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Experimental setup.
The experimental chair and the location of the 6-DOF load cell (JR3) are
shown, as well as the force platforms under the chair,the footrest and the VICON reflective markers on the
subject.
The seat height and seat depth of the chair are adjustable. Under the seat, a 6-DOF load
cell (JR3 Inc., Woodland, CA) was mounted to measure the forces and moments when the subject
performed all tasks. Force Platforms A force platform (www.amtiweb.com) was placed under the 4 legs
of the chair . Forces in anterior, right, and inferior directions and the moments around these axes
were recorded. Another such force platform was placed under the footrest. The locations of the chair and
footrest were fixed on the upper surface of the force platforms.
Motion Capturing System A ViconPeak motion capturing system (8 Camera MCam2, Vicon Peak,
Centennial, CO) was used to record the movement of the trunk, head, and upper limb of the seated
individual . Reflective markers were placed on the subject based on the standard placement of the
VICON Plug-In-Gait (PIG) model.
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Static sitting trial.
These tasks were designed for assessing the subject’s ability to maintain an
unsupported upright sitting posture . Trials were tested with and without the footrest. In static
sitting, the subject is asked to sit still in the chair for 1-minute. Three conditions were tested, "Eyes Open",
"Eyes Closed" and "Target Staring" (staring at a target which is 150cm away in the front at the eye level).
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COP sway during static sitting.
Representative data are from 1 healthy control and one
stroke patient.
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Dynamic sitting trials.
Dynamic sitting tasks test the subject’s ability to move efficiently his/her center of mass in a voluntary
reaching attempt and the ability to flex the trunk in forward and lateral directions, which are directly
related to the balance and trunk control impairment. Trials were tested with and without the footrest. For
forward reaching, the subject reaches out forward towards a distant target as much as possible with both
arms stretched out (Fig.A). For lateral reaching (both to the left and to the right), the subject was asked
to reach towards a distant target (Fig. B&C) Task efficiency (TE) was determined by calculating moment
coupling from the moment data recorded using the 6-DOF load cell underneath the seat. It is the ratio of
the squared value of the task moment (Mtask ) to the squared value of the magnitude of the resultant
moment (SMi) during an active task. It measures how much of the effort is dedicated to the task, i.e. the
efficiency. Since each of the designed tasks is a movement in a specific body anatomical plane, the
moment recorded during the task should be expected in the corresponding plane with only small amount of
coupled moment in other planes.
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COP area and displacement in static sitting.
Data are given for "Target staring" condition in
this plot
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Task efficiency (%) in dynamic reaching tasks in seated individuals.
--In all reaching tasks, the healthy controls achieved almost 100% of task efficiency and always were
higher than that of stroke individuals.
--When the footrest was not used, this difference was significant only when the stroke individuals reached
to their Non-Affected side.
--When the footrest was not used, the individuals with stroke showed significantly lower task efficiency in
all 3 reaching directions.
Note: Kinematics of preliminary data are not reported
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Lateral Trunk Performance Apparatus
In order to correlate trunk performance findings with
previously validated clinical tests, such as the Trunk Impairment Scale* (TIS), an apparatus has been
constructed to help normalize and quantify lateral trunk performance. Using this device, the
subject will be asked to touch his/her elbow to the surface that has an XSensor (www.xsensor.com)
pressure pad attached to it . The Kinematics (Vicon), Kinetics (JR3 and Force Platform), as well as
the coordinates of where the subject was able to make contact with the surface (XSensor) will be analyzed
to better understand the subject’s ability, or lack thereof, to properly extend and flex opposite sides of
trunk.
The apparatus seen here will be used for subjects to
touch his/her elbow to each surface on each side of the seat. The pressure sensing sheets on each surface
record the location of contact.
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Upper Trunk Co-ordination trials.
Trunk co-ordination tasks are designed to assess the subject’s ability to
axially rotate his/her trunk in both left and right directions. It consists of 2 parts, upper and lower trunk.
For upper trunk, the subject is asked to rotate his/her upper trunk in the transverse plane to bring forward
each of his/her shoulders in turn at a comfortable speed. For lower trunk, the subject is asked to
rotate his/her lower trunk and pelvis in the transverse plane to bring forward each of his/her knees in turn at a comfortable speed. Each of the trials last for 1 minute.
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Implementation of portable backrest.
Due to discomfort that may arise during extended
periods of (A) unsupported seating, a (B) portable backrest was designed to quickly be (C) implemented in
between trials to provide temporary support for subject.
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