My 9 year old DD1 can't do the monkey bars and never has been able to. She's not a particularly active child, never has been one to run everywhere like DD2, but she does do 3 hours of dancing classes a week which I encourage as it's the only time she's really active.
I feel the main problem with her lack of activity is school - the playground is a small square of tarmac (or in the summer this plus an area of grass) with absolutely nothing on it - I feel she's justified in finding playtimes boring, I think she and her friends just sit around, there isn't anything to do, and as there are so many children in a small space running around isn't particularly encouraged.
She's been wearing a pedometer for the last few days (DH is doing some fitness drive at work so she's been joining in) and I was horrified at how few steps she does during the school day (which, for a 9 year old, is most of the day). She only got over 10,000 once. We do our best with walking, but we live opposite school and quite a distance from anything else, so walking's not always practical. I would welcome daily PE at school - it seems to be the first thing dropped if anything else is to be done. Last week I questioned the fact that her PE T-shirt was clearly unworn and she told me she had to miss PE to finish a piece of work - I'd actually rather she did the PE!