I'm also a climber, I've been climbing about 20 hours a week lately, and using a cheap electric current device, I was getting measurements between 6% and 12%, and I have very lean muscle.

I have some friends who are physical trainers, and they were talking about low body fat once, saying it's very difficult to to get down to around 5% and lower than 4% is dangerous.

According to a random body building website thread, 3% is essential body fat... http://forum.bodybuilding.com/showthread.php?t=143851451&...