Experimental Protocol

An Investigation of the Effect of the Soleus Muscle Fatigue on Ankle Stretch-Reflex Dynamics

Purpose:

Reflex mechanisms are known to modulate the contraction of associated muscles through neuromuscular connections. While the magnitude of the reflex at a given time varies with the instantaneous muscle length, it may also vary with the fatigue state of the muscle. This experiment is designed to study the effect imposed muscle fatigue on the stretch-reflex dynamics.

Description of Testing Protocol:

1. A custom-fitt 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.
4. Pulse trials (6, 9, 15 pulses respectively) will be applied while the subjects contract their triceps surae at 5%, 60%, and then 5% of their MVC.
5. At each pulse onset, the subject's foot will be subjected to a 40 ms pulse with amplitudes of 0.03-0.06 radians, and sampling will be performed for an interval of 200 ms, thereafter.
6. Electromyographic signals (EMGs) from the tibialis anterior and gastrocnemius-soleus muscle groups and ankle position and torque signals will be measured throughout the testing session.
7. Usually, for a trained subject, the testing phase of the experiment will last for less than 30 minutes in addition to a 30 minute preparation period.
8. The subject may ask for a break or withdraw from the experiment at any time.

Experimental Timeline:

• Week 1: orientation & construction of custom made fibre-glass boot
• Week 2: control test #1
• Week 3: control test #2 & initiation of experimentation #1
• Week 4: Experimentation #2
• Week 5: Experimentation #3
• Week 6: Experimentation #4

Six subjects will be scheduled to run starting approximately from the end of May to the end of June of 1999.

Notes:

1. Suggestions and volunteers are welcome.
2. This experiment is being conducted by Sam Qita.

last modified on May 23, 1999