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Carlo Massaroni, Eugenio Cassetta and Sergio Silvestri

Respiratory parameters can be noninvasively evaluated by using motion capture systems. 1 These systems, primarily used in gait analysis, 2 are also capable of measuring tidal volumes and volume changes in standing position by tracking the coordinates of 89 markers placed on the skin

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Gustavo Ramos Dalla Bernardina, Tony Monnet, Heber Teixeira Pinto, Ricardo Machado Leite de Barros, Pietro Cerveri and Amanda Piaia Silvatti

Optoelectronic motion capture systems (MOCAP), such as Vicon (Oxford Metrics Ltd, Oxford, United Kingdom), Elite (BTS, Milan, Italy), Qualisys (Göteborg, Sweden), Motion Analysis (Motion Analysis Corp, Santa Rosa, CA), and OptiTrack (NaturalPoint, Inc, Corvallis, OR), are considered to be the

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Jacob A. Goldsmith, Cameron Trepeck, Jessica L. Halle, Kristin M. Mendez, Alex Klemp, Daniel M. Cooke, Michael H. Haischer, Ryan K. Byrnes, Robert F. Zoeller, Michael Whitehurst and Michael C. Zourdos

position transducers (LPTs) and wearable velocity calculators have been developed, 1 , 2 which have a lower cost (Tendo Weightlifting Analyzer System [TWAS], ∼$1500; GymAware, ∼$2000) than criterion measurement systems: force platforms and 3-dimensional motion capture ($10,000–40,000). In terms of

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Aurel Coza, Benno M. Nigg and Ladina Fliri

Soft-tissue vibrations can be used to quantify selected properties of human tissue and their response to impact. Vibrations are typically quantified using high-speed motion capture or accelerometry. The aim of this study was to compare the amplitude and frequency of soft-tissue vibrations during running when quantified by highspeed motion capture and accelerometry simultaneously. This study showed: (a) The estimated measurement errors for amplitude and frequency were of the same order of magnitude for both techniques. (b) There were no significant differences in the mean peak frequencies and peak amplitudes measured by the two methods. (c) The video method showed an inability to capture high frequency information. This study has shown that a tradeoff has to be made between the accuracy in amplitude and frequency when these methods are employed to quantify soft tissue vibrations in running.

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Saryn R. Goldberg, Thomas M. Kepple and Steven J. Stanhope

We increased the accuracy of an instrumented treadmill’s measurement of center of pressure and force data by calibrating in situ and optimizing the transformation between the motion capture and treadmill force plate coordinate systems. We calibrated the device in situ by applying known vertical and shear loads at known locations across the tread surface and calculating a 6 × 6 calibration matrix for the 6 output forces and moments. To optimize the transformation, we first estimated the transformation based on a locating jig and then measured center-of-pressure error across the treadmill force plate using the CalTester tool. We input these data into an optimization scheme to find the transformation between the motion capture and treadmill force plate coordinate systems that minimized the error in the center-of-pressure measurements derived from force plate and motion capture sources. When the calibration and transformation optimizations were made, the average measured error in the center of pressure was reduced to approximately 1 mm when the treadmill was stationary and to less than 3 mm when moving. Using bilateral gait data, we show the importance of calibrating these devices in situ and performing transformation optimizations.

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Dominic Thewlis, Chris Bishop, Nathan Daniell and Gunther Paul

The objective quantification of three-dimensional kinematics during different functional and occupational tasks is now more in demand than ever. The introduction of new generation of low-cost passive motion capture systems from a number of manufacturers has made this technology accessible for teaching, clinical practice and in small/medium industry. Despite the attractive nature of these systems, their accuracy remains unproved in independent tests. We assessed static linear accuracy, dynamic linear accuracy and compared gait kinematics from a Vicon MX-f20 system to a Natural Point OptiTrack system. In all experiments data were sampled simultaneously. We identified both systems perform excellently in linear accuracy tests with absolute errors not exceeding 1%. In gait data there was again strong agreement between the two systems in sagittal and coronal plane kinematics. Transverse plane kinematics differed by up to 3° at the knee and hip, which we attributed to the impact of soft tissue artifact accelerations on the data. We suggest that low-cost systems are comparably accurate to their high-end competitors and offer a platform with accuracy acceptable in research for laboratories with a limited budget.

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Brad W. Willis, Katie Hocker, Swithin Razu, Aaron D. Gray, Marjorie Skubic, Seth L. Sherman, Samantha Kurkowski and Trent M. Guess

reinjury and demonstrate increased rates of knee pain and prevalence of osteoarthritis. 1 – 4 Investigations into preventive screening techniques monitoring ACL injury risk factors aimed at mitigating female injury rates are warranted. 1 , 2 The use of 3-dimensional marker-based motion capture systems in

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James R. Cook, Nancy A. Baker, Rakié Cham, Erin Hale and Mark S. Redfern

A marker-based kinematic hand model to quantify finger postures was developed and compared to manual goniometric measurements. The model was implemented with data collected from static postures of five subjects. The metacarpal phalangeal (MCP) and proximal interphalangeal (PIP) joints were positioned in flexion of approximately 30, 60, and 90 degrees for 5 subjects. Wrist flexion/extension and ulnar/radial deviations were also examined. The model-based angles for the MCP and PIP joints were not statistically equivalent to the goniometric measurements, with differences of −1.8 degrees and +3.5 degrees, respectively. Differences between the two measurement methods for the MCP and PIP were found to be a function of the posture (i.e., 150, 120, or 90 degree blocks) used. Wrist measurements differed by −4.0 degrees for ulnar/radial deviation and +5.2 degrees for flexion/extension. Much of the difference between the model and goniometric measurements is believed due to inaccuracies in the goniometric measurements. The proposed model is useful for future investigations of finger-intensive activities by supplying accurate and unbiased measures of joint angles.

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M. A. Urbin, David Stodden and Glenn Fleisig

Individual body segment actions evolve during throwing skill development. Maximal trunk involvement is typically the last feature of the movement pattern to fully develop. The current study examined developmental levels of trunk action and the associated variability in the throwing motion. The throwing motions of children and adolescents were analyzed via motion capture and trunk actions were classified as exhibiting no rotation (n = 7), blocked rotation (n = 6), or differentiated rotation (n = 11). Results indicated nonrotators exhibited greater variability than blocked-rotators in maximum humeral external rotation and humeral horizontal adduction angles at ball release; nonrotators also demonstrated greater variability than differentiated-rotators on these parameters, in addition to forward trunk tilt and elbow extension angle at ball release. Nonrotators produced more variable peak upper torso and humeral horizontal adduction angular velocities, as well as peak upper torso linear velocity, relative to differentiated-rotators. Blocked-rotators produced more variable peak pelvis, upper torso, and humeral horizontal adduction angular velocities, as well peak pelvis linear velocity, relative to differentiated-rotators. Nonrotators were less consistent relative to blocked- and differentiated-rotators in the time that elapsed from peak pelvis angular velocity to ball release. These results indicate that greater trunk involvement is associated with more consistent movement production.

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Basilio Pueo, Patrycja Lipinska, José M. Jiménez-Olmedo, Piotr Zmijewski and Will G. Hopkins

Vertical-jump tests are commonly used to evaluate lower-limb power of athletes and nonathletes. Several types of equipment are available for this purpose.

Purpose:

To compare the error of measurement of 2 jump-mat systems (Chronojump-Boscosystem and Globus Ergo Tester) with that of a motion-capture system as a criterion and to determine the modifying effect of foot length on jump height.

Methods:

Thirty-one young adult men alternated 4 countermovement jumps with 4 squat jumps. Mean jump height and standard deviations representing technical error of measurement arising from each device and variability arising from the subjects themselves were estimated with a novel mixed model and evaluated via standardization and magnitude-based inference.

Results:

The jump-mat systems produced nearly identical measures of jump height (differences in means and in technical errors of measurement ≤1 mm). Countermovement and squat-jump height were both 13.6 cm higher with motion capture (90% confidence limits ±0.3 cm), but this very large difference was reduced to small unclear differences when adjusted to a foot length of zero. Variability in countermovement and squat-jump height arising from the subjects was small (1.1 and 1.5 cm, respectively, 90% confidence limits ±0.3 cm); technical error of motion capture was similar in magnitude (1.7 and 1.6 cm, ±0.3 and ±0.4 cm), and that of the jump mats was similar or smaller (1.2 and 0.3 cm, ±0.5 and ±0.9 cm).

Conclusions:

The jump-mat systems provide trustworthy measurements for monitoring changes in jump height. Foot length can explain the substantially higher jump height observed with motion capture.