My GF has been getting a dead leg sensation and lose of power in one - usually left leg or both legs during cycling.
she has tried everything, Physio, bike fits, saddles - everything really

A Physio has suggested she may have something called Iliac arterial compression, which if treatable would involve surgery.

Has anyone one on here got any experience of this? or better stil, some non surgical treatments or sugestions?

thanks.

Long ago in a high volume ride(about 4 hours) my left leg and hip was feeling really numb like blood was not circulating well. The problem was that my saddle was a bit forward and was compressing a vein.I was on a tempo ride with my mates and we were doing 1 minute "changes" on the flats and i was sitting on the saddle a lot.I have never felt that before while clibing for example . The solution was easy, i slided back half centimeter the saddles at all my bikes and the pain was no more.Maybe your gf has a different problem,also the female body has a bit different anatomy and this wont work but check that out.Good luck!

Cheers for the info.
since posting she has had a doppler scan which showed no blood flow issues, so she has to have some more tests b4 and after exercise.
Position wise, fitted some 165mm cranks (slight raise in saddle) to open up the hip angle and possibly a 10mm shorter stem, other than that..new girl friend

Let’s hope your girlfriend doesn’t read that comment or it might be you getting replaced

My girlfriend suffered from a dead leg & numbness and saw a physio & doc about it... doppler revealed no circulation issues. Physio talked through her cycling history and they managed to pinpoint the problem started not long after she changed bikes from a woman road bike to a man's bike. Being sceptical I thought women specific gear was a load of nonsense; a sales pitch to get us to buy more stuff. However, she has since gone back to a women's road bike and her problem has improved. Maybe there is something in this different anatomy stuff.