Over & Under is a cardio workout with a spike built into it. Blocks of twenty high knees and twenty climbers keep your heart rate elevated, while single jump knee-tucks - one maximal rep, three times per set - punch it higher. In between, five up and down planks grind your arms and core. The name is the structure: sustained work over, explosive and floor work under.

The single-rep knee-tucks are the clever part. One all-out jump demands total power production - hips, quads and calves firing at maximum - and because it appears when you are already breathing hard, it trains your body to explode from fatigue rather than from rest. That is a quality most steady-pace cardio never develops. The up and down planks in the middle serve a different purpose: transitioning from forearms to palms and back again, one arm at a time, they load the triceps and shoulders while your core fights the rotation each transition creates.

Drive for genuine height on the knee-tuck - pull both knees toward your chest and land soft with bent knees, ready to move. Keep the high knees at hip height and stay on the balls of your feet. During up and down planks, keep your feet wide and your hips as still as possible; the less you wobble, the more your core is doing.

One jump. It sounds generous until it arrives. Make it count every time.

Make it Harder: Turn every single jump knee-tuck into three.

Make it Easier: Swap the jump knee-tucks for bodyweight squats performed at speed.