Make the most of your cooldown or walk

Do you NOT look forward to "rest" days that have as an option cross-training or strength exercises because you feel guilty just resting? It's okay to rest as prescribed of course! But if you truly wish to get in some extra work that has a chance of leading to stronger running or walking and possibly a more athletic physique, you might try incorporating a few upper body exercises in your post-run or walk cool-down. A strong upper body can help propel you forward as you run and will help maintain your form when fatigue sets in.

On your route or path, find a park bench or low wall (steps can work too sometimes). Stop and perform a set of dips and push-ups on an incline. Continue your cool-down/walk on a loop that brings you back to this spot 3 times. If you're in an area or on a path in which that there are 3 stops at which you can perform these exercises, like a park, you won't need to loop around. Runners World™ has a video (see below) that shows how to perform traditional upper body exercises properly. Triceps dips are done on a chair, but you will perform them on the bench or low wall. Incline push-ups are shown as an alternate to those done on the floor. As the video instructs, if your form breaks, this is a signal to stop.
If you are new to upper body exercises, start slow, with 3-5 repetitions in each set; otherwise repeat as many as you can comfortably finish at first, doing 1 set of each exercise at each of the 3 stops. Some training programs suggest doing the most repetitions in the first set, decreasing with each following set (for example 10, 7, 5  or 20, 15, 10 to start depending on your fitness level).

If you tell yourself you cannot return home until the sets are completed, and if there are others nearby, you will be motivated to get them done and in good form. Good luck!!!

http://www.runnersworld.com/workouts/upper-body-strength-for-runners