just cruising the news and found an article from cnn on hwo tens units don't really work.https://www.cnn.com/2009/health/12/30/back.pain.tens.nerve.stimulation/
i have a unit. i have to admit i just don't use it. i've tried but the hassle outweighs the benefits for me.
it did seem to take the pain level down a notch though. maybe it's just that it feels good compared to just straight pain. the ultrasound unit at the pt places always felt much better than the little tens unit.