Compex Intensity vs mA

by **rfrye** » Fri Mar 25, 2011 10:29 am

How does one convert the intensity numbers on the new Compex (0 - 999) to milliamps (0 - 120)? The relationship isn't linear. I have been using the quadratic approximations:
mA = 3.8 * sqrt(intensity)
intensity = (mA)^2 / 14.4
-Roger Frye

by **jason-keister** » Fri Mar 25, 2011 10:37 am

Hi Roger,

I haven't been able to obtain a comparison chart from Compex as of yet, so I don't have a hard and fast rule for this. I have been told it varies form muscle group to muscle group. I am working on putting something together though, so I will certainly keep everyone in the loop as soon as I have more info.

Regards,

Jason

by **rfrye** » Sat Mar 26, 2011 12:42 pm

I would have hoped that the software would be designed to cleanly assign each feature to one aspect of the waveform. Naive, I guess.

I was thinking:
intensity buttons control amplitude;
levels control length of stress and recovery and total times;
program type controls frequency and general training/rest pattern;
body segment controls waveform details like rise time of the square wave.

Oh well, the idea is pretty. Perhaps not practical.

-Roger Frye

by **jason-keister** » Mon Mar 28, 2011 2:40 pm

Hi Roger,

What you just detailed is correct. The frequency also increases with the level though. I just don't have a direct comparison chart between mA's and the Energy Levels that the Compex units use. I will certainly keep you posted as I obtain this info.

Regards,

Jason

by **jbruskewitz** » Tue Mar 29, 2011 9:46 am

Roger,

There is a range of frequencies used for each of the strength programs. Strength: 75 HZ Level 1 to 100 Hz Level 5. Resistance: 50 H Level 1 to 70 Hz Level 5. Endurance: 10 Hz Level 1 to 18 Hz Level 5. The total time a contraction is held doesn’t effectively vary for the Endurance or Strength programs However for the Resistance program, the total time a contraction is held through the length of the program increase by 50% as the levels progress from 1 to 5.

Which body part you select determines the amplitude of the signal delivered.

AMPLITUDE is the pulse duration value. It is measured in microseconds [1 µsec = one millionth of a second] and it is usually set at the chronaxia value of the main nerve, which allows the muscle innervation to be activated.
CHRONAXIA is the needed time for stimulating the tissue by using an intensity double the intensity at the rheobase, the minimum current value to trigger an excitation no matter how long the duration of the stimulus.

Because of these differences in the strength programs from levels 1 through 5, it is best to spend time first at Level 1 and gradually work through the levels over a 6 to 8 week period to enjoy the full benefits.

Jim

by **rfrye** » Tue Mar 29, 2011 10:59 am

Jim,
Thanks for the details about AMPLITUDE and CHRONAXIA and how the frequency changes with level. Very interesting.

In electrical engineering, the amplitude of a square wave is how far it goes off the x-axis, and the period is how long it takes to go through a full cycle. From your description, it sounds like NMES refers to half the period as the AMPLITUDE.

Jason,
Thanks for trying to find the intensity vs mA tables.

-RogerF

by **jason-keister** » Fri Apr 08, 2011 12:42 pm

Hi Roger,

You can now find a condensed conversion chart on our website. Here's the link:

http://www.hammernutrition.com/download ... -Chart.pdf

Hope this is helpful, let me know if you have any additional questions.

Regards,

Jason