Four Minute Plank is the penultimate step in the plank series and the one that plays with asymmetry. It opens and closes with a 30-second full plank and a 30-second elbow plank, and between those bookends it puts you through 60 seconds of side elbow planks at 30 per side and 60 seconds of uneven planks - one hand down, one forearm down - again 30 seconds per side. Four continuous minutes, with the hardest work buried in the middle where your core is too busy to complain.

The uneven plank is the signature move here. With one arm extended and the other on its forearm, your shoulders sit at different heights, the load splits unevenly between your two sides, and your trunk has to resist both sagging and twisting at once. Pair that with the side elbow planks and the middle two minutes of this workout are entirely anti-rotation training - your obliques and deep core working to keep a lopsided structure level. The symmetrical planks on either end serve a purpose too: the opening pair pre-fatigues your midline so the asymmetric work bites harder, and the closing pair asks you to produce clean, level form on a spent core, which is where real stability gets built.

In the uneven plank, the temptation is to lean away from the lower arm - fight it. Press evenly through both contact points and keep your hips and shoulders level, as if balancing a tray across your upper back. Swap which arm is up at the halfway mark so both sides get equal time in each role. In the side elbow planks, keep your elbow under your shoulder, your feet stacked or staggered, and your hips lifted high throughout the entire 30 seconds - not just the first ten. In the bookend planks, hold the same straight line at minute four that you held at minute zero.

Symmetry is easy when everything matches. This workout takes the matching away and asks your core to keep you level anyway.

Make it Harder: Raise your top leg during both side elbow planks and hold it there.

Make it Easier: Split the workout in half and do the two halves at different times of the day.