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Alexander Nazareth, Nicole M. Mueske and Tishya A.L. Wren

This study aimed to determine the effect of tibia marker placement on walking kinematics in children with pathological gait. Three-dimensional lower extremity gait data were collected using both a traditional tibia wand (protruding laterally from the distal shank) and a tibia crest marker on 25 children with pathological gait. Kinematic variables during walking and quiet standing were calculated using each marker and the “Plug-in Gait” implementation of the conventional gait model. For walking, average differences in kinematics between tibia markers ranged from 0.1° to 1.9° at the knee and ankle, except in the transverse plane where differences were 6.0° to 7.2°. No significant differences were found during quiet standing, indicating that differences in kinematics derive primarily from dynamic sources, which likely affect the tibia wand more than the tibia crest marker. These results suggest that the tibia crest marker can be used in place of the traditional tibia wand in clinical gait analysis.

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Cale Jacobs and Carl Mattacola

Context:

Decelerating movements such as landing from a jump have been proposed to be a common mechanism of injury to the anterior cruciate ligament (ACL).

Objective:

To compare eccentric hip-abductor strength and kinematics of landing between men and women when performing a hopping task.

Setting:

Research laboratory.

Patients:

18 healthy subjects (10 women, 8 men).

Main Outcome Measures:

Eccentric peak torque of the hip abductors and peak knee-joint angles during a 350-millisecond interval after impact.

Results:

No significant sex differences were present, but there was a significant inverse relationship between women's eccentric peak torque and peak knee-valgus angle (r = –.61, P = .03).

Conclusions:

Women with larger eccentric peak torque demonstrated lower peak knee-valgus angles. By not reaching as large of a valgus angle, there is potentially less stress on the ACL. Increasing eccentric hip-abductor strength might improve knee-joint kinematics during landing from a jump.

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Takayuki Hasegawa, Toshiro Otani, Kentaro Takeda, Hideo Matsumoto, Kengo Harato, Yoshiaki Toyama and Takeo Nagura

The purpose of the current study was to longitudinally evaluate how preoperative knee kinematics change after ACL reconstruction. Three-dimensional gait analysis using the point cluster method was undertaken on the same subjects preoperatively and at 3, 6, and 12 months after ACL reconstructive surgery. Thirteen subjects (7 males, 6 females) were examined while performing 2 different activities at self-selected speeds: walking and walk-pivoting (walking, pivoting toward the landed limb side and walking away). The contralateral knees of subjects at 12 months postoperatively were selected as control knees. Flexion range in the stance phase increased with time after surgery, but remained lower than in the contralateral knee, even at 12 months postoperatively (P < .05) during walking and walk-pivoting. The rotation pattern during walking and walk-pivoting showed an offset toward external rotation by 6 months postoperatively compared with control knees, while at 12 months postoperatively the offset had nearly disappeared and the movement pattern resembled that in control knees. These findings suggest that a return to sport participation by 6 months after ACL reconstruction requires careful consideration. Depending on the type of sport, activity restriction even after 12 months may need to be considered to allow complete kinematic restoration.

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Wen-Hao Hsu, Evelyn J. Park, Daniel L. Miranda, Hani M. Sallum, Conor J. Walsh and Eugene C. Goldfield

This study examines how adults apply forces to regulate new walkers’ body sway directions while assisting them in standing and initiating their first steps. Eight healthy, typically developing young children who could stand independently and walk a few steps with an adult’s support participated in this study and were included for data analyses. Adults wore instrumented force gloves and placed their hands on their child’s hips to assist them in standing, then released glove contact with their child to allow their child to initiate walking. Using the glove force profiles, three phases (Stabilization, Relaxation, and Initiation) of adults’ support were determined. Results showed that adults gradually reduced their assistance in both the antero-posterior (AP) and mediolateral (ML) directions, before releasing their hands. They also influenced the directionality of their child’s center of mass (CoM) so that it was in the AP rather than ML direction. Furthermore, the behavior of the child’s CoM in the ML direction during the Initiation Phase was related to the latency with which the child initiated the first step. These findings support the view that adults play a role in modulating the directionality of the child’s body motion by transforming body sway into gait initiation.

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Christoph Schütz, Matthias Weigelt, Dennis Odekerken, Timo Klein-Soetebier and Thomas Schack

Previous studies on sequential effects of human grasping behavior were restricted to binary grasp type selection. We asked whether two established motor control strategies, the end-state comfort effect and the hysteresis effect, would hold for sequential motor tasks with continuous solutions. To this end, participants were tested in a sequential (predictable) and a randomized (nonpredictable) perceptual-motor task, which offered a continuous range of posture solutions for each movement trial. Both the end-state comfort effect and the hysteresis effect were reproduced under predictable, continuous conditions, but only the end-state comfort effect was present under nonpredictable conditions. Experimental results further revealed a work range restriction effect, which was reproduced for the dominant and the nondominant hand.

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Joseph Myers, John Jolly, Takashi Nagai and Scott Lephart

Context:

In vivo scapular kinematics during humeral movements are commonly assessed with electromagnetic tracking devices despite few published data related to reliability and precision of these measurements.

Objective:

To determine the intrasession reliability and precision of assessing scapular kinematics using an electromagnetic tracking device.

Design:

Scapular position and orientation were measured with an electromagnetic tracking device during humeral elevation/depression in several planes. Intrasession reliability and precision were established by comparing 2 trials performed in succession.

Setting:

A human-movement research laboratory.

Participants:

15 healthy individuals.

Main Outcome Measures:

Intrasession intraclass correlation coefficients and standard error of measurement of all scapular variables were established.

Results:

The mean intrasession reliability for all variables was ICC = .97 ± .03. The mean intrasession precision was .99° ± .36°.

Conclusions:

In vivo scapular kinematics can be measured with high reliability and precision during intrasession research designs.

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Kevin J. McQuade, Margaret A. Finley, Michelle Harris-Love and Sandra McCombe-Waller

The use of magnetic tracking technology has become increasingly popular in recent years for human motion studies. However, there have been few independent evaluations of how these systems perform. The purpose of this study was to develop a dynamic pendulum calibration method to test the performance of magnetic tracking sensors. A nonmetallic pendulum was constructed and instrumented with a rotary potentiometer. A cube was attached to the distal end of the pendulum so that sensors could be mounted orthogonally. In this manner, it was possible to obtain simultaneous recordings of azimuth, elevation, and roll depending on the sensor mounting orientation relative to the axis of rotation of the pendulum. Sensor data, using Flock of Birds™ sensors, and potentiometer data were collected simultaneously during dynamic pendulum motion at two transmitter distances and then were compared. The results showed excellent trial-to-trial repeatability of 2% or better for the sensors, and high correlations between the sensor and potentiometer data. RMS errors range from about 3 to 10 mm depending on the angular velocity of the pendulum. Angular errors were less than 1 degree RMS for all speeds.

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Robert J. Aughey

Background:

Australian football (AF) is a highly intermittent sport, requiring athletes to accelerate hundreds of times with repeated bouts of high-intensity running (HIR). Players aim to be in peak physical condition for finals, with anecdotal evidence of increased speed and pressure of these games.

Purpose:

However, no data exists on the running demands of finals games, and therefore the aim of this study was to compare the running demands of finals to regular season games with matched players and opponents.

Methods:

Player movement was recorded by GPS at 5 Hz and expressed per period of the match (rotation), for total distance, high-intensity running (HIR, 4.17-10.00 m·s-1) and maximal accelerations (2.78-10.00 m·s–2). All data was compared for regular season and finals games and the magnitude of effects was analyzed with the effect size (ES) statistic and expressed with confidence intervals.

Results:

Each of the total distance (11%; ES: 0.78 ± 0.30), high-intensity running distance (9%; ES: 0.29 ± 0.25) and number of maximal accelerations (97%; ES: 1.30 ± 0.20) increased in finals games. The largest percentage increases in maximal accelerations occurred from a commencement velocity of between 3–4 (47%; ES: 0.56 ± 0.21) and 4–5 m·s-1 (51%; ES: 0.72 ± 0.26), and with <19 s between accelerations (53%; ES: 0.63 ± 0.27).

Conclusion:

Elite AF players nearly double the number of maximal accelerations in finals compared with regular season games. This large increase is superimposed on requirements to cover a greater total distance and spend more time at high velocity during finals games. Players can be effectively conditioned to cope with these increased demands, even during a long competitive season.

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Chris Richter, Noel E. O’Connor, Brendan Marshall and Kieran Moran

The aim of this study is to propose a novel data analysis approach, an analysis of characterizing phases (ACP), that detects and examines phases of variance within a sample of curves utilizing the time, magnitude, and magnitude-time domains; and to compare the findings of ACP to discrete point analysis in identifying performance-related factors in vertical jumps. Twenty-five vertical jumps were analyzed. Discrete point analysis identified the initial-to-maximum rate of force development (P = .006) and the time from initial-to-maximum force (P = .047) as performance-related factors. However, due to intersubject variability in the shape of the force curves (ie, non-, uni- and bimodal nature), these variables were judged to be functionally erroneous. In contrast, ACP identified the ability to apply forces for longer (P < .038), generate higher forces (P < .027), and produce a greater rate of force development (P < .003) as performance-related factors. Analysis of characterizing phases showed advantages over discrete point analysis in identifying performance-related factors because it (i) analyses only related phases, (ii) analyses the whole data set, (iii) can identify performance-related factors that occur solely as a phase, (iv) identifies the specific phase over which differences occur, and (v) analyses the time, magnitude and combined magnitude-time domains.

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Timothy J. Koh, Mark D. Grabiner and John J. Brems

Shoulder kinematics, including scapular rotation relative to the trunk and humeral rotation relative to the scapula, were examined during humeral elevation in three vertical planes via video analysis of intracortical pins. Helical axis parameters provided an easily interpretable description of shoulder motion not subject to the limitations associated with Cardan/Euler angles. Between 30 and 150° of elevation in each plane, the scapula rotated almost solely about an axis perpendicular to the scapula. Additional scapular rotation appeared to support the notion that the scapula moves “toward” the plane of elevation. Humeral rotation took place mainly in the plane of the scapula independent of the plane of elevation. Many parameters of shoulder complex kinematics were quite similar across all planes of elevation, suggesting a consistent movement pattern with subtle differences associated with the plane of elevation.