[RiverFlash]

I have two Jacks. My older Jack, River, has been through obedience, was top of her class, is so wonderful and well behaved in a million ways. She is such a fabulous dog but she has this one really weird habit that I have tried to break in another million ways. We go walking twice a day. In the morning, I take them up a trail in the National Forest (right behind our house) for about an hour. On this walk, and only this walk, she runs up ahead, then comes whizzing back and 'bites' my foot. She doesn't bite hard, but she grabs my foot with her mouth and I nearly trip every single time! On her leash, she does not do this, but I like walking her off leash as she gets 100x more exercise and can run around freely. I have tried all sorts of things to avert her from attacking my foot. I have said no, made her sit, put her on the leash, grabbed her tail (when I can catch her ... she's so amazingly fast), thrown a ball to distract her ... I can't even remember some of the stuff I've tried. She just HAS to grab my foot, and I almost fall down each time. Our puppy doesn't do this, but I'm worried he'll learn from her because she teaches him EVERYTHING. Anyway, does anyone have any ideas to stop this? She eventually, after the first 15 minutes, stops, but it is really kind of annoying. She only does it to me, too. She doesn't do it to anyone else walking her (though she's super bonded to me and will sulk whenever I'm not around). Help! I know she's trying to play, but I really dislike the game (she's the masked dog in my avatar).