Start in a forearm plank with your elbows under your shoulders and your body in a straight line from head to heels. Keeping that line rigid, push through your forearms to shift your whole body backward, pivoting on your toes, then pull yourself forward again to the start. The range is small - a hand's length each way is plenty - but the further back you shift, the harder your abs have to fight to keep your hips from sagging.

Works: abs, obliques, lower back, shoulders

Breathing: Exhale as you push back, inhale as you return - slow and deliberate, matching the saw's rhythm.

Common Mistakes: Letting the hips sag toward the floor at the back of the movement, piking the hips up to make it easier, and reaching for a big range before you can hold a straight line through a small one.

Make Easier: Shorten the range right down to a few centimeters each way, or build your base with Slow Climbers first.

Make Harder: Extend the range gradually and slow every rep down, or move on to Alt Arm / Leg Raises or Up & Down Planks.