Squeeze the ball between your feet and lift.
Keep your low back glued down, never let it arch as you lower.
Pinning a stability ball between your feet forces the inner thighs to squeeze continuously while the core does the actual lifting, which stops the legs from going along for a lazy ride. The ball also adds a touch of leverage and awkwardness that makes the slow lower far more demanding than a standard leg raise. It's a floor-based core builder that specifically trains the ability to keep the lower back pressed down while the legs travel, the exact skill that protects your spine under a bar.
Yes, a bit. The ball adds light resistance, keeps constant tension through the squeeze, and stops you separating your legs to make the movement easier. It's a natural progression once floor leg raises feel comfortable.
It's peeling off the floor as your legs lower, which shifts the load into your spine. Only lower the ball as far as you can keep your low back glued down, even if that's halfway at first. The range grows as your core gets stronger.
A standard 55 to 65 cm ball works for most people. Bigger balls are slightly easier to grip between the feet, smaller ones demand more squeeze, either way the mechanics stay the same.
