Gait Analysis: Dynamic Electromyography

Nancy and Kristin are putting the 'Robot Suit' on Jo. This will tell the
CGMA staff when Jo’s muscles are working.

After the therapist has observed and videotaped your child walking, they usually move on to collect data on how your child’s muscles are working while walking. To do this, we use dynamic electromyography (D-EMG), which is the only method available to determine the timing of muscle use during movement.

We have found that it is easiest to explain this part of the analysis to patients by telling them that this is the part of the test where they get to put on the "robot suit." Many patients find this to be an interesting exercise where they get to perform some more for the cameras, only this time they get to dress up.

What to Expect

Your therapist will have your child put on a small vest over their clothes. They then attach surface electrodes to their skin, typically placed on the thigh muscles, hamstrings, the shin and the calf muscle, or any other muscles whose activity is questioned by the referring physician. These electrodes are then wired up to the vest in order to record all muscle activity.

Your child will be asked to walk or perform other activities while the activity of each individual muscle (timing and magnitude) is recorded. We can record when the muscles are on and when they are off. It cannot tell us how strong the muscles are. Muscle activity can be recorded from up to 16 muscles at a time.

Now Jo can walk and tell the CGMA staff how
her muscles work together.

It is important to know that the surface electrodes attached to your child’s skin are like stickers. They do not bother most patients and can be easily removed after the test with little trouble. Some patients, however, are more sensitive and find that the electrodes can be a little irritating. Be sure to prepare your child that these stickers will be removed when they are done, but it should only feel like a sticker or small bandage is being removed. Our staff is specially trained to make sure this is done as easily and quickly as possible.

Dynamic Electromyography with Fine-Wire Electrodes

On occasion, CGMA will need more information than the basic D-EMG test can provide. The activation pattern of muscles might be too deep (under other muscles) or too small so that it is difficult to detect using surface electrodes. In that case, your therapist might use a different type of electrode from the surface electrode, called a fine-wire electrode. This technique provides valuable information about the cause of movement problems especially in patients with specific types of foot abnormalities.

Fine-wire electrodes are tiny wires that are inserted through the skin directly into the muscles that need to be looked at more closely. While this is an invasive technique that may be briefly painful during needle insertion, most children find it only mildly irritating, with little after affects. Fine-wire electromyography is only used if specifically ordered or if it is determined at the time of the analysis that the muscle in question cannot be assessed accurately using surface electrode. This is not part of a typical visit to CGMA, but we want you to be aware of this possible procedure.

Step 4: 3D Motion Analysis and Stride Characteristics