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Deborah L. King and Barbara C. Belyea

Context: Landing kinematics have been identified as a risk factor for knee injury. Detecting atypical kinematics in clinical settings is important for identifying individuals at risk for these injuries. Objective: To determine the reliability of a handheld tablet and application (app) for measuring lower-extremity kinematics during drop vertical-jump landings. Design: Measurement reliability. Setting: Laboratory. Participants: 23 healthy young adults with no lower-extremity injuries and no contraindications for jumping and landing. Intervention: Subjects performed 6 drop vertical jumps that were captured with an iPad2 and analyzed with a KinesioCapture app by 2 novice and 2 experienced raters. Three trials each were captured in the frontal and sagittal planes. Main Outcome Measures: Frontal-plane projection angles, knee flexion, and hip flexion at initial contact and maximum knee flexion were measured. ICC and SEM were calculated to determine intertrial and interrater reliability. One-way ANOVAs were used to examine differences between the measured angles of the raters. Results: Average intertrial reliability ranged from .71 to .98 for novice raters and .77 to .99 for experienced raters. SEMs were 2.3-4.3° for novice raters and 1.6-3.9° for experienced raters. Interrater ICC2,1 was .39-.98 for the novice raters and .69-.93 for the experienced raters. SEMs were smallest with the experienced raters, all less than 1.5°. Conclusion: A handheld tablet and app is promising for evaluating landing kinematics and identifying individuals at risk for knee injury in a clinical setting. Intertrial reliability is good to excellent when using average trial measures. Interrater reliability is fair to excellent depending on experience level. Multiple trials should be assessed by a single rater when assessing lower-extremity mechanics with a handheld tablet and app, and results may vary with experience level or training.

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Deborah L. King, Allison S. Arnold and Sarah L. Smith

To be competitive internationally, figure skaters today must perform complex athletic skills such as triple axels. However, few skaters are executing such jumps consistently. In this study, a 3D kinematic analysis of five elite male skaters was undertaken to compare characteristics of single, double, and triple axels and to determine which parameters are most critical to completion of the triple axel. Results indicate that skaters increase their number of revolutions by increasing their rotational velocity, not by increasing their time in the air. The study also shows that skaters' triple axels travel horizontally only 70% as far as their single axels, an observation attributable to skaters' greater skid distances, greater takeoff angles, and consequently lower horizontal velocities in their triple axels. It appears that achieving a high rotational velocity by generating angular momentum at takeoff and by minimizing moment of inertia about the spin axis is a key to completing the triple axel.

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Barbara C. Belyea, Ethan Lewis, Zachary Gabor, Jill Jackson and Deborah L. King

Context: Lower-extremity landing mechanics have been implicated as a contributing factor in knee pain and injury, yet cost-effective and clinically accessible methods for evaluating movement mechanics are limited. The identification of valid, reliable, and readily accessible technology to assess lower-extremity alignment could be an important tool for clinicians, coaches, and strength and conditioning specialists. Objective: To examine the validity and reliability of using a handheld tablet and movement-analysis application (app) for assessing lower-extremity alignment during a drop vertical-jump task. Design: Concurrent validation. Setting: Laboratory. Participants: 22 healthy college-age subjects (11 women and 11 men, mean age 21 ± 1.4 y, mean height 1.73 ± 0.12 m, mean mass 71 ± 13 kg) with no lower-extremity pathology that prevented safe landing from a drop jump. Intervention: Subjects performed 6 drop vertical jumps that were recorded simultaneously using a 3-dimensional (3D) motion-capture system and a handheld tablet. Main Outcomes Measures: Angles on the tablet were calculated using a motion-analysis app and from the 3D motion-capture system using Visual 3D. Hip and knee angles were measured and compared between both systems. Results: Significant correlations between the tablet and 3D measures for select frontal- and sagittal-plane ranges of motion and angles at maximum knee flexion (MKF) ranged from r = .48 (P = .036) for frontal-plane knee angle at MKF to r = .77 (P < .001) for knee flexion at MKF. Conclusion: Results of this study suggest that a handheld tablet and app may be a reliable method for assessing select lower-extremity joint alignments during drop vertical jumps, but this technology should not be used to measure absolute joint angles. However, sports medicine specialists could use a handheld tablet to reliably record and evaluate lower-extremity movement patterns on the field or in the clinic.

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Tyler R. Keith, Tara A. Condon, Ayana Phillips, Patrick O. McKeon and Deborah L. King

The Star Excursion Balance Test (SEBT) is a valid and reliable measure of dynamic postural control. Center of pressure (COP) behavior during the SEBT could provide additional information about direction-dependent SEBT balance strategies. The purpose of this study was to quantify spatiotemporal COP differences using COP area and velocity among three different SEBT reach directions (anterior, posteromedial, posterolateral). The anterior direction COP velocity was significantly lower than both posterior directions. However, the anterior COP area was significantly greater than posterior. Based on COP behavior, the anterior and posterior reach directions appear to use different postural control strategies on the SEBT.

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Maggi M. Calo, Thomas Anania, Joseph D. Bello, Valerie A. Cohen, Siobhan C. Stack, Meredith D. Wells, Barbara C. Belyea, Deborah L. King and Jennifer M. Medina McKeon

Analyzing lower extremity (LE) landing mechanics is a main component of the screening process for athletes predisposed to injury. However, easily accessible and reliable tools for this process in a clinical setting need to be established. The purpose of this study was to determine the effect of differentiations in positioning of the iPad and evaluator on the reliability of an iPad to analyze LE landing mechanics during drop vertical jumps (DVJs). The results illustrate that iPads are reliable tools that can be used to capture and analyze DVJs. In addition, the exact positioning of the evaluator does not make a significant difference in the outcome. The results suggest that iPads are a practical and reliable alternative to traditional video analysis.