Survivor is one continuous piece of work with an interruption built into it. Set a timer and run high knees on the spot without stopping. Every ten seconds, jump sharply to the side in whatever direction you choose and drop straight into one plank jump-in, then get up and pick the high knees back up. Level I keeps this going for five minutes, Level II for seven, Level III for ten. There are no sets and no rest built in anywhere.
Counting to ten in your head works, but an interval timer set to ten seconds does the job better because it removes the temptation to stretch the count when your legs start complaining. The dodge is what makes this different to a straight cardio session: your body has to change direction, absorb the landing and then get down to the floor, which asks for coordination at exactly the moment you have the least of it. Then you stand back up and the running resumes, with your heart rate no lower than it was.
Keep the high knees at running pace with the arms driving, not a gentle jog on the spot. Make the dodge sharp and low, pushing off the outside foot and landing with a bent knee ready to absorb. The plank jump-in starts from the crouch: hands to the floor, jump the feet back into a plank, then jump them forward again and stand. Get your hands down early and keep the plank position honest for the moment you are in it. If the running has to slow down, let it slow rather than stop.
Ten seconds of running, one sharp change of direction, and repeat until the timer says otherwise.
Make it Harder: Add a push-up to every plank jump-in before you jump the feet back in.
Make it Easier: March the high knees rather than running them and keep the ten-second interruptions exactly as they are.
