Climb the wall in a plank and smoke your obliques.
Take the knee out to the side, not straight forward, and keep your hips from rocking.
Driving a knee out and around toward the same-side elbow while holding a plank makes the obliques do double duty, rotating the leg through while refusing to let the hips rock or sag. Every rep is a fight between the moving limb and a core trying to stay perfectly still. It slots in as core work that also opens up the hips, which is why you will see it in warm-ups and conditioning circuits alike.
Mountain climbers drive the knee straight forward for speed and conditioning. The spiderman takes the knee out and around to the elbow, which adds hip opening and forces the obliques to control rotation. Slower and wider is the point here.
Your core is letting go before the leg moves. Brace first, then drive the knee, and slow the tempo down until the hips stay level throughout.
Absolutely, it is one of the better warm-up moves going. The knee-to-elbow path opens the hips and fires the core, which covers you before squats, lunges, or any athletic session.
