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Gregor Schöner and John P. Scholz

An important aspect of the study of multi-degree-of-freedom motor control is the analysis of high-dimensional variance data. Through the “uncontrolled manifold” (UCM) approach the structure in such data can be discovered and interpreted. The covariation by randomization (CR) approach provides nonlinear and potentially multi-dimensional measures of covariance. We critically examine these two approaches and compare them relative to the three fundamental issues of choice of variables, choice of model, and adoption of either a geometrical or a correlational view of variance. The UCM approach is a geometrical approach that seeks to discover the structure of variance in multi-degree-of-freedom task spaces in which all degrees of freedom have a common metric. The structure of variance in that space is interpreted in terms of its meaning for task variables. The CR approach seeks to uncover correlations between interpretable elemental variables. It requires a defined and common metric in the space of task variables, but not the elemental variables. Although the CR approach is better suited for systems with strong nonlinearities, variance structure that is not caused by correlation but by different amounts of variance in the different elemental variables is undetected by this approach.

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Caroline Lisee, Tom Birchmeier, Arthur Yan, Brent Geers, Kaitlin O’Hagan, Callum Davis and Christopher Kuenze

the variables were not normally distributed (Table  1 ). Therefore, Spearman rank correlation coefficients were used to evaluate the relationship between the kinetic and audio waveform characteristics. Spearman rank correlation coefficients were interpreted as very weak ( ρ  < .30), weak ( ρ  = .30

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Robert W. Cox, Rodrigo E. Martinez, Russell T. Baker and Lindsay Warren

repeated measures correlation study was designed to determine if the Clinometer Smartphone Application™ would produce equivalent measurements to the Baseline Evaluation Instruments™ 12-1000 plastic goniometer. The University of Idaho Institutional Review Board granted approval for the study. Written

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Theresa L. Miyashita and Paul A. Ullucci

this study was to investigate the cumulative effect of subconcussive impacts on minimum perception time, static visual acuity, gaze stability (GST), and dynamic visual acuity (DVA) scores. The researchers hypothesized a positive correlation between subconcussive impacts and vestibulo-ocular system

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Francisco J. Vera-Garcia, Diego López-Plaza, Casto Juan-Recio and David Barbado

Stable and Unstable Sitting Test) and field settings (Biering-Sørensen Test, 3-Plane Core Strength Test, and Double-Leg Lowering Test). In addition, in order to avoid the potential bias caused by the low consistency of the variables on the correlational analysis, 25 , 26 the relative and absolute

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Kenji Kanazawa, Yoshihiro Hagiwara, Takuya Sekiguchi, Ryo Fujita, Kazuaki Suzuki, Masashi Koide, Akira Ando and Yutaka Yabe

to investigate correlations between ROM and CHL elasticity, by using shear-wave elastography evaluation, in order to verify and expand upon data suggesting that CHL elasticity decreases with age and influences ROM restrictions. Materials and Methods Subjects A total of 84 volunteers (39 men and 45

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Tricia J. Hubbard, John E. Kovaleski and Thomas W. Kaminski

Context:

Measurement reliability is critical when new sports-medicine devices or techniques are developed.

Objective:

To determine the reliability of laxity measurements obtained from an instrumented ankle arthrometer.

Design:

Intratester reliability was examined using a test–retest design, and intertester reliability was assessed using the measurements recorded by 2 different examiners on a separate group of participants.

Setting:

Sports-medicine research laboratory.

Participants:

40 participants with no history of ankle injury, equally divided across the 2 studies.

Measurements:

Laxity measurements included anteroposterior (AP) displacement during loading to 125 N. Inversion–eversion (I–E) rotation was tested during loading to 4000 N-mm. The measures were analyzed using intraclass correlation coefficients (ICCs) and dependent t tests.

Results:

Good to excellent ICCs (.80–.99) for intratester and intertester reliability. A significant difference in measures was observed between testers for both AP displacement and I–E rotation.

Conclusions:

Laxity measurements from an instrumented ankle arthrometer are reliable across test days and examiners

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Adam Culiver, J. Craig Garrison, Kalyssa M. Creed, John E. Conway, Shiho Goto and Sherry Werner

decrease the risk of error. Prior to the study, intrarater reliability was calculated and found to be good for hip abduction (intraclass correlation coefficient [ICC] = .96, 95% CI, .85–.98); hip extension [ICC = .98, 95% CI, .93–.99]); and hip ER (ICC = .87, 95% CI [.59–.97]). Hip strength asymmetry was

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Mehmet Uygur, Goran Prebeg and Slobodan Jaric

We compared two standard methods routinely used to assess the grip force (GF; perpendicular force that hand exerts upon the hand-held object) in the studies of coordination of GF and load force (LF; tangential force) in manipulation tasks. A variety of static tasks were tested, and GF-LF coupling (i.e., the maximum cross-correlation between the forces) was assessed. GF was calculated either as the minimum value of the two opposing GF components acting upon the hand-held object (GFmin) or as their average value (GFavg). Although both methods revealed high GF-LF correlation coefficients, most of the data revealed the higher values for GFavg than for GFmin. Therefore, we conclude that the CNS is more likely to take into account GFavg than GFmin when controlling static manipulative actions as well as that GFavg should be the variable of choice in kinetic analyses of static manipulation tasks.

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John H. Hollman, Kimberly E. Kolbeck, Jamie L. Hitchcock, Jonathan W. Koverman and David A. Krause

Context:

Hip-muscle weakness might be associated with impaired biomechanics and postures that contribute to lower extremity injuries.

Objective:

To examine relationships between hip-muscle strength, Q angle, and foot pronation.

Design:

Correlational study.

Setting:

Academic laboratory.

Participants:

33 healthy adults.

Main Outcome Measures:

Maximal isometric hip abduction (Abd), adduction (Add), external-rotation (ER) and internal-rotation (IR) strength; Q angle of the knee; and longitudinal arch angle of the foot. We analyzed Pearson product– moment (r) correlation coefficients between the Abd/Add and ER/IR force ratios, Q angle, and longitudinal arch angle.

Results:

The hip Abd/Add force ratio was correlated with longitudinal arch angle (r = .35, P = .025).

Conclusions:

Reduced strength of the hip abductors relative to adductors is associated with increased pronation at the foot. Clinicians should be aware of this relationship when examining patients with lower extremity impairments.