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Zachary Merrill, Grace Bova, April Chambers, and Rakié Cham

Body segment parameters (BSPs), such as segment length, mass, center of mass (COM), and radius of gyration, are commonly used as inputs in ergonomic applications, 1 as well as biomechanical models used to estimate the risk of musculoskeletal injuries during lifting and gait. 2 – 5 Specific

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Doris I. Miller and Eric J. Sprigings

Major factors influencing the ability of divers to perform nontwisting springboard dives of increasing degree of difficulty were investigated. The analysis was based upon 49 dives (42 in pike and 7 in tuck) executed by male and female medalists in the 1996 Olympics. Videotapes were digitized to determine competitors’ vertical velocities and angular momenta at the beginning of dive flight. Centripetal force and resultant joint torque models were used to estimate the effort needed to perform multiple somersaulting dives. Increasing degree of difficulty by spinning in a pike rather than a tuck position for the same number of somersaults was associated with decreased vertical velocity at the start of dive flight, decreased angular velocity while somersaulting in a quasi-rigid position, and little change in centripetal force or related muscular effort. Increasing degree of difficulty by adding a somersault while rotating in a tuck rather than a pike position involved increases in vertical and angular velocities, a smaller increase in angular momentum, and notable increases in resultant joint torque and centripetal force. Sufficient muscular torque to maintain a compact spinning position was considered to be the major additional challenge facing divers making the transition from a 21/2 pike to a 31/2 tuck.

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Sara L. Arena, Kelsey McLaughlin, Anh-Dung Nguyen, James M. Smoliga, and Kevin R. Ford

Athletic individuals may differ in body segment inertial parameter (BSIP) estimates due to differences in body composition, and this may influence calculation of joint kinetics. The purposes of this study were to (1) compare BSIPs predicted by the method introduced by de Leva1 with DXA-derived BSIPs in collegiate female soccer players, and (2) examine the effects of these BSIP estimation methods on joint moment and power calculations during a drop vertical jump (DVJ). Twenty female NCAA Division I soccer players were recruited. BSIPs of the shank and thigh (mass, COM location, and radius of gyration) were determined using de Leva’s method and analysis of whole-body DXA scans. These estimates were used to determine peak knee joint moments and power during the DVJ. Compared with DXA, de Leva’s method located the COM more distally in the shank (P = .008) and more proximally in the thigh (P < .001), and the radius of gyration of the thigh to be further from the thigh COM (P < .001). All knee joint moment and power measures were similar between methods. These findings suggest that BSIP estimation may vary between methods, but the impact on joint moment calculations during a dynamic task is negligible.

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Robert K. Jensen, Tina Treitz, and Sylvie Doucet

The purpose of this study was to develop prediction equations to estimate mass, radius to the center of mass (CM), and principal moments of the segments during pregnancy. Nonlinear regression equations were determined for the lower trunk, upper trunk, and thigh. The third sampling month of a longitudinal study was used (Sample 1, n = 15). The nonlinear regressions were then used to predict segment inertias above and below the third sampling month (Sample 2, the remaining 74 measurements). For the remaining segments, body mass and segment lengths were used as predictor variables for mass, radius to CM, and radius of gyration about the centroidal axes. The remaining seven segments did not change substantially during pregnancy, and the means of the repeated measures were used for the simple linear regressions. Eighteen of the 28 regressions and all of the CM regressions were significant. With pregnant subjects it is recommended that these regressions be used if application of the elliptical cylinder model is not possible.

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April J. Chambers, Alison L. Sukits, Jean L. McCrory, and Rakié Cham

Age, obesity, and gender can have a significant impact on the anthropometrics of adults aged 65 and older. The aim of this study was to investigate differences in body segment parameters derived using two methods: (1) a dual-energy x-ray absorptiometry (DXA) subject-specific method (Chambers et al., 2010) and (2) traditional regression models (de Leva, 1996). The impact of aging, gender, and obesity on the potential differences between these methods was examined. Eighty-three healthy older adults were recruited for participation. Participants underwent a whole-body DXA scan (Hologic QDR 1000/W). Mass, length, center of mass, and radius of gyration were determined for each segment. In addition, traditional regressions were used to estimate these parameters (de Leva, 1996). A mixed linear regression model was performed (α = 0.05). Method type was significant in every variable of interest except forearm segment mass. The obesity and gender differences that we observed translate into differences associated with using traditional regressions to predict anthropometric variables in an aging population. Our data point to a need to consider age, obesity, and gender when utilizing anthropometric data sets and to develop regression models that accurately predict body segment parameters in the geriatric population, considering gender and obesity.

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Shohei Shibata, Yuki Inaba, Shinsuke Yoshioka, and Senshi Fukashiro

) and the radius of gyration ( r ) were calculated as follows ( Goto, Yamamoto, & Kamiyoshi, 1971 ): I = l 2 12 m F , (2) r = I / m F . (3) Table 1 Inertial Parameters of Both Conventional Model and Finger Model Endpoints Radii of Gyration Segment Origin Other Mass (kg) COM (%) x axis (%) y axis

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Susan Park, Lindsay P. Toth, Scott E. Crouter, Cary M. Springer, Robert T. Marcotte, and David R. Bassett

manufacturer’s recommended wrist placement site. During ambulation and activities of daily living, monitors worn on the wrist/forearm move around a joint (e.g., the shoulder and elbow). For monitors worn closer to the wrist (i.e., position A), the radius of gyration around the shoulder or elbow is longer than

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Daniel W. Sample, Tanner A. Thorsen, Joshua T. Weinhandl, Kelley A. Strohacker, and Songning Zhang

center of mass locations, radius of gyrations, and moment of inertia-related anthropometric parameters. When working with obese populations, it is common to not normalize GRF and joint moment data by body weight and body mass, respectively, as doing so will limit the obesity effects on the joint kinetics