What the plank is and what the plank is not.
The is often misunderstood.
Today you see people setting world records for holding a plank for 10 hours or more--while that is a fine feat... it goes against the true purpose of the plank.
The purpose of the plank--specifically the Hardstyle Plank is to generate maximum tension within about 10-15 seconds.
Why?
Because any lift you do (specifically the deadlift, squat and press) will take no longer than 10 seconds to complete. During the swing similar breathing mechanics apply. You'll be holding the top position of the swing for less than a second.
"Strength is a skill"
And possessing the skillset to "zip up" your muscles from the ground up (over and over) and brace at the top... protects your back. And transfers the energy/power from your hips & midsection into the kettlebell.
This skill practice allows you to tap into "Hebb's Law."
Hebb's Law: Neurons that "fire together wire together." Meaning... when groups of nerve cells (or brain regions) are repeatedly activated at the same time (i.e., contracting specific muscle groups during the Hardstyle Plank), they form a circuit and are essentially "locked in" together. Making easier to active the right muscles at the right time to keep you safe and boost your performance.
Generating tension like this on demand is a skill. Maintaining the tension and being comfortable with the uncomfortable, is what the Hardstyle Plank is all about.