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Vladimir Ivkovic and Max J. Kurz

This study investigated the nature of the structural variations found in the motor output of individuals with Parkinson’s disease (PD). Young (n = 21; 19.9 ± 1.3 yrs.), aged (n = 9; 74.8 ± 6.8 yrs.) and individuals with PD (n = 9; 73.4 ± 6.6 yrs.) swung their leg at a pendular frequency and frequencies that were 20% faster and slower. This study had three key findings. First, individuals with PD have greater variability in the leg swing angular kinematics and swing times. These variations appear to be related to the 0–15 Hz band of the of angular displacement power spectrum. Second, changes in the structural variations appear to not be derived from a stochastic source. Third, the magnitude of the variations and the structure of the variations are influenced by the frequency that the leg is swung. These results are consistent with the viewpoint that changes in the magnitude of the variations and the regularity of the structural variations are dependent upon health and adaptability to the task dynamics.

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Max J. Kurz, Joan E. Deffeyes, David J. Arpin, Gregory M. Karst and Wayne A. Stuberg

The purpose of this investigation was to evaluate the effect of a lower body positive pressure support system on the joint kinematics and activity of the lower extremity antigravity musculature of adults and children during walking. Adults (age = 25 ± 4 years) and children (age = 13 ± 2 years) walked at a preferred speed and a speed that was based on the Froude number, while 0–80% of their body weight was supported. Electrogoniometers were used to monitor knee and ankle joint kinematics. Surface electromyography was used to quantify the magnitude of the vastus lateralis and gastrocnemius muscle activity. There were three key findings: (1) The lower extremity joint angles and activity of the lower extremity antigravity muscles of children did not differ from those of adults. (2) The magnitude of the changes in the lower extremity joint motion and antigravity muscle activity was dependent upon an interaction between body weight support and walking speed. (3) Lower body positive pressure support resulted in reduced activation of the antigravity musculature, and reduced range of motion of the knee and ankle joints.

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Amy K. Hegarty, Max J. Kurz, Wayne Stuberg and Anne K. Silverman

The goal of this pilot study was to characterize the effects of gait training on the capacity of muscles to produce body accelerations and relate these changes to mobility improvements seen in children with cerebral palsy (CP). Five children (14 years ± 3 y; GMFCS I-II) with spastic diplegic CP participated in a 6-week gait training program. Changes in 10-m fast-as-possible walking speed and 6-minute walking endurance were used to assess changes in mobility. In addition, musculoskeletal modeling was used to determine the potential of lower-limb muscles to accelerate the body’s center of mass vertically and forward during stance. The mobility changes after the training were mixed, with some children demonstrating vast improvements, while others appeared to be minimal. However, the musculoskeletal results revealed unique responses for each child. The most common changes occurred in the capacity for the hip and knee extensors to produce body support and the hip flexors to produce body propulsion. These results cannot yet be generalized to the broad population of children with CP, but demonstrate that therapy protocols may be enhanced by modeling analyses. The pilot study results provide motivation for gait training emphasizing upright leg posture, mediolateral balance, and ankle push-off.

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Swati M. Surkar, Rashelle M. Hoffman, Brenda Davies, Regina Harbourne and Max J. Kurz

There is mounting experimental evidence that suggests children with hemiplegic cerebral palsy (HCP) lack the ability to properly plan their motor actions. The purpose of this investigation was to determine how these planning deficits might affect the ability of children with HCP to execute a complex sequence of actions that have different final end states in the hand/arm position. Thirteen children with HCP (age = 6.8 ± 2.9 yrs, Manual Ability Classification levels = II–IV) and 15 typically developing (TD) children (age = 5.8 ± 1.1 yrs) completed a sequential motor task that involved reaching to grasp an object and place it into six-different target positions. Each target had a biomechanically different final hand/arm position for placing the object. A three-dimensional motion capture system was used to calculate the resultant spatiotemporal kinematics of a marker that was placed on the hand. In addition, video analysis was used to quantify the child’s reaction time, end-state comfort effect, and task failures. Compared with the TD children, the children with HCP had notable deviations in their spatiotemporal kinematics when reaching for the object and placing it in the respective target positions. The children with HCP also exhibited slower reaction time, reduced end-state comfort, and increased number of task failures when placing the objects in the respective target potions. Interestingly, the children with HCP showed impaired planning on the affected as well as the less affected arm. This suggests that the inability of children with HCP to properly plan a motor action might partly arise from central deficits in their cognitive processing, and not exclusively from the peripheral deficits seen in the musculoskeletal system. Altogether our results imply that children with HCP lack the ability to plan and execute sequential motor actions.