Supposedly increase blood flow to the feet.

Red light therapy is supposed to stimulate nerve growth. I'm skeptical, but it's not expensive to find out using something from Amazon. My limited knowledge of electrical engineering makes me think that high blood sugar is "burned" up in your body and produces carbon - think marshmallow catching on fire - and carbon is a good insulator which plays havoc with electrical signals from the brain to peripheral areas. The myelin sheath around the nerves may get some damage in all that goes on.
Anyway, the TENS units may act like a wire brush to clean off the corroded battery cables from brain to toes or more likely lower back to toes.
I keep trying things and all of it seems to be helping somewhat.
I'll keep posting my progress. Today is the last day of my 12 electro-therapy and red light sessions at the "clinic."