X Marks the Spot is a cardio workout that keeps moving and keeps changing. High knees open each round, getting your legs working and your heart rate climbing fast. Then the jacks take over - but not the same jack three times. Jumping jacks, twist jacks and split jacks each move your body differently, training coordination, trunk rotation and lateral power in turn. Two jump squats finish each round with a burst of explosive leg strength before the whole thing starts again.

The high knees are your home base - you return to them three times, and each time they feel a little different as fatigue builds. The three jack variations keep your brain as busy as your legs, because your body has to remember what comes next while it is already breathing hard. The jump squats are small in number but big in effort - just two reps, but they ask for everything you have left in that moment.

X marks the spot - and once you find it, you'll want to come back.