Cross-country Runners Research Articles

Differences in Body Composition, Bone Density, and Tibial Microarchitecture in Division I Female Athletes Participating in Different Impact Loading Sports.

Sport participation affects body composition and bone health, but the association between sport, body composition, and bone health in female athletes is complex. We compared areal bone mineral density (aBMD, DXA) and tibial volumetric bone mineral density (vBMD), geometry, microarchitecture, and estimated strength (HR-pQCT) in cross-country runners (n = 22), gymnasts (n = 23) and lacrosse players (n = 35), and investigated associations of total body lean mass (TBLM), team, and their interaction with tibial bone outcomes. Total body (TB), total hip (TH), femoral neck (FN), and lumbar spine (LS) aBMD were higher in gymnasts than runners (p < 0.001); FN and LS aBMD were higher in gymnasts than lacrosse players (p ≤ 0.045); and TB, TH, FN, and LS aBMD were higher in lacrosse players than runners (p ≤ 0.013). At the distal tibial metaphysis, total area (Tt.Ar) was higher in gymnasts than runners (p = 0.004); cortical area and thickness (Ct.Ar, Ct.Th) were higher in lacrosse players than runners (p ≤ 0.044); trabecular separation (Tb.Sp) was higher in runners than gymnasts (p = 0.031); and failure load was higher in both gymnasts and lacrosse players than runners (p ≤ 0.012). At the tibial diaphysis, Tt.Ar, Ct.Ar, cortical perimeter (Ct.Pm), and failure load were higher in gymnasts than runners (p ≤ 0.040). In multiple linear regression analyses, TBLM was significantly associated with metaphyseal failure load (ß = 0.30, p = 0.042), and diaphyseal Tt.Ar and Ct.Pm (ß = 6.17, p = 0.003; ß = 0.59, p = 0.010). Bone health can vary among different sport types and is associated with TBLM, which may be a modifiable factor to maintain or improve bone health.

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

Off-road running is a growing sport with little research investigating injury profiles of female participants. Bone stress injuries (BSIs) are a particularly detrimental injury with little known about their incidence and risk factors in female off-road runners. Collate and review the available evidence reporting epidemiological data and risk factors associated with BSI in female off-road runners. Systematic literature review, without meta-analyses. MEDLINE OVID, PubMed, SPORTDiscus, and MEDLINE EBSCO. Searches were finalized in July 2024. Studies that reported injury surveillance statistics and/or risk factors associated with BSIs in female off-road runners. Seventeen eligible studies were included, of which all reported surveillance statistics and 2 reported risk factors associated with BSI among 897 female runners. Owing to the scarcity of data, cross-country runners were included in the population of off-road runners. Most BSIs were high severity and in the lower leg, with an overall incidence ranging from 0 to 34.39 BSIs per 100,000 athlete-exposures and prevalence ranging from 0% to 40.9%. Study characteristics were reported alongside risk of bias, quality, and level of evidence assessment outcomes from varying tools. Eight significant intrinsic risk factors were associated with BSIs in female off-road runners: increasing age, disrupted menstruation, previous BSI, increased female triad risk, and lower calcium, vitamin D, and calorie intake. Limited by the number of studies available reporting data on the specific target population, which highlights the need for performing high-quality prospective studies in the future, this review summarizes the current epidemiological data and risk factors associated with BSIs in female off-road runners.

Asymptomatic female softball pitchers have altered hip morphology and cartilage composition

Few studies have explored hip morphology and cartilage composition in female athletes or the impact of asymmetric repetitive loading, such as occurs during softball pitching. The current cross-sectional study assessed bilateral bony hip morphology on computed tomography imaging in collegiate-level softball pitchers (‘Pitch1’, n = 25) and cross-country runners (‘Run’, n = 13). Magnetic resonance imaging was used to assess cartilage relaxation times in a second cohort of pitchers (‘Pitch2’, n = 10) and non-athletic controls (‘Con’, n = 4). Pitch1 had 52% greater maximum alpha angle than Run (p < 0.001) and were 21.3 (95% CI 2.4 to 192.0) times more likely to have an alpha angle ≥ 60° within at least one hip. Pitch2 had longer T2 relaxation times in the superior femoral cartilage of the drive leg (same side as the throwing arm) and stride leg than Con (all p < 0.02). The drive leg in Pitch2 had longer T1ρ and T2 relaxation times in the superior femoral cartilage compared to the stride leg (all p ≤ 0.03). Asymptomatic softball pitchers exhibit altered bony hip morphology and cartilage composition compared to cross-country runners and non-athletic controls, respectively. They also exhibit asymmetry in cartilage composition. Further studies with larger sample sizes are warranted and any potential long-term consequences of the changes in terms of symptom and osteoarthritis development requires investigation.

The Running Readiness Scale and Injury in Collegiate Track & Field and Cross Country Athletes.

Track & field and cross country athletes experience high rates of lower extremity injuries. The Running Readiness Scale (RRS) may help determine which athletes have a higher likelihood of lower extremity injury. To determine if RRS performance at the start of the season was related to likelihood of experiencing a lower extremity injury during the subsequent track & field or cross country season. Prospective cohort study. University. 113 NCAA Division III track & field athletes in running, jumping and vaulting events and cross country runners (50 female, 63 male, mean±SD age 19.9±1.3 years). Athletes were assessed on RRS tasks: double-leg hops, plank, step ups, single-leg squats, and wall sit at the start of their season and then were observed by team athletic trainers during the season for occurrence of lower extremity injuries that resulted in missing one or more practices or meets. Adjusted Odds Ratios (AOR) and 95% confidence intervals (CIs) were used to assess the likelihood of lower extremity injury. Thirty-seven athletes (32.7%) experienced a lower extremity injury. Athletes scoring ≤3 on the RRS were almost five times more likely to experience lower extremity injury (AOR=4.8; 95%CI: 2.1-11.3) than athletes scoring ≥ 4. Athletes failing double-leg hops or wall sit tasks were more likely to experience lower extremity injury (p<0.05). Track & field and cross country athletes with RRS scores of ≤3 had a higher likelihood of lower extremity injury than those with scores of ≥4.

Influence of cadence manipulation on running biomechanics in high school cross-country runners

ABSTRACT Increasing cadence is an intervention to reduce injury risk for adolescent long-distance runners. It is unknown how adolescents respond biomechanically when running with a higher than preferred cadence. We examined the influence of increasing cadence on peak joint angles, moments and powers, and ground reaction forces in long-distance runners. We collected three-dimensional kinematics and kinetics for 31 high school cross-country runners during overground running at their preferred cadence (baseline), +5%, and +10% baseline cadence. We performed repeated-measures ANOVAs to compare peak joint angles, moments and powers, and ground reactions forces among cadence conditions. Increasing cadence reduced peak pelvis, hip, knee, and ankle joint angles (p ≤ .01), peak knee moment and powers (p < .001), peak ankle power (p ≤ .01), and peak ground reaction forces (p ≤ .01) but increased peak hip moment and powers (p < .001). Increasing cadence by 10% elicited greater magnitude changes compared to increasing cadence by 5%. Increasing cadence may be a beneficial intervention to reduce lower extremity peak joint angles and knee kinetics for adolescent long-distance runners. The increase in hip kinetics when running at a higher than preferred cadence indicates this intervention increases the loads applied to the hip for adolescent long-distance runners.

Effect of tapering peak on physiological variables and Digital level of female cross-country runners

Effect of tapering peak on physiological variables and Digital level of female cross-country runners

Dietary Intake and Diet Quality of Female and Male NCAA Division I Cross Country Runners from a Single University

BackgroundCollegiate student-athletes have unique nutritional requirements to support their athletic performance and health. Few studies have comprehensively characterized the diets of National Collegiate Athletic Association (NCAA) Division I student-athletes. ObjectivesTo characterize dietary intake and diet quality during a competitive season in female and male NCAA Division I cross country student-athletes from a single university. MethodsFemales and males (n = 14/sex) from the Florida State University cross country teams completed 9-d of food records across their competitive season. Nutrient intakes were compared to the Dietary Reference Intakes for the United States population [e.g., Recommended Daily Allowances (RDAs)] and athlete-specific guidelines. Diet quality was assessed according to the Dietary Guidelines for Americans (DGAs) using the 2020 Healthy Eating Index (HEI-2020). Total daily energy expenditure was estimated from training records. ResultsCarbohydrate intakes were below athlete guidelines in 43% of females (mean ± SD, 5.67 ± 1.16 g·kg–1·d–1) and 29% of males (4.95 ± 1.05, P sex = 0.096). All participants met or exceeded athlete recommendations for protein (2.09 ± 0.425 g·kg–1·d–1, 1.92 ± 0.519, P sex = 0.36) and fat (32.8 ± 5.1% kcal, 34.4 ± 3.4%, P sex = 0.36). No participants met the RDA for vitamin D (5.14 ± 1.78 μg/d, 4.91 ± 3.24, P sex = 0.83). Only 79% of females and 36% of males met the RDA for calcium (1220 ± 307 mg/d, 1010 ± 296, P sex = 0.83). Most females (n = 13) and males (n = 11) consumed iron supplements where total intakes exceeded the tolerable upper intake level (110 ± 60.1 mg/d, 66.8 ± 36.3, P sex = 0.029). HEI-2020 indicated poor adherence to the DGAs, with better diet quality in females (65.3 ± 13.7) than males (50.6 ± 10.1, P sex = 0.0034). Participants failed to meet guidelines for all HEI-2020 food group components except total protein foods. Total daily energy expenditure was greater in males and declined across the competitive season (P sex < 0.0001, P time < 0.0001, P sex∗time = 0.25). ConclusionsNCAA Division I cross country student-athletes consumed inadequate carbohydrates, calcium, and vitamin D but met or exceeded intake guidelines for protein, fat, and iron. Diet quality was poor; HEI-2020 component scores may indicate food groups to target to improve diet quality and intake of nutrients important to runners.This trial was registered at clinicaltrials.gov as NCT04079322.

Relationship Between Hip Strength And Hip Mechanics During Running And Jumping In Collegiate Cross-Country Runners

Relationship Between Hip Strength And Hip Mechanics During Running And Jumping In Collegiate Cross-Country Runners

Cross-sectional size, shape, and estimated strength of the tibia, fibula and second metatarsal in female collegiate-level cross-country runners and soccer players

Bone stress injuries (BSIs) frequently occur in the leg and foot long bones of female distance runners. A potential means of preventing BSIs is to participate in multidirectional sports when younger to build a more robust skeleton. The current cross-sectional study compared differences in tibia, fibula, and second metatarsal diaphysis size, shape, and strength between female collegiate-level athletes specialized in cross-country running (RUN, n = 16) and soccer (SOC, n = 16). Assessments were performed using high-resolution peripheral quantitative computed tomography and outcomes corrected for measures at the radius diaphysis to control for selection bias and systemic differences between groups. The tibia in SOC had a 7.5 % larger total area than RUN, with a 29.4 % greater minimum second moment of area (IMIN) and 8.2 % greater estimated failure load (all p ≤ 0.02). Tibial values in SOC exceeded reference data indicating positive adaptation. In contrast, values in RUN were similar to reference data suggesting running induced limited tibial adaptation. RUN did have a larger ratio between their maximum second moment of area (IMAX) and IMIN than both SOC and reference values. This suggests the unidirectional loading associated with running altered tibial shape with material distributed more in the anteroposterior (IMAX) direction as opposed to the mediolateral (IMIN) direction. Comparatively, SOC had a similar IMAX/IMIN ratio to reference data suggesting the larger tibia in SOC resulted from multiplane adaptation. In addition to enhanced size and strength of their tibia, SOC had enhanced structure and strength of their fibula and second metatarsal. At both sites, polar moment of inertia was approximately 25 % larger in SOC compared to RUN (all p = 0.03). These data support calls for young female athletes to delay specialization in running and participate in multidirectional sports, like soccer, to build a more robust skeleton that is potentially more protected against BSIs.

Week-to-week changes in training were not prospectively associated with injuries among Wisconsin high school cross-country runners

BackgroundTraining characteristics, such as volume and duration, have been studied in relation to running-related injury (RRI) risk, with mixed findings in adult runners. There is a lack of research assessing...

Epidemiology of Bone-Stress Injuries and Health Care Use in Pac-12 Cross-Country Athletes.

Bone-stress injury (BSI) is common in collegiate athletes. Injury rates and health care use in running athletes are not well documented. To describe the rate and classification of injury and associated health care use in collegiate cross-country runners with BSI. Descriptive epidemiology study. Sports medicine facilities participating in the Pac-12 Health Analytics Program. Pac-12 Conference collegiate cross-country athletes. Counts of injury and health care resources used for each injury. Injury rates were calculated based on athlete-seasons. A total of 168 BSIs were reported over 4 seasons from 80 team-seasons (34 men's and 46 women's team-seasons) and 1220 athlete-seasons, resulting in 1764 athletic training services and 117 physician encounters. Bone-stress injuries represented 20% of all injuries reported by cross-country athletes. The average BSI rate was 0.14 per athlete-season. Injury rates were higher in female (0.16) than male (0.10) athletes and higher in the 2019-2020 season (0.20) than the 2020-2021 (0.14), 2018-2019 (0.12), and 2021-2022 (0.10) seasons. Most BSIs occurred in the lower leg (23.8%) and the foot (23.8%). The majority of injuries were classified as overuse and time loss (72.6%) and accounted for most of the athletic training services (75.3%) and physician encounters (72.6%). We found a mean of 10.89 athletic training services per overuse and time-loss injury and 12.20 athletic training services per overuse and non-time-loss injury. Mean occurrence was lower for physician encounters (0.70), prescription medications (0.04), tests (0.75), procedures (0.01), and surgery (0.02) than for athletic training services (10.50). Bone-stress injuries are common in collegiate cross-country runners and require considerable athletic training resources. Athletic trainers should be appropriately staffed for this population, and suspected BSIs should be confirmed with a medical diagnosis. Future investigators should track treatment codes associated with BSI to determine best-practice patterns.

Sex Differences in Exercise-Induced Modulation of the Humoral Immune Response to Influenza Vaccination

Physical activity is known to modulate immune cell function and understanding its role in vaccine-induced immunity is critical for both optimizing vaccine strategies and implementing lifestyle factors that contribute to better immune health. This study aimed to elucidate the impact of physical activity on antibody responses following influenza vaccination, with a specific focus on biological sex differences among male and female cross-country athletes. Based on previous studies, we hypothesized that physical activity would increase immune responses, regardless of biological sex. Two cohorts of male and female Division III college cross-country runners and two cohorts of non-athletes (no physical activity) participated in this longitudinal investigation. Studies were conducted in two separate influenza seasons where participants received a quadrivalent seasonal influenza vaccine (2020-21 and 2022-23). An estimated non-adjusted VO2 max was calculated, and a survey was administered to identify overall health status prior to the start of the study. Blood samples were collected at predefined intervals to assess pre- and post-vaccination antibody responses specific for the H1N1 component of each seasonal influenza vaccine. VO2 max, a measure of overall fitness, was higher in the athletes as compared to those participants who were not physically active, and these results were consistent among both males and females. All participants mounted an immune response to the seasonal influenza vaccine as indicated by a rise in vaccine-specific antibody titers from pre-vaccination to post-vaccination. However, the differences in titers were sex specific, with greater neutralizing antibody titers in females as compared to males — regardless of their level of physical activity. When data were further partitioned by physical activity level, it was identified that although males have lower antibody responses than females, males that were cross country runners had significantly greater antibody responses than males that were not physically active. This study contributes valuable insights into the complex interplay between exercise, sex, and immune responses. Understanding these dynamics could inform recommendations for individuals to be engaged in regular physical activity to optimize overall immune health. This research was funded by a College of Saint Benedict and Saint John's University Faculty Development and Research Committee Award. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Variability in Limb Occlusion Pressures Across Visits and Between Limbs in Collegiate Soccer and Cross Country Athletes

Our study assessed limb occlusion pressure (LOP) variability over time and between limbs. Collegiate athletes (n=42; Sample 1 = 15 soccer players, Sample 2 = 13 cross country runners, Sample 3 = 14 cross country runners) attended five visits separated by ≥48 hours (Sample 1), three visits separated by ~3 weeks each (Sample 2), or four visits separated by ~3 weeks each (Sample 3). For all samples, supine LOP was assessed in each leg (and also in each arm for Sample 3) using an automated system. Paired samples t-tests or RMANOVA were used to compare LOP between limbs and across trials, respectively. Additionally, agreement and variability across measures were assessed using intraclass correlations and mean absolute percent differences (MAPD). There were no significant differences in LOP across visits for any of the samples, with primarily moderate or good agreement (intraclass correlations r=0.29-0.88) and low variability (MAPD 4.3-9.0%). There were no significant differences in LOP between left and right limbs, with moderate to good agreement (r=0.74-0.93) and low variability (MAPD 3.2-7.2%). The demonstrated stability in LOP over time and between sides of the body suggests that LOP may not always need to be measured daily or bilaterally, adding feasibility to field-based implementation.

Developmental Trend of Talented Pupils' Performance in Orienteering - Longitudinal Research 1997-2020 in the East Bohemia Region of the Czech Republic

The paper presents the findings of a longitudinal testing of talented youth in orienteering in the Czech Republic. Young talented orienteers participate in the testing of motor skills by standardized tests. The results and conclusions of the 3 km and 5 km cross-country running measurements (according to age category) point to a regressive state of endurance abilities in young athletes between 1997 and 2020, describe possible reasons and suggest possible remedies. A total of 300 girls and 445 boys aged 12-14 years participated in the research investigation in the East Bohemian Region of the Czech Republic, who are divided into performance categories HD12 and HD14 in the context of organised Czech orienteering competition. The aim of the evaluation of the longitudinal testing was to determine the trends in performance in endurance cross-country running as a key performance parameter of talented orienteering athletes over the period 1997 to 2020. The resulting data indicate that performance in all the studied categories in the given field test has a consistently decreasing trend. The results are also related to the conclusions of foreign and domestic observations of the state of motor fitness of children and youth of the corresponding period and indicate that the level of aerobic ability of young talented runners generally follows the current state of the level of endurance ability found in the national testing of school youth under the auspices of the Czech School Inspectorate (CSI, 2023), and thus the alarming society-wide situation in the field of motor fitness of children and youth in the Czech Republic.

The Effect of Cross Country Running Training on Increasing the VO2Max of Alfalah Futsal Players

This study aims to determine the effect of cross-country running training on increasing VO2Max. This research was conducted at the Jambi cross-country from July to August. Sixteen treatments were administered at a frequency of three times per week. In this study, a single group pretest-posttest was employed as the designThe researchers targeted Al-falah futsal players as their population. For a sample of sixteen individuals, inclusion and exclusion criteria were employed. The research instrument used in this study measures VO2max pretest and posttest, namely from the Multi Stage Fitness Test. The data analysis processes of homogeneity, normalcy, and hypothesis testing are carried out using SPSS. The study's normality and homogeneity statistics further demonstrate that the distribution is homogeneous and normal (sig. &gt; 0.05). A significant value of 0.000 &lt; 0.05 in the hypothesis testing results indicates that cross-country running training increased the VO2max of Al-Falah futsal players. Based on these findings, the cross-country running training program is an effective training program for increasing VO2max.

Amenorrhea and Stress Fractures in Female New Jersey Division III Collegiate Runners: An Opportunity for Increased Health Education

BACKGROUND: In the National Collegiate Athletic Association (NCAA), 9.1% of the injuries reported by women’s cross-country athletes between 2014-2019 were fractures. Both history of amenorrhea and prior stress fractures have been found to predict incidence of subsequent bone stress injuries among female athletes. Although excessive exercise is a major contributor to the development of amenorrhea, there are currently no studies on the association between amenorrhea and stress fractures in New Jersey (NJ) National NCAA Division III Women’s cross country or track athletes. This study aims to determine if there is an association between incidence of amenorrhea and subsequent occurrence of stress fractures among this population, and to identify a possible area for increased reproductive health education. METHODS: This is a survey-based study. Participants were female athletes over the age of 18 who currently participate in collegiate cross country or track running at a NJ Division III school. Coaches of the Division III cross country and track teams in NJ distributed a survey to their female athletes to gain participants for this study. Survey data included information on participant menstrual history, stress fracture history, and athletic involvement. Participants also indicated if their school’s staff had ever educated them on the importance of menstrual regularity and athletics. Descriptive statistics and comparison between groups were analyzed. RESULTS: In total, 68 survey responses were collected. Survey respondents included female NJ cross country and track athletes ages 18-23, from a total of eight institutions. During training or competition, 58.8% of the study participants missed at least one menstrual cycle and 45.6% experienced a stress fracture. There is a significant association between having missed at least one menstrual cycle during training or competition and the number of stress fractures experienced by the athlete (p = 0.044). Only 30.9% of respondents indicated that someone from their school’s staff spoke to them about the importance of maintaining regular menstruation during training. CONCLUSION: This study confirms that both amenorrhea and stress fractures are commonly seen among NJ NCAA Division III female cross country and track athletes. Our data also highlights a need for increased education of NJ Division III female athletes regarding the importance of maintaining regular menstruation as a means of stress fracture prevention. Further investigation of the role of amenorrhea on the incidence of stress fractures may shine light on an important area for prevention and increased health education.

Yoga Tips for Cross Country and Distance Runners

Cross country has grown in popularity and provides youth with the ability to put into practice both physical capability and mental strength and preparedness. However, such preparedness can also lead to physical injuries such as shin splints, or mental fatigue, which can lead to dropout and/or burnout. Yoga is an activity that has become increasingly popular and has been shown to present both physical and mental benefits to its participants. This article aims to provide foundational information for coaches and young cross country and distance athletes to put yoga into action for physical and mental practice. Specific postures are provided with special benefits, stretches, and strengthening information to ensure the basic understanding of the why behind each pose and how that pose tackles a particular challenge for runners.

Retraction: Alexander C. Wu, Mitchell J. Rauh PT, PhD, MPH, FACSM, Stephanie DeLuca MD, Margo Lewis, Kathryn E. Ackerman MD, MPH, Michelle T. Barrack PhD, RD, CSSD, Bryan Heiderscheit PT, PhD, FAPTA, Brian J. Krabak MD, MBA, William O. Roberts MD, Adam S. Tenforde MD. Running-related injuries in middle school cross-country runners: Prevalence and characteristics of common injuries. PM&R. 2022;

The above article, published online on 30 May 2021 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor in Chief Dr. Janna Friedly, the American Academy of Physical Medicine and Rehabilitation, and Wiley Periodicals LLC. The retraction has been agreed upon following a joint review by the authors' institutions which identified the dataset of this article to be unreliable and not accurately represented in the paper. The institutions did not find the listed authors to be responsible for the data unreliability but have recommended that the paper be retracted.

Changes in the incidence of stress reactions and fractures among intercollegiate athletes after the COVID-19 pandemic

PurposeThe purpose of this study was to characterize the impact of detraining due to the COVID-19 pandemic on incidence of bony injuries and stress fractures in collegiate athletes.MethodsA comprehensive collegiate athletic conference injury database was queried for all in-season, sport-related bony injuries (defined as all stress reactions and fractures) that occurred across all sports from January 2016 to June 2021. The bony injury rate per 1000 athlete exposure hours (AEH) was calculated and compared between the immediate post-hiatus season and historic rates from pre-hiatus seasons (2016–2019). Injury characteristics were also compared between the pre- and post-hiatus time periods.ResultsA total of 868 bony injuries across 23 sports were identified. The sports with highest overall baseline bony injury rates in historic seasons were women’s cross country (0.57 injuries per 1000 AEH) and men’s cross country (0.32). Compared to historic pre-hiatus rates, female cross-country runners demonstrated a significantly lower bony injury incidence rate in the post-hiatus season (0.24 vs. 0.57, p = 0.016) while male swimming athletes demonstrated a statistically significant increase in bony injury rate (0.09 vs. 0.01, p = 0.015). The proportion of bony injuries attributed to repetitive trauma increased; while, the proportion of injuries attributed to running decreased between the pre- and post-hiatus seasons.ConclusionAcross all sports, there was no consistent trend toward increased rates of bony injury in the immediate post-hiatus season. However, female cross-country runners demonstrated lower rates of bony injury in the post-hiatus season while male swimmers demonstrated higher rates. Furthermore, bony injuries in the post-hiatus season were more likely to be the result of repetitive trauma and less likely to be from running.Level of Evidence: Level III, retrospective, cross sectional study.

A hierarchical clustering approach for examining the relationship between pelvis-proximal femur geometry and bone stress injury in runners

Bone stress injury (BSI) risk in runners is multifactorial and not well understood. Unsupervised machine learning approaches can potentially elucidate risk factors for BSI by identifying groups of similar runners within a population which differ in BSI incidence. Here, a hierarchical clustering approach is used to identify groups of collegiate cross country runners based on 2-dimensional frontal plane pelvis and proximal femur geometry, which was extracted from dual-energy X-ray absorptiometry scans and dimensionally reduced by principal component analysis. Seven distinct groups were identified using the cluster tree, with the initial split being highly related to female-male differences. Visual inspection revealed clear differences between groups in pelvis and proximal femur geometry, and groups were found to differ in lower body BSI incidence during the subsequent academic year (Rand index = 0.53; adjusted Rand index = 0.07). Linear models showed between-cluster differences in visually identified geometric measures. Geometric measures were aggregated into a pelvis shape factor based on trends with BSI incidence, and the resulting shape factor was significantly different between clusters (p < 0.001). Lower shape factor values, corresponding with lower pelvis height and ischial span, and greater iliac span and trochanteric span, appeared to be related to increased BSI incidence. This trend was dominated by the effect observed across clusters of male runners, indicating that geometric effects may be more relevant to BSI risk in males, or that other factors masked the relationship in females. More broadly, this work outlines a methodological approach for distilling complex geometric differences into simple metrics that relate to injury risk.