This workout is a great way to mix up your cardio and core exercises. Each of the core exercises listed in this workout can be performed outside with some slight variations. Start with a run - as a far as you like - which takes you to a park, school, football field, basketball court, etc. Each of the following exercises can be performed outside with the below twists. Up the reps to 5 sets of 20 if you are up for it. After the core circuit series, record your distance to get back home.
Box Jumps: Use bleachers or a platform on a jungle gym in place of a box.
Hanging Knee Ups: Use monkey bars, a pull up bar, soccer goal, or baseball dugout overhang in place of a traditional gym pullup bar and perform the exercise by bending your knees and bringing them up and in to your chest.
Jackknifes: Find a swingset and place your feet in a swing and your arms on the ground underneath your shoulders. Pull your feet (and the swing) toward your chest.
Crunches: Perform these anywhere.
Medicine Ball Twists: Perform the exercise with no weight- or if you are really up for it, find a large rock or log to add back the weight.