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Julia Freedman Silvernail, Richard E.A. van Emmerik, Katherine Boyer, Michael A. Busa and Joseph Hamill

patterns for joint tissue. A variety of methods have been used to examine coordination and its variability. One method that has been used to investigate the temporal–spatial movement coordination is the modified vector coding technique. 1 Vector coding analyses (VC) provide information on the underlying

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Pedro Rodrigues, Ryan Chang, Trampas TenBroek, Richard van Emmerik and Joseph Hamill

Excessive pronation, because of its coupling with tibial internal rotation (TIR), has been implicated as a risk factor in the development of anterior knee pain (AKP). Traditionally, this coupling has been expressed as a ratio between the eversion range of motion and the TIR range of motion (Ev/TIR) that occurs during stance. Currently, this technique has not been used to evaluate specific injuries or the effects of sex. In addition, Ev/TIR is incapable of detecting coupling changes that occur throughout stance. Therefore, the purpose of this study was to compare the coupling between eversion and TIR in runners with (n = 19) and without AKP (n = 17) and across sex using the Ev/TIR ratio, and more continuously using vector coding. When using vector coding, significant coupling differences were noted in runners with AKP (34% to 38% stance), with runners with AKP showing relatively more TIR than eversion. Similarly significant differences were noted across sex (14%–25% and 36%–47% stance), with males transitioning from a loading to propulsive coordination pattern using a proximal to distal strategy, and female runners using a distal to proximal strategy. These differences were only detected when evaluating this coupling relationship using a continuous technique such as vector coding.

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Dejan Tepavac and Edelle Carmen Field-Fote

The evaluation of a vector coding technique to quantify intersegmental coupling within a limb over multiple cycles of walking is described. The angular position of the knee with respect to the hip during walking was examined based on relative motion plots generated from videographic data. Participants included one able-bodied individual and one with spinal cord injury; the latter was assessed before and after participating in an assisted walking program. Vector coding of the frame-to-frame changes in hip/knee relationship was used to quantify the relative motion plots. Vector analysis techniques were then used to produce a single value that represents the overall variability of the hip/knee coupling relationship over multiple cycles. Hypothetical and random data were also used to evaluate the coding algorithm. In addition, the technique was compared to an earlier method in the analysis of this same data. Vector coding provided an easily interpretable method of quantifying the intersegmental coupling relationships and assessing the degree of consistency in the intralimb coordination over multiple cycles. The measure is sensitive to change in the kinematic variables and appears to have good validity. In addition, this technique has advantages over prior techniques as it allows simultaneous comparison of multiple cycles, calculations are performed quickly, and the algorithm is easy to program.

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Hai-Jung Steffi Shih, Danielle N. Jarvis, Pamela Mikkelsen and Kornelia Kulig

(vGRFs) of the 2 legs individually may serve as the representation of bilateral limb–loading behavior. The relationship between bilateral vGRF can be investigated through vector coding analyses, which have been successfully used in quantifying interjoint and intersegment kinematic coordination. 10 – 17

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Eric Foch and Clare E. Milner

. The plots were divided into 2 periods of stance 10 : braking phase (heel-strike–peak vertical ground reaction force) and propulsive phase (peak vertical ground reaction force–toe-off). Coupling angles were quantified using a vector coding analysis as described by Needham et al. 24 Coupling angles were

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Ben Langley, Nick Knight and Stewart C. Morrison

MTSS and healthy cohorts. Exploration of joint coupling has previously been proposed and utilized as a means of evaluating injury etiology 13 and may help to elucidate potential mechanisms for the development of MTSS. Relatively recent advancements in vector coding techniques 14 – 16 enable the

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Yumeng Li, Rumit S. Kakar, Marika A. Walker, Yang-Chieh Fu, Timothy S. Oswald, Cathleen N. Brown and Kathy J. Simpson

the vector coding method could quantify the spatial coordination. 18 – 20 The vector coding method calculates the angle of the vector between adjacent data points in time on the angle-angle diagram, thus supplying spatial coordination information as well as movement dominancy of 1 segment over the

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Michael A. Samaan, Matthew C. Hoch, Stacie I. Ringleb, Sebastian Bawab and Joshua T. Weinhandl

The aim of this study was to determine the effects of hamstrings fatigue on lower extremity joint coordination variability during a sidestep cutting maneuver. Twenty female recreational athletes performed five successful trials of a sidestep cutting task preand postfatigue. Each participant completed an isolated hamstrings fatigue protocol consisting of isokinetic maximum effort knee flexion and passive extension contractions. Vector coding was used to examine hip and knee joint couplings (consisting of various planar motions) during the impact and weight acceptance phases of the sidestep cut stance phase. Paired t tests were used to analyze differences of each phase as an effect of fatigue, where alpha was set a priori at .05. The hip rotation/knee rotation coupling exhibited a significant decrease in coordination variability as a function of fatigue in both the impact (P = .015) and weight acceptance phases (P = .043). Similarly, the hip adduction-abduction/knee rotation coupling exhibited a significant decrease in coordination variability in the weight acceptance phase (P = .038). Hamstrings fatigue significantly decreased coordination variability within specific lower extremity joint couplings that included knee rotation. Future studies should be conducted to determine if this decrease in coordination variability is related to lower extremity injury mechanisms.

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Danielle N. Jarvis, Jo Armour Smith and Kornelia Kulig

Variability, or how a task changes across trials, may reveal differences between athletes of differing skill levels. The purpose of this study was to examine trunk and lower extremity (LE) single joint kinematic variability and intersegmental coordination variability in dancers and nondancers during bipedal vertical dance jumps (sautés). Twenty healthy females, 10 with no formal dance training and 10 professional dancers, performed 20 consecutive sautés. Single joint kinematic variability was assessed using mean standard deviation of angular displacement, and intersegmental coordination variability was assessed using angular deviation of the coupling angle between segments. Within the context of the standard error of measure, there was no difference in single joint kinematic variability between dancers and nondancers. Intersegmental coordination variability in the trunk was higher than variability in LE couplings for both groups. Dancers had lower intersegmental coordination variability than nondancers for LE sagittal, frontal, and transverse plane couplings, and sagittal plane trunk couplings. Trunk adjustments may be important for successful performance, but lower intersegmental coordination variability in expert dancers indicates a higher level of control. Trunk coordination and postural control may be important factors to investigate in skilled athletes.

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Jebb G. Remelius, Joseph Hamill, Jane Kent-Braun and Richard E.A. Van Emmerik

Individuals with multiple sclerosis (MS) often have poor balance control that is especially apparent during dynamic tasks such as gait initiation (GI). The purpose of this study was to investigate how balance symptoms due to MS alter spatiotemporal variables, coordination, and temporal margins within the stability boundary during gait initiation. Twelve women with MS (Expanded Disability Status Scale [EDSS] mean = 4.0, SD = 1.4) and 12 women without MS (control group) initiated gait at their preferred speed. MS participants attained a slower anterior velocity because of smaller anterior center of mass displacements and took longer to complete the initiation of gait than the control group. MS participants exhibited a smaller posterior shift in center of pressure during GI and stepped with a longer dual support time than the control group. However, these changes may be due to differences in initiation velocity. Relative timing analysis showed invariance in postural and locomotor phases of gait initiation between groups. The MS group showed different coordination between anterior-posterior and medio-lateral center of pressure components while increasing temporal margins to the posterior and lateral stability boundaries in comparison with the control group. Overall, during gait initiation at their preferred speed the MS participants adopted a functional strategy that produces lower speed and reduced proximity to the stability boundaries prior to stepping.