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Sara L. Arena, Kelsey McLaughlin, Anh-Dung Nguyen, James M. Smoliga and Kevin R. Ford

Athletic individuals may differ in body segment inertial parameter (BSIP) estimates due to differences in body composition, and this may influence calculation of joint kinetics. The purposes of this study were to (1) compare BSIPs predicted by the method introduced by de Leva1 with DXA-derived BSIPs in collegiate female soccer players, and (2) examine the effects of these BSIP estimation methods on joint moment and power calculations during a drop vertical jump (DVJ). Twenty female NCAA Division I soccer players were recruited. BSIPs of the shank and thigh (mass, COM location, and radius of gyration) were determined using de Leva’s method and analysis of whole-body DXA scans. These estimates were used to determine peak knee joint moments and power during the DVJ. Compared with DXA, de Leva’s method located the COM more distally in the shank (P = .008) and more proximally in the thigh (P < .001), and the radius of gyration of the thigh to be further from the thigh COM (P < .001). All knee joint moment and power measures were similar between methods. These findings suggest that BSIP estimation may vary between methods, but the impact on joint moment calculations during a dynamic task is negligible.

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Brad W. Willis, Katie Hocker, Swithin Razu, Aaron D. Gray, Marjorie Skubic, Seth L. Sherman, Samantha Kurkowski and Trent M. Guess

correlations to ACL injury risk. 3 – 5 Specifically, an excessive knee abduction angle (KAA), a measure of tibia displacement relative to the femur acquired by 3-dimensional motion capture systems, has been linked to elevated risk of injury to the ACL. 3 A bilateral jump-landing task, the drop vertical jump

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Gabriel Andrade Paz, Marianna de Freitas Maia, Haroldo Gualter Santana, Humberto Miranda, Vicente Lima and John D. Willson

tibial abduction, 10 – 12 which, in the presence of a quadriceps force, increase both ACL strain and patellofemoral joint stress. 13 , 14 The drop vertical jump (DVJ) is a task routinely used to assess athletic injury risk and performance potential. 15 Increased frontal plane knee motion during the DVJ

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Kathryn Mills, Aula Idris, Thu-An Pham, John Porte, Mark Wiggins and Manolya Kavakli

calculate the projected frontal plane knee angle. 19 A static calibration was utilized to determine the “0” value for each participant. Figure 1 —The custom-built VR game. Participant stood on the 30-cm block and performed a maximal drop vertical jump. If the sensor (located in middle of image) detected

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Trent M. Guess, Swithin Razu, Amirhossein Jahandar, Marjorie Skubic and Zhiyu Huo

The Microsoft Kinect is becoming a widely used tool for inexpensive, portable measurement of human motion, with the potential to support clinical assessments of performance and function. In this study, the relative osteokinematic Cardan joint angles of the hip and knee were calculated using the Kinect 2.0 skeletal tracker. The pelvis segments of the default skeletal model were reoriented and 3-dimensional joint angles were compared with a marker-based system during a drop vertical jump and a hip abduction motion. Good agreement between the Kinect and marker-based system were found for knee (correlation coefficient = 0.96, cycle RMS error = 11°, peak flexion difference = 3°) and hip (correlation coefficient = 0.97, cycle RMS = 12°, peak flexion difference = 12°) flexion during the landing phase of the drop vertical jump and for hip abduction/adduction (correlation coefficient = 0.99, cycle RMS error = 7°, peak flexion difference = 8°) during isolated hip motion. Nonsagittal hip and knee angles did not correlate well for the drop vertical jump. When limited to activities in the optimal capture volume and with simple modifications to the skeletal model, the Kinect 2.0 skeletal tracker can provide limited 3-dimensional kinematic information of the lower limbs that may be useful for functional movement assessment.

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Kevin R. Ford, Anh-Dung Nguyen, Eric J. Hegedus and Jeffrey B. Taylor

Virtual environments with real-time feedback can simulate extrinsic goals that mimic real life conditions. The purpose was to compare jump performance and biomechanics with a physical overhead goal (POG) and with a virtual overhead goal (VOG). Fourteen female subjects participated (age: 18.8 ± 1.1 years, height: 163.2 ± 8.1 cm, weight 63.0 ± 7.9 kg). Sagittal plane trunk, hip, and knee biomechanics were calculated during the landing and take-off phases of drop vertical jump with different goal conditions. Repeated-measures ANOVAs determined differences between goal conditions. Vertical jump height displacement was not different during VOG compared with POG. Greater hip extensor moment (P < .001*) and hip angular impulse (P < .004*) were found during VOG compared with POG. Subjects landed more erect with less magnitude of trunk flexion (P = .002*) during POG compared with VOG. A virtual target can optimize jump height and promote increased hip moments and trunk flexion. This may be a useful alternative to physical targets to improve performance during certain biomechanical testing, screening, and training conditions.

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Kevin R. Ford, Gregory D. Myer, Laura C. Schmitt, Timothy L. Uhl and Timothy E. Hewett

The purpose of this study was to identify alterations in preparatory muscle activation patterns across different drop heights in female athletes. Sixteen female high school volleyball players performed the drop vertical jump from three different drop heights. Surface electromyography of the quadriceps and hamstrings were collected during the movement trials. As the drop height increased, muscle activation of the quadriceps during preparatory phase also increased (p < .05). However, the hamstrings activation showed no similar increases relative to drop height. Female athletes appear to preferentially rely on increased quadriceps activation, without an increase in hamstrings activation, with increased plyometric intensity. The resultant decreased activation ratio of the hamstrings relative to quadriceps before landing may represent altered dynamic knee stability and may contribute to the increased risk of ACL injury in female athletes.

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Christopher A. DiCesare, Adam W. Kiefer, Scott Bonnette and Gregory D. Myer

. Therefore, the purpose of this study was to examine movement patterns exhibited by athletes during a jump-landing task performed as part of both a standard biomechanical assessment (ie, drop vertical jump [DVJ]) and a sport-specific VR-based assessment to examine potential differences in assessed injury

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Rhodri S. Lloyd, Jon L. Oliver, Gregory D. Myer, Mark B. De Ste Croix, Josh Wass and Paul J. Read

sports such as soccer, with a lack of consistency among practitioners. 7 The drop vertical jump (DVJ) is one of the most commonly used screening tools within the literature, 4 , 8 , 9 and dynamic knee valgus measured during this test has previously been associated with a greater risk of anterior

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Anh-Dung Nguyen, Jeffrey B. Taylor, Taylor G. Wimbish, Jennifer L. Keith and Kevin R. Ford

a drop vertical jump (DVJ) compared with females. 3 These findings suggest that females tend to adopt a landing strategy that underutilizes the hip extensors and may contribute to increased frontal plane knee loading. Collectively, this evidence has led to research aimed at developing a more hip