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Suvobrata Mitra, Polemnia G. Amazeen and Michael T. Turvey

We investigated the 1:1 frequency locking of two hand-held pendulums oscillated parallel to the body's coronal plane. In this configuration, anti-phase defined muscularly is in-phase defined spatially, and vice versa. Coordination equilibria measured by average relative phase were shifted less from muscular anti-phase than from muscular in-phase by detuning (unequal uncoupled pendulum frequencies) and were shifted less in both modes with vision than without. Variability of the equilibria, however, was ordered opposite to their degrees of shift and was unaffected by vision. Demonstrated subcritical pitchfork and tangent bifurcations conformed to the variability classification of anti- and in-phase coordination. Implications for dynamical models, hierarchical control, and definitions of coordination modes were discussed.

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David Antonio Gonzalez, Stefan Kegel, Tadao Ishikura and Tim Lee

Low-skill golfers coordinate the movements of their head and putter with an allocentric, isodirectional coupling, which is opposite to the allocentric, antidirectional coordination pattern used by experts (Lee, Ishikura, Kegel, Gonzalez, & Passmore, 2008). The present study investigated the effects of four vision conditions (full vision, no vision, target focus, and ball focus) on head-putter coupling in low-skill golfers. Performance in the absence of vision resulted in a level of high isodirectional coupling that was similar to the full vision condition. However, when instructed to focus on the target during the putt, or focus on the ball through a restricted viewing angle, low-skill golfers significantly decoupled the head—putter coordination pattern.. However, outcome measures demonstrated that target focus resulted in poorer performance compared with the other visual conditions, thereby providing overall support for use of a ball focus strategy to enhance coordination and outcome performance. Focus of attention and reduced visual tracking were hypothesized as potential reasons for the decoupling.

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M.J.M. Volman

The effect of amplitude incongruence (small circles–large circles) and form incongruence (circles–lines) on the performance of the affected and non-affected arm was examined in 12 children with hemiplegic cerebral palsy in bimanual rhythmic drawing tasks. Amplitude and form incongruence are assumed to be associated with aspects of movement execution and movement planning, respectively. The following questions were addressed: Does amplitude or form incongruence in bimanual coordination result in: (a) accommodation of the affected or non-affected arm, or both, (b) an increase of temporal variability of drawing movements of the affected or non-affected arm, and (c) a decrease of bimanual coordination stability? Form incongruence resulted in accommodation of both affected and non-affected arm in a similar way found in non-disabled participants. Despite this accommodation, the temporal variability of both affected and non-affected arm was increased, and coordination stability decreased, because the spatial trajectories of affected and non-affected arm were still rather dissimilar. Amplitude incongruence resulted in accommodation of either the affected arm (large circles required) or non-affected arm (small circles required), and in an increase or decrease of temporal variability of the affected arm, depending on the degree of spatial similarity of the trajectories of affected and non-affected arm. These findings suggest that in children with hemiplegic cerebral palsy aspects of movement execution, but not aspects of movement planning are affected by the “hemiplegic” condition.

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Travis J. Peterson and Jill L. McNitt-Gray

impulse perpendicular to the target was found to be maintained near 0, while net linear impulse parallel to the target was less toward the target as players hit swings with a driver compared with a 6-iron. This coordination strategy implies a specific role of each leg during the golf swing. The regulation

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Dawne Larkin and Helen E. Parker

This study investigated landing patterns of children aged 7–9 years with either developmental coordination disorder (DCD) or without coordination problems (NC). Initially, 16 DCD and 15 NC children were videotaped performing two-foot landings from a height of 21.5 cm onto a force platform sampling at 500 Hz. Each landing was videotaped at 60 Hz. Regression modeling of the data identified that 72% of peak maximum loading force was explained by landing time, knee angle at touchdown, and hip joint range of motion. Dis-criminant function analysis using landing force, landing time and lower limb joint kinematic variables reliably separated the groups. In the second part, 12 DCD and 10 NC children participated in 6 weekly landing lessons. The only significant adjustment produced by the program was a decrease in the range of motion at the hip in response to instructions to look straight ahead and sit into the landing.

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Sukhvinder S. Obhi, Patrick Haggard, John Taylor and Alvaro Pascual-Leone

Bimanual coordination tasks form an essential part of our behaviour. One brain region thought to be involved in bimanual coordination is the supplementary motor area (SMA). We used repetitive transcranial magnetic stimulation (rTMS) at 1 Hz for 5 min to create a temporary virtual lesion of the rostral portion of the human SMA immediately prior to performance of a goal-directed bimanual coordination task. In two control conditions, participants underwent sham stimulation or stimulation over the primary motor cortex (MI). The experimental task was to open a drawer with the left hand, catch a ball with the right hand, and reinsert the ball into the drawer through an aperture just big enough for the ball to pass through, again with the right hand. Hence, the actions of one hand depend upon the actions of the other. We calculated time intervals between the successive component actions of one hand (unimanual intervals) and actions of both hands (bimanual intervals) and analyzed these intervals separately. Interestingly, none of the unimanual intervals were affected by the rTMS, but the variability of a critical bimanual interval—the time between the left hand opening the drawer and the right hand starting to move to catch the ball—was increased by rTMS over the rostral parts of the SMA. No such effect was seen following rTMS over MI or after sham rTMS. Our results suggest that the rostral parts of the SMA play an important role in aspects of functional bimanual tasks, which involve tight temporal coordination between different motor actions of the two hands.

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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.

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Georgia D. Tsiotra, Alan M. Nevill, Andrew M. Lane and Yiannis Koutedakis

We investigated whether children with suspected Developmental Coordination Disorder (DCD+) demonstrate different physical fitness levels compared with their normal peers (DCD). Randomly recruited Greek children (n = 177) were assessed for body mass index (BMI), flexibility (SR), vertical jump (VJ), hand strength (HS), 40m dash, aerobic power, and motor proficiency. ANCOVA revealed a motor proficiency (i.e., DCD group) effect for BMI (p < .01), VJ (p < .01), and 40m speed (p < .01), with DCD+ children demonstrating lower values than DCD. Differences between DCD+ and DCD were also obtained in log-transformed HS (p < .01). These findings suggest that intervention strategies for managing DCD should also aim at physical fitness increases.

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Wei Liu, Jill Whitall and Thomas M. Kepple

Functional arm reaching involves multilinked joints: shoulder, elbow, and wrist. We propose that induced position analysis is a useful analytical tool for multijoint coordination of arm reaching. This method was used to compute the contributions of the net joint moment to the hand position when reaching forward. We describe the method and give examples of validating this model with motion capture data. The shoulder and elbow were prime movers of the arm: both acted together with an “overshoot” and “undershoot” pattern respectively to move the hand forward into the final position.

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Ronald C. Marteniuk and Christopher P. Bertram

The present paper reviews a series of prehension experiments recently conducted at Simon Fraser University's Human Motor Systems Laboratory, and attempts to place them into the larger context of multi-segmental control theory. Two related lines of experiments are reported: (a) experiments involving prehension during walking, and (b) experiments involving trunk-assisted reaching. Three-dimensional analyses of movements were performed via both world-and body-centered coordinates. Our results are supportive of the idea that both types of tasks are carried out using task-specific synergies. Furthermore, we assert that the actions of these synergies are comprised of variable contributions of different movement systems and result in smooth, world-centered end-point trajectories. We show evidence that this “motor equivalence” is the result of increasing the complexity of a given task. Finally, the implications of the present findings on prevailing motor control theory are discussed in terms of the theoretical mechanisms underlying the coordination of the transport and grasp components of prehension.