Association of Dynamic Knee Valgus and Bone Stress Injury in US Military Academy Cadets.

CONTEXT: Early identification of incoming military personnel at elevated odds for bone stress injury (BSI) is important for the health and readiness of the US military. DESIGN: Prospective cohort study. METHODS: Knee kinematic data of the incoming US Military Academy cadets were collected while performing a jump-landing task (The Landing Error Scoring System) using a markerless motion capture system and depth camera. Data on incidence of lower-extremity injury, including BSI, were collected throughout the study period. RESULTS: A total of 1905 participants (452 females, 23.7%) were examined for knee valgus and BSI status. A total of 50 BSI occurred during the study period (incidence proportion = 2.6%). The unadjusted odds ratio for BSI at initial contact was 1.03 (95% confidence interval [CI], 0.94-1.14; P = .49). Adjusted for sex, the odds ratio for BSI at initial contact was 0.97 (95% CI, 0.87-1.06; P = .47). At the instant of maximum knee-flexion angle, the unadjusted odds ratio was 1.06 (95% CI, 1.02-1.10; P = .01), and the odds ratio was 1.02 (95% CI, 0.98-1.07; P = .29) after adjusting for sex. This suggests that there was not a significant enough association for an increase in the odds of BSI based on either degree of knee valgus. CONCLUSIONS: Our results did not demonstrate an association between knee valgus angle data during a jump-landing task and future increased odds of BSI in a military training population. Further analysis is warranted, but the results suggests the association between kinematics and BSI cannot be effectively screened by knee valgus angle data in isolation.

Examining the Dynamic Nature of Anterior Cruciate Ligament Injury Risk Factors in Women's Collegiate Soccer.

CONTEXT: Anterior cruciate ligament (ACL) injuries are a common and devastating injury in women's soccer. Several risk factors for ACL injury have been identified, but have not yet been examined as potentially dynamic risk factors, which may change throughout a collegiate soccer season. DESIGN: Prospective cohort study. METHODS: Nine common clinical screening assessments for ACL injury risk, consisting of range of motion, movement quality, and power, were assessed in 29 Division I collegiate women's soccer players. Preseason and midseason values were compared for significant differences. Change scores for each risk factor were also correlated with cumulative training loads during the first 10 weeks of a competitive soccer season. RESULTS: Hip external rotation range of motion and power had statistically significant and meaningful differences at midseason compared with preseason, indicating they are dynamic risk factors. There were no significant associations between the observed risk factor changes and cumulative training load. CONCLUSIONS: Hip external rotation range of motion and power are dynamic risk factors for ACL injury in women's collegiate soccer athletes. Serial screening of these risk factors may elucidate stronger associations with injury risk and improve prognostic accuracy of screening tools.

Automated Landing Error Scoring System Performance and the Risk of Bone Stress Injury in Military Trainees.

CONTEXT: Lower extremity bone stress injuries (BSIs) place a significant burden on the health and readiness of the US Armed Forces. OBJECTIVE: To determine if preinjury baseline performance on an expanded and automated 22-item version of the Landing Error Scoring System (LESS-22) was associated with the incidence of BSIs in a military training population. DESIGN: Prospective cohort study. SETTING: US Military Academy at West Point, NY. PATIENTS OR OTHER PARTICIPANTS: A total of 2235 incoming cadets (510 females [22.8%]). MAIN OUTCOME MEASURE(S): Multivariable Poisson regression models were used to produce adjusted incidence rate ratios (IRRs) to quantify the association between preinjury LESS scores and BSI incidence rate during follow-up and were adjusted for pertinent risk factors. Risk factors were included as covariates in the final model if the 95% CI for the crude IRR did not contain 1.00. RESULTS: A total of 54 BSIs occurred during the study period, resulting in an overall incidence rate of 0.07 BSI per 1000 person-days (95% CI = 0.05, 0.09). The mean number of exposure days was 345.4 ± 61.12 (range = 3-368 days). The final model was adjusted for sex and body mass index and yielded an adjusted IRR for a LESS-22 score of 1.06 (95% CI = 1.002, 1.13; P = .04), indicating that each additional LESS error documented at baseline was associated with a 6.0% increase in the incidence rate of BSI during the follow-up period. In addition, 6 individual LESS-22 items, including 2 newly added items, were significantly associated with the BSI incidence. CONCLUSIONS: We provided evidence that performance on the expanded and automated version of the LESS was associated with the BSI incidence in a military training population. The automated LESS-22 may be a scalable solution for screening military training populations for BSI risk.

Trends in movement quality in US Military Academy cadets 2005-17: A JUMP-ACL study.

OBJECTIVES: This study sought to determine if there were significant trends in lower extremity movement quality, as assessed by the Landing Error Scoring System (LESS) scores and plane-specific LESS subscales, across in 12 recent cohorts of incoming USMA cadets. DESIGN: prospective cohort study. SETTING: United States Military Academy. PARTICIPANTS: 7,591. MAIN OUTCOME MEASURES: Landing Error Scoring System (LESS) scores, adjusted for sex and ACL injury history. RESULTS: Statistically significant inverse trends were found between total LESS score and year (p < 0.01) and sagittal plane subscale and year (p < 0.01). A statistically significant direct trend was found for the frontal/transverse plane subscale and year (p < 0.01). However, each of these trends had a small associated effect size, and none were considered clinically meaningful. CONCLUSIONS: There were no meaningful changes in lower extremity movement quality in incoming US Military Academy cadets between 2005 and 2017.

Lower Extremity Movement Quality and the Internal Training Load Response of Male Collegiate Soccer Athletes.

CONTEXT: Training load and movement quality are associated with injury risk in athletes. Given these associations, it is important to understand how movement quality may moderate the training load so that appropriate injury-prevention strategies can be used. OBJECTIVE: To determine how absolute and relative internal training loads change during a men's National Collegiate Athletic Association (NCAA) soccer season and how movement quality, assessed using the Landing Error Scoring System (LESS), moderates the relative internal training load. DESIGN: Prospective cohort study. SETTING: Division I athletics. PATIENTS OR OTHER PARTICIPANTS: One NCAA Division I male collegiate soccer team was recruited and followed over 2 consecutive seasons. Fifty-two athletes (age = 19.71 ± 1.30 years, height = 1.81 ± 0.06 m, mass = 75.74 ± 6.64 kg) consented to participate, and 46 met the criteria to be included in the final statistical analysis. MAIN OUTCOME MEASURE(S): Daily absolute internal training load was tracked over 2 seasons using a rated perceived exertion scale and time, which were subsequently used to calculate the absolute and relative internal training loads. Movement quality was assessed using the LESS and participants were categorized as poor movers (LESS score ≥5) or good movers (LESS score ≤4). RESULTS: The 46 athletes consisted of 29 poor movers and 17 good movers. Absolute (P < .001) and relative (P < .001) internal training loads differed across the weeks of the season. However, movement quality did not moderate the relative internal training load (P = .264). CONCLUSIONS: Absolute and relative training loads changed across weeks of a male collegiate soccer season. Movement quality did not affect the relative training load, but future researchers need to conduct studies with larger sample sizes to confirm this result.

Correction to: The Relationship Between Training Load and Injury in Athletes: A Systematic Review.

"Cox proportional hazards regression models with frailty found no difference in injured vs. unin-jured players with week-to-week changes of < 20, 20-60, and > 60%, controlling for scapular con-trol, isometric rotational and abduction strength, and shoulder range of motion (p value ranges 0.09-0.68).

The Relationship Between Training Load and Injury in Athletes: A Systematic Review.

BACKGROUND: The relationship between training load and musculoskeletal injury is a rapidly advancing area of research in need of an updated systematic review. OBJECTIVE: This systematic review examined the evidence for the relationship between training load and musculoskeletal injury risk in athlete, military, and first responder (i.e. law enforcement, firefighting, rescue service) populations. METHODS: The CINAHL, EMBASE, MEDLINE, SportDISCUS, and SCOPUS databases were searched using a comprehensive strategy. Studies published prior to July 2017 were included if they prospectively examined the relationship between training load and injury risk. Study quality was assessed using the Newcastle-Ottawa Quality Assessment Scale (NOS) and Oxford Centre for Evidence-Based Medicine levels of evidence. A narrative synthesis of findings was conducted. RESULTS: A total of 2047 articles were examined for potential inclusion. Forty-six met the inclusion criteria and 11 known to the authors but not found in the search were added, for a total of 57 articles. Overall, 47 studies had at least partially statistically significant results, demonstrating a relationship between training load and injury risk. Included articles were rated as poor (n = 15), fair (n = 6), and good (n = 36) based on NOS score. Articles assessed as 'good' were considered level 2b evidence on the Oxford Centre for Evidence-Based Medicine Model, and articles assessed as 'fair' or 'poor' were considered level 4 evidence. CONCLUSIONS: Our results demonstrate that the existence of a relationship between training load and injury continues to be well supported in the literature and is strongest for subjective internal training load. The directionality of this relationship appears to depend on the type and timeframe of load measured.

Epidemiology of Hip Flexor and Hip Adductor Strains in National Collegiate Athletic Association Athletes, 2009/2010-2014/2015.

BACKGROUND: Little research has examined the rates and patterns of hip flexor or hip adductor strains in student-athletes in the National Collegiate Athletic Association (NCAA). PURPOSE: To describe the epidemiology of hip flexor and adductor strains in NCAA athletes during the 2009/2010-2014/2015 academic years. STUDY DESIGN: Descriptive epidemiology study. METHODS: Rates and patterns of hip flexor and adductor strains in collegiate sports were examined in a convenience sample of NCAA varsity teams from 25 sports. Rates and distributions of strains by mechanism, recurrence, and participation restriction time were examined. Injury rate ratios (IRRs) and proportion ratios were calculated to compare rates within and between sports by event type, sex, mechanism, recurrence, and participation restriction time. RESULTS: A total of 770 hip flexor and 621 hip adductor strains were reported, resulting in overall injury rates of 1.60 and 1.29 per 10,000 athlete-exposures (AEs), respectively. In men, the rate of hip flexor strains was 1.81 per 10,000 AEs, and that for hip adductor strains was 1.71 per 10,000 AEs. In women, the rate of hip flexor strains was 1.59 per 10,000 AEs, and the rate of hip adductor strains was 1.15 per 10,000 AEs. The highest rates of strains were found in men's soccer and men's ice hockey (range, 2.47-3.77 per 10,000 AEs). Most hip flexor and hip adductor strains occurred in practice, but both had higher rates in competition. In sex-comparable sports, hip flexor strain rates did not differ between the sexes (IRR = 1.14; 95% CI, 0.96-1.36), but the rate of hip adductor strains was higher in men than women (IRR = 1.49; 95% CI, 1.22-1.81). Noncontact was the most common mechanism for both types of strains (hip flexor strains, 59.4%; hip adductor strains, 62.5%); 10.1% of hip flexor strains and 11.1% of hip adductor strains were recurrent. The highest rates of recurrence of both types of strain were found in men's and women's ice hockey (range, 16.0%-30.6%). Most hip flexor and hip adductor strains resulted in <1 week of participation restriction (hip flexor strains, 83.8%; hip adductor strains, 82.9%). CONCLUSION: The NCAA sports with the highest rates of hip flexor and hip adductor strains were men's soccer and men's ice hockey. In sex-comparable sports, men had a higher rate of hip adductor, but not hip flexor, strains. Recurrence rates were remarkably high in ice hockey. Male sports teams, especially soccer and ice hockey, should place an emphasis on prevention programs for hip adductor strains. Secondary prevention programs involving thorough rehabilitation and strict return-to-play criteria should be developed and implemented to curb the high recurrence rate of these injuries, particularly in ice hockey.

Epidemiology of Quadriceps Strains in National Collegiate Athletic Association Athletes, 2009-2010 Through 2014-2015.

CONTEXT: Few researchers have examined the rates and patterns of quadriceps strains in student-athletes in the National Collegiate Athletic Association (NCAA). OBJECTIVE: To describe the epidemiology of quadriceps strains in 25 NCAA sports during the 2009-2010 through 2014-2015 academic years. DESIGN: Descriptive epidemiology study. SETTING: Convenience sample of NCAA programs from 25 sports during the 2009-2010 through 2014-2015 academic years. Patients or Other Particpants: Collegiate student-athletes participating in men's and women's NCAA athletics during the 2009-2010 through 2014-2015 academic years. MAIN OUTCOME MEASURE(S): Aggregate quadriceps strain injury and exposure data from the NCAA Injury Surveillance Program during the 2009-2010 through 2014-2015 academic years were analyzed. Quadriceps strain injury rates and injury rate ratios (IRRs) were reported with 95% confidence intervals (CIs). RESULTS: Overall, 517 quadriceps strains were reported, resulting in an injury rate of 1.07/10 000 athlete-exposures (AEs). The sports with the highest overall quadriceps strain rates were women's soccer (5.61/10 000 AEs), men's soccer (2.52/10 000 AEs), women's indoor track (2.24/10 000 AEs), and women's softball (2.15/10 000 AEs). Across sex-comparable sports, women had a higher rate of quadriceps strains than men overall (1.97 versus 0.65/10 000 AEs; IRR = 3.03; 95% CI = 2.45, 3.76). The majority of quadriceps strains were sustained during practice (77.8%). However, the quadriceps strain rate was higher during competition than during practice (1.29 versus 1.02/10 000 AEs; IRR = 1.27; 95% CI = 1.03, 1.56). Most quadriceps strains occurred in the preseason (57.8%), and rates were higher during the preseason compared with the regular season (2.29 versus 0.63/10 000 AEs; IRR = 3.60; 95% CI = 3.02, 4.30). Common injury mechanisms were noncontact (63.2%) and overuse (21.9%). Most quadriceps strains restricted participation by less than 1 week (79.3%). CONCLUSIONS: Across 25 sports, higher quadriceps strain rates were found in women versus men, in competitions versus practices, and in the preseason versus the regular season. Most quadriceps strains were minor in severity, although further surveillance is needed to better examine the risk factors associated with incidence and severity.

Static foot posture associated with dynamic plantar pressure parameters.

STUDY DESIGN: Controlled laboratory study. OBJECTIVE: To explore potential associations between foot posture index (FPI-6) composite scores and dynamic plantar pressure measurements, and to describe each of the 6 subscales and the FPI-6 composite scores across our sample. BACKGROUND: The FPI-6 is a static foot posture assessment comprised of 6 observations. Extreme scores have been associated with increased injury risk. However, knowledge describing the relationship between FPI-6 scores and plantar pressure distributions during gait is limited. METHODS: Participants (n = 1000; 566 males, 434 females) were predominantly active adults (mean ± SD age, 30.6 ± 8.0 years; body mass index, 26.2 ± 3.7 kg/m²), who ran 3.1 ± 1.4 d/wk. Static and dynamic foot characteristics were compared using the FPI-6 and a capacitance-based pressure platform. Correlation and hierarchical stepwise regression analyses were performed to determine the most parsimonious set of dynamic pressure data associated with FPI-6 scores. RESULTS: The mean ± SD FPI-6 score was 3.4 ± 2.9 (range, -6.0 to 11.0). Only 31 participants received a score of -2 (supinated foot) on any FPI-6 subscale. Classification of a pronated foot was 2.4 times more likely than a supinated foot. A 5-variable model (R = 0.57, R2 = 0.32) was developed to describe the association between dynamic plantar pressures and FPI-6 scores. CONCLUSION: The multivariate model associated with FPI-6 scores comprised clinically plausible variables which inform the association between static and dynamic foot postures. Different cutoff values may be required when using the FPI-6 to screen for individuals with supinated feet, given the limited number of high-arched participants identified by FPI-6 classifications.