A strong stay comes in very handy. You can leave your dog in one place and go off and do other activities. In the case of the partner gym workout, it has been helpful to have my dog wait while I do some things and then I call him to me and we do his exercises. But how do you get a strong stay?
When I start teaching the stay to my dogs, I usually start with breakfast and very short duration. I hold the dog and give my command. Then I give a release word. The dog is released immediately when the release word is given and helps themselves to breakfast. We follow this pattern until the dog is staying with my gently holding for about 5 seconds. I then start fading out the holding. I now have a dog that will stay for 5 seconds in a non distracting environment. I gradually build up the time I am asking for the stay. I like teaching the stay in association with breakfast. If the dog breaks the stay, I simply tell the dog that wasn't correct, and lift up the food bowl. A little while later we will try it again. Food motivated dogs tend to learn pretty quickly to stay to ensure they get their breakfast promptly. In addition to duration, once I'm fairly confident in the dog, I start walking away and
gradually start moving out of sight, but within hearing range in addition to adding some distractions. Once I have a reliable dog at home, I start taking it on the road. Dogs tend to be location learners. Just because I have a 5 minutes out of sight down stay at home, doesn't mean I'll have the same behavior at the park. I need to lower my expectations. I might start with a one minute stay with me in sight. If the dog does well, I will gradually make it more complex. When we are practicing I will often walk back to the dog, let them know they are being good and reward randomly while they are in the stay. By practicing a lot, rewarding when the dog is doing what I asked, changing duration, distractions and locations, I gradually build a very solid stay.