A plank with jumping-jack legs to keep your core firing under movement.
Keep your hips level and still, only your legs should move.
The plank jack bolts jumping-jack legs onto a high plank, so while your feet snap out and in, your core's job is to hold your hips dead level against every landing. It sneaks conditioning into core work, the legs push your heart rate up while your trunk grinds away isometrically. A staple for circuits when you want your abs and lungs taxed at the same time.
Both. The jumping legs raise your heart rate while your trunk holds an isometric brace, which is exactly why they show up in circuits and finishers.
Brace harder before the feet move and jump the feet slightly narrower until the hips stay silent. The plank is the exercise, the jack is just the disturbance.
Step one foot out and in at a time instead of jumping both. Same core challenge, no impact, and you can build back up to the jump.
