A Paradoxical Experiment

A Paradoxical Experiment

Postby rfrye » Wed Mar 30, 2011 10:55 pm

Try this experiment:

1) Place your pads in one of the standard arrangements that use all 4 channels to stimulate the quads.
I am thinking two small pads at the heads of particular muscles and either a double pad or two wide single pads at the base of the muscles near the top of the leg. This could be like diagram 20 or 21 of the Compex Electrode Placement Guide, or it could be like the first photo in Jason Keister's 7/13/2010 blog entry

2) Connect the leads in the standard arrangement; i.e. 4 negative (black) terminals to the pads at the top of the leg and 4 positive (red) terminals to the pads at the heads of the muscles.

3) Start some program such as Warm Up or Strength or Active Recovery and set the intensities so that you get a familiar strong response that you can see and feel. For now, the intensities should be the same on all leads. Remember the intensity settings and how your muscles look and feel.

4) Pause the program. Switch the positive leads on one leg with the negative leads on the other leg. Now all of the positive leads are connected to pads on one leg, and all of the negative leads are connected to pads on the other leg.

5) Continue the program. You may have to readjust the intensities to the settings you had in step 3. Compare how your muscles look and feel now. Try switching back and forth to make sure.

Can you detect any difference in the stimulus you get with the two arrangements? To me they seem exactly the same, and I feel the same long term training effect from either arrangement.

The accepted theory is that the square waves on the positive and negative leads are in opposite phase so that when they are connected in the standard arrangement they have a double effect on the action potential of the motor nerves. The standard arrangement should give a strong response, while the arrangement with a single polarity on each side of the body should give little or no response. If the two arrangements produce the same response, something else must be going on.

The practical application of not needing to connect pads to each end of a muscle group is that you can use each pad only where you want a contraction. This is particularly useful on the simpler muscle groups in the calves or the arms. A disadvantage is that if you have an imbalance, you can't vary the intensity between each side of your body.

Less pads per muscle group -- more muscle groups per session :!:

-Roger Frye
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Re: A Paradoxical Experiment

Postby jbruskewitz » Thu Mar 31, 2011 6:12 pm


I'm the first to admit that I am a biologist and not an electrical engineer. I may be following a thread with some incorrect assumptions, but here is what has occurred to me after reading the account of your experiment.

What seems to be different in the two polarity settings you tried is the length of the circuits. The longer the length, the more resistance. It sounds like you compensated by turning up the current. I wonder if the penetration into the muscle tissue is as deep as it is when the tow poles of each circuit are closer to one another?

One of the reasons that E-stim is able to stimulate more motor units, a motor neuron and the muscle fibers that it innervates, is that it can bypass the GABA that attaches itself to the motor neuron cell membrane. It can stimulate the neuron on either side of the GABA. The GABA shunts the signal away from following through the length of the neuron to the neuromuscular junctions. If the signal doesn't pass through the neuromuscular junctions, then the muscle fibers on the other side will not contract.

The degree to which the current penetrates the tissue is directly correlated to the number of motor units that are stimulated. The desired adaptations will come from the continued stimulation of these motor units.

I leave it to you to determine whether the alternate polar set up you mention will penetrate the tissue as effectively if the circuit is longer. Granted, the Compex packs enough of a wallop that the increased resistance with this polarity set up is possibly negated.

Pardon the logic if I've made incorrect assumptions regarding circuit length and resistance.

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Re: A Paradoxical Experiment

Postby rfrye » Fri Apr 01, 2011 11:09 am

Thanks for your response. You may recall that you and I discussed this idea last summer by email. You were understandably skeptical, because the idea that a single lead is enough to stimulate a muscle runs counter to the standard approach of stimulating the motor neuron on both ends.

No, I am not compensating for a longer circuit by turning up the current. I am using the same intensity settings for both arrangements.

I don't think there is a current flowing between the positive leads on one leg and the negative leads on the other leg. You can increase the distance as far as the body permits and still get the same effect. For example, you could stimulate the calves instead of the upper leg. If there were a current, it would run through the upper legs, and they would be stimulated, but instead the stimulus remains localized to the area of the pads.

-Roger Frye
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Joined: Wed Mar 23, 2011 4:17 pm

Re: A Paradoxical Experiment

Postby jason-keister » Wed Apr 06, 2011 12:17 pm

Hi Roger,

In posing your experiment to the engineers at Compex, they indicated that the body is completing the circuit by the current flowing through the entire body to the opposite leg where the opposite leads are connected. They recommended against doing this as you're using your entire body to complete the circuit rather than just the muscle group you're targeting. Let me know if you have any additional questions regarding this, but I do not recommend continuing this experiment.



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