Fillauer Myolab II, Prosthetist Manual

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Mark the location of the strongest EMG signal, and the total area
in which a strong EMG is found.
4. Instruct the patient to “contract-hold-relax” in about a three
second sequence. A smooth and even contraction is desired,
without strenuous effort, with relaxation after each contraction.
Instruct the patient to try to relax the muscles not being tested.
Systematically move the preamplifier by one-half inch increments
and ask the patient to perform the “contract-hold-relax” sequence
with the same strength of contraction for at least two repetitions
at each location.
5. When a potential control site is identified, mark the best
electrode location on the skin, and also mark the total area in
which an adequate EMG signal is obtained (Figure 7). This will be
important in locating electrodes in the prosthetic socket. Identify
all potential EMG control sites in this manner.
6. When probing EMG control sites for the Utah Artificial Arm, use
the “A” channel of the Myolab II to monitor the muscle (the “A”
muscle) most appropriate to control flexion of the elbow of the
prosthesis (usually an anterior muscle such as the biceps or
pectoralis). This muscle is usually recommended for the hand
closing site also, although exceptions are common, (e.g., when the
elbow extension muscle is more easily controlled by the subject).
Figure 6
For example, relax the shoulder when contracting the biceps.
Also, the EMG signal will usually be more controllable if some
resistance is provided to the motion of the remnant limb, either
with the clinician’s hand or the socket of a prosthesis.
3. Palpate the muscle as the patient contracts it and place the
preamplifier over the belly of the muscle. Touching the muscle
helps give the subject more sensation of the muscle contraction,
which may help in learning to control the muscle (Figure 6).