Assessment of function of Gastrocnemius and Soleus during walking in able bodied adults and selective electrical stimulation of the 2 muscles.

Anatomically gasrocnemius and soleus are grouped together and called triceps
surae. However they consist of 2 distinct muscles, one of which is bi-articular
and the other is mono-articular. The fibre composition of the 2 is also
different. Gastrocnemius has predominantly fast twitch fibres where as soleus
consists predominantly of slow twitch fibres. Functionally these 2 muscles
could be very different. Descriptions found in the literature concerning
function of these 2 muscles state that they function similar to one another.
However, due to close proximity, the surface electrodes placed on gastrocnemius
during gait studies are bound to show cross talk from soleus. The function of
these two muscles could only be differentiated using both, surface and fine
wire electrodes simultaneously.
For some years electrical stimulation of the calf muscles has been considered
as a possible solution for the lack of acceleration during gait in subjects who
have had stroke. However, the attempts to improve their gait have been
unsatisfactory. This may be due to the anatomical and functional differences or
may be due to meer closeness. Generally, implantable electrodes are the most
ideal method for stimulation of muscles in isolation however in many cases they
are not as practical as surface electrodes. The first step in this direction
would be to determine if we can effectively stimulate these underlying muscles
selectively using surface electrodes.

The objective of the study is primarily to study functions of gastrocnemius and
soleus during gait individually. Secondly, to determine to what degree
stimulation of the gastrocnemius and soleus can be achieved, in isolation or in
combination, using surface stimulating electrodes.

Fundamental theory forming observational study.
The use of 3-D measurement system such as VICON and simultaneous use of surface
and fine-wire EMG will help define the exact functions of the two muscles in
kinematic and kinetic terms. The use of surface and fine wire electrodes will
also enable us to explore the extent of cross talk during natural action of the
muscles in question and that during neuromuscular electrical stimulation
After placement EMG electrodes selectivity of the insertion site will be tested
by asking the subject to perform muscle specific movements. Markers will be
placed. The subject will be asked to walk at different walking speeds during
data collection.
For the stimulation part of the study: The muscles will be stimulated using
surface electrodes. Four different stimulation electrode placement
configurations will be examined. Stimulation parameters: biphasic pulses with
pulse duration 350µs, frequency 20 pps, 35 pps & 45 pps. EMG will be recorded
from all electrodes during stimulation
After the data collection the electrodes will be removed.

Besides a little discomfort at the time of insertion of fine wire electrodes it
is expected that the subjects will experience no further pain or discomfort. In
general, there will be no health risks involved in participating in the
project. On rare occasions the tip of the fine wire electrode breaks and is
left behind in the muscle, however, due to inert properties of the metal and
being sterile it causes very little problems.