The feasibility of workload monitoring among law enforcement officers: A multi-methodological approach

This study examined the feasibility of workload monitoring to assess internal workload in law enforcement officers (LEO) using a multi-methodological approach. Fifty front-line LEO completed workload surveys on workdays for eight weeks. Retention and adherence were assessed across the survey period. LEO completed usability and likelihood to continue questionnaires, while departmental administrators (n = 8) received workload reports and completed utility and sustainability questionnaires. A subsample of LEO and administrators participated in semi-structured interviews, following consensual qualitative research design. LEO retention (96%), survey adherence (94%), and usability scores (88.3/100) were high, with a moderate likelihood to continue to use the survey. Administration reported high utility and sustainability. The high adherence rates and usability scores, coupled with strong administrative support, suggest that workload monitoring may be a feasible strategy among LEO to monitor occupational workloads. The LEO and administration feedback highlight areas of improvement (e.g., data transparency, departmental collaboration) to inform future implementation.

Modeling Risk for Lower Extremity Musculoskeletal Injury in U.S. Military Academy Cadet Basic Training

INTRODUCTION

Sport and tactical populations are often impacted by musculoskeletal injury. Many publications have highlighted that risk is correlated with multiple variables. There do not appear to be existing studies that have evaluated a predetermined combination of risk factors that provide a pragmatic model for application in tactical and/or sports settings.

PURPOSE

To develop and test the predictive capability of multivariable risk models of lower extremity musculoskeletal injury during cadet basic training at the U.S.Military Academy.

MATERIALS AND METHODS

Cadets from the class of 2022 served as the study population. Sex and injury history were collected by questionnaire. Body Mass Index (BMI) and aerobic fitness were calculated during testing in the first week of training. Movement screening was performed using the Landing Error Scoring System during week 1 and cadence was collected using an accelerometer worn throughout initial training. Kaplan-Meier survival curves estimated group differences in time to the first musculoskeletal injury during training. Cox regression was used to estimate hazard ratios (HRs) and Akaike Information Criterion (AIC) was used to compare model fit.

RESULTS

Cox modeling using HRs indicated that the following variables were associated with injury risk : Sex, history of injury, Landing Error Scoring System Score Category, and Physical Fitness Test (PT) Run Score. When controlling for sex and history of injury, amodel including aerobic fitness and BMI outperformed the model including movement screening risk and cadence (AIC: 1068.56 vs. 1074.11) and a model containing all variables that were significant in the univariable analysis was the most precise (AIC: 1063.68).

CONCLUSIONS

In addition to variables typically collected in this tactical setting (Injury History, BMI, and aerobic fitness), the inclusion of kinematic testing appears to enhance the precision of the risk identification model and will likely continue to be included in screening cadets at greater risk.

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.

Impact Magnitude and Symmetry in Females During Return to Sport Tasks Measured With Inertial Sensors

CONTEXT

Impact magnitude, such as peak tibial acceleration, may be associated with lower extremity injury risk and can be measured with an inertial sensor. An understanding of impact magnitude across functional tasks could guide clinicians in exercise prescription during rehabilitation of lower extremity injuries.

OBJECTIVES

To determine (1) differences in impact magnitude based on task and (2) which tasks have asymmetrical impact magnitude based on limb dominance.

DESIGN

Observational cohort design. Thirty-three healthy, recreationally active adult females participated in 1 testing session on a basketball court.

METHODS

Participants wore inertial sensors with embedded accelerometers on bilateral distal shanks. Participants completed 9 plyometric, speed, and agility tasks commonly utilized during the return to sport phase of lower extremity rehabilitation.

MAIN OUTCOME MEASURES

Average impact magnitude (peak tibial acceleration in multiples of gravity, g) for each limb for each task.

ANALYSES

We used a repeated-measures analysis of variance (factor: task) to determine the differences in impact magnitude based on task. We categorized tasks by magnitude of impact into low, medium, high, and very high impact. We utilized paired t tests for each task to compare limbs (dominant vs nondominant).

RESULTS

Impact magnitude differed based on task (P < .001). We classified tasks as low impact (≤10g; single-leg [SL] lateral jump, double-leg [DL] lateral jump); medium impact (11-20g; SL vertical jump, box drill); high impact (21-30g; modified T test, DL forward jump, SL forward jump); and very high impact (≥31g; sprint, DL tuck jump). Impact magnitude differed by limb in 3 tasks (DL forward jump, DL lateral jump, and box drill), with a higher impact on the dominant limb in each task.

CONCLUSIONS

Impact magnitude differed based on task. While most tasks had symmetric impact magnitude between limbs, 3 tasks had a higher impact magnitude on the dominant limb.

Preventing Osteoarthritis After an Anterior Cruciate Ligament Injury: An Osteoarthritis Action Alliance Consensus Statement

After an anterior cruciate ligament (ACL) injury, people need secondary prevention strategies to identify osteoarthritis at its earliest stages so that interventions can be implemented to halt or slow the progression toward its long-term burden. The Osteoarthritis Action Alliance formed an interdisciplinary Secondary Prevention Task Group to develop a consensus on recommendations to provide clinicians with secondary prevention strategies that are intended to reduce the risk of osteoarthritis after a person has an ACL injury. The group achieved consensus on 15 out of 16 recommendations that address patient education, exercise and rehabilitation, psychological skills training, graded-exposure therapy, cognitive-behavioral counseling (lacked consensus), outcomes to monitor, secondary injury prevention, system-level social support, leveraging technology, and coordinated care models. We hope this statement raises awareness among clinicians and researchers on the importance of taking steps to mitigate the risk of osteoarthritis after an ACL injury.

Evidence Review for Preventing Osteoarthritis After an Anterior Cruciate Ligament Injury: An Osteoarthritis Action Alliance Consensus Statement

CONTEXT

The Osteoarthritis Action Alliance formed a secondary prevention task group to develop a consensus on secondary prevention recommendations to reduce the risk of osteoarthritis after a knee injury.

OBJECTIVE

Our goal was to provide clinicians with secondary prevention recommendations that are intended to reduce the risk of osteoarthritis after a person has sustained an anterior cruciate ligament injury. Specifically, this manuscript describes our methods, literature reviews, and dissenting opinions to elaborate on the rationale for our recommendations and to identify critical gaps.

DESIGN

Consensus process.

SETTING

Virtual video conference calls and online voting.

PATIENTS OR OTHER PARTICIPANTS

The Secondary Prevention Task Group consisted of 29 members from various clinical backgrounds.

MAIN OUTCOME MEASURE(S)

The group initially convened online in August 2020 to discuss the target population, goals, and key topics. After a second call, the task group divided into 9 subgroups to draft the recommendations and supportive text for crucial content areas. Twenty-one members completed 2 rounds of voting and revising the recommendations and supportive text between February and April 2021. A virtual meeting was held to review the wording of the recommendations and obtain final votes. We defined consensus as >80% of voting members supporting a proposed recommendation.

RESULTS

The group achieved consensus on 15 of 16 recommendations. The recommendations address patient education, exercise and rehabilitation, psychological skills training, graded-exposure therapy, cognitive-behavioral counseling (lacked consensus), outcomes to monitor, secondary injury prevention, system-level social support, leveraging technology, and coordinated care models.

CONCLUSIONS

This consensus statement reflects information synthesized from an interdisciplinary group of experts based on the best available evidence from the literature or personal experience. We hope this document raises awareness among clinicians and researchers to take steps to mitigate the risk of osteoarthritis after an anterior cruciate ligament injury.

Mechanical and Sensorimotor Outcomes Associated With Talar Cartilage Deformation After Static Loading in Those With Chronic Ankle Instability

CONTEXT

Those with chronic ankle instability (CAI) demonstrate deleterious changes in talar cartilage composition, resulting in alterations of talar cartilage loading behavior. Common impairments associated with CAI may play a role in cartilage behavior in response to mechanical loading.

OBJECTIVE

To identify mechanical and sensorimotor outcomes that are linked with the magnitude of talar cartilage deformation after a static loading protocol in patients with and those without CAI.

DESIGN

Cross-sectional study.

SETTING

Laboratory setting.

PATIENTS OR OTHER PARTICIPANTS

Thirty individuals with CAI and 30 healthy individuals.

MAIN OUTCOME MEASURES(S)

After a 60-minute off-loading period, ultrasonographic images of the talar cartilage were acquired immediately before and after a 2-minute static loading protocol (single-legged stance). Talar cartilage images were obtained and manually segmented to enable calculation of medial, lateral, and overall average talar thickness. The percentage change, relative to the average baseline thickness, was used for further analysis. Mechanical (ankle joint laxity) and sensorimotor (static balance and Star Excursion Balance Test) outcomes were captured. Partial correlations were computed to determine associations between cartilage deformation magnitude and the mechanical and sensorimotor outcomes after accounting for body weight.

RESULTS

In the CAI group, greater inversion laxity was associated with greater overall (r = -0.42, P = .03) and medial (r = -0.48, P = .01) talar cartilage deformation after a 2-minute static loading protocol. Similarly, poorer medial-lateral static balance was linked with greater overall (r = 0.47, P = .01) and lateral (r = 0.50, P = .01) talar cartilage deformation. In the control group, shorter posterolateral Star Excursion Balance Test reach distance was associated with greater lateral cartilage deformation (r = 0.42, P = .03). No other significant associations were observed.

CONCLUSIONS

In those with CAI, inversion laxity and poor static postural control were moderately associated with greater talar cartilage deformation after a 2-minute static loading protocol. These results suggest that targeting mechanical instability and poor balance in those with CAI via intervention strategies may improve how the talar cartilage responds to static loading conditions.

Association of Traumatic Knee Injury With Radiographic Evidence of Knee Osteoarthritis in Military Officers

OBJECTIVE

The association between knee injury and knee osteoarthritis (OA) is understudied relative to its importance, particularly in younger populations. This study was undertaken to examine the association of knee injury with radiographic features of knee OA in military officers, who have a physically demanding profession and high rates of knee injury.

METHODS

Participants were recruited in 2015-2017 from an existing program that enrolled 6,452 military officers during 2004-2009. Officers with a history of knee ligament or meniscal injuries (n = 117 via medical record review) were compared to officers with no history of knee injury (n = 143). Bilateral posteroanterior knee radiographs were obtained using a standardized fixed-flexion positioning frame. All images were read for Kellgren/Lawrence (K/L) grade, osteophyte (OST), and joint space narrowing (JSN) scores. Data were analyzed using linear-risk regression models with generalized estimating equations.

RESULTS

Injured and noninjured participants were similar (mean age 28 years, mean body mass index 25 kg/m² , ~40% female). The mean time from first knee injury to imaging among injured participants was 9.2 years. Compared with noninjured knees, greater prevalence of radiographic OA (K/L grade ≥ 2), OST (grade ≥ 1), and JSN (grade ≥ 1) was observed among injured knees, with prevalence differences of +16% (95% confidence interval [95% CI] 10%, 22%), +29% (95% CI 20%, 38%), and + 17% (95% CI 10%, 24%), respectively. Approximately 1 in 6 officers with prior knee injury progressed to radiographic OA by age 30 years.

CONCLUSION

At the midpoint of a projected 20-year military career, officers with a history of traumatic knee injury have a markedly increased prevalence of knee radiographic OA compared to officers without injury.

Understanding Youth Sport Coaches' Perceptions of Evidence-Based Injury-Prevention Training Programs: A Systematic Literature Review

OBJECTIVE

To systematically review and summarize the knowledge, attitudes, beliefs, and contextual perceptions of youth sport coaches toward injury-prevention training programs by using the Theoretical Domains Framework to guide the organization of results.

DATA SOURCES

Systematic searches of PubMed and Google Scholar were undertaken in November 2021.

STUDY SELECTION

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol was followed. Results were limited to full-text articles that were published in peer-reviewed journals and printed in English. Additional studies were added after a citation search of included studies. Studies were eligible for inclusion if researchers evaluated youth sport coaches' knowledge, beliefs, contextual perceptions, or all 3 of anterior cruciate ligament injury-prevention training programs.

DATA EXTRACTION

Data charting was performed by 1 author and confirmed by a separate author.

DATA SYNTHESIS

Of the 1194 articles identified, 19 were included in the final sample. Among articles in which researchers assessed knowledge (n = 19), coaches' awareness of the existence and components of injury-prevention training programs was inconsistent. Among articles in which researchers assessed beliefs (n = 19), many coaches had positive attitudes toward injury-prevention training programs, but few believed youth athletes are at a high risk of injury. Among articles in which researchers assessed contextual perceptions (n = 13), many coaches did not feel they had access to information about injury-prevention training programs and cited a lack of time, space, support, and other resources as barriers to implementation.

CONCLUSIONS

Our findings support the need for programs, protocols, and policies to enhance knowledge of and support for youth sport coaches who wish to implement injury-prevention training programs. A gap exists in the research about addressing the needs of youth sport coaches in the United States high school sports setting. The use of multilevel implementation science frameworks (such as the Theoretical Domains Framework) will be beneficial for identifying constructs that affect implementation and developing train-the-trainer programming to meet the needs of individual youth sport coaches.

Association Between Head Impact Biomechanics and Physical Load in College Football

Head impacts and physical exertion are ubiquitous in American football, but the relationship between these factors is poorly understood across a competitive season or even within an individual session. Gameplay characteristics, including player position and session type, may contribute to these relationships but have not been prospectively examined. The current study aimed to determine if an association exists between head impact biomechanics and physical load metrics. We prospectively studied college football players during the 2017–2021 football seasons across representative playing positions (15 offensive and defensive linemen, 11 linebackers and tight ends, and 15 defensive backs, running backs, and receivers). Participants wore halters embedded with Catapult Vector GPS monitoring systems to quantify player load and participant helmets were equipped with the Head Impact Telemetry System to quantify head impact biomechanics and repetitive head impact exposure (RHIE). Generalized linear models and linear regression models were employed to analyze in-session and season-long outcomes, while addressing factors such as player position and session type on our data. Player load was associated with RHIE (p < 0.001). Season-long player load predicted season-long RHIE (R² = 0.31; p < 0.001). Position group affected in-session player load (p = 0.025). Both player load and RHIE were greater in games than in practices (p < 0.001), and position group did not affect RHIE (p = 0.343). Physical load burden was associated with RHIE within sessions and across an entire season. Session type affected both RHIE and player load, while position group only affected player load. Our data point to tracking physical load burden as a potential proxy for monitoring anticipated RHIE during the season.

Dorsiflexion and Hop Biomechanics Associate with Greater Talar Cartilage Deformation in Those with Chronic Ankle Instability

PURPOSE

This study aimed to identify associations between dorsiflexion range of motion (DFROM), functional hop test performance, and hopping biomechanics with the magnitude of talar cartilage deformation after a standardized hopping protocol in individuals with and without chronic ankle instability (CAI).

METHODS

Thirty CAI and 30 healthy individuals participated. Ankle DFROM was assessed using the weight-bearing lunge test. Four different functional hop tests were assessed. Three-dimensional kinematics and kinetics were sampled during a 60-cm single-leg hop. We calculated cartilage deformation after a dynamic loading protocol consisting of sixty 60-cm single-leg forward hops by assessing the change in average thickness for the overall, medial, and lateral talar cartilage. Linear regressions examined the associations between cartilage deformation magnitude and DFROM, functional hop tests, and hop biomechanical variables after accounting for body weight and time since the initial ankle sprain.

RESULTS

In CAI group, lesser static DFROM (ΔR2 = 0.22) and smaller peak ankle dorsiflexion angle (ΔR2 = 0.17) was associated with greater medial deformation. Greater peak vertical ground reaction force (vGRF) (ΔR2 = 0.26-0.28) was associated with greater medial and overall deformation. Greater vGRF loading rate (ΔR2 = 0.23-0.35) was associated with greater lateral and overall deformation. Greater side hop test times (ΔR2 = 0.31-0.36) and ankle plantarflexion at initial contact (ΔR2 = 0.23-0.38) were associated with greater medial, lateral, and overall deformation. In the control group, lesser side hop test times (ΔR2 = 0.14), greater crossover hop distances (ΔR2 = 0.14), and greater single-hop distances (ΔR2 = 0.21) were associated with greater overall deformation.

CONCLUSIONS

Our results indicate that lesser static DFROM, poorer functional hop test performance, and hop biomechanics associate with greater talar cartilage deformation after a dynamic loading protocol in those with CAI. These factors may represent targets for therapeutic interventions within this population to slow ankle posttraumatic osteoarthritis progression.

Association Between Landing Error Scoring System (LESS) Items and the Incidence Rate of Lower Extremity Stress Fracture

Background:

Lower extremity stress fracture injuries are a major cause of morbidity in physically active populations. The ability to screen for modifiable risk factors associated with injury is critical in developing injury-prevention programs.

Purpose:

To determine if baseline Landing Error Scoring System (LESS) scores are associated with the incidence rate of lower extremity stress fracture.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A total of 1772 participants with no history of lower extremity stress fracture were included. At preinjury baseline, the authors conducted a lower extremity movement assessment during a jump-landing task using the LESS. Incident lower extremity stress fractures were identified during a 4-year follow-up period. Potential incident cases were reviewed by 2 sports medicine fellowship–trained orthopaedic surgeons blinded to baseline LESS data. Univariate and multivariable Poisson regression models were used to estimate the association between baseline total LESS scores, individual LESS items, and the incidence rate ratio (IRR) of lower extremity stress fracture.

Results:

A total of 94 incident lower extremity stress fractures were documented, for a 5.3% (95% CI, 4.3%-6.5%) cumulative incidence. The overall LESS score was associated with the incidence rate of lower extremity stress fracture. For every additional movement error documented at baseline, there was a 15% increase in the incidence rate of lower extremity stress fracture (IRR, 1.15 [95% CI, 1.02-1.31]; P = .025). In univariate analyses, ankle flexion, stance width, asymmetrical landing, and trunk flexion at initial contact, in addition to overall impression, were associated with the incidence rate of stress fracture. After controlling for sex and year of entry into the study cohort, participants who consistently landed flat-footed or heel-to-toe were 2.33 times (95% CI, 1.36-3.97; P = .002) more likely to sustain a lower extremity stress fracture. Similarly, participants who consistently demonstrated asymmetric landing at initial contact were 2.53 times (95% CI, 1.34-4.74; P = .004) more likely to sustain a stress fracture.

Conclusion:

Components of the LESS may be associated with increased lower extremity stress fracture risk and may be helpful in efficiently assessing high-risk lower extremity biomechanics in large groups.

Are Elite Collegiate Female Athletes PRIME for a Safe Return to Sport after ACLR? An Investigation of Physical Readiness and Integrated Movement Efficiency (PRIME)

Background

Elite female athletes who successfully return to sport after anterior cruciate ligament reconstruction (ACLR) represent a high-risk group for secondary injury. Little is known about how the functional profile of these athletes compares to their teammates who have not sustained ACL injuries.

Purpose

To compare elite collegiate female athletes who were able to successfully return to sport for at least one season following ACLR to their teammates with no history of ACLR with regard to self-reported knee function, kinetics, and kinematics during a double limb jump-landing task.

Study Design

Cross-Sectional Study.

Level of Evidence

Level 3.

Methods

Eighty-two female collegiate athletes (17 ACLR, 65 control) completed the knee-specific SANE (single assessment numeric evaluation) and three trials of a jump-landing task prior to their competitive season. vGRF data on each limb and the LESS (Landing Error Scoring System) score were collected from the jump-landing task. Knee-SANE, vGRF data, and LESS scores were compared between groups. All athletes were monitored for the duration of their competitive season for ACL injuries.

Results

Athletes after ACLR reported worse knee-specific function. Based on vGRF data, they unloaded their involved limb during the impact phase of the landing, and they were more asymmetrical between limbs during the propulsion phase as compared to the control group. The ACLR group, however, had lower LESS scores, indicative of better movement quality. No athletes in either group sustained ACL injuries during the following season.

Conclusion

Despite reporting worse knee function and demonstrating worse kinetics, the ACLR group demonstrated better movement quality relative to their uninjured teammates. This functional profile may correspond to short-term successful outcomes following ACLR, given that no athletes sustained ACL injuries in the competition season following assessment.

Think outside the box: Incorporating secondary cognitive tasks into return to sport testing after ACL reconstruction

The optimal set of return to sport (RTS) tests after anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) remains elusive. Many athletes fail to pass current RTS test batteries, fail to RTS, or sustain secondary ACL injuries if they do RTS. The purpose of this review is to summarize current literature regarding functional RTS testing after ACLR and to encourage clinicians to have patients "think" (add a secondary cognitive task) outside the "box" (in reference to the box used during the drop vertical jump task) when performing functional RTS tests. We review important criteria for functional tests in RTS testing, including task-specificity and measurability. Firstly, tests should replicate the sport-specific demands the athlete will encounter when they RTS. Many ACL injuries occur when the athlete is performing a dual cognitive-motor task (e.g., attending to an opponent while performing a cutting maneuver). However, most functional RTS tests do not incorporate a secondary cognitive load. Secondly, tests should be measurable, both through the athlete's ability to complete the task safely (through biomechanical analyses) and efficiently (through measures of performance). We highlight and critically examine three examples of functional tests that are commonly used for RTS testing: the drop vertical jump, single-leg hop tests, and cutting tasks. We discuss how biomechanics and performance can be measured during these tasks, including the relationship these variables may have with injury. We then discuss how cognitive demands can be added to these tasks, and how these demands influence both biomechanics and performance. Lastly, we provide clinicians with practical recommendations on how to implement secondary cognitive tasks into functional testing and how to assess athletes' biomechanics and performance.

Lower Extremity Musculoskeletal Injury in US Military Academy Cadet Basic Training: A Survival Analysis Evaluating Sex, History of Injury, and Body Mass Index

Background

Injury incidence for physically active populations with a high volume of physical load can exceed 79%. There is little existing research focused on timing of injury and how that timing differs based on certain risk factors.

Purpose/Hypothesis

The purpose of this study was to report both the incidence and timing of lower extremity injuries during cadet basic training. We hypothesized that women, those with a history of injury, and those in underweight and obese body mass index (BMI) categories would sustain lower extremity musculoskeletal injury earlier in the training period than men, those without injury history, and those in the normal-weight BMI category.

Study Design

Cohort study; Level of evidence, 2.

Methods

Cadets from the class of 2022, arriving in 2018, served as the study population. Baseline information on sex and injury history was collected via questionnaire, and BMI was calculated from height and weight taken during week 1 at the United States Military Academy. Categories were underweight (BMI <20), middleweight (20-29.99), and obese (≥30). Injury surveillance was performed over the first 60 days of training via electronic medical record review and monitoring. Kaplan-Meier survival curves were used to estimate group differences in time to the first musculoskeletal injury. Cox proportional hazard regression was used to estimate hazard ratios (HRs).

Results

A total of 595 cadets participated. The cohort was 76.8% male, with 29.9% reporting previous injury history and 93.3% having a BMI between 20 and 30. Overall, 16.3% of cadets (12.3% of male cadets and 29.7% of female cadets) experienced an injury during the follow-up period. Women experienced significantly greater incident injury than did men (P < .001). Separation of survival curves comparing the sexes and injury history occurred at weeks 3 and 4, respectively. Hazards for first musculoskeletal injury were significantly greater for women versus men (HR, 2.63; 95% CI, 1.76-3.94) and for those who reported a history of injury versus no injury history (HR, 1.76; 95% CI, 1.18-2.64). No differences were observed between BMI categories.

Conclusion

Female cadets and those reporting previous musculoskeletal injury demonstrated a greater hazard of musculoskeletal injury during cadet basic training. This study did not observe an association between BMI and injury.

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.

Association Between Automated Landing Error Scoring System Performance and Bone Stress Injury Risk in Military Trainees

CONTEXT

Lower extremity bone stress injuries (BSI) place a significant burden on the health and readiness of the US Armed Forces.

OBJECTIVE

To determine if pre-injury baseline performance on an expanded and automated 22-item version of the Landing Error Scoring System (LESS-22) is associated with the incidence of BSI in a military training population.

DESIGN

Prospective cohort study.

SETTING

US Military Academy at West Point Participants: 2,235 (510 females, 22.8%) incoming cadets Main outcome measures: Multivariable Poisson regression models were used to produce adjusted incidence rate ratios (IRR) to quantify the association between pre-injury LESS scores and BSI incidence rate during follow-up, adjusted for pertinent risk factors. Risk factors were included as covariates in the final model if the 95% confidence interval (95% CI) for the crude IRR did not contain 1.00.

RESULTS

A total of 54 BSI occurred during the study period, resulting in an overall incidence rate of 0.07 BSI per 1,000 person-days (95% CI: 0.05, 0.09). The mean number of exposure days was 345.4 (SD 61.12, range 3-368). The final model was adjusted for sex and BMI and yielded an adjusted IRR for LESS-22 score of 1.06 (95% CI: 1.002, 1.13; p=0.04), 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, six individual LESS-22 items, including two newly added items, were significantly associated with BSI incidence.

CONCLUSIONS

This study provides evidence that performance on the expanded and automated version of the LESS is associated with BSI incidence in a military training population. These results suggest that the automated LESS-22 may be a scalable solution for screening military training populations for BSI risk.

Combining Inertial Sensors and Machine Learning to Predict vGRF and Knee Biomechanics during a Double Limb Jump Landing Task

(1) Background: Biomechanics during landing tasks, such as the kinematics and kinetics of the knee, are altered following anterior cruciate ligament (ACL) injury and reconstruction. These variables are recommended to assess prior to clearance for return to sport, but clinicians lack access to the current gold-standard laboratory-based assessment. Inertial sensors serve as a potential solution to provide a clinically feasible means to assess biomechanics and augment the return to sport testing. The purposes of this study were to (a) develop multi-sensor machine learning algorithms for predicting biomechanics and (b) quantify the accuracy of each algorithm. (2) Methods: 26 healthy young adults completed 8 trials of a double limb jump landing task. Peak vertical ground reaction force, peak knee flexion angle, peak knee extension moment, and peak sagittal knee power absorption were assessed using 3D motion capture and force plates. Shank- and thigh- mounted inertial sensors were used to collect data concurrently. Inertial data were submitted as inputs to single- and multiple- feature linear regressions to predict biomechanical variables in each limb. (3) Results: Multiple-feature models, particularly when an accelerometer and gyroscope were used together, were valid predictors of biomechanics (R² = 0.68–0.94, normalized root mean square error = 4.6–10.2%). Single-feature models had decreased performance (R² = 0.16–0.60, normalized root mean square error = 10.0–16.2%). (4) Conclusions: The combination of inertial sensors and machine learning provides a valid prediction of biomechanics during a double limb landing task. This is a feasible solution to assess biomechanics for both clinical and real-world settings outside the traditional biomechanics laboratory.

Acute Talar Cartilage Deformation in Those with and without Chronic Ankle Instability

PURPOSE

This study aimed 1) to determine whether talar cartilage deformation measured via ultrasonography (US) after standing and hopping loading protocols differs between chronic ankle instability (CAI) patients and healthy controls and 2) to determine whether the US measurement of cartilage deformation reflects viscoelasticity between standing and hopping protocols.

METHODS

A total of 30 CAI and 30 controls participated. After a 60-min off-loading period, US images of the talar cartilage were acquired before and after static (2-min single-leg standing) and dynamic (60 single-leg forward hops) loading conditions. We calculated cartilage deformation by assessing the change in average thickness (mm) for overall, medial, and lateral talar cartilage. The independent variables include time (Pre60 and postloading), condition (standing and dynamic loading), and group (CAI and control). A three-way mixed-model repeated-measures ANCOVA and appropriate post hoc tests were used to compare cartilage deformation between the groups after static and dynamic loading.

RESULTS

After the static loading condition, those with CAI had greater talar cartilage deformation compared with healthy individuals for overall (-10.87% vs -6.84%, P = 0.032) and medial (-12.98% vs -5.80%, P = 0.006) talar cartilage. Similarly, the CAI group had greater deformation relative to the control group for overall (-8.59% vs -3.46%, P = 0.038) and medial (-8.51% vs -3.31%, P = 0.043) talar cartilage after the dynamic loading condition. In the combined cohort, cartilage deformation was greater after static loading compared with dynamic in overall (-8.85% vs -6.03%, P = 0.003), medial (-9.38% vs -5.91%, P = 0.043), and lateral (-7.90% vs -5.65%, P = 0.009) cartilage.

CONCLUSION

US is capable of detecting differences in cartilage deformation between those with CAI and uninjured controls after standardized physiologic loads. Across both groups, our results demonstrate that static loading results in greater cartilage deformation compared with dynamic loading.

Vibration improves gait biomechanics linked to posttraumatic knee osteoarthritis following anterior cruciate ligament injury

Anterior cruciate ligament reconstruction (ACLR) incurs a high risk of posttraumatic knee osteoarthritis (PTOA). Aberrant gait biomechanics contribute to PTOA and are attributable in part to quadriceps dysfunction. Vibration improves quadriceps function following ACLR, but its effects on gait biomechanics are unknown. The purpose of this study was to evaluate the effects of whole-body vibration (WBV) and local muscle vibration (LMV) on gait biomechanics in individuals with ACLR. Seventy-five volunteers (time since ACLR 27 ± 16 months) were randomized to WBV, LMV, or Control interventions. Walking biomechanics were assessed prior to and following a single exposure to the interventions. Outcomes included pre-post change scores in the ACLR limb for the peak vertical ground reaction force (vGRF) and its loading rate, peak internal knee extension (KEM) and abduction moments, and peak knee flexion and varus angles. LMV produced a significant decrease in the vGRF loading rate (-3.6 BW/s) that was greater than the changes in the WBV (-0.3 BW/s) and Control (0.5 BW/s) groups. Additionally, WBV produced an increase in the peak KEM (0.27% BW × Ht) that was greater than the change in the Control group (-0.17% BW × Ht) but not the LMV group (0.01% BW × Ht). Lower KEM and greater loading rates have been linked to declines in joint health following ACLR. WBV acutely increased the peak KEM and LMV decreased loading rates. These data suggest that vibration has the potential to mitigate aberrant gait biomechanics, and may represent an effective approach for reducing PTOA risk following ACLR.

Differences in Biomechanical Loading Magnitude During a Landing Task in Male Athletes with and without Patellar Tendinopathy

CONTEXT

Prior research has not established if overloading or underloading movement profiles are present in symptomatic and asymptomatic athletes with patellar tendon structural abnormality (PTA) compared to healthy athletes.

OBJECTIVE

The purpose was to compare involved limb landing biomechanics between male athletes with and without patellar tendinopathy.

DESIGN

Cross-sectional study Setting: Laboratory Patients or Other Participants: 43 males were grouped based on patellar tendon pain & ultrasound imaging of the proximal patellar tendon: symptomatic with PTA (SYM-PTA; n=13; 20±2yrs; 1.8±0.1m; 84±5kg), asymptomatic with PTA (ASYM-PTA; n=15; 21±2yrs; 1.8±0.1m; 82±13kg), and healthy control (CON; n=15; 20±2yrs; 1.8±0.1m; 79±12kg).

MAIN OUTCOME MEASURES

3D biomechanics were collected during double-limb jump-landing. Kinematic (knee flexion angle (KF)) and kinetic (vertical ground reaction force (VGRF); internal knee extension moment (KEM); patellar tendon force (FPT)) variables were analyzed as continuous waveforms during the stance phase for the involved limb. Mean values were calculated for each 1% of stance, normalized over 202 data points (0-100%), and plotted with 95% confidence intervals. Statistical significance was defined as a lack of 95% CI overlap for ≥ 6 consecutive data points.

RESULTS

SYM-PTA had lesser KF than CON throughout the stance phase. ASYM-PTA had lesser KF than CON in the early and late stance phase. SYM-PTA group had lesser KEM and FPT than CON in early stance, as well as ASYM-PTA in mid-stance.

CONCLUSIONS

Male athletes with SYM-PTA demonstrated a patellar tendon load-avoidance profile compared to ASYM-PTA and CON athletes. ASYM-PTA did not show evidence of overloading compared to CON. Our findings support the need for individualized treatments for athletes with tendinopathy to maximize load-capacity.

TRIAL REGISTRY

ClinicalTrials.gov (#XXX).

Differences in Lower Extremity Movement Quality by Level of Sport Specialization in Cadets Entering a United States Service Academy

BACKGROUND

Sport specialization in youth athletes is associated with increased risk for musculoskeletal injury; however, little is known about whether sport specialization is associated with lower extremity movement quality. The purpose of this study was to examine differences in lower extremity movement quality by level of sport specialization in US Service Academy cadets.

HYPOTHESIS

Cadets who report an increased level of sport specialization would have a lower level of movement quality than those who are less specialized.

STUDY DESIGN

Cross-sectional analysis from an ongoing prospective cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Cadets completed the Landing Error Scoring System (LESS) and a baseline questionnaire evaluating level of sport specialization during high school. Data were analyzed using separate 1-way analysis of variance models.

RESULTS

Among all participants (n = 1950), 1045 (53.6%) reported low sport specialization, 600 (30.8%) reported moderate sport specialization, and 305 (15.6%) reported high sport specialization at the time of data collection during the first week. Ages ranged from 17 to 23 years. Men (1491) and women (459) reported comparable specialization levels (P = 0.45). There were no statistically significant differences in lower extremity movement quality by level of specialization for all subjects combined (P = 0.15) or when only men were included in the analyses (P = 0.69). However, there were statistically significant differences in movement quality by level of specialization in women (P = 0.02). Moderately specialized women had the best movement quality (mean, 4.63; SD, 2.21) followed by those with high specialization (mean, 4.90; SD, 2.08) and those with low levels of specialization (mean, 5.23; SD, 2.07).

CONCLUSION

Women reporting moderate sport specialization had improved movement quality and significantly better LESS scores compared to those with high/low specialization.

CLINICAL RELEVANCE

Athletes, especially women, should be encouraged to avoid early sport specialization to optimize movement quality, which may affect injury risk.

Influence of Baseball Training Load on Clinical Reach Tests and Grip Strength in Collegiate Baseball Players

CONTEXT

A baseball-specific training load may influence strength or glenohumeral range of motion, which are related to baseball injuries. Glenohumeral reach tests and grip strength are clinical assessments of shoulder range of motion and upper extremity strength, respectively.

OBJECTIVE

To examine changes in glenohumeral reach test performance and grip strength between dominant and nondominant limbs and high, moderate, and low baseball-specific training-load groups.

DESIGN

Repeated-measures study.

SETTING

University laboratory and satellite clinic.

PATIENTS OR OTHER PARTICIPANTS

Collegiate baseball athletes (n = 18, age = 20.1 ± 1.3 years, height = 185.0 ± 6.5 cm, mass = 90.9 ± 10.2 kg).

MAIN OUTCOME MEASURE(S)

Participants performed overhead reach tests (OHRTs), behind-the-back reach tests (BBRTs), and grip strength assessments using the dominant and nondominant limbs every 4 weeks for 16 weeks. Percentage change scores were calculated between testing times. After each training session, participants provided their duration of baseball activity, throw count, and body-specific and arm-specific ratings of perceived exertion. We classified them in the high, moderate, or low training-load group based on each training-load variable: body-specific acute:chronic workload ratio (ACWR), arm-specific ACWR, body-specific cumulative load, and arm-specific cumulative load. Mixed models were used to compare training-load groups and limbs.

RESULTS

The arm-specific ACWR group demonstrated as main effect for OHRT (F = 7.70, P = .001), BBRT (F = 4.01, P = .029), and grip strength (F = 8.89, P < .001). For the OHRT, the moderate training-load group demonstrated a 10.8% greater increase than the high group (P = .004) and a 13.2% greater increase than the low group (P < .001). For the BBRT, the low training-load group had a 10.1% greater increase than the moderate group (P = .011). For grip strength, the low training-load group demonstrated a 12.1% greater increase than the high group (P = .006) and a 17.7% greater increase than the moderate group (P < .001).

CONCLUSIONS

Arm-specific ACWR was related to changes in clinical assessments of range of motion and strength. Clinicians may use arm-specific ACWR to indicate when a baseball athlete's physical health is changing.

Validation of a Commercially Available Markerless Motion-Capture System for Trunk and Lower Extremity Kinematics During a Jump-Landing Assessment

CONTEXT

Field-based, portable motion-capture systems can be used to help identify individuals at greater risk of lower extremity injury. Microsoft Kinect-based markerless motion-capture systems meet these requirements; however, until recently, these systems were generally not automated, required substantial data postprocessing, and were not commercially available.

OBJECTIVE

To validate the kinematic measures of a commercially available markerless motion-capture system.

DESIGN

Descriptive laboratory study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 20 healthy, physically active university students (10 males, 10 females; age = 20.50 ± 2.78 years, height = 170.36 ± 9.82 cm, mass = 68.38 ± 10.07 kg, body mass index = 23.50 ± 2.40 kg/m2).

INTERVENTION(S)

Participants completed 5 jump-landing trials. Kinematic data were simultaneously recorded using Kinect-based markerless and stereophotogrammetric motion-capture systems.

MAIN OUTCOME MEASURE(S)

Sagittal- and frontal-plane trunk, hip-joint, and knee-joint angles were identified at initial ground contact of the jump landing (IC), for the maximum joint angle during the landing phase of the initial landing (MAX), and for the joint-angle displacement from IC to MAX (DSP). Outliers were removed, and data were averaged across trials. We used intraclass correlation coefficients (ICCs [2,1]) to assess intersystem reliability and the paired-samples t test to examine mean differences (α ≤ .05).

RESULTS

Agreement existed between the systems (ICC range = -1.52 to 0.96; ICC average = 0.58), with 75.00% (n = 24/32) of the measures being validated (P ≤ .05). Agreement was better for sagittal- (ICC average = 0.84) than frontal- (ICC average = 0.35) plane measures. Agreement was best for MAX (ICC average = 0.77) compared with IC (ICC average = 0.56) and DSP (ICC average = 0.41) measures. Pairwise comparisons identified differences for 18.75% (6/32) of the measures. Fewer differences were observed for sagittal- (0.00%; 0/15) than for frontal- (35.29%; 6/17) plane measures. Between-systems differences were equivalent for MAX (18.18%; 2/11), DSP (18.18%; 2/11), and IC (20.00%; 2/10) measures. The markerless system underestimated sagittal-plane measures (86.67%; 13/15) and overestimated frontal-plane measures (76.47%; 13/17). No trends were observed for overestimating or underestimating IC, MAX, or DSP measures.

CONCLUSIONS

Moderate agreement existed between markerless and stereophotogrammetric motion-capture systems. Better agreement existed for larger (eg, sagittal-plane, MAX) than for smaller (eg, frontal-plane, IC) joint angles. The DSP angles had the worst agreement. Markerless motion-capture systems may help clinicians identify individuals at greater risk of lower extremity injury.

Gender-Specific Risk Factor Profiles for Patellofemoral Pain

OBJECTIVE

To determine the association between selected biomechanical variables and risk of patellofemoral pain (PFP) in males and females.

DESIGN

Prospective cohort.

SETTING

US Service Academies.

PARTICIPANTS

Four thousand five hundred forty-three cadets (1727 females and 2816 males).

ASSESSMENT OF RISK FACTORS

Three-dimensional biomechanics during a jump-landing task, lower-extremity strength, Q-angle, and navicular drop.

MAIN OUTCOME MEASURES

Cadets were monitored for diagnosis of PFP during their enrollment in a service academy. Three-dimensional hip and knee kinematic data were determined at initial contact (IC) and at 50% of the stance phase of the jump-landing task. Logistic regression analyses were performed for each risk factor variable in males and females (P < 0.05).

RESULTS

Less than 10 degrees of hip abduction at IC [odds ratio (OR) = 1.86, P = 0.03] and greater than 10 degrees of knee internal rotation at 50% of the stance phase (OR = 1.71, P = 0.02) increased the risk of PFP in females. Greater than 20 degrees of knee flexion at IC (OR = 0.47, P < 0.01) and between 0 and 5 degrees of hip external rotation at 50% of the stance phase (OR = 0.52, P = 0.04) decreased the risk of PFP in males. No other variables were associated with risk of developing PFP (P > 0.05).

CONCLUSIONS

The results suggest males and females have differing kinematic risk factor profiles for the development of PFP.

CLINICAL RELEVANCE

To most effectively reduce the risk of developing PFP, the risk factor variables specific to males (decreased knee flexion and increased hip external rotation) and females (decreased hip abduction and increased knee internal rotation) should be addressed in injury prevention programs.

Use of double leg injury screening to assess single leg biomechanical risk variables

OBJECTIVES

The purpose of this article was to determine if differences in kinematic and kinetic variables observed in a double-leg screen carried over to a single-leg task.

DESIGN

We used a case-control design with grouping based on performance during a double-leg jump landing.

SETTING

All participants were selected from a large university setting and testing was performed in a biomechanics laboratory.

PARTICIPANTS

Participants were females between 18 and 25 years of age with at least high school varsity experience in one or more of the following sports: soccer, lacrosse, field hockey, rugby, basketball, or team handball.

MAIN OUTCOME MEASURES

Primary outcome measures were knee angles in the frontal and sagittal planes as well as vertical ground reaction force (vGRF).

RESULTS

There were significant between group differences in peak knee flexion and knee flexion displacement during both the double and single-leg tasks, however between group differences for peak knee valgus and knee valgus displacement noted in the double-leg task were not observed in the single-leg task. vGRF was significantly different in the single-leg task but not the double-leg task.

CONCLUSION

A double leg screening may not provide complete identification of risk of injury during sports requiring single leg tasks.

Immediate Biochemical Changes After Gait Biofeedback in Individuals With Anterior Cruciate Ligament Reconstruction

CONTEXT

Gait biomechanics are linked to biochemical changes that contribute to the development of posttraumatic knee osteoarthritis in individuals with anterior cruciate ligament reconstruction (ACLR). It remains unknown if modifying peak loading during gait using real-time biofeedback will result in acute biochemical changes related to cartilage metabolism.

OBJECTIVE

To determine if acutely manipulating peak vertical ground reaction force (vGRF) during gait influences acute changes in serum cartilage oligomeric matrix protein concentration (sCOMP) among individuals with ACLR.

DESIGN

Crossover study.

PATIENTS OR OTHER PARTICIPANTS

Thirty individuals with unilateral ACLR participated (70% female, age = 20.43 ± 2.91 years old, body mass index = 24.42 ± 4.25, months post-ACLR = 47.83 ± 26.97). Additionally, we identified a subgroup of participants who demonstrated an increase in sCOMP after the control or natural loading condition (sCOMPCHANGE > 0 ng/mL, n = 22, 70% female, age = 20.32 ± 3.00 years old, body mass index = 24.73 ± 4.33, months post-ACLR = 47.27 ± 29.32).

MAIN OUTCOME MEASURE(S)

Serum was collected both prior to and immediately after each condition to determine sCOMPchange.

INTERVENTION(S)

All participants attended 4 sessions that involved 20 minutes of walking on a force-measuring treadmill consisting of a control condition (natural loading) followed by random ordering of 3 loading conditions with real-time biofeedback: (1) symmetric vGRF between limbs, (2) a 5% increase in vGRF (high loading) and (3) a 5% decrease in vGRF (low loading). A general linear mixed model was used to determine differences in sCOMPCHANGE between altered loading conditions and the control group in the entire cohort and the subgroup.

RESULTS

The sCOMPCHANGE was not different across loading conditions for the entire cohort (F3,29 = 1.34, P = .282). Within the subgroup, sCOMPCHANGE was less during high loading (1.95 ± 24.22 ng/mL, t21 = -3.53, P = .005) and symmetric loading (9.93 ± 21.45 ng/mL, t21 = -2.86, P = .025) compared with the control condition (25.79 ± 21.40 ng/mL).

CONCLUSIONS

Increasing peak vGRF during gait decreased sCOMP in individuals with ACLR who naturally demonstrated an increase in sCOMP after 20 minutes of walking.

TRIAL REGISTRY

ClinicalTrials.gov (NCT03035994).

Landing biomechanics are not immediately altered by a single-dose patellar tendon isometric exercise protocol in male athletes with patellar tendinopathy: A single-blinded randomized cross-over trial

OBJECTIVES

To a) determine the acute effects of a single-dose patellar tendon isometric exercise protocol on involved limb landing biomechanics in individuals with patellar tendinopathy and asymptomatic patellar tendon pathology, and b) determine if individuals with patellar tendinopathy demonstrated changes in pain following a single-dose patellar tendon isometric exercise protocol.

DESIGN

Single-blinded randomized cross-over trial.

SETTING

Laboratory; PARTICIPANTS: 28 young male athletes with symptomatic (n = 13, age: 19.62 ± 1.61) and asymptomatic (n = 15, age: 21.13 ± 1.88) patellar tendinopathy.

MAIN OUTCOME MEASURES

Participants completed a single-dose patellar tendon isometric exercise protocol and a sham-TENS protocol, randomized and separated by 7-10 days. Pain-levels during a single-limb decline squat (SLDS) and three-dimensional biomechanics were collected during a double-limb jump-landing task before and after each intervention protocol. A mixed-model repeated measures ANOVA was conducted to compare change scores for all dependent variables.

RESULTS

There were no group × intervention interactions for change in pain (F_{(1, 26)} = 0.555, p = 0.463). There was one significant group × intervention interaction for vertical ground reaction force (VGRF) (F_{(1, 26)} = 5.33, p = 0.029). However, post-hoc testing with Bonferroni correction demonstrated no statistical significance for group (SYM: t = -1.679, p = 0.119; ASYM: t = -1.7, p = 0.107) or intervention condition (isometric: t = -2.58, p = 0.016; sham-TENS: 0.72, p = 0.460). There were no further significant group × intervention interactions (p > 0.05).

CONCLUSIONS

A single-dose patellar tendon isometric exercise protocol did not have acute effects on landing biomechanics or pain levels in male athletes with patellar tendinopathy or asymptomatic patellar tendon pathology.

Trunk and Lower Extremity Movement Patterns, Stress Fracture Risk Factors, and Biomarkers of Bone Turnover in Military Trainees

CONTEXT

Military service members commonly sustain lower extremity stress fractures (SFx). How SFx risk factors influence bone metabolism is unknown. Understanding how SFx risk factors influence bone metabolism may help to optimize risk-mitigation strategies.

OBJECTIVE

To determine how SFx risk factors influence bone metabolism.

DESIGN

Cross-sectional study.

SETTING

Military service academy.

PATIENTS OR OTHER PARTICIPANTS

Forty-five men (agepre = 18.56 ± 1.39 years, heightpre = 176.95 ± 7.29 cm, masspre = 77.20 ± 9.40 kg; body mass indexpre = 24.68 ± 2.87) who completed Cadet Basic Training (CBT). Individuals with neurologic or metabolic disorders were excluded.

INTERVENTION(S)

We assessed SFx risk factors (independent variables) with (1) the Landing Error Scoring System (LESS), (2) self-reported injury and physical activity questionnaires, and (3) physical fitness tests. We assessed bone biomarkers (dependent variables; procollagen type I amino-terminal propeptide [PINP] and cross-linked collagen telopeptide [CTx-1]) via serum.

MAIN OUTCOME MEASURE(S)

A markerless motion-capture system was used to analyze trunk and lower extremity biomechanics via the LESS. Serum samples were collected post-CBT; enzyme-linked immunosorbent assays determined PINP and CTx-1 concentrations, and PINP : CTx-1 ratios were calculated. Linear regression models demonstrated associations between SFx risk factors and PINP and CTx-1 concentrations and PINP : CTx-1 ratio. Biomarker concentration mean differences with 95% confidence intervals were calculated. Significance was set a priori using α ≤ .10 for simple and α ≤ .05 for multiple regression analyses.

RESULTS

The multiple regression models incorporating LESS and SFx risk factor data predicted the PINP concentration (R2 = 0.47, P = .02) and PINP : CTx-1 ratio (R2 = 0.66, P = .01). The PINP concentration was increased by foot internal rotation, trunk flexion, CBT injury, sit-up score, and pre- to post-CBT mass changes. The CTx-1 concentration was increased by heel-to-toe landing and post-CBT mass. The PINP : CTx-1 ratio was increased by foot internal rotation, lower extremity sagittal-plane displacement (inversely), CBT injury, sit-up score, and pre- to post-CBT mass changes.

CONCLUSIONS

Stress fracture risk factors accounted for 66% of the PINP : CTx-1 ratio variability, a potential surrogate for bone health. Our findings provide insight into how SFx risk factors influence bone health. This information can help guide SFx risk-mitigation strategies.

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).

Biomechanical effects of manipulating peak vertical ground reaction force throughout gait in individuals 6-12 months after anterior cruciate ligament reconstruction

BACKGROUND

We aimed to determine the effect of cueing an increase or decrease in the vertical ground reaction force impact peak (peak in the first 50% of stance) on vertical ground reaction force, knee flexion angle, internal knee extension moment, and internal knee abduction moment waveforms throughout stance in individuals 6-12 months after an anterior cruciate ligament reconstruction.

METHODS

Twelve individuals completed 3 conditions (High, Low, and Control) where High and Low Conditions cue a 5% body weight increase or decrease, respectively, in the vertical ground reaction force impact peak compared to usual walking. Biomechanics during High and Low Conditions were compared to the Control Condition throughout stance.

FINDINGS

The High Condition resulted in: (a) increased vertical ground reaction forces at each peak and decreased during mid-stance, (b) greater knee excursion (i.e., greater knee flexion angle in early stance and a more extended knee in late stance), (c) greater internal extension moment for the majority of stance, and (d) lesser second internal knee abduction moment peak. The Low Condition resulted in: (a) vertical ground reaction forces decreased during early stance and increased during mid-stance, (b) decreased knee excursion, (c) increased internal extension moment throughout stance, and (d) decreased internal knee abduction moment peaks.

INTERPRETATION

Cueing a 5% body weight increase in vertical ground reaction force impact peak resulted in a more dynamic vertical ground reaction force loading pattern, increased knee excursion, and a greater internal extension moment during stance which may be useful in restoring gait patterns following anterior cruciate ligament reconstruction.

Using TENS to Enhance Therapeutic Exercise in Individuals with Knee Osteoarthritis

Transcutaneous electrical nerve stimulation (TENS) facilitates quadriceps voluntary activation in experimental settings. Augmenting therapeutic exercise (TE) with TENS may enhance the benefits of TE in individuals with knee osteoarthritis (KOA) and quadriceps voluntary activation failure (QVAF).

PURPOSE

This study aimed to determine the effect of TENS + TE on patient-reported function, quadriceps strength, and voluntary activation, as well as physical performance compared with sham TENS + TE (Sham) and TE alone in individuals with symptomatic KOA and QVAF.

METHODS

Ninety individuals participated in a double-blinded randomized controlled trial. Everyone received 10 standardized TE sessions of physical therapy. TENS + TE and Sham groups applied the respective devices during all TE sessions and throughout activities of daily living over 4 wk. The Western Ontario and McMaster University Osteoarthritis Index (WOMAC), quadriceps strength, and voluntary activation, as well as a 20-m walk test, chair-stand test, and stair-climb test were performed at baseline, after the 4-wk intervention (post 1) and at 8 wk after the start of the intervention (post 2). Mixed-effects models were used to determine between-group differences between baseline and post 1, as well as baseline and post 2.

RESULTS

Improvements in WOMAC subscales, quadriceps strength, and voluntary activation, 20-m walk times, chair-stand repetitions, and stair-climb time were found at post 1 and post 2 compared with baseline for all groups (P < 0.05). WOMAC Pain and Stiffness improved in the TENS + TE group compared with TE alone at post 1 (P < 0.05); yet, no other between-group differences were found.

CONCLUSIONS

TE effectively improved patient-reported function, quadriceps strength, and voluntary activation, as well as physical performance in individuals with symptomatic KOA and QVAF, but augmenting TE with TENS did not improve the benefits of TE.

Prevalence of and Risk Factors for Total Hip and Knee Replacement in Retired National Football League Athletes

BACKGROUND

Osteoarthritis is a substantial cause of disability. Joint replacement prevalence relates to the burden of severe osteoarthritis, and identifying risk factors for end-stage disease may indicate intervention opportunities. American football has high youth and elite participation, and determining risk factors for severe osteoarthritis may support future morbidity prevention.

PURPOSE

To (1) determine the prevalence of hip and knee replacement in retired National Football League (NFL) athletes, (2) examine risk factors for replacement, and (3) identify the association between knee injuries and knee replacement.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Retired NFL athletes who participated in a general health survey were included. This historical cohort included those playing between 1929 and 2001. The association between self-reported playing or injury history, and replacement after retirement, was assessed with prevalence ratios (PRs). Models were adjusted for potential confounders of age and weight.

RESULTS

Data for 2432 retired male NFL players (69.3% response rate) who had participated in football for a mean 15.2 years were included, in which 277 players reported replacement after retirement (11.4%). More participants reported knee replacement (7.7%) than hip replacement (4.6%). The majority of participants reported previous severe knee injury (53%), and the most prevalent was meniscal tear (32.2%). In multivariable models, age (10-year increase, PR, 2.23; 95% CI, 1.99-2.51), current weight (PR, 1.10; 95% CI, 1.06-1.14), and reporting 1 (PR, 1.78; 95% CI, 1.14-2.77), 2 (PR, 1.91; 95% CI, 1.16-3.15), or ≥3 knee injuries (PR, 3.44; 95% CI, 2.33-5.09) were associated with knee replacement. Age (10-year increase, PR, 1.86; 95% CI, 1.59-2.18), linemen (PR, 1.62; 95% CI, 1.03-2.55), and reporting 1 (PR, 1.72; 95% CI, 1.05-2.80), 2 (PR, 2.77 95% CI, 1.58-4.84), or ≥3 (PR, 2.44; 95% CI, 1.52-3.91) hip injuries were associated with hip replacement. Each reported knee injury type was cross-sectionally associated with replacement after retirement (P < .05).

CONCLUSION

Knee replacement was more prevalent than hip replacement. Risk factors differed between the hip and the knee, with age and severe joint injury associated with hip and knee replacement, weight with knee replacement, and playing position associated with hip replacement. Joint injury and weight management may be prevention opportunities to reduce morbidity and end-stage osteoarthritis in this population.

Ankle Sprains in the National Basketball Association, 2013-2014 Through 2016-2017

BACKGROUND

Ankle sprains are one of the most common injuries in basketball. Despite this, the incidence and setting of ankle sprains among elite basketball players are not well described.

PURPOSE

To describe the epidemiology of ankle sprains among National Basketball Association (NBA) players.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

All players on an NBA roster for ≥1 NBA game (preseason, regular season, or playoffs) during the 2013-14 through 2016-17 seasons were included. Data were collected with the NBA electronic medical record system. All NBA teams used the electronic medical record continuously throughout the study period to record comprehensive injury data, including onset, mechanism, setting, type, and time lost. Game incidence rates were calculated per 1000 player-games and per 10,000 player-minutes of participation, stratified by demographic and playing characteristics.

RESULTS

There were 796 ankle sprains among 389 players and 2341 unique NBA player-seasons reported in the league from 2013-14 through 2016-17. The overall single-season risk of ankle sprain was 25.8% (95% CI, 23.9%-28.0%). The majority of ankle sprains occurred in games (n = 565, 71.0%) and involved a contact mechanism of injury (n = 567, 71.2%). Most ankle sprains were lateral (n = 638, 80.2%). The incidence of ankle sprain among players with a history of prior ankle sprain in the past year was 1.41 times (95% CI, 1.13-1.74) the incidence of those without a history of ankle sprain in the past year (P = .002). Fifty-six percent of ankle sprains did not result in any NBA games missed (n = 443); among those that did, players missed a median of 2 games (interquartile range, 1-4) resulting in a cumulative total of 1467 missed player-games over the 4-season study period.

CONCLUSION

Ankle sprains affect approximately 26% of NBA players on average each season and account for a large number of missed NBA games in aggregate. Younger players and players with a history of ankle sprain have elevated rates of incident ankle sprains in games, highlighting the potential benefit for integrating injury prevention programs into the management of initial sprains. Research on basketball- and ankle-specific injury prevention strategies could provide benefits.

The effect of performance demands on lower extremity biomechanics during landing and cutting tasks

BACKGROUND

Anterior cruciate ligament (ACL) injuries commonly occur during the early phase of landing and cutting tasks that involve sudden decelerations. The purpose of this study was to investigate the effects of jump height and jump speed on lower extremity biomechanics during a stop-jump task and the effect of cutting speed on lower extremity biomechanics during a side-cutting task.

METHODS

Thirty-six recreational athletes performed a stop-jump task under 3 conditions: jumping fast, jumping for maximum height, and jumping for 60% of maximum height. Participants also performed a side-cutting task under 2 conditions: cutting at maximum speed and cutting at 60% of maximum speed. Three-dimensional kinematic and kinetic data were collected.

RESULTS

The jumping fast condition resulted in increased peak posterior ground reaction force (PPGRF), knee extension moment at PPGRF, and knee joint stiffness and decreased knee flexion angle compared with the jumping for maximum height condition. The jumping for 60% of maximum height condition resulted in decreased knee flexion angle compared with the jumping for maximum height condition. Participants demonstrated greater PPGRF, knee extension moment at PPGRF, knee valgus angle and varus moment at PPGRF, knee joint stiffness, and knee flexion angle during the cutting at maximum speed condition compared with the cutting at 60% maximum speed condition.

CONCLUSION

Performing jump landing at an increased jump speed resulted in lower extremity movement patterns that have been previously associated with an increase in ACL loading. Cutting speed also affected lower extremity biomechanics. Jump speed and cutting speed need to be considered when designing ACL injury risk screening and injury prevention programs.

Can Functional Movement Assessment Predict Football Head Impact Biomechanics?

PURPOSE

The purposes of this study was to determine functional movement assessments' ability to predict head impact biomechanics in college football players and to determine whether head impact biomechanics could explain preseason to postseason changes in functional movement performance.

METHODS

Participants (N = 44; mass, 109.0 ± 20.8 kg; age, 20.0 ± 1.3 yr) underwent two preseason and postseason functional movement assessment screenings: 1) Fusionetics Movement Efficiency Test and 2) Landing Error Scoring System (LESS). Fusionetics is scored 0 to 100, and participants were categorized into the following movement quality groups as previously published: good (≥75), moderate (50-75), and poor (<50). The LESS is scored 0 to 17, and participants were categorized into the following previously published movement quality groups: good (≤5 errors), moderate (6-7 errors), and poor (>7 errors). The Head Impact Telemetry (HIT) System measured head impact frequency and magnitude (linear acceleration and rotational acceleration). An encoder with six single-axis accelerometers was inserted between the padding of a commercially available Riddell football helmet. We used random intercepts general linear-mixed models to analyze our data.

RESULTS

There were no effects of preseason movement assessment group on the two Head Impact Telemetry System impact outcomes: linear acceleration and rotational acceleration. Head impact frequency did not significantly predict preseason to postseason score changes obtained from the Fusionetics (F1,36 = 0.22, P = 0.643, R = 0.006) or the LESS (F1,36 < 0.01, P = 0.988, R < 0.001) assessments.

CONCLUSIONS

Previous research has demonstrated an association between concussion and musculoskeletal injury, as well as functional movement assessment performance and musculoskeletal injury. The functional movement assessments chosen may not be sensitive enough to detect neurological and neuromuscular differences within the sample and subtle changes after sustaining head impacts.

Lesser lower extremity mechanical loading associates with a greater increase in serum cartilage oligomeric matrix protein following walking in individuals with anterior cruciate ligament reconstruction

BACKGROUND

Aberrant mechanical loading during gait is hypothesized to contribute to the development of posttraumatic osteoarthritis following anterior cruciate ligament reconstruction. Our purpose was to determine if peak vertical ground reaction force and instantaneous vertical ground reaction force loading rate associate with the acute change in serum cartilage oligomeric matrix protein following a 20-minute bout of walking.

METHODS

We enrolled thirty individuals with a unilateral anterior cruciate ligament reconstruction. Peak vertical ground reaction force and instantaneous vertical ground reaction force loading rate were extracted from the first 50% of the stance phase of gait during a 60-second trial. Blood samples were collected immediately before and after 20 min of treadmill walking at self-selected speed. The change in serum cartilage oligomeric matrix protein from pre- to post-walking was calculated. Stepwise linear regression models were used to determine the association between each outcome of loading and the change in serum cartilage oligomeric matrix protein after accounting for sex, gait speed, time since anterior cruciate ligament reconstruction, graft type, and history of concomitant meniscal procedure (ΔR²).

FINDINGS

Lesser peak vertical ground reaction force (ΔR² = 0.208; β = -0.561; P = 0.019) and instantaneous vertical ground reaction force loading rate (ΔR² = 0.168; β = -0.519; P = 0.037) on the anterior cruciate ligament reconstructed limb associated with a greater increase in serum cartilage oligomeric matrix protein following 20 min of walking.

INTERPRETATION

Mechanical loading may be a future therapeutic target for altering the acute biochemical response to walking in individuals with an anterior cruciate ligament reconstruction.

Walking gait asymmetries 6 months following anterior cruciate ligament reconstruction predict 12-month patient-reported outcomes

The study sought to determine the association between gait biomechanics (vertical ground reaction force [vGRF], vGRF loading rate [vGRF-LR]) collected 6 months following anterior cruciate ligament reconstruction (ACLR) with patient-reported outcomes at 12 months following ACLR. Walking gait biomechanics and all subsections of the Knee Injury and Osteoarthritis Outcomes Score (KOOS) were collected at 6 and 12 months following ACLR, respectively, in 25 individuals with a unilateral ACLR. Peak vGRF and peak instantaneous vGRF-LR were extracted from the first 50% of the stance phase. Limb symmetry indices (LSI) were used to normalize outcomes in the ACLR limb to that of the uninjured limb (ACLR/uninjured). Linear regression analyses were used to determine associations between biomechanical outcomes and KOOS while accounting for walking speed. Receiver operator characteristic curves were used to determine the accuracy of 6-month biomechanical outcomes for identifying individuals with acceptable patient-reported outcomes, using previously defined KOOS cut-off scores, 12 months post-ACLR. Individuals with lower peak vGRF LSI 6 months post-ACLR demonstrated worse patient-reported outcomes (KOOS Pain, Activities of Daily life, Sport and Recreation, Quality of Life) at the 12-month exam. A peak vGRF LSI ≥0.99 6 months following ACLR associated with 13.33× higher odds of reporting acceptable patient-reported outcomes 12 months post-ACLR. Lesser peak vGRF LSI during walking at 6-months post-ACLR may be a critical indicator of worse future patient-reported outcomes. Clinical significance achieving early symmetrical lower extremity loading and minimizing under-loading of the ACLR limb during walking may be a potential therapeutic target for improving patient-reported outcomes post-ACLR. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2932-2940, 2018.

Movement profile influences systemic stress and biomechanical resilience to high training load exposure

OBJECTIVES

Determine the influence of movement profile on systemic stress and mechanical loading before and after high training load exposure.

DESIGN

Cross-sectional cohort study.

METHODS

43 physically active, college-aged field or court sport female athletes participated in this study. Participants were assigned to a "excellent" (n=22; age=20.5±1.9yrs, height=1.67±0.67m, mass=64.5±7.8kg) or "poor" (n=21; age=20.4±1.3yrs, height=1.69±0.67m, mass=60.9±6.1kg) movement group defined by The Landing Error Scoring System. Participants completed five cycles of high training load exercise of 5-min treadmill-running at a speed coincident with 100-120% ventilatory threshold and 10 jump-landings from a 30-cm box. Jump-landing vertical ground reaction force and serum cortisol were evaluated prior to and following exercise. Vertical ground reaction force ensemble averages and 95% confidence interval waveforms were generated for pre-exercise, post-exercise, and pre-post exercise changes. A two-way mixed model ANOVA was used to evaluate the effect of movement profile on systemic stress before and after exercise.

RESULTS

There was no significant difference in changes in serum cortisol between the poor and excellent groups (p=0.69) in response to exercise. Overall, individuals in the poor group exhibited a higher serum cortisol level (p<0.05, d=0.85 [0.19,1.48]). The poor group exhibited higher magnitude vertical ground reaction force prior to (d=1.02-1.26) and after exercise (d=1.15) during a majority of the stance phase.

CONCLUSIONS

Individuals with poor movement profiles experience greater mechanical loads compared to individuals with excellent movement profiles. A poor movement profile is associated with greater overall concentrations of circulating cortisol, representative of greater systemic stress.

Associations Between Slower Walking Speed and T1ρ Magnetic Resonance Imaging of Femoral Cartilage Following Anterior Cruciate Ligament Reconstruction

OBJECTIVE

To determine whether walking speed, collected at 6 and 12 months following anterior cruciate ligament reconstruction (ACLR), is associated with inter-extremity differences in proteoglycan density, measured via T1ρ magnetic resonance imaging, in tibiofemoral articular cartilage 12 months following ACLR.

METHODS

Twenty-one individuals with a unilateral patellar-tendon autograft ACLR (10 women and 11 men, mean ± SD age 23.9 ± 2.7 years, mean ± SD body mass index 23.9 ± 2.7 kg/m² ) were recruited for participation in this study. Walking speed was collected using 3-dimensional motion capture at 6 and 12 months following ACLR. The articular cartilage of the medial femoral condyle (MFC) and lateral femoral condyle and medial and lateral tibial condyles was manually segmented and subsectioned into 3 regions of interest (anterior, central, and posterior) based on the location of the meniscus in the sagittal plane. Inter-extremity mean T1ρ relaxation time ratios (T1ρ ACLR extremity / T1ρ contralateral extremity) were calculated and used for analysis. Pearson product-moment correlations were used to determine associations between walking speed and inter-extremity differences in T1ρ relaxation time ratios.

RESULTS

Slower walking speed 6 months post-ACLR was significantly associated with higher T1ρ relaxation time ratios in the MFC of the ACLR extremity 12 months following ACLR (posterior MFC, r = -0.51, P = 0.02; central MFC, r = -0.47, P = 0.04). Similarly, slower walking speed at 12 months post-ACLR was significantly associated with higher T1ρ relaxation time ratios in the posterior MFC ACLR extremity (r = -0.47, P = 0.04) 12 months following ACLR.

CONCLUSION

Slower walking speed at 6 and 12 months following ACLR may be associated with early proteoglycan density changes in medial femoral compartment cartilage health in the first 12 months following ACLR.

Correction to: Estrogen and muscle stiffness have a negative relationship in females

In the original publication the name of the fourth reviewer was incorrectly published.

Quadriceps Neuromuscular Function and Jump-Landing Sagittal-Plane Knee Biomechanics After Anterior Cruciate Ligament Reconstruction

CONTEXT

  Aberrant biomechanics may affect force attenuation at the knee during dynamic activities, potentially increasing the risk of sustaining a knee injury or hastening the development of osteoarthritis after anterior cruciate ligament reconstruction (ACLR). Impaired quadriceps neuromuscular function has been hypothesized to influence the development of aberrant biomechanics.

OBJECTIVE

  To determine the association between quadriceps neuromuscular function (strength, voluntary activation, and spinal-reflex and corticomotor excitability) and sagittal-plane knee biomechanics during jump landings in individuals with ACLR.

DESIGN

  Cross-sectional study.

SETTING

  Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Twenty-eight individuals with unilateral ACLR (7 men, 21 women; age = 22.4 ± 3.7 years, height = 1.69 ± 0.10 m, mass = 69.4 ± 10.1 kg, time postsurgery = 52 ± 42 months).

MAIN OUTCOME MEASURE(S)

  We quantified quadriceps spinal-reflex excitability via the Hoffmann reflex normalized to maximal muscle response (H : M ratio), corticomotor excitability via active motor threshold, strength as knee-extension maximal voluntary isometric contraction (MVIC), and voluntary activation using the central activation ratio (CAR). In a separate session, sagittal-plane kinetics (peak vertical ground reaction force [vGRF] and peak internal knee-extension moment) and kinematics (knee-flexion angle at initial contact, peak knee-flexion angle, and knee-flexion excursion) were collected during the loading phase of a jump-landing task. Separate bivariate associations were performed between the neuromuscular and biomechanical variables.

RESULTS

  In the ACLR limb, greater MVIC was associated with greater peak knee-flexion angle ( r = 0.38, P = .045) and less peak vGRF ( r = -0.41, P = .03). Greater CAR was associated with greater peak internal knee-extension moment (ρ = -0.38, P = .045), and greater H : M ratios were associated with greater peak vGRF ( r = 0.45, P = .02).

CONCLUSIONS

  Greater quadriceps MVIC and CAR may provide better energy attenuation during a jump-landing task. Individuals with greater peak vGRF in the ACLR limb possibly require greater spinal-reflex excitability to attenuate greater loading during dynamic movements.

National Athletic Trainers' Association Position Statement: Prevention of Anterior Cruciate Ligament Injury

OBJECTIVE

  To provide certified athletic trainers, physicians, and other health care and fitness professionals with recommendations based on current evidence regarding the prevention of noncontact and indirect-contact anterior cruciate ligament (ACL) injuries in athletes and physically active individuals.

BACKGROUND

  Preventing ACL injuries during sport and physical activity may dramatically decrease medical costs and long-term disability. Implementing ACL injury-prevention training programs may improve an individual's neuromuscular control and lower extremity biomechanics and thereby reduce the risk of injury. Recent evidence indicates that ACL injuries may be prevented through the use of multicomponent neuromuscular-training programs.

RECOMMENDATIONS

  Multicomponent injury-prevention training programs are recommended for reducing noncontact and indirect-contact ACL injuries and strongly recommended for reducing noncontact and indirect-contact knee injuries during physical activity. These programs are advocated for improving balance, lower extremity biomechanics, muscle activation, functional performance, strength, and power, as well as decreasing landing impact forces. A multicomponent injury-prevention training program should, at minimum, provide feedback on movement technique in at least 3 of the following exercise categories: strength, plyometrics, agility, balance, and flexibility. Further guidance on training dosage, intensity, and implementation recommendations is offered in this statement.

Effect of a Lower Extremity Preventive Training Program on Physical Performance Scores in Military Recruits

Peck, KY, DiStefano, LJ, Marshall, SW, Padua, DA, Beutler, AI, de la Motte, SJ, Frank, BS, Martinez, JC, and Cameron, KL. Effect of a lower extremity preventive training program on physical performance scores in military recruits. J Strength Cond Res 31(11): 3146-3157, 2017-Exercise-based preventive training programs are designed to improve movement patterns associated with lower extremity injury risk; however, the impact of these programs on general physical fitness has not been evaluated. The purpose of this study was to compare fitness scores between participants in a preventive training program and a control group. One thousand sixty-eight freshmen from a U.S. Service Academy were cluster-randomized into either the intervention or control group during 6 weeks of summer training. The intervention group performed a preventive training program, specifically the Dynamic Integrated Movement Enhancement (DIME), which is designed to improve lower extremity movement patterns. The control group performed the Army Preparation Drill (PD), a warm-up designed to prepare soldiers for training. Main outcome measures were the Army Physical Fitness Test (APFT) raw and scaled (for age and sex) scores. Independent t tests were used to assess between-group differences. Multivariable logistic regression models were used to control for the influence of confounding variables. Dynamic Integrated Movement Enhancement group participants completed the APFT 2-mile run 20 seconds faster compared with the PD group (p < 0.001), which corresponded with significantly higher scaled scores (p < 0.001). Army Physical Fitness Test push-up scores were significantly higher in the DIME group (p = 0.041), but there were no significant differences in APFT sit-up scores. The DIME group had significantly higher total APFT scores compared with the PD group (p < 0.001). Similar results were observed in multivariable models after controlling for sex and body mass index (BMI). Committing time to the implementation of a preventive training program does not appear to negatively affect fitness test scores.

Automated Quantification of the Landing Error Scoring System With a Markerless Motion-Capture System

CONTEXT

  The Landing Error Scoring System (LESS) can be used to identify individuals with an elevated risk of lower extremity injury. The limitation of the LESS is that raters identify movement errors from video replay, which is time-consuming and, therefore, may limit its use by clinicians. A markerless motion-capture system may be capable of automating LESS scoring, thereby removing this obstacle.

OBJECTIVE

  To determine the reliability of an automated markerless motion-capture system for scoring the LESS.

DESIGN

  Cross-sectional study.

SETTING

  United States Military Academy.

PATIENTS OR OTHER PARTICIPANTS

  A total of 57 healthy, physically active individuals (47 men, 10 women; age = 18.6 ± 0.6 years, height = 174.5 ± 6.7 cm, mass = 75.9 ± 9.2 kg).

MAIN OUTCOME MEASURE(S)

  Participants completed 3 jump-landing trials that were recorded by standard video cameras and a depth camera. Their movement quality was evaluated by expert LESS raters (standard video recording) using the LESS rubric and by software that automates LESS scoring (depth-camera data). We recorded an error for a LESS item if it was present on at least 2 of 3 jump-landing trials. We calculated κ statistics, prevalence- and bias-adjusted κ (PABAK) statistics, and percentage agreement for each LESS item. Interrater reliability was evaluated between the 2 expert rater scores and between a consensus expert score and the markerless motion-capture system score.

RESULTS

  We observed reliability between the 2 expert LESS raters (average κ = 0.45 ± 0.35, average PABAK = 0.67 ± 0.34; percentage agreement = 0.83 ± 0.17). The markerless motion-capture system had similar reliability with consensus expert scores (average κ = 0.48 ± 0.40, average PABAK = 0.71 ± 0.27; percentage agreement = 0.85 ± 0.14). However, reliability was poor for 5 LESS items in both LESS score comparisons.

CONCLUSIONS

  A markerless motion-capture system had the same level of reliability as expert LESS raters, suggesting that an automated system can accurately assess movement. Therefore, clinicians can use the markerless motion-capture system to reliably score the LESS without being limited by the time requirements of manual LESS scoring.