The Influence of Lower Extremity Biomechanics on Biochemical Markers of Bone Turnover During Army Cadet Basic Training

Lower extremity stress fracture rates are high among military personnel, result in substantial lost duty time, and inhibit military readiness. Stress fracture risk factors include aberrant biomechanics, previous musculoskeletal injury, physical fitness, and anthropometric measurements. It is unknown how these risk factors influence bone formation and resorption (turnover) biomarkers. Elucidating the relationships between stress fracture risk factors and bone turnover biomarkers will provide insight into how these factors influence bone health. Our primary aim was to characterize the effects of stress fracture risk factors on bone turnover biomarkers. Our secondary aim was to validate an automated markerless motion capture system. We hypothesized the presence of stress fracture risk factors would result in bone biomarker profiles indicative of high turnover rates. We also hypothesized the markerless motion capture system would provide valid kinematic measurements. Army cadets completing Cadet Basic Training (CBT) were assessed via a jump-landing assessment and other stress fracture risk factors were recorded. Bone turnover biomarkers were measured post-CBT. Linear regression models were used to determine the extent to which stress fracture risk factors influenced bone turnover biomarkers. Kinematic measures calculated by the markerless motion capture system during a jump-landing assessment were compared against a stereophotogrammetric motion capture system. Lower extremity stress fracture risk factors predicted post-CBT bone turnover biomarkers. Overall movement quality was not predictive, but variables associated with sagittal plane displacement and foot position at initial ground contact did predict post-CBT bone turnover biomarkers. Injury during CBT, physical fitness test performance, and mass also predicted post-CBT bone turnover biomarkers. Moderate agreement was observed between the markerless and stereophotogrammetric motion capture systems. Better agreement was observed for sagittal than frontal plane joint angles and for maximum and displacement angles than initial ground contact joint angles. Our findings provide important information regarding how stress fracture risk factors affect bone health. The markerless motion capture system was limited in identifying minute changes in trunk and lower extremity joint angles but can accurately identify gross movement patterns. These findings will guide interventions to reduce stress fracture risks and guide the use of automated movement assessments for identifying injury risks.Doctor of Philosoph

Die Ebstorfer Weltkarte. Die größte Karte des Mittelalters

La carte du monde d’Ebstorf est, comme l’énonce le sous-titre de l’ouvrage, « la plus grande carte du Moyen Âge ». Elle se composait de 30 morceaux de parchemin collés et mesurait environ 3,6 × 3,6 mètres. Une mappemonde ronde, entourée de textes explicatifs sur la structure du monde et de nombreux peuples et animaux sauvages, montrait le monde selon les idées médiévales : orienté à l’est et divisé en trois continents par le schéma en T. L’Asie occupait sa moitié orientale, l’Afrique et l’Eur..

Michael Borgolte, Die Welten des Mittelalters.

Avec son ouvrage Die Welten des Mittelalters. Globalgeschichte eines Jahrtausends [Les Mondes du Moyen Âge. Histoire globale d’un millénaire], le médiéviste berlinois Michael Borgolte présente un ouvrage de poids : en 1100 pages, il passe en revue 1000 ans d’histoire globale, des îles du Pacifique aux gigantesques masses terrestres d’Afrique, d’Asie et d’Europe (qu’il nomme ‘Eufrasie’), en passant par les deux Amériques. La bibliographie volumineuse du volume laisse entrevoir l’ampleur du tra..

Group comparison of lower extremity muscle activation and lower extremity muscular flexibility and their effect on single leg squat performance

Knee valgus is a potential risk factor for lower extremity (LE) injuries. LE movement screenings and flexibility measurements may be utilized to identify neuromuscular patterns, which contribute to knee valgus. There are few studies that have investigated how flexibility and muscular activation differ between individuals who display medial knee displacement (MKD) during a single leg squat (SLS) and those who do not. We hypothesized that flexibility and muscular activation would differ between the groups. Forty individuals completed flexibility measurements and a SLS task while EMG data were collected from eight LE muscles. Three MANOVAs were run comparing flexibility measurements, EMG data, and muscle co-activation ratios. The MKD group had significantly less dorsiflexion, greater talar glide motion, and smaller hip adductor and gluteal co-activation ratios compared to the control group. Therefore, knee valgus appears to be influenced by decreased dorsiflexion and decreased co-activation of the Hip ADD and GMed and GMax muscles

Particulate Matter Detection In Mines Using 3D Light Detection And Ranging Technology

This paper proposes a novel portable prototype and self-contained Air Quality (AQ) monitoring device that utilizes Light Detection and Ranging (LiDAR) technology to take its measurements. The novel device aims to improve mining safety by collecting and analyzing the AQ inside mines and displaying the real-time conditions to personnel. The intent is to create a 3D map of the environment and display potentially hazardous Atmospheric Particulate Matter (APM). To achieve this goal, we prototype a portable, compact, and easy-to-operate system that utilizes LiDAR to detect APM. Then, we propose how the collected data can be used to calculate real-time AQ conditions. Finally, we illustrate selected results to show the importance and feasibility of our novel prototype

Static and dynamic single leg postural control performance during dual-task paradigms

ABSTRACTCombining dynamic postural control assessments and cognitive tasks may give clinicians a more accurate indication of postural control under sport-like conditions compared to single-task assessments. We examined postural control, cognitive and squatting performance of healthy individuals during static and dynamic postural control assessments in single- and dual-task paradigms. Thirty participants (female = 22, male = 8; age = 20.8 ± 1.6 years, height = 157.9 ± 13.0 cm, mass = 67.8 ± 20.6 kg) completed single-leg stance and single-leg squat assessments on a force plate individually (single-task) and concurrently (dual-task) with two cognitive assessments, a modified Stroop test and the Brooks Spatial Memory Test. Outcomes included centre of pressure speed, 95% confidence ellipse, squat depth and speed and cognitive test measures (percentage of correct answers and reaction time). Postural control performance varied between postural control assessments and testing paradigms. Participants did not squat..

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

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 ¼ 18.6 6 0.6 years, height ¼ 174.5 6 6.7 cm, mass ¼ 75.9 6 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 j statistics, prevalence- and bias-adjusted j (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 j ¼ 0.45 6 0.35, average PABAK ¼ 0.67 6 0.34; percentage agreement ¼ 0.83 6 0.17). The markerless motion-capture system had similar reliability with consensus expert scores (average j ¼ 0.48 6 0.40, average PABAK ¼ 0.71 6 0.27; percentage agreement ¼ 0.85 6 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