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Kristen M. Stearns-Reider, Rachel K. Straub, and Christopher M. Powers

. Participants were excluded from participation in the study if any of the following were present: (1) a history or diagnosis of hip or knee pathology or trauma (including ACL injury), (2) current hip or knee pain during any sports activities or activities of daily living, or (3) inability to perform a landing

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Nelson Cortes, James Onate, João Abrantes, Linda Gagen, Elizabeth Dowling, and Bonnie Van Lunen

The purpose of this study was to assess kinematic lower extremity motion patterns (hip flexion, knee flexion, knee valgus, and ankle dorsiflexion) during various foot-landing techniques (self-preferred, forefoot, and rear foot) between genders. 3-D kinematics were collected on 50 (25 male and 25 female) college-age recreational athletes selected from a sample of convenience. Separate repeated-measures ANOVAs were used to analyze each variable at three time instants (initial contact, peak vertical ground reaction force, and maximum knee flexion angle). There were no significant differences found between genders at the three instants for each variable. At initial contact, the forefoot technique (35.79° ± 11.78°) resulted in significantly (p = .001) less hip flexion than did the self-preferred (41.25° ± 12.89°) and rear foot (43.15° ± 11.77°) techniques. At peak vertical ground reaction force, the rear foot technique (26.77° ± 9.49°) presented significantly lower (p = .001) knee flexion angles as compared with forefoot (58.77° ± 20.00°) and self-preferred (54.21° ± 23.78°) techniques. A significant difference for knee valgus angles (p = .001) was also found between landing techniques at peak vertical ground reaction force. The self-preferred (4.12° ± 7.51°) and forefoot (4.97° ± 7.90°) techniques presented greater knee varus angles as compared with the rear foot technique (0.08° ± 6.52°). The rear foot technique created more ankle dorsiflexion and less knee flexion than did the other techniques. The lack of gender differences can mean that lower extremity injuries (e.g., ACL tears) may not be related solely to gender but may instead be associated with the landing technique used and, consequently, the way each individual absorbs jump-landing energy.

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Kathy Liu and Gary D. Heise

Dynamic stability is often measured by time to stabilization (TTS), which is calculated from the dwindling fluctuations of ground reaction force (GRF) components over time. Common protocols of dynamic stability research have involved forward or vertical jumps, neglecting different jump-landing directions. Therefore, the purpose of the present investigation was to examine the influence of different jump-landing directions on TTS. Twenty healthy participants (9 male, 11 female; age = 28 ± 4 y; body mass = 73.3 ± 21.5 kg; body height = 173.4 ± 10.5 cm) completed the Multi-Directional Dynamic Stability Protocol hopping tasks from four different directions—forward, lateral, medial, and backward—landing single-legged onto the force plate. TTS was calculated for each component of the GRF (ap = anterior-posterior; ml = medial-lateral; v = vertical) and was based on a sequential averaging technique. All TTS measures showed a statistically significant main effect for jump-landing direction. TTSml showed significantly longer times for landings from the medial and lateral directions (medial: 4.10 ± 0.21 s, lateral: 4.24 ± 0.15 s, forward: 1.48 ± 0.59 s, backward: 1.42 ± 0.37 s), whereas TTSap showed significantly longer times for landings from the forward and backward directions (forward: 4.53 ± 0.17 s, backward: 4.34 0.35 s, medial: 1.18 ± 0.49 s, lateral: 1.11 ± 0.43 s). TTSv showed a significantly shorter time for the forward direction compared with all other landing directions (forward: 2.62 ± 0.31 s, backward: 2.82 ± 0.29 s, medial: 2.91 ± 0.31 s, lateral: 2.86 ± 0.32 s). Based on these results, multiple jump-landing directions should be considered when assessing dynamic stability.

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Jae P. Yom, Kathy J. Simpson, Scott W. Arnett, and Cathleen N. Brown

One potential ACL injury situation is due to contact with another person or object during the flight phase, thereby causing the person to land improperly. Conversely, athletes often have flight-phase collisions but do land safely. Therefore, to better understand ACL injury causation and methods by which people typically land safely, the purpose of this study was to determine the effects of an in-flight perturbation on the lower extremity biomechanics displayed by females during typical drop landings. Seventeen collegiate female recreational athletes performed baseline landings, followed by either unexpected laterally-directed perturbation or sham (nonperturbation) drop landings. We compared baseline and perturbation trials using paired-samples t tests (P < .05) and 95% confidence intervals for lower-extremity joint kinematics and kinetics and GRF. The results demonstrated that perturbation landings compared with baseline landings exhibited more extended joint positions of the lower extremity at initial contact; and, during landing, greater magnitudes for knee abduction and hip adduction displacements; peak magnitudes of vertical and medial GRF; and maximum moments of ankle extensors, knee extensors, and adductor and hip adductors. We conclude that a lateral in-flight perturbation leads to abnormal GRF and angular motions and joint moments of the lower extremity.

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Komeil Dashti Rostami and Abbey Thomas

landing, 3 , 5 and altered quadriceps and hamstrings onset times. 6 – 8 However, little is known about the biomechanical adaptations patients with ACLD experience during landing. Chmielewski et al 9 and Hurd and Snyder-Mackler 10 demonstrated that patients with ACLD employ a kinematic strategy of

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Erica M. Willadsen, Andrea B. Zahn, and Chris J. Durall

increase knee flexion during landing, cutting, or jumping activities to moderate ACL strain. This review was conducted to determine if current evidence supports one of these training approaches over the others for reducing noncontact ACL injuries in adolescent female athletes. Focused Clinical Question

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Ling Li, Yu Song, Maddy Jenkins, and Boyi Dai

Noncontact anterior cruciate ligament (ACL) injuries often occur during unbalanced jump landings with most body weight on the injured leg, 1 – 4 and females have higher incidences of ACL injuries compared with males in most sports events. 5 – 7 In vitro and in vivo studies have shown that

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Jonathan M. Williams, Michael Gara, and Carol Clark

quantifying subtle changes. Hop testing is highly prevalent in lower limb rehabilitation, especially post knee surgery or in patellofemoral pain. Measuring quality of landing is challenging for clinicians using hop testing. Laboratory-based systems that quantify balance often require specific fixed

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Andrew D. Nordin and Janet S. Dufek

align with motor control interpretations. 6 , 12 , 13 – 15 Collective assessments among neural and mechanical waveforms in landing can therefore extend our understanding of gross motor control as shown in Nordin and Dufek. 16 Lesser intra-individual movement variability may also underscore overuse

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John R. Harry, Leland A. Barker, Jeffrey D. Eggleston, and Janet S. Dufek

Many competitive and recreational sports involve a propulsive vertical jump followed by a landing. An unavoidable occurrence during jump landings is impact with the ground. 1 Typically, the landing phase is evaluated with respect to injury potential due to high-magnitude vertical ground reaction