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John L. Woodard and Annalise A.M. Rahman

Recent progress in technology has allowed for the development and validation of computer-based adaptations of existing pencil-and-paper neuropsychological measures and comprehensive cognitive test batteries. These computer-based assessments are frequently implemented in the field of clinical sports psychology to evaluate athletes’ functioning postconcussion. These tests provide practical and psychometric advantages over their pencil-and-paper counterparts in this setting; however, these tests also provide clinicians with unique challenges absent in paper-and-pencil testing. The purpose of this article is to present advantages and disadvantages of computer-based testing, generally, as well as considerations for the use of computer-based assessments for the evaluation of concussion among athletes. Furthermore, the paper provides suggestions for further development of computerized assessment of sports concussion given the limitations of the current technology.

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Akinori Nagano, Senshi Fukashiro and Taku Komura

Contribution of series elasticity of the human mm. triceps surae in cyclic heel-raise exercise (similar to hopping but the feet do not leave the floor) was examined via computer modeling and simulation. A two-dimensional skeletal model of the human body was constructed. Upright posture was maintained throughout the simulation to prevent the model from falling. A mathematical representation of the mm. triceps surae was implemented in the skeletal model. The muscle was activated by the neural activation input signal with a time resolution of 0.050 sec. Cyclic heel-raise exercises of cycle duration ranging from 0.300 sec to 0.900 sec, corresponding to the motion frequency of 200 to 66.7 cycles/min, were generated using an optimization approach. The goal of the numerical optimization was to generate cyclic motions with as much range of motion as possible. As a result, realistic heel-raise motions were generated with the range of motion between 0.0023 m (cycle duration = 0.300 sec) and 0.0414 m (cycle duration = 0.900 sec). It was found that contribution of the series elasticity in positive mechanical work output of the muscle-tendon complex during the pushoff phase (from the lowest position to the termination of a cycle) increased as motion frequency increased (3% at 66.7 cycles/min to 47% at 200 cycles/min). Relatively higher muscle activation was found during the downward moving phase when the motion frequency was higher. These tendencies are consistent with the findings reported in preceding studies involving experimental animals as well as human participants. It is suggested that series elasticity plays an integral role in the generation of cyclic human motions.

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Pascal Madeleine

This laboratory study investigated seated computer work before and after prolonged constrained sitting. Discomfort ratings and kinetic and kinematics data were recorded in nine healthy males performing computer work for 5 min before and after 96 min of sitting. The displacement of the center of pressure (CoP) in anterior-posterior and medial-lateral directions and lumbar curvature (LC) were calculated. The root mean square, standard deviation, and sample entropy values were computed from the CoPs and LC signals to assess the magnitude, amount of variability, and regularity of sitting dynamics, respectively. The discomfort increased for the buttocks (p = .02).The standard deviation and sample entropy values of the CoPs and LC signals, respectively, increased (p < .04) and decreased (p < .004) whereas the root mean square remained unchanged (p > .15) after prolonged constrained sitting compared with before. This present study showed that during seated computer work, prolonged constrained sitting affected the amount of variability and the regularity of sitting postural control, whereas the magnitude was not affected. The importance of the dynamics of sitting control may challenge the idea of a static and ideal seated posture at work.

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Jennifer L. Bruno, Zhizhong Li, Matthieu Trudeau, Sachin M. Raina and Jack T. Dennerlein

The goal of this study was to evaluate the performance of a single video camera system for measuring shoulder rotation during computer work, and to quantify the work and postural space within which the system performs optimally. Shoulder rotation angles calculated using the video system were compared with angles calculated using an active infrared LED three-dimensional motion analysis system while 10 adult volunteers simulated postures for two different trials: typical of normal computer work (freestyle) and with forced shoulder abduction (constrained). Average and absolute errors were calculated to determine the accuracy and precision of the system, respectively, for each trial, for each position, and for both the right and left hands. For the right hand, mean values for the average and absolute errors were –1 and 0 degrees, respectively. Only the absolute error increased significantly to 12 degrees for the constrained posture compared with freestyle. During normal computer work, the video system provided shoulder rotation angle values similar to those of a three-dimensional system, thus making it a viable and simple instrument to use in field studies.

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David J. Sanderson

The purpose of this experiment was to assess the efficacy of using real-time generated computer feedback of a selected biomechanical variable, force, for modifying the pattern-of-force application of inexperienced cyclists while they cycled at a steady rate (60 rpm) and power output (approximately 112 watts). Positive results would imply that the technique of using biomechanical variables as augmented feedback could be applied in a learning study in such a way to train for the enhancement of performance of cyclists. This approach differs from the traditional one of using novices performing novel tasks. Even though the cyclists were inexperienced, they nonetheless knew how to cycle and thus modifications of the pattern of force application were made to an already existing complex skill.

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Semyon Slobounov, William Kraemer, Wayne Sebastianelli, Robert Simon and Shannon Poole

The primary purpose of this paper was to demonstrate how modem motion tracking technologies, i.e., the Hock of Birds, and computer visualization graphics may be used in a clinical setting. The idea that joint injury reduces proprioception was investigated, and data for injured subjects were compared to data for noninjured subjects (subjects in all experiments were college students). Two experiments showed that there were no significant losses in joint position sense in knee-injured subjects, and both injured and noninjured groups visually overestimated knee movements. However, injured subjects showed no significant differences when visual reproduction data were compared with actual movement data. In addition, these data indicated that injured subjects may have greater potential for apprehension than noninjured subjects, at least in terms of visual estimation of movement ranges. This is an idea that needs further testing.

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Klaus Schneider and Ronald F. Zernicke

With a validated mathematical model of the head-neck consisting of nine rigid bodies (skull, seven cervical vertebrae, and torso), we simulated head impacts to estimate the injury risk associated with soccer heading. Experimental data from head-linear accelerations during soccer heading were used to validate the nine-body head-neck model for short duration impact loading of the head. In the computer simulations, the mass ratios between head mass and impacting body mass, the velocity of the impacting body, and the impact elasticity were varied. Head-linear and angular accelerations were compared to standard head-injury tolerance levels, and the injury risk specifically related to soccer heading was estimated. Based on our choice of tolerance levels in general, our simulations showed that injury risk from angular head accelerations was greater than from linear head accelerations, and compared to frontal impacts, lateral impacts had greater angular and less linear head accelerations. During soccer heading, our simulations indicated an unacceptable injury risk caused by angular head accelerations for frontal and lateral impacts at relatively low impact velocities for children, and at medium range impact velocities for adults. For linear head accelerations, injury risk existed for frontal and lateral impacts at medium range to relatively larger impact velocities for children, while no injury risk was shown for adults throughout the entire velocity range. For injury prevention, we suggest that head-injury risk can be reduced most substantially by increasing the mass ratio between head and impacting body. In soccer with children, the mass of the impacting body has to be adjusted to the reduced head mass of a child, that is, it must be clearly communicated to parents, coaches, and youngsters to only use smaller soccer balls.

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Alicia M. Kissinger-Knox, Nicole J. Norheim, Denise S. Vagt, Kevin P. Mulligan and Frank M. Webbe

also that athletes (all male) reported more symptoms when the examiner was female versus male, although the group sizes for this comparison were fairly small (N = 20–30). 10 With technological advancements, computer-based assessments have been integrated into the process of concussion evaluation and

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Behzat B. Kentel, Mark A. King and Sean R. Mitchell

A torque-driven, subject-specific 3-D computer simulation model of the impact phase of one-handed tennis backhand strokes was evaluated by comparing performance and simulation results. Backhand strokes of an elite subject were recorded on an artificial tennis court. Over the 50-ms period after impact, good agreement was found with an overall RMS difference of 3.3° between matching simulation and performance in terms of joint and racket angles. Consistent with previous experimental research, the evaluation process showed that grip tightness and ball impact location are important factors that affect postimpact racket and arm kinematics. Associated with these factors, the model can be used for a better understanding of the eccentric contraction of the wrist extensors during one-handed backhand ground strokes, a hypothesized mechanism of tennis elbow.

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Jolene M. Henning, Michelle Lesperance and Jane D. Harris

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