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 ¼ 20.50 6 2.78 years, height ¼ 170.36 6 9.82 cm, mass ¼ 68.38 6 10.07 kg, body mass index ¼ 23.50 6 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 (a < .05). Results: Agreement existed between the systems (ICC range ¼1.52 to 0.96; ICC average ¼ 0.58), with 75.00% (n ¼ 24/ 32) of the measures being validated (P < .05). Agreement was better for sagittal- (ICC average ¼ 0.84) than frontal- (ICC average ¼ 0.35) plane measures. Agreement was best for MAX (ICC average ¼ 0.77) compared with IC (ICC average ¼ 0.56) and DSP (ICC average ¼ 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

Longitudinal Analysis of Inter-Limb Coordination Before and After Anterior Cruciate Ligament Injury: The JUMP-ACL Study

Purpose: Inter-limb coordination may provide insight into why patients with anterior cruciate ligament reconstructive surgery (ACLR) have an increased risk for future injury and osteoarthritis. The purpose of this study was to compare inter-limb coordination prior-to anterior cruciate ligament (ACL) injury and following ACLR. Methods: Unilateral lower extremity biomechanics during a double-leg jump landing were collected prior-to ACL injury (baseline) and after ACLR, rehabilitation, and return to physical activity (follow-up). Sixty-nine participants were included in this analysis: 31 participants suffered an ACL injury since baseline: 12 injured the leg tested at baseline [ACLR-injured leg (ACLR-INJ), n = 12] and 19 injured the leg that was not tested at baseline [ACLR-uninjured leg (ACLR-UNINJ) n = 19]; 38 participants served as matched controls. Inter-limb coordination—calculated as the mean coupling angle—between the hip and knee were measured in the respective leg of each defined group and compared amongst groups at baseline and follow-up. Results: We observed no significant change in sagittal or frontal plane inter-limb coordination amongst groups or across time (P > 0.05). A significant decrease in inter-limb coordination in the transverse plane from baseline and follow-up was observed but limited to the ACLR-INJ group (P = 0.016). Conclusion: The primary finding of this study is that inter-limb coordination between the hip and knee in the sagittal and frontal plane is unchanged by ACL injury and ACLR. This may help explain previous observations of changes in kinematics at both the hip and knee in this population. Our observation of alterations in the transverse plane should be interpreted with caution, but may provide additional evidence for potential mechanisms that lead to the development of osteoarthritis in ACLR patients

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 injuryprevention 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

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 ± 1.9 yrs, height = 1.67 ± 0.67 m, mass = 64.5 ± 7.8 kg) or “poor” (n = 21; age = 20.4 ± 1.3 yrs, height = 1.69 ± 0.67 m, mass = 60.9 ± 6.1 kg) 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

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

Biomechanical risk factors for lower extremity stress fracture

Objectives: Stress fracture injuries disproportionately affect athletes and military service members and little is known about the modifiable biomechanical risk factors associated with these injuries. The purpose of this study was to prospectively examine the association between neuromuscular and biomechanical factors upon entry to military service and the subsequent incidence of lower-extremity stress fracture injury during four years of follow-up. Methods: We analyzed data from the JUMP-ACL cohort, an existing prospective cohort study of military cadets. JUMP-ACL conducted detailed motion analysis during a jump landing task at the initiation of each subject’s military career. We limited our analyses to the class years 2009-2013 (i.e., subjects who completed baseline testing in 2005-2008). There were 1895 subjects available for analysis. Fifty-two subjects reported a history of stress fracture at baseline and were excluded from further analysis leaving 1843 subjects. Incident lower extremity-stress fracture cases were identified through the Defense Medical Surveillance System and the Cadet Injury and Illness Tracking System during the follow-up period. The electronic medical records of each potential incident case were reviewed and each case was confirmed by an adjudication committee consisting of two sports medicine fellowship trained orthopaedic surgeons. The primary outcome of interest was the incidence rate of lower-extremity stress fracture during the follow-up period. The association between incident stress fracture and sagittal, frontal, and transverse plane hip and knee kinematics during the jump-landing task were examined at initial contact (IC), 15%(T15), 50%(T50), 85%(T85) and 100%(T100) of stance phase. Descriptive plots of all biomechanical variables along with 95% confidence intervals (CI) were generated during the stance phase of the jump landing task. Univariate and multivariable Poisson regression models were used to estimate the association between baseline biomechanical factors and the incidence rate of lower-extremity stress fracture during follow-up. Results: Overall, 94 (5.1%, 95%CI: 4.14, 6.21) subjects sustained an incident stress fracture during the follow-up period. The incidence rate for stress fracture injuries among females was nearly three times greater when compared to males (IRR=2.86, 95%CI: 1.88, 4.34, p<0.001). Compared to those with greater than 5° of knee valgus, subjects with neutral or varus knee alignment experienced incidence rates for stress fracture that were 43%-53% lower at IC (IRR=0.57, 95%CI: 0.29, 1.11, p=0.10), T50 (IRR=0.47, 95%CI=0.23, 1.00, p=0.05), and T85 (IRR=0.53, 95%CI: 0.29, 0.98, p=0.04). Subjects with greater than 5° of internal knee rotation exhibited rates for stress fracture that were 2-4 times higher at T15 (IRR=2.31, 95%CI: 1.01, 5.27, p=0.05), T50 (IRR=3.98, 95%CI: 0.99, 16.00, p=0.05), and T85 (IRR=2.31, 95%CI: 0.86, 6.23, p=0.10), when compared to those with neutral or external knee rotation alignment. Conclusion: Several potentially modifiable biomechanical factors at the time of entry into military service appear to be associated with the subsequent rate of stress fracture. It is possible that injury prevention programs targeted to address these biomechanical movement patterns may reduce the risk of stress fracture injury in athletes and military service members

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