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ABSTRACT: The authors sought to determine if principles of the Leading Joint Hypothesis, when applied to a multijoint, bimanual coordination task, could provide insight into the contribution of intralimb dynamics to interlimb coordination. Participants repetitively traced ellipse templates with an isodirectional motion of the end effectors (both hands moving counterclockwise [CCW]) at two cycling frequencies. Ellipse templates were oriented either tilted right or tilted left, yielding a total of 4 left arm-right arm leading-joint combinations. Analysis of torque sign and impulse data indicated that the 4 ellipse-tracing conditions resulted in 4 distinct left arm-right arm leading-joint combinations: 2 conditions with similar leading joints and 2 conditions with different leading joints. Isodirectional CCW ellipse tracing was more stable when produced with similar leading joints compared with when produced with different leading joints. The authors discuss results within the context of intralimb control contributions to the stability of interlimb coordination patterns.
Journal of Motor Behavior 12/2009; 42(1):49-60. · 1.64 Impact Factor
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ABSTRACT: The authors compared the force and time endpoint accuracy of goal-directed ipsilateral upper and lower limb isometric contractions and determined the components of motor performance that can be transferred from 1 limb to the other after practice. Ten young adults (27.4 +/- 4.4 years) performed 100 trials that involved their matching peak force to a force-time target with ankle dorsiflexor and elbow flexor muscles. The peak force error and variability was greater for ankle dorsiflexor contractions than for elbow flexor contractions, whereas the timing error and variability did not significantly vary with limb. There was transfer of timing, but not force, of motor output between upper and lower limbs. The timing error of the elbow flexor contractions decreased by 23% when those contractions were preceded by ankle dorsiflexor contractions, and the timing error of the ankle dorsiflexors decreased by 24% when those contractions were preceded by elbow flexor contractions. These finding therefore suggest that timing of an aiming isometric contraction may be organized at a common part of the brain for the upper and lower limbs.
Journal of Motor Behavior 06/2008; 40(3):186-9. · 1.64 Impact Factor
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ABSTRACT: Research has shown that movement impairments following stroke are typically associated with the limb contralateral to the side of the stroke. Prior studies identified ipsilateral motor declines across a variety of tasks.
Two experiments were conducted to better understand the ipsilateral contributions to organization and execution of proximal upper extremity multisegment aiming movements in persons with right-hemispheric stroke.
Participants performed reciprocal aiming (Experiment 1) and 2-segment aiming movements (Experiment 2) on a digitizing tablet. In both experiments, target size and/or target orientation were manipulated to examine the influence of accuracy constraints on the planning and organization of movements.
Kinematic measures, submovement analysis, and harmonicity measures were included in this study. Declines in organization and execution of multisegment movements were found to contribute to performance decrements and slowing in stroke patients. Furthermore, stroke patients were unable to efficiently plan multisegment movements as one functional unit, resulting in discrete movements.
Results suggest the importance of considering ipsilateral contributions to the control and organization of targeted aiming movements as well as implications for rehabilitation and recovery.
Neurorehabilitation and neural repair 21(5):388-97. · 4.49 Impact Factor
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Tiffany M. Rodriguez
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ABSTRACT: A number of movements produced in everyday life require not only coordination of joints within a limb, but also coordination between one or more limbs. The aim of this dissertation was to examine the influence of biomechanical constraints on intralimb coordination, interlimb coordination, and learning. Experiment 1 sought to determine if principles of the Leading Joint Hypothesis, when applied to a multijoint bimanual coordination task, could provide insight into the contribution of intralimb dynamics to interlimb coordination. Participants repetitively traced ellipse templates in an asymmetrical coordination pattern (i.e. both limbs moving counter-clockwise). Kinematic data of the upper limbs were recorded with a VICON camera system. Ellipse templates were oriented either tilted right or tilted left; yielding a total of four left arm-right arm leading joint combinations. The findings indicated that stability of interlimb coordination patterns were found to be influenced by whether arm movements were produced with similar or different leading joints. Bimanual asymmetric ellipse-tracing produced with similar leading joints were more stable than patterns produced with different leading joints. For example, asymmetric coordination patterns produced with similar leading joints exhibited less transient behavior than coordination patterns produced with different leading joints (p < .01). Experiment 2 expanded on these findings by employing a similar task and incorporating a learning component to assess how intralimb dynamics are tuned with practice of a novel coordination pattern. Participants were randomly assigned to one of three groups. One group practiced tracing a pair of ellipse templates that were oriented in such a way that required similar leading joints while the other two groups practiced tracing ellipse templates that required different leading joints. Early in practice, the group learning the coordination pattern with similar leading joints exhibited greater interlimb stability than the two groups learning with different leading joints. However, following two days of practice, performance of the groups learning with different leading joints improved to match that of the group learning with similar leading joints. The findings suggest that initial biomechanical constraints can be overcome with practice, resulting in similar performance regardless of whether being produced with similar or different leading joints.
