Meet in the middle and fold like a jackknife.
Lift both ends at once and meet in the middle. Don't let your feet crash down.
Folding your torso and legs up simultaneously makes the core contract from both ends at once, shortening it through the biggest range a floor exercise can offer. The reach for your toes at the peak demands full-body coordination and a strong finish to the contraction, while the slow return to a stretched-out position keeps tension on during the lower. It earns its place as the high-range sit-up variation, one step up in difficulty and payoff from crunches and standard sit-ups.
You are lifting both halves of your body, not just the torso, and starting from full stretch with arms overhead gives the core its longest lever. There is also no anchored-feet leverage to cheat with, so the midsection does everything.
No, reach as close as your range allows. Bending the knees slightly or aiming for your shins keeps the movement productive while you build the strength and flexibility. The simultaneous fold matters far more than the fingertip contact.
You are letting both ends crash down instead of lowering under control. Descend slowly and stop just before your heels and shoulders fully settle, keeping light tension. If the arch persists, shorten the range or bend the knees a touch.
