Here are some sites I awhile ago, they seemed to have good info about the various electrical stimulation type of machines , how they work, and what conditions they might help.

the first link explains the varous types - TENS, IF, EMS, etc.

Electro therapy TENS/EMS/IF stimulator info
http://www.vitality-web.com/backstor...Stimulator.htm
http://www.medi-stim.com/overview.htm
http://www.rehabpub.com/features/82004/3.asp
http://www.spine-health.com/topics/c...ctro/el01.html
http://www.skylarkdevice.com/web-site/ele_thera.htm
http://www.bmls.com/electrodes/epc.php
http://rehabilicare.com/protocol.html