Kinetic risk factors of running-related injuries in female recreational runners

Comparison of ground reaction forces as running speed increases between male and female runners

Introduction: The biomechanics associated with human running are affected by gender and speed. Knowledge regarding ground reaction force (GRF) at various running speeds is pivotal for the prevention of injuries related to running. This study aimed to investigate the gait pattern differences between males and females while running at different speeds, and to verify the relationship between GRFs and running speed among both males and females. Methods: GRF data were collected from forty-eight participants (thirty male runners and eighteen female runners) while running on an overground runway at seven discrete speeds: 10, 11, 12, 13, 14, 15 and 16 km/h. Results: The ANOVA results showed that running speed had a significant effect (p < 0.05) on GRFs, propulsive and vertical forces increased with increasing speed. An independent t-test also showed significant differences (p < 0.05) in vertical and anterior-posterior GRFs at all running speeds, specifically, female runners demonstrated higher propulsive and vertical forces than males during the late stance phase of running. Pearson correlation and stepwise multiple linear regression showed significant correlations between running speed and the GRF variables. Discussion: These findings suggest that female runners require more effort to keep the same speed as male runners. This study may provide valuable insights into the underlying biomechanical factors of the movement patterns at GRFs during running.

Enhancing running injury prevention strategies with real-time biofeedback: A systematic review and meta-analysis

The number of runners and the incidence of running-related injuries (RRIs) are on the rise. Real-time biofeedback gait retraining offers a promising approach to RRIs prevention. However, due to the diversity in study designs and reported outcomes, there remains uncertainty regarding the efficacy of different forms of feedback on running gait biomechanics. Three databases: MEDLINE, PUBMED, and SPORTDiscus were searched to identify relevant studies published up to March 2024, yielding 4646 articles for review. The quality of the included studies was assessed using the Downs and Black Quality checklist. Primary outcomes, including Peak Tibial Acceleration (PTA), Vertical Average Loading Rate (VALR), and Vertical Instantaneous Loading Rate (VILR), were analysed through meta-analysis. 24 studies met the inclusion criteria and were analysed in this review.17 used visual biofeedback (VB) while 14 chose auditory biofeedback (AB). The meta-analysis revealed a reduction in loading variables both immediately following the intervention and after extended training, with both visual and auditory feedback. Notably, the decrease in loading variables was more pronounced post-training and VB proved to be more effective than AB. Real-time biofeedback interventions are effective in lowering loading variables associated with RRIs. The impact is more substantial with sustained training, and VB outperforms AB in terms of effectiveness.

Running Biomechanics and Clinical Features Among Adolescent Athletes With Lower Leg Chronic Exertional Compartment Syndrome

OBJECTIVE

To compare clinical measures between patients with chronic exertional compartment syndrome (CECS) and healthy controls and evaluate running biomechanics, physical measurements, and exertional intracompartmental (ICP) changes in adolescent athletes with lower leg CECS.

DESIGN

Cross-sectional case-control study.

SETTING

Large tertiary care hospital and affiliated injury prevention center.

PARTICIPANTS

Forty-nine adolescents with CECS (39 F, 10 M; age: 16.9 ± 0.8 years; body mass index (BMI): 23.1 ± 2.9 kg/m 2 ; symptom duration: 8 ± 12 months) were compared with 49 healthy controls (39 F, 10 M; age: 6.9 ± 0.8 years; BMI: 20.4 ± 3.7 kg/m 2 ).

INTERVENTIONS

All participants underwent gait analyses on a force plate treadmill and clinical lower extremity strength and range of motion testing. Patients with chronic exertional compartment syndrome underwent Stryker monitor ICP testing.

MAIN OUTCOME MEASURES

Symptoms, menstrual history, and ICP pressures of the patients with CECS using descriptive statistics. Mann-Whitney U and χ 2 analyses were used to compare CECS with healthy patients for demographics, clinical measures, and gait biomechanics continuous and categorical outcomes, respectively. For patients with CECS, multiple linear regressions analyses were used to assess associations between gait biomechanics, lower extremity strength and range of motion, and with ICP measures.

RESULTS

The CECS group demonstrated higher mass-normalized peak ground reaction force measures (xBW) compared with controls (0.21 ± 0.05 xBW ( P < 0.001) and were more likely to have impact peak at initial contact ( P = 0.04). Menstrual dysfunction was independently associated with higher postexertion ICP (ß = 14.6; P = 0.02).

CONCLUSIONS

The CECS group demonstrated increased total force magnitude and vertical impact transient peaks. In women with CECS, menstrual dysfunction was independently associated with increased postexertion ICP. These biomechanical and physiological attributes may play a role in the development of CECS.

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.

The biomechanics of running and running styles: a synthesis

Running movements are parametrised using a wide variety of devices. Misleading interpretations can be avoided if the interdependencies and redundancies between biomechanical parameters are taken into account. In this synthetic review, commonly measured running parameters are discussed in relation to each other, culminating in a concise, yet comprehensive description of the full spectrum of running styles. Since the goal of running movements is to transport the body centre of mass (BCoM), and the BCoM trajectory can be derived from spatiotemporal parameters, we anticipate that different running styles are reflected in those spatiotemporal parameters. To this end, this review focuses on spatiotemporal parameters and their relationships with speed, ground reaction force and whole-body kinematics. Based on this evaluation, we submit that the full spectrum of running styles can be described by only two parameters, namely the step frequency and the duty factor (the ratio of stance time and stride time) as assessed at a given speed. These key parameters led to the conceptualisation of a so-called Dual-axis framework. This framework allows categorisation of distinctive running styles (coined 'Stick', 'Bounce', 'Push', 'Hop', and 'Sit') and provides a practical overview to guide future measurement and interpretation of running biomechanics.

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.

Using wearable technology data to explain recreational running injury: A prospective longitudinal feasibility study

OBJECTIVES

Investigate 1) if collecting and analysing wristwatch inertial measurement unit (IMU) and global positioning system (GPS) data using a commercially-available training platform was feasible in recreational runners and 2) which variables were associated with subsequent injury.

DESIGN

Prospective longitudinal cohort.

PARTICIPANTS

Healthy recreational runners.

MAIN OUTCOME MEASURES

We set a priori feasibility thresholds for recruitment (maximum six-months), acceptance (minimum 80%), adherence (minimum 70%), and data collection (minimum 80%). Participants completed three patient-reported outcome measures (PROMS) detailing their psychological health, sleep quality, and intrinsic motivation to run. We extracted baseline anthropometric, biomechanical, metabolic, and training load data from their IMU/GPS wristwatch for analysis. Participants completed a weekly injury status surveillance questionnaire over the next 12-weeks. Feasibility outcomes were analysed descriptively and injured versus non-injured group differences with 95% confidence intervals were calculated for PROM/IMU/GPS data.

RESULTS

149 participants consented; 86 participants completed (55 men, 31 women); 21 developed an injury (0.46 injuries/1000km). Feasibility outcomes were satisfied (recruitment = 47 days; acceptance = 133/149 [89%]; adherence = 93/133 [70%]; data collection = 86/93 [92%]). Acute load by calculated effort was associated with subsequent injury (mean difference -562.14, 95% CI -1019.42, -21.53).

CONCLUSION

Collecting and analysing wristwatch IMU/GPS data using a commercially-available training platform was feasible in recreational runners.

Peak instantaneous PlayerLoad metrics highlight movement strategy deficits in professional male soccer players

To investigate the influence of task, limb dominance and previous injury on single leg hop task performance and loading response, 25 professional male soccer players completed anterior, medial and lateral hop tests with an accelerometer at mid-calf. Performance outcome was defined as hop distance with loading response defined as the magnitude of, and time to peak instantaneous planar PlayerLoad. The performance was sensitive to task and previous injury (P < 0.001) but not limb dominance, with no evidence of bilateral asymmetry (P = 0.668). Despite impaired performance, previously injured players did not exhibit lower peak instantaneous PlayerLoad after impact in any plane (P ≥ 0.110). There was however a significantly (P = 0.001) longer time to peak medio-lateral loading after impact in previously injured players' affected limb. This observation was exacerbated when the injury was to the non-dominant limb (P = 0.041). Lower-limb accelerometry enhances understanding of movement strategy beyond task outcome, with practical implications in player screening and objective rehabilitation.

Use of subject-specific models to detect fatigue-related changes in running biomechanics: a random forest approach

Running biomechanics are affected by fatiguing or prolonged runs. However, no evidence to date has conclusively linked this effect to running-related injury (RRI) development or performance implications. Previous investigations using subject-specific models in running have demonstrated higher accuracy than group-based models, however, this has been infrequently applied to fatigue. In this study, two experiments were conducted to determine whether subject-specific models outperformed group-based models to classify running biomechanics during non-fatigued and fatigued conditions. In the first experiment, 16 participants performed four treadmill runs at or around the maximal lactate steady state. In the second experiment, nine participants performed five prolonged runs using commercial wearable devices. For each experiment, two segments were extracted from each trial from early and late in the run. For each participant, a random forest model was applied with a leave-one-run-out cross-validation to classify between the early (non-fatigued) and late (fatigued) segments. Additionally, group-based classifiers with a leave-one-subject-out cross validation were constructed. For experiment 1, mean classification accuracies for the single-subject and group-based classifiers were 68.2 ± 8.2% and 57.0 ± 8.9%, respectively. For experiment 2, mean classification accuracies for the single-subject and group-based classifiers were 68.9 ± 17.1% and 61.5 ± 11.7%, respectively. Variable importance rankings were consistent within participants, but these rankings differed from each participant to those of the group. Although the classification accuracies were relatively low, these findings highlight the advantage of subject-specific classifiers to detect changes in running biomechanics with fatigue and indicate the potential of using big data and wearable technology approaches in future research to determine possible connections between biomechanics and RRI.

Bone mineral density and its relationship with ground reaction force characteristics during gait in young adults with Prader-Willi Syndrome

Introduction

The incidence of osteopenia and osteoporosis is of concern in adults with Prader-Willi syndrome (PWS). Walking generates reaction forces that could stimulate bone mineralization and is popular in people with PWS. This study compared bone parameters and ground reaction forces (GRF) during gait between young adults with PWS and without PWS and explored associations between bone and GRFs during gait.

Methods

10 adults with PWS, 10 controls with obesity (OB) and 10 with normal weight (NW) matched on sex participated. Segmental and full body dual-energy x-ray absorptiometry scans provided femoral neck, spine, total body minus the head bone mineral density (BMD), bone mineral content (BMC). Vertical GRF, vertical impulse, posterior force and negative impulse were measured during 5 walking trials at a self-selected speed along a 10 m runway.

Results

Multivariate analyses of variance showed that adults with PWS (n = 7-8) had hip and body BMD and BMC comparable (p > .050) to NW and lower (p < .050) than OB. Adults with PWS showed slower speed than NW (p < .050) but similar to OB (p > .050). Adults with PWS presented lower absolute vertical GRF, vertical impulse and negative impulse than OB (p < .050). Pearson r correlations (p < .050) in those with PWS (n = 7-8) indicated that femoral neck BMC was associated with vertical GRF (r = 0.716), vertical impulse (r = 0.780), posterior force (r = -0.805), and negative impulse (r = -0.748). Spine BMC was associated with speed (r = 0.829) and body BMD was associated with speed (r = 0.893), and posterior force (r = -0.780).

Conclusions

Increased BMC in the femoral neck and body were associated with larger breaking forces during walking, a phenomenon normally observed at greater gait speeds. Faster walking speed was associated with greater BMC in the spine and body. Our preliminary results suggest that young adults with PWS could potentially benefit from faster walking for bone health; however, larger prospective studies are needed to confirm this.

The one-week and three-month reliability of acceleration outcomes from an insole-embedded inertial measurement unit during treadmill running

Inertial measurement units (IMUs) represent an exciting opportunity for researchers to broaden our understanding of running-related injuries, and for clinicians to expand their application of running gait analysis. The primary aim of our study was to investigate the 1-week (short-term) and 3-month (long-term) reliability of peak resultant, vertical, and anteroposterior accelerations derived from insole-embedded IMUs. The secondary aim was to assess the reliability of peak acceleration variability and left-right limb symmetry in all directions over the short and long term. A sample of healthy adult rearfoot runners (n = 23; age 41.7 ± 11.2 years) ran at a variety of speeds (2.5 m/s, 3.0 m/s, and 3.5 m/s) on a treadmill in standardised footwear with insole-embedded IMUs in each shoe. Peak accelerations exhibited good to excellent short-term reliability and moderate to excellent long-term reliability in all directions. Peak acceleration variability showed poor to good short- and long-term reliability, whereas the symmetry of peak accelerations demonstrated moderate to excellent and moderate to good short- and long-term reliability, respectively. Our results demonstrate how insole-embedded IMUs represent a viable option for clinicians to measure peak accelerations within the clinic.

Reference Values and Determinants of Spatiotemporal and Kinetic Variables in Recreational Runners

Background

Identifying atypical lower limb biomechanics may help prevent the occurrence or recurrence of running-related injuries. No reference values for spatiotemporal or kinetic variables in healthy recreational runners are available in the scientific literature to support clinical management.

Purpose

To (1) present speed- and sex-stratified reference values for spatiotemporal and kinetic variables in healthy adult recreational runners; (2) identify the determinants of these biomechanical variables; and (3) develop reference regression equations that can be used as a guide in a clinical context.

Study Design

Descriptive laboratory study.

Methods

This study involved 860 healthy recreational runners (age, 19-65 years [38.5% women]) tested on an instrumented treadmill at their preferred running speed in randomly allocated, standardized running shoes with either hard or soft cushioning. Twelve common spatiotemporal and kinetic variables-including contact time, flight time, duty factor, vertical oscillation, step cadence, step length, vertical impact peak (VIP), time to VIP, vertical average loading rate, vertical stiffness, peak vertical ground-reaction force (GRF), and peak braking force-were derived from GRF recordings. Reference values for each biomechanical variable were calculated using descriptive statistics and stratified by sex and running speed category (≤7, 8, 9, 10, 11, 12, 13, 14, and ≥15 km/h). Correlations and multiple regression analyses were performed to identify potential determinants independently associated with each biomechanical variable and generate reference equations.

Results

The mean running speed was 10.5 ± 1.3 km/h and 9 ± 1.1 km/h in men and women, respectively. While all potential predictors were significantly correlated with many of the 12 biomechanical variables, only running speed showed high correlations (r > 0.7). The adjusted R2 of the multiple regression equations ranged from 0.19 to 0.88.

Conclusion

This study provides reference values and equations that may guide clinicians and researchers in interpreting spatiotemporal and kinetic variables in recreational runners.

Clinical Relevance

The reference values can be used as targets for clinicians working with recreational runners in cases where there is a clinical suspicion of a causal relationship between atypical biomechanics and running-related injury.

Injury and performance related biomechanical differences between recreational and collegiate runners

Introduction

Running related injuries (RRI) are common, but factors contributing to running performance and RRIs are not commonly compared between different types of runners.

Methods

We compared running biomechanics previously linked to RRIs and performance between 27 recreational and 35 collegiate runners. Participants completed 5 overground running trials with their dominant limb striking a force plate, while outfitted with standardised footwear and 3-dimensional motion capture markers.

Results

Post hoc comparisons revealed recreational runners had a larger vertical loading rate (194.5 vs. 111.5 BW/s, p < 0.001) and shank angle (6.80 vs. 2.09, p < 0.001) compared with the collegiate runners who demonstrated greater vertical impulse (0.349 vs. 0.233 BWs, p < 0.001), negative impulse (-0.022 vs. -0.013 BWs, p < 0.001), positive impulse (0.024 vs. 0.014 BWs, p < 0.001), and propulsive force (0.390 vs. 0.333 BW, p = 0.002). Adjusted for speed, collegiate runners demonstrated greater total support moment (TSM), plantar flexor moment, knee extensor moment, hip extensor moment, and had greater proportional plantar flexor moment contribution and less knee extensor moment contribution to the TSM compared with recreational runners. Unadjusted for speed, collegiate runners compared with recreational had greater TSM and plantar flexor moment but similar joint contributions to the TSM.

Discussion

Greater ankle joint contribution may be more efficient and allow for greater capacity to increase speed. Improving plantarflexor function during running provides a strategy to improve running speed among recreational runners. Moreover, differences in joint kinetics and ground reaction force characteristics suggests that recreational and collegiate runners may experience different types of RRI.

The Association of Joint Power Kinetic Variables with Running Injuries: A Case-Control Study

Background

There is conflicting data on which kinetic variables are important to consider with running injuries. Furthermore, less is understood regarding differences in these variables when considering demographics such as age, sex, weight, and running speed. The primary question was what joint power kinetic variables were different between non-injured and injured runners.

Purpose

The purpose of this study was to identify if there were differences in joint power kinetic variables between non-injured runners and injured runners.

Study Design

Case-Control Study.

Methods

Kinetic data were collected on 122 runners (26 non-injured and 96 injured) over three years with a Bertec force plated treadmill and Qualisys 3D motion capture. The subjects were considered eligible if they self-identified themselves as runners or had running as a key component of their activity. The subjects ran at a comfortable, self-selected pace while two 10-second trials of recordings were used to calculate the means of peak power generated at the hips, knees, and ankles of each gait cycle. Foot strike was categorized by kinematic data. Two sample T-tests were used to compare peak power variables at the hips, knees, and ankles between non-injured and injured runners. Logistic regression analyses examined how a combination of demographics and peak power variables were associated with injuries.

Results

No peak power variable at the hip, knee, or ankle was significantly different between injured and non-injured runners (p=0.07-0.87). However, higher hip power absorbed was found to be protective against injuries (odds ratio, .16; 95% CI .025-.88) when considering demographics using a logistic regression model including sex, foot strike, BMI, speed, age, and power variables from the hip, knee, and ankle. The area under the ROC curve was .74, which is acceptable discrimination.

Conclusion

When controlling for age, sex, BMI, foot strike, and speed; higher hip power absorbed was found to be protective against injury. This could be due to the hip muscles' unique role in absorbing force during early stance phase.

Level of Evidence

3b©The Author(s).

The Effects of a Simple Sensor Reorientation Procedure on Peak Tibial Accelerations during Running and Correlations with Ground Reaction Forces

While some studies have found strong correlations between peak tibial accelerations (TAs) and early stance ground reaction forces (GRFs) during running, others have reported inconsistent results. One potential explanation for this is the lack of a standard orientation for the sensors used to collect TAs. Therefore, our aim was to test the effects of an established sensor reorientation method on peak Tas and their correlations with GRFs. Twenty-eight runners had TA and GRF data collected while they ran at a self-selected speed on an instrumented treadmill. Tibial accelerations were reoriented to a body-fixed frame using a simple calibration trial involving quiet standing and kicking. The results showed significant differences between raw and reoriented peak TAs (p < 0.01) for all directions except for the posterior (p = 0.48). The medial and lateral peaks were higher (+0.9-1.3 g), while the vertical and anterior were lower (-0.5-1.6 g) for reoriented vs. raw accelerations. Correlations with GRF measures were generally higher for reoriented TAs, although these differences were fairly small (Δr² = 0.04-0.07) except for lateral peaks (Δr² = 0.18). While contingent on the position of the IMU on the tibia used in our study, our results first showed systematic differences between reoriented and raw peak accelerations. However, we did not find major improvements in correlations with GRF measures for the reorientation method. This method may still hold promise for further investigation and development, given that consistent increases in correlations were found.

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.

Sex-related differences in hip and groin injuries in adult runners: a systematic review

OBJECTIVES

Hip/groin running-related injuries (RRIs) are relatively uncommon. It is unclear if runners of either sex are disproportionately affected. Our objective was to systematically review differences in hip/groin RRIs between males and females.

DATA SOURCES

A structured and comprehensive search of four medical literature databases was performed (PubMed, Embase, Ovid Medline, and CINAHL). Terms searched were as follows: risk, epidemiology, hip injury, groin injury, overuse injury, running, sprinting, and track and field.

STUDY SELECTION

Studies reporting sex-specific data on hip/groin RRIs in adult runners were included. Data was extracted and reviewed independently by two authors.

STUDY APPRAISAL AND DATA SYNTHESIS

Sex-specific injury rates, risk factors, and return to sport (RTS) following hip/groin RRI were extracted. Risk of bias was assessed using the Joanna-Briggs Institute Critical Appraisal Tool.

RESULTS

Ten studies with 7,353 total runners were included: 2,315 (47%) males and 2,559 (53%) females. The mean age of the included runners was 37.3 ± 8.9 years and the mean weekly running distance was 10.4 ± 8.4 km. Hip/groin injuries comprised 10.1% (491/4,874) of total RRIs, including 6.3% of RRIs sustained by males and 11.0% by females. Three studies reported significantly higher rates of hip/groin RRIs in female runners. One study reported significantly higher rates of gluteus medius and adductor RRIs for females and males, respectively. One study identified female sex as an independent risk factor for hip/groin RRIs. Three studies reported on RTS after hip/groin RRIs: the pooled RTS rate was 81.4% (57/70) at 1 to 368 days after injury.

LIMITATIONS

Data was pooled when possible; however, there was considerable clinical, methodological, and statistical heterogeneity across studies.

CONCLUSIONS

Hip/groin RRIs comprise a greater percentage of total injuries among injured female runners relative to males. Females may be at a higher risk for sustaining hip/groin RRIs though more research on risk factors and RTS is needed.

Using beat frequency in music to adjust running cadence in recreational runners: A randomized multiple baseline design

Running with music has been shown to acutely change cadence. However, it is unclear if the increased cadence remains long-term when running without music in an in-field situation. The aim of this 12-week study was to investigate the effect of a 4-week music running program on cadence, speed and heartrate during and after the music running program. Seven recreational runners with a cadence of <170 steps per minute were randomly assigned to a baseline and post-intervention period of different durations. During the intervention phase, the participants ran with a musical beat that was 7.5-10% higher than their mean cadence at the start of the study. Cadence, heartrate and running speed were measured twice a week during a 5-kilometer run with a watch, and were analyzed using randomization tests and visual data inspection. Two participants dropped-out due to shortage of time (n = 1) and an acute calf injury (n = 1). Cadence significantly increased during the intervention period (+8.5%), and remained elevated during the post-intervention period (+7.9% (p = .001)) in comparison with the baseline period. Heartrate and running speed did not significantly change during any period. This study among five participants shows that four weeks of running with a musical beat that is 7.5-10% higher than the preferred cadence may be an effective and feasible intervention to increase running cadence. Importantly, the increased cadence occurred without simultaneous increases in running speed and heartrate, hereby potentially reducing mechanical loading without increasing metabolic load.HighlightsRunning with a musical rhythm that is higher than the preferred cadence leads to an increased running cadence, without increasing heartrate and running speed.This cadence remains elevated for at least three to five weeks after the music intervention period.All individuals showed a practically relevant increase in cadence during and after the intervention.

Differences in kinetic variables between injured and uninjured rearfoot runners: A hierarchical cluster analysis

Running is a popular form of physical activity with a high incidence of running-related injuries. However, the etiology of running-related injuries remains elusive, possibly due to the heterogeneity of movement patterns. The purpose of this study was to investigate whether different clusters existed within a large group of injured and uninjured runners based on their kinetic gait patterns. A sample of 134 injured and uninjured runners were acquired from an existing database and 12 discrete kinetic and spatiotemporal variables which are commonly associated with running injuries were extracted from the ground reaction force waveforms. A principal components analysis followed by an unsupervised hierarchical cluster analysis was performed. The results revealed two distinct clusters of runners which were not associated with injury status (OR = 1.14 [0.57, 2.30], χ²  = 0.143, p = 0.706) or sex (OR = 1.72 [0.85, 3.49], χ²  = 2.3258, p = 0.127). These results suggest that while there appeared to be evidence for two distinct clusters within a large sample of injured and uninjured runners, there is no association between the kinetic variables and running related injuries.

What is the Effect of Changing Running Step Rate on Injury, Performance and Biomechanics? A Systematic Review and Meta-analysis

Background

Running-related injuries are prevalent among distance runners. Changing step rate is a commonly used running retraining strategy in the management and prevention of running-related injuries.

Objective

The aims of this review were to synthesise the evidence relating to the effects of changing running step rate on injury, performance and biomechanics.

Design

Systematic review and meta-analysis.

Data Sources

MEDLINE, EMBASE, CINAHL, and SPORTDiscus.

Results

Thirty-seven studies were included that related to injury (n = 2), performance (n = 5), and biomechanics (n = 36). Regarding injury, very limited evidence indicated that increasing running step rate is associated with improvements in pain (4 weeks: standard mean difference (SMD), 95% CI 2.68, 1.52 to 3.83; 12 weeks: 3.62, 2.24 to 4.99) and function (4 weeks: 2.31, 3.39 to 1.24); 12 weeks: 3.42, 4.75 to 2.09) in recreational runners with patellofemoral pain. Regarding performance, very limited evidence indicated that increasing step rate increases perceived exertion ( − 0.49,  − 0.91 to − 0.07) and awkwardness (− 0.72, − 1.38 to − 0.06) and effort (− 0.69, − 1.34, − 0.03); and very limited evidence that an increase in preferred step rate is associated with increased metabolic energy consumption (− 0.84, − 1.57 to − 0.11). Regarding biomechanics, increasing running step rate was associated with strong evidence of reduced peak knee flexion angle (0.66, 0.40 to 0.92); moderate evidence of reduced step length (0.93, 0.49 to 1.37), peak hip adduction (0.40, 0.11 to 0.69), and peak knee extensor moment (0.50, 0.18 to 0.81); moderate evidence of reduced foot strike angle (0.62, 034 to 0.90); limited evidence of reduced braking impulse (0.64, 0.29 to 1.00), peak hip flexion (0.42, 0.10 to 0.75), and peak patellofemoral joint stress (0.56, 0.07 to 1.05); and limited evidence of reduced negative hip (0.55, 0.20 to 0.91) and knee work (0.84, 0.48 to 1.20). Decreasing running step rate was associated with moderate evidence of increased step length (− 0.76, − 1.31 to − 0.21); limited evidence of increased contact time (− 0.95, − 1.49 to − 0.40), braking impulse (− 0.73, − 1.08 to − 0.37), and negative knee work (− 0.88, − 1.25 to − 0.52); and limited evidence of reduced negative ankle work (0.38, 0.03 to 0.73) and negative hip work (0.49, 0.07 to 0.91).

Conclusion

In general, increasing running step rate results in a reduction (or no change), and reducing step rate results in an increase (or no change), to kinetic, kinematic, and loading rate variables at the ankle, knee and hip. At present there is insufficient evidence to conclusively determine the effects of altering running step rate on injury and performance. As most studies included in this review investigated the immediate effects of changing running step rate, the longer-term effects remain largely unknown.

Prospero Registration

CRD42020167657.

Are impact accelerations during treadmill running representative of those produced overground?

BACKGROUND

Although many runners train overground, measuring impact accelerations on a treadmill may be advantageous for researchers and clinicians. Previous investigations of peak and rate of acceleration (peak_accel, rate_accel) during treadmill running compared to overground running have not examined both the relative consistency and absolute agreement of these measures, or the effect of treadmill stiffness.

RESEARCH QUESTION

(1) Are peak_accel and rate_accel produced during running on a stiff and less stiff treadmill 'representative' of those produced during overground running? (2) Are peak_accel and rate_accel measured on treadmills of different stiffness 'representative' of each other?

METHODS

Eighteen participants ran at a self-selected pace on three surfaces: Treadmill 1 (reduced stiffness), Treadmill 2 (increased stiffness) and overground on asphalt, whilst peak_accel and rate_accel were recorded at the shank and lower back. Relative consistency (ICC (3,1)), absolute agreement (Bland-Altman analysis) and systematic differences (ANOVA/Friedman's Tests) were assessed.

RESULTS

ICCs revealed moderate to excellent relative consistency in peak_accel and rate_accel between surfaces, with higher consistency for measures at the lower back. Absolute agreement was low, with the Bland Altman limits of agreement exceeding the clinical acceptable range for all comparisons. For systematic differences in means, peak_accel and rate_accel at the shank were significantly higher overground than on either treadmill; with no difference evident at the lower back. No differences were found for surface with respect to shank or lower back peak_accel and rate_accel between treadmills.

SIGNIFICANCE

Moderate to excellent relative consistency of peak_accel and rate_accel between the surfaces suggests that using different surfaces in research involving rank ordering of participants by acceleration magnitude may be acceptable (e.g. prospective studies examining if impact accelerations are related to injury). However, low absolute agreement indicates that data collected on treadmills of different stiffness and overground should not be used interchangeably (e.g. running-retraining studies).

One size does not fit all: Influence of sex and maturation on temporal-spatial parameters for adolescent long-distance runners

Runners and coaches are often interested in identifying the "ideal" running form to reduce the risk of injury and improve performance. While differences in pelvis and hip motion have been reported among adolescent female and male long-distance runners of different stages of physical maturation, the influence of sex and/or maturation on temporal-spatial parameters is unknown for adolescent runners. Adolescent runners of different stages of physical maturation (pre-, mid-, post-pubertal) completed an overground running analysis at a self-selected speed. We performed 2 × 3 ANCOVAs (covariate = running speed) to compare temporal-spatial parameters among sex and maturation groups. Pre-adolescents ran with higher cadences and shorter step lengths than mid- (p ≤ .01) and post-pubertal adolescents (p ≤ .01), respectively. Mid-pubertal males and post-pubertal females also ran with higher cadences and shorter step lengths than post-pubertal males (p ≤ .01). When step length was normalized to leg length, less physically mature runners demonstrated longer normalized step lengths (p ≤ .01). Caution is advised when using a "one-size-fits-all" approach for recommending an "ideal" cadence and/or step length for adolescent long-distance runners. A runner's sex, stage of physical maturation and leg length should be considered when assessing and prescribing cadence and/or step length.

The Effects of Cadence Manipulation on Joint Kinetic Patterns and Stride-to-Stride Kinetic Variability in Female Runners

Altering running cadence is commonly done to reduce the risk of running-related injury/reinjury. This study examined how altering running cadence affects joint kinetic patterns and stride-to-stride kinetic variability in uninjured female runners. Twenty-four uninjured female recreational runners ran on an instrumented treadmill with their typical running cadence and with a running cadence that was 7.5% higher and 7.5% lower than typical. Ground reaction force and kinematic data were recorded during each condition, and principal component analysis was used to capture the primary sources of variability from the sagittal plane hip, knee, and ankle moment time series. Runners exhibited a reduction in the magnitude of their knee extension moments when they increased their cadence and an increase in their knee extension moments when they lowered their cadence compared with when they ran with their typical cadence. They also exhibited greater stride-to-stride variability in the magnitude of their hip flexion moments and knee extension moments when they deviated from their typical running cadence (ie, running with either a higher or lower cadence). These differences suggest that runners could alter their cadence throughout a run in an attempt to limit overly repetitive localized tissue stresses.

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.

Running-induced fatigue and impact loading in runners: A systematic review and meta-analysis

This systematic review and meta-analysis aimed to synthesise and clarify the effect of running-induced fatigue on impact loading during running. Eight electronic databases were systematically searched until April 2021. Studies that analysed impact loading over the course of a run, in adult runners free of medical conditions were included. Changes in leg stiffness, vertical stiffness, shock attenuation, peak tibial accelerations, peak ground reaction forces (GRF) and loading rates were extracted. Subgroup analyses were conducted depending on whether participants were required to run to exhaustion. Thirty-six studies were included in the review, 25 were included in the meta-analysis. Leg stiffness decreased with running-induced fatigue (SMD -0.31, 95% CI -0.52, -0.08, moderate evidence). Exhaustive and non-exhaustive subgroups were different for peak tibial acceleration (Chi² = 3.79, p = 0.05), with limited evidence from exhaustive subgroups showing an increase in peak tibial acceleration with fatigue. Findings for vertical GRF impact peak and peak braking force were conflicting based on exhaustive and non-exhaustive protocols (Chi² = 3.83, p = 0.05 and Chi² = 5.10, p = 0.02, respectively). Moderate evidence suggests leg stiffness during running decreases with fatigue. Given the non-linear relationship between leg stiffness and running economy, this may have implications for performance.

Effect of the Innovative Running Shoes With the Special Midsole Structure on the Female Runners’ Lower Limb Biomechanics

The study aimed to research the effects of innovative running shoes (a high heel-to-toe drop and special structure of midsole) on the biomechanics of the lower limbs and perceptual sensitivity in female runners. Fifteen healthy female runners were recruited to run through a 145-m runway with planted force plates at one peculiar speed (3.6 m/s ± 5%) with two kinds of shoe conditions (innovative running shoes vs. normal running shoes) while getting biomechanical data. The perception of shoe characteristics was assessed simultaneously through a 15-cm visual analog scale. The statistical parametric mapping technique calculated the time-series parameters. Regarding 0D parameters, the ankle dorsiflexion angle of innovative running shoes at touchdown was higher, and the peak dorsiflexion angle, range of motion, peak dorsiflexion velocity, and plantarflexion moment on the metatarsophalangeal joint of innovative running shoes during running were significantly smaller than those of normal running shoes (all p < 0.001). In addition, the braking phase and the time of peak vertical force 1 of innovative running shoes were found to be longer than those of normal running shoes (both p < 0.05). Meanwhile, the average vertical loading rate 1, peak vertical loading rate 1, peak braking force, and peak vertical force 1 in the innovative running shoes were lower than those of the normal running shoes during running (both p < 0.01). The statistical parametric mapping analysis exhibited a higher ankle dorsiflexion angle (0–4%, p < 0.05), a smaller knee internal rotation angle (0–6%, p < 0.05) (63–72%, p < 0.05), a decreased vertical ground reaction force (11–17%, p = 0.009), and braking anteroposterior ground reaction force (22–27%, p = 0.043) for innovative running shoes than normal running shoes. Runners were able to perceive the cushioning of innovative running shoes was better than that of normal running shoes. These findings suggested combining the high offset and structure of the midsole would benefit the industrial utilization of shoe producers in light of reducing the risk of running injuries for female runners.

Discriminating features of ground reaction forces in overweight old and young adults during walking using functional principal component analysis

BACKGROUND

Limited attention has been paid to age- or body size-related changes in the ground reaction forces (GRF) during walking despite their strong associations with lower limb injuries and pathology.

RESEARCH QUESTION

Do the features of GRF during walking associate with age or body size?

METHODS

Fifty-four participants were subdivided into four groups according to their age and body size: overweight old (n = 12), non-overweight old (n = 13), overweight young (n = 13), and non-overweight young (n = 16). Participants were asked to walk at their self-selected speeds on level ground with force plates embedded in the center of walkway. Functional principal component analysis (FPCA) was performed to extract major modes of variation and functional principal component scores (FPCs) in three-dimensional GRFs. Analysis of variance models were employed to investigate the effect of age, body size, or their interactions on the FPCs of each component of the GRF, with the adjustment to gait speed.

RESULTS

Significant age and body size effects were observed in FPC1 across all three-dimensional GRF. Both overweight and older groups showed greater braking force after heel-strike and greater propulsive forces during pre-swing when compared to the non-overweight and younger groups, respectively. The overweight old group displayed greater medial forces during mid-stance and the overweight young group showed prominently larger medial forces during pre-swing, while non-overweight old showed a tendency of flatter medial-lateral GRF waveforms during the entire stance phase. FPC2 revealed that only body size had an effect on three-dimensional GRF with the highest FPC2 scores in the overweight old group.

SIGNIFICANCE

Three-dimensional GRF during walking could be altered by the body size and age, which were more pronounced in the overweight and older group. The more dynamic GRF pattern with greater and/or lower peaks could be contributing factors to the increased joint load and injury rates observed in overweight aged individuals.

One hundred marathons in 100 days: Unique biomechanical signature and the evolution of force characteristics and bone density

BACKGROUND

An extraordinary long-term running performance may benefit from low dynamic loads and a high load-bearing tolerance. An extraordinary runner (age = 55 years, height = 1.81 m, mass = 92 kg) scheduled a marathon a day for 100 consecutive days. His running biomechanics and bone density were investigated to better understand successful long-term running in the master athlete.

METHODS

Overground running gait analysis and bone densitometry were conducted before the marathon-a-day challenge and near its completion. The case's running biomechanics were compared pre-challenge to 31 runners who were matched by a similar foot strike pattern.

RESULTS

The case's peak vertical loading rate (Δx̄ = -61.9 body weight (BW)/s or -57%), peak vertical ground reaction force (Δx̄ = -0.38 BW or -15%), and peak braking force (Δx̄ = -0.118 BW or -31%) were remarkably lower (p < 0.05) than the control group at ∼3.3 m/s. The relatively low loading-related magnitudes were attributed to a remarkably high duty factor (0.41) at the evaluated speed. The foot strike angle of the marathoner (29.5°) was greater than that of the control group, affecting the peak vertical loading rate. Muscle powers in the lower extremity were also remarkably low in the case vs. controls: peak power of knee absorption (Δx̄ = -9.16 watt/kg or -48%) and ankle generation (Δx̄ = -3.17 watt/kg or -30%). The bone mineral density increased to 1.245 g/cm² (+2.98%) near completion of the challenge, whereas the force characteristics showed no statistically significant change.

CONCLUSION

The remarkable pattern of the high-mileage runner may be useful in developing or evaluating load-shifting strategies in distance running.

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.”

Friction Syndromes of the Knee

The knee is a complex joint with many fascial and ligamentous interactions. The movement in multiple planes makes the knee a prime site for friction syndromes, especially in active individuals. The most common friction syndrome is the iliotibial band friction syndrome. This occurs commonly in runners and cyclists and can be diagnosed clinically in a patient with lateral knee pain during activity. The anterior fat pads of the knee can also be the site of friction syndromes, most often in the Hoffa fat pad. Edema here can be located in the superolateral aspect of the fat pad when associated with patellar abnormalities, or diffusely when impingement is due to other causes. Edema of the quadriceps or prefemoral fat pad may also cause anterior knee pain and may be diagnosed with magnetic resonance imaging. The posteromedial friction syndrome and medial tibial crest syndrome are rare causes of medial knee pain highly active individuals.

Biomechanical and Musculoskeletal Measurements as Risk Factors for Running-Related Injury in Non-elite Runners: A Systematic Review and Meta-analysis of Prospective Studies

BACKGROUND

Running-related injury (RRI) is highly prevalent among recreational runners and is a key barrier to participation. Atypical lower limb alignment and mechanical function have been proposed to play a role in development of lower extremity injury. The purpose of this study was to investigate relationships between incidence of running-related injury (RRI) in non-elite runners with biomechanical and musculoskeletal variables.

METHODS

A systematic review and meta-analysis of prospective studies. Published research indexed in MEDLINE, EMBASE, CINAHL, SPORTDiscus, AMED, and The Cochrane library until 13th January 2021, grey literature, and reference lists of included studies were screened to identify prospective studies of non-elite adult runners that measured a relationship between biomechanical or musculoskeletal measures and incidence of RRI.

RESULTS

Thirty studies (3404 runners), testing over 100 discrete biomechanical and musculoskeletal risk factors for RRI, were included. Nineteen studies were pooled in twenty-five separate meta-analyses. Meta-analysis of four studies detected significantly less knee extension strength among runners who developed a RRI (SMD - 0.19, 95% CI - 0.36 to - 0.02, p = 0.03), though this may not be clinically important. A meta-analysis of two studies detected significantly lower hip adduction velocity among runners who developed a RRI (MD - 12.80, 95% CI - 25.22 to - 0.38, p = 0.04). Remaining meta-analyses found no significant relationship between biomechanical or musculoskeletal variables and RRI.

CONCLUSION

This systematic review and meta-analysis found the currently available literature does not generally support biomechanical or musculoskeletal measures as risk factors for RRI in non-elite runners. While meta-analysis findings for knee extension strength and hip adduction velocity as risk factors for RRI were statistically significant, the associated trivial to small effects sizes suggest these findings should be treated with caution. Until further evidence emerges, recommendations for injury prevention in non-elite runners cannot be made based on biomechanical and musculoskeletal measurements alone.

Differences in Peak Impact Accelerations Among Foot Strike Patterns in Recreational Runners

Introduction

Running-related injuries (RRIs) occur from a combination of training load errors and aberrant biomechanics. Impact loading, measured by peak acceleration, is an important measure of running biomechanics that is related to RRI. Foot strike patterns may moderate the magnitude of impact load in runners. The effect of foot strike pattern on peak acceleration has been measured using tibia-mounted inertial measurement units (IMUs), but not commercially available insole-embedded IMUs. The aim of this study was to compare the peak acceleration signal associated with rearfoot (RFS), midfoot (MFS), and forefoot (FFS) strike patterns when measured with an insole-embedded IMU.

Materials and Methods

Healthy runners ran on a treadmill for 1 min at three different speeds with their habitual foot strike pattern. An insole-embedded IMU was placed inside standardized neutral cushioned shoes to measure the peak resultant, vertical, and anteroposterior accelerations at impact. The Foot strike pattern was determined by two experienced observers and evaluated using high-speed video. Linear effect mixed-effect models were used to quantify the relationship between foot strike pattern and peak resultant, vertical, and anteroposterior acceleration.

Results

A total of 81% of the 187 participants exhibited an RFS pattern. An RFS pattern was associated with a higher peak resultant (0.29 SDs; p = 0.029) and vertical (1.19 SD; p < 0.001) acceleration when compared with an FFS running pattern, when controlling for speed and limb, respectively. However, an MFS was associated with the highest peak accelerations in the resultant direction (0.91 SD vs. FFS; p = 0.002 and 0.17 SD vs. RFS; p = 0.091). An FFS pattern was associated with the lowest peak accelerations in both the resultant and vertical directions. An RFS was also associated with a significantly greater peak acceleration in the anteroposterior direction (0.28 SD; p = 0.033) than an FFS pattern, while there was no difference between MFS and FFS patterns.

Conclusion

Our findings indicate that runners should be grouped by RFS, MFS, and FFS when comparing peak acceleration, rather than the common practice of grouping MFS and FFS together as non-RFS runners. Future studies should aim to determine the risk of RRI associated with peak accelerations from an insole-embedded IMU to understand whether the small observed differences in this study are clinically meaningful.

Spatiotemporal and Ground-Reaction Force Characteristics as Risk Factors for Running-Related Injury: A Secondary Analysis of a Randomized Trial Including 800+ Recreational Runners

BACKGROUND

Running biomechanics may play a role in running-related injury development, but to date, only a few modifiable factors have been prospectively associated with injury risk.

PURPOSE

To identify risk factors among spatiotemporal and ground-reaction force characteristics in recreational runners and to investigate whether shoe cushioning modifies the association between running biomechanics and injury risk.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Recreational runners (N = 848) were tested on an instrumented treadmill at their preferred running speed in randomly allocated, standardized running shoes (with either hard or soft cushioning). Typical kinetic and spatiotemporal metrics were derived from ground-reaction force recordings. Participants were subsequently followed up for 6 months regarding running activity and injury. Cox regression models for competing risk were used to investigate the association between biomechanical risk factors and injury risk, including stratified analyses by shoe version.

RESULTS

In the crude analysis, greater injury risk was found for greater step length (subhazard rate ratio [SHR], 1.01; 95% CI, 1.00-1.02; P = .038), longer flight time (SHR, 1.00; 95% CI, 1.00-1.01; P = .028), shorter contact time (SHR, 0.99; 95% CI, 0.99-1.00; P = .030), and lower duty factor (defined as the ratio between contact time and stride time; SHR, 0.95; 95% CI, 0.91-0.98; P = .005). In the stratified analyses by shoe version, adjusted for previous injury and running speed, lower duty factor was associated with greater injury risk in those using the soft shoes (SHR, 0.92; 95% CI, 0.85-0.99; P = .042) but not in those using the hard shoes (SHR, 0.97; 95% CI, 0.91-1.04; P = .348).

CONCLUSION

Lower duty factor is an injury risk factor, especially for softer shoe use. Contrary to widespread beliefs, vertical impact peak, loading rate, and step rate were not injury risk factors in recreational runners.

REGISTRATION

NCT03115437 (ClinicalTrials.gov identifier).

Comparisons of Gait Variability and Symmetry in Healthy Runners, Runners with a History of Lower Limb Injuries, and Runners with a Current Lower Limb Injury

Background: Running is a cyclic movement requiring bilateral symmetry between the lower limbs to reduce injury risk. The assessment of side-to-side differences is often performed to detect functional deficits. Objectives: The purpose was to study side-to-side differences using clinical and running performance assessments in healthy runners (HR), runners with a history of lower limb injuries (RHI), and runners with a current lower limb injury (RLI). Methods: Forty-three runners were recruited, with 14 participants being allocated to the HR group, 13 to the RHI group, and 16 to the RLI group. Peak vertical ground reaction force (GRF), midfoot pressure, foot rotation, and gait variability were recorded using a Zebris FDM-T treadmill analysis system. Participants were also assessed using the navicular drop test. Dependent t-tests were used to determine if any differences existed between the lower limbs within each group. One-way ANOVAs were then used to investigate the side-to-side differences between the three groups. Results: Significant differences were seen in navicular drop height between lower limbs within both the HR (P = 0.02) and RHI (P = 0.009) groups, and side-to-side differences in foot rotation were greatest in the RLI group (~34%) compared to both the RHI (~30.5%) and HR (~24%) groups. The lateral variability of the center of pressure was greatest in the RLI group (37.1 mm) compared to the RHI (28.9 mm) and HR (22.2 mm) groups. Conclusions: Variability of butterfly center of pressure diagram may help identify runners at a greater risk of lower limb injury. Side-to-side differences should be expected to progressively decrease from the injured stage, through the recovery and return to sport phases. Target goals of less than 34% side-to-side difference for foot rotation and 37.1 mm for the lateral center of pressure variability may be used to help the decision-making process when considering a return to running practice.

The Use of a Single Trunk-Mounted Accelerometer to Detect Changes in Center of Mass Motion Linked to Lower-Leg Overuse Injuries: A Prospective Study

Movement dynamics during running was previously characterized using a trunk-mounted accelerometer, and were associated with a history of overuse injuries. However, it remains unknown if these measures are also linked to the development of overuse injuries. The aim of this study was therefore to determine how movement dynamics alter in response to fatigue, and the possible link with developing lower-leg overuse injuries during a six-month follow-up period. Two hundred and eight movement science university students completed a 12-min all-out run while wearing a trunk-mounted accelerometer. Dynamic stability, dynamic loading and spatiotemporal measures were extracted from the accelerometer. Participants sustaining an injury within the 6-month period demonstrated significantly higher RMS ratio values in the vertical direction and lower RMS ratio values in the anteroposterior direction, and lower impact acceleration values in the anteroposterior direction in an unfatigued state compared to the uninjured group. They also demonstrated an increase in dynamic loading in the horizontal plane during the run. In addition, with running fatigue both groups exhibited changes in dynamic stability and loading measures. These results show the potential of using a single trunk-mounted accelerometer to detect changes in movement dynamics that are linked to lower-leg overuse injuries.

Recommendations for marathon runners: on the application of recommender systems and machine learning to support recreational marathon runners

Every year millions of people, from all walks of life, spend months training to run a traditional marathon. For some it is about becoming fit enough to complete the gruelling 26.2 mile (42.2 km) distance. For others, it is about improving their fitness, to achieve a new personal-best finish-time. In this paper, we argue that the complexities of training for a marathon, combined with the availability of real-time activity data, provide a unique and worthwhile opportunity for machine learning and for recommender systems techniques to support runners as they train, race, and recover. We present a number of case studies-a mix of original research plus some recent results-to highlight what can be achieved using the type of activity data that is routinely collected by the current generation of mobile fitness apps, smart watches, and wearable sensors.

The effects of incremental changes in rucksack load on lower extremity joint Kinetic patterns during ruck marching

Injuries are often attributed to ruck marching. Therefore, it is important to examine how load carriage influences gait mechanics. The purpose of this study was to examine how subtle changes in rucksack load influence joint torque patterns during marching. Fourteen Army ROTC cadets marched with light, moderate, and heavy rucksack loads. Kinetic and kinematic data were recorded via an instrumented treadmill and motion capture system and principal component analysis was used to analyse the joint torque waveforms. Cadets exhibited moderate-large increases in knee extension torques during early stance (effect sizes ≥0.45) and small-moderate increases in ankle plantarflexion torques during push off (effect sizes ≥0.23) with each incremental increase in rucksack load. The lighter load also resulted in lower hip extension torques during early stance and flexion torques during late stance, vs. the moderate and heavier loads (effect sizes ≥0.23). It appears that subtle changes in rucksack load influence marching mechanics. Practitioner Summary: The purpose of this study was to examine how relatively subtle changes in rucksack load influence marching mechanics. Army ROTC cadets marched with relatively light, moderate, and heavy rucksack loads. Our results indicate that even subtle changes in rucksack load influence joint torque patterns of the hip, knee, and ankle. Abbreviations: ROTC: reserve officer training corps; RoF: rating-of-fatigue; PC: principal component; ICC: intraclass correlation coefficient; ES: effect size.

Lower step rate is associated with a higher risk of bone stress injury: a prospective study of collegiate cross country runners

OBJECTIVES

To determine if running biomechanics and bone mineral density (BMD) were independently associated with bone stress injury (BSI) in a cohort of National Collegiate Athletic Association Division I cross country runners.

METHODS

This was a prospective, observational study of 54 healthy collegiate cross country runners over three consecutive seasons. Whole body kinematics, ground reaction forces (GRFs) and BMD measures were collected during the preseason over 3 years via motion capture on an instrumented treadmill and total body densitometer scans. All medically diagnosed BSIs up to 12 months following preseason data collection were recorded. Generalised estimating equations were used to identify independent risk factors of BSI.

RESULTS

Univariably, step rate, centre of mass vertical excursion, peak vertical GRF and vertical GRF impulse were associated with BSI incidence. After adjusting for history of BSI and sex in a multivariable model, a higher step rate was independently associated with a decreased risk of BSI. BSI risk decreased by 5% (relative risk (RR): 0.95; 95% CI 0.91 to 0.98) with each one step/min increase in step rate. BMD z-score was not a statistically significant risk predictor in the final multivariable model (RR: 0.93, 95% CI 0.85 to 1.03). No other biomechanical variables were found to be associated with BSI risk.

CONCLUSION

Low step rate is an important risk factor for BSI among collegiate cross country runners and should be considered when developing comprehensive programmes to mitigate BSI risk in distance runners.

The Effect of Footwear, Running Speed, and Location on the Validity of Two Commercially Available Inertial Measurement Units During Running

Introduction: Most running-related injuries are believed to be caused by abrupt changes in training load, compounded by biomechanical movement patterns. Wearable technology has made it possible for runners to quantify biomechanical loads (e.g., peak positive acceleration; PPA) using commercially available inertial measurement units (IMUs). However, few devices have established criterion validity. The aim of this study was to assess the validity of two commercially available IMUs during running. Secondary aims were to determine the effect of footwear, running speed, and IMU location on PPA.

Materials and Methods: Healthy runners underwent a biomechanical running analysis on an instrumented treadmill. Participants ran at their preferred speed in three footwear conditions (neutral, minimalist, and maximalist), and at three speeds (preferred, +10%, −10%) in the neutral running shoes. Four IMUs were affixed at the distal tibia (IMeasureU-Tibia), shoelaces (RunScribe and IMeasureU-Shoe), and insole (Plantiga) of the right shoe. Pearson correlations were calculated for average vertical loading rate (AVLR) and PPA at each IMU location.

Results: The AVLR had a high positive association with PPA (IMeasureU-Tibia) in the neutral and maximalist (r = 0.70–0.72; p ≤ 0.001) shoes and in all running speed conditions (r = 0.71–0.83; p ≤ 0.001), but low positive association in the minimalist (r = 0.47; p < 0.05) footwear condition. Conversely, the relationship between AVLR and PPA (Plantiga) was high in the minimalist (r = 0.75; p ≤ 0.001) condition and moderate in the neutral (r = 0.50; p < 0.05) and maximalist (r = 0.57; p < 0.01) footwear. The RunScribe metrics demonstrated low to moderate positive associations (r = 0.40–0.62; p < 0.05) with AVLR across most footwear and speed conditions.

Discussion: Our findings indicate that the commercially available Plantiga IMU is comparable to a tibia-mounted IMU when acting as a surrogate for AVLR. However, these results vary between different levels of footwear and running speeds. The shoe-mounted RunScribe IMU exhibited slightly lower positive associations with AVLR. In general, the relationship with AVLR improved for the RunScribe sensor at slower speeds and improved for the Plantiga and tibia-mounted IMeasureU sensors at faster speeds.

Relationship between duty factor and external forces in slow recreational runners

Objectives

Recreational runners show a large interindividual variation in spatiotemporal characteristics. This research focused on slow runners and intended: (1) to document the variance in duty factor (DF) between runners in a real-life running setting and (2) examine whether the interindividual variation in DF and stride frequency (SF) relates to differences in external loading parameters between runners.

Methods

Spatiotemporal characteristics of 23 slow runners (ie, <2.6 m/s) were determined during a 5.2 km running event. To relate the interindividual variation in DF and SF to differences in external forces between runners (maximal vertical ground reaction force (FzMax), peak braking force (PBF) and vertical instantaneous loading rate (VILR)), 14 of them were invited to the lab. They ran at 1.9 m/s on a treadmill while ground reaction forces were recorded. A multiple linear regression analysis was conducted to investigate the effect of DF and SF on external force measures.

Results

DF between slow runners varied from 42.50% to 56.49% in a recreational running event. DF was found to be a significant predictor of FzMax (R²=0.755) and PBF (R²=0.430). SF only improved the model for PBF, but to a smaller extent than DF (R² change=0.191). For VILR, neither DF nor SF were significant predictors.

Conclusion

External forces are lower in recreational runners that run with higher DFs and slightly lower SFs. These findings may be important for injury prevention purposes, especially directed to recreational runners that are more prone to overuse injuries.

Music-based biofeedback to reduce tibial shock in over-ground running: a proof-of-concept study

Methods to reduce impact in distance runners have been proposed based on real-time auditory feedback of tibial acceleration. These methods were developed using treadmill running. In this study, we extend these methods to a more natural environment with a proof-of-concept. We selected ten runners with high tibial shock. They used a music-based biofeedback system with headphones in a running session on an athletic track. The feedback consisted of music superimposed with noise coupled to tibial shock. The music was automatically synchronized to the running cadence. The level of noise could be reduced by reducing the momentary level of tibial shock, thereby providing a more pleasant listening experience. The running speed was controlled between the condition without biofeedback and the condition of biofeedback. The results show that tibial shock decreased by 27% or 2.96 g without guided instructions on gait modification in the biofeedback condition. The reduction in tibial shock did not result in a clear increase in the running cadence. The results indicate that a wearable biofeedback system aids in shock reduction during over-ground running. This paves the way to evaluate and retrain runners in over-ground running programs that target running with less impact through instantaneous auditory feedback on tibial shock.

Relationships between tibial acceleration and ground reaction force measures in the medial-lateral and anterior-posterior planes

Peak vertical tibial accelerations during running have shown strong correlations with vertical ground reaction force loading rates and some associations with injury. However, little attention has been given to tibial accelerations along the medial-lateral and anterior-posterior axes. Therefore, our purpose was to examine the correlation between peak tibial accelerations and ground reaction force loading rates in the medial-lateral and posterior directions. Eighteen recreational runners were recruited who ran with a rearfoot strike pattern (10 men/ 8 women, mean age (yrs) = 33 ± 11). Tibial accelerations and ground reaction forces were collected while participants ran on an instrumented treadmill at a self-selected speed. Correlations were developed for: a) peak medial and lateral accelerations with lateral and medial loading rates, respectively, b) peak anterior tibial accelerations and posterior loading rates. Significant correlations were found between tibial accelerations and loading rates in all planes. Peak medial tibial accelerations were correlated with lateral loading rates (R_s = 0.86, p < 0.001) and peak lateral tibial accelerations were correlated with peak medial loading rates (R_s = 0.91, p < 0.001). A lower correlation was found between anterior accelerations and posterior loading rates (R_s = 0.51, p = 0.030). Tibial accelerations in the medial-lateral plane seem to be a valid surrogate for the respective ground reaction force measures during running on a treadmill, explaining 74-83% of the variance in loading rates. However, with only 26% of the variance explained, the same may not be true for anterior tibial accelerations and posterior loading rates.

Risk factors for overuse injuries in short- and long-distance running: A systematic review

PURPOSE

The aim of this study was to review information about risk factors for lower extremity running injuries in both short-distance (mean running distance ≤20 km/week and ≤10 km/session) and long-distance runners (mean running distance >20 km/week and >10 km/session).

METHODS

Electronic databases were searched for articles published up to February 2019. Prospective cohort studies using multivariable analysis for the assessment of individual risk factors or risk models for the occurrence of lower extremity running injuries were included. Two reviewers independently selected studies for eligibility and assessed risk of bias with the Quality in Prognostic Studies Tool. The GRADE approach was used to assess the quality of the evidence.

RESULTS

A total of 29 studies were included: 17 studies focused on short-distance runners, 11 studies focused on long-distance runners, and 1 study focused on both types of runners. A previous running-related injury was the strongest risk factor for an injury for long-distance runners, with moderate-quality evidence. Previous injuries not attributed to running was the strongest risk factor for an injury for short-distance runners, with high-quality evidence. Higher body mass index, higher age, sex (male), having no previous running experience, and lower running volume were strong risk factors, with moderate quality evidence, for short-distance runners. Low-quality evidence was found for all risk models as predictors of running-related injuries among short- and long-distance runners.

CONCLUSION

Several risk factors for lower extremity injuries have been identified among short- and long-distance runners, but the quality of evidence for these risk factors for running-related injuries is limited. Running injuries seem to have a multifactorial origin both in short- and long-distance runners.

Gait Retraining Improves Running Impact Loading and Function in Previously Injured U.S. Military Cadets: A Pilot Study

INTRODUCTION

Running-related musculoskeletal injury (RRI) among U.S. military service members continues to negatively impact force readiness. There is a paucity of evidence supporting the use of RRI interventions, such as gait retraining, in military populations. Gait retraining has demonstrated effectiveness in altering running biomechanics and reducing running load. The purpose of this pilot study was to investigate the clinical effect of a gait retraining intervention on a military cadet population recovering from a lower-extremity RRI.

MATERIALS AND METHODS

The study design is a pilot study. Before study initiation, institutional approval was granted by the Keller Army Community Hospital Office of Human Research Protections. Nine rearfoot strike (RFS) runners recovering from a lower-extremity RRI at the U.S. Military Academy were prospectively enrolled and completed a gait retraining intervention. Participants followed-up with their assigned medical provider 6 times over 10 weeks for a clinical evaluation and running gait retraining. Gait retraining was provided utilizing verbal, visual, and audio feedback to facilitate a change in running foot strike pattern from RFS to non-rearfoot strike (NRFS) and increase preferred running step rate. At pre-intervention and post-intervention running ground reaction forces (GRF) [average vertical loading rate (AVLR), peak vertical GRF], kinematic (foot strike pattern) and temporospatial (step rate, contact time) data were collected. Participants self-reported their level of function via the Single Assessment Numeric Evaluation, Patient-Specific Functional Scale, and total weekly running minutes. Paired samples t-tests and Wilcoxon signed rank tests were used to compare pre- and post-intervention measures of interest. Values of P < .05 were considered statistically significant.

RESULTS

Nine patients completed the 10-week intervention (age, 20.3 ± 2.2 years; height, 170.7 ± 13.8 cm; mass, 71.7 ± 14.9 kg; duration of injury symptoms, 192.4 ± 345.5 days; running speed, 2.8 ± 0.38 m/s). All nine runners (100%) transitioned from RFS to NRFS. Left AVLR significantly decreased from 60.3 ± 17.0 bodyweight per second (BW/s) before intervention to 25.9 ± 9.1 BW/s after intervention (P = 0.008; effect size (d) = 2.5). Right AVLR significantly decreased from 60.5 ± 15.7 BW/s to 32.3 ± 12.5 BW/s (P < .001; d = 2.0). Similarly, step rate increased from 169.9 ± 10.0 steps per minute (steps/min) before intervention to 180.5 ± 6.5 steps/min following intervention (P = .005; d = 1.3). Single Assessment Numeric Evaluation scores improved significantly from 75 ± 23 to 100 ± 8 (P = .008; d = 1.5) and Patient-Specific Functional Scale values significantly improved from 6 ± 2.3 to 9.5 ± 1.6 (P = .007; d = 1.8) after intervention. Peak vertical GRF (left, P = .127, d = 0.42; right, P = .052, d = 0.53), contact time (left, P = 0.127, d = 0.42; right, P = 0.052, d = 0.53), and total weekly continuous running minutes (P = 0.095, d = 0.80) remained unchanged at post-intervention. All 9 patients remained injury free upon a 6-month medical record review.

CONCLUSIONS

In 9 military service members with a RRI, a 10-week NRFS gait retraining intervention was effective in improving running mechanics and measures of function. Patients remained injury-free 6 months following enrollment. The outcomes of this pilot study suggest that individuals recovering from certain lower-extremity RRIs may benefit from transitioning to an NRFS running pattern.

Estimation of Three-Dimensional Lower Limb Kinetics Data during Walking Using Machine Learning from a Single IMU Attached to the Sacrum

Kinetics data such as ground reaction forces (GRFs) are commonly used as indicators for rehabilitation and sports performance; however, they are difficult to measure with convenient wearable devices. Therefore, researchers have attempted to estimate accurately unmeasured kinetics data with artificial neural networks (ANNs). Because the inputs to an ANN affect its performance, they must be carefully selected. The GRF and center of pressure (CoP) have a mechanical relationship with the center of mass (CoM) in the three dimensions (3D). This biomechanical characteristic can be used to establish an appropriate input and structure of an ANN. In this study, an ANN for estimating gait kinetics with a single inertial measurement unit (IMU) was designed; the kinematics of the IMU placed on the sacrum as a proxy for the CoM kinematics were applied based on the 3D spring mechanics. The walking data from 17 participants walking at various speeds were used to train and validate the ANN. The estimated 3D GRF, CoP trajectory, and joint torques of the lower limbs were reasonably accurate, with normalized root-mean-square errors (NRMSEs) of 6.7% to 15.6%, 8.2% to 20.0%, and 11.4% to 24.1%, respectively. This result implies that the biomechanical characteristics can be used to estimate the complete three-dimensional gait data with an ANN model and a single IMU.