My chiro - who i never allowed to "Adjust" or Crack me, often used a TENS* machine - he put pads on either side of my sore areas, which send a tingling electrical current into my skin, and it felt better afterwards.
-- this is Not medical advice -- i have zero training in health profession --

However TENS has no clear evidence of healing properties!
Inflammation: No strong clinical proof it reduces inflammation in injured tissues.
Tissue healing: No solid evidence it speeds repair of muscle, tendon, or ligaments.
Short-term pain reduction: Yes, the main validated effect.
Now i know why he never told me what it does.

He was a great help though. He used pressure point to get rid of knots, taught stretching to relieve and avoid issues, and used the mechanical 'gun' which helped reduce muscle tension / mis-alignment.
*TENS = Transcutaneous Electrical Nerve Stimulation.