Interval Timer 40 seconds of work with 15 seconds off between movements. Work for 4 total rounds: Example: Leg Matrix for 40 seconds, rest for 15, Plank Walk Ups for 40 seconds, rest for 15, High Knees for 40 seconds, rest for 15, Walk Out to Jump for 40 seconds, rest for 15, back to Leg Matrix for 40….for 4 total rounds.