EMG sensor to sense muscle atonia

I'm trying to detect when a person is in REM. For part of this detection, I want to detect muscle atonia. Atonia is when the muscle has no strength. This happens in REM.

When I participated in Northwestern's lucid dream research, they used an electrode on my chin to detect atonia. They could tell the difference between my muscle not moving and atonia. You can be awake and not move your muscle. But you won't have atonia unless you're asleep (or paralyzed).

I found this sensor: myoware. But I want to know if it will be sensitive enough to detect atonia vs the muscle not moving.

I'm not sure how to figure out the answer. Is there some standard way to measure sensitivity in sensors? Is there something I could look up to know how sensitive a sensor has to be to pick up atonia?

Also Northwestern used one electrode (I believe called monopolar montage) but this sensor I found has two electrodes (bipolar montage). Does anyone know what the purpose of having a bipolar montage vs a monopolar montage?

OK, so please quote a reference for the different patterns for "atonia" versus relaxation.

If the system is detecting individual action potentials, then it is sufficiently sensitive.

All sensor systems have a reference point; you require two connections for an electrical circuit. Presumably the distinction made is between "monopolar" where the reference electrode is some distance from the muscle electrode and "bipolar" where there are two muscle electrodes in modest proximity. In the latter case which has superior noise rejection, you generally still have a distant electrode as the "guard" so that the voltage on the muscle electrodes stays within the working range of the amplifier.

EMG systems can use high pass filtering, certainly much higher than for an ECG.