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Aisha Chen, Sandhya Selvaraj, Vennila Krishnan and Shadnaz Asgari

Accurate and reliable detection of the onset of gait initiation is essential for the correct assessment of gait. Thus, this study was aimed at evaluation of the reliability and accuracy of 3 different center of pressure–based gait onset detection algorithms: A displacement baseline–based algorithm (method 1), a velocity baseline–based algorithm (method 2), and a velocity extrema–based algorithm (method 3). The center of pressure signal was obtained during 10 gait initiation trials from 16 healthy participants and 3 participants with Parkinson’s disease. Intrasession and absolute reliability of each algorithm was assessed using the intraclass correlation coefficient and the coefficient of variation of center of pressure displacement during the postural phase of gait initiation. The accuracy was evaluated using the time error of the detected onset by each algorithm relative to that of visual inspection. The authors’ results revealed that although all 3 algorithms had high to very high intrasession reliabilities in both healthy subjects and subjects with Parkinson’s disease, methods 2 and 3 showed significantly better absolute reliability than method 1 in healthy controls (P = .001). Furthermore, method 2 outperformed the other 2 algorithms in both healthy subjects and subjects with Parkinson’s disease with an overall accuracy of 0.80. Based on these results, the authors recommend using method 2 for accurate and reliable gait onset detection.

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Kristin D. Morgan

Between-limb deficits in vertical ground reaction force (vGRF) production continue to remain years after anterior cruciate ligament rehabilitation, resulting in altered dynamic stability. However, the challenge is in identifying ways to assess this between-limb stability. This study implemented second-order autoregressive [AR(2)] modeling and its stationarity triangle to both quantitatively and visually delineate differences in dynamic stability from peak vGRF data in controls and post-anterior cruciate ligament reconstruction (ACLR) individuals during running. It was hypothesized that post-ACLR individuals would exhibit less dynamic stability than the controls, and that they would reside in a different location on the stationarity triangle, thus denoting differences in stability. The results presented supported the hypothesis that post-ACLR individuals exhibited significantly less dynamic stability than their control counterparts based on their model coefficients (AR1 P < .01; AR2 P = .02). These findings suggested that the post-ACLR individuals adopted a similar running pattern, possibly due to muscle weakness asymmetry, which was less dynamically stable and potentially places them at greater risk for injury. The ability of this approach to both quantitatively and visually delineate differences between these 2 groups indicates its potential as a return-to-sport decision tool.

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Yumeng Li, He Wang and Kathy J. Simpson

The purpose of the study was to compare the tibiofemoral contact forces of participants with chronic ankle instability versus controls during landings using a computer-simulated musculoskeletal model. A total of 21 female participants with chronic ankle instability and 21 pair-matched controls performed a drop landing task on a tilted force plate. A 7-camera motion capture system and 2 force plates were used to test participants’ lower-extremity biomechanics. A musculoskeletal model was used to calculate the tibiofemoral contact forces (femur on tibia). No significant between-group differences were observed for the peak tibiofemoral contact forces (P = .25–.48) during the landing phase based on paired t tests. The group differences ranged from 0.05 to 0.58 body weight (BW). Most participants demonstrated a posterior force (peak,  ∼1.1 BW) for most duration of the landing phase and a medial force (peak, ∼0.9 BW) and large compressive force (peak, ∼10 BW) in the landing phase. The authors conclude that chronic ankle instability may not be related to the increased tibiofemoral contact forces or knee injury mechanisms during landings on the tilted surface.

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Jennifer A. Hogg, Randy J. Schmitz and Sandra J. Shultz

Clinical femoral anteversion (Craig test) and hip range of motion (ROM) have been associated with valgus collapse, but their clinical usefulness in predicting biomechanics is unknown. Our purpose was to determine the individual and combined predictive power of femoral anteversion and passive hip ROM on 3-dimensional valgus collapse (hip internal rotation and adduction, knee rotation, and abduction) during a single-leg forward landing in females. Femoral anteversion and passive hip ROM were measured on 20 females (24.9 [4.1] y, 168.7 [8.0] cm, 63.8 [11.6] kg). Three-dimensional kinematics and kinetics were collected over 5 trials of the task. Each variable was averaged across trials. Backward, stepwise regressions determined the extent to which our independent variables were associated with valgus collapse. The combination of greater hip internal and external rotation ROM (partial r = .52 and .56) predicted greater peak knee internal rotation moment (R 2 = .38, P = .02). Less hip internal rotation ROM (partial r = −.44) predicted greater peak knee abduction moments (R 2 = .20, P = .05). Greater total hip ROM (internal and external rotation ROM) was not consistently associated with combined motions of valgus collapse but was indicative of isolated knee moments. Passive hip ROM is more associated with knee moments than is femoral anteversion as measured with Craig test.

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Christian A. Clermont, Lauren C. Benson, W. Brent Edwards, Blayne A. Hettinga and Reed Ferber

The purpose of this study was to use wearable technology data to quantify alterations in subject-specific running patterns throughout a marathon race and to determine if runners could be clustered into subgroups based on similar trends in running gait alterations throughout the marathon. Using a wearable sensor, data were collected for cadence, braking, bounce, pelvic rotation, pelvic drop, and ground contact time for 27 runners. A composite index was calculated based on the “typical” data (4–14 km) for each runner and evaluated for 14 individual 2-km sections thereafter to detect “atypical” data (ie, higher indices). A cluster analysis assigned all runners to a subgroup based on similar trends in running alterations. Results indicated that the indices became significantly higher starting at 20 to 22 km. Cluster 1 exhibited lower indices than cluster 2 throughout the marathon, and the only significant difference in characteristics between clusters was that cluster 1 had a lower age–grade performance score than cluster 2. In summary, this study presented a novel method to investigate the effects of fatigue on running biomechanics using wearable technology in a real-world setting. Recreational runners with higher age–grade performance scores had less atypical running patterns throughout the marathon compared with runners with lower age–grade performance scores.

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Cherice N. Hughes-Oliver, Kathryn A. Harrison, D.S. Blaise Williams III and Robin M. Queen

In healthy individuals, symmetrical lower-extremity movement is often assumed and calculated using discrete points during various tasks. However, measuring overall movement patterns using methods such as statistical parametric mapping (SPM) may allow for better interpretation of human movement. This study demonstrated the ability of SPM to assess interlimb differences in lower-extremity movement during 2 example tasks: running and landing. Three-dimensional motion analysis was used to determine sagittal and frontal plane lower-extremity joint angles in (1) young and older individuals during running and (2) patients with anterior cruciate ligament reconstruction and uninjured control athletes during landing. Interlimb differences within each group were compared using SPM and paired t tests on peak discrete angles. No differences between limbs were found between young and older runners using SPM. Peak ankle eversion and plantar flexion angles differed between limbs in young and older runners. Sagittal plane hip angle varied between limbs in uninjured control athletes. Frontal plane ankle angle and sagittal plane knee and hip angles differed between limbs in patients with anterior cruciate ligament reconstruction using SPM and discrete analysis. These data suggest that SPM can be useful to determine clinically meaningful interlimb differences during running and landing in multiple populations.

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Ebrahim Norouzi, Fatemeh Sadat Hosseini, Mohammad Vaezmosavi, Markus Gerber, Uwe Pühse and Serge Brand

In sport such as darts, athletes are particularly challenged by demands for concentration, skills underpinned by implicit learning, and fine motor skill control. Several techniques have been proposed to improve the implicit learning of such skills, including quiet eye training (QET) and quiet mind training (QMT). Here, the authors tested whether and to what extent QET or QMT, compared with a control condition, might improve skills among novice dart players. In total, 30 novice dart players were randomly assigned either to the QET, QMT, or a control condition. Dart playing skills were assessed four times: at the baseline, 7 days later, under stress conditions, and at the study’s end. Over time, errors reduced, but more so in the QET and QMT conditions than in the control condition. The pattern of the results indicates that, among novice dart players and compared with a control condition, both QET and QMT provide significant improvements in implicit learning.

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Anne Sofie B. Malling, Bo M. Morberg, Lene Wermuth, Ole Gredal, Per Bech and Bente R. Jensen

The authors examined the associations between the performance of upper- and lower-extremity motor tasks across task complexity and motor symptom severity, overall disease severity, and the physical aspects of quality of life in persons with Parkinson’s disease. The performance was assessed for three lower-extremity tasks and two upper-extremity tasks of different levels of complexity. The motor symptoms and overall disease severity correlated significantly with all motor tasks with higher correlation coefficients in the complex tasks. Thus, the strength of the association between disease severity or severity of motor symptoms and motor performance is task-specific, with higher values in complex motor tasks than in simpler motor tasks. Mobility-related and activity-of-daily-living-related quality of life correlated with lower-extremity tasks of low and medium complexity and with the complex upper-extremity task, respectively; this suggests that Parkinson’s Disease Questionnaire-39 is capable of differentiating between the impact of gross and fine motor function on quality of life.

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Janina M. Prado-Rico and Marcos Duarte

The goal of this work was to investigate body weight distribution during relaxed and quiet (constrained) standing tasks. Forty-one healthy, young adults performed relaxed and quiet standing tasks, and they stood with each leg on a separate force plate. The weight distribution asymmetry across time was computed as the difference between the right and left vertical force time series. The subjects presented a small average across time asymmetry during relaxed and quiet standing. However, during relaxed standing, the subjects alternated between postures, and, as a result, they were largely asymmetrical over time (instant by instant). Two unexpected results that the authors found for the relaxed standing task were that women were more asymmetrical over time than men and that there were two preferential modes of weight distribution.

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Manuel E. Hernandez, Erin O’Donnell, Gioella Chaparro, Roee Holtzer, Meltem Izzetoglu, Brian M. Sandroff and Robert W. Motl

Functional near-infrared spectroscopy was used to evaluate prefrontal cortex activation differences between older adults with multiple sclerosis (MS) and healthy older adults (HOA) during the performance of a balance- and attention-demanding motor task. Ten older adults with MS and 12 HOA underwent functional near-infrared spectroscopy recording while talking, virtual beam walking, or virtual beam walking while talking on a self-paced treadmill. The MS group demonstrated smaller increases in prefrontal cortex oxygenation levels than HOA during virtual beam walking while talking than talking tasks. These findings indicate a decreased ability to allocate additional attentional resources in challenging walking conditions among MS compared with HOA. This study is the first to investigate brain activation dynamics during the performance of balance- and attention-demanding motor tasks in persons with MS.