence supports that alterations of running biomechanics are associated with running-related injuries. Heterogeneity in evaluation conditions and inconsistency in the naming and definitions of biomechanical variables make definitive conclusions challenging.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO, CRD42017068839.

The "impacts cause injury" hypothesis: Running in circles or making new strides?

Some of the earliest biomechanics research focused on running and the ground reaction forces generated with each step. Research in running gait accelerated in the 1970's as the growing popularity in running increased attention to the musculoskeletal injuries sustained by runners. Despite decades of high-quality research, running remains the most common cause of exercise-related musculoskeletal injuries and rates of overuse running-related injuries (RRI) have not appreciably declined since the research began. One leading area of running gait research focuses on discrete variables derived from the vertical ground reaction force, such as the vertical loading rate. Across sub-disciplines of running gait research, vertical loading rate is often discussed as the primary and undisputed variable associated with RRI despite only low to moderate evidence that retrospectively or prospectively injured runners generate greater vertical loading rates than uninjured counterparts. The central thesis of this review is that relying on vertical loading rate is insufficient to establish causal mechanisms for RRI etiology. To present this argument, this review examines the history of the 'impacts cause injury' hypothesis, including a historical look at ground reaction forces in human running and the research from which this hypothesis was generated. Additionally, a synthesis of studies that have tested the hypothesis is provided and recommendations for future research are discussed. Although it is premature to reject or support the 'impacts cause injury' hypothesis, new knowledge of biomechanical risk factors for RRI will remain concealed until research departs from the current path or adopts new approaches to previous paradigms.

Aetiological Factors of Running-Related Injuries: A 12 Month Prospective "Running Injury Surveillance Centre" (RISC) Study

BACKGROUND

Running-related injuries (RRIs) are a prevalent issue for runners, with several factors proposed to be causative. The majority of studies to date are limited by retrospective study design, small sample sizes and seem to focus on individual risk factors in isolation. This study aims to investigate the multifactorial contribution of risk factors to prospective RRIs.

METHODS

Recreational runners (n = 258) participated in the study, where injury history and training practices, impact acceleration, and running kinematics were assessed at a baseline testing session. Prospective injuries were tracked for one year. Univariate and multivariate Cox regression was performed in the analysis.

RESULTS

A total of 51% of runners sustained a prospective injury, with the calf most commonly affected. Univariate analysis found previous history of injury < 1 year ago, training for a marathon, frequent changing of shoes (every 0-3 months), and running technique (non-rearfoot strike pattern, less knee valgus, greater knee rotation) to be significantly associated with injury. The multivariate analysis revealed previous injury, training for a marathon, less knee valgus, and greater thorax drop to the contralateral side to be risk factors for injury.

CONCLUSION

This study found several factors to be potentially causative of injury. With the omission of previous injury history, the risk factors (footwear, marathon training and running kinematics) identified in this study may be easily modifiable, and therefore could inform injury prevention strategies. This is the first study to find foot strike pattern and trunk kinematics to relate to prospective injury.

Isolated effects of footwear structure and cushioning on running mechanics in habitual mid/forefoot runners

The true differences between barefoot and shod running are difficult to directly compare because of the concomitant change to a mid/forefoot footfall pattern that typically occurs during barefoot running. The purpose of this study was to compare isolated effects of footwear structure and cushioning on running mechanics in habitual mid/forefoot runners running shod (SHOD), barefoot (BF), and barefoot on a foam surface (BF+FOAM). Ten habitually shod mid/forefoot runners were recruited (male = 8, female = 2). Repeated measures ANOVA (α = 0.05) revealed differences between conditions for only vertical peak active force, contact time, negative and total ankle joint work, and peak dorsiflexion angle. Post hoc tests revealed that BF+FOAM resulted in smaller vertical active peak magnitude and instantaneous vertical loading rate than SHOD. SHOD resulted in lower total ankle joint work than BF and BF+FOAM. BF+FOAM resulted in lower negative ankle joint work than either BF or SHOD. Contact time was shorter with BF than BF+FOAM or SHOD. Peak dorsiflexion angle was smaller in SHOD than BF. No other differences in sagittal joint kinematics, kinetics, or ground reaction forces were observed. These overall similarities in running mechanics between SHOD and BF+FOAM question the effects of footwear structure on habituated mid/forefoot running described previously.

Vertical Loading Rate Is Not Associated with Running Injury, Regardless of Calculation Method

INTRODUCTION

Loading rate (LR), the slope of the vertical ground reaction force (vGRF), is commonly used to assess running-related injury risk. However, the relationship between LR and running-related injuries, including bone stress injuries (BSI), is unclear. Inconsistent findings may result from the numerous LR calculation methods that exist and their application across different running speeds.

PURPOSE

This study aimed to assess the influence of calculation method and running speed on LR values and to determine the association of LR during healthy running with subsequent injury.

METHODS

Healthy preseason running data and subsequent injury records from Division I cross-country athletes ( n = 79) over four seasons (2015-2019) at 2.68 m·s -1 , preferred training pace, and 4.47 m·s -1 were collected. LR at each speed was calculated four ways: 1) maximum and 2) average slope from 20% to 80% of vGRF magnitude at impact peak (IP), 3) average slope from initial contact to IP, and 4) average slope from 3% to 12% of stance time. Linear mixed effects models and generalized estimation equations were used to assess LR associations.

RESULTS

LR values differed depending on speed and calculation method ( P value <0.001). The maximum slope from 20% to 80% of the vGRF at 4.47 m·s -1 produced the highest LR estimate and the average slope from initial contact to IP at 2.68 m·s -1 produced the lowest. Sixty-four injuries (20 BSI) were observed. No significant association was found between LR and all injuries or BSI across any calculation method ( P values ≥0.13).

CONCLUSIONS

Calculation method and running speed result in significantly different LR values. Regardless of calculation method, no association between LR and subsequent injury was identified. Thus, healthy baseline LR may not be useful to prospectively assess running-related injury risk.

Unsupervised Clustering Techniques Identify Movement Strategies in the Countermovement Jump Associated With Musculoskeletal Injury Risk During US Marine Corps Officer Candidates School

Musculoskeletal injuries (MSKI) are a significant burden on the military healthcare system. Movement strategies, genetics, and fitness level have been identified as potential contributors to MSKI risk. Screening measures associated with MSKI risk are emerging, including novel technologies, such as markerless motion capture (mMoCap) and force plates (FP) and allow for field expedient measures in dynamic military settings. The aim of the current study was to evaluate movement strategies (i.e., describe variables) of the countermovement jump (CMJ) in Marine officer candidates (MOCs) via mMoCap and FP technology by clustering variables to create distinct movement strategies associated with MSKI sustained during Officer Candidates School (OCS). 728 MOCs were tested and 668 MOCs (Male MOCs = 547, Female MOCs = 121) were used for analysis. MOCs performed 3 maximal CMJs in a mMoCap space with FP embedded into the system. De-identified MSKI data was acquired from internal OCS reports for those who presented to the OCS Physical Therapy department for MSKI treatment during the 10 weeks of OCS training. Three distinct clusters were formed with variables relating to CMJ kinetics and kinematics from the mMoCap and FPs. Proportions of MOCs with a lower extremity and torso MSKI across clusters were significantly different (p < 0.001), with the high-risk cluster having the highest proportions (30.5%), followed by moderate-risk cluster (22.5%) and low-risk cluster (13.8%). Kinetics, including braking rate of force development (BRFD), braking net impulse and propulsive net impulse, were higher in low-risk cluster compared to the high-risk cluster (p < 0.001). Lesser degrees of flexion and shorter CMJ phase durations (braking phase and propulsive phase) were observed in low-risk cluster compared to both moderate-risk and high-risk clusters. Male MOCs were distributed equally across clusters while female MOCs were primarily distributed in the high-risk cluster. Movement strategies (i.e., clusters), as quantified by mMoCap and FPs, were successfully described with MOCs MSKI risk proportions between clusters. These results provide actionable thresholds of key performance indicators for practitioners to use for screening measures in classifying greater MSKI risk. These tools may add value in creating modifiable strength and conditioning training programs before or during military training.

Effects of Foot-Core Training on Foot-Ankle Kinematics and Running Kinetics in Runners: Secondary Outcomes From a Randomized Controlled Trial

This study investigated the effectiveness of an 8-week foot-core exercise training program on foot-ankle kinematics during running and also on running kinetics (impact loads), with particular interest in biomechanical outcomes considered risk factors for running-related injuries in recreational runners. A single-blind, randomized, controlled trial was conducted with 87 recreational runners randomly allocated to either the control (CG) or intervention (IG) group and assessed at baseline and after 8 weeks. The IG underwent foot-core training 3 times/week, while the CG followed a placebo lower-limb stretching protocol. The participants ran on a force-instrumented treadmill at a self-selected speed while foot-segment motion was captured simultaneously with kinetic measurements. After the intervention, there were statistically significant changed in foot biomechanics, such as: IG participants strike the ground with a more inverted calcaneus and a less dorsiflexed midfoot than those in the CG; at midstance, ran with a less plantarflexed and more adducted forefoot and a more abducted hallux; and at push-off, ran with a less dorsiflexed midfoot and a less adducted and more dorsiflexed hallux. The IG runners also had significantly decreased medial longitudinal arch excursion (p = 0.024) and increased rearfoot inversion (p = 0.037). The 8-week foot-core exercise program had no effect on impact (p = 0.129) and breaking forces (p = 0.934) or on vertical loading rate (p = 0.537), but it was positively effective in changing foot-ankle kinematic patterns.”

Can a Modified Y-Balance Test Predict Running Overuse Injuries over the Course of a Division I Collegiate Cross-Country Season?

BACKGROUND

Collegiate distance runners often suffer from running overuse injuries (ROI). The Y-Balance Test (YBT) has the potential to predict ROI risk in collegiate runners.

PURPOSE

To investigate whether a preseason clinical assessment of dynamic balance, through a modified version of the YBT (mYBT), can predict risk of ROIs during one NCAA Division I cross-country (XC) season.

STUDY DESIGN

Prospective case-control study.

METHODS

Participants from a Division I XC team were screened for mYBT performance in four directions: anterior (AN), posteromedial (PM), posterolateral (PL), and posterior (PO). ROIs were tracked over the course of the XC season. Receiver operating characteristic (ROC) curve analysis (α = 0.05) was utilized to investigate the effectiveness of the mYBT in predicting injury risk.

RESULTS

Nine (5 female, 4 male) of 29 runners developed an ROI during the XC season. Five components of the mYBT were found to predict injuries, including normalized nondominant PO score (AUC = 0.756, p = 0.03; RR = 1.90), AN raw difference and limb asymmetry (AUC = 0.808, p = 0.01), and PM raw difference and limb asymmetry in males (AUC = 0.958, p = 0.02).

CONCLUSION

Specific components of the mYBT can help predict the risk of developing a running overuse injury over one Division I XC season.

LEVEL OF EVIDENCE

Screening, Level 3.

Risk Factors for Injuries in Runners: A Systematic Review of Foot Strike Technique and Its Classification at Impact

Background:

It has been suggested that foot strike technique (FST) at initial contact is related to running-related injuries (RRIs).

Purpose:

To explore the relationship between FST and RRIs.

Study Design:

Systematic review; Level of evidence, 3.

Methods:

A systematic electronic search was performed using MEDLINE, PubMed, SPORTDiscus, Scopus, and Web of Science databases. Included were studies published in the English language that explored the relationship between FST and RRIs between January 1960 and November 2020. Results were extracted and collated. The Grading of Recommendations, Assessment, Development and Evaluation approach was applied to synthesize the quality of evidence.

Results:

We reviewed 13 studies exploring the relationship between FST and RRIs. Of these, 6 studies reported FST categorically (foot strike pattern [FSP]), and 7 reported continuous measures (foot contact angle, ankle flexion angle, and strike index). Three of the 6 studies looking at categorical FSP found rearfoot strikers have a significantly greater retrospective injury rate than do non– rearfoot strikers, with 1 other study noting a greater risk associated with midfoot and forefoot strike. Regarding the continuous measures of FST, only 1 of the 7 studies reported a significant relationship with RRIs.

Conclusion:

There was low evidence to suggest a relationship between FST (or its subcategories of categorical FSP and continuous measures) and RRIs. While two-thirds of the categorical studies found a relationship between FSP and RRIs, these studies were very low quality, with limitations such as retrospective study design, low participant numbers, and poor FSP assessment methods. More large-scale prospective studies are required.

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.

Association Between Knee- and Hip-Extensor Strength and Running-Related Injury Biomechanics in Collegiate Distance Runners

CONTEXT

Running-related injuries are common in distance runners. Strength training is used for performance enhancement and injury prevention. However, the association between maximal strength and distance-running biomechanics is unclear.

OBJECTIVE

To determine the relationship between maximal knee- and hip-extensor strength and running biomechanics previously associated with injury risk.

DESIGN

Cross-sectional study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 36 collegiate distance runners (26 men, 10 women; age = 20.0 ± 1.5 years, height = 1.74 ± 0.09 m, mass = 61.97 ± 8.26 kg).

MAIN OUTCOME MEASURE(S)

Strength was assessed using the 1-repetition maximum (1RM) back squat and maximal voluntary isometric contractions of the knee extensors and hip extensors. Three-dimensional running biomechanics were assessed overground at a self-selected speed. Running variables were the peak instantaneous vertical loading rate; peak forward trunk-lean angle; knee-flexion, internal-rotation, and -abduction angles and internal moments; and hip-extension, internal-rotation, and -adduction angles and internal moments. Separate stepwise linear regression models were used to examine the associations between strength and biomechanical outcomes (ΔR2) after accounting for sex, running speed, and foot-strike index.

RESULTS

Greater 1RM back-squat strength was associated with a larger peak knee-flexion angle (ΔR2 = 0.110, ΔP = .045) and smaller peak knee internal-rotation angle (ΔR2 = 0.127, ΔP = .03) and internal-rotation moment (ΔR2 = 0.129, ΔP = .03) after accounting for sex, speed, and foot-strike index. No associations were found between 1RM back-squat strength and vertical loading rate, trunk lean, or hip kinematics and kinetics. Hip- and knee-extensor maximal voluntary isometric contractions were also not associated with any biomechanical variables.

CONCLUSIONS

Greater 1RM back-squat strength was weakly associated with a larger peak knee-flexion angle and smaller knee internal-rotation angle and moment in collegiate distance runners. Runners who are weaker in the back-squat exercise may exhibit running biomechanics associated with the development of knee-related injuries.

Do knee abduction kinematics and kinetics predict future anterior cruciate ligament injury risk? A systematic review and meta-analysis of prospective studies

BACKGROUND

To systematically review the association between knee abduction kinematics and kinetics during weight-bearing activities at baseline and the risk of future anterior cruciate ligament (ACL) injury.

METHODS

Systematic review and meta-analysis according to PRISMA guidelines. A search in the databases MEDLINE (PubMed), CINAHL, EMBASE and Scopus was performed. Inclusion criteria were prospective studies including people of any age, assessing baseline knee abduction kinematics and/or kinetics during any weight-bearing activity for the lower extremity in individuals sustaining a future ACL injury and in those who did not.

RESULTS

Nine articles were included in this review. Neither 3D knee abduction angle at initial contact (Mean diff: -1.68, 95%CI: - 4.49 to 1.14, ACL injury n = 66, controls n = 1369), peak 3D knee abduction angle (Mean diff: -2.17, 95%CI: - 7.22 to 2.89, ACL injury n = 25, controls n = 563), 2D peak knee abduction angle (Mean diff: -3.25, 95%CI: - 9.86 to 3.36, ACL injury n = 8, controls n = 302), 2D medial knee displacement (cm; Mean diff:: -0.19, 95%CI: - 0,96 to 0.38, ACL injury n = 72, controls n = 967) or peak knee abduction moment (Mean diff:-10.61, 95%CI: - 26.73 to 5.50, ACL injury n = 54, controls n = 1330) predicted future ACL injury.

CONCLUSION

Contrary to clinical opinion, our findings indicate that knee abduction kinematics and kinetics during weight-bearing activities may not be risk factors for future ACL injury. Knee abduction of greater magnitude than that observed in the included studies as well as factors other than knee abduction angle or moment, as possible screening measures for knee injury risk should be evaluated in future studies.

Shoe feature recommendations for different running levels: A Delphi study

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

Biomechanical risk factors for running-related injury differ by sample population: A systematic review and meta-analysis

BACKGROUND

The role of biomechanical variables of running gait in the development of running related injury has not been clearly elucidated. Several systematic reviews have examined running biomechanics and its association with particular running related injuries. However, due to retrospective designs, inferences into the cause of these injuries are limited. Although prospective studies have been completed, no quantitative analysis pooling these results has been completed.

METHODS

A systematic review of MEDLINE, CINAHL, and PubMed was completed. Articles included used prospective study designs, human subjects currently completing a regular running program, and a minimum 12-week follow-up period. Excluded articles had no biomechanical data reported, participants who were beginning runners or military recruits, or had an intervention provided.

FINDINGS

Thirteen studies met these criteria. Pooled analyses were completed if two or more studies were available with samples that investigated the same sex and competition level. A qualitative synthesis was completed when pooled analysis was not possible. Five unique running samples were identified and allowed for pooled analyses of variables in mixed-sex collegiate runners and female recreational runners. Moderate evidence exists for increased hip adduction and reduced peak rearfoot eversion as risk factors for running related injury in female recreational runners. Variables differed in other samples of runners.

INTERPRETATION

A runner's sex and competition level may affect the relationship between biomechanical factors and the development of running related injury. Hip adduction and rearfoot eversion may be important factors related to running related injury in female recreational runners. Further investigation of biomechanical factors in running injury is warranted.

Associations between biomechanical and clinical/anthropometrical factors and running-related injuries among recreational runners: a 52-week prospective cohort study

BACKGROUND

The purpose of this exploratory study was to investigate whether runners with certain biomechanical or clinical/anthropometrical characteristics sustain more running-related injuries than runners with other biomechanical or clinical/anthropometrical characteristics.

METHODS

The study was designed as a prospective cohort with 52-weeks follow-up. A total of 224 injury-free, recreational runners were recruited from the Gothenburg Half Marathon and tested at baseline. The primary exposure variables were biomechanical and clinical/anthropometrical measures, including strength, lower extremity kinematics, joint range of motion, muscle flexibility, and trigger points. The primary outcome measure was any running-related injury diagnosed by a medical practitioner. Cumulative risk difference was used as measure of association. A shared frailty approach was used with legs as the unit of interest. A total of 448 legs were included in the analyses.

RESULTS

The cumulative injury incidence proportion for legs was 29.0% (95%CI = 24.0%; 34.8%). A few biomechanical and clinical/anthropometrical factors influence the number of running-related injuries sustained in recreational runners. Runners with a late timing of maximal eversion sustained 20.7% (95%CI = 1.3; 40.0) more injuries, and runners with weak abductors in relation to adductors sustained 17.3% (95%CI = 0.8; 33.7) more injuries, compared with the corresponding reference group.

CONCLUSIONS

More injuries are likely to occur in runners with late timing of maximal eversion or weak hip abductors in relation to hip adductors.

Validity and Reliability of 2-Dimensional Video-Based Assessment to Analyze Foot Strike Pattern and Step Rate During Running: A Systematic Review

CONTEXT

Two-dimensional (2D) video-based analysis is often used by clinicians to examine the foot strike pattern (FSP) and step rate in runners. Reliability and validity of 2D video-based analysis have been questioned.

OBJECTIVE

To synthesize the psychometric properties of 2D video-based analysis for assessing runners' FSP and step rate while running.

DATA SOURCES

Medline/PubMed, Science Direct, Embase, EBSCOHost/CINAHL, and Scielo were searched from their inception to August 2018.

STUDY SELECTION

Studies were included if (1) they were published in English, French, Portuguese or Spanish; (2) they reported at least 1 psychometric property (validity and/or reliability) of 2D video-based analysis to assess running kinematics; and (3) they assessed FSP or step rate during running.

STUDY DESIGN

Systematic review.

LEVEL OF EVIDENCE

Level 2.

DATA EXTRACTION

Studies were screened for methodological (MacDermid checklist) and psychometric quality (COSMIN checklist) by 2 independent raters.

RESULTS

Eight studies, with a total of 702 participants, were included. Seven studies evaluated the reliability of 2D video to assess FSP and found very good to excellent reliability (0.41 ≤ κ ≤ 1.00). Two studies reported excellent reliability for the calculation of step rate (0.75 ≤ intraclass correlation coefficient [ICC] ≤ 1.00). One study demonstrated excellent concurrent validity between 2D and 3D (gold standard) motion capture systems to determine FSP (Gwet agreement coefficient [AC] > 0.90; ICC > 0.90), and another study found excellent concurrent validity between 2D video and another device to calculate step rate (0.84 ≤ ICC ≤ 0.95).

CONCLUSION

Strong evidence suggests that 2D video-based analysis is a reliable method for assessing FSP and quantifying step rate, regardless of the experience of the assessor. Limited evidence exists on the validity of 2D video-based analysis in determining FSP and calculating step rate during running.

Influence of Aging on Lower Extremity Sagittal Plane Variability During 5 Essential Subphases of Stance in Male Recreational Runners

BACKGROUND

Interjoint coordination variability is a measure of the ability of the human system to regulate multiple movement strategies. Normal aging may reduce variability, resulting in a less adaptive system. Additionally, when older runners are asked to run at speeds greater than preferred, this added constraint may place older runners at greater risk for injury.

OBJECTIVES

To examine the influence of normal aging on coordination variability across 5 distinct subphases of stance in runners during preferred and fixed speeds.

METHODS

Twelve older (60 years of age or older) and 12 younger (30 years of age or younger) male recreational runners volunteered for this cross-sectional study. Three-dimensional gait analyses were collected at preferred and fixed speeds. Stance phase was divided into 5 subphases: (SP1) loading response, (SP2) peak braking, (SP3) peak compression, (SP4) midstance, and (SP5) peak propulsion. Continuous relative phase variability for sagittal plane joint pairs-hip-knee, knee-ankle, and hip-ankle-was calculated. Repeated-measures linear mixed models were employed to compare variability for each joint pair.

RESULTS

An age-by-stance subphase interaction was found for knee-ankle (P<.01) and hip-ankle (P<.01) pairs, while main effects for age and stance subphase were found for the hip-knee pair (P<.05). Specifically, loading response and peak braking variability were lower in older runners and greater across stance for knee-ankle and hip-ankle pairs, while midstance was lowest in the hip-knee pair for older and younger runners. No effects for running pace were found.

CONCLUSION

Less adaptive movement strategies seen in older runners may partially contribute to the increased eccentric stresses during periods of high load. J Orthop Sports Phys Ther 2019;49(3):171-179. Epub 30 Nov 2018. doi:10.2519/jospt.2019.8419.

Ground reaction force metrics are not strongly correlated with tibial bone load when running across speeds and slopes: Implications for science, sport and wearable tech

INTRODUCTION

Tibial stress fractures are a common overuse injury resulting from the accumulation of bone microdamage due to repeated loading. Researchers and wearable device developers have sought to understand or predict stress fracture risks, and other injury risks, by monitoring the ground reaction force (GRF, the force between the foot and ground), or GRF correlates (e.g., tibial shock) captured via wearable sensors. Increases in GRF metrics are typically assumed to reflect increases in loading on internal biological structures (e.g., bones). The purpose of this study was to evaluate this assumption for running by testing if increases in GRF metrics were strongly correlated with increases in tibial compression force over a range of speeds and slopes.

METHODS

Ten healthy individuals performed running trials while we collected GRFs and kinematics. We assessed if commonly-used vertical GRF metrics (impact peak, loading rate, active peak, impulse) were strongly correlated with tibial load metrics (peak force, impulse).

RESULTS

On average, increases in GRF metrics were not strongly correlated with increases in tibial load metrics. For instance, correlating GRF impact peak and loading rate with peak tibial load resulted in r = -0.29±0.37 and r = -0.20±0.35 (inter-subject mean and standard deviation), respectively. We observed high inter-subject variability in correlations, though most coefficients were negligible, weak or moderate. Seventy-six of the 80 subject-specific correlation coefficients computed indicated that higher GRF metrics were not strongly correlated with higher tibial forces.

CONCLUSIONS

These results demonstrate that commonly-used GRF metrics can mislead our understanding of loading on internal structures, such as the tibia. Increases in GRF metrics should not be assumed to be an indicator of increases in tibial bone load or overuse injury risk during running. This has important implications for sports, wearable devices, and research on running-related injuries, affecting >50 scientific publications per year from 2015-2017.

Knee Joint Kinematics and Kinetics During Walking and Running After Surgical Achilles Tendon Repair

BACKGROUND

Despite the increasing incidence of Achilles tendon (AT) ruptures, there is a lack of information on the possible risks associated with regular running and walking for exercise after an injury. There are some known kinematic gait changes after an AT rupture, especially at the knee. However, it is not clear whether runners with AT ruptures may be at risk for secondary knee injuries during shod or barefoot running/walking.

PURPOSE/HYPOTHESIS

The purpose of this study was to compare the kinematics and kinetics of barefoot walking and barefoot and shod running between athletes with a history of AT ruptures and a healthy control group. We hypothesized that there would be increased knee joint loads in the affected limb of the AT rupture group, especially during shod running.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten patients who had undergone surgical treatment of a unilateral acute AT rupture (6.1 ± 3.7 years postoperatively ) and 10 control participants were matched according to age, sex, physical activity, weight, height, and footfall type. The kinematics and kinetics of barefoot walking and barefoot and shod running were recorded using a high-speed motion capture system synchronized with force platforms.

RESULTS

The main outcome measures were lower extremity joint angles and moments during the stance phase of walking and running. After AT repair, athletes had increased internal knee abduction moments during shod and barefoot running compared with the healthy control group (P < .05, η2 > 0.14). There were no significant differences in kinematics and kinetics during walking between the AT rupture and healthy control groups (P ≥ .05).

CONCLUSION

After an AT rupture, athletes had increased internal knee abduction moments during running compared with the healthy control group.

CLINICAL RELEVANCE

The increased abduction loads on the knee in patients with an AT rupture could lead to further running-related injuries. However, barefoot walking may be used as a proprioceptive exercise without an increased risk of overuse injuries in these patients.