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

Does accelerometer location influence recreational runners' response to an accelerometer-based biofeedback gait re-education system?

Running is one of the most popular exercise modalities worldwide. However, injuries remain prevalent and are reported as a reason for running cessation. Research has demonstrated that load-based biofeedback systems may be able to reduce the loading experienced during running, potentially decreasing injury occurrence or enhancing rehabilitation. This study aimed to examine if varying accelerometer location in a load-based visual biofeedback system altered participants ability to reduce loading (peak tibial and sacral accelerations). Participants (n = 27), were randomly divided into 1 of three conditions; tibial, sacral, or treadmill-based biofeedback. In each condition, participants ran for 6 minutes (baseline), followed by 10 minutes with biofeedback (location varying based on group), and for a further 6 minutes without biofeedback. Linear mixed models that included time and biofeedback location as fixed effects, and participants as a random effect, demonstrated a significant main effect for time (p < 0.001) and biofeedback location (p = 0.05) for peak tibial accelerations, and a significant effect of time for peak sacral accelerations (p < 0.001). Practically, it appears that all biofeedback locations were effective at reducing both tibial and sacral peak accelerations and may have utility in the prevention and rehabilitation of running injuries.

Variability Among Individual Male Runners Influences Cumulative Loading More Than Foot Strike Type

BACKGROUND

Foot strike type affects running mechanics and may influence overuse injury occurrence. Measuring the interaction between cumulative load and foot strike type may provide additional information that could increase understanding of injury mechanisms.

HYPOTHESIS

There will be no differences in cumulative loading between runners using rearfoot strike (RFS) and nonrearfoot strike (NRFS) patterns. NRFS runners will have a greater stride rate. There will be differences in per stride metrics of select lower extremity mechanics.

STUDY DESIGN

Observational laboratory study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Thirty male participants (age, 22.7 ± 2.9 years; height, 1.79 ± 0.07 m; mass, 70.7 ± 7.86 kg; mean ± SD) ran on an instrumented treadmill for 5 km at 3.15 m/s with their preferred foot strike type (14 RFS, 16 NRFS). Stride rate, foot strike angle, loading rate (LR), per stride and per kilometer (cumulative) vertical ground-reaction force (VGRF) impulse, impact peak, absolute peak, knee negative work, and ankle negative work were calculated and compared across time and between groups.

RESULTS

Per stride differences were seen for stance time, foot strike angle, and LR (greater for RFS runners, P = 0.003). Per stride and cumulative ankle and knee negative work showed significant differences (greater ankle negative work for NRFS runners, P < 0.001 [per stride and cumulative], greater knee negative work for RFS runners, P = 0.01 per stride, P = 0.008 cumulative).

CONCLUSION

Ankle and knee loading metrics showed differences in per stride and cumulative metrics between foot strike groups. Individual variability in VGRF loading patterns was more apparent than group distinctions. The common perception that NRFS runners have a higher stride rate was not supported.

CLINICAL RELEVANCE

Individual loading patterns, not just foot strike type, and training session characteristics related to cumulative load should be considered when assessing injury risk.

Can Ground Reaction Force Variables Preidentify the Probability of a Musculoskeletal Injury in Collegiate Distance Runners?

The incidence of lower extremity injuries in collegiate distance runners is ∼20%. Identification of a runner sustaining a potential injury remains challenging. This exploratory, cross-institutional study sought to determine whether ground reaction force (GRF) characteristics during steady-state running could identify competitive collegiate distance runners who would later sustain lower extremity injuries. Normative boundaries for 10 GRF variables during braking and propulsion were established for noninjured runners using median ± scaled median absolute deviation. A subanalysis was conducted on runners with and without impact peaks in vertical GRF to mitigate the influence of impact peaks on GRF variables. We hypothesized that prior to injury, runners who later developed an injury would have more GRF variables outside of the normative boundaries than noninjured runners. Using Cliff's method, a rank-based, nonparametric method for comparing 2 independent groups, we found no statistically significant difference between the number of variables outside the boundaries for injured and noninjured runners overall (P = .17). However, injured runners without impact peaks had more variables outside the normative boundaries than noninjured runners (P < .001). This novel analytical approach demonstrates the potential for preidentifying collegiate distance runners without impact peaks who may be at risk for injury.

Effect of double- density foot orthoses on ground reaction forces and lower limb muscle activities during running in adults with and without pronated feet

BACKGROUND

The analysis of ground reaction forces and muscle activities during walking or running can help clinicians decide on the usage of foot orthoses, particularly in individuals with pronated feet. Here, we aimed to investigate the effects of double- density foot orthoses on running kinetics and lower limb muscle activities in adults with and without pronated feet.

METHODS

Forty male adults with pronated feet (PF: n = 20, age = 25.4 ± 0.3 years, body-mass-index [BMI] = 23.3 ± 1.2 kg/m2) and without pronated feet (WPF: n = 20, age = 26.4 ± 1.0 years, BMI = 24.0 ± 0.7 kg/m2) volunteered to participate in this study. The study was registered with the Iranian Registry of Clinical Trials (IRCT20220129053865N1). Ground reaction forces (Fx, Fy, Fz) and lower limb muscle activities (e.g., m. gastrocnemius) were recorded using surface electromyography (EMGs) during running at a constant speed of 3.2 m/s over an 18-m walkway with an embedded force plate. EMGs were normalized to maximum voluntary isometric contractions.

RESULTS

Test-retest reliability for running speed data was excellent for PF and WPF groups and for the entire study cohort with intraclass correlation coefficients > 0.95. The 2-way ANOVA revealed lower peak Fz (p = 0.011; d = 1.226), lower time-to-peak for Fx (p = 0.023, d = 1.068), Fy (p = 0.025, d = 1.056), and Fz (p = 0.045, d = 0.931) during running with foot orthoses in PF individuals. During the loading phase, PF and WPF exhibited lower gastrocnemius (WPF: p = 0.005, d = 1.608; PF: p = 0.001, d = 2.430 ) and vastus medialis (WPF: p < 0.001, d = 2.532; PF: p < 0.001, d = 2.503) activity when running with foot orthoses.

CONCLUSIONS

Although double- density foot orthoses resulted in some beneficial biomechanical effects such as lower muscle activation (e.g., m. vastus medialis) in individuals with PF, foot orthoses constructions need further modifications to achieve even better running mechanics to enhance performance and lower limbinjury occurrence.

TRIAL REGISTRATION

IRCT20220129053865N1 (Registration date 19/08/2024).

Field-Based Gait Retraining to Reduce Impact Loading Using Tibial Accelerometers in High-Impact Recreational Runners: A Feasibility Study

This study investigated the feasibility of a field-based gait retraining program using real-time axial peak tibial acceleration (PTA) feedback in high-impact recreational runners and explored the effects on running biomechanics and economy. We recruited eight recreational runners with high landing impacts to undertake eight field-based sessions with real-time axial PTA feedback. Feasibility outcomes were assessed through program retention rates, retraining session adherence, and perceived difficulty of the gait retraining program. Adverse events and pain outcomes were also recorded. Running biomechanics were assessed during field and laboratory testing at baseline, following retraining, and one-month post-retraining. Running economy was evaluated during laboratory testing sessions. Seven participants completed the retraining program, with one participant withdrawing due to illness before commencing retraining. An additional participant withdrew due to a foot injury after retraining. Adherence to retraining sessions was 100%. The mean (SD) perceived difficulty of the program was 4.3/10 (2.2). Following retraining, the mean axial PTA decreased in field (-29%) and laboratory (-33%) testing. The mean instantaneous vertical loading rate (IVLR) reduced by 36% post-retraining. At one-month follow-up, the mean axial PTA remained lower for field (-24%) and laboratory (-34%) testing, and the IVLR remained 36% lower than baseline measures. Submaximal oxygen consumption increased following gait retraining (+5.6%) but reverted to baseline at one month. This feasibility study supports the use of field-based gait retraining to reduce axial PTA and vertical loading rates in recreational runners without adversely affecting the running economy.

Effects of augmented feedback on landing mechanics after anterior cruciate ligament reconstruction in collegiate females compared to healthy controls

OBJECTIVE

To analyze if immediate visual and verbal feedback influenced landing mechanics during single and dual-task conditions in recreationally active females with a history of anterior cruciate ligament reconstruction (ACLr) compared to healthy controls.

DESIGN

Cross-sectional cohort study.

SETTING

Motion Laboratory.

PARTICIPANTS

33 college-aged females with two to five years status post-ACLr and 33 matched health controls.

MATERIALS AND METHODS

30 Drop landings were performed over one single session with immediate post-trial feedback followed by a retention trial on peak vGRF and symmetry.

MAIN OUTCOME MEASURES

Vertical ground reaction forces (vGRFs) during drop landing from a 50-cm platform and loading rate (LR) normalized to body weight.

RESULTS

For peak vGRF, there was a time effect from baseline, post-test, and transfer task trials. Based on baseline, post-test, and transfer tasks, there was a significant group-by-time interaction between the ACLr and a healthy group. For peak vGRF asymmetry, there was no time effect from baseline, post-test, and transfer task trials. There was a significant group effect for peak vGRF asymmetry. Total LR did not show a time effect from baseline, post-test, and transfer task. The ACLr group demonstrated higher LR compared to the health group.

CONCLUSIONS

Results demonstrated a reduction in peak vGRF and asymmetry in vGRF during drop landings with the inclusion of augmented feedback. The ACLr group demonstrated higher LR than the control group. Rehabilitation specialists may be able to incorporate targeted feedback as an intervention to help resolve landing asymmetries following ACLr.

Influence of Step Rate Manipulation on Foot Strike Pattern and Running Economy

CONTEXT

With the rise in distance running, there is an increasing interest in reducing running-related injuries and improving performance. Foot strike patterns (FSP) and step rate (SR) are key factors in managing the external forces generated during foot contact in running. Adjusting SR may help alter FSP and improve running economy (RE), yet its effects on recreational runners are not fully understood. Thus, this study aimed to examine if SR manipulations are sufficient to shift FSP and whether the manipulations change the RE.

DESIGN

Cross-sectional study.

METHODS

Eighteen healthy recreational runners' (age: 30.2 [7.6] y) foot strike angle was calculated using 2D video motion analysis, and submaximal VO2 was measured while running on a treadmill during preferred and adjusted (±5% and ±10%) SR conditions. Foot strike angle was used to predict strike index and quantify FSP, and submaximal VO2 was analyzed to determine RE.

RESULTS

Predicted strike index was significantly different between preferred SR and the -10% (P = .002), -5% (P = .002), and +10% (P < .001) SR conditions. Submaximal VO2 was significantly increased in the -10% (P < .001) and -5% (P = .002) SR conditions.

CONCLUSION

SR manipulations were sufficient to alter foot strike angle and predicted strike index in recreational runners, leading to moderate to significant changes in RE. These findings suggest that SR manipulation can be a useful tool for influencing FSPs and optimizing RE to enhance performance and reduce injury risk.

Bone Stress Injury Epidemiology and Risk Factors in Female Off-Road Runners: A Systematic Review

BACKGROUND

Off-road running is a growing sport with little research investigating injury profiles of female participants. Bone stress injuries (BSIs) are a particularly detrimental injury with little known about their incidence and risk factors in female off-road runners.

OBJECTIVE

Collate and review the available evidence reporting epidemiological data and risk factors associated with BSI in female off-road runners.

DESIGN

Systematic literature review, without meta-analyses.

DATA SOURCES

MEDLINE OVID, PubMed, SPORTDiscus, and MEDLINE EBSCO. Searches were finalized in July 2024.

ELIGIBILITY CRITERIA

Studies that reported injury surveillance statistics and/or risk factors associated with BSIs in female off-road runners.

RESULTS

Seventeen eligible studies were included, of which all reported surveillance statistics and 2 reported risk factors associated with BSI among 897 female runners. Owing to the scarcity of data, cross-country runners were included in the population of off-road runners. Most BSIs were high severity and in the lower leg, with an overall incidence ranging from 0 to 34.39 BSIs per 100,000 athlete-exposures and prevalence ranging from 0% to 40.9%. Study characteristics were reported alongside risk of bias, quality, and level of evidence assessment outcomes from varying tools. Eight significant intrinsic risk factors were associated with BSIs in female off-road runners: increasing age, disrupted menstruation, previous BSI, increased female triad risk, and lower calcium, vitamin D, and calorie intake.

DISCUSSION

Limited by the number of studies available reporting data on the specific target population, which highlights the need for performing high-quality prospective studies in the future, this review summarizes the current epidemiological data and risk factors associated with BSIs in female off-road runners.

Preferred temporal-spatial parameters, physical maturation, and sex are related to vertical and braking forces in adolescent long-distance runners

For adults, increasing cadence reduces ground reaction forces, but a lower preferred cadence does not predispose adults to experience higher ground reaction forces. Pubertal growth and motor control changes influence running mechanics, but it is unknown if preferred cadence or step length are associated with ground reaction forces for pre-adolescent and adolescent runners. Pre-adolescent and adolescent runners underwent an overground running analysis at a self-selected speed. Mixed model multiple linear regressions investigated the associations of preferred cadence, step length, physical maturation, and sex on ground reaction forces, while accounting for running speed and leg length. Running with a lower preferred cadence or longer preferred step length was associated with larger peak braking and vertical forces (p ≤ .01), being less physically mature was associated with larger vertical impact peak force and vertical loading rate (p ≤ .01), and being a male was associated with larger loading rates (p ≤ .01). A lower preferred cadence or longer preferred step length were associated with higher braking and vertical forces and being less physically mature or a male were associated with higher loading rates. An intervention to increase cadence/decrease step length could be considered if ground reaction forces are a concern for an adolescent runner.

The relationships between patellofemoral bone remodeling, cartilage composition, and vertical loading rate: PET/MRI in isolated patellofemoral osteoarthritis

OBJECTIVE

Loading is invariably an important factor of consideration for understanding the causality flow and parallel existence of articular cartilage and subchondral bone changes. The goal of this study was to investigate the patterns of subregional 18NaF-SUV vs. T1p-T2 associations and vertical ground reaction force loading rates; in isolated patellofemoral-joint-osteoarthritis (PFJ-OA) patients.

METHOD

Thirty-five isolated PFJ-OA patients, with no tibiofemoral involvement, underwent simultaneous scans in a 3.0T whole-body hybrid positron emission tomography-magnetic resonance imaging scanner. MRI Whole-Organ Magnetic Resonance Imaging Scoring assessments were performed to identify/confirm isolated PFJ-OA knees from bilateral scans. T1p-T2 relaxation and SUV values were automatically computed for both trochlear and patellar cartilage and subchondral bone subregions (deep, superficial, lateral, and medial). Maximum vertical impact loading rates (Loading-RateNorm) were calculated from walking trials. Relationships were explored between SUV uptake, T1p-T2 values, and Loading-RateNorm via linear mixed-effects modeling.

RESULTS

Significant and complex association patterns were noted between medial and lateral bone 18NaF-SUV uptakes vs. medial and lateral cartilage sub-regional T1p and T2. SUVMean and SUVMax were positively associated with deep cartilage subregional T1pand T2 values; and negatively associated with superficial cartilage subregional T1p-T2 values in both medial and lateral regions. Both medial and lateral bone 18NaF-SUVMean and SUVMax uptakes remained positively associated with the individual gait characteristics, i.e., peak vertical impact loading rates (Loading-RateNorm).

CONCLUSION

Evidence of simultaneous, complementary, cross-sectional associations between T1p-T2 values and peak vertical loading rates with 18NaF-SUV, have been rare in the isolated PFJ-OA cohort. The clinical implications of such novel associations remain of utmost importance from a gait retraining perspective.

Biomechanical Effects of the Badminton Split-Step on Forecourt Lunging Footwork

BACKGROUND

This research investigates the biomechanical impact of the split-step technique on forehand and backhand lunges in badminton, aiming to enhance players' on-court movement efficiency. Despite the importance of agile positioning in badminton, the specific contributions of the split-step to the biomechanical impact of lunging footwork still need to be determined.

METHODS

This study examined the lower limb kinematics and ground reaction forces of 18 male badminton players performing forehand and backhand lunges. Data were collected using the VICON motion capture system and Kistler force platforms. Variability in biomechanical characteristics was assessed using paired-sample t-tests and Statistical Parametric Mapping 1D (SPM1D).

RESULTS

The study demonstrates that the split-step technique in badminton lunges significantly affects lower limb biomechanics. During forehand lunges, the split-step increases hip abduction and rotation while decreasing knee flexion at foot contact. In backhand lunges, it increases knee rotation and decreases ankle rotation. Additionally, the split-step enhances the loading rate of the initial ground reaction force peak and narrows the time gap between the first two peaks.

CONCLUSIONS

These findings underscore the split-step's potential in optimizing lunging techniques, improving performance and reducing injury risks in badminton athletes.

Toe Box Shape of Running Shoes Affects In-Shoe Foot Displacement and Deformation: A Randomized Crossover Study

BACKGROUND

Long-distance running is popular but associated with a high risk of injuries, particularly toe-related injuries. Limited research has focused on preventive measures, prompting exploration into the efficacy of raised toe box running shoes.

PURPOSE

This study aimed to investigate the effect of running shoes with raised toe boxes on preventing toe injuries caused by distance running.

METHODS

A randomized crossover design involved 25 male marathon runners (height: 1.70 ± 0.02 m, weight: 62.6 + 4.5 kg) wearing both raised toe box (extended by 8 mm along the vertical axis and 3 mm along the sagittal axis) and regular toe box running shoes. Ground reaction force (GRF), in-shoe displacement, and degree of toe deformation (based on the distance change between the toe and the metatarsal head) were collected.

RESULTS

Wearing raised toe box shoes resulted in a significant reduction in vertical (p = 0.001) and antero-posterior (p = 0.015) ground reaction forces during the loading phase, with a notable increase in vertical ground reaction force during the toe-off phase (p < 0.001). In-shoe displacement showed significant decreased movement in the forefoot medial (p < 0.001) and rearfoot (medial: p < 0.001, lateral: p < 0.001) and significant increased displacement in the midfoot (medial: p = 0.002, lateral: p < 0.001). Impact severity on the hallux significantly decreased (p < 0.001), while impact on the small toes showed no significant reduction (p = 0.067).

CONCLUSIONS

Raised toe box running shoes offer an effective means of reducing toe injuries caused by long-distance running.

Athletic Injury Research: Frameworks, Models and the Need for Causal Knowledge

Within applied sports science and medicine research, many challenges hinder the establishment and detailed understanding of athletic injury causality as well as the development and implementation of appropriate athletic injury prevention strategies. Applied research efforts are faced with a lack of variable control, while the capacity to compensate for this lack of control through the application of randomised controlled trials is often confronted by a number of obstacles relating to ethical or practical constraints. Such difficulties have led to a large reliance upon observational research to guide applied practice in this area. However, the reliance upon observational research, in conjunction with the general absence of supporting causal inference tools and structures, has hindered both the acquisition of causal knowledge in relation to athletic injury and the development of appropriate injury prevention strategies. Indeed, much of athletic injury research functions on a (causal) model-blind observational approach primarily driven by the existence and availability of various technologies and data, with little regard for how these technologies and their associated metrics can conceptually relate to athletic injury causality and mechanisms. In this article, a potential solution to these issues is proposed and a new model for investigating athletic injury aetiology and mechanisms, and for developing and evaluating injury prevention strategies, is presented. This solution is centred on the construction and utilisation of various causal diagrams, such as frameworks, models and causal directed acyclic graphs (DAGs), to help guide athletic injury research and prevention efforts. This approach will alleviate many of the challenges facing athletic injury research by facilitating the investigation of specific causal links, mechanisms and assumptions with appropriate scientific methods, aiding the translation of lab-based research into the applied sporting world, and guiding causal inferences from applied research efforts by establishing appropriate supporting causal structures. Further, this approach will also help guide the development and adoption of both relevant metrics (and technologies) and injury prevention strategies, as well as encourage the construction of appropriate theoretical and conceptual foundations prior to the commencement of applied injury research studies. This will help minimise the risk of resource wastage, data fishing, p-hacking and hypothesising after the results are known (HARK-ing) in athletic injury research.

Predicting overstriding with wearable IMUs during treadmill and overground running

Running injuries are prevalent, but their exact mechanisms remain unknown largely due to limited real-world biomechanical analysis. Reducing overstriding, the horizontal distance that the foot lands ahead of the body, may be relevant to reducing injury risk. Here, we leverage the geometric relationship between overstriding and lower extremity sagittal segment angles to demonstrate that wearable inertial measurement units (IMUs) can predict overstriding during treadmill and overground running in the laboratory. Ten recreational runners matched their strides to a metronome to systematically vary overstriding during constant-speed treadmill running and showed similar overstriding variation during comfortable-speed overground running. Linear mixed models were used to analyze repeated measures of overstriding and sagittal segment angles measured with motion capture and IMUs. Sagittal segment angles measured with IMUs explained 95% and 98% of the variance in overstriding during treadmill and overground running, respectively. We also found that sagittal segment angles measured with IMUs correlated with peak braking force and explained 88% and 80% of the variance during treadmill and overground running, respectively. This study highlights the potential for IMUs to provide insights into landing and loading patterns over time in real-world running environments, and motivates future research on feedback to modify form and prevent injury.

Risk Factors for Running-Related Injury in High School and Collegiate Cross-country Runners: A Systematic Review

OBJECTIVE: To summarize and describe risk factors for running-related injuries (RRIs) among high school and collegiate cross-country runners. DESIGN: Descriptive systematic review. LITERATURE SEARCH: Four databases (Scopus, SPORTDiscus, CINAHL, Cochrane) were searched from inception to August 2023. STUDY SELECTION CRITERIA: Studies assessing RRI risk factors in high school or collegiate runners using a prospective design with at least 1 season of follow-up were included. DATA SYNTHESIS: Results across each study for a given risk factor were summarized and described. The NOS and GRADE frameworks were used to evaluate quality of each study and certainty of evidence for each risk factor. RESULTS: Twenty-four studies were included. Overall, study quality and certainty of evidence were low to moderate. Females or runners with prior RRI or increased RED-S (relative energy deficiency in sport) risk factors were most at risk for RRI, as were runners with a quadriceps angle of >20° and lower step rates. Runners with weaker thigh muscle groups had increased risk of anterior knee pain. Certainty of evidence regarding training, sleep, and specialization was low, but suggests that changes in training volume, poorer sleep, and increased specialization may increase RRI risk. CONCLUSION: The strongest predictors of RRI in high school and collegiate cross-country runners were sex and RRI history, which are nonmodifiable. There was moderate certainty that increased RED-S risk factors increased RRI risk, particularly bone stress injuries. There was limited evidence that changes in training and sleep quality influenced RRI risk, but these are modifiable factors that should be studied further in this population. J Orthop Sports Phys Ther 2024;54(2):1-13. Epub 16 November 2023. doi:10.2519/jospt.2023.11550.

Preinjury Knee and Ankle Mechanics during Running Are Reduced among Collegiate Runners Who Develop Achilles Tendinopathy

INTRODUCTION

Achilles tendinopathies (AT) are common in runners, but prospective data assessing running mechanics associated with developing AT are limited. Asymmetry in running mechanics is also considered a risk factor for injury, although it is unknown if the problematic mechanics occur on the injured limb only or are present bilaterally.

PURPOSE

This study aimed to prospectively identify differences in preinjury running biomechanics in collegiate runners who did and did not develop AT and determine if between-limb asymmetries were associated with which limb developed AT.

METHODS

Running gait data were obtained preseason on healthy collegiate cross-country runners, and AT incidence was prospectively recorded each year. Spatiotemporal, ground reaction forces, and joint kinematics and kinetics were analyzed. Linear mixed-effects models assessed differences in biomechanics between those who did and did not develop AT during the subsequent year. Generalized linear mixed-effects models determined if the asymmetry direction was associated with which limb developed an AT, with odds ratios (OR) and 95% confidence intervals (95% CI) reported.

RESULTS

Data from 106 runners were analyzed and 15 developed AT. Preinjury biomechanics of runners who developed AT showed less peak knee flexion (noninjured: 45.9° (45.2°-46.6°), injured: 43.2° (41.5°-44.9°), P < 0.001), ankle dorsiflexion (noninjured: 28.7° (28.0°-30.2°), injured: 26.0° (23.8°-28.3°), P = 0.01), and knee extensor moment (noninjured: -2.18 (N·m)·kg -1 (-2.24 to -2.12 (N·m)·kg -1 ), injured: -2.00 (N·m)·kg -1 (-2.17 to -1.84 (N·m)·kg -1 ), P = 0.02). The limb demonstrating less peak knee flexion had greater odds of sustaining an AT (OR, 1.29 (1.00-1.65), P = 0.05).

CONCLUSIONS

Knee and ankle kinematics, in addition to knee kinetics, were associated with developing an AT. Monitoring these mechanics may be useful for prospectively identifying runners at risk of developing AT.

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.

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

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

The effectiveness of telehealth gait retraining in addition to standard physical therapy treatment for overuse knee injuries in soldiers: a protocol for a randomized clinical trial

INTRODUCTION

Running is the most common cardiovascular exercise in the military. However, there is a high incidence of running-related overuse injuries that reduces military readiness. Gait retraining is a common intervention to treat running-related injuries, but the high cost of equipment and lack of clinician expertise and availability reduces utilization. Gait retraining intervention in a telehealth format might improve feasibility. The purpose of this randomized clinical trial is to determine the effectiveness of a telehealth gait retraining intervention on pain, self-reported function, and biomechanical risk factors for injury in service members who present to a Military Health System physical therapy clinic with an overuse knee injury.

METHODS

This is a parallel, two-arm, single-blind randomized clinical trial. The two independent variables are intervention (2 levels: telehealth gait retraining intervention with standard of care or only standard of care) and time (3 levels: baseline, 10 weeks or post-intervention, 14 weeks). Participants between the ages of 18 to 60 years will be included if they report knee pain during and/or after running to be anywhere from a 3 to a 7 on the numerical pain rating scale and demonstrate a rearfoot strike pattern. The primary dependent variables are as follows: (1) pain (worst pain during and/or after running) and (2) foot strike pattern (conversion rate from rearfoot to non-rearfoot foot strike pattern during running). Secondary outcomes include patient self-reported function and running biomechanics.

DISCUSSION

The effectiveness of a telehealth gait retraining intervention to reduce pain and modify foot strike pattern is not known. The results of this study may help determine the effectiveness and feasibility of a telehealth gait retraining intervention to reduce pain, change foot strike, improve function, and improve running gait biomechanics.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04269473 . Registered 05 February 2020.

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.

Dynamic postural control in injured collegiate cross-country runners is not associated with running-related injury

BACKGROUND

Biomechanical factors have been associated with running-related injury, but associations are unclear. Dynamic postural stability may be a factor related to injury that has not been studied extensively.

RESEARCH QUESTION

Does dynamic postural control differ in those with a history of running-related injury or those who go on to sustain a running-related injury?

METHODS

Sixty-five (45 injured; 20 uninjured) and fifty-eight (13 injured; 45 uninjured) collegiate cross-country runners were available for our retrospective and prospective analyses. Time to stabilization and dynamic postural stability index were collected during two separate jump landing tasks (forward and lateral direction) for each leg. Retrospective injury was tabulated by a running history survey. Prospective injuries were recorded by a licensed athletic trainer during the competitive season. Differences in postural stability were compared between injured and uninjured groups and between limbs using two-way ANOVA's. An overall group by leg comparison was completed for each task.

RESULTS

The non-dominant limb demonstrated better postural stability indices regardless of injury history. An interaction was observed between limbs and history of injury for the anterior-posterior time to stabilization for the lateral task. The non-dominant limb demonstrated better medio-lateral postural stability indices and time to stabilization during the lateral task, regardless of prospective injury.

SIGNIFICANCE

Dynamic postural stability was reduced in the dominant limb, but no clear differences were seen between injured and uninjured runners. This suggests dynamic postural stability may be altered in individuals with a history of a running-related injury, but no relationship to subsequent injury was substantiated. Further work is needed to understand how dynamic postural stability may be related to running-related injury.

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

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

Correspondence Between Values of Vertical Loading Rate and Oxygen Consumption During Inclined Running

Purpose

The aim of this study was to provide a theoretical model to predict the vertical loading rate (VLR) at different slopes and speeds during incline running.

Methods

Twenty-nine healthy subjects running at least once a week performed in a randomized order 4-min running trials on an instrumented treadmill at various speeds (8, 10, 12, and 14 km h−1) and slopes (− 20%, − 10%, − 5%, 0%, + 5%, + 10%, + 15%, + 20%). Heart rate, gas exchanges and ground reaction forces were recorded. The VLR was then calculated as the slope of the vertical force between 20 and 80% of the duration from initial foot contact to the impact peak.

Results

There was no difference in VLR between the four different uphill conditions at given running speeds, but it was reduced by 27% at 5% slope and by 54% at 10% slope for the same metabolic demand (similar $${\dot{\text{V}}\text{O}}_{{2}}$$ V ˙ O 2 ), when compared to level running. The average VLR measured at maximal aerobic intensity during level running would be decreased by 52.7% at + 5%, by 63.0% at + 10%, and by 73.3% at + 15% slope. Moreover, VLR was dependent on the slope in downhill conditions.

Conclusion

This study highlights the possibility to use uphill running to minimize rate of mechanical load (i.e., osteoarticular load) from foot impact on the ground and as a time-efficient exercise routine (i.e., same energy expenditure than in level running in less time).