Roll a loaded bar out and pull it back with pure core strength.
Keep your hips tucked and back flat, never let your low back sag at full reach.
As the bar rolls away, your body becomes a long lever that gravity is trying to fold in half backwards, and the abs work overtime to stop that extension happening. Unlike crunches, the hardest tension arrives with the abs at full stretch in the extended position, which is exactly where they grow best. It belongs in your programme as the heavy compound of core training rather than another high-rep filler.
It is more stable and lets you set your grip wider, which makes it easier to learn and to control at long range. The wheel allows more freedom of path once you are strong. Either way the abs do the same anti-extension job.
Your hips are sagging and your spine is taking the load instead of your abs. Tuck the pelvis, squeeze the glutes, and shorten the rollout to a range where your back stays flat. Earn distance gradually.
As far as you can go with hips tucked and back flat, then pull back. For most people that is short of full extension for a while. A rep cut short with position beats a full stretch with a sagging spine.
