I just wondered if anyone has used a TENS machine in labour & if it helped at all?

We were talking about different things for pain relief at our antenatal class on Wednesday night & I asked about it. The physio (who took the class) said that they have been used with some success.

I know it's different, but I've used a TENS for shoulder pain before & it worked really well so thought this might be an option for me. I'm not planning on having an epidural AT ALL, personal choice, it's just not an option unless absolutely necessary so I need to look at all alternative options.