Balance on your sit bones in a tight V and hold.
Keep your chest up and back flat, do not let your spine round to hold the shape.
The V-sit is an isometric fight to hold your body in a tight V while balanced on your sit bones. Your core has to hold the torso and legs up simultaneously without letting the spine round, which makes it a static test of the same strength V ups build dynamically. It works as a finisher, a plank alternative, or a benchmark hold to track your core progress over time.
Hold only as long as your back stays flat and your chest stays up. Several shorter quality holds beat one long collapse where your spine rounds and your legs sink.
Bend your knees to shorten the lever, or hold the position with legs lower until your core catches up. A rounded-back V-sit is just a balancing trick, not core training.
It is a different challenge. The plank resists sagging while the V-sit forces you to actively hold your legs and torso up against gravity, so the V-sit generally demands more from the front of your core.
