Crunch and side-bend against the cable while the dome keeps you honest.
Pull with your abs and obliques, not your arms, and keep the dome steady.
Lying back over the dome with a low cable in hand puts the core against real, adjustable resistance through a longer arc than the floor allows, and the routine alternates straight crunches with side-bending reps so the obliques get their own turn against the stack. The dome adds a balance tax to every rep, drift lazy and it tells on you immediately. It earns its place as weighted ab training that hits flexion and lateral flexion in one setup.
Bodyweight crunches stop challenging you after a point, the cable stack lets you load the movement and progress it like any other lift. Constant cable tension through the whole arc is the bonus you cannot get from a plate on your chest.
Treat your hands as hooks and keep the elbow angle frozen, if the handles move closer to your knees without your ribs moving toward your hips, that was an arm pull, not a crunch. Going lighter usually fixes it instantly.
Light, the dome instability plus a new movement pattern deserves a humble first session. Pick a weight you can crunch and side-bend for 12 to 15 smooth reps, then build once the balance feels routine.
