I did our local Pants in the Park 5k race last Sunday, in aid of prostate cancer.
I wore my running shorts and singlet underneath, but don't think I'll be making a habit of running in my aikido kit! Once I'd registered, I did a couple of laps of the track as my warm up, and found my hakama eventually got a bit bunched up and then muddy because of its length.
They gave out prizes at the end for best pants, and I got a special mention along with a man wearing a very fetching Borat green mankini! Seems his outfit had the opposite problem to mine, as he said he suffered from frequent wedgies all the way round.