I'm a single parent whose kid receives virtually no contact from the other parent, so instead I rely of the help of family and friends to survive. I work really odd hours (4ish-midnight, but I tend to stay an extra hour or two), so I do not get to spend as much time with my kiddo as I would like. Health and fitness are really important to me so I try to incorporate it into daily life when at all possible.
My son really likes going to the park and the community we live in has a nature trail that is at least 2 miles long that passes through the park so whenever we go, we almost always go on foot--either that or ride our bikes! Since I adopted a lovely anatolian shephard mix dog about 4 months ago, I try to give her some attention to so she always comes along.
Lately the kiddo has gotten into this habit of turning everything into a race. I've managed to curb it by reinforcing that not everything is a race (and that it's not nice to call people losers when we secretly let him win). This has also created a positive effect of him wanting to go running with me, but between his growing 5-year-old body and my 100lb dog this is not an easy task.
My son and I usually do a combination of walking/jogging the 3 miles from our house, around the trail, stop at the park halfway through the trail, and make our way back home. I'll admit we've been working on this since we moved into our house 2 years ago.
1. Add an incentive that will entice your child's interest to follow through
My son loves going to the park. He also didn't object to exploring the nature trail in our neighborhood, but it was a lot of activity for his 3-year-old body when we initially started. The pros of this was it exhausted him pretty quickly and he took a nap easy when we got home; the cons of this was it exhausted him pretty quickly and I typically had to carry him at some point to make it back home.