Here they write 10%
It’s not for lab testing but i think make sense too.
I’m currently training for Alpine climbing and am taking an AeT test in the lab on Thursday. Last year I did it on a flat treadmill and afterwards I read that I should have done it on an incline. Any recommendations on how steep the treadmill should be? I did a forum search and didn’t see anything (possibly missed it). Any advice is greatly appreciated thanks!