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  • Author: James G. Richards x
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Edward J. Quigley and James G. Richards

This study investigated the mechanical effects that cycling has on running style which may explain the discomfort associated with the transition from cycling to running. The joint angles, angular velocities, reaction forces, and reaction moments of the left and right hip, knee, and ankle joints as well as stance time, flight time, stride length, and maximum vertical displacement of the center of gravity were measured using high-speed video and ground reaction force data. Data were collected from 11 competitive biathletes and triathletes. Each subject's running mechanics were determined from 10 trials for each of three conditions: (a) unfatigued, (b) immediately following 30 min of running, and (c) immediately following 30 min of bicycling. The results indicate that a person's running mechanics, as described by the variables above, are virtually unchanged between each of the three conditions. Therefore, awkwardness of the bicycle-to-run transition may not be related to a change in running mechanics.

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Dustin A. Bruening and James G. Richards

Lower extremity injuries in figure skating have long been linked to skating boot stiffness, and recent increases in jump practice time may be influencing the frequency and seriousness of these injuries. It is hypothesized that stiff boots compromise skaters' abilities to attenuate jump landing forces. Decreasing boot stiffness by adding an articulation at the ankle may reduce the rate and magnitude of landing forces. Prototype articulated figure skating boots were tested in this study to determine their effectiveness in enabling skaters to land with lower peak impact forces. Nine competitive figure skaters, who trained in standard boots and subsequently in articulated boots, performed off-ice jump simulations and on-ice axels, double toe loops, and double axels. Analysis of the off-ice simulations showed decreases in peak heel force and loading rate with use of the articulated boot, although the exact kinematic mechanisms responsible for these decreases are still unclear. Analysis of the on-ice jumps revealed few kinematic differences between boot types, implying that the skaters did not use the articulation. Greater adaptation and training time is likely needed for the results seen off-ice to transfer to difficult on-ice jumps.

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Elisa S. Arch, Sarah Colón and James G. Richards

Breast and bra motion research aims to understand how the breasts/bra move to aid development of apparel that minimizes motion. Most previously published research has tracked nipple motion to represent bra motion. However, this method does not provide information regarding regional tissue motion. A more comprehensive approach might facilitate understanding how the entire soft-tissue mass moves during physical activities. This study developed and tested an objective method to comprehensively measure 3-dimensional bra motion, including regional displacement and velocity, displacement phasing, and surface stretch. To test the method, 6 females were fitted with a minimally supportive, seamless bra (small bra n = 3; large bra n = 3). Data were collected as participants ran on a treadmill. Results indicated marker displacement, velocity, link stretch, and link stretch velocities reached as high as 52.6 (6.8) mm, 504.8 (88.7) mm/s, 29.5% (7.1%) of minimum length, and 3.8 (1.0) mm/s/mm, respectively, with the large bra having greater motions compared with the small. Most bra motion occurred above/below the nipple region and at the bra’s strap–body interface, independent of bra size. Importantly, maximum marker displacement and velocity did not occur at the nipple. Measurements obtained from this new method may be important for designing innovative clothing that minimizes bra motion during physical activity.

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Daniel P. Buckalew, David A. Barlow, James W. Fischer and James G. Richards

Extensive study has been done on male subjects dealing with gait analysis, but similar investigations of women runners are limited. The purpose of this study was to quantify the essential characteristics and alterations in gait mechanics of women marathoners. Forty elite women marathoners were filmed at four camera locations during the first U.S. Olympic Women's Marathon Trial. Data were quantified with a microcomputer and digitizing system. Quantification of 11 kinematic and temporal variables of gait were obtained. Five variables were examined bilaterally to determine degree of symmetry. Results showed remarkably consistent characteristics of gait across the four camera locations. However, substantial changes did occur between the third and fourth camera locations in stride length and horizontal velocity. All subjects displayed little asymmetry throughout the race. Minimal differences between the top and bottom 10 finishers were noted. There are differences between the gait patterns of men and women distance runners. Stride length, support/nonsupport time ratio, and percent overstride appear to be important factors for success of women distance runners. Most alterations in gait mechanics appear to occur between the 20- and 24-mile marks of the marathon.

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R. Tyler Richardson, Elizabeth A. Rapp, R. Garry Quinton, Kristen F. Nicholson, Brian A. Knarr, Stephanie A. Russo, Jill S. Higginson and James G. Richards

Musculoskeletal modeling is capable of estimating physiological parameters that cannot be directly measured, however, the validity of the results must be assessed. Several models utilize a scapular rhythm to prescribe kinematics, yet it is unknown how well they replicate natural scapular motion. This study evaluated kinematic errors associated with a model that employs a scapular rhythm using 2 shoulder movements: abduction and forward reach. Two versions of the model were tested: the original MoBL ARMS model that utilizes a scapular rhythm, and a modified MoBL ARMS model that permits unconstrained scapular motion. Model estimates were compared against scapulothoracic kinematics directly measured from motion capture. Three-dimensional scapulothoracic resultant angle errors associated with the rhythm model were greater than 10° for abduction (mean: 16.4°, max: 22.4°) and forward reach (mean: 11.1°, max: 16.5°). Errors generally increased with humerothoracic elevation with all subjects reporting greater than 10° differences at elevations greater than 45°. Errors associated with the unconstrained model were less than 10°. Consequently, use of the original MoBL ARMS model is cautioned for applications requiring precise scapulothoracic kinematics. These findings can help determine which research questions are suitable for investigation with these models and assist in contextualizing model results.

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Kristen F. Nicholson, Stephanie A. Russo, Scott H. Kozin, Dan A. Zlotolow, Robert L. Hulbert, K. Michael Rowley and James G. Richards

Several studies have described using an acromion marker cluster for measuring scapular orientation in healthy adults performing planar motions. It is unknown whether the acromion marker cluster method will provide the same level of accuracy in children with brachial plexus birth palsy. This study compared this method to palpation for calculating scapular orientation in children with brachial plexus birth palsy performing clinically relevant movements. Scapular orientation in ten patients was determined by palpation and an acromion marker cluster in neutral and six Modified Mallet positions. RMSEs and mean relative errors were calculated. Resultant RMSEs ranged from 5.2 degrees to 21.4 degrees. The averages of the mean relative errors across all positions for each axis were 177.4% for upward/downward rotation, 865.0% for internal/external rotation, and 166.2% for anterior/posterior tilt. The acromion marker cluster method did not accurately measure scapular rotation relative to the total movement on an individual or group basis in the population. With most relative errors over 100%, the acromion marker cluster method often produced errors larger than the actual measured motion. The accuracy of the acromion marker cluster method limits its use as a clinical tool for measuring scapular kinematics on children with brachial plexus birth palsy.