Per-step and cumulative load at three common running injury locations: The effect of speed, surface gradient, and cadence.

Understanding how loading and damage on common running injury locations changes across speeds, surface gradients, and step frequencies may inform training programs and help guide progression/rehabilitation after injuries. However, research investigating tissue loading and damage in running is limited and fragmented across different studies, thereby impairing comparison between conditions and injury locations. This study examined per-step peak load and impulse, cumulative impulse, and cumulative weighted impulse (hereafter referred to as cumulative damage) on three common injury locations (patellofemoral joint, tibia, and Achilles tendon) across different speeds, surface gradients, and cadences. We also explored how cumulative damage in the different tissues changed across conditions relative to each other. Nineteen runners ran at five speeds (2.78, 3.0, 3.33, 4.0, 5.0 m s-1 ), and four gradients (-6, -3, +3, +6°), and three cadences (preferred, ±10 steps min-1 ) each at one speed. Patellofemoral, tibial, and Achilles tendon loading and damage were estimated from kinematic and kinetic data and compared between conditions using a linear mixed model. Increases in running speed increased patellofemoral cumulative damage, with nonsignificant increases for the tibia and Achilles tendon. Increases in cadence reduced damage to all tissues. Uphill running increased tibial and Achilles tendon, but decreased patellofemoral damage, while downhill running showed the reverse pattern. Per-step and cumulative loading, and cumulative loading and cumulative damage indices diverged across conditions. Moreover, changes in running speed, surface gradient, and step frequency lead to disproportional changes in relative cumulative damage on different structures. Methodological and practical implications for researchers and practitioners are discussed.

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

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

Hip and core exercise programme prevents running-related overuse injuries in adult novice recreational runners: a three-arm randomised controlled trial (Run RCT).

OBJECTIVE: This study aims to investigate the efficacy of two exercise interventions in reducing lower extremity (LE) injuries in novice recreational runners. METHODS: Novice runners (245 female, 80 male) were randomised into hip and core (n=108), ankle and foot (n=111) or control (n=106) groups. Interventions were completed before running and included exercise programmes focusing on either (1) hip and core or (2) ankle and foot muscles. The control group performed static stretching exercises. All groups were supervised by a physiotherapist and performed the same running programme. Injuries and running exposure were registered using weekly questionnaires during the 24-week study. Primary outcome was running-related LE injury. RESULTS: The incidence of LE injuries was lower in the hip and core group compared with the control group (HR 0.66; 95% CI 0.45 to 0.97). The average weekly prevalence of overuse injuries was 39% lower (prevalence rate ratio, PRR 0.61, 95% CI 0.39 to 0.96), and the prevalence of substantial overuse injuries was 52% lower (PRR 0.48, 95% CI 0.27 to 0.90) in the hip and core group compared with the control group. No significant difference was observed between the ankle and foot group and control group in the prevalence of overuse injuries. A higher incidence of acute injuries was observed in the ankle and foot group compared with the control group (HR 3.60, 95% CI 1.20 to 10.86). CONCLUSION: A physiotherapist-guided hip and core-focused exercise programme was effective in preventing LE injuries in novice recreational runners. The ankle and foot programme did not reduce LE injuries and did not protect against acute LE injuries when compared with static stretching.

Injury incidence and prevalence in elite short-course triathletes: a 4-year prospective study.

OBJECTIVE: To characterise the prevalence, incidence rate (IR) and burden of injuries in elite short-course triathletes over a 4-year training and competition period. METHODS: Fifty elite Australian triathletes were prospectively monitored for injury during four consecutive seasons (2018-2021). Injuries requiring medical attention were prospectively recorded and further subcategorised according to time loss. The IR and burden (injury IR×mean injury severity) were calculated per 365 athlete days, with sex differences in IR compared using IR ratios (IRR) from negative binomial regression models. RESULTS: Two hundred and sixty-six injuries were reported in 46 (92.0%) athletes, of which 67.3% resulted in time loss. The injury IR was 1.87 injuries per 365 athlete days (95% CI 1.70 to 2.80), and comparable between sexes (IRR 0.82, 95% CI 0.64 to 1.04, p=0.109). Most injuries (70.7%) were training related. The most frequently injured body sites were the ankle (15.8%), foot (12.4%) and lower leg (12.0%). Bone stress injuries (BSIs) were the most burdensome injury type with 31.38 days of time loss per 365 days (95% CI 24.42 to 38.34). Twenty athletes (40.0%) reported at least one bone stress injury (BSI) (range 0-3). The rate of BSIs in female athletes was three times greater compared with male athletes (IRR 2.99, 95% CI 1.26 to 7.07, p=0.013). CONCLUSION: Two-thirds of injuries reported in elite short-course triathletes resulted in time loss, with the majority occurring during training activities. Foot, ankle and other lower leg injuries had the highest incidence, with BSIs carrying the highest injury burden. The considerably higher rate of BSI observed in female athletes warrants consideration for future prevention strategies in female triathletes.

Congenital Generalized Lipodystrophy in a Division 1 Female Sprinter.

ABSTRACT: A 21-year-old African American Division 1 female sprinter presented with 3-weeks history of right great toe and forefoot pain, fatigue, and a 30-day continuous menstrual cycle despite implanted etonogestrel (Nexplanon) inserted 3 years prior. An magnetic resonance imagine (MRI) identified likely stress fracture of the second metatarsal base with a diffusely low T1 signal indicating hyperactive red marrow. Due to persistent pain, a follow-up MRI was ordered 6 months later and indicated serous atrophy of the bone marrow, prompting a further metabolic workup notable for triglycerides exceeding 4000 mg/dL and a hemoglobin A1c of 10.9%. This case highlights the manifestation of a rare congenital lipodystrophy that initially presented as a relatively classic stress fracture and metrorrhagia in a female athlete.

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.

Hamstrings on focus: Are 72 hours sufficient for recovery after a football (soccer) match? A multidisciplinary approach based on hamstring injury risk factors and histology.

This study aimed to assess acute and residual changes in sprint-related hamstring injury (HSI) risk factors after a football (soccer) match, focusing on recovery within the commonly observed 72-h timeframe between elite football matches. We used a multifactorial approach within a football context, incorporating optical and ultrastructural microscopic analysis of BFlh (biceps femoris long head) muscle fibres, along with an examination of BFlh fibre composition. Changes in sprint performance-related factors and HSI modifiable risk factors were examined until 3 days after the match (MD +3) in 20 football players. BFlh biopsy specimens were obtained before and at MD +3 in 10 players. The findings indicated that at MD +3, sprint-related performance and HSI risk factors had not fully recovered, with notable increases in localized BFlh fibre disruptions. Interestingly, match load (both external and internal) did not correlate with changes in sprint performance or HSI risk factors nor with BFlh fibre disruption. Furthermore, our study revealed a balanced distribution of ATPase-based fibre types in BFlh, with type-II fibres associated with sprint performance. Overall, the results suggest that a 72-h recovery period may not be adequate for hamstring muscles in terms of both HSI risk factors and BFlh fibre structure following a football match.

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.

Effectiveness of an 18-week general strength and foam-rolling intervention on running-related injuries in recreational runners.

RATIONALE: More research is needed to uncover the effectiveness of combined strength and foam-rolling interventions to prevent running-related injuries. OBJECTIVES: To evaluate effectiveness of an 18-week general strength and foam-rolling intervention on the incidence of running-related injuries. METHOD: This is an 18-week observational comparative study. A total of 433 recreational runners participated (n = 203 female). The intervention group (n = 228) performed general strength and foam-rolling exercises twice weekly for 18 weeks, the control group (n = 205) maintained their regular training habits. Running volume and running-related pain were reported weekly. Secondary analyses were performed on the subgroups of the intervention group based on compliance; low compliance (n = 100), intermediate compliance (n = 63), and high compliance (n = 65). Cumulative incidence proportions were calculated and time-to-event statistics were performed to compare survival times between groups. Univariate cox proportional hazards ratio was calculated to estimate the risk of running-related injuries at 18 weeks. RESULTS: A total of 100 running-related injuries were sustained. The cumulative incidence proportion for the control and intervention groups was 27.1% (95% CI: 21.4-33.9) and 23.0% (95% CI: 17.8-29.4), respectively. No statistically significant difference was found between the overall intervention group and control group (log-rank p = 0.31). A significant difference existed between the high-compliance subgroup and the control group (log-rank p = 0.00). Highly compliant runners were 85% less likely (hazard rate ratio = 0.15; 95% CI: 0.05-0.46) to sustain an injury during the study compared with controls. CONCLUSION: Recreational runners highly compliant with the intervention were 85% less likely and took on average 57 days longer to sustain a running-related injury when compared with controls, with a cumulative incidence proportion of 4.6% after 18 weeks.

Outpatient Runners Clinic Visit Trends and Injury Characteristics Among 392 Child and Adolescent Patients: A 10-year Chart Review.

OBJECTIVE: To evaluate clinic visits and running-related injury (RRI) characteristics among child and adolescent runners seeking care at an outpatient clinic over a 10-year time frame. DESIGN: Retrospective chart review. SETTING: Outpatient hospital-affiliated Injured Runners Clinic. PATIENTS: Children and adolescent runners (6-17 years) with RRIs. INDEPENDENT VARIABLES: We examined electronic medical records (EMRs) among child and adolescent patients in the hospital database from 2011 to 2021 to obtain RRI characteristics and key demographic factors. MAIN OUTCOME MEASURES: We assessed volume and frequency of patient visits to the clinic by RRI characteristics. Chi square analyses were used to compare the proportion of clinic visits over time and injury trends by body region and diagnosis. RESULTS: There were 392 patients (sex: 277 F; mean age: 16.1 ± 1.3 years) and an average of 5 clinic visits per diagnosis (5 ± 4 visits; min: 1 visit, max: 31 visits). Number of visits generally increased over time up to 2016 but declined most drastically during the years of the pandemic (2020-2021; χ 2 = 644, P < 0 .001). Of the 654 new injury diagnoses, 77.68% were attributed to repetitive stress. Bone stress injuries to the tibia were the most common RRI (χ 2 = 1940, P < 0 .001; N = 132; 20.2% of all injuries) and constituted most of the clinic visits (χ 2 = 9271, P < 0 .001; N = 591; 25.4% of all visits). CONCLUSION: We identified that adolescents with overuse injuries, particularly bone stress injuries to the tibia, constituted most of the visits to the outpatient healthcare setting. Clinicians should emphasize injury prevention efforts in clinical practice to reduce RRI burden.

Achilles tendon structure is associated with regular running volume and biomechanics.

Achilles tendinopathy was reported to have the highest incidence proportion of all running-related injuries. The purpose of this study was to analyse the association between the Achilles tendon structure and running activity status. 350 healthy participants (runners and inactive controls, 30-50 years) participated in this research. Each participant completed questionnaires: socioeconomic, psychological, physical activity habits, running status and history and VISA-A. Magnetic resonance imaging, anthropological, running biomechanics and 14 days of physical activity monitoring assessments were performed. There was a higher odd of being in the upper quartile of the Achilles tendon T2* relaxation time with higher maximal knee extension moment independent of age and sex. Compared with runners who ran 21-40 km per week, non-runners and those who ran more than 40 km per week had increased odds of having longest the Achilles tendon T2* relaxation time. Regular running of 21 to 40 km per week is related to the Achilles tendon T2* relaxation time indicating possibly better water content and collagen orientation in these runners with compare to inactive non-runners or highly active individuals. In addition, Achilles tendon T2* relaxation time as indirect indicator of the Achilles tendon structure was positively related to the maximal knee extension moment during running.

Predicting Tissue Loads in Running from Inertial Measurement Units.

BACKGROUND: Runners have high incidence of repetitive load injuries, and habitual runners often use smartwatches with embedded IMU sensors to track their performance and training. If accelerometer information from such IMUs can provide information about individual tissue loads, then running watches may be used to prevent injuries. METHODS: We investigate a combined physics-based simulation and data-based method. A total of 285 running trials from 76 real runners are subjected to physics-based simulation to recover forces in the Achilles tendon and patella ligament, and the collected data are used to train and test a data-based model using elastic net and gradient boosting methods. RESULTS: Correlations of up to 0.95 and 0.71 for the patella ligament and Achilles tendon forces, respectively, are obtained, but no single best predictive algorithm can be identified. CONCLUSIONS: Prediction of tissues loads based on body-mounted IMUs appears promising but requires further investigation before deployment as a general option for users of running watches to reduce running-related injuries.

Running-Related Achilles Tendon Injury: A Prospective Biomechanical Study in Recreational Runners.

There are relatively few running studies that have attempted to prospectively identify biomechanical risk factors associated with Achilles tendon (AT) injuries. Therefore, the aim was to prospectively determine potential running biomechanical risk factors associated with the development of AT injuries in recreational, healthy runners. At study entry, 108 participants completed a set of questionnaires. They underwent an analysis of their running biomechanics at self-selected running speed. The incidence of AT running-related injuries (RRI) was assessed after 1-year using a weekly questionnaire standardized for RRI. Potential biomechanical risk factors for the development of AT RRI injury were identified using multivariable logistic regression. Of the 103 participants, 25% of the sample (15 males and 11 females) reported an AT RRI on the right lower limb during the 1-year evaluation period. A more flexed knee at initial contact (odds ratio = 1.146, P = .034) and at the midstance phase (odds ratio = 1.143, P = .037) were significant predictors for developing AT RRI. The results suggested that a 1-degree increase in knee flexion at initial contact and midstance was associated with a 15% increase in the risk of an AT RRI, thus causing a limitation of training or a stoppage of running in runners.

Efficacy of an Audio-Based Biofeedback Intervention to Modify Running Gait in Female Runners.

CONTEXT: A variety of gait retraining interventions are available to modify running mechanics associated with musculoskeletal injuries. These often require specialized equipment and/or personnel to prompt the runner toward specific strategies. OBJECTIVE: To determine whether instructing female recreational runners to "run quietly" could decrease impact force characteristics. DESIGN: Cohort. SETTING: Research laboratory. PARTICIPANTS: Fifteen healthy female recreational runners (24 [7] y) volunteered. INTERVENTIONS: Baseline testing occurred on day 1 (baseline), a posttraining assessment occurred on day 2 (training), and a final assessment occurred 1 week after training on day 3 (follow-up). A smartphone decibel measuring app was used to provide biofeedback on the decibel level of foot strike on day 2 (training). MAIN OUTCOMES: Peak vertical force, impact transient, peak and average vertical loading rate, ground contact time, and running economy were collected on each day and compared via repeated-measures analyses of variance. RESULTS: Vertical ground reaction force was lower at follow-up (2.30 bodyweights [BW]) versus baseline (2.39 BW, P = .023) and training (2.34 BW, P = .047). Maximal loading rate decreased from baseline (69.70 BW·s-1) to training (62.24 BW·s-1, P = .021) and follow-up (60.35 BW·s-1, P = .031). There was no change in running economy. CONCLUSIONS: Our findings demonstrate that simple instructions to "run quietly" can yield immediate and sustained reductions in impact force profiles, which do not influence running economy.

Instructions Promoting an External Focus Are More Effective for Altering Impact Forces in Female Runners.

CONTEXT: Previous studies have found that instructions promoting an external focus (EF) tend to be more effective for movement pattern retraining compared to instructions promoting an internal focus (IF), for a variety of movement tasks. However, few studies have examined how different types of instructions affect running mechanics associated with running-related injury risk. Therefore, the purpose of this study was to compare the effects of instructions promoting different attentional foci on impact forces during running. DESIGN: Cross-sectional study. METHODS: Twenty uninjured female recreational runners ran at a self-selected speed with their typical pattern (no instructions condition) on an instrumented treadmill that measured ground reaction forces. Next, they were given 2 sets of instructions intended to alter their running pattern; one promoted an IF and the other promoted an EF. Repeated-measures analysis of variance was used to compare impact peaks and loading rates across the conditions (no instructions, IF, and EF), with post hoc tests conducted in the case of a significant omnibus test. RESULTS: There were differences among the conditions in the impact peaks (P < .001) and loading rates (P < .001). Impact peaks were lower for the IF (P = .002) and EF (P < .001) conditions compared to the no instructions condition. Loading rates were lower for the EF condition compared to the no instructions (P < .001) and IF (P < .001) conditions; there was no difference between the IF and no instructions conditions (P = .24). CONCLUSIONS: Our findings indicate that instructions promoting an EF may be more effective at reducing loading rates during running compared to instructions promoting an IF. Clinicians should consider these findings when attempting to retrain a runner's running pattern.

Sacral stress fractures in athletes.

PURPOSE: Fatigue stress fractures are a common overuse injury, frequently associated with high load-bearing endurance activities such as running, military training and aerobic exercise. While these fractures can arise at any site, sacral stress fractures are poorly studied with evidence consisting mainly of case reports and limited case series. This review aims to analyze and summarize all reports published to date describing cases of sacral stress fracture in athletes. METHODS: PubMed, Embase, Web of Science and the Cochrane Database were systematically searched for studies reporting on Stress Fractures of the Sacrum. Insufficiency fractures of the elderly were excluded. RESULTS: The literature review revealed 49 studies reporting on 124 cases of sacral stress fractures. Seventy-six patients (61%) were professional or collegiate level athletes, and 37 (30%) were military recruits or police officers in training. Seventeen female athletes were identified as suffering from low bone mineral density (25%), 9 of which reported menstrual irregularities. Thirteen female patients (19%) had a history of eating disorders. CONCLUSION: While most sacral stress fractures occur in normal bones exposed to abnormal repetitive loads, the high percentage of lower bone mineral density can blur the lines between fatigue fractures and insufficiency fractures. The causes of these fractures are multifactorial. High endurance sports and the features of the female athlete triad were found in high percentage of the cases. Conservative treatment is the mainstay of treatment, consisting of ceasing of training and a period of rehabilitation and gradual return to training and competition.

Trail running injury risk factors: a living systematic review.

OBJECTIVE: To review and frequently update the available evidence on injury risk factors and epidemiology of injury in trail running. DESIGN: Living systematic review. Updated searches will be done every 6 months for a minimum period of 5 years. DATA SOURCES: Eight electronic databases were searched from inception to 18 March 2021. ELIGIBILITY CRITERIA: Studies that investigated injury risk factors and/or reported the epidemiology of injury in trail running. RESULTS: Nineteen eligible studies were included, of which 10 studies investigated injury risk factors among 2 785 participants. Significant intrinsic factors associated with injury are: more running experience, level A runner and higher total propensity to sports accident questionnaire (PAD-22) score. Previous history of cramping and postrace biomarkers of muscle damage is associated with cramping. Younger age and low skin phototypes are associated with sunburn. Significant extrinsic factors associated with injury are neglecting warm-up, no specialised running plan, training on asphalt, double training sessions per day and physical labour occupations. A slower race finishing time is associated with cramping, while more than 3 hours of training per day, shade as the primary mode of sun protection and being single are associated with sunburn. An injury incidence range 0.7-61.2 injuries/1000 hours of running and prevalence range 1.3% to 90% were reported. The lower limb was the most reported region of injury, specifically involving blisters of the foot/toe. CONCLUSION: Limited studies investigated injury risk factors in trail running. Our review found eight intrinsic and nine extrinsic injury risk factors. This review highlighted areas for future research that may aid in designing injury risk management strategies for safer trail running participation.PROSPERO registration numberCRD42021240832.

Strategies to prevent and manage running-related knee injuries: a systematic review of randomised controlled trials.

OBJECTIVE: To evaluate the effectiveness of interventions to prevent and manage knee injuries in runners. DESIGN: Systematic review and meta-analysis. DATA SOURCES: MEDLINE, EMBASE, CINAHL, Web of Science and SPORTDiscus up to May 2022. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Randomised controlled trials (RCTs) with a primary aim of evaluating the effectiveness of intervention(s) to prevent or manage running-related knee injury. RESULTS: Thirty RCTs (18 prevention, 12 management) analysed multiple interventions in novice and recreational running populations. Low-certainty evidence (one trial, 320 participants) indicated that running technique retraining (to land softer) reduced the risk of knee injury compared with control treadmill running (risk ratio (RR) 0.32, 95% CI 0.16 to 0.63). Very low-certainty to low-certainty evidence from 17 other prevention trials (participant range: 24 -3287) indicated that various footwear options, multicomponent exercise therapy, graduated running programmes and online and in person injury prevention education programmes did not influence knee injury risk (RR range: 0.55-1.06). In runners with patellofemoral pain, very low-certainty to low-certainty evidence indicated that running technique retraining strategies, medial-wedged foot orthoses, multicomponent exercise therapy and osteopathic manipulation can reduce knee pain in the short-term (standardised mean difference range: -4.96 to -0.90). CONCLUSION: There is low-certainty evidence that running technique retraining to land softer may reduce knee injury risk by two-thirds. Very low-certainty to low-certainty evidence suggests that running-related patellofemoral pain may be effectively managed through a variety of active (eg, running technique retraining, multicomponent exercise therapy) and passive interventions (eg, foot orthoses, osteopathic manipulation). PROSPERO REGISTRATION NUMBER: CRD42020150630.

Chronic Disease, Allergies, and Increased Years of Running Are Risk Factors Predicting Gradual Onset Running-Related Injuries in Ultramarathon Runners-SAFER XIX Study in 29 585 Race Entrants.

OBJECTIVES: To identify risk factors that predict gradual onset running-related injuries (GORRIs) in ultramarathon runners entering a mass community-based event. DESIGN: Descriptive cross-sectional study. SETTING: Two Oceans 56 km ultramarathon 2012 to 2015. PARTICIPANTS: Race entrants (n = 42 003) completed a compulsory pre-race medical history questionnaire; 29 585 (70.4%) of entrants consented. DEPENDENT/OUTCOME VARIABLE: A history of GORRIs in the past 12 months among race entrants. MAIN OUTCOME MEASURES: In a multi-variate model, runner demographics, training variables (years of recreational running, weekly running distance, training running speed), history of chronic disease (composite score), and history of allergies were included as factors predicting GORRIs. Prevalence (%) and prevalence ratios (PR, 95% CIs) are reported. RESULTS: The lifetime prevalence of GORRIs in ultramarathon runners was 24.4%. Independent factors predicting GORRIs were: higher chronic disease composite score (PR = 2.05 times increase risk for every 2 additional chronic diseases; P < 0.0001), history of allergies (PR = 1.66; P < 0.0001), increased years of recreational running (PR = 1.07 times increased risk for every 5 year increase in running; P < 0.0001), lower average weekly running distance (PR = 0.98 times decreased risk for every 15 km increase weekly running distance; P < 0.0001), and slower average training running speed (PR = 0.96 times decreased risk for every km/h increase in training running speed; P < 0.0001). CONCLUSIONS: Novel risk factors predicting GORRIs are increased number of chronic diseases and a history of allergies. These factors, together with training variables (years of recreational running, weekly running distance, and training running speed) can be targeted to develop and implement injury prevention, treatment, and rehabilitation interventions in ultramarathon runners.

Should Adolescents Run Marathons?: Youth Marathon Training Injury Epidemiology and Risk Factors.

OBJECTIVE: Youth participation in distance running has increased, yet little data exist about the injury patterns and safety of such activity. This study seeks to determine the types and rates of injuries seen in an adolescent marathon training program. DESIGN: Observational prospective cohort study. SETTING: Community-based adolescent marathon training program. PARTICIPANTS: The study enrolled 1927 students from 50 high schools (HS) and 34 middle schools (MS) participating in the 2017 to 2018 Students Run Los Angeles marathon training program. ASSESSMENT OF RISK FACTORS: Weekly injury reports completed by running coaches. Data elements included participant demographics, weekly training distance, injury type, injury acuity, and missed training time. MAIN OUTCOME MEASURES: Epidemiology of self-reported injury in adolescent runners. RESULTS: A total of 583 injuries occurred in 18% of runners during the training program. High schools runners were more likely to be injured than MS runners (20.8% vs 14.2%, P < 0.001). Seventy-two percent of injuries were acute with a mean missed training time of 4.8 days (SD 4.8). The most frequent site of injury was the knee (33%). Overall, runners with injuries ran a significantly greater distance per week than uninjured runners (14.6 mi vs 12.0 mi, P < 0.001). Ninety-nine percent of marathon participants completed the race. CONCLUSIONS: During a 28-week marathon training program, 18% of adolescent participants reported an injury. More injuries occurred in HS students, were acute, and involved the knee. This study represents one of the largest descriptions of injury prevalence in adolescent distance running and highlights a lower injury rate than adults during marathon training.