To start, kneel down and bend one leg up so your dog can crawl under it. Lure them under with one piece of food and then toss a second piece a bit further so they go all the way through and stand up. Show them another piece and lure them the other direction and repeat! If they don't want to go all the way through at first, just be patient and give lots of rewards for each attempt at going under further and further. Some dogs aren't comfortable with crawling under your leg like that.
I have her do about 10 repetitions back and forth and then walk around a minute and then another 10 or so.
If you have bare floors like we do I think it's nice to use a rug or a dog bed for your dog to crawl on so it's not so hard on their elbows.
I feel it strengthens her hind leg muscles.
A video:
Happy Fit dog Friday!