The overall goal of this procedure is to assess neuromuscular function using percutaneous electrical nerve stimulation. This is accomplished by first connecting surface electrodes to the desired muscle. The second step is to install the subject on the ergometer.
Next, the motor nerve is electrically stimulated using a handheld ball electrode or a self-adhesive electrode. The final step is to record electromyographic activity of the muscle. Ultimately, percutaneous electrical nerve stimulation is used to assess neuromuscular function at the spinal, spinal and peripheral level.
The main advantage of this technique is that he has a good reliability and electrical and mechanical response are easy to obtain. This method can help answer key questions in the field of normal muscular physiology, such as evaluation of normal muscularity following training or rehabilitation program. To begin clean the skin where the electrodes will be placed by shaving off the hair and scrubbing the exposed skin with alcohol.
This is required for a low impedance connection. Next, ask the participant to stand tiptoe to clearly identify the plantar flexor muscles. Place two 10 millimeters silver chloride surface electrodes about two centimeters apart on the prominent bulge of the medial gastroc emus muscle for the lateral gastroc emus.
Place two electrodes at one third of the distance from the head of the fibula to the heel for the soleus muscle. Place two electrodes at two thirds of the way between the medial condyles of the femur and the medial maus for the tibials anterior muscle. Ask the participant to stand tiptoe to identify it.
Then place two electrodes at one third of the distance between the tip of the fibula and the tip of the medial maus. Next place a reference electrode in a central position on the same leg between stimulation and recording sites. Now adjust the participant's chair so that the ankle and knee are bent at 90 degrees so that the soleus and gastroc knee, my muscles are not stretched, and so the H reflex is not altered.
Now firmly strap the ankle to the ergometer such that the anatomical axis of the joint, which is the external mos, is aligned with ergometer axis of rotation. Next, ask the participant to exert pressure on a foot plate and record the plantar flexor torque. Then connect the electrodes to the amplifier and place the anode for electrical stimulation over the patellar tendon.
Now, try to feel the posterior tibial nerve through the skin in the popal Fosse. Then determine the best stimulation site of the posterior tibial nerve. Use a handheld cathode ball electrode on the popal fossa to find the site with the largest age reflex at that location.
Attach the self-adhesive silver chloride cathode. None of this parameter should change for the assessment of the different electrosurgical measurements. Only the intensity of the stimulation and the condition should vary.
Before starting the test, instruct the participant to relax and keep their muscles at rest. Then set the stimulation intensity to obtain a maximal soli age reflex amplitude, which usually ranges from 20 to 50 milliamps. Using one millisecond pulses record at least three sous H reflex responses.
Pause at least three seconds between stimulations to avoid post activation depression. Next, increase the intensity to between 40 and 100 milliamps to get the maximal sous M wave amplitude. Once determined, increase the intensity by 20 to 50%and deliver three super maximal stimulations.
Record the twitch torques associated with these stimulations for the voluntary contraction test. Begin with a warmup. Ask the participant to perform 10 brief non fatiguing sub maximal contractions of the plantar flexor muscles.
Ask that they wait a few seconds between each contraction during the warmup and throughout the test record the tricep Siri EMG activity. Next, instruct the participant to perform an exothermic maximal voluntary contraction of the plantar flexors. The participant must push as hard as possible against the ergometer by contracting his plantar flexor muscles.
Give visual feedback during the effort with standardized verbal encouragement, the maximal voluntary contraction is reached. When a plateau is observed at the plateau, delivered a paired stimulation at 100 hertz frequency at super maximal intensity of the maximal voluntary contraction. Immediately after the contraction, deliver another paired stimulation when the muscle is fully relaxed.
To evaluate the voluntary activation level using software such as acknowledge 4.1, select a time window, including the EMG response associated with the twitch at rest, select the H wave or the M wave measure the peak tope amplitude, the peak to peak duration, and the area of the waves. Then select the resting twitch and measure its peak torque. Next, calculate the ratio between the peak torque and the sum of the amplitudes of the soleus and gastroc nemi M waves.
To quantify the electromechanical efficiency, this ratio reflects the efficiency of the excitation contraction coupling. Next, measure the maximal peak torque of the maximal voluntary contraction from the baseline of the torque at rest to the maximal value of the maximal voluntary contraction, exclude the superimposed torque induced by the doublet stimulation. Then measure the superimposed torque induced by the doublet stimulation.
Measure from the voluntary torque value at the onset of the stimulation to the peak of the evoked response. Lastly, measure the peak torque associated with a potentiated doublet. Use these values to calculate the voluntary activation level.
Using the described methods, h and m waves were investigated at rest. The H reflex reaches a maximum value before being totally absent from the EMG signal, whereas M waves progressively increase until reaching a plateau at maximal intensity. After watching this video, you should have a good understanding of how to assess neuromuscular function using percutaneous electrical nerve stimulation.
Once mastered, localizing the stimulation site and finding the optimal intensity can be done in 10 minutes if it's performed properly Following this procedure. Other techniques like transcranial magnetic stimulation can be performed in order to answer additional questions like changes in corticospinal excitability following training or rehabilitation program.
