Experiment Protocol:

IDENTIFICATION OF STRTETCH REFLEX CONTRIBUTIONS TO
JOINT STIFFNESS IN NORMAL AND SPASTIC HUMANS

 

Purpose:

The objective of this study is:

·  1.Carrying out a test_retest study to find intrasubject reliability of the dynamic stiffness model of the ankle joint. The experiment is repeated at two different time for each normal subject.

·  2. Finding the intrinsic and reflex contributions to pathological muscle tone. The experiment is performed on spastic patients.

Description:

  1. A custom-fit fibre-glass boot is used to securely attach the subject's foot to the actuator in the experimental apparatus described in the consent form.
  2. Range of Motion. The ankle is rotated passively from a neutral position towards maximum dorsiflexion and then towards maximum plantarflexion. Displacement in each direction is continued until the subject could tolerate no further movement, i.e. the onset of pain, or until motion of the knee or lower leg is observed.
  3. Maximum Voluntary Contraction (MVC). Subjects are required to generate both dorsiflexing and plantarflexing maximum voluntary contractions in response to changes in a tracking stimulus displayed on an oscilloscope. The experiment is run at the operating point (position) at which good reflex torques can be generated.

A pseudorandom binary sequences (PRBS) is used as position input to the ankle joint.

  1. Displacement Amplitude. The PRBS amplitude is started at 0.01 rad and increased by 0.005 rad for each trial up to a maximum amplitude that can be endured by the subject.
  2. Displacement Frequency. The PRBS switching interval is started at 75 ms (corresponding to maximum frequency) and increased by 25 ms for each trial up to 200 ms (corresponding to minimum frequency.)
  3. Position Variation. The experiment is started at the first position in which reflex torques can be generated. The appropriate amplitude is selected based on the production of the largest reflex torque. This amplitude is maintained during this part of the experiment.
  4. Level of Contraction. Subjects are asked to generate ankle torques from 50% plantarflexing MVC to 0, decreasing by 10% PF MVC for each trial. Subjects should match the feedback torque line with the target signal, both of which are displayed on the oscilloscope. The appropriate amplitude nad position are selected based on the production of the largest reflex torque and the endurance of the subject. This amplitude and position are kept constant during this part of experiment.
  5. A part of the experiment, described in 5 to 7, is run for each subject.
  6. Usually, the experiment will last for less than 120 minutes including a 30 - 40 min preparation period.
  7. Subject may ask for a rest or withdraw from the experiment at any time.

Notes:

  1. Suggestions and volunteers are welcomed!
  2. Mehdi Mirbagheri is responsible for modifying and arranging this experiment.

Last modified by Mehdi on March 21,95

 

Last modified: Thu Feb 27 12:18:41 1997