Fillauer Myolab II, Prosthetist Manual

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7. Find the best agonist-antagonist pair of EMG control sites. Use
the “B” channel of the Myolab II to monitor the muscle (the
“B” muscle) most appropriate to control powered extension
of the elbow (and hand opening or closing). In a two-muscle
control system such as the Utah Artificial Arm, strength and
independence are important to the agonist-antagonist pair of
muscle control sites.
While viewing both Myolab II meters simultaneously, probe
for the two muscle sites with the greatest difference of EMG
amplitude (Figure 7). When the subject contracts the “A” muscle,
note the amplitude of co-contraction on the “B” channel. Then test
the reverse situation as the patient contracts the “B” muscle while
the “A” meter is monitored. Raise the gain for the weaker muscle
using the Gain Control Dial on the Myolab II so that contraction
of either “A” or “B” muscles results in about the same difference
between the two meter readings.
8. To train patients in using the unlock feature of the Utah
Artificial Arm, instruct the patient to contract both the flexor and
extensor muscles simultaneously, in a quick but low strength
co-contraction, followed by relaxation (the motion is similar to
“snapping” the fingers-very quickly but without straining for
a strong contraction). After the muscles have relaxed, the “A”
muscle is contracted gradually to move the elbow after unlocking
the prosthesis.
9. Using the Myolab II to monitor activity of the appropriate
muscles, have the subject perform the following sequence
repetitively:
Step 1- Gradually contract the “A” muscle. Maintain a
contraction for one second and then relax.
Step 2- Gradually contract the “B” muscle. Maintain a
contraction for one second and then relax.
Step 3- Quickly co-contract both the “A” and “B” muscles, then
relax both. Return to Step 1 and repeat sequence.
Once the best control sites are found, the patient may use
the Myolab II as a training device, by concentrating efforts on
developing the maximum difference between the two Myolab
II meters (Figure 7). Some patients may be aided by visualizing
movements of the phantom limb while they contract the
remnant musculature.